2022/08/11 更新

写真a

クロダ カズユキ
黒田 一幸
所属
理工学術院
職名
名誉教授

学位

  • 早稲田大学   工学博士

所属学協会

  •  
     
     

    American Chemical Society

  •  
     
     

    日本粘土学会

  •  
     
     

    日本セラミックス協会

  •  
     
     

    日本化学会

 

研究分野

  • 無機物質、無機材料化学

研究キーワード

  • 層状・層間化合物、無機固体化学、無機物質化学、無機合成化学

論文

  • Preparation of Siloxane‐based Microporous Crystal from Hydrogen Bonded Molecular Crystal of Cage Siloxane

    Naoto Sato, Yoshiyuki Kuroda, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry – A European Journal   in press  2018年11月  [査読有り]

  • Effect of Intercalated Amide Molecules on Interlayer Condensation of Layered Silicate RUB-15

    Masakazu Koike, Yusuke Asakura, Yoshiyuki Kuroda, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Clay Science   22   1 - 11  2018年06月  [査読有り]

  • Formation of Single-Digit Nanometer Scale Silica Nanoparticles by Evaporation-Induced Self-Assembly

    Shigeru Sakamoto, Masashi Yoshikawa, Kota Ozawa, Yoshiyuki Kuroda, Atsushi Shimojima, Kazuyuki Kuroda

    Langmuir   34 ( 4 ) 1711 - 1717  2018年01月  [査読有り]

     概要を見る

    There are emerging demands for single-digit nanoscale particles in multidisciplinary fields, such as nanomedicine, optics, catalysis, and sensors, to create new functional materials. Here, we report a novel route to prepare silica nanoparticles less than 3 nm in size via the evaporation-induced self-assembly of silicate species and quaternary trialkylmethylammonium surfactants, which usually form reverse micelles. The solvent evaporation induces a local concentration increase and simultaneous polycondensation of silicate species within the hydrophilic region of the surfactant mesophases. Extremely small silica nanoparticles in the silica-surfactant mesostructures can be stably dispersed in organic solvents by destroying the mesostructure, which is in clear contrast to the preparation of silica nanoparticles using the conventional reverse micelle method. The surface chemical modification of the formed silica nanoparticles is easily performed by trimethylsilylation. The particle size is adjustable by changing the ratio of the surfactants to the silica source because the hydrophobic/hydrophilic ratio determines the curvature and diameter of the resulting spherical silica-surfactant domains in the mesostructure. The versatility of this method is demonstrated by the fabrication of very small titania nanoparticles. These findings will increase the designability of oxide nanoparticles at the single-digit nanoscale because conventional methods based on the generation and growth of nuclei in a solution cannot produce such nanoparticles with highly regulated sizes.

    DOI

  • Formation of Concentric Silica Nanogrooves Guided by the Curved Surface of Silica Particles

    Shintaro Hara, Keiya Hirota, Yuka Tabe, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Langmuir   34 ( 4 ) 1733 - 1741  2018年01月  [査読有り]

     概要を見る

    The flexible control of nanopatterns by a bottom-up process at the nanometer scale is essential for nanofabrication with a finer pitch. We have previously reported that for the fabrication of linear nanopatterns with sub-5 nm periodicity on Si substrates the outermost surfaces of assembled micelles facing the substrates can be replicated with soluble silicate species generated from the Si substrates under basic conditions. In this study, concentrically arranged nanogrooves with a sub-5 nm periodicity were prepared on Si substrates by replicating the outermost surfaces of bent micelles guided by silica particles. The Si substrates, where silica particles and surfactants films were deposited, were exposed to an NH3-water vapor mixture. During the vapor treatment, cylindrical micelles became arranged in concentric patterns centered on the silica particles, and their outermost surfaces facing the substrates were replicated by soluble silicate species on the Si substrates. The thinness of the surfactant film on the substrate is crucial for the formation of concentric silica nanogrooves because the out-of-plane orientations of the micelles are suppressed at the interface. Surprisingly, the domains of the concentric silica nanogrooves spread to much larger areas than the maximum cross-sectional areas of the particles, and the size of the domains increased linearly with the radii of the particles. The extension of concentric nanogrooves is discussed on the basis of the orientational elastic energies of the micelles around one silica particle. This study of the formation of bent nanogrooves guided by the outlines of readily deposited nanoscale objects provides a new nanostructure-guiding process.

    DOI

  • Transformation of Mesostructured Silica Nanoparticles into Colloidal Hollow Nanoparticles in the Presence of a Bridged-Organosiloxane Shell

    Eisuke Yamamoto, Saki Uchida, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda

    Chemistry of Materials   30 ( 2 ) 540 - 548  2018年01月  [査読有り]

     概要を見る

    Hollow siloxane-based nanoparticles (HSNs) have attracted significant attention because of their unique properties and applications. Recently, it was discovered that the simple covering of silica nanoparticles with an organosiloxane shell leads to the spontaneous formation of HSNs
    however, the detailed mechanism of their formation has not yet been established. In this study, colloidal 30 nm HSNs were prepared by adding organically bridged alkoxysilane to an aqueous dispersion of mesostructured silica-surfactant composite nanoparticles, and the temporal changes of the morphology and chemical state of the nanoparticles were monitored to elucidate the formation mechanism. Core silica was dissolved after the formation of the core-shell structured nanoparticles, and almost all the dissolved silicate species were incorporated in the organosiloxane shell, changing the shell thickness. Two conditions were essential for silica dissolution induced by covering with organosiloxane: (i) presence of a sufficient amount of uncondensed Si-OH groups in the organosiloxane shell, and (ii) elevated temperature and pH for the promotion of the hydrolysis of silica. These findings will enable the fabrication of various HSNs through organosiloxane-induced silica dissolution and redeposition.

    DOI

  • Precise size control of layered double hydroxide nanoparticles through reconstruction using tripodal ligands

    Yoshiyuki Kuroda, Yuya Oka, Tadao Yasuda, Tatsuyuki Koichi, Keisuke Muramatsu, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Dalton Transactions   47   12884 - 12892  2018年01月  [査読有り]

     概要を見る

    © 2018 The Royal Society of Chemistry. Precise size control of layered double hydroxide nanoparticles (LDHNPs) is crucial for their applications in anion exchange, catalysis, and drug delivery systems. Here, we report the synthesis of LDHNPs through a reconstruction method, using tripodal ligands (e.g., tris(hydroxymethyl)aminomethane; THAM). We found that the mechanism of reconstruction at least includes a dissolution-recrystallization process rather than topotactic transformation. THAM is immobilized on the surface of recrystallized LDHNPs with tridentate linkages, suppressing their crystal growth especially in lateral directions. The particle size of the LDHNPs is precisely controlled by the concentration of THAM regardless of the synthetic routes, such as coprecipitation and reconstruction. It is suggested that the particle size is controlled on the basis of Ostwald ripening which is governed by the equilibrium of the surface modification reaction.

    DOI

  • Polymerization of cyclododecasiloxanes with Si-H and Si-OEt side groups by the piers-Rubinsztajn reaction

    Masashi Yoshikawa, Hiroya Shiba, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Bulletin of the Chemical Society of Japan   91 ( 5 ) 747 - 753  2018年  [査読有り]

     概要を見る

    Two types of cyclododecasiloxanes possessing SiH and SiOEt side groups were polymerized by the Piers-Rubinsztajn (P-R) reaction. Cyclododecasiloxane possessing both methyl and ethoxydimethylsilyl side groups (Cyclo12-Me-Si- Me2(OEt)) was synthesized by ethoxylation of cyclododecasiloxane possessing both methyl and dimethylsilyl side groups (Cyclo12-Me-SiHMe2). Cyclo12-Me-SiMe2(OEt) and Cyclo12-Me-SiHMe2 were polymerized by the P-R reaction, using B(C6F5)3 as a catalyst. The original cyclic structures were retained after the reaction without cleavage of the SiOSi bonds. Dimethylsilane elimination between two side SiHMe2 groups and the consecutive siloxane-bond formation occurred concomitantly during the main P-R reaction. The effectiveness of the P-R reaction between oligosiloxanes toward preparation of polyorganosiloxanes with well-defined architectures has been demonstrated.

    DOI

  • In situ synthesis of magnesium hydroxides modified with tripodal ligands in an organic medium

    Keisuke Muramatsu, Yoshiyuki Kuroda, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Dalton Transactions   47 ( 9 ) 3074 - 3083  2018年  [査読有り]

     概要を見る

    Layered magnesium hydroxides modified organically with tris(hydroxymethyl)aminomethane (Tris-NH2) were directly synthesized from magnesium chloride dissolved in a polar organic solvent, like dimethyl sulfoxide (DMSO), containing a small amount of water. Tris-NH2 acted as a base for precipitating magnesium hydroxides as well as an organic modifier. In contrast to the case of an aqueous solution, the use of organic solvents substantially increased the degree of modification of layered magnesium hydroxides with Tris-NH2 owing to the formation of bidentate Mg-O-C linkages by Tris-NH2 in addition to its tridentate bonding mode. Bidentate linkages, hydrolyzed readily in water, are stable in the organic media. Pentaerythritol (Tris-CH2OH), trimethylolethane (Tris-CH3), and trimethylolpropane (Tris-C2H5) were also successfully used for the synthesis of organically-modified layered magnesium hydroxides by the addition of tetrabutylammonium hydroxide as a base with DMSO as the solvent. The synthesis of hybrid magnesium hydroxides in organic solvents is expected to expand the chemistry of organically modified layered metal hydroxides with various metallic species and a wide variety of organic functional groups.

    DOI

  • Formation of silica-organic hybrid nanoparticles by cross-linking of ultra-small silica nanoparticles

    Shigeru Sakamoto, Koki Fujino, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry Letters   47   1018 - 1021  2018年01月  [査読有り]

     概要を見る

    © 2018 The Chemical Society of Japan. A new type of silicaorganic hybrid nanoparticle (HNPs) ~30nm in size, consisting of vinylsilylated silica nanoparticles (SNPs) of size ~2nm and 1,6-hexanedithiol as the organic linker, were prepared by their interconnection via the thiolene reaction. The particle size of the HNPs varied depending on the concentration of the linker. Additionally, they could be dispersed in organic solvents and further successful chemical modification of the internal surfaces of HNPs indicated the accessibility of guest species into the internal nanospaces.

    DOI

  • Self-assembly of cyclohexasiloxanes possessing alkoxysilyl groups and long alkyl chains

    Masashi Yoshikawa, Hanako Ikawa, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry Letters   47   1203 - 1206  2018年01月  [査読有り]

     概要を見る

    © 2018 The Chemical Society of Japan. Cyclohexasiloxanes with long alkyl chains and triethoxy-silyl groups were synthesized by alkoxysilylation of organo-metallasiloxanes containing cyclohexasiloxanes. Lamellar mesostructured siloxane-based materials were formed by self-assembly of these cyclosiloxane compounds through hydrolysis and polycondensation. This molecular design will lead to the creation of siloxane-based materials with cavities that can be used for inclusion and separation of guest species.

    DOI

  • Protecting and Leaving Functions of Trimethylsilyl Groups in Trimethylsilylated Silicates for the Synthesis of Alkoxysiloxane Oligomers

    Masashi Yoshikawa, Yasuhiro Tamura, Ryutaro Wakabayashi, Misa Tamai, Atsushi Shimojima, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   56 ( 45 ) 13990 - 13994  2017年11月  [査読有り]

     概要を見る

    The concept of protecting groups and leaving groups in organic synthesis was applied to the synthesis of siloxane-based molecules. Alkoxy-functionalized siloxane oligomers composed of SiO4, RSiO3, or R2SiO2 units were chosen as targets (R: functional groups, such as Me and Ph). Herein we describe a novel synthesis of alkoxysiloxane oligomers based on the substitution reaction of trimethylsilyl (TMS) groups with alkoxysilyl groups. Oligosiloxanes possessing TMS groups were reacted with alkoxychlorosilane in the presence of BiCl3 as a catalyst. TMS groups were substituted with alkoxysilyl groups, leading to the synthesis of alkoxysiloxane oligomers. Siloxane oligomers composed of RSiO3 and R2SiO2 units were synthesized more efficiently than those composed of SiO4 units, suggesting that the steric hindrance around the TMS groups of the oligosiloxanes makes a difference in the degree of substitution. This reaction uses TMS groups as both protecting and leaving groups for SiOH/SiO- groups.

    DOI

  • Spontaneous Crack Healing in Nanostructured Silica-Based Thin Films

    Shun Itoh, Satoshi Kodama, Maho Kobayashi, Shintaro Hara, Hiroaki Wada, Kazuyuki Kuroda, Atsushi Shimojima

    ACS NANO   11 ( 10 ) 10289 - 10294  2017年10月  [査読有り]

     概要を見る

    Self-healing materials that can spontaneously repair damage under mild conditions are desirable in many applications. Significant progress has recently been made in the design of polymer materials capable of healing cracks at the molecular scale using reversible bonds; however, such a self-healing mechanism has rarely been applied to rigid inorganic materials. Here, we demonstrate the self-healing ability of lamellar silica-based thin films formed by self assembly of silica precursors and quaternary ammonium type surfactants. Specifically, spontaneous healing of cracks (typically less than 1.5 mu m in width) was achieved under humid conditions even at room temperature. The randomly oriented lamellar structure with thin silica layers is suggested to play an essential role in crack closure and the reformation of siloxane networks on the fracture surface. These findings will lead to the creation of smart self-healing silica-based materials based on reversible siloxane bonds.

    DOI

  • Nanospace-Mediated Self-Organization of Nanoparticles in Flexible Porous Polymer Templates

    Yoshiyuki Kuroda, Itaru Muto, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda

    LANGMUIR   33 ( 36 ) 9137 - 9143  2017年09月  [査読有り]

     概要を見る

    Self-organization is a fundamental process for the construction of complex hierarchically ordered nanostructures, which are widespread in biological systems. However, precise control of size, shape, and surface properties is required for self-organization of nanoparticles. Here, we demonstrate a novel self-organization phenomenon mediated by flexible nanospaces in templates. Inorganic nanoparticles (e.g., silica, zirconia, and titania) are deposited in porous polymer thin films with randomly distributed pores on the surface, leaving a partially filled nanospace in each pore. Heating at temperatures beyond the glass transition temperature of the template leads to self-organization of the inorganic nanoparticles into one-dimensional chainlike networks. The self-organization is mediated by the deformation and fusion of the residual nanospaces, and it can be rationally controlled by sequential heat treatments. These results show that a nanospace, defined by the nonexistence of matter, interacts indirectly with matter and can be used as a component of self-organization systems.

    DOI

  • Topotactic conversion of layered silicate RUB-15 to silica sodalite through interlayer condensation in N-methylformamide

    Masakazu Koike, Yusuke Asakura, Megumi Sugihara, Yoshiyuki Kuroda, Hidehiro Tsuzura, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    DALTON TRANSACTIONS   46 ( 31 ) 10232 - 10239  2017年08月  [査読有り]

     概要を見る

    Silica sodalite was obtained using topotactic conversion of layered silicate RUB-15 through stepwise processes that consisted of the control of stacking sequence of the layers, interlayer condensation by refluxing, and elimination of intercalated guest species. The interlayer condensation of RUB-15, in which acetic acid was pre-intercalated between the layers to control the stacking sequence, afforded a sodalite framework containing organic guest species by refluxing in N-methylformamide (NMF). The pre-intercalated acetic acid molecules were largely replaced with NMF. This formation process of silica sodalite containing large amounts of intercalated organic guest species is in clear contrast to the previously reported process that used direct calcination of an intercalation compound of layered RUB-15 accommodating acetic acid between the layers. Calcination of the condensed product provided sodalite with fewer defects than the directly calcined product, thus indicating the advantage of the stepwise process. The method reported here is useful for the preparation of pure silica sodalite with relatively low defects and plate-like morphology.

    DOI

  • Role of Cubic Siloxane Cages in Mesostructure Formation and Photoisomerization of Azobenzene-Siloxane Hybrid

    Sufang Guo, Jun Sasaki, Shiho Tsujiuchi, Shintaro Hara, Hiroaki Wada, Kazuyuki Kuroda, Atsushi Shimojima

    CHEMISTRY LETTERS   46 ( 8 ) 1237 - 1239  2017年08月  [査読有り]

     概要を見る

    A mesostructured siloxane-based hybrid film is formed by the self-assembly of cubic, double-four-ring (D4R) siloxanes mono-functionalized with azobenzene. The azobenzene groups in the film exhibit reversible and a high degree of trans-cis isomerization upon UV-vis irradiation. The bulky D4R cages play an important role in both the formation of cylindrical assemblies and the improvement of the photoisomerization behavior as compared with conventional azobenzene-siloxane hybrid materials.

    DOI

  • Synthesis of a Single-Crystalline Macroporous Layered Silicate from a Macroporous UTL-Type Zeolite and Its Accelerated Intercalation

    Yusuke Asakura, Naoki Kawaura, Yoshiyuki Kuroda, Masakazu Koike, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    CHEMISTRY-A EUROPEAN JOURNAL   23 ( 46 ) 11022 - 11029  2017年08月  [査読有り]

     概要を見る

    A single-crystalline macroporous layered silicate was obtained for the first time. Firstly, UTL-type zeolite with macropores was prepared hydrothermally under the presence of acetylene black as a macropore template and the subsequent calcination to remove the template. Double four-membered ring (d4r) units in the UTL framework were selectively dissolved to yield a layered silicate with macropores. Intercalation of tetrabutylammonium ions into the macroporous layered silicate is accelerated if compared with that into the same silicate without macropores, indicating the effectiveness of macropores due to easy diffusion. The layered silicate with macropores was converted into PCR-type zeolite with macropores, a hierarchically micro- and macroporous material, through interlayer condensation.

    DOI

  • Preparation of Mesoporous Basic Oxides through Assembly of Monodispersed Mg–Al Layered Double Hydroxide Nanoparticles

    Yuya Oka, Yoshiyuki Kuroda, Takamichi Matsuno, Keigo Kamata, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry - A European Journal   23 ( 39 ) 9362 - 9368  2017年07月  [査読有り]

     概要を見る

    © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Mesoporous basic Mg–Al mixed metal oxides (MMOs) with a high surface area and large pore size have been prepared through the assembly of monodispersed layered double hydroxide nanoparticles (LDHNPs) with block copolymer templates. The particle sizes of the LDHNPs were mainly controlled by varying the concentration of tris(hydroxymethyl)aminomethane (THAM), which was used as a surface stabilizing agent. LDHNPs and micelles of a block copolymer (Pluronic F127) were assembled to form a composite. The composites were calcined to transform them into mesoporous MMOs and to remove the templates. The Brunauer–Emmett–Teller surface areas, mesopore sizes, and pore volumes increased as a result of using the templates. Moreover, the pore sizes of the mesoporous MMOs could be controlled by using LDHNPs of different sizes. The mesoporous MMOs prepared from the LDHNPs showed much higher catalytic activity than a conventional MMO catalyst for the Knövenagel condensation of ethyl cyanoacetate with benzaldehyde. The mesoporous MMO catalyst prepared using the smallest LDHNPs, about 12 nm in size, showed the highest activity. Therefore, the use of monodispersed LDHNPs and templates is effective for preparing highly active mesoporous solid base catalysts.

    DOI

  • Pore Clogging of Colloidal Mesoporous Silica Nanoparticles for Encapsulating Guest Species

    Eisuke Yamamoto, Kouya Nagata, Kenta Onishi, Chihiro Urata, Atsushi Shimojima, Hiroaki Wada, Shinji Takeoka, Kazuyuki Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   90 ( 6 ) 706 - 708  2017年06月  [査読有り]

     概要を見る

    Colloidal mesoporous silica nanoparticles (CMS) are useful as carriers for imaging probes because of their unique features. A simple method for the pore clogging of CMS has been proved by the addition of tetraethoxysilane under weakly basic conditions. The pore clogging of CMS is useful for encapsulation of thermoresponsive dyes.

    DOI

  • Thickness control of 3-dimensional mesoporous silica ultrathin films by wet-etching

    Maho Kobayashi, Kyoka Susuki, Tomohiro Otani, Shinpei Enomoto, Haruo Otsuji, Yoshiyuki Kuroda, Hiroaki Wada, Atsushi Shimojima, Takayuki Homma, Kazuyuki Kuroda

    NANOSCALE   9 ( 24 ) 8321 - 8329  2017年06月  [査読有り]

     概要を見る

    The thickness of 3-dimensional (3D) mesoporous silica ultrathin films was controlled at a single-nano-meter scale by wet-etching. A drop casting method with an aqueous etchant of ammonium fluoride was effective in etching the surfaces of films in the direction perpendicular to their substrates. The decrease in the film thickness depends on the interface tension of etching solutions. The wettability of thin films also influences the etching. CoPt nanodots were electrodeposited within ultrathin silica films on Ru substrates to form CoPt nanodot patterns.

    DOI

  • Formation of Nanogrooves with Sub-5 nm Periodicity Using Local Silicification at the Interspace between a Si Substrate and Lyotropic Liquid Crystals

    Shintaro Hara, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    ACS NANO   11 ( 5 ) 5160 - 5166  2017年05月  [査読有り]

     概要を見る

    Bottom-up fabrication of nanopatterns with single nanometer-scale periodicity is quite challenging. In this study, we have focused on the use of the outermost convex surfaces of lyotropic liquid crystals (LLCs) as a template. Periodically arrayed single nanometer-scale nano grooves consisting of silica are successfully formed on a Si substrate covered with LLCs composed of cylindrical micelles of cetyltrimethylammonium chloride. Soluble silicate species are generated from the Si substrate by a treatment with an NH3-water vapor mixture, infilling the interspaces between the Si substrate and the LLCs. The cross section of the nanogrooves has a symmetrical sawtooth-like profile with a periodicity of 4.7 nm, and the depth of each nanogroove is around 2 nm. Uniaxial alignment of the nanogrooves can be achieved using micrometer-scale grooves fabricated by a focused ion beam technique. Although formed nanogrooves contain defects, such as bends and discontinuities, this successful concept provides a novel fabrication method of arrayed concave patterns with sub-5 nm periodicity on the surfaces of Si substrates.

    DOI

  • Direct Synthesis of Highly Designable Hybrid Metal Hydroxide Nanosheets by Using Tripodal Ligands as One-Size-Fits-All Modifiers

    Yoshiyuki Kuroda, Tatsuyuki Koichi, Keisuke Muramatsu, Kazuya Yamaguchi, Noritaka Mizuno, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda

    CHEMISTRY-A EUROPEAN JOURNAL   23 ( 21 ) 5023 - 5032  2017年04月  [査読有り]

     概要を見る

    Brucite-type layered metal hydroxides are prepared from diverse metallic elements and have outstanding functions; however, their poor intercalation ability significantly limits their chemical designability and the use of their potentially ultrahigh surface areas and unique properties as two-dimensional nanosheets. Here, we demonstrate that tripodal ligands (RC(CH2OH)(3), R=NH2, CH2OH, or NHC2H4SO3H) are useful as one-size-fits-all modifiers for the direct synthesis of hybrid metal hydroxide nanosheets with various constituent metallic elements (M=Mg, Mn, Fe, Co, Ni, or Cu) and surface functional groups. The hybrid nanosheets are formed directly from solution phases, and they are stacked into a turbostratic layered structure. The ligands form tridentate Mg-O-C bonds with brucite layers. The hybrid brucite intercalates various molecules and is exfoliated into nanosheets at room temperature, although the non-modified material does not intercalate any molecules. Consequently, both the constituent metallic elements and surface functional groups are freely designed by the direct synthesis.

    DOI

  • Direct Synthesis of Highly Designable Hybrid Metal Hydroxide Nanosheets by Using Tripodal Ligands as One-Size-Fits-All Modifiers

    Yoshiyuki Kuroda, Tatsuyuki Koichi, Keisuke Muramatsu, Kazuya Yamaguchi, Noritaka Mizuno, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda

    Chemistry - A European Journal   23   4949  2017年04月  [査読有り]

     概要を見る

    © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim Invited for the cover of this issue is the group of Yoshiyuki Kuroda and Kazuyuki Kuroda at the Waseda University in Tokyo. The image depicts how the production of diverse metal hydroxide nanosheets can be standardized in the same way as Sushi. Read the full text of the article at 10.1002/chem.201605698.

    DOI

  • Construction of siloxane-based porous materials by using cage-Type element blocks

    Naoto Sato, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Funtai Oyobi Fummatsu Yakin/Journal of the Japan Society of Powder and Powder Metallurgy   64 ( 3 ) 126 - 129  2017年03月  [査読有り]

     概要を見る

    Construction of nanoarchitectures using cage siloxane oligomers as element blocks is of much interest because of its excellent potential for creating novel porous materials. In this review, our recent work on the fabrication of siloxane-based nanostructures from cage siloxanes is presented. The arrangement of cage siloxanes units is controlled by various methods, including amphiphilic self-Assembly and hydrogen bonding of silanol groups, toward the preparation of well-defined porous siloxane-based materials.

    DOI

  • Direct Observation of the Outermost Surfaces of Mesoporous Silica Thin Films by High Resolution Ultralow Voltage Scanning Electron Microscopy

    Maho Kobayashi, Ktoka Susuki, Haruo Otsuji, Yusuke Sakuda, Shunsuke Asahina, Naoki Kikuchi, Toshiyuki Kanazawa, Yoshiyuki Kuroda, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    LANGMUIR   33 ( 9 ) 2148 - 2156  2017年03月  [査読有り]

     概要を見る

    The properties of the outermost surfaces of mesoporous silica thin films are critical in determining their functions. Obtaining information on the presence or absence of silica layers on the film surfaces and on the degree of mesopore opening is essential for applications of surface mesopores. In this study, the outermost surfaces of mesoporous silica thin films with 3-dimensional orthorhombic and 2-dimensional hexagonal structures were observed using ultralow voltage high resolution scanning electron microscopy (HR-SEM) with decelerating optics. SEM images of the surfaces before and after etching with NH4F were taken at various landing voltages. Comparing the images taken under different conditions indicated that the outermost surfaces of the nonetched mesoporous silica thin films are coated with a thin layer of silica. The images taken at an ultralow landing voltage (i.e., 80 V) showed that the presence or absence of surface silica layers depends on whether the film was etched with an aqueous solution of NH4F. The mesostructures of both the etched and nonetched films were visible in images taken at a conventional landing voltage (2 kV); hence, the ultralow landing voltage was more suitable for analyzing the outermost surfaces. The SEM observations provided detailed information about the surfaces of mesoporous silica thin films, such as the degree of pore opening and their homogeneities. AFM images of nonetched 2-dimensional hexagonal mesoporous silica thin films show that the shape of the silica layer on the surface of the films reflects the curvature of the top surface of the cylindrical mesochannels. SEM images taken at various landing voltages are discussed, with respect to the electron penetration range at each voltage. This study increases our understanding of the surfaces of mesoporous silica thin films, which may lead to potential applications utilizing the periodically arranged mesopores on these surfaces.

    DOI

  • Fabrication of colloidal crystals composed of pore-expanded mesoporous silica nanoparticles prepared by a controlled growth method

    Eisuke Yamamoto, Seiya Mori, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda

    NANOSCALE   9 ( 7 ) 2464 - 2470  2017年02月  [査読有り]

     概要を見る

    Colloidal crystals composed of mesoporous silica nanoparticles (MSNs) are expected to have various applications because of their unique hierarchical structures and tunable functions. The expansion of the mesopore size is important for introducing guest species which cannot be accommodated by using conventional colloidal crystals of MSNs; however, the preparation of MSNs with a controllable pore size, suitable for the fabrication of colloidal crystals, still remains a challenge. In this study, we fabricated colloidal crystals composed of pore-expanded MSNs using a sophisticated particle growth method to control the pore size of colloidal MSNs while retaining their monodispersity high enough to form colloidal crystals. By adding triisopropylbenzene (TIPB) only during the growth process with the stepwise addition of tetrapropoxysilane (TPOS), the particle size can be tuned from 60 nm to 100 nm, while the pore size can be tuned from 3 nm to ten plus several nm which is the largest size among the previous MSNs capable of forming colloidal crystals. These novel colloidal crystals should contribute to the expansion of nanomaterials science.

    DOI

  • Synthesis of a 12-membered cyclic siloxane possessing alkoxysilyl groups as a nanobuilding block and its use for preparation of gas permeable membranes

    Masashi Yoshikawa, Hiroya Shiba, Masakoto Kanezashi, Hiroaki Wada, Atsushi Shimojima, Toshinori Tsuru, Kazuyuki Kuroda

    RSC ADVANCES   7 ( 77 ) 48683 - 48691  2017年  [査読有り]

     概要を見る

    A 12-membered cyclic siloxane possessing alkoxysilyl groups was synthesized as a nanobuilding block for siloxane-based materials by the alkoxysilylation of organometallasiloxane containing a 12-membered ring with Si-Me and Si-O- groups as the side groups. The cyclic structure was retained not only in the hydrolysis and condensation reactions (sol-gel process) of the alkoxysilyl groups but also in the xerogel and membrane preparation processes. The degree of condensation of the xerogel derived from the 12-membered ring siloxane was higher than that derived from alkoxysilane monomers, indicating that the alkoxysilylated cyclic oligosiloxane is useful for controlling siloxane networks. A membrane composed of the cyclic siloxane was prepared by coating the hydrolyzed solution onto a porous alumina tube for evaluating the gas permeation properties. The membrane showed a molecular sieving effect for H-2/SF6.

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  • Selective Formation of Alkoxychlorosilanes and Organotrialkoxysilane with Four Different Substituents by Intermolecular Exchange Reaction

    Yuma Komata, Masashi Yoshikawa, Yasuhiro Tamura, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry-An Asian Journal   11 ( 22 ) 3225 - 3233  2016年11月  [査読有り]

     概要を見る

    Alkoxychlorosilanes are scientifically and industrially important toward preparing silicone and silica as well as preparation of siloxane-based nanomaterials by stepwise reactions of Si-OR (R = alkyl) and Si-Cl groups. Intermolecular exchange of alkoxy and chloro groups between alkoxysilanes and chlorosilanes (functional group exchange reaction) provides an efficient and environmentally benign route to alkoxychlorosilanes. BiCl3 as a Lewis acid catalyst can promote the functional group exchange reactions more efficiently than conventional acid catalysts. Higher reactivity has been observed for chlorosilanes with smaller numbers of Si-CH3 groups and for alkoxysilanes with larger numbers of Si-CH3 groups. The reaction mechanism is proposed and selective syntheses of alkoxychlorosilanes are demonstrated. These findings also enable us to synthesize an organotrialkoxysilane with four different substituents.

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  • Use of Mesoporous Silica Modified with Titanium Oxide as a Template for Preparation of Mesoporous Carbon Incorporating TiO2 Nanocrystals

    Masaki Kitahara, Kohei Suzuki, Saori Kubara, Yuta Shimasaki, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   89 ( 10 ) 1207 - 1211  2016年10月  [査読有り]

     概要を見る

    Mesoporous silica modified with titanium oxide is shown to be useful as a template for the preparation of mesoporous carbon incorporating TiO2 nanocrystals. The nanocomposite was prepared by deposition of carbon within the mesoporous silica template modified with titanium oxide, and subsequent template removal with NaOH (aq). The high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) image of the prepared nanocomposite clearly showed that small TiO2 nanocrystals embedded on mesoporous carbon were formed. The Si-O-Ti bonds between mesoporous silica and titanium oxide layers are effective to suppress the migration of the Ti species, resulting in the formation of the TiO2 nanocrystals.

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  • Cover Picture: Cubic Siloxanes with Both Si−H and Si−OtBu Groups for Site-Selective Siloxane Bond Formation (Chem. Eur. J. 39/2016)

    Shohei Saito, Nao Yamasue, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry - A European Journal   22 ( 39 ) 13733  2016年09月  [査読有り]

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  • Cubic Siloxanes with Both Si−H and Si−OtBu Groups for Site-Selective Siloxane Bond Formation

    Shohei Saito, Nao Yamasue, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry - A European Journal   22 ( 39 ) 13857 - 13864  2016年09月  [査読有り]

     概要を見る

    © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Cage-type siloxanes have attracted increasing attention as building blocks for silica-based nanomaterials as their corners can be modified with various functional groups. Cubic octasiloxanes incorporating both Si−H and Si−OtBu groups [(tBuO)nH8−nSi8O12; n=1, 2 or 7] have been synthesized by the reaction of octa(hydridosilsesquioxane) (H8Si8O12) and tert-butyl alcohol in the presence of a Et2NOH catalyst. The Si−H and Si−OtBu groups are useful for site-selective formation of Si−O−Si linkages without cage structure deterioration. The Si−H group can be selectively hydrolyzed to form a Si−OH group in the presence of Et2NOH, enabling the formation of the monosilanol compound (tBuO)7(HO)Si8O12. The Si−OH group can be used for either intermolecular condensation to form a dimeric cage compound or silylation to introduce new reaction sites. Additionally, the alkoxy groups of (tBuO)7HSi8O12can be treated with organochlorosilanes in the presence of a BiCl3catalyst to form Si−O−Si linkages, while the Si−H group remains intact. These results indicate that such bifunctional cage siloxanes allow for stepwise Si−O−Si bond formation to design new siloxane-based nanomaterials.

    DOI

  • Cubic Siloxanes with Both Si−H and Si−OtBu Groups for Site-Selective Siloxane Bond Formation

    Shohei Saito, Nao Yamasue, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry - A European Journal   22   13737  2016年09月  [査読有り]

     概要を見る

    © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Invited for the cover of this issue is the group of Atsushi Shimojima and Kazuyuki Kuroda at Waseda University. The image depicts the structure of cage-type octasiloxane, the smallest “glass” cube in the universe, and its selective functionalization. Read the full text of the article at 10.1002/chem.201601906.

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  • A Mesoporous Superlattice Consisting of Alternately Stacking Interstitial Nanospace within Binary Silica Colloidal Crystals

    Yoshiyuki Kuroda, Yosuke Shimbo, Yasuhiro Sakamoto, Hiroaki Wada, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   55 ( 36 ) 10702 - 10706  2016年08月  [査読有り]

     概要を見る

    A novel class of nonclassical structures of mesoporous silica, namely a binary nanoparticle mesoporous superlattice (BNMS), is obtained by the assembly of silica nanospheres of different sizes into a binary colloidal crystal. The colloidal crystal has a CrB-type structure and consists of alternate stacks of unary fcc and binary AlB2-type structures along the baxis and has four types of interstitial mesopores. The BNMS can be deposited on a substrate by dip coating to form an oriented thin film in which the direction of the superstructure (baxis) is perpendicular to the substrate.

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  • A photoresponsive azobenzene-bridged cubic silsesquioxane network

    Sufang Guo, Tatsuya Okubo, Kazuyuki Kuroda, Atsushi Shimojima

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   79 ( 2 ) 262 - 269  2016年08月  [査読有り]

     概要を見る

    An azobenzene (AZO)-bridged cubic silsesquioxane network exhibiting reversible photoisomerization behavior in nonpolar solvents has been prepared via hydrosilylation reaction between 4,4'-diallyloxy-azobenzene and octahydridosilsesquioxane (H8Si8O12; H-POSS). Approximately 70 % of the corner Si-H groups of H-POSS are reacted to form a three-dimensional gel network while maintaining the cubic siloxane structure. The dried gel has a high thermal stability, which is attributed to the highly cross-linked cubic silsesquioxane network where AZOs are covalently incorporated in the main chain. The gel exhibits reversible swelling behavior in nonpolar solvents during wetting-drying cycles. In toluene, a large extent of reversible trans-cis isomerization of the AZO moiety is observed. These results are promising for the design of a new class of photoresponsive materials applicable in host-guest chemistry.
    [GRAPHICS]

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  • Colloidal Mesoporous Silica Nanoparticles

    Eisuke Yamamoto, Kazuyuki Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   89 ( 5 ) 501 - 539  2016年05月  [査読有り]

     概要を見る

    Mesoporous silica nanoparticles (MSNs) with colloidal stability have attracted increasing interest because of their important properties, such as high transparency and cell uptake. Colloidal MSNs are comprehensively reviewed from the viewpoints of their preparation, characterization, and applications which include biomedical, catalytic, and optical materials. The following two points have been emphasized. The first point is that this review covers the widest range of introduction and discussion of the preparation and applications of both colloidal and noncolloidal MSNs. The second point is that this account contains a discussion from the viewpoints of both inorganic and colloid chemistries. After the introduction of the historical background of preparation of MSNs, preparative methods of colloidal MSNs and the major factors for the preparation of nanosized and colloidal MSNs are discussed. The methods to control the size, composition, morphology, and pore size of MSNs are also presented. Appropriate methods to obtain MSNs with high colloidal dispersibility are also discussed. Applications of colloidal MSNs are introduced with an emphasis on the colloidal stability. Issues to be addressed for further developments of colloidal MSNs are finally described.

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  • A Single-Crystalline Mesoporous Quartz Superlattice

    Takamichi Matsuno, Yoshiyuki Kuroda, Masaki Kitahara, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   55 ( 20 ) 6008 - 6012  2016年05月  [査読有り]

     概要を見る

    There has been significant interest in the crystallization of nanostructured silica into -quartz because of its physicochemical properties. We demonstrate a single-crystalline mesoporous quartz superlattice, a silica polymorph with unprecedentedly ordered hierarchical structures on both the several tens of nanometers scale and the atomic one. The mesoporous quartz superlattice consists of periodically arranged -quartz nanospheres whose crystalline axes are mostly oriented in an assembly. The superlattice is prepared by thermal crystallization of amorphous silica nanospheres constituting a colloidal crystal. We found that the deposition of a strong flux of Li+ only on the surface of silica nanospheres is effective for crystallization.

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  • Usefulness of Mesoporous Silica as a Template for the Preparation of Bundles of Bi Nanowires with Precisely Controlled Diameter Below 10nm

    Masaki Kitahara, Hasbuna Kamila, Atsushi Shimojima, Hiroaki Wada, Takao Mori, Ichiro Terasaki, Kazuyuki Kuroda

    CHEMISTRY-AN ASIAN JOURNAL   11 ( 6 ) 900 - 905  2016年03月  [査読有り]

     概要を見る

    The reduction of the diameter of Bi nanowires below 10nm has been an important target because of the theoretical prediction with regard to significant enhancement in thermoelectric performance by size reduction. In this study, we have demonstrated the usefulness of mesoporous silica with tunable pore size as a template for the preparation of thin Bi nanowires with diameters below 10nm. Bi was deposited within the templates through a liquid phase deposition using hexane and 1,1,3,3-tetramethyldisiloxane as a solvent and reducing agent, respectively. Bundles of thin Bi nanowires with non-crystalline frameworks were successfully obtained after the template removal. The diameter was precisely controlled between about 6nm and 9nm. The judicious choices of mesoporous silica and deposition conditions are critical for the successful preparation. The reliable formation of such thin Bi nanowires reported here opens up exciting new possibilities.

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  • Relationship between Aggregated Structures and Dispersibility of Layered Double Hydroxide Nanoparticles ca. 10 nm in Size and Their Application to Ultrafast Removal of Aqueous Anionic Dye

    Yoshiyuki Kuroda, Kazuya Yamaguchi, Kazuyuki Kuroda, Noritaka Mizuno

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   88 ( 12 ) 1765 - 1772  2015年12月  [査読有り]

     概要を見る

    Layered double hydroxides (LDHs) are anion-exchanging materials applicable to removal of harmful anionic species from water. Here, we report novel highly dispersible LDH nanoparticles (LDHNPs) which can remove methylorange (MO), a model anionic pollutant, quite rapidly. The LDHNPs are prepared by using tris(hydroxymethyl)aminomethane. The LDHNPs aggregate into sheet-like structure by face-to-face association or house-of-cards structure by edge-to-face association. The removal of MO by the LDHNPs with the house-of-cards structure reaches 95% of equilibrium level within only 5 s, which is much faster than the sheet-like aggregates and conventional large LDHs by at least two orders of magnitude. Therefore, it is found that the structural control of aggregates is critical to the dispersibility of LDHNPs and the ultrafast removal of anionic dye.

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  • Photoinduced Bending of Self-Assembled Azobenzene Siloxane Hybrid

    Sufang Guo, Kimihiro Matsukawa, Takashi Miyata, Tatsuya Okubo, Kazuyuki Kuroda, Atsushi Shimojima

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   137 ( 49 ) 15434 - 15440  2015年12月  [査読有り]

     概要を見る

    A novel azobenzene siloxane hybrid material displaying photoinduced macroscopic motions has been prepared by one-step organosilane self-assembly. Two types of alkoxysilane precursors with either pendant or bridging azobenzene groups were synthesized via thiol-ene click reactions. Hybrid films with well-ordered lamellar structures were obtained by hydrolysis and polycondensation of these precursors. The film with solely pendant azobenzene groups showed reversible and rapid d-spacing variation upon UV-vis irradiation, which was induced by the trans-cis isomerization of azobenzene moieties. The flexible, free-standing film obtained by co-condensation of two types of precursors showed reversible bending unbending motions upon UV-vis irradiation. The partial cross-linking between the siloxane layers by bridging azobenzene groups was crucial for photoinduced distortion of the film. This film possesses high elastic modulus, good thermal stability, and shows large amplitude of photoinduced bending unbending over a wide temperature range. This is the first report on photoinduced macroscopic motions of azobenzene-containing siloxane-based materials. These materials possess great potential for applications in smart devices and energy conversion systems.

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  • Preparation of Mesoporous Bimetallic Au-Pt with a Phase-Segregated Heterostructure Using Mesoporous Silica

    Masaki Kitahara, Saori Kubara, Azusa Takai, Daisuke Takimoto, Shinpei Enomoto, Yusuke Yamauchi, Wataru Sugimoto, Kazuyuki Kuroda

    CHEMISTRY-A EUROPEAN JOURNAL   21 ( 52 ) 19142 - 19148  2015年12月  [査読有り]

     概要を見る

    Mesoporous bimetallic Au-Pt with a phase-segregated heterostructure has been prepared by using mesoporous silica SBA-15 as a template. Au nanoparticles were prepared as a seed metal within the mesopores, and subsequently Pt was deposited, sandwiching the Au seeds. Energy-dispersive X-ray (EDX) spectral mapping showed that the framework of mesoporous bimetallic Au-Pt, prepared by removing the silica template with HF, was composed of Au nanoparticles joined with Pt nanowires. The Au/Pt ratio of the mesoporous bimetallic Au-Pt could be varied by controlling the number of Au deposition cycles. Pre-adsorbed CO (COad) stripping voltammetry of the mesoporous bimetallic Au-Pt showed that the surfaces of the joined bimetallic structure were electrochemically active. This could be attributed to the open framework structure having a high ratio of exposed bimetallic mesopore surfaces. The described preparative approach, involving a mesoporous silica template and stepwise deposition within the mesopores, enables control of the nanostructure of the bimetallic material, which is greatly promising for the further development of synthetic methodologies for bimetallic structures.

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  • Interlayer Condensation of Protonated Layered Silicate Magadiite through Refluxing in N-Methylformamide

    Yusuke Asakura, Nami Hosaka, Shimon Osada, Taichi Terasawa, Atsushi Shimojima, Kazuyuki Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   88 ( 9 ) 1241 - 1249  2015年09月  [査読有り]

     概要を見る

    Interlayer-condensed materials of protonated layered silicate (magadiite) are synthesized by refluxing in N-methylformamide (NMF) and the subsequent calcination. The obtained materials possess 2-3 times higher surface areas than calcined protonated magadiite, depending on the time of refluxing. NMF molecules in the interlayer spaces are converted to organic substances with higher thermal stability during the refluxing, which is useful for the control of the stacking sequence of silicate layers and for the following interlayer condensation to increase the microporosity. The microporosity of the material obtained by the treatment of protonated magadiite with NMF at r.t. and the subsequent calcination is similar to that of simply calcined protonated magadiite, indicating that the retention of thermally stable substances in the interlayer is critical for the increase in the pore volume and surface area of the derivative from magadiite. The method reported here will stimulate re-estimation of a large number of known layered silicate organic intercalation compounds as possible candidates for the preparation of porous silica by interlayer condensation.

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  • The Critical Effect of Niobium Doping on the Formation of Mesostructured TiO2: Single-Crystalline Ordered Mesoporous Nb-TiO2 and Plate-like Nb-TiO2 with Ordered Mesoscale Dimples

    Masaki Kitahara, Yuta Shimasaki, Takamichi Matsuno, Yoshiyuki Kuroda, Atsushi Shimojima, Hiroaki Wada, Kazuyuki Kuroda

    CHEMISTRY-A EUROPEAN JOURNAL   21 ( 37 ) 13073 - 13079  2015年09月  [査読有り]

     概要を見る

    Highly ordered mesoporous niobium-doped TiO2 with a single-crystalline framework was prepared by using silica colloidal crystals with ca. 30nm in diameter as templates. The preparation of colloidal crystals composed of uniform silica nanoparticles is a key to obtain highly ordered mesoporous Nb-doped TiO2. The XPS measurements of Nb-doped TiO2 showed the presence of Nb5+ and correspondingly Ti3+. With the increase in the amount of doped Nb, the crystalline phase of the product was converted from rutile into anatase, and the lattice spacings of both rutile and anatase phases increased. Surprisingly, the increase in the amount of Nb led to the formation of plate-like TiO2 with dimpled surfaces on one side, which was directly replicated from the surfaces of the colloidal silica crystals.

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  • Effective Use of Alkoxysilanes with Different Hydrolysis Rates for Particle Size Control of Aqueous Colloidal Mesostructured and Mesoporous Silica Nanoparticles by the Seed-Growth Method

    Hironori Yamada, Chihiro Urata, Eisuke Yamamoto, Sayuri Higashitamori, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMNANOMAT   1 ( 3 ) 194 - 202  2015年07月  [査読有り]

     概要を見る

    The particle sizes of mesoporous silica nanoparticles most greatly affect their properties, including cellular uptake, cytotoxicity, and dispersity. The growth of colloidal mesostructured silica nanoparticles (CMSS) with particle sizes less than 100 nm was controlled by a modified seed-growth method by using alkoxysilanes (Si(OR)(4), R: Me, Et, Pr, and Bu) with different hydrolysis rates as additives. It was confirmed that the approximate matching of the hydrolysis rates of the added silanes with the consumption rates, determined by the total outer surface area of the seeds, is most important. CMSS with narrow particle-size distributions (e.g., 60 or 80 nm in size) were successfully prepared. Si(OPr)(4) was the most suitable additive, though Si(OEt)(4) was also useful for controlled growth. Si(OBu)(4) was usable but needed varied conditions for controlled growth. The meso-structures and the high dispersity of nanoparticles were retained, even after removal of the surfactants of the CMSS by dialysis. These findings should contribute to the more precise control of particle sizes of mesoporous silica nanoparticles and to the deeper understanding of their properties.

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  • Proton tunneling in low dimensional cesium silicate LDS-1

    Hiroshi Matsui, Kei Iwamoto, Dai Mochizuki, Shimon Osada, Yusuke Asakura, Kazuyuki Kuroda

    JOURNAL OF CHEMICAL PHYSICS   143 ( 2 )  2015年07月  [査読有り]

     概要を見る

    In low dimensional cesium silicate LDS-1 (monoclinic phase of CsHSi2O5), anomalous infrared absorption bands observed at 93, 155, 1210, and 1220 cm(-1) are assigned to the vibrational mode of protons, which contribute to the strong hydrogen bonding between terminal oxygen atoms of silicate chain (O-O distance = 2.45 angstrom). The integrated absorbance (oscillator strength) for those modes is drastically enhanced at low temperatures. The analysis of integrated absorbance employing two different anharmonic double-minimum potentials makes clear that proton tunneling through the potential barrier yields an energy splitting of the ground state. The absorption bands at 93 and 155 cm(-1), which correspond to the different vibrational modes of protons, are attributed to the optical transition between the splitting levels (excitation from the ground state (n = 0) to the first excited state (n = 1)). Moreover, the absorption bands at 1210 and 1220 cm(-1) are identified as the optical transition from the ground state (n = 0) to the third excited state (n = 3). Weak Coulomb interactions in between the adjacent protons generate two types of vibrational modes: symmetric mode (93 and 1210 cm(-1)) and asymmetric mode (155 and 1220 cm(-1)). The broad absorption at 100-600 cm(-1) reveals an emergence of collective mode due to the vibration of silicate chain coupled not only with the local oscillation of Cs+ but also with the proton oscillation relevant to the second excited state (n = 2). (C) 2015 AIP Publishing LLC.

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  • Mesoporous TiO2 films with regularly aligned slit-like nanovoids

    Hirokatsu Miyata, Yuta Fukushima, Yosuke Kanno, Saeko Hayase, Shintaro Hara, Masatoshi Watanabe, Shin Kitamura, Masahiko Takahashi, Kazuyuki Kuroda

    Journal of Materials Chemistry C   3 ( 16 ) 3869 - 3875  2015年04月  [査読有り]

     概要を見る

    Novel mesoporous TiO2 films with regularly aligned slit-like nanovoids are prepared through structural transformation from a mesostructured TiO2 film with honeycomb-packed aligned cylindrical micelles by pyrolytic removal of the micelle template. The transformation takes place through interconnection of the TiO2 walls of the framework in the thickness direction by a heat-induced shrinkage and eventual collapse of the original channel structure. For the formation of this new structure, the preparation of a mesostructured titania film with cylindrical micelles aligned entirely in the plane of the film over the whole thickness is indispensable. This is achieved by coating a substrate, on which a rubbing-treated polyimide layer is formed, with a precursor solution containing two nonionic surfactants, Brij56 and P123. In the mixed surfactant system, Brij56 works as an alignment-controlling agent through selective and directional adsorption on the anisotropic polymer surface. On the other hand, P123 suppresses the formation of a surface layer without controlled in-plane alignment, which has been inevitable when Brij56 is used alone. This is caused by the retarded condensation of the TiO2 precursors due to increased coordination of oxyethylene moieties on titanium. P123 also increases the wall thickness of the framework, which also contributes to the formation of this mesoporous TiO2 film with oriented regular slit-like voids. The structural transformation takes place in a relatively low temperature range lower than 300 °C, which shows that the driving force is not crystallization. The mesoporous TiO2 films with aligned slit-like voids show optical anisotropy, birefringence, with a Δn value of ∼0.023 reflecting the structural anisotropy of the film. Calcination of the aligned mesostructured TiO2 film at 450 °C induces crystallization of TiO2, which deteriorates the meso-scale structural regularity by interconnection of the TiO2 walls. However, the partial retention of the regular structure is confirmed in the vicinity of the surface, which allows the retention of the optical anisotropy. The novel mesoporous TiO2 films in this paper have potential for optical applications by combining their unique anisotropic mesostructure, which enhances the accessibility to the inner surface, with various properties of TiO2 such as high refractive index and photocatalytic activity. This journal is

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  • Si Substrate as a SiO2 Source for the Preparation of Mesoporous SiO2-TiO2 Thin Films

    Shintaro Hara, Hirokatsu Miyata, Masahiko Takahashi, Atsushi Shimojima, Kazuyuki Kuroda

    CHEMISTRY LETTERS   44 ( 3 ) 372 - 374  2015年03月  [査読有り]

     概要を見る

    A Si substrate has been proved to be used as a SiO2 source for the preparation of mesoporous silica-titania thin films with cylindrical mesochannels. Exposing mesostructured titania-surfactant thin films to aqueous NH3 vapor reinforces the pore walls with uniformly distributed silicate species, which retain the mesostructure after calcination.

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  • A multifunctional role of trialkylbenzenes for the preparation of aqueous colloidal mesostructured/mesoporous silica nanoparticles with controlled pore size, particle diameter, and morphology

    Hironori Yamada, Hiroto Ujiie, Chihiro Urata, Eisuke Yamamoto, Yusuke Yamauchi, Kazuyuki Kuroda

    NANOSCALE   7 ( 46 ) 19557 - 19567  2015年  [査読有り]

     概要を見る

    Both the pore size and particle diameter of aqueous colloidal mesostructured/mesoporous silica nanoparticles (CMSS/CMPS) derived from tetrapropoxysilane were effectively and easily controlled by the addition of trialkylbenzenes (TAB). Aqueous highly dispersed CMPS with large pores were successfully obtained through removal of surfactants and TAB by a dialysis process. The pore size (from 4 nm to 8 nm) and particle diameter (from 50 nm to 380 nm) were more effectively enlarged by the addition of 1,3,5-triisopropylbenzene (TIPB) than 1,3,5-trimethylbenzene (TMB), and the enlargement did not cause the variation of the mesostructure and particle morphology. The larger molecular size and higher hydrophobicity of TIPB than TMB induce the incorporation of TIPB into micelles without the structural change. When TMB was used as TAB, the pore size of CMSS was also enlarged while the mesostructure and particle morphology were varied. Interestingly, when tetramethoxysilane and TIPB were used, CMSS with a very small particle diameter (20 nm) with concave surfaces and large mesopores were obtained, which may strongly be related to the initial nucleation of CMSS. A judicious choice of TAB and Si sources is quite important to control the mesostructure, size of mesopores, particle diameter, and morphology.

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  • Synthesis of colloidal Janus nanoparticles by asymmetric capping of mesoporous silica with phenylsilsesquioxane

    Hiroto Ujiie, Atsushi Shimojima, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   51 ( 15 ) 3211 - 3214  2015年  [査読有り]

     概要を見る

    Colloidal mesoporous silica nanoparticles asymmetrically capped with non-porous phenylsilsesquioxane have been prepared by adding phenyltriethoxysilane to an aqueous dispersion of mesostructured silica-surfactant composite nanoparticles. The integration of colloidal stability, mesoporosity and the Janus structure is quite promising for materials design applicable in various fields, including catalysis, biomedicine and coatings.

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  • Regular assembly of cage siloxanes by hydrogen bonding of dimethylsilanol groups

    Naoto Sato, Yoshiyuki Kuroda, Takuya Abe, Hiroaki Wada, Atsushi Shimojima, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   51 ( 55 ) 11034 - 11037  2015年  [査読有り]

     概要を見る

    A new class of ordered silica-based materials has been prepared by hydrogen bond-directed assembly of cage siloxanes modified with dimethylsilanol groups, providing a soft-chemical approach to crystalline silica materials with molecularly designed architectures.

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  • Molecularly Designed Nanoparticles by Dispersion of Self-Assembled Organosiloxane-Based Mesophases

    Shigeru Sakamoto, Yasuhiro Tamura, Hideo Hata, Yasuhiro Sakamoto, Atsushi Shimojima, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   53 ( 35 ) 9173 - 9177  2014年08月  [査読有り]

     概要を見る

    The design of siloxane-based nanoparticles is important for many applications. Here we show a novel approach to form core-shell silica nanoparticles of a few nanometers in size through the principle of "dispersion of ordered mesostructures into single nanocomponents". Self-assembled siloxane-organic hybrids derived from amphiphilic alkyl-oligosiloxanes were postsynthetically dispersed in organic solvent to yield uniform nanoparticles consisting of dense lipophilic shells and hydrophilic siloxane cores. In situ encapsulation of fluorescent dyes into the nanoparticles demonstrated their ability to function as nanocarriers.

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  • Electron Microscopy Study of Binary Nanocolloidal Crystals with ico-AB(13) Structure Made of Monodisperse Silica Nanoparticles

    Yasuhiro Sakamoto, Yoshiyuki Kuroda, Susumu Toko, Takuji Ikeda, Toshiyuki Matsui, Kazuyuki Kuroda

    JOURNAL OF PHYSICAL CHEMISTRY C   118 ( 27 ) 15004 - 15010  2014年07月  [査読有り]

     概要を見る

    Binary nanocolloidal crystals (BNCCs) made of two different nanoparticles are a promising new class of advanced functional materials with synergetic and collective properties. These materials have been shown to exhibit excellent structural diversity and a wide range of different stoichiometries. In this study, BNCCs with an ico-AB(13) structure were prepared as inorganic bulk materials by simple solvent evaporation of silica nanocolloidal aqueous solutions. Systematic analysis of Fourier diffractograms of high-resolution transmission electron microscopy (HRTEM) images shows the reflection conditions of the space group Fm (3) over barc without any ambiguities, which is indicative of the ico-AB(13) structure. Simulated HRTEM images based on the ideal ico-AB(13) structure were also calculated under the kinematical scattering approximation. These images showed the characteristic fine structure of the ico-AB(13) structure along the high-symmetry axes. The agreement between the observed and simulated HRTEM images indicates the validity of the ideal ico-AB(13) model structure. This result shows that HRTEM together with a quantitative image simulation is a versatile method for the characterization of the BNCCs at the nanoscale and can be routinely applied for any nanocolloidal crystals, even for complex structures.

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  • Replication of Ordered Mesostructure on the Surface of 2D Hexagonal Mesoporous Silica Film as Exemplified by the Formation of Striped Cu Nanopatterns

    Maho Kobayashi, Yosuke Kanno, Kazuyuki Kuroda

    CHEMISTRY LETTERS   43 ( 6 ) 846 - 848  2014年06月  [査読有り]

     概要を見る

    The surface of 2D hexagonal mesoporous silica film has been successfully etched with ammonium fluoride to form an uncovered and well-defined mold surface. The surface can be effectively used to replicate striped Cu nanopatterns with the same mesoscale periodicity by vapor deposition of Cu.

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  • Silylation of Layered Silicate RUB-51 with SiCl4 and Conversion of the Silylated Derivative to a Crystalline Microporous Material

    Yusuke Asakura, Yasuhiro Sakamoto, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   26 ( 12 ) 3796 - 3803  2014年06月  [査読有り]

     概要を見る

    A novel crystalline microporous material is synthesized by silylation of layered silicate RUB-51 with tetrachlorosilane (SiCl4), hydrolysis, and heat treatment for interlayer condensation. One SiCl4 molecule first undergoes ordered silylation with two confronting groups, Si-O- and Si OH, on the interlayer surfaces of RUB-51 (bidentate silylation). Hydrolysis of the unreacted Si-Cl groups of the immobilized silyl groups by a mixture of H2O and dimethyl sulfoxide (DMSO) affords geminal Si-OH groups on the surfaces without simultaneous interlayer condensation because of intercalation with DMSO. Subsequent heat treatment leads to condensation between neighboring layers, and the condensed material is composed of layers of RUB-51 displaced by a half-unit cell along the a axis. Hydroxyl groups are present after interlayer cross-linking, which is one of the unique features of the method using SiCl4. The obtained sample adsorbs CO2 molecules, while RUB-51 itself without silylation cannot. The amount of adsorbed CO2 on the microporous material is larger than that of CH4, suggesting the potential of this material as a separation medium between CO2 and CH4. This study indicates that the preparation of microporous materials, using layered silicates as a building block and various silylating agents, is useful for precise design of both porosity and functional groups on pore surfaces, which drastically affect the properties of crystalline microporous materials, including catalytic selectivity and separation capability.

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  • Preparation of Size-Controlled Monodisperse Colloidal Mesoporous Silica Nanoparticles and Fabrication of Colloidal Crystals

    Eisuke Yamamoto, Masaki Kitahara, Takuya Tsumura, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   26 ( 9 ) 2927 - 2933  2014年05月  [査読有り]

     概要を見る

    Although mesoporous silica particles are useful building blocks for colloidal crystals, mesoporous silica nanoparticles smaller than 100 nm with sufficient monodispersity and colloidal stability to enable thermodynamic assemblies have not been reported. Here, we report that highly monodisperse colloidal mesoporous silica nanoparticles (CMS) can be prepared by combining the preparation of colloidal mesoporous silica nanoparticles with a shortened nucleation time. The nanoparticles exhibited a uniform shape and relatively smooth surface because an undesirable aggregate dispersion process was avoided. In addition, the diameter of the nanoparticles was controlled by seed-growth without spontaneous nucleation, which enabled the investigation of fundamental CMS properties. Using monodisperse CMS, the dependence of the zeta-potential of CMS on the diameter was revealed. Colloidal crystals composed of mesoporous silica nanoparticles were fabricated by drying the colloidal solution. This is the first report regarding the fabrication of colloidal crystals composed of mesoporous silica nanoparticles with a small particle size.

    DOI

  • Critical Roles of Cationic Surfactants in the Preparation of Colloidal Mesostructured Silica Nanoparticles: Control of Mesostructure, Particle Size, and Dispersion

    Hironori Yamada, Chihiro Urata, Sayuri Higashitamori, Yuko Aoyama, Yusuke Yamauchi, Kazuyuki Kuroda

    ACS APPLIED MATERIALS & INTERFACES   6 ( 5 ) 3491 - 3500  2014年03月  [査読有り]

     概要を見る

    Mesoporous silica nanoparticles are promising materials for various applications, such as drug delivery and catalysis, but the functional roles of surfactants in the formation and preparation of mesostructured silica nanoparticles (MSN-as) remain to be seen. It was confirmed that the molar ratio of cationic surfactants to Si of alkoxysilanes (Surf/Si) can affect the degree of mesostructure formation (i.e., whether the mesochannels formed inside the nanoparticles actually pass through the outer surface of the particles), the particle diameter, and the dispersibility of MSN-as. Wormhole-like mesostructures formed with low Surf/Si ratios; however, the mesopores did not pass through the outer surface of the particles completely. At high Surf/Si ratios, the mesostructures extended. The particle diameter was 100 nm or larger at low Surf/Si ratios, and the primary particle diameter decreased as the Surf/Si ratio increased. This was because the surfactants enhanced the dispersity of the alkoxysilanes in water and the hydrolysis rate of the alkoxysilanes became faster, leading to an increased nucleation as compared to the particle growth. Moreover, primary particles aggregated at low Surf/Si ratios because of the hydrophobic interactions among the surfactants that were not involved in the mesostructure formation but were adsorbed onto the nanoparticles. At high Surf/Si ratios, the surfactant micelles were adsorbed on the surface of primary particles (admicelles), resulting in the dispersion of the particles due to electrostatic repulsion. In particular, molar ratios of 0.13 or higher were quite effective for the preparation of highly dispersed MSN-as. Surfactants played important roles in the mesostructure formation, decreasing the particle diameters, and the dispersibility of the particles. All of these factors were considerably affected by the Surf/Si ratio. The results suggested novel opportunities to control various colloidal mesostructured nanoparticles from the aspects of composition, structure, and morphology and will also be useful in the development of novel methods to prepare nanomaterials in various fields.

    DOI

  • Topotactic conversion of β-helix-layered silicate into AST-type zeolite through successive interlayer modifications

    Yusuke Asakura, Ryosuke Takayama, Toshimichi Shibue, Kazuyuki Kuroda

    Chemistry - A European Journal   20 ( 7 ) 1893 - 1900  2014年02月  [査読有り]

     概要を見る

    AST-type zeolite with a plate morphology can be synthesized by topotactic conversion of a layered silicate (β-helix-layered silicate; HLS) by using N,N-dimethylpropionamide (DPA) to control the layer stacking of silicate layers and the subsequent interlayer condensation. Treatment of HLS twice with 1)hydrochloric acid/ethanol and 2)dimethylsulfoxide (DMSO) are needed to remove interlayer hydrated Na ions and tetramethylammonium (TMA) ions in intralayer cup-like cavities (intracavity TMA ions), both of which are introduced during the preparation of HLS. The utilization of an amide molecule is effective for the control of the stacking sequence of silicate layers. This method could be applicable to various layered silicates that cannot be topotactically converted into three-dimensional networks by simple interlayer condensation by judicious choice of amide molecules. © 2014 Wiley-VCH Verlag GmbH& Co. KGaA, Weinheim.

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  • Preparation of highly controlled nanostructured Au within mesopores using reductive deposition in non-polar environments

    Masaki Kitahara, Kazuyuki Kuroda

    RSC ADVANCES   4 ( 52 ) 27201 - 27206  2014年  [査読有り]

     概要を見る

    This paper describes a sophisticated and unique method of Au deposition exclusively inside mesoporous silica, in clear contrast to general methods requiring surface modification with organic functional groups interacting with Au. Reductive deposition using hexane and 1,1,3,3-tetramethydisiloxane as solvent and reducing agent, respectively, was very successful in the inside deposition of Au in two-dimensional hexagonal mesoporous silica (SBA-15). This result was attributed to the suppression of the migration of Au species (Au ions, atoms, and clusters) inside SBA-15 by forcibly locating Au species near the relatively polar mesopore surfaces in the presence of highly non-polar compounds in the mesochannels. Au nanorods replicated from the pore shape of SBA-15 were prepared by reductive deposition, while Au nanoparticles were selectively formed by performing the deposition in the presence of hexadecyltrimethylammonium bromide, which shows promise in the further development of precise design strategies for nanostructured Au.

    DOI

  • Utilization of Alkoxysilyl Groups for the Creation of Structurally Controlled Siloxane-Based Nanomaterials

    Kazuyuki Kuroda, Atsushi Shimojima, Kazufumi Kawahara, Ryutaro Wakabayashi, Yasuhiro Tamura, Yusuke Asakura, Masaki Kitahara

    CHEMISTRY OF MATERIALS   26 ( 1 ) 211 - 220  2014年01月  [査読有り]

     概要を見る

    Silica-based materials have found many applications in various fields. Alkoxysilanes have been most widely used as precursors. Fine structural control of silica-based materials has become increasingly important for tuning their properties and for developing new functions. In this perspective, utilization of alkoxysilyl groups has been reviewed from the viewpoint of designing siloxane-based nanomaterials. Alkoxy groups have generally been used only as eliminating groups in the sol-gel processing; however, recent research has shown that they are useful for molecular assembly, for generating pores, for linking nanobuiliding blocks, and for selective synthesis of new oligosiloxane compounds.

    DOI

  • Films with Tunable Graded Refractive Index Consisting of Spontaneously Formed Mesoporous Silica Nanopinnacles

    Shin Kitamura, Yosuke Kanno, Masatoshi Watanabe, Masahiko Takahashi, Kazuyuki Kuroda, Hirokatsu Miyata

    ACS PHOTONICS   1 ( 1 ) 47 - 52  2014年01月  [査読有り]

     概要を見る

    Coatings with surfaces packed with pointed projections with subwavelength sizes are known as "moth-eye", whose graded index structure gives superior antireflection (AR) properties with a small dependence on wavelength and incident angle. However, the optical interface between the AR coating and a substrate still causes reflection, unless the refractive index of the coating is matched to that of the substrate. Here, we show a new AR coating with both graded and tunable refractive index, which completely eliminates distinct optical interfaces. The coating is made of a mesoporous silica film, whose surface is spontaneously converted to an assembly of pointed nanostructure by reactive ion etching, and its refractive index is matched universally to that of a substrate by controlled incorporation of titanium dioxide into the mesopores. This AR coating enables universal ultralow reflection on a substrate over the index range from 1.2 to 1.8 and will be applied widely in practical optics.

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  • Multiphase coexistence and destabilization of liquid crystalline binary nanosheet colloids of titanate and clay

    Teruyuki Nakato, Yoshie Yamashita, Emiko Mouri, Kazuyuki Kuroda

    SOFT MATTER   10 ( 18 ) 3161 - 3165  2014年  [査読有り]

     概要を見る

    Aplate-plate binary colloid system of photocatalytically active titanate and inert clay nanosheets shows macroscopically separated multiphase coexistence. Two liquid crystalline phases and one isotropic phase coexist at high titanate and low clay concentrations whereas the colloids are destabilized at high clay concentrations.

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  • Optimal topotactic conversion of layered octosilicate to RWR-type zeolite by separating the formation stages of interlayer condensation and elimination of organic guest molecules

    Yusuke Asakura, Shimon Osada, Nami Hosaka, Taichi Terasawa, Kazuyuki Kuroda

    DALTON TRANSACTIONS   43 ( 27 ) 10392 - 10395  2014年  [査読有り]

     概要を見る

    We demonstrate that the separation of two stages of interlayer condensation under refluxing and elimination of organic guests provides the optimal conditions for the formation of RWR-type zeolite from layered octosilicate. The obtained RWR-type zeolite has higher quality than any other RWR-type zeolite reported previously.

    DOI

  • Synthesis of a multifunctional alkoxysiloxane oligomer

    Masashi Yoshikawa, Ryutaro Wakabayashi, Misa Tamai, Kazuyuki Kuroda

    NEW JOURNAL OF CHEMISTRY   38 ( 11 ) 5362 - 5368  2014年  [査読有り]

     概要を見る

    An alkoxysiloxane oligomer (1, SiMe[OSi(CH=CH2)(OMe)(2)][OSi(CH2)(3)Cl(OMe)(2)](2)), containing vinyl and chloropropyl groups, was synthesized as a precursor for sol-gel synthesis. Di-tert-butoxymethylhydroxysilane (t-BuO)(2)MeSiOH was reacted with (MeO)(2)(CH2=CH)SiCl to form (t-BuO)(2)MeSiOSi(CH=CH2)(OMe)(2) which was further alkoxysilylated with Cl(CH2)(3)SiCl(OMe)(2) to form 1. The H-1, C-13, Si-29 NMR and HR-MS data confirmed the formation of 1, indicating the successful synthesis of an alkoxysiloxane oligomer possessing different kinds of functional groups by a chemoselective route. Hydrolysis of 1 under acidic conditions was completed in a few hours. The solution state Si-29 NMR spectra of samples hydrolyzed and condensed at various reaction times show no signals due to species generated by the cleavage of the siloxane bonds in 1, indicating the validity of the synthesized substance as a precursor for the formation of hybrids with homogeneously distributed functional groups. Intramolecular condensation of 1 to form cyclic trisiloxane units proceeds more preferentially than intermolecular condensation.

    DOI

  • Siloxane-Bond Formation Promoted by Lewis Acids: A Nonhydrolytic Sol-Gel Process and the Piers-Rubinsztajn Reaction

    Ryutaro Wakabayashi, Kazuyuki Kuroda

    CHEMPLUSCHEM   78 ( 8 ) 764 - 774  2013年08月  [査読有り]

     概要を見る

    Siloxane formation reactions of both the nonhydrolytic sol-gel process and Piers-Rubinsztajn reaction can be integrated as Lewis acid promoted siloxane syntheses without involving silanol groups. The former was developed in the field of inorganic materials chemistry and the latter was initiated in polymer chemistry. We have realized both reactions are quite similar, in terms of 1)the nonhydrolytic reaction, 2)the use of alkoxysilanes, 3)the group-exchange reactions competing with the siloxane formation, and 4)the proposed reaction mechanisms. This Minireview focuses on the above two reactions. The evolution of both reactions should realize a more sophisticated molecular design of siloxane compounds, which surely contributes to the development of advanced functional materials.

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  • Mesoporous Silica

    T. Kimura, K. Kuroda

    Comprehensive Inorganic Chemistry II (Second Edition): From Elements to Applications   5   133 - 150  2013年08月  [査読有り]

     概要を見る

    Porous materials are categorized on the basis of pore size. Mesoporous materials possess a large number of pores ranging from 2 to 50. nm in size. Periodic mesostructures of various compositions, including inorganic oxides and metal phosphates, are successfully replicated by using amphiphilic organic molecules possessing a self-assembling property. It is essential for the preparation of periodic mesoporous materials to generate the interactions between soluble inorganic species and amphiphilic organic molecules. Amphiphilic organic molecules, whose hydrophilic headgroups are interacted with inorganic species, are self-assembled with gradual condensation of inorganic species, being called as 'cooperative organization' for the formation of periodic mesostructures. Materials with uniform mesopores can then be prepared after the removal of surfactant assemblies. Such periodic mesoporous materials have been expected as reaction vessels showing high selectivity for relatively large organic molecules and thus increasingly and widely investigated. © 2013 Elsevier Ltd. All rights reserved.

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  • Platinum Nanopeapods: Spatial Control of Mesopore Arrangements by Utilizing a Physically Confined Space

    Azusa Takai, Yasuhiro Sakamoto, Osamu Terasaki, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMISTRY-A EUROPEAN JOURNAL   19 ( 35 ) 11564 - 11567  2013年08月  [査読有り]

     概要を見る

    Spherical mesopores: Mesoporous Pt rods containing cage-type mesopores were prepared with porous anodic alumina membranes (PAAMs). It is noteworthy that spherical mesopores are aligned in the rods due to physical confinement by the PAAM channels. Both the mesopore alignment and the morphological control are realized simultaneously, which could be important for bottom-up approaches to nanometals with desirable structural features (see figure). Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

    DOI

  • Heteroepitaxial Formation of Aligned Mesostructured Silica Films with Large Structural Periodicities from Mixed Surfactant Systems

    Saeko Hayase, Yosuke Kanno, Masatoshi Watanabe, Masahiko Takahashi, Kazuyuki Kuroda, Hirokatsu Miyata

    LANGMUIR   29 ( 23 ) 7096 - 7101  2013年06月  [査読有り]

     概要を見る

    Liquid-crystal phases consisting of cylindrical micelles of amphiphilic block copolymers and silica precursors are epitaxially built up on aligned surface micelles formed by an alkyl-PEO surfactant, Brij56, irrespective of the large difference in the intrinsic structural periodicities resulting in the formation of fully aligned mesostructured silica films with large lattice constants. Brij56 works as an alignment controlling agent on rubbing-treated polyimide through selective adsorption from a precursor solution containing the two surfactants, a block copolymer and Brij56, through strong hydrophobic interactions to form an anisotropic surface micelle structure. Aligned mesostructured silica layers with larger periodicities, which dominantly consist of block copolymers, form on these aligned surface micelles by gradually changing the vertical periodicity keeping the lateral intermicelle distance constant. This can be regarded as a kind of heteroepitaxy because the lattice constant at the surface is different from that of the bulk of the film. On the basis of this new concept, highly aligned mesostructured silica films with structural periodicities as large as 10 tun are successfully formed, which has never been achieved when the block copolymers are used alone as the structure-directing agent. The periodicity of the aligned films can precisely be controlled by an appropriate choice of block copolymers and the mixing ratio of the two surfactants, which increases the opportunity for applications of these films with highly anisotropic mesoscale structure.

    DOI PubMed

  • Formation of Au Nanostructure by Electrodeposition in a Mesoporous Silica Film with Interconnected Cage-Type Mesopores

    Yosuke Kanno, Kazuyuki Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   86 ( 5 ) 583 - 585  2013年05月  [査読有り]

     概要を見る

    A mesoporous silica film with interconnected cage-type mesopores is found to work as a scaffold to construct a novel nanostructured Au by electrodeposition. The nanostructure consists of Au nanoparticles located in the mesopores and they are connected to each other, which induces a red shift in the visible absorption band.

    DOI

  • Lattice matching in the epitaxial formation of mesostructured silica films

    Hirokatsu Miyata, Shimon Kobori, Wataru Kubo, Masatoshi Watanabe, Kazuyuki Kuroda

    Langmuir   29 ( 2 ) 761 - 765  2013年01月  [査読有り]

     概要を見る

    Crystallographic orientation of mesostructured silica films on a substrate drastically changes when the substrate is modified with an anisotropic surface. The «01» axis of a two-dimensional (2D) hexagonal structure of the film prepared on a polyimide surface using C22EO20 as a structure-directing agent changes from perpendicular to parallel with respect to the substrate after a rubbing treatment of polyimide, which is accompanied by the simultaneous unidirectional alignment of the cylindrical pores in the plane of the film. The normal direction of the film is «21», which has never been observed in the mesostructured silica films reported so far including those with controlled in-plane alignment of the mesochannels. The change of the orientation with respect to the substrate can be explained by the increased lateral distance between the adjacent surface micelles, which is caused by the elongation of the alkyl chains of the surfactant molecules induced by the adsorption onto the polymer surface with a molecular-level anisotropy. These results show that the total structural orientation of the mesostructured silica film is determined by the matching of the intrinsic lattice constant of the mesostructured silica with that of the surface micelle structure on a substrate. © 2012 American Chemical Society.

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  • Exfoliation of Layered Octosilicate by Simple Cation Exchange with Didecyldimethylammonium Ions

    Shimon Osada, Aoi Iribe, Kazuyuki Kuroda

    CHEMISTRY LETTERS   42 ( 1 ) 80 - 82  2013年01月  [査読有り]

     概要を見る

    Layered octosilicate was exfoliated by stirring didecyldimethylammonium-exchanged silicate in pentane with ultrasonication. The silicate framework was retained at least partly even after the exfoliation. Loosely arranged decyl groups in the interlayers probably induce the exfoliation. This exfoliation method should be applicable to other layered alkali silicates.

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  • Electrochemical Preparation of Controllably Large-sized Mesoporous Platinum Films by Using Diblock Copolymers and an Organic Expander

    Kaori Sekine, Yoji Doi, Azusa Takai, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMISTRY LETTERS   42 ( 1 ) 52 - 54  2013年01月  [査読有り]

     概要を見る

    Mesoporous Pt films with controllably large-sized mesopores were prepared by using a diblock copolymer (polystyrene-b-poly(ethylene oxide), PS-b-PEO) and an organic expander (polystyrene homopolymer, h-PS). With the increase in the molecular weight of PS-b-PEO, the mesopore size gradually increased. All films possess spherical cage-type mesopores irrespectively of both the molecular weight of PS-b-PEO and the use of the expander.

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  • A novel route for preparation of Ti-containing mesoporous silica with high catalytic performance by using a molecular precursor tetrakis(tris-tert-butoxysiloxy)titanium

    Kwang-Min Choi, Toshiyuki Yokoi, Takashi Tatsumi, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY A   1 ( 7 ) 2485 - 2494  2013年  [査読有り]

     概要を見る

    Mesoporous silica containing isolated Ti with variable Si/Ti ratios was prepared by pyrolysis of a mixture of tetrakis(tris-tert-butoxysiloxy)titanium (TS4) and tetraethoxysilane (TEOS) through a hard template method. TEOS plays two roles as a silica source and solvent. TS4 works as a catalyst for the hydrolysis of TEOS. Titanium species are found to be isolated in the silica frameworks, supported by DR-UV-vis, FT-IR, ESR, and XPS. The mesoporous structure was verified by XRD, N-2 adsorption, and SEM. The results of the catalytic performance for the oxidation reaction of cyclohexene using tert-butoxy hydrogen peroxide (TBHP) as oxidant show that high conversion (29%) of cyclohexene and selectivity (98%) of cyclohexene oxide are realized for the Ti-containing mesoporous silica with Si/Ti ratios of 28 and 51.

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  • Preparation of aqueous colloidal mesostructured and mesoporous silica nanoparticles with controlled particle size in a very wide range from 20 nm to 700 nm

    Hironori Yamada, Chihiro Urata, Hiroto Ujiie, Yusuke Yamauchi, Kazuyuki Kuroda

    NANOSCALE   5 ( 13 ) 6145 - 6153  2013年  [査読有り]

     概要を見る

    Particle size control of colloidal mesoporous silica nanoparticles (CMPS) in a very wide range is quite significant for the design of CMPS toward various applications, such as catalysis and drug delivery. Various types of CMPS and their precursors (colloidal mesostructured silica nanoparticles (CMSS)) with different particle sizes (ca. 20-700 nm) were newly prepared from tetraalkoxysilanes with different alkoxy groups (Si(OR)(4), R = Me, Et, Pr, and Bu) in the presence of alcohols (R'OH, R' = Me, Et, Pr, and Bu) as additives. CMSS with larger particle size were obtained by using tetrabutoxysilane (TBOS) and by increasing the amount of BuOH, which is explained by both the difference in the hydrolysis rates of tetraalkoxysilanes themselves and the effect of added alcohols on the hydrolysis rates of tetraalkoxysilanes. Larger amounts of alcohols with longer alkyl chains decrease the hydrolysis rates of tetraalkoxysilanes and the subsequent formation rates of silica species. Thus, the preferential particle growth of CMSS to nucleation occurs, and larger CMSS are formed. Highly dispersed CMPS were prepared by the removal of surfactants of CMSS by dialysis which can lead to the preparation of CMPS without aggregation. Therefore, the particle size control through the tuning of the hydrolysis rate of tetraalkoxysilanes can be conducted by a one-pot and easy approach. Even larger CMPS (ca. 700 nm in size) show relatively high dispersibility. This dispersibility will surely contribute to the design of materials both retaining nanoscale characteristics and avoiding various nanorisks.

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  • Preparation of Au Nanowire Films by Electrodeposition Using Mesoporous Silica Films as a Template: Vital Effect of Vertically Oriented Mesopores on a Substrate

    Yosuke Kanno, Takashi Suzuki, Yusuke Yamauchi, Kazuyuki Kuroda

    JOURNAL OF PHYSICAL CHEMISTRY C   116 ( 46 ) 24672 - 24680  2012年11月  [査読有り]

     概要を見る

    Films consisting of polycrystalline Au nanowires were prepared by electrodeposition using mesoporous silica films with vertically oriented mesochannels as a template. The importance of the mesostructure near the surface of the substrate is emphasized by the comparison of films possessing vertically aligned mesochannels to the substrate with those having parallel aligned mesochannels from the viewpoints of Au deposition in the films and the presence or absence of the resulting cracking. When all mesopores lie parallel to the substrate, the mesoporous film was cleaved by the deposition of Au, which is in clear contrast to the case of Pt deposition. Fabricated Au nanowires are not interconnected with each other unlike Pt, irrespective of the presence of interconnected micropores.

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  • Direct alkoxysilylation of alkoxysilanes for the synthesis of explicit alkoxysiloxane oligomers

    Ryutaro Wakabayashi, Misa Tamai, Kazufumi Kawahara, Hiroki Tachibana, Yutaka Imamura, Hiromi Nakai, Kazuyuki Kuroda

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   716   26 - 31  2012年10月  [査読有り]

     概要を見る

    Direct alkoxysilylation, which is a powerful tool to provide explicit alkoxysiloxanes, is developed and its versatility is investigated. Siloxane pentamers Si[OSiR1(OMe)(2)](4) having various functional groups (R-1 = methyl, vinyl, phenyl, chloropropyl and n-butyl groups) were successfully obtained by direct alkoxysilylation of Si(OR)(4) (R= t-Bu, CHPh2). Thus, the versatility of the reaction is confirmed on organic functional groups R-1. Functional group tolerance of the reaction is discussed on the basis of electro-negativity of the R-1 groups. Alkoxysilylation of Si(Ot-Bu)(2)(OMe)(2) and Si(Ot-Bu)(OMe)(3) selectively gives trimer (MeO)(2)Si[OSiMe(OMe)(2)](2) and dimer (MeO)(3)SiOSiMe(OMe)(2), respectively. Thus, the feasibility on siloxane structure is also confirmed. Various siloxane compounds are synthesized by this newly developed reaction for the first time. (C) 2012 Published by Elsevier B.V.

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  • Selective Cleavage of Periodic Mesoscale Structures: Two-Dimensional Replication of Binary Colloidal Crystals into Dimpled Gold Nanoplates

    Yoshiyuki Kuroda, Yasuhiro Sakamoto, Kazuyuki Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   134 ( 20 ) 8684 - 8692  2012年05月  [査読有り]

     概要を見る

    Specific crystallographic planes of binary colloidal crystals consisting of silica nanoparticles are two-dimensionally replicated on the surface of gold nanoplates. The selectivity of the surface patterns is explained by the geometrical characteristics of the binary colloidal crystals as templates. The binary colloidal crystals with the AlB2- and NaZn13-type structures are fabricated from aqueous dispersions of stoichiometrically mixed silica nanoparticles with different sizes. The stoichiometry is precisely controlled on the basis of a seed growth of silica nanoparticles. Dimpled gold nanoplates are formed by the two-dimensional growth of gold between partially cleaved surfaces of templates. The selectivity of the surface patterns is explained using the AlB2-type binary colloidal crystal as a template. The surface pattern is determined by the preferential cleavage of the plane with the lowest density of particle-particle connections. The tendency to form well-defined cleavage in binary colloidal crystals is crucial to formation of dimpled gold nanoplates, which is explained using the NaZn13-type binary colloidal crystal as a template. Its complex structure does not show well-defined cleavage, and only distorted nanoplates are obtained. Therefore, the mechanism of the two-dimensional replication of binary colloidal crystals is reasonably explained on the basis of their periodic mesoscale structures and crystal-like properties.

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  • Preparation of Colloidal Mesoporous Silica Nanoparticles with Different Diameters and Their Unique Degradation Behavior in Static Aqueous Systems

    Hironori Yamada, Chihiro Urata, Yuko Aoyama, Shimon Osada, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   24 ( 8 ) 1462 - 1471  2012年04月  [査読有り]

     概要を見る

    The degradation of colloidal mesoporous silica nanoparticles (CMPS) is quite important for the design of stable catalyst supports and biodegradable drug delivery systems carriers. The degradation of various silica nanoparticles in static aqueous systems was investigated. The condition was achieved through the use of a dialysis tube. Four types of CMPS with different particle diameters (ca. 20-80 nm) were newly prepared from tetraalkoxysilanes (Si(OR)(4), R = Me, Et, Pr, and Bu) at different hydrolysis rates by a one-pot synthesis. Larger particles were formed by using tetraalkoxysilanes at slower hydrolysis rates because particle growth dominates nucleation. The degradation of CMPS is independent of diameter differences. The degradation rate of CMPS is higher than that of colloidal nonporous silica nanoparticles with smaller diameters because of the presence of mesopores. CMPS are also more degradable than aggregated CMPS because of colloidal clispersity. Moreover, it was confirmed for the first time that the degradation simultaneously proceeds from the outer as well as the inner surfaces of CMPS and that the mesostructure and morphology are partly retained even after more than half of the CMPS are degraded. The information on the degradation reported here is quite useful for the design of silica-based nanomaterials with tunable degradability/stability.

    DOI

  • Electrochemical Synthesis of Mesoporous Pt-Au Binary Alloys with Tunable Compositions for Enhancement of Electrochemical Performance

    Yusuke Yamauchi, Akihisa Tonegawa, Masaki Komatsu, Hongjing Wang, Liang Wang, Yoshihiro Nemoto, Norihiro Suzuki, Kazuyuki Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   134 ( 11 ) 5100 - 5109  2012年03月  [査読有り]

     概要を見る

    Mesoporous Pt-Au binary alloys were electrochemically synthesized from lyotropic liquid crystals (LLCs) containing corresponding metal species. Two-dimensional exagonally ordered LLC templates were prepared on conductive substrates from diluted surfactant solutions including water, a nonionic surfactant, ethanol, and metal species by drop-coating. Electrochemical synthesis using such LLC templates enabled the preparation of ordered mesoporous Pt-Au binary alloys without phase segregation. The framework composition in the mesoporous Pt-Au alloy was controlled simply by changing the compositional ratios in the precursor solution. Mesoporous Pt-Au alloys with low Au content exhibited well-ordered 2D hexagonal mesostructures, reflecting those of the original templates. With increasing Au content, however, the mesostructural order gradually decreased, thereby reducing the electrochemically active surface area. Wide-angle X-ray diffraction profiles, X-ray photoelectron spectra, and elemental mapping showed that both Pt and Au were atomically distributed in the frameworks. The electrochemical stability of mesoporous Pt-Au alloys toward methanol oxidation was highly improved relative to that of nonporous Pt and mesoporous Pt films, suggesting that mesoporous Pt-Au alloy films are potentially applicable as electrocatalysts for direct methanol fuel cells. Also, mesoporous Pt-Au alloy electrodes showed a highly sensitive amperometric response for glucose molecules, which will be useful in next-generation enzyme-free glucose sensors.

    DOI

  • Polymorph Control of Calcium Carbonate on the Surface of Mesoporous Silica

    Kwang-Min Choi, Kazuyuki Kuroda

    CRYSTAL GROWTH & DESIGN   12 ( 2 ) 887 - 893  2012年02月  [査読有り]

     概要を見る

    The influence of mesoporous silica on the polymorph selectivity in CaCO3 has been investigated. Vaterite is selectively formed from an aqueous solution containing CaCl2 and Na2CO3 by precipitation under the presence of KIT-6-type mesoporous silica. Crystallization time of vaterite from amorphous calcium carbonate (ACC) is much longer on the addition of KIT-6 than that reported previously, indicating the remarkable stabilization of ACC on the surface of mesoporous silica. Other types of silica affect the polymorph selectivity; the addition of amorphous silica gel or assembled silica nanoparticles 12 nm in particle size induced the formation of vaterite as a main phase whereas the presence of assembled silica nanoparticles 30 nm in particle size resulted in the formation of calcite as a main phase with a minor component of vaterite. Therefore, the porous nature of the surfaces of silica greatly influences the polymorph, and a sort of "surface confinement" should play a major role in the selectivity of polymorph.

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  • Uniform and high dispersion of gold nanoparticles on imogolite nanotubes and assembly into morphologically controlled materials

    Yoshiyuki Kuroda, Kohta Fukumoto, Kazuyuki Kuroda

    APPLIED CLAY SCIENCE   55   10 - 17  2012年01月  [査読有り]

     概要を見る

    Morphologically controlled materials consisting of imogolite nanotubes and gold nanoparticles were prepared by electrostatic assembly. The composites consisting of imogolite nanotubes and gold nanoparticles (ca. 2 or 3 nm) were highly dispersed in water and they were subsequently used as building blocks of morphologically controlled materials. The formation of the composites was based on the electrostatic interactions between the surface carboxylato groups of gold nanoparticles and positively charged imogolite nanotubes. The composites were assembled to form free-standing films by filtration and into hollow spheres by the colloidal templating technique accompanied with the layer-by-layer technique. The free-standing films showed intense colors due to the gold nanoparticles, which makes the films useful as color filters. Hollow spheres were found to be useful as catalyst supports, because most of the gold nanoparticles retained their size as ca. 3 nm even after the heating at 500 degrees C. Imogolite nanotubes enabled facile morphological control of functionalized materials and are useful because of their transparency, stability, and high porosity. (C) 2011 Elsevier B.V All rights reserved.

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  • A Novel Preparative Method of Silica Nanotubes by Utilizing Self-assembly and Disassembly of Peptide Amphiphiles

    Tomoko Shimada, Yasuhiro Tamura, Matthew Tirrell, Kazuyuki Kuroda

    CHEMISTRY LETTERS   41 ( 1 ) 95 - 97  2012年01月  [査読有り]

     概要を見る

    The addition of 2,2,2-trifluoroethanol (TFE) induces both the transition from beta-sheet to alpha-helix structure of peptides and disassembly of wormlike micelles of peptide amphiphiles. The hierarchical structural changes were utilized for the preparation of silica nanotubes from silica-micelle complexes with avoiding structural deterioration that is normally caused by thermal treatment. This method is advantageous for the preparation of silica nanotubes because of reusability of peptide templates, possible replication of the surface of beta-sheet structure, and very mild conditions.

    DOI

  • Preparation of Ni nanoparticles between montmorillonite layers utilizing dimethylaminoborane as reducing agent

    Yusuke Yamauchi, Tetsuro Itagaki, Tokihiko Yokoshima, Kazuyuki Kuroda

    DALTON TRANSACTIONS   41 ( 4 ) 1210 - 1215  2012年  [査読有り]

     概要を見る

    Preparation of Ni nanoparticles between montmorillonite layers using dimethylaminoborane (DMAB) as a reducing agent is reported. The DMAB molecules are first intercalated into the interlayer space of Ni-montmorillonite (Ni-mont). Then, as a result of a heating process, the DMAB is decomposed to release electrons for the reduction of the Ni ions. From high-resolution TEM images, it is demonstrated that the deposited Ni nanoparticles with about 1-2 nm in size are formed uniformly over the entire area of the Ni-mont matrix. Considering the gallery height calculated by subtracting the silicate sheet thickness from the basal spacing (1.30 nm), the morphology of the formed Ni nanoparticles in the interlayer space is thought to be disc-like in shape with a thickness of 0.3-0.4 nm and an average lateral size of 1.2 nm.

    DOI

  • A spherosilicate oligomer with eight stable silanol groups as a building block of hybrid materials

    Kazufumi Kawahara, Hiroki Tachibana, Yoshiaki Hagiwara, Kazuyuki Kuroda

    NEW JOURNAL OF CHEMISTRY   36 ( 5 ) 1210 - 1217  2012年  [査読有り]

     概要を見る

    Diphenylsilylated double four-membered ring (D4R) spherosilicate possessing eight stable silanol groups (((RR2)-R-1(HO)SiO)(8)Si8O12, R-1 and R-2 = Ph:PP(OH)-D4R) has been synthesized by silylation of D4R silicate ([Si8O12](8-)) with chloroethoxydiphenylsilane (ClSi(OEt)Ph-2) followed by subsequent hydrolysis. PP(OH)-D4R solid is air stable for at least 1 week. Ethoxymethylphenylsilylated and ethoxydimethylsilylated D4R oligomers ((RR2)-R-1(EtO)SiO)(8)Si8O12, R-1 = Me and R-2 = Ph abbreviated as MP(OEt)-D4R and R-1 and R-2 = Me as MM(OEt)-D4R) do not provide spherosilicates possessing stable silanol groups and eventually gel (MP(OEt)-D4R-G and MM(OEt)-D4R-G, respectively) as hydrolyzed solutions dry. This suggests that bulky phenyl groups effectively stabilize terminal silanols. Although the PP(OH)-D4R silanols are stable, they can be trimethylsilylated or condensed to form Si-O-Si bonds by thermal-treatment. PP(OH)-D4R on a glass substrate cross-links upon heating. The structural periodicity and distance between D4R units in the heat-treated sample are higher and longer than those of MP(OEt)-D4R-G and MM(OEt)-D4R-G due to the steric effects of the bulky Ph groups. Additionally, the silica-based gel derived from PP(OH)-D4R also possesses a higher molecularly ordered structure than that derived from a mixture of Si(OEt)(4) and Ph2Si(OEt)(2). This means that a building block approach is efficient for preparing molecularly ordered hybrid materials. The new spherosilicate possessing silanol groups will be a useful building block for preparation of various materials such as metallosilicates and mesostructured materials.

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  • Dendritic, Nanosized Building Block for Siloxane-Based Materials: A Spherosilicate Dendrimer

    Kazufumi Kawahara, Yoshiaki Hagiwara, Kazuyuki Kuroda

    CHEMISTRY-A EUROPEAN JOURNAL   17 ( 47 ) 13188 - 13196  2011年11月  [査読有り]

     概要を見る

    A spherosilicate dendrimer (DMS-1) with closely spaced reaction sites (Si-H groups) on the dendrimer surface has been synthesized by stepwise silylation of double-four-ring silicate with chlorotriethoxysilane (ClSi(OEt)(3)) and subsequently with chlorodimethylsilane (ClSiHMe2). DMS-1 consists of a maximum of 40 Si atoms in the interior frameworks and 24 reactive Si-H groups on the surface. Because DMS-1 is spherical and about 1.5 nm in diameter, it can be regarded as the smallest well-defined silica-based nanoparticle. DMS-1 also forms molecular crystals and is soluble in typical organic solvents. A molecularly ordered silica-based hybrid can be prepared by heating a cast film of DMS-1 at 180 degrees C for 5 days. The surface of DMS-1 can be modified by hydrosilylation with 1-hexadecene, triethoxyvinylsilane, and allylic-terminated tetraethylene glycol monomethyl ether. More than 20 Si-H groups out of 24 react with these reagents. The solubilities of the products depend on the modification. DMS-1 is not only a building block for nanohybrids, but also the smallest and most precisely designed siloxane-based nanoparticle.

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  • Ordered Silylation of Layered Silicate RUB-51 with Half-Sodalite Cages

    Yusuke Asakura, Yuki Matsuo, Nobuyuki Takahashi, Kazuyuki Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   84 ( 9 ) 968 - 975  2011年09月  [査読有り]

     概要を見る

    Layered silicate RUB-51 with half-sodalite cages was silylated with dichlorodimethylsilane and trichloromethylsilane. RUB-51, which possesses two confronting Si-O-/Si-OH groups on the interlayer surface, was reacted with bi/tri-functional silylating agents to induce bidentate silylation. RUB-51 silylated with dichlorodimethylsilane was delaminated through ultrasonication in cyclohexane. Layered octosilicate, which also possesses two confronting Si-O-/Si-OH groups to form a bidentate state, was reacted with the same silylating reagents. The comparison of these silylated products derived from two different layered silicates reveals that the structures of silylated interlayer surfaces are varied by the arrangement of the two Si-O-/Si-OH groups. Silylated RUB-51 possesses zigzag grooves on the layer surfaces which will be useful for silicate-based nanomaterials design.

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  • Remarkable Birefringence in a TiO2-SiO2 Composite Film with an Aligned Mesoporous Structure

    Hirokatsu Miyata, Yuta Fukushima, Kohei Okamoto, Masahiko Takahashi, Masatoshi Watanabe, Wataru Kubo, Atsushi Komoto, Shin Kitamura, Yosuke Kanno, Kazuyuki Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   133 ( 34 ) 13539 - 13544  2011年08月  [査読有り]

     概要を見る

    Mesoporous titania-silica composite films with highly aligned cylindrical pores are prepared by the sol-gel method using a substrate with structural anisotropy. The strong alignment effect of a rubbing-treated polyimide film on a substrate provides a narrow alignment distribution in the plane of the film regardless of the fast condensation rate of titania precursors. The collapse of the mesostructure upon the surfactant removal is effectively suppressed by the reinforcement of the pore walls with silica by exposing the as-deposited film to a vapor of a silicon alkoxide. The existence of a silica layer on the titania pore wall is proved from the distributions of Ti and Si estimated by the elemental analysis in high resolution electron microscopy. The obtained mesoporous titania-silica composite film exhibits a remarkable birefringence reflecting the highly anisotropic mesoporous structure and the high refractive index of titania that forms the pore wall. The Delta n value estimated from the optical retardation and the film thickness is larger than 0.06, which cannot be achieved with the conventional mesoporous silica films with uniaxially aligned mesoporous structure even though the alignment of the pores in the films is perfect. These inorganic films with mesoscopic structural anisotropy will find many applications in the field of optics as phase plates with high thermal/chemical/mechanical stabilities.

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  • Usefulness of alkoxyltitanosiloxane for the preparation of mesoporous silica containing a large amount of isolated titanium

    Kwang-Min Choi, Ryutaro Wakabayashi, Takashi Tatsumi, Toshiyuki Yokoi, Kazuyuki Kuroda

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   359 ( 1 ) 240 - 247  2011年07月  [査読有り]

     概要を見る

    Mesoporous silica containing a large amount of isolated Ti was prepared from an alkoxytitanosiloxane precursor through a hard template method. Isopropoxytris(tris-tert-butoxysiloxy)titanium (((i)PrO)Ti[O-Si(O(t)Bu)(3)](3), TS3) was synthesized and TS3 was mixed with mesoporous carbon (CMK-3), a hard template. The mixture was pyrolyzed at 180 degrees C to form a composite consisting of titanosilica and the hard template. After calcination at 600 degrees C for the removal of the carbon template, the titanium species were not transformed to anatase TiO(2), proved by DR-UV-Vis, FTIR, XPS, and XRD, while the ESR results indicated the presence of isolated Ti. The mesoporous structure was verified by SEM, TEM, and N(2) adsorption. The Si/Ti ratio of the product was consistent with that of the precursor. All the results show that the material prepared from the precursor is ordered mesoporous silica containing a large amount of isolated Ti in the frameworks. The use of well-defined alkoxytitanosiloxane precursor leads to the formation of mesoporous silica with exactly controlled composition of titanium with neither loss of Ti nor transformation to anatase. (c) 2011 Elsevier Inc. All rights reserved.

    DOI PubMed

  • Aqueous Colloidal Mesoporous Nanoparticles with Ethenylene-Bridged Silsesquioxane Frameworks

    Chihiro Urata, Hironori Yamada, Ryutaro Wakabayashi, Yuko Aoyama, Shota Hirosawa, Satoshi Arai, Shinji Takeoka, Yusuke Yamauchi, Kazuyuki Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   133 ( 21 ) 8102 - 8105  2011年06月  [査読有り]

     概要を見る

    Aqueous colloidal mesoporous nanoparticles with ethenylene-bridged silsesquioxane frameworks with a uniform diameter of similar to 20 nm were prepared from bis(triethoxysilyl)ethenylene in a basic aqueous solution containing cationic surfactants. The nanopartides, which had higher hydrolysis resistance under aqueous conditions, showed lower hemolytic activity toward bovine red blood cells than colloidal mesoporous silica nanoparticles.

    DOI PubMed

  • Enlargement of mesopores of 2-D orthorhombic KSW-2 type silica by the addition of poly(oxyethylene) alkyl ether during the mesostructural formation

    Nobuyuki Takahashi, Tatsuo Kimura, Kazuyuki Kuroda

    SOLID STATE SCIENCES   13 ( 4 ) 714 - 720  2011年04月  [査読有り]

     概要を見る

    The size of mesopores in 2-D orthorhombic KSW-2 type silica, derived from a layered silicate kanemite, can be enlarged by the addition of poly(oxyethylene) alkyl ether (C(16)EO(10) during the mesostructural transformation from a lamellar phase to a 2-D orthorhombic one. Precursors for pore-expanded KSW-2 type silica were prepared by an acid treatment of lamellar hexadecyltrimethylammonium-intercalated kanemite (C(16)TMA-kanemite) in the presence of C(16)EO(10). The acid treatment induces simultaneous reactions of (1) intercalation of C(16)EO(10), (2) deintercalation of C(16)TMA cations, and (3) mesostructural transformation into a 2-D orthorhombic phase. Depending on the concentration of C(16)EO(10), the d(11) spacing of the products after the acid treatment but before calcination varied from 4.0 to 5.4 nm and that of the calcined products varied from 3.5 nm to 4.8 nm. The method provides a precise control in a certain range of the pore size of KSW-2 type mesoporous silica. 2010 Elsevier Masson SAS. All rights reserved.

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  • TEM image simulation of mesoporous crystals for structure type identification

    Tetsu Ohsuna, Yasuhiro Sakamoto, Osamu Terasaki, Kazuyuki Kuroda

    SOLID STATE SCIENCES   13 ( 4 ) 736 - 744  2011年04月  [査読有り]

     概要を見る

    Software, MesoPoreImage, for transmission electron microscope (TEM) image simulation of mesoporous crystals was developed. MesoPoreImage provides two-dimensional (2D) projected potential distributions along any directions as well as corresponding 2D TEM images calculated from a three-dimensional (3D) density distribution of an ideal mesoporous structure. In order to adjust the contrast of simulated TEM images to that observed, a parameter representing surface roughness on the pore surface is introduced. Simulated TEM images of four typical silica mesoporous crystals, MCM-48, AMS-10, SBA-16 and SBA-6 are shown and compared with observed ones, which shows the usefulness of the software for identification of the mesoporous structure type. A procedure for the identification of structure types of mesoporous crystals by using TEM and the simulation software is fully described. (C) 2010 Elsevier Masson SAS. All rights reserved.

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  • A Rational Repeating Template Method for Synthesis of 2D Hexagonally Ordered Mesoporous Precious Metals

    Azusa Takai, Yoji Doi, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMISTRY-AN ASIAN JOURNAL   6 ( 3 ) 881 - 887  2011年03月  [査読有り]

     概要を見る

    A repeating template method is presented for the synthesis of mesoporous metals with 2D hexagonal mesostructures. First, a silica replica (i.e., silica nanorods arranged periodically) is prepared by using 2D hexagonally ordered mesoporous carbon as the template. After that, the obtained silica replica is used as the second template for the preparation of mesoporous ruthenium. After the ruthenium species are introduced into the silica replica, the ruthenium species are then reduced by a vapor-infiltration method by using the reducing agent dimethylamine borane. After the ruthenium deposition, the silica is chemically removed. Analysis by transmission and scanning electron microscopies, a nitrogen-adsorption-desorption isotherm, and small-angle X-ray scattering revealed that the mesoporous ruthenium had a 2D hexagonal mesostructure, although the mesostructural ordering is decreased compared to that of the original mesoporous carbon template. This method is widely applicable to other metal systems. By changing the metal species introduced into the silica replica, several mesoporous metals (palladium and platinum) can be synthesized. Ordered mesoporous ruthenium and palladium, which are not easily attainable by the soft-templating methods, can be prepared. This study has overcome the composition variation limitations of the soft-templating method.

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  • Synthesis of mesostructured silica from monoalkyl-substituted double five-ring units

    Atsushi Shimojima, Hideki Kuge, Kazuyuki Kuroda

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   57 ( 3 ) 263 - 268  2011年03月  [査読有り]

     概要を見る

    A mesostructured silica-based material was synthesized by self-assembly of a novel amphiphilic molecule consisting of a well-defined siloxane head with a double five-ring (D5R) structure and a hydrophobic alkyl tail. A precursor functionalized with ethoxy groups, C(22)H(45)Si(10)O(15)(OEt)(9) (1), was hydrolyzed under an acidic condition with the retention of the D5R units, leading to the formation of two-dimensional (2D) hexagonal phase by evaporation-induced self-assembly of amphiphilic hydrolyzed molecules. Solid-state (29)Si MAS NMR analysis of the resulting hybrid solid confirmed that the D5R units were cross-linked to form siloxane networks. Calcination of this hybrid solid gave mesoporous silica with high BET surface area (740 m(2) g(-1)). These results expand the design possibility of silica-based materials at both molecular- and meso-scales, leading to the bottom up synthesis of hierarchically ordered materials.

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  • One-Step Exfoliation of Kaolinites and Their Transformation into Nanoscrolls

    Yoshiyuki Kuroda, Kazuyuki Ito, Kenichi Itabashi, Kazuyuki Kuroda

    LANGMUIR   27 ( 5 ) 2028 - 2035  2011年03月  [査読有り]

     概要を見る

    Kaolinite nanoscrolls, rolled kaolinite sheets with a tubular form, were prepared by a one-step route in which intercalation of guest species and swelling with solvent proceed at the same time. A methoxy-modified kaolinite was exfoliated by the intercalation of hexadecyltrimethylammonium chloride. The formation of nanoscrolls by the one-step route proceeded only by several alkyltrimethylammonium salts and 1-hexadecyl-3-methylimidazolium chloride. Intercalation of primary amines caused the formation of nanoscrolls by a two-step route in which the intercalation and swelling proceed separately. The successful one-step route is ascribed to the relatively weak interactions between the head groups of guest species and the interlayer surface of methoxy-modified kaolinite, and the interaction is thought to allow the formation of a flexible array of interlayer guest species for swelling. The tubular structure was mostly retained after the heat treatment at 600 degrees C to form hierarchically porous aluminosilicates with amorphous frameworks. The nanoscrolls intercalated organic guests species, which are not directly intercalated into methoxy-modified kaolinite, between the scrolled layers. The formation route to nanoscrolls is quite dependent not only on the surface modification of kaolinite but also on the structure of guest species.

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  • Expansion of Intertubular Mesopores of Imogolite Nanotubes by Thermal Decomposition of an Imogolite-Poly(sodium 4-styrenesulfonate) Composite

    Yoshiyuki Kuroda, Kazuyuki Kuroda

    CHEMISTRY LETTERS   40 ( 1 ) 46 - 48  2011年01月  [査読有り]

     概要を見る

    Intertubular mesopores of imogolite nanotubes were enlarged by using poly(sodium 4-styrenesulfonate) as an expander. The polyanion was bound electrostatically on the positively charged imogolite nanotubes to form an intertwined composite, which provided expanded intertubular mesopores after heat treatment. The expanded intertubular mesopores are expected to contribute to efficient diffusion.

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  • Formation of Hierarchically Porous Hollow Spheres Composed of Dehydroxylated Imogolite and Carbonaceous Materials

    Yoshiyuki Kuroda, Kazuyuki Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   84 ( 1 ) 49 - 51  2011年01月  [査読有り]

     概要を見る

    Hierarchically porous hollow spheres composed of dehydroxylated imogolite and carbonaceous materials were formed by using polystyrene particles as templates. A large amount of polystyrene particles were removed by heat treatment at relatively low temperature, leaving a small amount of highly porous carbonaceous material and retaining micropores of imogolite nanotubes.

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  • Exfoliation of Layered Silicates through Immobilization of Imidazolium Groups

    Nobuyuki Takabashi, Hideo Hata, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   23 ( 2 ) 266 - 273  2011年01月  [査読有り]

     概要を見る

    Layered octosilicate immobilized covalently with butylimidazolium groups was fully exfoliated into monolayer nanosheets in water. The thickness of the nanosheets was 1.9 nm (atomic force microscopy (AFM)). The colloidal aggregates of the nanosheets did not show X-ray diffraction (XRD) peaks at lower angles, suggesting the absence of layer stacking. After drying of the colloidal aggregates, a sharp peak at 1.9 nm was observed. This d-value agreed well with the thickness observed by AFM. The in-plane crystal structure of octosilicate was retained after exfoliation because of the presence of the XRD peak at 0.19 nm assignable to the (400) plane of octosilicate. The interlayer surface of Bim-Oct immobilized with butylimidazolium groups is suggested to be easily hydrated, which leads to the swelling and the following exfoliation into nanosheets. The significant change of the silicate surface by the immobilization is novel, which reflects the unique property of butylimidazolium groups. A transparent and colorless film was successfully obtained by spin-coating the colloidal aggregates of nanosheets on a glass substrate: An anionic dye of Orange II was intercalated into the interlayer of restacked nanosheets in the film. The immobilization of imidazolium groups on layered silicates is innovative for the preparation of nanosheets which are designable for various applications.

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  • Preparation of mesostructured silica-micelle hybrids and their conversion to mesoporous silica modified controllably with immobilized hydrophobic blocks by using triethoxysilyl-terminated PEO-PPO-PEO triblock copolymer

    Chihiro Urata, Yasuhiro Tamura, Yusuke Yamauchi, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   21 ( 11 ) 3711 - 3717  2011年  [査読有り]

     概要を見る

    Mesostructured silica having mesopore surface functionalized with poly(ethylene oxide)(20)-b-poly(propylene oxide)(70)-b-poly(ethylene oxide)(20) (EO20PO70EO20, P123) micelles was synthesized by using triethoxysilyl-terminated P123 (TES-P123) with dual functions of templating and surface anchoring. The amount of anchored P123 was controlled by mixing TES-P123 and conventional P123 as a cotemplate and the subsequent removal of the cotemplate by extraction. All the samples show the presence of ordered mesopores after the extraction. Unexpectedly, the d-spacing and the pore size increased after the extraction when the ratio of TES-P123/(TES-P123 + P123) was over 75%, which is explained by an osmotic force caused by anchored P123 swollen with THF during the extraction. To evaluate the stability of anchored P123, ibuprofen was simultaneously incorporated into mesopores during the formation of mesostructured silica. When TES-P123 was exclusively used, the percentage of retained P123 after the extraction of IBU was higher than that found for the case of conventional P123. This approach will open a new way to stabilize assembled amphiphiles in regularly ordered siloxane frameworks.

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  • Pt nanoworms: creation of a bumpy surface on one-dimensional (1D) Pt nanowires with the assistance of surfactants embedded in mesochannels

    Azusa Takai, Hamed Ataee-Esfahani, Yoji Doi, Minekazu Fuziwara, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   47 ( 27 ) 7701 - 7703  2011年  [査読有り]

     概要を見る

    A new type of platinum nanowire with a bumpy surface "Pt nanoworm" is electrochemically synthesized in mesochannels of mesoporous silica films with the assistance of a nonionic surfactant (C(16)EO(8)).

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  • Materials design of layered silicates through covalent modification of interlayer surfaces

    Nobuyuki Takahashi, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   21 ( 38 ) 14336 - 14353  2011年  [査読有り]

     概要を見る

    Layered silicates, whose frameworks are composed of only SiO4 tetrahedra, provide many interesting properties through covalent modification of interlayer SiOH/SiO- groups. This review summarizes covalent modifications of layered silicates, such as magadiite, kanemite, kenyaite, layered octosilicate (RUB-18 or ilerite), and layered zeolitic materials (or their precursors). Interlayer silanol groups can be modified with various silylation reagents including alkyl, amino, and thiol groups. Anion exchangeable layered hybrids are obtained by immobilization of imidazolium groups, and are exfoliated into monolayer nanosheets in water. New crystalline silicate structures are obtained by precisely designed silylation of octosilicate. Silanol groups of layered silicates are esterified with some alcohols. Condensation of silanol groups in the same layer is effective for intercalation of bulky nonionic surfactants. Topotactic conversion through interlayer condensation of silanol groups leads to the formation of 3-D zeolite structures. Expansion of the pores of zeolites is achieved by pillaring through covalent modification. These covalent modifications of layered silicates make it possible to design for practical applications.

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  • Double function of tris(hydroxymethyl)aminomethane (THAM) for the preparation of colloidal silica nanospheres and the conversion to ordered mesoporous carbon

    Kwang-Min Choi, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   47 ( 39 ) 10933 - 10935  2011年  [査読有り]

     概要を見る

    Tris(hydroxymethyl)aminomethane (THAM) has been found to be an excellent catalyst for the preparation of colloidal silica nanospheres around 10 to 20 nm in size, and THAM on the surfaces of nanospheres is an efficient carbon source for the synthesis of highly ordered mesoporous carbon with controlled pore size by using closely packed nanospheres as a porogen.

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  • Practical Conversion of Chlorosilanes into Alkoxysilanes without Generating HCl

    Ryutaro Wakabayashi, Yasushi Sugiura, Toshimichi Shibue, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   50 ( 45 ) 10708 - 10711  2011年  [査読有り]

     概要を見る

    Alcohol-free: A versatile, efficient, and practical synthesis of alkoxysilanes without generation of HCl involves the reaction of chlorosilanes with unsymmetrical ethers in the presence of a Lewis acid (see scheme). The reaction proceeds through selective cleavage of C-O bonds and is superior to conventional processes. Industrially feasible reagents are used and only one by-product results. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

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  • Effect of organic additives on the formation of alkylsiloxane mesophases

    Atsushi Shimojima, Mikako Sakurai, Kazuyuki Kuroda, Tatsuya Okubo

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   350 ( 1 ) 155 - 160  2010年10月  [査読有り]

     概要を見る

    The effects of organic additives (1,3,5-trialkylbenzenes, n-alkanes, and n-alkyl alcohols) on the formation of hybrid siloxane organic mesophases from alkoxylated precursors (C(n)H(2n+1)Si(OSi(OMe)(3))(3), 1Cn, n = 6, 10, and 16) have been investigated. These precursors become amphiphilic upon hydrolysis of the alkoxy groups, thus forming two-dimensional (2D) hexagonal phase (n = 6 and 10) and lamellar phase (n = 16) by evaporation-induced self-assembly followed by polycondensation. The addition of 1,3,5-trialkylbenzenes or n-alkanes to the 1C10 system leads to swollen 2D hexagonal phases, thereby achieving pore-size expansion of the calcined samples from 2.0 nm up to 3.8 nm in diameter. The effect of these organic additives depends largely on the alkyl chain length of 1Cn; the 2D hexagonal structure (n = 6) undergoes structural disordering, while the lamellar structure (n = 16) remains unchanged. On the other hand, the addition of alkyl alcohols to the 1C10 system causes a drastic change in the mesostructure from 2D hexagonal to lamellar, which can be attributed to possible interactions between alcohol molecules and silanol groups of hydrolyzed 1C10. These results provide a facile approach to the fine structural control of nanohybrid materials assembled from single siloxane-based molecules. (C) 2010 Elsevier Inc. All rights reserved.

    DOI

  • Applied Organometallic Chemistry: Preface

    Richard M. Laine, Richard A. Vaia, Kazuyuki Kuroda, Kimihiro Matsukawa, Hirokazu Matsuda, Yoshiyuki Sugihara

    Applied Organometallic Chemistry   24 ( 8 ) 539  2010年08月  [査読有り]

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  • Lamellar self-assembly of a porphyrin derivative possessing poly(ethylene oxide) methyl ether and the formation of a silica-porphyrin hybrid with tetraethoxysilane

    Shintaro Nasu, Kazuyuki Kuroda

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   348 ( 2 ) 446 - 451  2010年08月  [査読有り]

     概要を見る

    A porphyrin derivative, possessing poly(ethylene oxide) methyl ether on the para positions of phenyl groups in the tetraphenylporphyrin, is self-assembled to form a thin film with a lamellar structure. A split of the absorption band in the visible light region of the film strongly indicates the stacking of the porphyrin rings in the film. A molecular periodicity perpendicular to the substrate, proven by in-plane XRD, suggests the perpendicular orientation of the porphyrin rings. A silica-porphyrin hybrid film with a mesostructure was prepared from the mixture of the derivative and tetraethoxysilane. The mesoscale periodicity of the hybrid was confirmed by low-angle XRD and TEM data. The presence of the grafted groups suppressed the segregation of tetraphenylporphyrin rings in the formation of the hybrids, which is in clear contrast to the separated precipitation of tetraphenylporphyrin from a mixture of underivatized tetraphenylporphyrin and hydrolyzed tetraethoxysilane. These results indicate that porphyrin derivatives can be utilized as the organic components in silica-organic hybrids if they are appropriately derivatized. (C) 2010 Published by Elsevier Inc.

    DOI PubMed

  • Synthesis of Mesoporous Carbon Using a Fullerenol-based Precursor Solution via Nanocasting with SBA-15

    Yoji Doi, Azusa Takai, Sho Makino, Logudurai Radhakrishnan, Norihiro Suzuki, Wataru Sugimoto, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMISTRY LETTERS   39 ( 7 ) 777 - 779  2010年07月  [査読有り]

     概要を見る

    Here, we demonstrate mesoporous carbons with different amounts of fullerene cage (MCF) by using a fullerenol-based precursor solution via a nanocasting method with SBA-15 mesoporous silica. The fullerene cages embedded in the frameworks are electrochemically active, showing high potential as an electrode material for an electric double-layer capacitor.

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  • Anion Exchangeable Layered Silicates Modified with Ionic Liquids on the Interlayer Surface

    Nobuyuki Takahashi, Hideo Hata, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   22 ( 11 ) 3340 - 3348  2010年06月  [査読有り]

     概要を見る

    Novel layered materials with two-dimensionally arranged anion exchangeable sites in the interlayer space were prepared by immobilization of imidazolium chloride salts (1-butyl (or 1-octyl)-3-(3-triethoxysilylpropyl)-4,5-dihydroimidazolium chloride, abbreviated as BimSi(OEt)(3)Cl or OimSi(OEt)(3)Cl, respectively) containing terminal triethoxysilyl groups onto layered octosilicate via silylation. More than 80% of SiOH/SiO(-) groups on the silicate layers were silylated and they are denoted as Bim-Oct and Oim-Oct. The cation exchangeable sites on octosilicate were stoichiometrically converted to anion exchangeable sites. The confronting arrangement of SiOH/SiO(-) groups on octosilicate is essential for this stoichiometric conversion because the silylation reagents ideally react with the surface SiOH/SiO(-) groups to form bidentate immobilization on octosilicate. The anion exchangeable capacity of the silylated materials is around 2 mmol g(-1). The affinity of these materials for Cl(-), Br(-), I(-), and NO(3-) is quite different from those of conventional anion exchangeable layered double hydroxides (LDHs). Bim-Oct is stable at pH 1.0, which is in clear contrast to the behavior of LDHs. Bim-Oct exhibits a high capacity for sorption of sulfasalazine, a bulky prodrug. The release behavior of the accommodated sulfasalazine is largely dependent on the pH values of simulated gastric and intestinal fluids, suggesting that these novel layered anion exchangers are potentially applicable to drug delivery systems.

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  • Soft-Chemical Approach of Noble Metal Nanowires Templated from Mesoporous Silica (SBA-15) through Vapor Infiltration of a Reducing Agent

    Azusa Takai, Yoji Doi, Yusuke Yamauchi, Kazuyuki Kuroda

    JOURNAL OF PHYSICAL CHEMISTRY C   114 ( 17 ) 7586 - 7593  2010年05月  [査読有り]

     概要を見る

    Noble metal (Pt, Ag, and Au) nanowires are synthesized by using mesoporous silica (SBA-15) powders as templates through vapor infiltration of a reducing agent (dimethylamine borane, DMAB) under the same reduction conditions. Because SBA-15 has micropores connecting mesochannels, Pt nanowires are connected and periodically packed, reflecting the micropores and the mesochannel arrangements in the original mesoporous silica. On the other hand, other metal (Ag and Au) nanowires are mainly unconnected. Such a difference is attributed to the relatively faster deposition rate of Ag and Au than Pt. Therefore, Ag and Au tend to grow rapidly along the mesochannels, and the metal deposition in micropores is insufficient to occur. The length of the metal nanowires is controlled by the reduction time. As a typical case, the surface plasmon resonance spectra of the Au nanowires embedded in SBA-15 change depending on the length of the nanowires. The present reduction is a soft-chemical, straightforward, and general approach, which has advantages for the synthesis of metal nanowires in large amounts.

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  • Electrochemical analysis of perpendicular mesoporous Pt electrode filled with pure water for clarifying the active region in fuel cell catalyst layers

    Satoshi Tominaka, Chia-Wen Wu, Kazuyuki Kuroda, Tetsuya Osaka

    JOURNAL OF POWER SOURCES   195 ( 8 ) 2236 - 2240  2010年04月  [査読有り]

     概要を見る

    A perpendicular mesoporous platinum film is used as a model electrode to clarify the effectiveness of catalysts inside agglomerates of fuel cell catalyst layers on the basis of experimental facts. The analysis clarifies that: (i) Pt surface even apart from Nafion ionomer phase can be electrochemically active: (ii) its response is different from that of the surface covered with ionomer; and (iii) ionic resistance in pores filled with pure water is too high (ca. 0.18 M Omega cm) for fuel cell reactions to smoothly occur. We conclude that such catalysts in pores filled with pure water are ineffective for fuel cell reactions due to the high ionic resistance, though their catalytic activity is possibly higher than that of the catalysts covered with Nafion. (C) 2009 Published by Elsevier B.V.

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  • Formation of Reactive Microporous Networks from Alkoxyvinylsilylated Siloxane Cages

    Yoshiaki Hagiwara, Atsushi Shimojima, Kazuyuki Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   83 ( 4 ) 424 - 430  2010年04月  [査読有り]

     概要を見る

    A bifunctional siloxane cage, where double four-membered ring (D4R) silicate was capped with alkoxyvinylsilyl groups, was synthesized as a novel building block for the formation of inorganic-organic microporous solids in order to show its usefulness for synthesizing silica-based nanomaterials with unique structures and properties. The nanobuilding blocks were connected to each other either by hydrolysis and condensation of alkoxysilyl groups to form Si-O-Si linkages or by hydrosilylation of vinyl groups with hydrogen-terminated D4R (H8Si8O12), which was used as a linking agent, to form Si-CH2CH2-Si linkages. Xerogel obtained by hydrosilylation showed a significant increase in the surface area upon removal of alkoxy groups by post treatment. The molecular design of bifunctionally-silylated D4R units provides a new approach to the formation of microporous networks with uniform distribution of reactive groups that allow post-modification.

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  • Tailored Electrochemical Synthesis of 2D-Hexagonal, Lamellar, and Cage-Type Mesostructured Pt Thin Films with Extralarge Periodicity

    Azusa Takai, Yusuke Yamauchi, Kazuyuki Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   132 ( 1 ) 208 - 214  2010年01月  [査読有り]

     概要を見る

    We report the synthesis of mesostructured Pt films with extralarge periodicity from lyotropic liquid crystals consisting of block copolymers (polystyrene-b-polyethylene oxide, PS-b-PEO) on Au substrates by electrochemical deposition. The Pt films with three types of (two-dimensional (2D)-hexagonal, lamellar, and cage-type) mesostructures are successfully synthesized by controlling the compositional ratio between block copolymers and Pt species in precursor solutions. The mesostructured Pt films have high electrochemically active surface areas. The bumpy mesopore surfaces, which reflect the mesopore walls consisting of connected nanoparticles, greatly contribute to the enhancement of the surface areas. The mesopore walls have single crystal domains over 400 nm(2) region proved by the lattice fringes of Pt extending over several nanoparticles.

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  • Integrated structural control of cage-type mesoporous platinum possessing both tunable large mesopores and variable surface structures by block copolymer-assisted Pt deposition in a hard-template

    Yoshiyuki Kuroda, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   46 ( 11 ) 1827 - 1829  2010年  [査読有り]

     概要を見る

    Cage-type mesoporous Pt with tunable large mesopores possessing smooth and rough pore surfaces were prepared selectively by the deposition of Pt in the absence and presence of a block copolymer in a hard-template, respectively.

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  • Interlayer modification of a layered H-octosilicate (H-RUB-18) with methanol: formation of a highly ordered organosilicate nanohybrid

    Shosuke Kiba, Tetsuro Itagaki, Teruyuki Nakato, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   20 ( 16 ) 3202 - 3210  2010年  [査読有り]

     概要を見る

    Highly ordered silicate-organic nanohybrids were prepared by the modification of interlayer silanol groups of a layered polysilicic acid (H-octosilicate, H-RUB-18) with methanol. The grafting reaction was performed in a Teflon-lined stainless steel autoclave at 120 degrees C for various reaction periods. The grafting of methoxy groups onto the interlayer surface was evidenced by the downfield chemical shifts of the methyl groups in the solid state (13)C NMR spectra and the exothermic DTA peaks with substantial weight losses due to combustion of methyl groups. The degree of modification with the methoxy groups was variable in the range between 0.42 and 0.95, depending on the reaction time. The retention of the layered silicate structure was proved by XRD and (29)Si HD/MAS NMR. The structure was also analyzed by molecular mechanics force field calculation and Rietveld analysis, indicating the expansion of the silicate plane composed of the 5(4) cage with six-membered rings in the structure. This small structural distortion, caused by repulsion between the grafted methoxy groups, resulted in transformation of the crystal system from tetragonal to monoclinic. Hydrogen molecules were sorbed into the grafted products.

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  • Nonhydrolytic Synthesis of Branched Alkoxysiloxane Oligomers Si[OSiH(OR)(2)](4) (R = Me, Et)

    Rytnaro Wakabayashi, Kazufumi Kawahara, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   49 ( 31 ) 5273 - 5277  2010年  [査読有り]

     概要を見る

    Beyond silanol: A branched siloxane oligomer bearing terminal dialkoxysilyl groups was nonhydrolytically synthesized by direct alkoxysilylation of a tetraalkoxysilane with a chlorodialkoxysilane in the presence of the Lewis acid BiCl3 (see scheme). The reaction proceeds without the formation of intermediate silanol groups, and provides a selective route for siloxane-based oligomers. (Chemical equation presented) © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

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  • Preparation of lamellar inorganic-organic hybrids from tetraethoxysilane and a coumarin derivative containing a triethoxysilyl group and photodimerization of the interlayer coumarin groups

    Shintaro Nasu, Ayako Tsuchiya, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   20 ( 32 ) 6688 - 6695  2010年  [査読有り]

     概要を見る

    Lamellar inorganic-organic hybrids were prepared as powders and films via hydrolysis and cocondensation of tetraethoxysilane (TEOS) and a coumarin derivative containing a triethoxysilyl group. The formation of lamellar structures consisting of siloxane layers and interlayer coumarin groups with ca. 4 nm periodicities, revealed by XRD and TEM, is induced by self-assembly of the oligomeric species derived from TEOS and the derivative. The UV-vis absorption spectrum of the as-synthesized hybrid film showed an absorption maximum blue-shifted from that observed for a CHCl(3) solution of the monomeric coumarin derivative, which supports the formation of a face-to-face structure of the interlayer coumarin groups. Dimerization of the coumarin groups occurred by irradiation with visible light (>310 nm). The groups in the lamellar hybrid film showed faster dimerization and the yield of dimers was higher, if compared with those in a disordered hybrid film and the neat coumarin derivative, indicating the efficient dimerization of the chromophores with a controlled arrangement. The molecular design of a coumarin derivative strongly influences the property of hybrids as well as the mesostructural formation.

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  • Tailored synthesis of mesoporous platinum replicas using double gyroid mesoporous silica (KIT-6) with different pore diameters via vapor infiltration of a reducing agent

    Yoji Doi, Azusa Takai, Yasuhiro Sakamoto, Osamu Terasaki, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   46 ( 34 ) 6365 - 6367  2010年  [査読有り]

     概要を見る

    We demonstrate facile synthesis of mesoporous Pt replicas using double gyroid mesoporous silica (KIT-6) with different pore diameters via vapor infiltration of a reducing agent. Through controlling the complementary pore size, it becomes possible to selectively deposit Pt into one side pore of the Ia (3) over bard bicontinuous structure, thereby forming a mesoporous Pt replica with relatively large mesopores (over 10 nm).

    DOI PubMed

  • Morphosynthesis of Nanostructured Gold Crystals by Utilizing Interstices in Periodically Arranged Silica Nanoparticles as a Flexible Reaction Field

    Yoshiyuki Kuroda, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   49 ( 39 ) 6993 - 6997  2010年  [査読有り]

     概要を見る

    Rigid but flexible: Gold nanoplates with highly ordered surface dimples (see picture) are deposited in the interstices of periodically arranged silica nanoparticles. The silica nanoparticles not only act as rigid templates to form dimples or mesopores, but also provide a flexible reaction field that allows anisotropic crystal growth of gold in a simultaneously formed two-dimensional nanospace. © 2010 Wiley-VCH Verlag GmbH & Co. KGaA.

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  • Alignment Control of Self-Assembled Organosiloxane Films Derived from Alkyloligosiloxane Amphiphiles

    Jenny Du, Madoka Fukushima, Shigeru Sakamoto, Mikako Sakurai, Takashi Suzuki, Atsushi Shimojima, Hirokatsu Miyata, Cathleen M. Crudden, Kazuyuki Kuroda

    LANGMUIR   25 ( 23 ) 13614 - 13618  2009年12月  [査読有り]

     概要を見る

    Transparent and continuous organosiloxane Films with macroscopically oriented mesostructures were prepared by dip-coating a substrate, on which a rubbing-treated polyimide film is formed, with hydrolyzed solutions of oligosiloxane precursors (C(n)H(2n+1)Si(OSi(OMe(3))(3)), The structure of the films depends on the alkyl chain length of the precursors such that films with two-dimensional (2D) hexagonal and lamellar structures are obtained when n = 10 and 16, respectively. In the 2D hexagonal film, the cylindrical organic moieties are aligned perpendicular to the rubbing direction in the plane of the film over the whole film thickness. Oil the other hand, the lamellar film changes its orientation with increased distance from the substrate surface. While the orientation of the lamellae at the surface of the film is parallel to the film-air interface, they are perpendicularly aligned in the vicinity of the substrate with the layer normal parallel to the rubbing direction. The observed unique orientation of the mesostructures is attributed to the anisotropic hydrophobic interactions between the alkyl chains of the hydrolyzed oligosiloxane molecules and the polymer chains of the polyimide layer oriented by the rubbing treatment.

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  • Formation of Two- and Three-Dimensional Hybrid Mesostructures from Branched Siloxane Molecules

    Shigeru Sakamoto, Atsushi Shimojima, Keiichi Miyasaka, Juanfang Ruan, Osamu Terasaki, Kazuyuki Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   131 ( 28 ) 9634 - 9635  2009年07月  [査読有り]

     概要を見る

    (Chemical Equation Presented) We report the design of a new precursor having three branching disiloxane units capable of forming 3D mesostructures with a cubic Pm-3n and its orthorhombic and tetragonal variants Cmmm and P4 2/mnm, in addition to a conventional 2D hexagonal (p6mm) mesostructure, thus creating a novel research area of mesostructural design in silica-organic nanohybrid materials. © 2009 American Chemical Society.

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  • Preparation of Mesoporous Pt-Ru Alloy Fibers with Tunable Compositions via Evaporation-Mediated Direct Templating (EDIT) Method Utilizing Porous Anodic Alumina Membranes

    Azusa Takai, Takahiro Saida, Wataru Sugimoto, Liang Wang, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   21 ( 14 ) 3414 - 3423  2009年07月  [査読有り]

     概要を見る

    Synthesis of composition-controlled mesoporous Pt-Ru alloy fibers by a dual-templating method (Yamauchi et al. J. Am. Client. Soc., 2008, 130, 5426-5427) is demonstrated using lyotropic liquid crystals (LLCs) as mesostructural direct templates and porous anodic alumina membranes (PAAMs) as morphological direct templates. The LLCs, including Pt and Ru species, were formed from diluted precursor solutions inside PAAM channels via the evaporation-mediated direct templating (EDIT) method. For all Pt-Ru compositions, the tubular mesophases in the LLCs were stacked like donuts within the PAAM channels because of the confined effect. After metal deposition by the vapor infiltration method of dimethylamineborane (DMAB) and subsequent removal of both surfactants and PAAM, mesoporous Pt-Ru fibers with various compositions were successfully prepared. Both the alloy state and the mesoporous structures were Fully characterized by high-resolution scanning electron microscopy (HR-SEM) transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopic (EDS) mapping X-ray photoelectron spectroscopy (XPS), and electrochemical techniques. The composition ratios of Pt and Ru in the fibers were tuned by controlling those of the used precursor solutions. The mesoporous structures in the fibers reflected the original LLC mesostructures; however, the ordering of the mesoporous structures gradually decreased with the increase in the Ru contents in the precursor solutions.

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  • Mesostructured silica based delivery system for a drug with a peptide as a cell-penetrating vector

    Chuanbo Gao, Isabel Izquierdo-Barba, Ikuhiko Nakase, Shiroh Futaki, Juanfang Ruan, Kazutami Sakamoto, Yasuhiro Sakamoto, Kazuyuki Kuroda, Osamu Terasaki, Shunai Che

    MICROPOROUS AND MESOPOROUS MATERIALS   122 ( 1-3 ) 201 - 207  2009年06月  [査読有り]

     概要を見る

    A drug delivery system using mesostructured silica as a reservoir has been developed for the storage and controlled release of a drug with a cell-penetrating peptide (CPP) as a vector. We use fluorescein isothiocyanate (FITC) as the drug model and octaarginine (R8) as a vector to endow the drug with cell-penetrating property. The mesostructured silica reservoir system was prepared by using a one-pot liquid-crystal templating method, which is suitable for the encapsulation of intact FITC-R8 conjugates and sustained release of drugs without hampering their properties. The hydrophobic poly(propyl oxide) (PPO) shell of the pore-filling Pluronic F127 and the electrostatic interaction between R8 and siloxide ions on the pore walls act as the diffusion-limiting factors of the FITC-R8 conjugate. A sigmoidal in vitro release of FITC-R8 from mesostructured silica into phosphate buffered saline (PBS, pH 7.4) was observed and the typical release duration was 5 days at 37 degrees C. Release from the reservoir yielded significant elongation in duration of the FITC signals in DUI 45 cells by confocal microscopic analysis, compared with a single administration of FITC-R8. (C) 2009 Elsevier Inc. All rights reserved.

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  • Self-Assembled Double Ladder Structure Formed Inside Carbon Nanotubes by Encapsulation of H8Si8O12

    Zheng Liu, Soon-Kil Joung, Toshiya Okazaki, Kazu Suenaga, Yoshiaki Hagiwara, Tetsu Ohsuna, Kazuyuki Kuroda, Sumio Iijima

    ACS NANO   3 ( 5 ) 1160 - 1166  2009年05月  [査読有り]

     概要を見る

    Unique low-dimensional SiO2-based nanomaterials can be encapsulated and synthesized inside the nanometer-scale one-dimensional internal spaces of carbon nanotubes (CNTs). In this study, various single-walled CNTs (SWNTs) and double-walled CNTs (DWNTs) having different diameters are used as containers for cubic octameric H8Si8O12 molecules. High-resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FT-IR) spectroscopy, and Raman spectroscopy observations revealed that, depending on the diameter of the CNTs, two types of structures are formed inside the SWNTs and DWNTs: In the case of those CNTs having inner diameters ranging from 1.2 to 1.4 nm, a new ordered self-assembled structure composed of H8Si4nO8n-4 molecules was formed through the transformation of H8Si8O12; however, in the case of CNTs having inner diameters larger than 1.7 nm, a disordered structure was formed. This behavior may indicate that strong interactions occur between the CNTs and the encapsulated HSi4nO8n-4 molecules.

    DOI PubMed

  • Color Tuning of an Acidic Blue Dye by Intercalation into the Basic Interlayer Galleries of a Poly(allylamine)/Synthetic Fluoromica Nanocomposite

    Hideo Hata, Thomas E. Mallouk, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   21 ( 6 ) 985 - 993  2009年03月  [査読有り]

     概要を見る

    The intercalation of an acidic blue dye, Brilliant Blue FCF, into poly(allylamine) (PAA)/synthetic fluoromica (Na-TSM) was investigated as a function of the reaction pH (1.5-12.0) and the loading of the polyelectrolyte and acidic dye. Surprisingly, the colored solids so obtained show a variety of colors from the original blue to yellow through green with only a slight increase in the reaction pH. At low and neutral pH (1.5-9.5), the acidic blue dye molecules were adsorbed/intercalated on/in PAA/Na-TSM mainly through electrostatic interactions between protonated amine groups on the PAA chains and sulfonate groups of the dye, resulting in the original blue color. UV-visible spectroscopic data hint that the adsorbed/intercalated dye molecules were aggregated. The color shifted to blue-green at pH 10.0 and finally to yellow at pH 12.0. At high pH, the PAA layers have lower charge density and the dye is well-dispersed within the interlayer galleries. The fraction of neutral primary amine groups increases with increasing reaction pH, and interaction of the neutral amine groups to the dye becomes the dominant driving force for intercalation. On the basis of these intercalation results at different pH and some control experiments, the pH-dependent color change of the intercalated dye appears to be caused by inhibition of the intramolecular interaction between N(+) in the dye conjugated system and a free sulfonate group.

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  • Ordered Mesoporous Silica Derived from Layered Silicates

    Tatsuo Kimura, Kazuyuki Kuroda

    ADVANCED FUNCTIONAL MATERIALS   19 ( 4 ) 511 - 527  2009年02月  [査読有り]

     概要を見る

    Here, the development of ordered mesoporous silica prepared of layered silicates with organciammonium surfactants is reviewed. The specific features of mesoporous silica are discussed with relation to the probable formation mechanisms. The recent understanding of the unusual structural changes from the 2D structure to periodic 3D mesostructures is presented. The formation of mesophase silicates from layer silicates with single silicate sheets depends on combined factors including the reactivity of layered silicates, the presence of layered intermediates, the variation of the silicate sheets, and the assemblies of surfactant molecules in the interlayer spaces. FSM-16-type (p6mm) mesoporous silica is formed via layered intermediates composed of fragmented silicate sheets and alkyltrimethylammonium (C(n)TMA) cations. KSW-2-type (c2mm) mesoporous silica can be prepared through the bending of the individual silicate sheets with intralayer and interlayer condensation. Although the structure of the silicate sheets changes during the reactions with C(n)TMA cations in a complex manner, the structural units caused by kanemite in the frameworks are retained. Recent development of the structural design in the silicate framework is very important for obtaining KSW-2-based mesoporous silica with molecularly ordered frameworks. The structural units originating from layered silicates are chemically designed and structurally stabilized by direct silylation of as-synthesized KSW-2. Some proposed applications using these mesoporous silica are also summarized with some remarks on the uniqueness of the use of layered silicates by comparison with MCM-type mesoporous silica.

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  • Dialysis process for the removal of surfactants to form colloidal mesoporous silica nanoparticles

    Chihiro Urata, Yuko Aoyama, Akihisa Tonegawa, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   ( 34 ) 5094 - 5096  2009年  [査読有り]

     概要を見る

    Colloidal mesoporous silica nanoparticles less than 20 nm in diameter are prepared by dialysis; this simple surfactant removal route can avoid aggregation by sedimentation-redispersion and remove cationic surfactants while retaining the original colloidal state, which is applicable to the preparation of primary nanoparticles carrying a functional organic substance.

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  • QCM Study of Superfluid Transition in He-4 Films Adsorbed in SBA-15

    K. Matsuda, M. Hieda, T. Matsushita, T. Suzuki, K. Kuroda, N. Wada

    25TH INTERNATIONAL CONFERENCE ON LOW TEMPERATURE PHYSICS (LT25), PART 3   150  2009年  [査読有り]

     概要を見る

    A quartz crystal microbalance (QCM) is a useful tool to study the superfluidity of He-4 films at very high frequencies. Our recent efforts to fabricate mesoporous silica films onto QCM have enabled us to study the noble superfluidity adsorbed in nanopores. In this paper we report results of QCM measurements for the superfluid He-4 films in SBA-15 with one-dimensional nanopores 4.1 nm in diameter and similar to 1 mu m in length. From the 4 He pressure isotherm at 4.2 K, a uniform layer is formed in the nanopores up to the coverage of 48 mu mol/m(2), corresponding to similar to 2.5 layers. The superfluid response is measured at 12 MHz for various coverages in the temperature range of 0.1 - 1.5 K. Above the onset coverage of similar to 23 mu mol/m(2), we observed a frequency shift accompanied by a dissipation peak due to the superfluid Kosterlitz-Thouless (KT) transition.

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  • Facile patterning of assembled silica nanoparticles with a closely packed arrangement through guided growth

    Yusuke Yamauchi, Junko Imasu, Yoshiyuki Kuroda, Kazuyuki Kuroda, Yoshio Sakka

    JOURNAL OF MATERIALS CHEMISTRY   19 ( 14 ) 1964 - 1967  2009年  [査読有り]

     概要を見る

    A facile patterning of assembled silica nanoparticles with a closely packed arrangement is demonstrated over a wide area through a guided growth approach utilizing a micro-mold.

    DOI

  • Properties of metal species in square-shape mesopores of KSW-2-based silica

    Tatsuo Kimura, Shengjun Huang, Atsushi Fukuoka, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   19 ( 23 ) 3859 - 3866  2009年  [査読有り]

     概要を見る

    Properties arising from 2-D orthorhombic mesoporous silica (KSW-2) were investigated for each structural feature: (1) periodicity in silicate framework and (2) square-shape mesopore. Titanium species were grafted onto the periodic silica walls of KSW-2-based mesoporous silica through silylation with octylmethyldichlorosilane in the presence of organotitanium compounds with cyclopentadienyl ligands. The surface TiO(4) units formed after calcination at 550 degrees C showed a higher activity in the oxidation of cyclohexene with peroxides than those onto FSM-16 and MCM-41 grafted in the same manner, indicating that (1) the periodicity in the framework influenced the catalytic activity due to the heteroatoms fixed at the silicate surfaces. The synthesis of metallic Pt species inside square-shape mesopores of KSW-2-based silica was conducted by reduction of impregnated H(2)PtCl(6). Considering the morphology of metallic Pt species formed through wet H(2) and UV reduction, it is considered that (2) the square-shape mesopore is useful for suppressing the sintering of metallic Pt species.

    DOI

  • Facile formation of single crystalline Pt nanowires on a substrate utilising lyotropic liquid crystals consisting of cationic surfactants

    Azusa Takai, Yusuke Yamauchi, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   19 ( 24 ) 4205 - 4210  2009年  [査読有り]

     概要を見る

    Single crystalline Pt nanowires about 2 nm in diameter with high-aspect ratios are successfully formed over the entire area of glass substrates by utilising lyotropic liquid crystals (LLC) containing cationic surfactants and Pt species. After the LLC films are coated on the substrates by spin-coating, the Pt species are reduced in the presence of the LLC films with an aqueous solution of sodium borohydride. Each Pt nanowire, which is well adhered to the substrate surface, is single crystalline because the nanowires are deposited in LLC films consisting of cationic surfactants acting as a capping agent. In this article, we propose a new role for LLC coated on substrates that provides a reaction field near the surface of substrates and contributes to the anisotropic growth of Pt nanowires.

    DOI

  • Ferromagnetic Mesostructured Alloys: Design of Ordered Mesostructured Alloys with Multicomponent Metals from Lyotropic Liquid Crystals

    Yusuke Yamauchi, Masaki Komatsu, Minekazu Fuziwara, Yoshihiro Nemoto, Keisuke Sato, Tokihiko Yokoshima, Hiroaki Sukegawa, Kouichiro Inomata, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   48 ( 42 ) 7792 - 7797  2009年  [査読有り]

     概要を見る

    Magnets made to order: Highly ordered multicomponent mesostructured alloys with controllable compositions have been synthesized [see TEM image and electron diffraction patterns (inset)]. The saturation magnetization of the alloys can be controlled by changing the ratio of metal components. New functions that are not found in a single metal system can be realized by alloying, thus opening up a range of new magnetic applications for these materials. © 2009 Wiley-VCH Verlag GmbH & Co. KGaA.

    DOI

  • Exploration of a Standing Mesochannel System with Antimatter/Matter Atomic Probes

    Hiroyuki K. M. Tanaka, Yusuke Yamauchi, Toshikazu Kurihara, Yoshio Sakka, Kazuyuki Kuroda, Allen P. Mills

    ADVANCED MATERIALS   20 ( 24 ) 4728 - +  2008年12月  [査読有り]

     概要を見る

    Positronium, a system consisting of an electron and its antimatter, a positron, offers a new technique to explore vertical accessibility and connectivity. Here, we show how this technique can be used to map out the vertical profile of mesoporous silica channel systems by comparing a standing (perpendicular to the substrate) 2D hexagonal with a lying (parallel to the substrate) 2D hexagonal mesoporous film.

    DOI

  • Magnetically induced orientation of mesochannels inside porous anodic alumina membranes under ultra high magnetic field of 30 T: Confirmation by TEM

    Yusuke Yamauchi, Atsushi Sugiyama, Makoto Sawada, Masaki Komatsu, Azusa Takai, Chihiro Urata, Noriyuki Hirota, Yoshio Sakka, Kazuyuki Kuroda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   116 ( 1359 ) 1244 - 1248  2008年11月  [査読有り]

     概要を見る

    Mesoporous silica rods were prepared inside the channels of porous anodic alumina membranes (PAAMs) by a solvent evaporation method using a precursor solution containing P123 block copolymers. The orientation of the mesochannels within the PAAM channels could be controlled by applying high magnetic field processing under 30 T. When the magnetic field was applied parallel to the PAAM channels, mesochannels were successfully induced parallel along the magnetic direction. Such magnetically induced mesochannels were directly confirmed by TEM observation. (C) 2008 The Ceramic Society of Japan. All rights reserved.

    DOI

  • Self-Assembly of Amphiphilic Alkyloligosiloxanes within Cylindrically and Spherically Confined Spaces

    Mikako Sakurai, Atsushi Shimojima, Yusuke Yamauchi, Kazuyuki Kuroda

    LANGMUIR   24 ( 22 ) 13121 - 13126  2008年11月  [査読有り]

     概要を見る

    The self-assembly of amphiphilic alkyloligosiloxane molecules within cylindrically and spherically confined spaces has been investigated. Hydrolyzed solutions of the precursors consisting of an alkylsiloxane core and three branching trimethoxysilyl groups (CnH2n+1Si(OSi(OMe)(3))(3), n = 10 and 16) were impregnated into the cylindrical pores of porous anodic alumina membranes (PAAMs), leading to the formation of rod- and tubelike hybrids. A two-dimensional (2D) hexagonal mesostructure with a circular orientation and a lamellar mesostructure with a multitubular orientation were confirmed for n = 10 and 16, respectively. The pore diameters of PAAMs ranging from 30 to 400 nm did not significantly affect the mesostructures of the hybrids. The self-assembly in the spherical droplets was also performed by spray-drying of the hydrolyzed solutions. At high temperature, vesicular lamellar mesostructures were formed, independent of the alkyl chain length of the precursors (n = 10 or 16). Spherical hybrids with a core-shell structure (a 2D hexagonal core and a lamellar shell) were also prepared by lowering the drying temperature in the case of it = 10. These are the first findings on the confined assembly of single siloxane-based amphiphiles that will lead to the fabrication of novel hierarchically ordered hybrid materials having Si-C covalent bonds at the interfaces.

    DOI

  • Size- and Shape-Controlled Conversion of Tungstate-Based Inorganic-Organic Hybrid Belts to WO3 Nanoplates with High Specific Surface Areas

    Deliang Chen, Lian Gao, Atsuo Yasumori, Kazuyuki Kuroda, Yoshiyuki Sugahara

    SMALL   4 ( 10 ) 1813 - 1822  2008年10月  [査読有り]

     概要を見る

    Two-dimensional monoclinic WO3 nanoplates with high specific surface areas are synthesized through a novel conversion process using tungstate-based inorganic-organic hybrid micro/nanobelts as precursors. The process developed involves a topochemical transformation of tungstate-based inorganic-organic hybrid belts into WO,3 nanoplates via an intermediate product of H2WO4 nanoplates, utilizing the similarity of the W-O octahedral layers in both H2WO4 and WO3. The as-obtained WO3 nanoplates show a single-crystalline nanostructure with the smallest side along the [001] direction. The WO3 nanoplates are 200-500 nm x 200-500 nm x 10-30 nm in size, and their specific surface areas are up to 180 m(2) g(-1). Photocatalytic measurements of visible-light-driven oxidation of water for O-2 generation in the presence of Ag+ ions indicate that the activity of the as-obtained WO3 nanoplates is one order of magnitude higher than that Of commercially available WO3 powders.

    DOI PubMed

  • Layer-by-layer assembly of imogolite nanotubes and polyelectrolytes into core-shell particles and their conversion to hierarchically porous spheres

    Yoshiyuki Kuroda, Kazuyuki Kuroda

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   9 ( 2 )  2008年06月  [査読有り]

     概要を見る

    Core-shell particles were prepared by the layer-by-layer (LbL) assembly of imogolite (IMO) nanotubes and poly( sodium 4-styrenesulfonate) (PSS) on polystyrene particles ( diameter: 800 nm) coated preliminarily with poly(diallyldimethylammonium chloride) (PDDA). PSS and imogolite were alternately adsorbed on the particles to form core-shell particles with one to three bilayers of PSS/IMO. Macroporous hollow spheres were formed by removing polystyrene cores via heat treatment or extraction when the number of bilayers was 2 or 3. The sample formed by extraction (the number of bilayer was 3) showed only macroporosity and PSS remained in the shell, whereas the heat-treated sample showed hierarchical micro- and macroporosities. When the diameter of polystyrene particles decreased from 800 nm to 300 or 100 nm, hollow spheres were deformed because of the increase in the relative length of imogolite nanotubes against the size of polystyrene particles. Imogolite is a promising building block of hierarchically porous materials with core-shell morphologies using LbL assembly.

    DOI

  • Controlled synthesis of nanostructured silica-based materials from designed alkoxysilanes

    Atsushi Shimojima, Kazuyuki Kuroda

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   46 ( 3 ) 307 - 311  2008年06月  [査読有り]

     概要を見る

    Recent progress in the synthesis of nanostructured silica-based materials through the self-assembly process using well-designed alkoxysilane precursors is presented. Alkoxysilanes with covalently attached hydrophobic organic tails become amphiphilic when hydrolyzed to form silanol groups, leading to the formation of various mesostructures upon evaporation of solvents. The precursors having large oligosiloxane heads are particularly important because of their ability to form cylindrical assemblies, providing a direct pathway to ordered porous silica by removal of the organic groups. Our recent research includes (i) templated-synthesis of hierarchically ordered structures and (ii) design of molecules having chemically cleavable bonds to generate pores without calcination.

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  • Fabrication of hierarchically porous spherical particles by assembling mesoporous silica nanoparticles via spray drying

    Chihiro Urata, Yusuke Yamauchi, Yuko Aoyama, Junko Imasu, Shin-ichi Todoroki, Yoshio Sakka, Satoru Inoue, Kazuyuki Kuroda

    JOURNAL OF NANOSCIENCE AND NANOTECHNOLOGY   8 ( 6 ) 3101 - 3105  2008年06月  [査読有り]

     概要を見る

    A new type of hierarchically porous materials is fabricated by assembling mesoporous nanoparticles via spray drying. Well-dispersed mesostructured silica nanoparticles (MSN), whose particle size distribution was narrow in the range of 20 nm and 50 nm, were prepared by a thermal deposition method. By spray drying a MSN suspension, MSN were assembled into spherical secondary particles. After calcination, the spherical particles have two types of mesopores, mesopores of 3 nm in size inside of calcined MSN and larger inter-nanoparticle mesopores of about 15-20 nm. This hierarchical pore system should provide nanospaces for efficient mass transport of guest species with different sizes.

    DOI

  • Pt fibers with stacked donut-like mesospace by assembling Pt nanoparticles: Guided deposition in physically confined self-assembly of surfactants

    Yusuke Yamauchi, Azusa Takai, Tomota Nagaura, Satoru Inoue, Kazuyuki Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   130 ( 16 ) 5426 - +  2008年04月  [査読有り]

     概要を見る

    A stack donut-like mesospace is successfully introduced into Pt fibers by assembling Pt nanoparticles with uniform particle size, by utilizing the guided deposition of Pt nanoparticles in preferentially oriented liquid crystals. We clearly demonstrate that the collaboration of both LLC templating by electrochemical processes and hard templating utilizing a confined effect can lead to the genesis of new nanostructured metals. Such a unique metal-based nanoarchitecture enhances the surface area and enables the high-mass transportation of guest species. Preferentially oriented mesochannels should contribute significantly to the fine control and transport of electronic carriers through metal fibers.

    DOI PubMed

  • Cycle and rate properties of mesoporous tin anode for lithium ion secondary batteries

    Hiroki Nara, Yoshiki Fukuhara, Azusa Takai, Masaki Komatsu, Hitomi Mukaibo, Yusuke Yamauchi, Toshiyuki Momma, Kazuyuki Kuroda, Tetsuya Osaka

    CHEMISTRY LETTERS   37 ( 2 ) 142 - 143  2008年02月  [査読有り]

     概要を見る

    A mesoporous Sn anode was electrodeposited in the presence of lyotropic liquid crystals made of nonionic surfactants. The introduction of mesoporous structure was effective for the accommodation of volume change of Sn during charge and discharge cycling of Li ions. The discharge capacity of the mesoporous Sn anode at 1 C rate was as high as 425 mA h g(-1) at the 100th cycle, and that was as high as 320 mA It g(-1) at the 100th cycle even though at 5 degrees C rate.

    DOI

  • Silica films having zigzag mesoporous structures with fixed kink angles

    Hirokatsu Miyata, Takashi Suzuki, Masatoshi Watanabe, Takashi Noma, Kazuhiro Takada, Taihei Mukaide, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   20 ( 3 ) 1082 - 1089  2008年02月  [査読有り]

     概要を見る

    Mesoporous silica films with a highly controlled unique zigzag porous structure are prepared on a rubbing-treated polyimide film. The honeycomb-packed tubular pores in the films have two distinct inplane alignment directions with respect to the rubbing direction; that is, the films have an in-plane zigzag mesoporous structure with a fixed kink angle. The kink angle is controllable by the molar ratio of tetraethoxysilane as a silica source to surfactant in the reactant solution, and the increase of the ratio results in larger kink angles. The zigzag structure is found to be formed through the formation of an initial immature mesostructured film with uniaxially aligned rodlike surfactant assemblies. It is highly probable that the observed in-plane bending of the pores is caused by the translational shift of the positions of the adsorbed surfactant molecules along the polyimide chains on the surface and that the shift is caused by the steric effects between the adjacent hydrophilic components consisting of surfactant head groups and silica oligomers. The present results show that a unique nanoscale structure, which can hardly be obtained through a reaction under homogeneous conditions, can be formed under the heterogeneous conditions in which the reaction takes place within a restricted environment.

    DOI

  • Vapor infiltration of a reducing agent for facile synthesis of mesoporous Pt and Pt-based alloys and its application for the preparation of mesoporous Pt microrods in anodic porous membranes

    Yusuke Yamauchi, Azusa Takai, Masaki Komatsu, Makoto Sawada, Tetsu Ohsuna, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   20 ( 3 ) 1004 - 1011  2008年02月  [査読有り]

     概要を見る

    Highly ordered mesoporous Pt and Pt-based alloy (Pt-Ru and Pt-Ni) microparticles were deposited from lyotropic liquid crystal (LLC) films containing corresponding metal species via vapor infiltration of a reducing agent of dimethylaminoborane (DMAB). The LLC films with 2D hexagonal symmetry were prepared on flat substrates from diluted surfactant solutions including water, nonionic surfactant, ethanol, and metal species by drop-coating. Low-angle XRD measurements and TEM observations proved that the deposited Pt and Pt-based alloy microparticles have 2D hexagonally ordered mesoporous structures. Moreover, EDS mapping of mesoporous Pt-Ru microparticles indicated that the constituent metals are well-distributed within the mesopore walls. Moreover, we effectively utilized the method to fabricate mesoporous Pt microrods with 100 nm in diameter by using a porous anodic alumina membrane (PAAM) as a hard template. The Pt microrods possess a highly porous nanostructure. Our method utilizing vapor infiltration of a reducing agent, unlike conventional electrochemical and chemical deposition methods, allows the facile preparation of mesoporous. metal microparticles and microrods and should be widely applicable to the deposition of various metals and multicomponent alloys.

    DOI

  • Alkoxysilylated-derivatives of double-four-ring silicate as novel building blocks of silica-based materials

    Yoshiaki Hagiwara, Atsushi Shimojima, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   20 ( 3 ) 1147 - 1153  2008年02月  [査読有り]

     概要を見る

    Novel oligomeric alkoxysilanes consisting of double-four-ring (D4R) units functionalized with mono-, di-, and trialkoxysilyl groups (designated as 1, 2, and 3, respectively) were designed as nanobuilding blocks for synthesizing silica-based nanomaterials. Hydrolysis and polycondensation of these oligomers were performed under acidic conditions. The gelation occurred much faster than monomeric, dimeric, and cubic octameric alkoxysilanes, which should depend on both molecular size and siloxane structures. Structural analyses of the xerogels derived from 1-3 strongly suggested that the D4R units are at least partly retained in their frameworks. The number of alkoxy groups had a large effect on their porosities: the xerogel derived from 2 was a microporous solid with the BET surface area of 600 m(2) g(-1), whereas 1- and 3-derived xerogels had very low BET surface areas. Furthermore, mesostructured silica films were successfully synthesized froth 2 and 3 by using amphiphilic triblock copolymer surfactant as a structure-directing agent. Such an approach will lead to the construction of molecularly designed siloxane networks.

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  • Platinum thin film consisting of well-aligned nanowires and its optical behavior

    Takashi Suzuki, Hirokatsu Miyata, Takashi Noma, Kazuyuki Kuroda

    JOURNAL OF PHYSICAL CHEMISTRY C   112 ( 6 ) 1831 - 1836  2008年02月  [査読有り]

     概要を見る

    A nanostructured film composed of interconnecting aligned platinum nanowires is prepared by electrodeposition using a hard template of mesoporous silica film with uniaxially aligned mesochannels formed on a conductive substrate. Platinum is introduced into the mesopores through micropores, connecting adjacent mesopores, without influencing the mesoporous structure. The alignment of the nanowires is retained to some extent after the removal of the silica template, leading to the formation of a film with aligned platinum nanowires, although the structural regularity is largely degraded. Irrespective of the presence of the silica template, the obtained films show distinct macroscopic optical anisotropy in the visible region, reflecting the anisotropic localized surface plasmon resonance arising from individual nanowire, despite its interconnected structure. The aligned structure enables the observation of such an axis-dependent optical property in a macroscopic scale. This versatile replication method can be extended to the preparation of aligned nanowire assemblies with various compositions.

    DOI

  • Design of molecularly ordered framework of mesoporous silica with squared one-dimensional channels

    Tatsuo Kimura, Hiroaki Tamura, Masato Tezuka, Dai Mochizuki, Tetsuro Shigeno, Tetsu Ohsuna, Kazuyuki Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   130 ( 1 ) 201 - 209  2008年01月  [査読有り]

     概要を見る

    Mesoporous silica with squared one-dimensional channels (KSW-2-type mesoporous silica), possessing a molecularly ordered framework arising from a starting layered polysilicate kanemite, was obtained through silylation of a surfactant (hexadecyltrimethylammonium, C(16)TMA)-containing mesostructured precursor with octoxytrichlorosilane (C(8)H(17)OSiCl(3)) and octylmethyldichlorosilane (C(8)H(17)(CH(3))SiCl(2))The presence of the molecular ordering in the silicate framework was confirmed by XRD and TEM. Octoxy groups grafted on KSW-2 can be eliminated by subsequent hydrolysis under very mild condition, and pure mesoporous silica was obtained with the retention of the kanemite-based framework. The framework is structurally stabilized by the attachment of additional SiO(4) units to the framework, and the mesostructural ordering hardly changed under the presence of water vapor. A large number of silanol groups remained at the mesopore surfaces because C(16)TMA ions and octoxy groups can be removed without calcination. Octylmethylsilyl groups are regularly arranged at the mesopore surface due to the molecular ordering in the silicate framework. The molecularly ordered structural periodicity originating from kanemite is retained even after calcination at 550 degrees C, while that in the precursor without silylation disappeared. The synthetic strategy is quite useful for the design of the silicate framework of mesostructured and mesoporous materials with and without surface functional organic groups.

    DOI PubMed

  • Stable silanetriols that contain tert-alkoxy groups: Versatile precursors of siloxane-based nanomaterials

    Jumpei Suzuki, Atsushi Shimojima, Yasuhiro Fujimoto, Kazuyuki Kuroda

    CHEMISTRY-A EUROPEAN JOURNAL   14 ( 3 ) 973 - 980  2008年  [査読有り]

     概要を見る

    Novel tert-alkoxysilanetriols (ROSi(OH)(3), R=adamantyl and 3-ethyl-3-pentyl) have been prepared from the corresponding tert-alkoxytrichlorosilanes and successfully used as molecular building blocks to produce ordered siloxane-based nanomaterials. Controlled hydrolysis of the alkoxytrichlorosilanes led to the formation of crystalline powders of alkoxysilanetriols that were stable under ambient conditions. Solid-state polycondensation of the alkoxysilanetriols occurred upon heating, which led to the formation of ordered silica-organic nanocomposites with laminated morphologies. On the other hand, silylation of the tert-alkoxysilanetriols with chlorotrimethoxysilane enabled us to synthesize well-defined oligomeric alkoxysilanes (ROSi[OSi(OMe)(3)](3)). Hydrolysis and polycondensation of these oligomers followed by acid treatment gave microporous silica with narrow pore size distributions. Thus, tert-alkoxy groups serve not only as protecting groups of siloxane species to regulate hydrolysis and polycondensation, but also as templates to generate micropores thereby providing unique synthetic pathways for the design of ordered silica-based materials.

    DOI PubMed

  • Oligomeric alkoxysilanes with cagelike hybrids as cores: Designed precursors of nanohybrid materials

    Hideki Kuge, Yoshiaki Hagiwara, Atsushi Shimojima, Kazuyuki Kuroda

    CHEMISTRY-AN ASIAN JOURNAL   3 ( 3 ) 600 - 606  2008年  [査読有り]

     概要を見る

    Well-defined alkoxysilane oligomers containing a cagelike carbosiloxane core were synthesized and used as novel building blocks for the formation of siloxane-based hybrid networks. These oligomers were synthesized from the cagelike trimer derived from bis(triethoxysilyl)methane by silylation with mono-, di-, and triethoxy-chlorosilanes ((EtO)(n)Me3-n,SiCl, n=1, 2, and 3). Hybrid xerogels were prepared by hydrolysis and polycondensation of these oligomers under acidic conditions. The structures of the products varied depending on the number of alkoxy groups (n). When n=2 and 3, microporous xerogels (BET surface areas of 820 and 510 m(2) g(-1), respectively) were obtained, whereas a nonporous xerogel was obtained when n=1. Si-29 NMR spectroscopic analysis suggested that partial rearrangement of the siloxane networks, which accompanied the cleavage of the Si-O-Si linkages, occurred during the polycondensation processes. By using an amphiphilic triblock copolymer surfactant as a structure-directing agent, hybrid thin films with a 2D hexagonal mesostructure were obtained when n = 2 and 3. These results provide important insight into the rational synthesis of molecularly designed hybrid materials by sol-gel chemistry.

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  • Phenylene-bridged mesoporous organosilica films with uniaxially aligned mesochannels

    Takashi Suzuki, Hirokatsu Miyata, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   18 ( 11 ) 1239 - 1244  2008年  [査読有り]

     概要を見る

    The alignment of mesochannels in a phenylene-bridged mesoporous organosilica film is successfully controlled by using a substrate with a rubbing-treated polyimide film. The films are prepared by two different procedures: the hydrothermal deposition process and the so-called evaporation-induced self-assembly process. The narrow alignment distribution of mesochannels is achieved by the interfacial hydrophobic interactions between alkyl chains of surfactant and the elongated polymer chains of rubbing-treated polyimide. The molecular-scale ordering of the framework in the films is low, unlike those in mesoporous organosilica powders and films prepared under basic conditions, though the thickness of the pore walls is comparable to the molecular size. The emission behaviour in the ultraviolet region, which is sensitive to inter-phenylene interactions, is influenced by synthesis and thermal treatment temperatures, irrespective of the preparative methods. The changes in the spectra indicate that the major emissive species changes from the excited monomer to the excimer with the increase of temperature. These organic-inorganic hybrid films will find various applications by combining functionalities of organic and inorganic moieties and highly controlled nanospaces.

    DOI

  • Rational design of mesoporous metals and related nanomaterials by a soft-template approach

    Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMISTRY-AN ASIAN JOURNAL   3 ( 4 ) 664 - 676  2008年  [査読有り]

     概要を見る

    We review recent developments in the preparation of mesoporous metals and related metal-based nanomaterials. Among the many types of mesoporous materials, mesoporous metals hold promise for a wide range of potential applications, such as in electronic devices, magnetic recording media, and metal catalysts, owing to their metallic frameworks. Mesoporous metals with highly ordered networks and narrow pore-size distributions have traditionally been produced by using mesoporous silica as a hard template. This method involves the formation of an original template followed by deposition of metals within the mesopores and subsequent removal of the template. Another synthetic method is the direct-template approach from lyotropic liquid crystals (LLCs) made of nonionic surfactants at high concentrations. Direct-template synthesis creates a novel avenue for the production of mesoporous metals as well as related metal-based nanomaterials. Many mesoporous metals have been prepared by the chemical or electrochemical reduction of metal salts dissolved in aqueous LLC domains. As a soft template, LLCs are more versatile and therefore more advantageous than hard templates. It is possible to produce various nanostructures (e.g., lamellar, 2D hexagonal (p6mm), and 3D cubic (Ia (3) over bard)), nanoparticles, and nanotubes simply by controlling the composition of the reaction bath.

    DOI PubMed

  • Perpendicular mesoporous Pt thin films: electrodeposition from titania nanopillars and their electrochemical properties

    Satoshi Tominaka, Chia-Wen Wu, Toshiyuki Momma, Kazuyuki Kuroda, Tetsuya Osaka

    CHEMICAL COMMUNICATIONS   ( 25 ) 2888 - 2890  2008年  [査読有り]

     概要を見る

    A perpendicular mesoporous platinum electrode with a. at surface is successfully synthesized by electrodeposition using titania nanopillars as template, and the electrochemical studies indicate that this material is a promising catalytic electrode for fuel cells because of its high surface area and perpendicular nanopores.

    DOI

  • Facile unidirectional alignment of mesochannels in a mesoporous silica film on a freshly cleaved mica surface

    Takashi Suzuki, Yosuke Kanno, Yuji Morioka, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   ( 28 ) 3284 - 3286  2008年  [査読有り]

     概要を見る

    The alignment of mesochannels in a mesoporous silica film on a freshly cleaved mica surface, prepared by an evaporation-induced self-assembly process, is unexpectedly found to be unidirectional with the narrowest directional distribution.

    DOI

  • Mesoporous platinum with giant mesocages templated from lyotropic liquid crystals consisting of diblock copolymers

    Yusuke Yamauchi, Atsushi Sugiyama, Ryoichi Morimoto, Azusa Takai, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   47 ( 29 ) 5371 - 5373  2008年  [査読有り]

     概要を見る

    Giant metal cages: Mesoporous Pt particles, with mesocages connected closely in three dimensions (see picture), are prepared by an electrodeposition process through soft templating from lyotropic liquid crystals of diblock copolymers. The size of the mesocages is the largest (about 15 nm) reported in mesoporous metals. The method can be extended to other metals and mesostructures, and the mesopores can be controlled over a range of pore sizes. (Figure Presented) © 2008 Wiley-VCH Verlag GmbH & Co. KGaA.

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  • Stepwise silylation of double-four-ring (D4R) silicate into a novel spherical siloxane with a defined architecture

    Kazufumi Kawahara, Yoshiaki Hagiwara, Atsushi Shimojima, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   18 ( 27 ) 3193 - 3195  2008年  [査読有り]

     概要を見る

    Trimethylsilylation of a triethoxysilylated derivative of double-four-ring ( D4R) silicate led to the formation of a novel crystalline spherical siloxane molecule containing a cubic D4R core, which proves that this bottom-up process provides a new pathway to prepare silica nanoparticles with well defined size, structure, morphology, and functionality.

    DOI

  • Organic derivatives of the layered perovskite HLaNb<inf>2</inf>O<inf>7</inf>·xH<inf>2</inf>O with polyether chains on the interlayer surface: Characterization, intercalation of LiClO<inf>4</inf>, and ionic conductivity

    Yosuke Takeda, Toshiyuki Momma, Tetsuya Osaka, Kazuyuki Kuroda, Yoshiyuki Sugahara

    Journal of Materials Chemistry   18 ( 30 ) 3581 - 3587  2008年  [査読有り]

     概要を見る

    Polyether chains have been successfully grafted onto the interlayer surface of a Dion-Jacobson-type layered perovskite, HLaNb2O7·xH2O, by a reaction between an n-decoxy-derivative of HLaNb2O7·xH2O and CH3(OCH2CH2)mOH (1 ≤ m ≤ 4). After the reaction, the interlayer distance decreases from 2.73 nm to 1.58 (m = 1), 2.07 (m = 2), 2.28 (m = 3), and 2.69 (m = 4) nm. Solid-state13C CP/MAS NMR spectroscopy indicates that the CH3(OCH2CH2)mO- groups are bound to the interlayer surface of HLaNb2O7·xH2O. The n-decoxy groups are completely removed by the reaction with CH3(OCH2CH2)mOH (m = 2 and 3), while a part of the n-decoxy groups remain after the reaction with CH3(OCH2CH2)mOH (m = 1 and 4). Upon treatment of the CH3(OCH2CH2)mO-grafted HLaNb2O7·xH2O (m = 2 or 3) with a CH3(OCH2CH2)mOH solution of LiClO4, the interlayer distance decreases further to 1.78 (m = 2) and 2.01 (m = 3) nm. Inductively coupled plasma emission spectrometry reveals the presence of lithium (0.22 (m = 2) and 0.24 (m = 3) per [LaNb2O7]). The presence of ClO4-ions is demonstrated by Raman spectroscopy, and the position of the ν1(A1) band indicates the presence of isolated ClO4-ions in the interlayer space. After treatment with a LiClO4solution, CH3(OCH2CH2)mO-grafted HLaNb2O7·xH2O (m = 2 and 3) exhibits ionic conductivity, and no clear temperature dependence is observed. © 2008 The Royal Society of Chemistry.

    DOI

  • Fabrication of mesoporous Pt nanotubes utilizing dual templates under a reduced pressure condition

    Azusa Takai, Yusuke Yamauchi, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   ( 35 ) 4171 - 4173  2008年  [査読有り]

     概要を見る

    Pt nanotubes with mesoporous walls have been successfully prepared for the first time by the combination of hard templates (porous anodic alumina membranes, PAAM) and soft templates (lyotropic liquid crystals, LLC).

    DOI

  • Self-Assembly of Alkyl-Substituted Cubic Siloxane Cages into Ordered Hybrid Materials

    Atsushi Shimojima, Ryota Goto, Norimasa Atsumi, Kazuyuki Kuroda

    CHEMISTRY-A EUROPEAN JOURNAL   14 ( 28 ) 8500 - 8506  2008年  [査読有り]

     概要を見る

    Siloxane-organic hybrids with well-ordered mesostructures were synthesized through the self-assembly of novel amphiphilic molecules that consist of cubic siloxane heads and hydrophobic alkyl tails. The monoalkyl precursors functionalized with ethoxy groups (C(n)H(2n+1)Si(8)O(12)(OEt)(7), 1 Cn, n=16, 18, and 20) were hydrolyzed under acidic conditions with the retention of the siloxane cages, leading to the formation of two-dimensional hexagonal phases by evaporation-induced self-assembly processes. Analysis of the solid-state (29)Si MAS NMR spectra of these hybrid mesostructures confirmed that the cubic siloxane units were crosslinked to form siloxane networks. Calcination of these hybrids gave mesoporous silica, the pore diameter of which varied depending on the alkyl-chain length. We also found that the precursors that had two alkyl chains formed lamellar phases, thus confirming that the number of alkyl chains per cage had a strong influence on the mesostructures. These results expand the design possibility of novel nanohybrid and nanoporous materials through the self-assembly of well-defined oligosiloxane-based precursors.

    DOI

  • A hybrid mesoporous material with uniform distribution of carboxy groups assembled from a cubic siloxane-based precursor

    Ryota Goto, Atsushi Shimojima, Hideki Kugea, Kazuyuki Kuroda

    CHEMICAL COMMUNICATIONS   ( 46 ) 6152 - 6154  2008年  [査読有り]

     概要を見る

    A novel hybrid mesoporous material functionalized with carboxy groups was synthesized by self-assembly of a novel building block consisting of a cubic siloxane unit and a long organic chain with an ester bond and the following hydrolysis of ester bonds, representing a promising approach to designing hybrid structures at both molecular and mesoscopic scales.

    DOI

  • Direct deposition of nanostructured Pt particles onto a Ni foam from lyotropic liquid crystalline phase by displacement plating

    Yusuke Yamauchi, Masaki Komatsu, Azusa Takai, Ryusuke Sebata, Makoto Sawada, Toshiyuki Momma, Minekazu Fuziwara, Tetsuya Osaka, Kazuyuki Kuroda

    ELECTROCHIMICA ACTA   53 ( 2 ) 604 - 609  2007年12月  [査読有り]

     概要を見る

    Nanostructured Pt particles are directly deposited onto a Ni foam by utilizing displacement plating after a lyotropic liquid crystalline phase including Pt species was prepared within macropores of the Ni foam. The EDS mapping of Pt after deposition corresponds to the macroscopic framework of the Ni foam, indicating the uniform displacement plating of Pt on the surface of the Ni foam. The Pt particles of 150-250 nm in size are formed over the entire area of the surface of the Ni foam. The TEM images prove that the nanoscale rods (width: about 3 nm) are aggregated with each other to form nanoscale porosity. The active area of Pt can be estimated to be ca. 12 m(2)/g by using the cyclic voltammogram in sulfuric acid. Our method realizes one-step production of hierarchical macro-meso type porous electrodes. (c) 2007 Elsevier Ltd. All rights reserved.

    DOI

  • Preparation of mesostructured siloxane-organic hybrid films with ordered macropores by templated self-assembly

    Mikako Sakurai, Atsushi Shimojima, Masaru Heishi, Kazuyuki Kuroda

    LANGMUIR   23 ( 21 ) 10788 - 10792  2007年10月  [査読有り]

     概要を見る

    Novel hierarchically ordered siloxane-based hybrid films with well-defined macropores and mesostructured pore walls have been prepared by the self-assembly process using oligomeric siloxane precursors bearing alkyl chains (CnH2n+1Si(OSi(OMe)(3))(3)) in the presence of polystyrene opal films as a template. Either a two-dimensional (2D) hexagonal structure or a lamellar structure was formed depending on the alkyl chain length of the precursors (n = 10 and 16, respectively). In both of the films, the mesostructures were oriented along the spherical surface of the template and were retained after removal of the template. Calcination of the 2D hexagonal hybrid produced ordered porous silica with both macro- and microporosities. The lamellar hybrid film exhibited a unique property of accommodating alkyl alcohols with an expansion of the interlayer spacings. These results provide a new concept for designing hierarchical hybrid materials that are potentially applicable as adsorbents, catalysts, sensors, and photonic crystals.

    DOI PubMed

  • Intercalation of poly(oxyethylene) alkyl ether into a layered silicate kanemite

    Nobuyuki Takahashi, Hiroaki Tamura, Dai Mochizuki, Tatsuo Kimura, Kazuyuki Kuroda

    LANGMUIR   23 ( 21 ) 10765 - 10771  2007年10月  [査読有り]

     概要を見る

    Poly(oxyethylene) alkyl ether (C,,EO) is intercalated into the interlayer space of a layered silicate kanemite by using layered hexadecyltrimethylammonium (C(16)TMA) intercalated kanemite (C(16)TMA-kanemite) as the intermediate. C(16)TMA-kanemite was treated with an aqueous solution of C16EO10, and the intercalation of C16EO10 was confirmed by the slight increase in the basal spacing (from 2.92 to 3.34 nm) with the increase in the carbon content, yielding C16EO10-C(16)TMA-kanemite. The product was dispersed again in a C16EO10 aqueous solution, and then 1.0 M HCl was added to the suspension to remove C16TMA ions completely. The basal spacing was further increased (from 3.34 to 5.52 nm) and the content of nitrogen was virtually zero, indicating further intercalation of C16EO10 molecules and complete elimination of C(16)TMA ions simultaneously. Though C16EO10 molecules are not directly intercalated into kanemite, the mutual interactions among C(16)TMA ions, C16EO10 molecules, and the interlayer silicate surfaces effectively induce the intercalation Of C16EO10. C16EO10-kanemite shows a reversible adsorption of n-decane and water owing to the hydrophobicity and hydrophilicity of C(16)Eo(10), respectively, in the interlayer space. Layered CnEO10-kanemites (n = 12 and 18) were also synthesized in a manner similar to layered C16EO10-kanemite.

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  • Structural design in the silicate framework of ordered mesoporous silica derived from kanemite

    T. Kimura, H. Tamura, M. Tezuka, D. Mochizuki, T. Shigeno, K. Kuroda

    Studies in Surface Science and Catalysis   170   1740 - 1747  2007年10月  [査読有り]

     概要を見る

    The silicate framework of ordered mesoporous silica KSW-2 was chemically designed and structurally stabilized by direct silylation of the mesostructured precursor using silylating agents such as octoxytrichlorosilane (C8H17OSiCl3) and octylmethyldichlorosilane (C8H17-(CH3)SiCl2). Depending on the molecular structures of the silylating agents, pure silica type and surface-modified type mesoporous materials can be obtained with the retention of the molecularly ordered framework because of the presence of the new silicate units strengthened by silylation, and the framework was thermally more stable. © 2007 Elsevier B.V. All rights reserved.

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  • Preparation of porous solids composed of layered niobate walls from colloidal mixtures of niobate nanosheets and polystyrene spheres

    Nobuyoshi Miyamoto, Kazuyuki Kuroda

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   313 ( 1 ) 369 - 373  2007年09月  [査読有り]

     概要を見る

    Macroporous solids with crystalline layered walls were fabricated from colloidal mixtures of size-controlled niobate nanosheets and polystyrene spheres. The macroporous solids, obtained after burning off the spheres, were characterized by scanning electron microscopy and X-ray diffraction. The obtained structures strongly depended on the lateral dimension L of the nanosheets used, When small nanosheets (L = 100 nm) were used, partly ordered macroporous solids with interconnected pores were obtained, whereas sponge-like random macroporous structures were obtained with larger nanosheets (L = 190 and 270 nm). Peapod-like hollow structures were obtained when we used small (L = 190 nm) and very large (L = 3 mu m) nanosheets at the same time. The microstructure of the pore walls was controllable by changing the calcination conditions. The walls were composed of propylammonium/K4Nb6O17 intercalation compound which has a layered structure with exchangeable cations in the interlayer space, stable up to 350 degrees C for 6 h on calcination. The walls were converted to crystalline K8Nb18O49 after calcination at 500 degrees C for 6 h. (c) 2007 Elsevier Inc. All rights reserved.

    DOI PubMed

  • One-pot preparation of mesoporous silica particles having mesopore surface functionalized with poly(propylene oxide) chains

    Chihiro Urata, Yusuke Yamauchi, Dai Mochizuki, Kazuyuki Kuroda

    CHEMISTRY LETTERS   36 ( 7 ) 850 - 851  2007年07月  [査読有り]

     概要を見る

    Mesoporous silica particles having mesopore surface functionalized with poly(propylene oxide) (PPO) chains were prepared in one pot by using newly designed triethoxysilylterminated poly(ethylene oxide) (PEO)-PPO-PEO triblock copolymers with structure-directing and surface-modifying dual functions.

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  • Formation of mesoporous silica from a layered polysilicate makatite

    Hiroaki Tamura, Dai Mochizuki, Tatsuo Kimura, Kazuyuki Kuroda

    CHEMISTRY LETTERS   36 ( 3 ) 444 - 445  2007年03月  [査読有り]

     概要を見る

    Mesoporous silicas with highly ordered and less ordered mesopores were formed through the reaction of a crystalline layered polysilicate makatite with hexadecyltrimethylammonium (C(16)TMA) chloride. The uniqueness of makatite as a starting material for the formation of mesostructured silica is verified.

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  • Synthesis and structural characterization of a highly ordered mesoporous Pt-Ru alloy via "evaporation-mediated direct templating"

    Yusuke Yamauchi, Tetsu Ohsuna, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   19 ( 6 ) 1335 - 1342  2007年03月  [査読有り]

     概要を見る

    Highly ordered 2D-hexagonal mesoporous Pt-Ru alloy particles were deposited by an electrochemical process after a lyotropic liquid crystalline (LLC) film including both Pt and Ru species was prepared on a conductive substrate from a diluted surfactant solution by casting. We have determined the alloy state by using high-resolution scanning electron microscopy (HR-SEM), transmission electron microscopy (TEM), energy-dispersive X-ray spectroscopic (EDS) mapping, and X-ray photoelectron spectroscopy (XPS). The HR-SEM images show that the porous nanostructures are formed over the entire area on the external surface of each particle. The TEM images prove that the pore wall is composed of connected nanoparticles of ca. 3 nm in size and that the lattice fringes assigned to a fcc structure are randomly oriented. The EDS mapping shows both elements of Pt and Ru are well distributed within the pore wall. From the XPS data, Ru atoms in the alloy are thought to basically be in the zerovalent metallic state, Ru(0). These results indicate the formation of mesoporous intermetallic Pt-Ru alloys. The structural information on the mesoporous alloys should be very useful for development of mesoporous metals toward advanced nanomaterials.

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  • Structure and properties of multilayered siloxane-organic hybrid films prepared using long-chain organotrialkoxysilanes containing C=C double bonds

    Atsushi Shimojima, Chia-Wen Wu, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   17 ( 7 ) 658 - 663  2007年  [査読有り]

     概要を見る

    Oriented multilayered films composed of alternating siloxane layers and organic layers were prepared from mixtures of tetramethoxysilane [Si(OMe)(4)] and unsaturated organotrimethoxysilane [RSi(OMe)(3), where R is CH2=CH(CH2)(8-) or CH2=CH(CH2)(2)CH=CH(CH2)(4)-], and the structures and macroscopic properties of the films were studied. Hydrolysis and partial condensation of the precursors led to the formation of amphiphilic organosiloxane species which self-assemble into lamellar phases. Polymerization of the organic phase occurred by UV irradiation, as evidenced by substantial decreases of the IR absorption bands due to -CH=CH2 or -CH=CH- groups. The hardness of the films was remarkably increased by the irradiation, due to the covalent linking of adjacent siloxane layers by organic polymerization. The films after organic polymerization had a much higher resistance to an alkaline solution, which enabled the patterning of the films on the micrometer length scale. These results provide an important insight into the structure-property relationships of nanostructured hybrid materials prepared by sol-gel chemistry.

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  • Fabrication of hierarchically ordered porous films composed of imogolite via colloidal templating

    Yoshiyuki Kuroda, Mamoru Tamakoshi, Junnosuke Murakami, Kazuyuki Kuroda

    Journal of the Ceramic Society of Japan   115 ( 1339 ) 233 - 236  2007年  [査読有り]

     概要を見る

    Hierarchically ordered porous materials composed of imogolite with macro-, meso- and microporous systems were fabricated via colloidal templating. The monodispersed polystyrene particles used as templates were assembled into a close-packed structure on Si substrates. An imogolite sol was infiltrated into voids of polystyrene particles to form composite films. The ordered macropores as well as micro- and mesopores originating from imogolite were confirmed after the removal of templates by either extraction with toluene or calcination. The films were stable in organic solvents, such as acetone, ethanol, and hexane. Although the extracted film was unstable in water, the stability was improved by calcination. Imogolite is found to be a quite useful building block to fabricate hierarchically ordered porous materials with a wide range of porosities without using surfactants as templates.

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  • Orientational control of hexagonally packed silica mesochannels in lithographically designed confined nanospaces

    Chia-Wen Wu, Tetsu Ohsuna, Tomohiro Edura, Kazuyuki Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   46 ( 28 ) 5364 - 5368  2007年  [査読有り]

     概要を見る

    A top-down/bottom-up approach has been developed to fabricate mesoporous silica with well-aligned mesochannels of controlled orientation by means of cooperative assembly of an amphiphilic tri-block copolymer (P123) and silica species within lithographically designed confined nanospaces. Some mesochannel patterns that can be prepared by this technique are shown schematically in the picture. TEOS = tetraethoxysilane. (Figure Presented). © 2007 Wiley-VCH Verlag GmbH &amp; Co. KGaA.

    DOI PubMed

  • Deposition of single-crystalline mesoporous silica particles and the in-plane arrangement of mesocages over particles on a cleaved mica surface

    Takashi Suzuki, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   17 ( 45 ) 4762 - 4767  2007年  [査読有り]

     概要を見る

    Single-crystalline mesoporous silica particles with a 3D-hexagonal mesostructure were deposited hydrothermally on a freshly cleaved mica surface, and the controlled in-plane arrangement of mesocages over particles was achieved. The in-plane arrangement of mesocages of formed particles with a decaoctahedral-like shape reflected the surface structure of mica. The characterization results of mesostructured silica particles prepared at the early formation stages suggest that silica particles containing surfactants are initially deposited and that the mesostructure subsequently transformed from a disordered to an ordered one inside each silica particle.

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  • Magnetically induced orientation of mesochannels in mesoporous silica films at 30 Tesla

    Yusuke Yamauchi, Makoto Sawada, Masaki Komatsu, Atsushi Sugiyama, Tetsuya Osaka, Noriyuki Hirota, Yoshio Sakka, Kazuyuki Kuroda

    CHEMISTRY-AN ASIAN JOURNAL   2 ( 12 ) 1505 - 1512  2007年  [査読有り]

     概要を見る

    We demonstrate the magnetically induced orientation of mesochannels in mesoporous silica films prepared with low-molecular-weight surfactants under an extremely high magnetic field of 30 T. This process is principally applicable to any type of surfactant that has magnetic anisotropy because such a high magnetic field provides sufficient magnetic energy for smooth magnetic orientation. Hexade-cyltrimethylammonium bromide (CTAB) and polyoxyethylene-10-cetyl ether (Brij 56) were used as cationic and nonionic surfactants, respectively. According to XRD and cross-sectional TEM, mesochannels aligned perpendicular to the substrates were observed in films prepared with low-molecular-weight surfactants, although the effect was incomplete. The evolution of these types of films should lead to future applications such as highly sensitive chemical sensors and selective separation.

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  • Fabrication of a Pt film with a well-defined hierarchical pore system via "solvent-evaporation-mediated direct physical casting"

    Yusuke Yamauchi, Kazuyuki Kuroda

    ELECTROCHEMISTRY COMMUNICATIONS   8 ( 10 ) 1677 - 1682  2006年10月  [査読有り]

     概要を見る

    We fabricated a well-ordered Pt thin film with a bimodal pore system by combining the modified liquid crystal templating method (solvent-evaporation-mediated direct physical casting, SEDPC) with colloidal crystal templating. The direct observation of the film by high-resolution scanning microscopy (HR-SEM) showed the formation of a hierarchical porous structure. The resulting Pt film possesses macropores (ca. 460 nm), interconnected windows (ca. 100 nm), and mesopores (ca. 3-4 nm). Macropore wall consists of small nanoparticles of ca. 3 nm in size. These nanoparticles are interconnected to create mesoporosity. The cyclic voltammogram of the resulting Pt film in sulfuric acid revealed a typical feature which can identify the clean Pt surface. (c) 2006 Elsevier B.V. All rights reserved.

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  • Critical effect of surfactant concentration on the structure of mesoporous silica films prepared on a substrate coated with rubbing-treated polyimide

    Takashi Suzuki, Hirokatsu Miyata, Masatoshi Watanabe, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   18 ( 20 ) 4888 - 4893  2006年10月  [査読有り]

     概要を見る

    The change of nonionic surfactant C-16(EO)(10) (Brij56) concentration has a critical effect on the structure of mesoporous silica films grown hydrothermally on a substrate coated with a rubbing-treated polyimide film. The uniaxially aligned two-dimensional (2D) hexagonal mesoporous structure changes into a "single-crystalline" three-dimensional (3D) hexagonal structure, which means that the in-plane arrangement of spherical pores of the 3D-hexagonal structure is fully controlled, by simply decreasing the surfactant concentration. The investigation of the early stages of the film formation suggests that the initial formation of the uniaxially aligned tubular micelles and the subsequent transformation to the spherical ones are included in the formation mechanism. It is considered that such a transformation is caused by the increase in the size of headgroups of the building units, consisting of the surfactants and silica oligomers, due to the progress of silica condensation. The small association number of surfactant molecules in the building units would allow the growth of silica oligomers in the headgroups to the level that induces the total restructuring.

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  • Synthesis of microporous inorganic-organic hybrids from layered octosilicate by silylation with 1,4-bis(trichloro- and dichloromethyl-silyl)benzenes

    Dai Mochizuki, Sachiko Kowata, Kazuyuki Kuroda

    CHEMISTRY OF MATERIALS   18 ( 22 ) 5223 - 5229  2006年10月  [査読有り]

     概要を見る

    Crystalline microporous inorganic-organic nanohybrids were synthesized by pillaring layered octosilicate with 1,4-bis( trichlorosilyl)benzene or 1,4-bis(dichloromethylsilyl)benzene. The silylating agents were preferentially bridged between the layers of octosilicate, resulting in the formation of microporous hybrids with BET surface areas of similar to 500 m(2)/g. The trichlorosilyl or dichloromethylsilyl groups were regularly grafted with confronting two Si-OH groups on the same octosilicate surface, and each reacted group possessed one unreacted site (chloro or methyl group). The micropores derived from 1,4-bis(trichlorosilyl)benzene showed a hydrophilic nature due to remaining Si-OH groups after hydrolysis of chlorosilyl groups, whereas those derived from 1,4-bis(dichloromethylsilyl)benzene showed a hydrophobic nature. The difference affected the phenol adsorption behavior from dilute aqueous solutions.

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  • Development of microfabrication process of mesoporous Pt via "Solvent-Evaporation-mediated Direct Physical Casting": Selective deposition into sloped microchannels

    Yusuke Yamauchi, Hiroki Kitoh, Toshiyuki Momma, Tetsuya Osaka, Kazuyuki Kuroda

    SCIENCE AND TECHNOLOGY OF ADVANCED MATERIALS   7 ( 5 ) 438 - 445  2006年07月  [査読有り]

     概要を見る

    We have developed an excellent process for selective deposition of mesoporous Pt through tailored microfabrication steps via the "Solvent-Evaporation-mediated Direct Physical Casting (SEDPC)" method. The direct observation by high-resolution scanning microscopy (HR-SEM) shows the formation of an ordered mesoporous structure in a very confined area. The cyclic voltammogram of the mesoporous Pt reveals a typical feature of Pt surface. The surface morphology and ordering of the mesostructure strongly depend on the electrodeposition conditions (constant-current and constant-potential depositions). The roughness factors are greatly enhanced as the charge densities in the constant-current deposition are increased. These findings are important for the morphological design of mesoporous metals in a micrometer scale. (c) 2006 NIMS and Elsevier Ltd. All rights reserved.

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  • Formation of highly ordered mesoporous titania films consisting of crystalline nanopillars with inverse mesospace by structural transformation

    CW Wu, T Ohsuna, M Kuwabara, K Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   128 ( 14 ) 4544 - 4545  2006年04月  [査読有り]

     概要を見る

    Highly ordered mesoporous titania films consisting of crystalline nanopillars with open-spaced, perpendicular, and continuous porosity have been prepared via structural transformation from a 3D hexagonal mesostructure during the thermal treatment. The mechanism of the structural transformation is explained by the crystallization of the titania framework and the large contraction of the initial 3D hexagonal mesostructured film upon calcination. This structural transformation provides a new approach to generate mesoporous thin-film materials with unique structures. Copyright © 2006 American Chemical Society.

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  • Design of silicate nanostructures by interlayer alkoxysilylation of layered silicates (magadiite and kenyaite) and subsequent hydrolysis of alkoxy groups

    D Mochizuki, K Kuroda

    NEW JOURNAL OF CHEMISTRY   30 ( 2 ) 277 - 284  2006年02月  [査読有り]

     概要を見る

    Silica nanostructures are sophisticatedly designed by interlayer alkoxysilylation of layered silicates (magadiite and kenyaite) with alkoxytrichlorosilanes and the subsequent hydrolysis of alkoxy groups. The dichlorosilyl groups Of alkoxytrichlorosilanes [(RO)ClSiCl2] were reacted onto two neighboring Si-OH groups On the surface of the layered silicates to form a bridge, leaving two functional (Si-OR and Si-Cl) groups On the bridge. The remaining bifunctional groups were almost completely hydrolyzed to transform into Si-OH groups. Depending oil the solvent for hydrolysis, the hydrolyzed product derived from magadiite forms either a new 3-D silicate structure by condensation of interlayer silanol groups or a new 2-D silicate structure by geminal Si-OH groups remaining immobilized on both sides of the silicate layers. The 3-D silicate structure exhibits microporosity (130 m(2) g(-1)) and hydrophilic behavior. On the other hand, the hydrolyzed product from kenyaite takes only a 2-D silicate structure, even when the solvents for hydrolysis were completely evaporated.

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  • Sol-gel synthesis of a nanostructured hybrid material from an organosiloxane oligomer with a terminal phenyl group

    Atsushi Shimojima, Norimasa Atsumi, Noritaka Umeda, Yasuhiro Fujimoto, Kazuyuki Kuroda

    Journal of the Ceramic Society of Japan   114 ( 1334 ) 819 - 822  2006年  [査読有り]

     概要を見る

    A novel ordered siloxane-organic hybrid material has been prepared by hydrolysis and polycondensation of a well-defined alkoxysilane precursor consisting of a tetrasiloxane unit and a 4-phenylbutyl group (1). Evaporation-induced self-assembly during hydrolysis and polycondensation of 1 led to the formation of a two-dimensional (2D) hexagonal mesostructure, which was revealed by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Solid-state 13C CP/MAS NMR and 29Si MAS NMR confirmed that the product consisted of 4-phenylbutyl groups and siloxane networks, both of which are linked via Si-C bonds. These results will allow us to produce functional hybrid materials by chemical modification of phenyl groups, and also by incorporating other organic groups. Furthermore, calcination of this hybrid to remove organic groups led to the creation of an ordered microporous silica with the Brunauer-Emmett-Teller (BET) surface area of 570 m2 g-1 and the average pore diameter of 1.2 nm.

    DOI

  • Mesophase of colloidally dispersed nanosheets prepared by exfoliation of layered titanate and niobate

    T Nakato, Y Yamashita, K Kuroda

    THIN SOLID FILMS   495 ( 1-2 ) 24 - 28  2006年01月  [査読有り]

     概要を見る

    Colloidal dispersion of oxide nanosheets was prepared by exfoliation of lepidocrocite-type layered titanate H1.01Ti1.73O4, and the obtained "nanosheet colloid" formed a liquid crystalline phase which was detected by birefringence of the colloid with naked-eye and optical microscope observations between crossed polarizers. The nanosheet colloids exhibited phase transition from isotropic to isotropic-liquid crystalline biphasic, and finally to full liquid crystalline, as the nanosheet concentration increased. The mesophase was characterized by the stability; liquid crystallinity appeared at low particle concentrations due to high aspect ratio (around 1 tun of thickness and similar to 7 mu m of lateral length) of the nanosheets. Mixing the titanate nanosheet colloid with hectorite clay yielded apparently homogeneous birefringent colloids, where a cationic cyanine dye was selectively adsorbed onto the clay nanosheets. (c) 2005 Elsevier B.V. All rights reserved.

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  • Surfactant-free synthesis of lamellar and wormhole-like silica mesostructures by using 1-alkynyltrimethoxysilanes

    Y Fujimoto, A Shimojima, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   16 ( 10 ) 986 - 994  2006年  [査読有り]

     概要を見る

    Silica-based nanomaterials with lamellar and wormhole-like mesostructures were prepared via self-assembly processes using 1-alkynyltrimethoxysilanes (CH3(CH2)(n-3)C CSi(OCH3)(3); 1Cn, n = 10, 16) containing a C-C triple bond adjacent to the silicon atom. Hydrolysis and polycondensation of 1C10 afforded a viscous paste, whereas 1C16 formed a lamellar hybrid consisting of siloxane layers and bilayers of alkynyl groups. Wormhole-like mesostructures were formed by co-hydrolysis and polycondensation of 1Cn and tetramethoxysilane ( TMOS) followed by evaporation of solvents at room temperature for n = 10 and at 50 degrees C for n = 16. Removal of alkynyl groups from the wormhole-like mesostructures either by chemical treatment using fluoride ions or by calcination afforded mesoporous silica with three-dimensional pore-connectivity. This procedure affords one of the synthetic pathways to prepare mesoporous silica without surfactants as templates. The N-2 adsorption data revealed that the chemically treated products had larger pore diameters and pore volumes than those of the calcined products. The pore diameter and the pore wall thickness were controlled by changing the alkynyl chain length and the TMOS/1Cn molar ratio, respectively. Furthermore, transparent thin films of a wormhole-like mesostructure could be prepared from a 1C10-TMOS or 1C10-1C16-TMOS system, although only a lamellar thin film was obtained from a 1C16-TMOS system.

    DOI

  • Designed synthesis of nanostructured siloxane-organic hybrids from amphiphilic silicon-based precursors

    A Shimojima, K Kuroda

    CHEMICAL RECORD   6 ( 2 ) 53 - 63  2006年  [査読有り]

     概要を見る

    This paper reports on recent progress in the synthesis of nanostructured siloxane-organic hybrids based on the self-assembly of amphiphilic silicon-based precursors. A variety of ordered hybrid materials have been obtained by molecular design of the precursors. Alkoxysilanes and chlorosilanes with covalently attached hydrophobic organic tails are hydrolyzed to form amphiphilic molecules containing silanol groups, leading to the formation of layered (lamellar) structures. Transparent and oriented thin films of lamellar hybrids were prepared by the reaction in the presence of tetraalkoxysilane. In addition, the design of molecules having alkyl chains and large oligosiloxane heads led to the formation of mesophases consisting of cylindrical assemblies, providing a direct pathway to ordered porous silica. The synthesis, structural features, and formation processes of these hybrid mesostructures are discussed. (C) 2006 The Japan Chemical journal Forum and Wiley Periodicals, Inc.

    DOI PubMed

  • Synthesis and characterization of mesoporous Pt-Ni (H-I-Pt/Ni) alloy particles prepared from lyotropic liquid crystalline media

    Y Yamauchi, SS Nair, T Momma, T Ohsuna, T Osaka, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   16 ( 23 ) 2229 - 2234  2006年  [査読有り]

     概要を見る

    Mesoporous intermetallic Pt-Ni alloys with various compositions have been produced by the chemical reduction of two metal (nickel and platinum) salts dissolved in aqueous domains of a lyotropic liquid crystalline (LLC) phase. The mesoporous Pt-Ni alloys are small particles less than 100 nm in size and exhibit high specific surface areas higher than 40 m(2) g(-1). The ordering of the mesostructure decreases with increasing Ni content in the alloys. The high resolution scanning electron microscopic (HR-SEM) images show that the porous nanostructures are indeed formed over the entire area on the external surface of the particles. The lattice parameters of the alloys decrease with the increasing Ni content, implying the incorporation of Ni. The X-ray photoelectron spectroscopic (XPS) data show that Ni atoms in the alloys are thought to be in the zerovalent metallic state (Ni-0). The transmission electron microscopic (TEM) images prove that the lattice fringes assigned to a fcc structure are randomly oriented in the pore walls. The energy-dispersive X-ray spectroscopic (EDS) mapping shows uniform distribution of Ni atoms in the porous matrix. These results indicate the formation of mesoporous intermetallic Pt-Ni alloys.

    DOI

  • Structural study of highly ordered mesoporous silica thin films and replicated Pt nanowires by high-resolution scanning electron microscopy (HRSEM)

    Chia-Wen Wu, Yusuke Yamauchi, Tetsu Ohsuna, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   16 ( 30 ) 3091 - 3098  2006年  [査読有り]

     概要を見る

    We have investigated the structures of mesostructured ( before calcination) and mesoporous ( after calcination) silica thin films and replicated Pt nanowires by high-resolution scanning electron microscopy (HRSEM). Highly ordered lamellar, two-dimensional (2D) hexagonal, and three-dimensional (3D) hexagonal mesostructured/mesoporous silica thin films were synthesized by adjusting the concentration of triblock copolymer (EO20PO70EO20; P123) used as a structure-directing agent. Direct HRSEM observation of these mesostructured/mesoporous silica thin films demonstrated that they have inherent external structures on the top surfaces: ( 1) the lamellar mesostructured silica film exhibits a smooth plane; ( 2) the 2D hexagonal mesoporous silica film exhibits curved stripes; ( 3) the 3D hexagonal mesoporous silica film exhibits 2D porous arrangements ( e. g. 6-fold symmetry and pseudo 4-fold symmetry). The removal of P123 by calcination had no effect on the surface structure but caused an anisotropic contraction, as found from cross-sectional images. Methods for the formation of the 2D hexagonal mesoporous film affected the orientation of mesochannels. Pt replicates, electrodeposited in the mesochannels of the 2D hexagonal mesoporous silica films, exhibited new structures, i.e., S-shaped, Y-shaped, and swirling-shaped nanowires with ellipsoidal cross section. Direct HRSEM observation of the mesostructured/mesoporous silica thin films on the top surface and cross section provides detailed information on the external and internal structures, which is significant and useful for various applications of these thin films.

    DOI

  • Magnetically induced orientation of mesochannels in 2D-hexagonal mesoporous silica films

    Yusuke Yamauchi, Makoto Sawada, Atsushi Sugiyama, Tetsuya Osaka, Yoshio Sakka, Kazuyuki Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   16 ( 37 ) 3693 - 3700  2006年  [査読有り]

     概要を見る

    Mesoporous silica films with uniaxially oriented mesochannels were prepared by dip coating under a steady-homogeneous magnetic field parallel to a substrate. The effect of a strong magnetic field ( 12 Tesla) on the preparation of mesoporous silica films was systematically investigated by using two kinds of templates. When mesoporous silica films with a 2D-hexagonal structure were prepared by using an ionic CTAB ( hexadecyltrimethylammonium bromide)-based precursor solution, the in-plane XRD results of the films proved that the mesochannels were slightly oriented parallel to the magnetic field. When mesoporous silica films were prepared by using a non-ionic P123 ( polyethylene oxide - polypropylene oxide - polyethylene oxide triblock copolymer)- based precursor solution, the directional distribution of the mesochannels became narrow (FWHM was about 20 degrees). The use of large molecules such as triblock copolymers leads to successful magnetically induced orientation. The spatial orientations of the magnetically aligned mesochannels are elucidated by theta - 2 theta XRD, in-plane XRD, cross-sectional transmission electron microscopy (TEM), and high resolution scanning electron microscopy (HR-SEM).

    DOI

  • Fabrication of mesoporous Pt inside micrometer channels via "solvent-evaporation-mediated direct physical casting"

    Y Yamauchi, T Momma, H Kitoh, T Osaka, K Kuroda

    ELECTROCHEMISTRY COMMUNICATIONS   7 ( 12 ) 1364 - 1370  2005年12月  [査読有り]

     概要を見る

    We have proposed a novel convenient pathway via solvent-evaporation-mediated direct physical casting (SEDPC) for the fabrication of mesoporous metals in a micrometer scale. We have presented the successful deposition of highly ordered mesoporous Pt into micrometer channels prepared by lithography. The direct observation by a high-resolution scanning microscope (HR-SEM) showed the formation of highly ordered 2D-hexagonal (p6mm) mesoporous metals onto such substrates. The cyclic voltammogram of the mesoporous Pt in sulfuric acid revealed a typical feature which can identify the clean Pt surface. Moreover, mesoporous Pt exhibits an effective reduction of dissolved dioxygen molecules. It is proved that mesoporous Pt deposited in a very confined area via the SEDPC method possesses electrocatalytic performance owing to Pt. (c) 2005 Elsevier B.V. All rights reserved.

    DOI

  • Unique microstructure of mesoporous Pt (H(I)-Pt) prepared via direct physical casting in lyotropic liquid crystalline media

    Y Yamauchi, T Momma, M Fuziwara, SS Nair, T Ohsuna, O Terasaki, T Osaka, K Kuroda

    CHEMISTRY OF MATERIALS   17 ( 25 ) 6342 - 6348  2005年12月  [査読有り]

     概要を見る

    Two-dimensional hexagonally ordered mesoporous Pt particles are prepared by Pt deposition in the aqueous domains of lyotropic liquid crystals (LLC) by chemical reduction with Zn powders. Interestingly, the framework is composed of connected nanoparticles of about 3 nm in size. Moreover, it is proved that the lattice fringes on the atomic crystallinity are coherently extended across the several nanoparticles in the framework. Such a framework composed of connected nanoparticles with extended crystallinity is uniquely created by using LLC as a soft template, which is not attainable by a traditional approach using mesoporous silica as a hard template. Through the structural identification, the formation mechanism of mesoporous Pt in the presence of LLC is thought to be continuous deposition of Pt nanoparticles from one nanoparticle.

    DOI

  • Synthesis of thermally stable and 2-D hexagonal super-microporous silica from hydrated α-sodium disilicate

    Munetaka Kato, Tetsuro Shigeno, Tatsuo Kimura, Kazuyuki Kuroda

    Chemistry of Materials   17 ( 25 ) 6416 - 6421  2005年12月  [査読有り]

     概要を見る

    Thermally stable and 2-D hexagonal super-microporous silicas were obtained utilizing hydrated α-sodium disilicate over a diverse range of surfactant/Si molar ratios. Silica-based mesostructured materials composed of hydrated α-sodium disilicate and hexadecyltrimethylammonium (C 16TMA) cations were acid-treated, resulting in the formation of 2-D hexagonal mesostructured silica(α)-n (n = C16TMA/Si molar ratio). Although the 2-D hexagonal structure of mesostructured silica(α)-0.2 collapsed at 900°C, those of mesostructured silicas(α)-0.5, -0.7, and -1.0 were retained even after calcination at 1000°C. The retention of the 2-D hexagonal structures was confirmed further by TEM. The higher thermal stability is ascribed to lower Na content in mesostructured silica(α)-n. Higher C16TMA/Si molar ratios lowered the pH values in the reaction suspensions, and then interlayer Na ions in the silicates were further exchanged with hydrated protons. Because of the higher thermal stability, ordered super-microporous silicas can be formed in the present system. The condensation of the silicate frameworks proceeded with the rise of the calcination temperature, leading to a further decrease in pore size. The pore sizes of the products calcined at 1000°C were 1.7-1.8 nm (BJH method), smaller than those reported for ordered mesoporous silicas prepared using C16TMA cations. © 2005 American Chemical Society.

    DOI

  • Self-assembly of designed oligomeric siloxanes with alkyl chains into silica-based hybrid mesostructures

    A Shimojima, Z Liu, T Ohsuna, O Terasaki, K Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   127 ( 40 ) 14108 - 14116  2005年10月  [査読有り]

     概要を見る

    A novel self-assembly route to ordered silica-organic hybrids using well-defined siloxane oligomers with alkoxy functionality and covalently attached alkyl chains has been investigated. Various hybrid mesostructures were obtained by hydrolysis and polycondensation without the use of any structure-directing agents, The oligomers 1(Cn), having an alkylsilane core and three branched trimethoxysilyl groups, formed highly ordered lamellar phases when n = 14-18, while those with shorter alkyl chains formed cylindrical assemblies, slightly distorted two-dimensional (2D) hexagonal structures (n = 6-10), and a novel 2D monoclinic structure (n = 12). Furthermore, the mixtures of 1(Cn) with different chain lengths yielded well-ordered 2D hexagonal phases, possibly due to the better packing of the precursors. The hybrids consisting of cylindrical assemblies were converted to ordered porous silica with tunable pore sizes upon calcination to remove organic groups. The liquid-state Si-29 NMR analysis of the hydrolysis and polycondensation processes of l(Cn) revealed a unique intramolecular reaction yielding primarily the oligomer with a tetrasiloxane ring which is a new class of amphiphilic molecule having both self-assembling ability and high cross-linking ability. We also found that the mesostructure (lamellar or 2D hexagonal) was strictly controlled by varying the number of siloxane units per alkyl chain. These results provide a deeper understanding of the present self-assembly process that is strongly governed by the molecular packing of oligosiloxane precursors.

    DOI PubMed

  • Interlayer esterification of layered silicic acid-alcohol nanostructured materials, derived from alkoxytrichlorosilane

    Y Fujimoto, A Shimojima, K Kuroda

    LANGMUIR   21 ( 16 ) 7513 - 7517  2005年08月  [査読有り]

     概要を見る

    Layered silicic acid-organic nanohybrid materials consisting of long-chain alkoxy groups attached to thin silica layers have been prepared via esterification of a layered silicic acid-alcohol nanostructured material derived from hexadecoxytrichlorosilane (C(16)H(33)OSiCl(3)). The esterification reaction was performed by heating the layered composite. The detailed characterization of the product heated at 80 degrees C revealed that the interlayer alcohol molecules partly (similar to 50%) reacted with the interlayer surface silanol groups to form alkoxy groups. Unreacted alcohol molecules were removed by tetrahydrofuran (THF) treatment to form a novel alkoxylated layered silica material. This product retains its structure up to 120 degrees C and has a higher stability in organic solvents if compared with the layered silicic acid-alcohol nanocomposite before esterification, whose structure collapsed over 100 degrees C. Furthermore, various alcohols can be adsorbed into the esterified nanohybrid with the expansion of the interlayer spacing.

    DOI

  • Adsorption of alcohols from aqueous solutions into a layered silicate modified with octyltrichlorosilane

    Fujita, I, K Kuroda, M Ogawa

    CHEMISTRY OF MATERIALS   17 ( 14 ) 3717 - 3722  2005年07月  [査読有り]

     概要を見る

    The adsorption of 1-hexanol and 1-butanol from water on the organically modified layered silicates, derived from magadiite by silylation with octyltrichlorosilane, was investigated. The degree of the interlamellar surface coverage of magadiite with octylsilyl groups affected the adsorptive properties. The modified magadiites with lower coverage adsorbed alcohols from aqueous solutions with lower concentrations. Both 1-hexanol and 1-butanol were adsorbed from aqueous solutions with very similar relative concentrations, suggesting that the solubilities of 1-hexanol and 1-butanol in water were correlated with the adsorption behavior. 1-Hexanol was adsorbed preferentially from a 1-hexanol/1-butanol aqueous mixture under limited conditions.

    DOI

  • Molecular manipulation of two- and three-dimensional silica nanostructures by alkoxysilylation of a layered silicate octosilicate and subsequent hydrolysis of alkoxy groups

    D Mochizuki, A Shimojima, T Imagawa, K Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   127 ( 19 ) 7183 - 7191  2005年05月  [査読有り]

     概要を見る

    A novel methodology for constructing molecularly ordered silica nanostructures with twodimensional (2-D) and three-dimensional (3-D) networks has been developed by using a stepwise process involving silylation of a layered silicate octosilicate with alkoxytrichlorosilanes [ROSiCl3, R = alkyl] and subsequent reaction within the interlayer spaces. Alkoxytrichlorosilanes react almost completely with octosilicate, bridging two closest Si-OH (or -O-) sites on the silicate layers, to form new five-membered rings. The unreacted functional groups, Si-Cl and Si-OR, are readily hydrolyzed by the posttreatment with a water/dimethyl sulfoxide (DMSO) or water/acetone mixture, leading to the formation of two types of silicate structures. The treatment with a water/DMSO mixture produced a unique crystalline 2-D silicate framework with geminal silanol groups, whereas a water/acetone mixture induced hydrolysis and subsequent condensation between adjacent layers to form a new 3-D silicate framework. The 2-D structure is retained by the presence of DMSO molecules within the swelled interlayer spaces and is transformed to a 3-D silicate upon desorption of DMSO. The structural modeling suggests that both of the 3-D silicates contain new cagelike frameworks where solvent molecules are trapped even at high temperature (up to 380 &DEG; C, in the case of acetone). Both 2-D and 3-D silica structures are quite different from known layered silicates and zeolite-like materials, indicating the potential of the present approach for precise design of various silicate structures at the molecular level.

    DOI

  • Energy transfer between chlorophyll derivatives in silica mesostructured films and photocurrent generation

    H Furukawa, N Inoue, T Watanabe, K Kuroda

    LANGMUIR   21 ( 9 ) 3992 - 3997  2005年04月  [査読有り]

     概要を見る

    Layered silica/surfactant mesostructured thin films containing chlorophyllous pigments [C13(2)-demethoxycarbonyl-pheophytin b (pyroPheo b) or zinc C13(2)-demethoxycarbonyl-chlorophyll b (Zn-pyroCh1 b)] have been prepared on an indium tin oxide (ITO) electrode grafted with a chlorophyll derivative possessing a triethoxysilyl group (copper C13(2)-demethoxycarbonyl-chlorophyllide a 3-triethoxysilyl propylamide, Cu-APTES-Chl a) to achieve effective light harvesting and successive photocurrent generation by the mesostructured films. The incorporation of pyroPheo b and Zn-pyroChl b in the mesostructured film resulted in 1.2- and 1.6-fold increases of the photocurrent density, respectively, as compared to the case of an antenna pigment-free film also grafted to a surface-modified ITO electrode. The difference action spectra, between the electrodes with and without the antenna pigments, coincided well with the absorption spectra of the immobilized pigments. Because direct electron injection from the antenna pigments in the mesostructured films to the ITO electrode was scarcely observed, the energy transfer from the antenna pigments to Cu-APTES-Chl a plays an important role for the increase in photocurrent density. The usefulness of the mesostructured films as model systems is discussed in relation to the photosynthetic primary processes of higher plants.

    DOI

  • Synthesis and characterization of mesostructured alloys with controlled compositions

    Y. Yamauchi, S. Sadasivan Nair, T. Yokoshima, T. Momma, T. Osaka, K. Kuroda

    Studies in Surface Science and Catalysis   156   457 - 464  2005年01月  [査読有り]

     概要を見る

    This article summarizes our recent studies on the synthesis of highly ordered mesostructured Ni and Ni-Co alloys by electroless deposition method. We propose that a careful control over the nucleation as well as the grain growth by reducing agents can lead to the formation of a highly ordered mesostructure from a lyotropic liquid crystalline phase (LLC). The sophisticated combination of dimethylamineborane (DMAB) and sodium borohydride (SBH) in an electroless plating bath produces highly ordered mesoporous Ni, and this technique can be extended to prepare a series of mesostructured Ni-Co alloys with various compositions. The composition of the alloys can be varied easily by controlling the metal compositions in the plating bath. © 2005 Elsevier B.V. All rights reserved.

  • Orientation of mesochannels in continuous mesoporous silica films by a high magnetic field

    Y Yamauchi, M Sawada, T Noma, H Ito, S Furumi, Y Sakka, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   15 ( 11 ) 1137 - 1140  2005年  [査読有り]

     概要を見る

    The effect of a high magnetic field on the orientation of mesochannels in continuous mesoporous silica films is demonstrated; the orientation of mesochannels in the film can be induced parallel to the magnetic field, though the effect is not complete.

    DOI

  • Highly ordered mesostructured Ni particles prepared from lyotropic liquid crystals by electroless deposition: the effect of reducing agents on the ordering of mesostructure

    Y Yamauchi, T Momma, T Yokoshima, K Kuroda, T Osaka

    JOURNAL OF MATERIALS CHEMISTRY   15 ( 20 ) 1987 - 1994  2005年  [査読有り]

     概要を見る

    Mesostructured Ni and Co particles are formed by metal deposition in the aqueous domains of lyotropic liquid crystals (LLC) using different reducing agents. We have investigated the role of reducing agents in metal deposition for the synthesis of highly-ordered mesoporous metals by electroless deposition. Slow metal deposition accompanied by the autocatalytic reaction of dimethylamineborane ( DMAB), caused by the combination of Ni and DMAB, led to the formation of highly-ordered mesostructured Ni.

    DOI

  • Direct physical casting of the mesostructure in lyotropic liquid crystalline media by electroless deposition

    Y Yamauchi, T Yokoshima, T Momma, T Osaka, K Kuroda

    ELECTROCHEMICAL AND SOLID STATE LETTERS   8 ( 10 ) C141 - C144  2005年  [査読有り]

     概要を見る

    Nickel particles with a highly ordered mesostructure are prepared by electroless deposition of Ni salts dissolved in aqueous domains of lyotropic liquid crystalline (LLC) media made of a nonionic surfactant (Brij 56) at a high concentration. The mesostructure inside the Ni particles after the electroless deposition has a macroscopic alignment of mesochannels derived from the LLC media which are composed of crystalline domains on a micrometer scale. It is proved that the arrangements of rod-like self-assemblies in the LLC indeed work as a scaffold to direct the grain growth of Ni. This is the first direct evidence of direct physical casting from LLC. (c) 2005 The Electrochemical Society.

    DOI

  • Layered assembly of alkoxy-substituted bis(trichlorosilanes) containing various organic bridges via hydrolysis of Si-Cl groups

    Y Fujimoto, M Heishi, A Shimojima, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   15 ( 48 ) 5151 - 5157  2005年  [査読有り]

     概要を見る

    Monoalkoxy derivatives of bis(trichlorosilanes) containing methylene, ethylene, and phenylene bridges (Cl3Si-R'-SiCl2OC16H33, R' = -CH2-, -C2H4-, -C6H4-) were synthesized and self-assembly of the amphiphilic hydrolyzed species ((HO)(3)Si - R' - Si(OH)(2)OC16H33) was investigated. Hydrolysis of all Si - Cl groups was confirmed by liquid-state Si-29 and C-13 NMR while the alkoxy groups were retained. The self-assembly was induced either by casting the hydrolyzed solutions on glass substrates or by cooling. The structures of the products were characterized by X-ray diffraction (XRD), electron microscopies (TEM and SEM), and solid-state Si-29 and C-13 NMR. The products obtained from methylene- and ethylene-bridged monomers have lamellar structures consisting of bridged polysilsesquioxane layers and all-trans hexadecanol layers, which means that alkoxy groups were cleaved during polycondensation. The large difference in the d values of these hybrids (5.84 nm and 3.40 nm) suggests the variation in the arrangement of hexadecanol molecules within the layers. In contrast, the phenylene-bridged monomer afforded a lamellar solid (d = 55.14 nm) consisting of monomeric species, where both silanol groups and alkoxy groups mostly remain intact. This is attributed to the relatively stronger interaction and hydrogen-bonding networks between hydrolyzed species.

    DOI

  • Platinum thin film with a highly ordered mesostructure by contact plating

    Y Yamauchi, T Yokoshima, T Momma, T Osaka, K Kuroda

    CHEMISTRY LETTERS   33 ( 12 ) 1576 - 1577  2004年12月  [査読有り]

     概要を見る

    By a contact plating technique using a galvanic reaction between Al and An in the presence of Pt complex, we have for the first time succeeded in the formation of a highly ordered meso-structured Pt film on a An surface by reduction of Pt ions in the presence of lyotropic liquid crystals.

    DOI

  • Silica films with a single-crystalline mesoporous structure

    H Miyata, T Suzuki, A Fukuoka, T Sawada, M Watanabe, T Noma, K Takada, T Mukaide, K Kuroda

    NATURE MATERIALS   3 ( 9 ) 651 - 656  2004年09月  [査読有り]

     概要を見る

    Films of mesoporous materials attract broad interest because of their wide applicability in the fields of optics and electronics. Although many of these films have a regular local porous structure, the structural regularity has not been used practically yet because of difficulties in its control on macroscopic scales. Here, we demonstrate the preparation of mesoporous silica films whose porous structure can be described as a single crystal, that is, a long-range order of cage-like pores is maintained over centimetre scales. These films have a three-dimensional hexagonal (space group P6(3)/mmc) porous structure, and the in-plane arrangement of the pores is strictly controlled by a polymeric substrate surface that has been treated by rubbing. This new class of single-crystalline films with mesoscopic periodic structure is a significant breakthrough in bottom-up nanotechnology, and could lead to novel devices, for example, optics in a soft X-ray region, and quantum electronics.

    DOI PubMed

  • Influence of the kind of layered disodium disilicates on the formation of silica-organic mesostructured materials

    M Kato, T Shigeno, T Kimura, K Kuroda

    CHEMISTRY OF MATERIALS   16 ( 17 ) 3224 - 3230  2004年08月  [査読有り]

     概要を見る

    Silica-based mesostructured materials are formed using hydrated alpha-sodium disilicate and hexadecyltrimethylammonium (C(16)TMA) chloride at various C(16)TMA/Si molar ratios, and compared with those from kanemite. When the C(16)TMA/Si ratios are 0.2, 0.5, 0.7, and 1.0, 2-D hexagonal structures are formed from hydrated alpha-sodium disilicate though the structures are collapsed on calcination. Less ordered hexagonal structures with straight channels arranged in one direction are formed when the C16TMA/Si ratio exceeds 1.0. In the case of the reactions of kanemite with C(16)TMA ions, lamellar mesostructures are formed at the ratios higher than 0.5, whereas a 2-D hexagonal structure is formed only at the ratio of 0.2. Mesoporous silica (SSW-1) derived from hydrated alpha-sodium disilicate is prepared at lower pH without acid treatment when the C(16)TMA/Si ratio is 2.0. The volume occupied by the headgroups Of C(16)TMA ions in hydrated a-sodium disilicate should be larger than that in kanemite because the distance between Si-O- sites in the bending direction of hydrated a-sodium disilicate is longer than that of kanemite due to the unique layered silicate structure.

    DOI

  • Synthesis of kaolinite-organic nanohybrids with butanediols

    J Murakami, T Itagaki, K Kuroda

    SOLID STATE IONICS   172 ( 1-4 ) 279 - 282  2004年08月  [査読有り]

     概要を見る

    The reaction of methoxy-modified kaolinite with 1,2- and 1,3-butanediols yielded two types of kaolinite-organic nanohybrids. The XRD, IR, and TG-DTA data showed that both diols were grafted onto the hydroxyl groups in the interlayer surfaces of kaolinite. The C-13 MAS NMR and CHN results indicated that the reaction proceeded by transesterification with methoxy groups and further esterification with hydroxyl groups. The IR spectra also showed that the interlayer environments are different between the two systems depending on the location of hydroxyl groups in diols. (C) 2004 Elsevier B.V All rights reserved.

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  • Highly ordered mesoporous Ni particles prepared by electroless deposition from lyotropic liquid crystals

    Y Yamauchi, T Yokoshima, H Mukaibo, M Tezuka, T Shigeno, T Momma, T Osaka, K Kuroda

    CHEMISTRY LETTERS   33 ( 5 ) 542 - 543  2004年05月  [査読有り]

     概要を見る

    Highly ordered mesoporous Ni particles have been prepared by electroless deposition using lyotropic liquid crystals as templates. The bath conditions, in particular the kind of the reducing agents, greatly affected the degree of the ordering of mesostructures. By using well chosen appropriate reducing agents and combining those agents, we have succeeded in synthesizing Ni particles with highly ordered mesoporosity.

    DOI

  • Visible light induced electron transfer and long-lived charge separated state in cyanine dye/layered titanate intercalation compounds

    N Miyamoto, K Kuroda, M Ogawa

    JOURNAL OF PHYSICAL CHEMISTRY B   108 ( 14 ) 4268 - 4274  2004年04月  [査読有り]

     概要を見る

    Visible light induced guest-to-host electron transfer and formation of long-lived charge separated state were demonstrated in cyanine dye/layered titanate intercalation compounds. 1,1'-Diethyl-2,2'-cyanine (dye-1) and 5,5'-dichloro-3,3',9-triethyl-thiacarbocyanine (dye-2) were intercalated into layered titanates, Cs(x)Ti(2-x/4)square(x/4)O(4) (square = vacancy, x = 0.7) and Na2Ti3O7, by cation exchange reactions with alkylammonium-exchanged forms as the intermediates. The formation of the intercalation compounds was confirmed by XRD, elemental analysis, and visible absorption and fluorescence spectroscopies. The intercalated dyes formed J-aggregates in the interlayer spaces for all the dye/titanate systems. The visible light induced electron transfer was shown by the appearance of ESR signal, which was ascribed to the radical dications of the dyes, and by the quenching of the fluorescence of the dye aggregates. Apparent lifetimes of the charge separated states were estimated from the decay curve of the ESR signal. The charge separated state was most stable in the dye-2/Cs(x)Ti(2-x/4)square(x/4)O(4) system with the lifetime of 246 min among four tested compounds.

    DOI

  • Silica-based mesostructured materials induced by surfactant assemblies in the two-dimensionally limited space of a layered polysilicate kanemite

    T Kimura, D Itoh, T Shigeno, K Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   77 ( 3 ) 585 - 590  2004年03月  [査読有り]

     概要を見る

    Silica-based mesostructured materials derived from a layered polysilicate kanemite were prepared by reactions with gemini-type diammonium (C16-3-16, C16-5-16, C16-3-1) surfactants. The surfactants were assembled in the two-dimensionally limited space between the silicate layers of kanemite. leading to the formation of lamellar, 2-d hexagonal, and disordered mesophases. Lamellar phases were formed by using C16-3-16 and C16-5-16 surfactants. An acid treatment of the lamellar C16-5-16-silicate complex induced the transformation into a 2-d hexagonal phase, whereas the C16-3-16-silicate complex retained its lamellar structure after the treatment. A disordered phase was obtained through the reaction of kanemite with C16-3-1 surfactants whose assembly shows a larger surface Curvature. The formation of layered surfactant-silicate intermediates under various conditions and the transformation to other mesophases lead to the conclusion that the formation of ordered and disordered mesostructured materials derived from kanemite simply depends on the surfactant assemblies in the two-dimensionally limited space.

    DOI

  • Discovery of mesoporous silica from layered silicates

    Kazuyuki Kuroda

    Studies in Surface Science and Catalysis   148   73 - 108  2004年01月  [査読有り]

  • Exfoliation and film preparation of a layered titanate, Na2Ti3O7, and intercalation of pseudoisocyanine dye

    N Miyamoto, K Kuroda, M Ogawa

    JOURNAL OF MATERIALS CHEMISTRY   14 ( 2 ) 165 - 170  2004年  [査読有り]

     概要を見る

    Fine powders of propylammonium-exchanged Na2Ti3O7 were successfully converted to transparent thin films by swelling ( and exfoliating) the material in water and subsequent casting and drying the obtained titanate sol on a substrate. The dispersion of the material was promoted by sonication and hydrothermal treatment of the sol. A self-standing film was also obtained by depositing the sol on a Teflon substrate and subsequent peeling off from the substrate by soaking in acetone. Taking advantage of the cation exchange capability of the films thus obtained, a cationic cyanine dye ( pseudoisocyanine) was intercalated with retaintion of the transparency and morphology of the films. Polarized visible spectra revealed that the intercalated dyes were present as J-aggregates with the dipole moment oriented parallel to the film surface. The present methodology is a convenient way to fabricate titanate - dye hybrids as films.

    DOI

  • Fabrication of magnetic mesostructured nickel-cobalt alloys from lyotropic liquid crystalline media by electroless deposition

    Y Yamauchi, T Yokoshima, T Momma, T Osaka, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   14 ( 19 ) 2935 - 2940  2004年  [査読有り]

     概要を見る

    Mesostructured binary Ni - Co alloys with various compositions are prepared for the first time by the electroless deposition of metal salts ( nickel and cobalt) dissolved in aqueous domains of the lyotropic liquid crystalline phases of a non-ionic surfactant ( Brij 56) at high concentrations. Mesostructured alloys with various Ni/Co ratios are easily obtained by changing the composition of the baths, leading to the control of saturation magnetization. The composition of the alloys affects the ordering of the mesostructure; higher Co content lowers the ordering.

    DOI

  • Selective formation of siloxane-based hybrid cages with methylene groups in the frameworks

    A Shimojima, K Kuroda

    CHEMICAL COMMUNICATIONS   ( 23 ) 2672 - 2673  2004年  [査読有り]

     概要を見る

    A new class of cage-like oligomers were selectively formed by hydrolysis and polycondensation of a methylene-bridged bistrialkoxysilane precursor in the presence of tetramethylammonium hydroxide, which led to the creation of novel silica-based hybrid materials.

    DOI

  • Formation of layered silica-alcohol nanostructured materials from alkoxytrichlorosilanes

    Y Fujimoto, A Shimojima, K Kuroda

    CHEMISTRY OF MATERIALS   15 ( 25 ) 4768 - 4774  2003年12月  [査読有り]

     概要を見る

    Novel layered silica-organic nanostructured materials were prepared by hydrolysis and condensation of alkoxytrichlorosilanes (n-CnH2n+1OSiCl3, n = 12, 14, 16, 18, and 20) as single precursors. The formation relies on the self-assembly of alkoxysilanetriols (n-CnH2n+1OSi-(OH)(3)) generated by the preferential hydrolysis of Si-Cl groups in the precursors. The products exhibited the XRD patterns indicative of layered structures whose d spacings varied in the range of 3.95 to 6.13 nm depending on the alkyl chain lengths. The SEM images of the products showed well-defined platelike morphologies on micrometer length scales, reflecting the layered structures of the products. Further structural characterization by solid-state Si-29 and C-13 NMR and FTIR revealed that the layered structures consisted of bimolecular layers of long-chain alcohols and thin silica layers. Condensation of alkoxysilanetriols proceeded in the solid state to form silica networks, being accompanied by the cleavage of the alkoxy groups. The present results provide a new approach for the construction of silica-based nanostructured materials with well-regulated organic arrays and silica networks.

    DOI

  • Synthesis of multilayered silica-based hybrid films from difunctional organosilanes by co-hydrolysis and polycondensation with tetraalkoxysilane

    N Umeda, A Shimojima, K Kuroda

    JOURNAL OF ORGANOMETALLIC CHEMISTRY   686 ( 1-2 ) 223 - 227  2003年11月  [査読有り]

     概要を見る

    Decylethyldimethoxysilane (C10EtDMS) and didecyldimethoxysilane (2C10DMS) were used to prepare thin films of silica-based hybrids by co-hydrolysis and polycondensation with tetramethoxysilane (TMOS) followed by spin-coating. The length of the second alkyl chains (Et or n-decyl) had large effects on the formation of ordered hybrid films. In the case of C10EtDMS, transparent films of well-ordered lamellar hybrids were formed with various TMOS/C10EtDMS ratios by controlling the degree of polycondensation in the precursor solutions. In contrast, no ordered hybrids were obtained in the case of 2C10DMS under the same conditions, due to the larger steric hindrance of the longer second alkyl chain in the co-condensation. Increases of both TMOS/2C10DMS and HCl/Si ratios in the starting solutions promoted polycondensation and lead to the formation of ordered hybrid films. (C) 2003 Elsevier B.V. All rights reserved.

    DOI

  • Synthesis of interlamellar silylated derivatives of magadiite and the adsorption behavior for aliphatic alcohols

    Fujita, I, K Kuroda, M Ogawa

    CHEMISTRY OF MATERIALS   15 ( 16 ) 3134 - 3141  2003年08月  [査読有り]

     概要を見る

    Interlayer silanol groups of a layered polysilicate magadiite (Na2H2Si14O30.nH(2)O) were silylated with octyltrichlorosilane via dodecyltrimethylammonium magadiite as the intermediate. Three organic derivatives with different degrees of silylation were prepared by varying the amount of the silylating reagent. Aliphatic alcohols with different alkyl chain lengths (n = 8, 12, and 16) were adsorbed into these derivatives at room temperature, and the adsorption behavior was examined. The basal spacings of the derivatized silicates were expanded after the adsorption, and larger spacings were observed when the derivatives with lower degrees of silylation and the alcohols with longer chain lengths were used. Because intercalated alcohols and alcohols taken up in the intercrystal spaces were desorbed by drying, the amounts of intercalated alcohols were estimated by surveying the relationship between the variation in the basal spacing and the amounts of alcohols in the samples treated under various drying conditions. Larger amounts of alcohols were adsorbed onto the derivatives with lower degree of silylation, indicating a possible control of the interlayer nanospace by varying the amount of grafting alkylsilyl groups.

    DOI

  • Unidirectional orientation of methylene blue intercalated in K4Nb6O17 single crystal

    Ryozo Kaito, Kazuyuki Kuroda, Makoto Ogawa

    Journal of Physical Chemistry B   107 ( 17 ) 4043 - 4047  2003年05月  [査読有り]

     概要を見る

    Intercalation of methylene blue into K4Nb6O17 single crystals was investigated for the construction of hybrid materials with three-dimensional anisotropy. By the reaction of K4Nb6O17 with a methylene blue aqueous solution in the presence of propylamine, methylene blue/K4Nb6O17 intercalation compounds were obtained. The basal spacing increased to 3.0 nm, and the macroscopic thickness of the crystal also increased. The regularity in the ac plane did not change by the reaction as evidenced by the in-plane X-ray diffraction measurements. Polarized absorption spectra showed a dichroism showing that the methylene blue/K4Nb6O17 intercalation compounds possess three-dimensionally confined nanostructures.

    DOI

  • Intercalation of a cationic azobenzene into montmorillonite

    M Ogawa, T Ishii, N Miyamoto, K Kuroda

    APPLIED CLAY SCIENCE   22 ( 4 ) 179 - 185  2003年02月  [査読有り]

     概要を見る

    The intercalation of a cationic azobenzene derivative into the interlayer space of montmorillonite has been achieved by ion exchange between sodium-montmorillonite and p-(omega-dimethyl-hydroxyethylaminonioethoxy)-azobenzene bromide. X-ray diffractometry and elemental analysis indicated that the dye cations were intercalated. The microstructures of the montmorillonite-dye intercalates were controlled by the amount of dye loaded as evidenced by the variation in basal spacings and visible absorption spectra of the materials. The intercalated azo dyes exhibit reversible trans-to-cis photoisomerization under UV and visible light irradiation. (C) 2002 Published by Elsevier Science B.V.

    DOI

  • Alignment control of a cyanine dye using a mesoporous silica film with uniaxially aligned mesochannels

    A Fukuoka, H Miyata, K Kuroda

    CHEMICAL COMMUNICATIONS   9 ( 2 ) 284 - 285  2003年  [査読有り]

     概要を見る

    The feasibility of alignment control of low-molecular-weight guest species by controlling the orientation of mesochannels in a mesoporous silica host has been shown for the first time; spectroscopically anisotropic absorption behaviour of a cyanine dye was observed upon its incorporation into the mesochannels of a mesoporous silica film with uniaxially aligned porous structure, proving that the preferred alignment of the dye molecules was achieved on a macroscopic scale.

    DOI PubMed

  • Synthesis of Al-containing mesoporous silica (KSW-2) with semi-squared channels by incorporation of Al into the framework of kanemite

    T Shigeno, K Inoue, T Kimura, N Katada, M Niwa, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   13 ( 4 ) 883 - 887  2003年  [査読有り]

     概要を見る

    Incorporation of Al into the framework of single-layered silicate kanemite and the formation of Al-containing mesoporous silica (Al-KSW-2) with semi-squared one-dimensional channels were surveyed. Al-containing delta-Na2Si2O5 was successfully obtained by thermal treatment of an aqueous sodium silicate solution (Na2O/SiO2 = 1 : 2) containing NaAlO2 up to 785-810 degreesC, depending on the amount of NaAlO2 added. After Al-containing delta-Na2Si2O5 was dispersed in distilled water, Al-containing kanemite (Al-kanemite) was obtained with tetrahedrally coordinated Al. The reaction of Al-kanemite with an aqueous solution of hexadecyltrimethylammonium (C(16)TMA) surfactant yielded a layered C(16)TMA-Al-kanemite complex which was converted to a mesostructured precursor of Al-KSW-2 by mild acid treatment. Tetrahedral coordination of Al was retained in the framework of Al-KSW-2 with high surface area (830 m(2) g(-1)) and uniform semi-squared mesopores (2.7 nm), which increased the adsorption ability for cationic dye molecules.

    DOI

  • Organic modification of the interlayer surface of kaolinite with propanediols by transesterification

    T Itagaki, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   13 ( 5 ) 1064 - 1068  2003年  [査読有り]

     概要を見る

    Propanediols (1,2- and 1,3-propanediols) were reacted with methoxy-modified kaolinite to form hydroxypropoxy-modified kaolinites by transesterification. Grafting occurred on the AlOH groups of the interlayer surface, which provides unique asymmetrical interlayer environments surrounded by both hydroxy groups of the diols and silicate layers, suggesting potential applications for specific adsorption and regioselective reactions in the interlayer spaces. When the reaction time was increased, 1,3-propanediol partly forms a bridge type grafting where both OH groups were bonded. Methoxy groups on the interlayer surface of kaolinite were eliminated by the grafting. The amounts of the grafted alkoxy groups per Al2Si2O5(OH)(4) unit were larger than that of methoxy-modified kaolinite, indicating that not only transesterification but also further grafting onto the AlOH groups proceeded. Under milder conditions, 1,2- and 1,3-propanediols were not grafted onto the interlayer surface, but molecularly intercalated.

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  • Direct formation of mesostructured silica-based hybrids from novel siloxane oligomers with long alkyl chains

    A Shimojima, K Kuroda

    ANGEWANDTE CHEMIE-INTERNATIONAL EDITION   42 ( 34 ) 4057 - 4060  2003年  [査読有り]

     概要を見る

    Lamellar and hexagonal structures of new silica-based hybrids were directly formed from newly designed alkylsiloxane oligomers 1. This approach based on the self-assembly of single precursors provides a novel pathway to ordered microporous silica as well as mesostructured silica-based hybrid materials (see scheme, 1) hydrolysis and polycondensation, 2) self-assembly).

    DOI

  • Adsorption of methylene blue onto aluminum-containing mesoporous silica films prepared by rapid solvent evaporation method

    T Yoshikawa, T Nakamura, K Kuroda, M Ogawa

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   75 ( 12 ) 2589 - 2594  2002年12月  [査読有り]

     概要を見る

    The adsorption of methylene blue onto aluminum-containing mesoporous silica films was investigated. The mesoporous silica films were synthesized by rapid solvent evaporation method using tetramethoxysilane, aluminum tri(s-butoxide), and trimethyloctadecylammonium chloride as a silica source, alumina source and supramolecular template, respectively. Methylene blue was adsorbed effectively on the mesoporous silica films from solutions. The adsorbed amount increased with the increase in the aluminum content of the films, indicating that the added aluminum generated the adsorption sites (probably acidic sites) for methylene blue adsorption. The mesopore surface is not strongly acidic because the protonation of methylene blue did not occur. Adsorbed methylene blue exists as monomers in the mesopore. The dehydration of the films resulted in the aggregation of methylene blue, as evidenced by the visible absorption spectra.

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  • Preparation and characterization of Eu-magadiite intercalation compounds

    N Mizukami, M Tsujimura, K Kuroda, M Ogawa

    CLAYS AND CLAY MINERALS   50 ( 6 ) 799 - 806  2002年12月  [査読有り]

     概要を見る

    The intercalation of europium ions (Eu3+) into the interlayer space of a layered silicate, magadiite, was conducted by ion-exchange reactions between magadiite and europium(III) chloride. X-ray diffraction and elemental analysis results indicated that Eu3+ cations were intercalated into the interlayer space of magadiite. The ion exchange between Eu3+ and Na+ occurred preferentially so that the adsorbed Eu3+ amounts were controlled quantitatively. Thermal transformation of the original layered structure was suppressed by the intercalation of Eu3+. The resulting intercalation compounds exhibited photoluminescence arising from the intercalated Eu3+ The luminescence intensity varied in accordance with the amount of Eu3+ absorbed, suggesting that the self-quenching occurred at higher loading levels. The luminescence intensity was also changed by the heat treatment, corresponding to the change in the surroundings of the Eu3+ adsorbed, induced by the removal of the adsorbed water molecules and the hydroxyl groups of the silicate.

    DOI

  • Effective inclusion of chlorophyllous pigments into mesoporous silica for the energy transfer between the chromophores

    Hiroyasu Furukawa, Kazuyuki Kuroda

    Studies in Surface Science and Catalysis   146   577 - 580  2002年12月  [査読有り]

     概要を見る

    Silica/chlorophyll nanocomposites were synthesized for mimicking partly a light-harvesting apparatus of higher plants. The energy transfer between chlorophyll a and b in alkanediol-modified mesoporous silica was observed by fluorescence measurements. To develop an effective immobilization method for the highly efficient energy transfer, chlorophyll derivatives possessing triethoxysilyl groups were also synthesized and grafted onto FSM-type mesoporous silica. In this case, the energy transfer efficiency was higher than that of the former adsorption way. © 2003 Elsevier Science B.V. All rights reserved.

    DOI

  • Transformation of layered docosyltrimethyl- and docosyltriethylammonium silicates derived from kanemite into precursors for ordered mesoporous silicas

    T Kimura, D Itoh, T Shigeno, K Kuroda

    LANGMUIR   18 ( 24 ) 9574 - 9577  2002年11月  [査読有り]

     概要を見る

    The transformation of layered silicate-surfactant materials derived from a layered polysilicate kanemite into precursors for ordered mesoporous silicas was investigated. When kanemite was allowed to react with docosyltrimethylammonium (C(22)TMA) and docosyltriethylammonium (C(22)TEA) surfactants, layered C(22)TMA- and C(22)TEA-silicate materials were formed. The Si-29 MAS NMR spectra of the layered intermediates clearly indicated that fragmented silicate sheets were present in the silicate-surfactant materials. These layered materials can be transformed by acid treatment into mesostructured precursors with three-dimensional (3-d) silicate networks that afford uniform mesopores after the removal of the surfactants. Ordered mesoporous silica with a 2-d hexagonal structure (FSM-16) can be obtained by using C(22)TEA with a larger headgroup. The results here successfully support the proposed formation mechanism of FSM-16, Which consists of assembling of fragmented layered silicate sheets with surfactants and the subsequent structural transformation to the 2-d hexagonal mesophase.

    DOI

  • Direct silylation of a mesostructured precursor for novel mesoporous silica KSW-2

    T Shigeno, M Nagao, T Kimura, K Kuroda

    LANGMUIR   18 ( 21 ) 8102 - 8107  2002年10月  [査読有り]

     概要を見る

    A mesostructured precursor for KSW-2 with semi-squared mesopores was directly modified with chlorotrimethylsilane and chlorooctyldimethylsilane for the first time. The silylated products were characterized by powder XRD, IR, Si-29 MAS NMR, CHN analysis, and N-2 and water vapor adsorption measurements. Mesoporous silica KSW-2 prepared by calcination of the precursor was also silylated in a similar manner. The mesostructures of the precursor and of KSW-2 were retained after silylation. The characteristics of semi-squared mesopores remarkably changed; the hydrophobicity of the derivatives increased substantially after silylation. The BET surface area, the pore volume, and the width of the semi-squared mesopores decreased after silylation, and the degree of the decrease is larger for the octyldimethylsilyl derivatives than that for the trimethylsilyl derivatives. The numbers of the silyl groups grafted on the directly silylated derivatives are larger than those on the silylated KSW-2, In addition, calcination of the trimethylsilylated products yielded mesoporous silica with the same structure in which the pore wall thickness was increased because of the participation of the silyl groups to the silica network by oxidation.

    DOI

  • Formation of a new crystalline silicate structure by grafting dialkoxysilyl groups on layered octosilicate

    D Mochizuki, A Shimojima, K Kuroda

    JOURNAL OF THE AMERICAN CHEMICAL SOCIETY   124 ( 41 ) 12082 - 12083  2002年10月  [査読有り]

     概要を見る

    Dialkoxydichlorosilanes ((RO)2SiCl2, R = alkyl) react almost completely with interlayer silanol groups in a layered silicate octosilicate to create a new crystalline silicate structure consisting of new five-membered rings arranged regularly on both sides of the silicate layers. The introduction of dialkoxysilyl groups to the interlamellar region of layered silicates with regular reaction sites provides a new methodology for the design and construction of novel crystalline silicate frameworks by a soft chemical route. Copyright © 2002 American Chemical Society.

    DOI PubMed

  • Intercalation of 8-hydroxyquinoline into Al-smectites by solid-solid reactions

    N Khaorapapong, K Kuroda, M Ogawa

    CLAYS AND CLAY MINERALS   50 ( 4 ) 428 - 434  2002年08月  [査読有り]

     概要を見る

    Tris(8-hydroxyquinoline)aluminum(III) complexes (Alq(3)), one of the Molecules Studied most widely for organic light-emitting devices, were formed in the interlayer spaces of smectites by solid-solid reactions between Al-smectites (Al-montmorillonite and Al-synthetic saponite (Sumecton)) and 8-hydroxyquinoline (8Hq) at room temperature. The intercalation of 8-hydroxyquinoline molecules into Al-smectites was demonstrated by powder XRD, FTIR, DTA, TG, TG-MS, and chemical analysis. The coordination of the ligand to the interlayer Al cations was proved by FTIR, UV-Vis, and photoluminescence spectroscopies. The luminescence intensity of Alq(3)-Sumecton was much greater than that of Alq(3)-montmorillonite, and this was ascribed to the very small amount of quenching impurities in Sumecton.

    DOI

  • Conversion of Aurivillius phases Bi(2)ANaNb(3)O(12) (A = Sr or Ca) into the protonated forms of layered perovskite via acid treatment

    W Sugimoto, M Shirata, K Kuroda, Y Sugahara

    CHEMISTRY OF MATERIALS   14 ( 7 ) 2946 - 2952  2002年07月  [査読有り]

     概要を見る

    Protonated forms of layered perovskites were derived from Aurivillius phases, Bi(2)ANaNb(3)O(12) (A = Sr or Ca), by the substitution of bismuth oxide sheets with protons via acid treatment. The conversion into the protonated forms was achieved easily using 6 M HCl at room temperature. Preservation of the structure of the perovskite-like slabs and contraction in the e axis were confirmed by X-ray and electron diffraction analysis as well as by transmission electron microscopy. The compositions of the resulting products were determined to be H-1.8[A(0.8)Bi(0.2)NaNb(3)O(10)] (A = Sr or Ca) by inductively coupled plasma emission spectroscopy and thermogravimetry. The acid-treated product H-1.8[Sr0.8Bi0.2NaNb3O10] was capable of accommodating n-alkylamines in the interlayer space, which is in good agreement with the proposed layered structure.

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  • Surface modification of mesoporous silica to control the states of tris(2,2′-bipyridine)ruthenium(II) cations

    Makoto Ogawa, Kazuyuki Kuroda, Tomoyuki Nakamura

    Chemistry Letters   ( 6 ) 632 - 633  2002年04月  [査読有り]

     概要を見る

    The adsorption and immobilization of tris(2,2′-bipyridine)-ruthenium(II) ([Ru(bpy)3]2+) in mesoporous silicas (C18-FSM) modified by the introduction of aluminum as well as sulfonic acid groups were investigated. The complex was immobilized by the cooperative effects of electrostatic interactions between [Ru(bpy)3]2+cation and sulfonic acid group and the interactions with the phenyl rings of the mesopore surface and the bipyridine rings.

    DOI

  • Preparation of aluminum-containing mesoporous silica films

    M Ogawa, K Kuroda, J Mori

    LANGMUIR   18 ( 3 ) 744 - 749  2002年02月  [査読有り]

     概要を見る

    Aluminum-containing mesoporous silica films were synthesized by the solvent evaporation method using tetraethoxysilane, aluminum tri(sec-butoxide), and octadecyltrimethylammonium chloride as the silica source, the alumina source, and a supramolecular template, respectively. The Al/Si ratios were 0.004-0.031 in the present synthesis. The resulting films with the Al/Si ratios of 0.004, 0.013, and 0.022 were highly transparent in the wavelength region of 200-800 nm. The porous structures of the aluminum-containing films were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption, Although the hexagonal pore arrangements were disordered to some extent by the addition of aluminum, the pore size uniformity was confirmed by the nitrogen adsorption isotherms. The cation exchange ability was evaluated by the adsorption of a cationic azobenzene derivative, p-(w-dimethylhydroxyethylammonioethoxy)-azobenzene bromide, which was not adsorbed effectively on a siliceous mesoporous film. The cation exchange ability of the aluminum-containing mesoporous silica films was semiquantitatively controlled by the amount of added aluminum.

    DOI

  • Structural control of multilayered inorganic-organic hybrids derived from mixtures of alkyltriethoxysilane and tetraethoxysilane

    A Shimojima, K Kuroda

    LANGMUIR   18 ( 4 ) 1144 - 1149  2002年02月  [査読有り]

     概要を見る

    Multilayered inorganic-organic hybrids were prepared by cohydrolysis and polycondensation of alkyltriethoxysilanes (CnTES, n = 8-18) and tetraethoxysilane (TEOS). Thin films were deposited from homogeneous solutions containing the oligomeric species by dip-coating. Self-assembly of co-condensed oligomers into lamellar structures depended essentially on the alkyl chain length of CnTES and the temperature of the solutions. By controlling the solution temperature during the dip-coating process, transparent and highly ordered films were formed from the mixtures of TEOS and CnTES with various alkyl chain lengths. The resulting hybrid materials were structurally different from those derived from CnTES alone and exhibited various interlayer structures depending on the alkyl chain length, which is due to the differences in the arrangements and conformations of the chains.

    DOI

  • Preparation of mesoporous silica films with fully aligned large mesochannels using nonionic surfactants

    H Miyata, T Noma, M Watanabe, K Kuroda

    CHEMISTRY OF MATERIALS   14 ( 2 ) 766 - 772  2002年02月  [査読有り]

     概要を見る

    Mesoporous silica films with uniaxially aligned large-sized mesochannels were prepared using nonionic alkyl poly(ethylene oxide) surfactants and a rubbing-treated polyimide coating. Although the increment of the pore size was small as long as conventional alkylammonium surfactants were used, the use of nonionic surfactants with poly(ethylene oxide) headgroups led to successful enlargement of the mesochannels. The directional distribution of the mesochannels in the films, which is estimated by in-plane X-ray diffraction, was very narrow and was comparable with that in the oriented mesostructured silica films prepared using hexadecyltrimethylammonium chloride as a templating agent. The distribution of the alignment direction of the mesochannels is nearly independent of the nature of the hydrophilic headgroup, but is slightly affected by the alkyl-chain length of the surfactants used. These results indicate that the alignment of the mesochannels is determined by the hydrophobic interactions between the oriented polymer chains of the rubbed polyimide and the surfactant tail groups.

    DOI

  • Conversion of a precursor derived from cage-type and cyclic molecular building blocks into Al-Si-N-C ceramic composites

    H Nakashima, S Koyama, K Kuroda, Y Sugahara

    JOURNAL OF THE AMERICAN CERAMIC SOCIETY   85 ( 1 ) 59 - 64  2002年01月  [査読有り]

     概要を見る

    A precursor derived from (HAIN(i)Pr)(m) and [MeSi(H)NH](n), which mainly consisted of cage-type compounds and cyclic compounds, respectively, was converted into Al-Si-N-C ceramic composites via pyrolysis. A dehydrocoupling reaction between AlH groups and NH groups occurred at low temperatures (less than or equal tosimilar to250degreesC), which mainly accounts for its high ceramic yield (69% up to 900degreesC). At high temperatures (greater than or equal tosimilar to250degreesC), the organic groups were decomposed. The product pyrolyzed at 1350degrees and 1500degreesC under Ar contained a 2H wurtzite-type compound and a beta-Si3N4-type compound, while beta-SiC was clearly detected in addition to these compounds in the product pyrolyzed at 1600degreesC under Ar. On the other hand, the product pyrolyzed at 800degreesC under NH3 and subsequently at 1350degreesC under N-2 consisted of AIN and beta-Sialon.

    DOI

  • Formation of extraordinarily large nanosheets from K4Nb6O17 crystals

    N Miyamoto, H Yamamoto, R Kaito, K Kuroda

    CHEMICAL COMMUNICATIONS   2 ( 20 ) 2378 - 2379  2002年  [査読有り]

     概要を見る

    Exfoliated K4Nb6O17 bilayer nanosheets in extraordinarily large size (ca. 100 mum) were prepared by the direct reaction of K4Nb6O17.3H(2)O crystals with an aqueous solution of propylamine; the size was extremely larger than that of exfoliated nanosheets (several mum) reported previously.

    DOI

  • Intercalation of cationic phthalocyanines into layered titanates and control of the microstructures

    R Kaito, N Miyamoto, K Kuroda, M Ogawa

    JOURNAL OF MATERIALS CHEMISTRY   12 ( 12 ) 3463 - 3468  2002年  [査読有り]

     概要を見る

    Two cationic phthalocyanines (Pc), a tetravalent Alcian Blue pyridine variant (ABpy(4+)) and a monovalent iron(III) phthalocyanine (FePc+), were intercalated into two layered titanates derived from Na2Ti3O7 and Cs(x)Ti(2-x/4)square(x/4)O(4) (square = vacancy, x = 0.7) by using the corresponding propylammonium titanates as the intermediates for guest displacement reactions. When Na2Ti3O7 was used as a host, segregation occurred in the products, since it has a relatively higher layer charge density; some interlayer spaces accommodated Pc, but the others contained propylammonium cations. On the other hand, Pc cations were homogeneously intercalated into the interlayer spaces of Ti(2-x/4)square(x/4)O(4) layers. ABpy(4+) formed agglomerates in the gallery between Ti(2-x/4)square(x/4)O(4) layers, whereas FePc+ was distributed molecularly. In the ABpy-Ti(2-x/4)square(x/4)O(4) system, further ABpy(4+) was added or any remaining propylammonium cations were removed by thermal treatment under reduced pressure in order to vary the microstructure, which resulted in the formation of higher aggregated states of ABpy(4+). Electron transfer from FePc+ to Ti(2-x/4)square(x/4)O(4) induced by visible light irradiation was observed for FePc-Ti(2-x/4)square(x/4)O(4) by fluorescence measurements.

    DOI

  • Incorporation of tris(2,2′-bipyridine)ruthenium(II) cations ([Ru(bpy)3]2+) into a mesoporous silica

    Makoto Ogawa, Tomoyuki Nakamura, Jun Ichi Mori, Kazuyuki Kuroda

    Microporous and Mesoporous Materials   48 ( 1-3 ) 159 - 164  2001年11月  [査読有り]

     概要を見る

    The luminescence characteristics of tris(2.2&#039;-bipyridine)ruthenium(II) ([Ru(bpy)3]2+) adsorbed on a mesoporous silica was investigated. The adsorption of the complex cation into the mesoporous silica was conducted by the reaction using a dimethylformamide solution of [Ru(bpy)3]2+chloride hexahydrate. The amount of adsorbed [Ru(bpy)3]2+was controlled by changing the concentration of the solution. When the samples were dehydrated, the adsorbed [Ru(bpy)3]2+ions aggregated to cause self-quenching of the luminescence. The luminescence was intensified dramatically upon hydration of the samples, indicating that the aggregated [Ru(bpy)3]2+ions were dispersed in the mesopore to suppress the self-quenching. The luminiscence characteristics of the adsorbed [Ru(bpy)3]2+significantly changed upon washing, showing the possible role of the co-adsorbed Cl-ions. © 2001 Elsevier Science B.V. All rights reserved.

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  • Preparation and HREM characterization of a protonated form of a layered perovskite tantalate from an Aurivillius phase Bi2SrTa2O9 via acid treatment

    Y Tsunoda, M Shirata, W Sugimoto, Z Liu, O Terasaki, K Kuroda, Y Sugahara

    INORGANIC CHEMISTRY   40 ( 23 ) 5768 - 5771  2001年11月  [査読有り]

     概要を見る

    An Aurivillius phase, Bi2SrTa2O9, which consists of perovskite-like stabs and bismuth oxide sheets, was treated with 3 M hydrochloric acid for 72 h, and the resultant product was characterized. Scanning electron microscopy investigation indicated that no morphological change occurred during the acid treatment. X-ray diffraction (XRD) analysis revealed that the product exhibited tetragonal symmetry with a = 0.391 +/- 0.004 run and c = 0.98 +/- 0.01 run, and the a parameter is consistent with a typical value for cubic perovskite oxides. High-resolution electron microscopy (HREM) observations along both [001] and [010] showed that the structure of the perovskite-like slabs in Bi2SrTa2O9 was retained after the acid treatment. The compositional analyses revealed the loss of a large portion of bismuth and a part of strontium (present in the bismuth oxide sheets due to B &lt;----&gt; Sr disorder) and the introduction of protons. These observations indicate that the bismuth oxide sheets in Bi2SrTa2O9 were selectively leached and that protons were introduced into the interlayer space to form a protonated layered perovskite, H-1.8[Sr0.8Bi0.2Ta2O7]. Though diffraction techniques (XRD and electron diffraction) demonstrated that an average structure of H-1.8[Sr0.8Bi0.2Ta2O7] consisted of perovskite-like slabs stacked without displacement, HREM observation along [010] demonstrated that both a simple stacking sequence without displacement (P-type) and a stacking sequence with a relative displacement by (a + b)/2 (I-type) were present in H-1.8[Sr0.8Bi0.2Ta2O7].

    DOI PubMed

  • Intercalation of nitroanilines into kaolinite and second harmonic generation

    R Takenawa, Y Komori, S Hayashi, J Kawamata, K Kuroda

    CHEMISTRY OF MATERIALS   13 ( 10 ) 3741 - 3746  2001年10月  [査読有り]

     概要を見る

    Kaolinite intercalates ortho- and para-nitroanilines (oNA and pNA) between the layers whereas meta-nitroaniline (mNA) is not intercalated. para-Nitroaniline takes a monolayer arrangement with the long axis inclined to the layers of kaolinite. oNA molecules also take a monolayer arrangement though the orientation is not well ordered. Kaolinite-pNA and -oNA intercalation compounds exhibit second harmonic generation, which is evaluated quantitatively by the second-harmonic wave generated with evanescent wave (SHEW) method. This indicates noncentrosymmetric arrangements of pNA and oNA, and such orientations are induced by the asymmetric environment of the interlayer region of kaolinite.

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  • Interlamellar esterification of H-magadiite with aliphatic alcohols

    Y Mitamura, Y Komori, S Hayashi, Y Sugahara, K Kuroda

    CHEMISTRY OF MATERIALS   13 ( 10 ) 3747 - 3753  2001年10月  [査読有り]

     概要を見る

    Magadiite, a layered sodium polysilicate, was organically modified by esterification of interlayer silanol groups with various aliphatic alcohols. Methanol was directly reacted with H-magadiite (acid-treated magadiite) by refluxing. The methanol-treated product showed an increase in the basal spacing and the C-13 NMR signals due to methyl groups. The H-2 NMR spectrum of CD3OD-treated H-magadiite showed Pake doublet patterns of quadrupole coupling constants of 43 and 48 kHz and asymmetry factors of 0, indicating the fixation of the C-O axis. When aliphatic alcohols with the carbon chain length longer than 4 were used, an H-magadiite/N-methylformamide (NMF) intercalation compound was used as an intermediate for esterification. The basal spacing of butanol-treated H-magadiite was 1.40 nm, the value of which was smaller than that of H-magadiite/NMF (1.63 nm) and larger than that of H-magadiite (1.15 nm). C-13 spin-lattice relaxation times (T-1) of butyl groups showed a low mobility of the alpha carbon. Other alcohols (CnH2n+1OH (n = 2-16) and (CH3)(3)COH) were also reacted with the silanol groups. The differential thermal analysis (DTA) curves of the products showed exothermic peaks. The alkyl chains are apparently lying parallel to the inner surface because almost constant basal spacings were observed despite the variation in the alkyl chain length. The butanol-treated H-magadiite was dispersed in toluene and cast, resulting in the formation of a transparent nanocomposite film.

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  • Preparation and pyrolysis of a blended precursor possessing Ti-N and Al-N bonds

    F Cheng, Y Sugahara, K Kuroda

    APPLIED ORGANOMETALLIC CHEMISTRY   15 ( 8 ) 710 - 716  2001年08月  [査読有り]

     概要を見る

    The preparation and pyrolysis of a blended precursor possessing Ti-N and Al-N bonds were investigated. The precursor was prepared by mixing (HAIN(i)Pr)(n), whose main component was a cage-type compound, and an aminolysis product of Ti(NMe2)(4) with MeHNCH2CH2NHMe with a molar ratio of Ti:Al = 2:1. IR analysis of the products pyrolyzed under NH3-N-2 indicated that a large proportion of the organic groups in the precursor were removed by an amine-exchange reaction during the pyrolysis under NH3; thus, the products contained only a small amount of carbon. On the contrary, a considerable amount of carbon was present in the product pyrolyzed under Ar. Composites consisting of AIN and an NaCl-type compound were obtained after pyrolysis of the precursor under both NH3-N-2 and Ar. The composition of the NaCl-type compound depended significantly on the pyrolysis atmosphere. Copyright (C) 2001 John Wiley & Sons, Ltd.

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  • Effective inclusion of chlorophyllous pigments into mesoporous silica modified with α,ω-diols

    S. Murata, H. Furukawa, K. Kuroda

    Chemistry of Materials   13 ( 8 ) 2722 - 2729  2001年08月  [査読有り]

     概要を見る

    FSM-type mesoporous silica modified with various diols was utilized as an inorganic medium for immobilizing chlorophyll a (Chl a) without denaturation. The energy transfer from Chl b to Chl a in the mesopores was also observed for the first time. Silanol groups on the mesoporous silica were esterified with diols, and this was confirmed by 13C MAS NMR, IR, N2 adsorption, and elemental analysis. The suppression of the pigment degradation in modified FSM was confirmed by both visible absorption spectroscopy of the FSM/Chl compounds and the analysis of the extracts from FSM/Chl by high-performance liquid chromatography. The fluorescence emission bands of Chl a and Chl b in FSM modified with 1,6-hexanediol appeared at 672 and 654 nm, respectively. In the FSM/Chl containing both Chl a and Chl b, the emission band due to Chl b was decreased whereas the band due to Chl a was increased. This is in sharp contrast to the emission spectrum of an acetone solution containing both of Chls, implying energy transfer from Chl b to Chl a in modified mesoporous silica.

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  • Solid-state intercalation of 4,4′-bipyridine and 1,2-di(4-pyridine) ethylene into the interlayer spaces of Co(II)-, Ni(II)- and Cu(II)-montmorillonites

    Nithima Khaorapapong, Kazuyuki Kuroda, Hideo Hashizume, Makoto Ogawa

    Applied Clay Science   19 ( 1-6 ) 69 - 76  2001年07月  [査読有り]

     概要を見る

    Intercalation of two diimines, 4,4′-bipyridine (4BPY) and 1,2-di(4-pyridine)ethylene (DPE), into the interlayer spaces of cobalt(II)-, nickel(II)- and copper(II)-montmorillonites by solid-solid reactions was investigated. The successful intercalation of these compounds through coordination to the interlayer exchangeable cations was confirmed by powder X-ray diffraction, infrared spectroscopy, elemental (CHN) analysis, and thermal analysis of the products. The presented solid-state intercalation of bidentate bridging ligands and in situ complex formation in the interlayer spaces of montmorillonite is a feasible way to prepare clay-coordination polymer-intercalation compounds, which cannot be obtained in conventional ion exchange reactions. © 2001 Elsevier Science B.V. All rights reserved.

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  • Intercalation of a cationic cyanine dye into the layer silicate magadiite

    N Miyamoto, R Kawai, K Kuroda, M Ogawa

    APPLIED CLAY SCIENCE   19 ( 1-6 ) 39 - 46  2001年07月  [査読有り]

     概要を見る

    A cationic cyanine dye, 1,1 ' -diethyl-2,2 ' -cyanine (denoted as PIG), was intercalated into the layer silicate magadiite by ion-exchange between an aqueous PICBr solution and Na-magadiite or dodecyltrimethylammonium-exchanged magadiite. The formation of the intercalation compounds was probed by XRD, IR and chemical analysis. The basal spacing, the adsorbed amount of PIC, and the spectroscopic features of the products were determined. UV-Vis spectra revealed that different types of PIC aggregates were formed in the products synthesized from Na-magadiite and dodecyltrimethylammonium-exchanged magadiite. The state of PIC was also affected by the presence of alkylammonium ions. The microstructure of dye aggregates in the present systems was different from the typical structure of other systems such as the J-aggregates on the surface of AgBr crystals. (C) 2001 Elsevier Science B.V. All rights reserved.

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  • Photocontrol of the basal spacing of azobenzene-magadiite intercalation compound

    M. Ogawa, T. Ishii, N. Miyamoto, K. Kuroda

    Advanced Materials   13   1107 - 1109  2001年07月  [査読有り]

     概要を見る

    The intercalation of a cationic azobenzene derivative into the interlayer space of magadiite was achieved. The spectral properties as well as the X-ray diffraction results reveal that the adsorbed azo cations form head-to-head aggregates in the interlayer space. The basal spacing of the compound changed reversibly upon photoisomerization of the intercalated azobenzene.

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  • Intercalation of an amphiphilic azobenzene derivative into the interlayer space of a layered silicate, magadiite

    M Ogawa, M Yamamoto, K Kuroda

    CLAY MINERALS   36 ( 2 ) 263 - 266  2001年06月  [査読有り]

     概要を見る

    Intercalation of an ammonium amphiphile having an azobenzene chromophore, 4-dodecyloxy-4'-(trimethylammoniopentyloxy)azobenzene and 4-(omega -trimethylammoniodecyloxy)-p'-(octyloxy)azobenzene bromide, into the layered silicate magadiite (ideal formula Na2Si14O29. nH(2)O) was carried out by a conventional ion exchange reaction in an aqueous medium. An intercalation compound with the ideal formula {(C(12)AzoC(5)N(+))(1.4)H-0.6. Si14O29. nH(2)O} was obtained. Based on the change in the basal spacing (to 4.21 nm) after the reaction and the visible absorption spectrum of the product, the intercalated azo dyes appear to form a J-aggregate in the interlayer space of magadiite. Under W and visible light irradiation, the intercalated azo chromophore exhibited reversible trans-cis isomerization in the interlayer space of magadiite. This is the first successful report of photochemical reactions of guest species in the interlayer space of magadiite.

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  • Preparation of a kaolinite-nylon 6 intercalation compound

    A Matsumura, Y Komori, T Itagaki, Y Sugahara, K Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   74 ( 6 ) 1153 - 1158  2001年06月  [査読有り]

     概要を見る

    A kaolinite-nylon 6 intercalation compound was prepared by the polymerization of 6-aminohexanoic acid (AHA) in the interlayer space of kaolinite. The intercalation of AHA was achieved by a guest displacement reaction using a kaolinite-methanol intercalation compound as an intermediate. After AHA dissolved in a mixed solvent of methanol and water (1:3) was added to a kaolinite-methanol intercalation compound, the mixture was stirred for 3 h. The basal spacing of the product increased to 1.23 nm, indicating the intercalation of AHA molecules with a monolayer arrangement between the layers of kaolinite. AHA was polymerized by a heat treatment at 250 degreesC for 1 h under a nitrogen flow. Although the basal spacing of the heat-treated product slightly decreased to 1.16 nm, the spacing was larger than those of kaolinite and the kaolinite-methanol intermediate. The formation of a kaolinite-nylon 6 intercalation compound was confirmed by the appearance of IR bands due to amide I (1637 cm(-)1) and amide II (1550 cm(-1)).

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  • Film to fiber transformation of preferentially aligned mesostructured silica

    Hirokatsu Miyata, Kazuyuki Kuroda

    Advanced Materials   13   558 - 561  2001年04月  [査読有り]

     概要を見る

    A new method for fabricating fibrous mesostructured silica on a glass substrate using rubbing-treated polyimide film is presented. By using this method, both continuous films and fibers with preferred mesochannel orientation can be formed. Self-supported fiber-like silica prepared by this method have smooth surfaces without branching or connecting.

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  • Immobilization of chlorophyll derivatives into mesoporous silica and energy transfer between the chromophores in mesopores

    Hiroyasu Furukawa, Tadashi Watanabe, Kazuyuki Kuroda

    Chemical Communications   1 ( 19 ) 2002 - 2003  2001年  [査読有り]

     概要を見る

    Chlorophyll derivatives possessing triethoxysilyl groups have been synthesized for the first time and grafted on mesoporous silica to construct an efficient energy transfer system between the chromophores. © 2001 Royal Society of Chemistry.

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  • Preparation of kaolinite-nylon6 composites by blending nylon6 and a kaolinite-nylon6 intercalation compound

    T Itagaki, A Matsumura, M Kato, A Usuki, K Kuroda

    JOURNAL OF MATERIALS SCIENCE LETTERS   20 ( 16 ) 1483 - 1484  2001年  [査読有り]

     概要を見る

    Blended composites were prepared by employing nylon6 as a polymer matrix and a kaolinite-nylon6 intercalation compound or kaolinite as an inorganic filler. An increase in tensile moduli of the composites was confirmed and the layered structure was retained. Results suggested for larger interfaces between the kaolinite surface and polymers higher dispersion of kaolinite crystallites in polymers.

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  • Synthesis of layered inorganic-organic nanocomposite films from mono-, di-, and trimethoxy(alkyl)silane-tetramethoxysilane systems

    A. Shimojima, N. Umeda, K. Kuroda

    Chemistry of Materials   13 ( 10 ) 3610 - 3616  2001年  [査読有り]

     概要を見る

    Transparent thin films of layered inorganic-organic nanocomposites were prepared by the sol-gel reactions of alkyldimethylmethoxysilane, alkylmethyldimethoxysilane, and alkyltrimethoxysilane in the presence of tetramethoxysilane followed by spin-coating. The macroscopic homogeneity and the nanostructural ordering of the films were strongly affected by the degree of polycondensation in the precursor solutions. The formation of siloxane networks containing organosiloxane units was confirmed by 29Si MAS NMR, suggesting that the structure of the inorganic-organic interface can be designed at a molecular level by the functionalities in the alkylmethoxysilanes used. On the other hand, the 29Si NMR spectra of the precursor solutions showed that the monomeric species almost disappeared and that co-condensed oligomers were formed at the initial stages of the reactions. In the cases of mono- and dimethoxysilanes, the ability to form ordered structures depends largely on the co-condensation with tetramethoxysilane in the precursor solutions.

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  • Synthesis of silylated derivatives of a layered polysilicate kanemite with mono-, di-, and trichloro(alkyl)silanes

    A. Shimojima, D. Mochizuki, K. Kuroda

    Chemistry of Materials   13 ( 10 ) 3603 - 3609  2001年  [査読有り]

     概要を見る

    Interlayer modification of a layered polysilicate kanemite was performed by silylation with mono-, di-, and trichloro(alkyl)silanes. The introduction of silyl groups into the interlayer region was confirmed by XRD, IR, 13C NMR, and 29Si NMR. The layered structures of the silylated products were confirmed by swelling behavior upon adsorption of n-alkyl alcohols. The amounts of attached alkylsilyl groups varied with the number of functional groups as well as the alkyl chain length in the silylating agents. The products modified with alkyltrichlorosilanes exhibited various interlayer structures due to the different arrangements and/or conformations of the alkyl chains, depending on the chain lengths. The BET surface areas were relatively large (up to ∼480 m2 g-1) when short-chain alkyltrichlorosilanes were used, and decreased substantially to nonporous structures with increasing chain length. In addition to the inherent six-membered rings in the single layered silicate sheets of kanemite, new five- and six-membered rings were formed onto the silicate frameworks when dichloro- and trichlorosilanes were used for silylation. This leads to a new method for constructing novel organosilicate nanomaterials utilizing layered silicates.

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  • Synthesis of a kaolinite-poly(β-alanine) intercalation compound

    T. Itagaki, Y. Komori, Y. Sugahara, K. Kuroda

    Journal of Materials Chemistry   11 ( 12 ) 3291 - 3295  2001年  [査読有り]

     概要を見る

    A kaolinite-poly(β-alanine) intercalation compound (kaolinite/poly(β-alanine)) was synthesized by in-situ polycondensation of preintercalated β-alanine, which is an initial step toward the extension of the variety of host materials for polymer-clay nanocomposites. β-Alanine was intercalated into kaolinite by a displacement method using kaolinite/ammonium acetate as the intermediate. Zwitterionic β-alanine was ordered in a monolayer arrangement between the layers, which was confirmed by powder XRD, IR and NMR. Although β-alanine was mostly polymerized by thermal treatment of kaolinite/β-alanine at 250°C for 10 h under an N2atmosphere, a part of the guest species was decomposed. Kaolinite/poly(β-alanine) had a higher thermal stability than bulk poly(β-alanine), as evidenced by TG-DTA.

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  • Uni-directional orientation of cyanine dye aggregates on a K4Nb6O17 single crystal: Toward novel supramolecular assemblies with three-dimensional anisotropy

    N. Miyamoto, K. Kuroda, M. Ogawa

    Journal of the American Chemical Society   123 ( 28 ) 6949 - 6950  2001年  [査読有り]

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  • Immobilization of photosynthetic pigments into silica-surfactant nanocomposite films

    H Hata, T Kimura, M Ogawa, Y Sugahara, K Kuroda

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   19 ( 1-3 ) 543 - 547  2000年12月  [査読有り]

     概要を見る

    Highly transparent silica-surfactant nanocomposite films containing photosynthetic pigments have been successfully formed through the solubilization of chlorophyll a (Chl a) into surfactant micelles. The UV-vis absorption spectra indicated that a large amount of Chl a were transformed into pheophytin a in the films. These photosynthetic pigments were well dispersed in the surfactant assemblies and their chlorin rings were exposed to the surface of silica layers. Even under an air atmosphere, the photostability of immobilized pigments was largely improved in comparison with that in a homogeneous Chl a solution. Because both Chl a and pheophytin a molecules are effective for the photosensitive charge separation, the present film system is very suitable for heterogeneous immobilizing media for photosynthetic pigments from the viewpoint of in vitro biomimetic devices for solar energy conversion.

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  • Formation of novel ordered mesoporous silicas with square channels and their direct observation by transmission electron microscopy

    Tatsuo Kimura, Takayuki Kamata, Minekazu Fuziwara, Yuri Takano, Mizue Kaneda, Yasuhiro Sakamoto, Osamu Terasaki, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Angewandte Chemie - International Edition   39   3855 - 3859  2000年11月  [査読有り]

     概要を見る

    The layered polysilicate kanemite can be used to synthesize the novel mesoporous silica KSW-2 (see picture), which contains square channels. The individual silicate sheets of kanemite are bent during the gradual leaching of hexadecyltrimethyl-ammonium (C16TMA) surfactants from a layered C16TMA-kanemite complex.

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  • Lamellar hexadecyltrimethylammonium silicates derived from kanemite

    T Kimura, D Itoh, N Okazaki, M Kaneda, Y Sakamoto, O Terasaki, Y Sugahara, K Kuroda

    LANGMUIR   16 ( 20 ) 7624 - 7628  2000年10月  [査読有り]

     概要を見る

    Lamellar organoammonium silicates with variable silicon environments have been synthesized by the reaction of a layered polysilicate kanemite with aqueous solutions of hexadecyltrimethylammonium (C(16)TMA) chloride. While the structure of kanemite is composed of only Q(3) silicate species ((SiO)(3)SiO), SiO4 units with both Q(3) and Q(4) ((SiO)(4)Si) environments were present in the silicate frameworks of the lamellar C(16)TMA silicates. The Q(4) species mainly formed by intralayer condensation of the Q(3) species in the individual silicate sheets in kanemite rather than by interlayer condensation between the adjacent sheets. The intralayer condensation can be suppressed by lowering the reaction temperature and/or shortening the reaction time, which results in the relative retention of the silicate framework of kanemite in the lamellar C(16)TMA silicates.

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  • Luminescence of tris(2,2′-bipyridine)ruthenium(II) cations ([Ru(bpy)<inf>3</inf>]2+) adsorbed in mesoporous silica

    Makoto Ogawa, Tomoyuki Nakamura, Jun Ichi Mori, Kazuyuki Kuroda

    Journal of Physical Chemistry B   104   8554 - 8556  2000年09月  [査読有り]

     概要を見る

    The adsorption of a cationic luminescence probe, tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)3]2+), into a mesoporous silica was investigated in order to understand the nature of mesoporous silicas as immobilizing media for organic guest species. The adsorption of the probe into the mesoporous silica was conducted by the reaction using a dimethylformamide solution of [Ru(bpy)3]2+ chloride. The adsorbed amount of [Ru(bpy)3]2+ was controlled by changing the concentration of the solutions. When the samples were dehydrated, the adsorbed [Ru(bpy)3]2+ ions aggregated to cause self-quenching of the luminescence. The luminescence was intensified dramatically upon hydratiori of the samples, indicating that the aggregated [Ru(bpy)3]2+ ions were dispersed in the mesopore to suppress the self-quenching. © 2000 American Chemical Society.

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  • Effective adsorption of chlorophyll a by FSM-type mesoporous silica modified with 1,4-butanediol

    S Murata, H Hata, T Kimura, Y Sugahara, K Kuroda

    LANGMUIR   16 ( 18 ) 7106 - 7108  2000年09月  [査読有り]

     概要を見る

    Surface silanol groups of FSM-type mesoporous silica were modified with 1,4-butanediol, and the esterified material was successfully used as the adsorbent to accommodate chlorophyll alpha molecules. Pheophytinization was effectively suppressed by the presence of the surface organic groups grafted onto the mesoporous silica, whereas pheophytinization occurred in unmodified mesoporous silica.

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  • Modification of the interlayer surface of kaolinite with methoxy groups

    Y Komori, H Enoto, R Takenawa, S Hayashi, Y Sugahara, K Kuroda

    LANGMUIR   16 ( 12 ) 5506 - 5508  2000年06月  [査読有り]

     概要を見る

    The elucidation of the structure of the intermediate, methanol-treated kaolinite, is significant for the understanding of the interlayer surface reactions of kaolinite. In this study, methanol-treated kaolinite prepared at room temperature is characterized. Evidence is given concerning the methoxy modification of the AlO2(OH)4 layers of kaolinite.

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  • Interlamellar grafting of γ-methacryloxypropylsilyl groups on magadiite and copolymerization with methyl methacrylate

    Kei Isoda, Kazuyuki Kuroda, Makoto Ogawa

    Chemistry of Materials   12 ( 6 ) 1702 - 1707  2000年06月  [査読有り]

     概要を見る

    Organically modified magadiite has been prepared by grafting γ-methacryloxypropylsilyl (γ-MPS) groups to the interlayer surface. γ-Methacryloxypropyltrimethoxysilane as silylating reagent was reacted with dodecyltrimethylammonium-exchanged magadiite. Formation of the organic derivatives of magadiite was confirmed by XRD, IR, 29Si CP-MAS NMR, and 13C CP-MAS NMR. Copolymerization of the grafted groups with methyl methacrylate yielded a novel type of layered silicate-organic intercalation compound with covalently bound polymers in the interlayer space. This is in contrast to conventional clay-polymer systems where ionic interactions between silicates and organic modifiers are dominant.

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  • Incorporation of tris(2,2′-bipyridine)ruthenium(II) in a synthetic swelling mica with poly(vinylpyrrolidone)

    Makoto Ogawa, Masashi Tsujimura, Kazuyuki Kuroda

    Langmuir   16 ( 9 ) 4202 - 4206  2000年05月  [査読有り]

     概要を見る

    Tris(2,2′-bipyridine)ruthenium(II) ([Ru(bpy)3]2+)-fluortetrasilicic mica-poly(vinylpyrrolidone) intercalation compounds were prepared by the intercalation of poly(vinylpyrrolidone) into the presynthesized [Ru(bpy)3]2+-fluortetrasilicic mica intercalation compounds. The formation of the intercalation compounds was confirmed by the expansion of the interlayer space as well as the spectroscopic observations. Intercalation compounds with variable chemical compositions have been prepared, and the effect of the distribution of the intercalated [Ru(bpy)3]2+ on the luminescence has been discussed. The luminescence probe can be utilized for the study of clay-polymer interactions.

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  • Synthesis of a soluble precursor possessing an Nb-N backbone structure and its pyrolytic conversion into niobium-based ceramics

    F Cheng, Y Sugahara, K Kuroda

    BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN   73 ( 5 ) 1299 - 1305  2000年05月  [査読有り]

     概要を見る

    Synthesis and pyrolysis of a soluble precursor possessing an Nb-N backbone structure were investigated. The precursor was prepared by aminolysis reaction of tetrakis(diethylamido)niobium with isopropylamine. The precursor was soluble in benzene, and had a polymeric structure possessing Nb-N-Nb imido-bridges. The precursor was pyrolyzed under NH3-N-2 (at 600 degrees C for 2 h under NH3 and subsequently at 1350 degrees C for 8 h under N-2) and Ar (at 1500 degrees C for 2 h) atmospheres. delta-NbN was obtained as a main crystalline phase after the pyrolysis of the precursor under NH3-N-2 whereas pyrolysis of the precursor under Ar led to the formation of NbC as the only crystalline phase. More than 90% of niobium which was present in the precursor remained in both of the pyrolyzed products.

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  • Adsorption and aggregation of a cationic cyanine dye on layered clay minerals

    N Miyamoto, R Kawai, K Kuroda, M Ogawa

    APPLIED CLAY SCIENCE   16 ( 3-4 ) 161 - 170  2000年03月  [査読有り]

     概要を見る

    The adsorption and aggregation of a cationic cyanine dye, 1,1'-diethyl-2,2'-cyanine (pseudoisocyanine; abbreviated as PIC), on various clays have been investigated. The PIC formed J-aggregates on Na-montmorillonite and synthetic Na-fluor-tetrasilicic mica (TSM), while they distributed molecularly on synthetic Na-saponite and synthetic Na-hectorites. The particle size of the clays was considered to be a dominant factor to control the aggregation of PIC. The J-aggregate formation was suppressed when tetramethylammonium-montmorillonite was employed as a host material. Ethylene glycol in the suspension was also responsible for the suppression of J-aggregate formation of PIC. Thus, the aggregation of PIC was effectively controlled by the species surrounding the PIC cations as well as the nature of clays. (C) 2000 Elsevier Science B.V. All rights reserved.

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  • Solid state intercalation of 4,4'-bipyridine into the interlayer space of montmorillonites

    Nithima Khaorapapong, Kazuyuki Kuroda, Hideo Hashizume, Makoto Ogawa

    Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals   341   351 - 356  2000年01月  [査読有り]

     概要を見る

    Intercalation of 4,4&#039;-bipyridine into the interlayer spaces of cobalt(II), nickel(II) and copper(II)-montmorillonites by solid-solid reactions was investigated. The successful intercalation of 4,4-bipyridine and the complex formation in the interlayer spaces of montmorillonites was confirmed by powder XRD (the change in the basal spacings) as well as IR and the thermal analysis of the products. © 2000 OPA (Overseas Publishers Association) N.V. Published by license under the Gordon and Breach Science Publishers imprint.

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  • Orientation of guest molecules and formation of mesoporous silica induced by layered silicate-organic interactions

    Kazuyuki Kuroda

    Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals   341   283 - 288  2000年01月  [査読有り]

     概要を見る

    This paper summarizes some of our recent results on layered silicate-organic systems. Unique nanomaterials are prepared by the interactions between layered silicates and organic species. The structural control of guest molecules and the structural transformation of host silicates have been accomplished by choosing appropriate layered silicates. One way for specific orientation of guest molecules is to utilize a layered clay mineral kaolinite. A kaolinite-p-nitroaniline intercalation compound was successfully prepared by using a kaolinite-methanol intercalation compound as a versatile intermediate. Kanemite, a layered polysilicate composed of single layered silicate sheets, was structurally transformed on intercalation of organoammonium ions, which produced a mesostructured precursor for ordered mesoporous silica.

    DOI

  • Aluminium-containing mesoporous silica films as nano-vessels for organic photochemical reactions

    M Ogawa, K Kuroda, J Mori

    CHEMICAL COMMUNICATIONS   ( 24 ) 2441 - 2442  2000年  [査読有り]

     概要を見る

    The adsorption of a cationic azobenzene derivative into both siliceous and aluminium containing mesoporous silica films has been investigated; photoisomerization was found to occur in the temperature range 80-300 K and the mesoporous aluminium containing silica films were proved to be useful reaction media to immobilize organic photochromic species.

    DOI

  • Adsorption of zinc-metallated chlorophyllous pigments on FSM-type mesoporous silica

    Hiroyasu Furukawa, Kazuyuki Kuroda, Tadashi Watanabe

    Chemistry Letters   ( 11 ) 1256 - 1257  2000年  [査読有り]

     概要を見る

    The spectroscopic properties of zinc chlorophyll (Zn-Chl) derivatives within FSM-type mesoporous silica were examined. Visible absorption and resonance Raman spectroscopies suggest that chlorophyllous pigments are successfully incorporated and form hydrogen bonds to silanol groups on silica.

    DOI

  • Novel layered silica/organic polymer hybrid films with the interface linked by Si-C bonds

    Atsushi Shimojima, Kazuyuki Kuroda

    Chemistry Letters   ( 11 ) 1310 - 1311  2000年  [査読有り]

     概要を見る

    Inorganic-organic hybrids films composed of alternating layers of siloxane network and organic polymer assemblies linked by Si-C bonds have been prepared via co-hydrolysis and polycondensation of alkenyltriethoxysilane-tetraethoxysilane mixtures followed by organic polymerization, providing a new methodology for the design and construction of inorganic-organic nanostructured materials.

    DOI

  • Characterization of silanol groups in protonated magadiite by 1H and 2H solid-state nuclear magnetic resonance

    Yoshihiko Komori, Masaki Miyoshi, Shigenobu Hayashi, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Clays and Clay Minerals   48 ( 6 ) 632 - 637  2000年  [査読有り]

     概要を見る

    Silanol groups in protonated magadiite (H-magadiite) were characterized by 1H and 2H solid-state nuclear magnetic resonance (NMR). H-magadiite and deuterated (D) magadiite were synthesized by the treatment of Na-rich magadiite with 0.2 N HCl and 0.2 N DCl, respectively. In the 1H NMR spectrum measured at room temperature, silanol groups of H-magadiite showed two signals at 3.75 and 5.70 ppm, indicating that two types of silanol groups were present. The ratio of silanol groups associated with strong hydrogen bonding (5.70 ppm) to those with weaker hydrogen bonding (3.75 ppm) was 2 to 1. The 2H NMR spectra of deuterated magadiite were measured in the temperature range from 150 to 440 K. In the spectra measured at temperatures below 294 K, silanol groups showed Pake doublet patterns. These patterns were composed of two components corresponding to the two types of silanol groups shown in the 1H NMR analysis. Both silanol groups produced wobbling motions with increasing temperature. Above 294 K, the profile of the Pake doublet pattern was transformed gradually to a near triangular pattern, indicating that the silanol groups underwent other motions also, such as a two-site jump.

    DOI

  • Pyrolysis of poly(isopropyliminoalane) to aluminum nitride

    Yasuo Saito, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Journal of the American Ceramic Society   83   2436 - 2440  2000年01月  [査読有り]

     概要を見る

    The pyrolysis processes of poly(isopropyliminoalane) ((HAlNiPr)n) were investigated, using mass spectrometry to analyze the gases and infrared spectroscopy to analyze the residual solids. The major mass loss (in the temperature range of 240°-540 °C) consisted of two different pyrolysis stages. At the first stage (240°-320 °C), (HAlNiPr)6 was detected continuously as a gas, and the precursor was converted to a cross-linked structure. A polymerization mechanism without a release of organic compounds has been proposed, and the formation of (HAlNiPr)6 during polymerization (besides its evaporation) has been suggested. The second stage (320°-560 °C) involved the formation of various organic compounds, and radical processes for their formation were proposed.

    DOI

  • Photochromism of an azobenzene in a nanoporous silica film

    M. Ogawa, J. Mori, K. Kuroda

    Studies in Surface Science and Catalysis   129   865 - 870  2000年01月  [査読有り]

     概要を見る

    The incorporation of a cationic azobenzene derivative, p-(ω-dimethylethanolammonioethoxy)-azobenzene bromide, into nanoporous silica films and the photochemical reactions of the adsorbed dye were investigated. The nanoporous silica films were prepared from tetramethoxysilane and octadecyltrimethylammonium chloride by the rapid solvent evaporation method which we have reported previously. The adsorption of the cationic azo dye was conducted by casting an ethanol solution of the dye onto the nanoporous silica films. Upon UV light irradiation, frans-azobenzene isomerized photochemically to the cis-form and photochemically formed cis-form turned back to the trans-form upon visible light irradiation. The nanoporous silica films were proved to be an excellent reaction media to immobilize organic photocromic species. © 2000 Elsevier Science B.V. All rights reserved.

  • Aggregation of a cationic cyanine dye intercalated in the interlayer space of a layered titanate Na2Ti3O7

    Nobuyoshi Miyamoto, Kazuyuki Kuroda, Makoto Ogawa

    Molecular Crystals and Liquid Crystals Science and Technology Section A: Molecular Crystals and Liquid Crystals   341   259 - 264  2000年  [査読有り]

     概要を見る

    A cationic cyanine dye, 1,1′-diethyl-2,2′-cyanine (PIC), was successfully intercalated into Na2Ti3O7 by a guest-exchange method using a propylamine/Ti3O7 intercalation compound as the intermediate. Based on the XRD and chemical analytical results, it was presumed that PIC was densely packed in the interlayer space with the short axis of its quinoline-ring almost perpendicular to the host layer. Spectroscopic results revealed that the PIC formed J-aggregates even in the restricted space between the titanate layers.

    DOI

  • Pyrolytioc Conversion of Blended Precursors into Ti-Al-N Ceramic Composites

    Korean J. Ceram.   6(1)  2000年

  • Preparation of a Soluble Precursor by an Aminolysis Reaction of Zr(NEt2)4 and Its Pyrolytic Conversion into ZrN

    Chem. Lett.   2  2000年

    DOI

  • Formation of a Continuous Mesoporous Silica Film with Fully Aligned Mesochannels on a Glass Substrate

    Chem. Mater.   12、49〜54  2000年

    DOI

  • Pyrolytic conversion of the cage-type precursors into AlN

    Y. Sugahara, S. Koyama, K. Kuroda

    Key Engineering Materials   159-160   77 - 82  1999年12月  [査読有り]

     概要を見る

    Aluminum nitride (AlN) was prepared via pyrolysis of cage-type poly(alkyliminoalane) [(HAlNR), (R=Et, iPr)] under Ar or NH3-N2 atmospheres. Both (HAlNiPr), and (HAlNEt)m were converted into ceramic residues with relatively high ceramic yields. The ceramic residues obtained via pyrolysis of the precursors under an Ar atmosphere contained considerable amounts of carbon, while most of carbon was removed during the pyrolysis under an NH3-N2 atmosphere. The only obtained crystalline phase was AlN, whose lattice parameters showed that isostructural Al2OC was rarely dissolved in the lattices of the 2H wurtzite-type structures.

  • Intercalation of alkylamines and water into kaolinite with methanol kaolinite as an intermediate

    Y Komori, Y Sugahara, K Kuroda

    APPLIED CLAY SCIENCE   15 ( 1-2 ) 241 - 252  1999年09月  [査読有り]

     概要を見る

    Alkykamines and water were intercalated between the layers of kaolinite by utilizing a kaolinite/methanol intercalation compound as an intermediate. A kaolinite/methanol intercalation compound was synthesized by guest displacement reaction of a kaolinite/N-methylformamide intercalation compound with methanol. The basal spacing increased up to 5.75 nm when octadecylamine was used. It increased linearly with the length of alkyl chains by 0.255 nm per carbon atom, suggesting that the alkylamine molecules in the interlayer space of kaolinite take a bilayer arrangement with their alkyl chains almost perpendicular to the layers of kaolinite. Water molecules were also intercalated into kaolinite by displacement of methanol. The basal spacing of the product was 1.00 nm under wet conditions and 0.85 nm after drying. By using hydrated kaolinite as an intermediate, pyridine molecules were intercalated into kaolinite, thus, the hydrated kaolinite also shows the ability as an intermediate for displacement reactions. These results demonstrate that kaolinite has higher intercalation ability for a wider variety of guest species than previously accepted if appropriate intermediates are used. (C) 1999 Elsevier Science B.V. All rights reserved.

    DOI

  • Synthesis and structural study of the KNb4O6-type compound

    W Sugimoto, K Mimuro, Y Sugahara, K Kuroda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   107 ( 4 ) 318 - 321  1999年04月

     概要を見る

    Polycrystalline samples with nominal compositions K1+xNb4O6 (0 less than or equal to x less than or equal to 1.0) were prepared by the solid-state reaction of KNbO3, Nb2O5 and Nb. Powder X-ray diffraction analysis revealed that the KNb4O6-type compound was obtained as the major phase when x greater than or equal to 0.4. Transmission electron microscopy observations showed that when x=0.4, the KNb4O6-type compound contained intergrowth defects. In contrast, when x=1.0, practically no intergrowth defects were observed, although this sample contained KNbO3 as an impurity phase. The relation between the nominal composition and the formation of the intergrowth defects is discussed.

    DOI

  • Synthesis of Mesoporous Aluminophosphates Using Surfactants with Long Alkyl Chains

    <italic>Proc. 12th Int. Zeolite Conf.</italic><fontfamily>,<bold>II</bold></fontfamily>/Materials Research Society    1999年03月

  • Preparation of Fine Aggregate and Rod-like Ordered Mesoporous Silicas by the Use of Behenyltrimethylammonium Chloride with an Aqueous Sodium Metasilicate Solution

    <italic>Proc. 12th Int. Zeolite Conf.</italic><fontfamily>,<bold>I</bold></fontfamily>/Materials Research Society    1999年03月

  • Pyrolytic Convertion of the Cage-type Precursors into AIN

    Key Engineering Mater/Trans Tech Publications   159-160  1999年02月

  • Synthesis and Characterization of Lamellar and Hexagonal Mesostructured Aluminophosphates Using Alkyltrimethylammonium Cations as Structure Directing Agents

    Chem. Mater./Am. Chem. Soc.   11;2  1999年02月

    DOI

  • Synthesis of Mesoporous Materials Utilizing Molecular Assemblies

    Tatsuo Kimura, Kazuyuki Kuroda

    Kobunshi   48   256 - 259  1999年01月  [査読有り]

    DOI

  • Synthesis and structural study of the KNb<inf>4</inf>O<inf>6</inf>-type compound

    Wataru Sugimoto, Ken Mimuro, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Journal of the Ceramic Society of Japan   107   318 - 321  1999年01月  [査読有り]

     概要を見る

    Polycrystalline samples with nominal compositions K1+xNb4O6(0≤x≤1.0) were prepared by the solid-state reaction of KNbO3, Nb2O5and Mb. Powder X-ray diffraction analysis revealed that the KNb4O6-type compound was obtained as the major phase when x≥0.4. Transmission electron microscopy observations showed that when x=0.4, the KNb4O6-type compound contained intergrowth defects. In contrast, when x=1.0, practically no intergrowth defects were observed, although this sample contained KNbO3as an impurity phase. The relation between the nominal composition and the formation of the intergrowth defects is discussed.

  • Photochromism of azobenzene in the hydrophobic interlayer spaces of dialkyldimethylammonium-fluor-tetrasilicic mica films

    M. Ogawa, M. Hama, K. Kuroda

    Clay Minerals   34 ( 2 ) 213 - 220  1999年

     概要を見る

    ABSTRACT: Photochemical isomerization of azobenzenc intercalated in the Hydrophobie, interlayer spaces of swelling fluor-tetrasilicic micas exchanged with dialkyldimethylammonium ions, with the alkyl chain length from 10 to 18, was investigated. Thin films of the organoammonium-mica-azobenzene intercalation compounds were obtained by depositing a suspension of the organoammonium-micas (prepared using a toluene/methanol solution of azobcnzene) on quartz substrates. The intercalated azobenzene showed reversible photochromic reactions induced by UV and visible light irradiation. The fraction of the photochemically formed c/s-isomer in the photostationary states decreased with a decrease in temperature. The observed change in the photochemical reactions is thought to reflect changes in the states of the dialkyldimethylammonium ions in the interlayer space of the swelling fluor-tetrasilicic mica. © 1999 The Mineralogical Society.

    DOI

  • Direct Intercalation of Poly(vinylpyrrolidone) into Kaolinite by a Refined Guest Replacement Method

    Chem. Mater./Am. Chem. Soc.   11;1  1999年01月

    DOI

  • Synthesis of Na1-xLnxNbo3(Ln=La,Sm,Gd)and their structures and electrical properties in "Solid-State Chemistry of Inorganic Materials II"

    Mat.Res.Soc.Proc.   547  1999年

  • Preparation of a Kaolinite-εCaprolactam Intercalation compound

    Clay Sci.   11  1999年

    DOI

  • Synthesis and Structure of Reduced Niobates with Four Perovskite-like Layers and Their Semiconducting Properties

    J. Solid State Chem.   148  1999年

    DOI

  • New Conversion Reaction of an Aurivillius Phase into the Protonated Form of the Layered Perovskite by the Selective Leaching of the Bismuth Oxide Sheet

    J. Am. Chem. Soc.   121  1999年

    DOI

  • Alignment of Mesostructured Silica on a Langmuir-Blodgett Film

    Adv. Mater.   11(17)  1999年

    DOI

  • Thermal Transformation of a Kaolinite-Poly(acrylamide) Intercalation Compound

    J. Mater. Chem.   9(12)  1999年

    DOI

  • An Acentric Arrangement of p-Nitroaniline Molecules between the Layers of Kaolinite

    Chem. Commun.   22  1999年

    DOI

  • Preferred Alignment of Mesochannels in a Mesoporous Silica Film Grown on a Silicon (110) Surface

    J. Am. Chem. Soc.   121  1999年

    DOI

  • "Synthesis of Na1-xLnxNbO3 (Ln=La, Nd, Sm, Gd) and their structures and electrical properties", in "Solid-State Chemistry of Inorganic Materials II"

    Mat. Res. Soc. Symp. Proc.   547  1999年

  • Alignment of Mesoporous Silica on a Glass Substrate by a Rubbing Method

    Chem. Mater.   11(6)  1999年

    DOI

  • Direct Observation of Mesoporous Silica by High Resolution Scanning Electron Microscopy

    Adv. Mater.   11  1999年

    DOI

  • Pyrolytic Convertion of the Cage-type Precursors into AlN

    Key Engineering Mater.   159〜160  1999年

  • Synthesis of Reduced Layered Titanoniobates KTi1-xNb1+xO5

    Mater. Lett.   39  1999年

    DOI

  • Preparation and characterization of silylated-magadiites

    Appl. Clay Sci.   15  1999年

    DOI

  • Intercalation of Alkylamines and Water into Kaolinite by Using a Kaolinite-Methanol Intercalation Compound

    Appl. Clay Sci.   15  1999年

  • Time-Resolved In-Situ X-Ray Powder Diffraction Study of the Formation of Mesoporous Silicates

    Chem. Mater.   11  1999年

    DOI

  • Adsorption of Taxol into Ordered Mesoporous Silicas with Various Pore Diameters

    Chem. Mater.   11  1999年

    DOI

  • Organic Modification of FSM-type Mesoporous Silicas by Silylation

    Langmuir   15(8)  1999年

    DOI

  • Synthesis and Characterization of Lamellar and Hexagonal Mesostructured Aluminophosphates Using Alkyltrimethylammonium Cations as Structure Directing Agents

    Chem. Mater.   11  1999年

    DOI

  • Photochromism of Azobenzene in the Hydrophobic Interlayer Spaces of Dialkyldimethylammonium-Fluor-tetrasilisic Mica Films

    Clay Minerals   34  1999年

    DOI

  • Preparation of Fine Aggregate and Rod-like Ordered Mesoporous Silicas by the Use of Behenyltrimethylammonium Chloride with an Aqueous Sodium Metasilicate Solution

    Proc.12th Int.Zeolite Conc.Baltimore.   Vol. I  1999年

  • Synthesis of Mesoporous Aluminophosphates Using Surfactants with Long Alkyl Chains

    Proc.12th Int.Zeolite Conf.Baitimore.   Vol. II  1999年

  • Preparation of Smectite-Dodecyldimethylamine-N-Oxide Intercalation Compounds

    Langmuir/Am. Chem. Soc.   14;24  1998年12月

    DOI

  • Perfluoroalkylsilylation of the Interlayer Silanol Groups of a Layered Silicate, Magadiite

    Chem. Mater./Am. Chem. Soc.   10;12  1998年12月

    DOI

  • Preparation of smectite/dodecyldimethylamille N-oxide intercalation compounds

    M Ogawa, N Kanaoka, K Kuroda

    LANGMUIR   14 ( 24 ) 6969 - 6973  1998年11月  [査読有り]

     概要を見る

    The adsorption of dodecyldimethylamineN-oxide into the interlayer space of Na-saponite was investigated. The Na-saponite/dodecyldimethylamine N-oxide intercalation compounds were prepared as supported and unsupported films. Intercalation compounds with two different arrangements of the intercalated dodecyldimethylamine N-oxide were obtained, depending on the adsorbed amounts, When the adsorbed amount was greater than 400 mmol/100 g of clay, the intercalated dodecyldimethylamine N-oxide took a paraffin type bilayer. On the other hand, the intercalated dodecyldimethylamine N-oxide molecules are thought to arrange as a bimolecular coverage with their alkyl chains parallel to the silicate sheet when the added amount of dodecyldimethylamine N-oxide was 100 mmol/100 g of clay. The coadsorption of tris(2,2'-bipyridine)ruthenium(II) with dodecyldimethylamine N-oxide was achieved. The luminescence characteristics of tris(2,2'-bipyridine)ruthenium(II) revealed that there are certain interactions between the adsorbed tris(2,2'-bipyridine)ruthenium(II) and dodecyldimethylamine N-oxide in the interlayer space of saponite. Since the products have been obtained as highly transparent supported and self-standing films, the intercalation of dodecyldimethylamine N-oxide is a way to control the adsorbed states of cationic dyes on the surface of smectites.

    DOI

  • Morphological Control of Ordered Mesoporous Silica: Formation of Fine and Rod-like Mesoporous Powders from Completely Dissolved Aqueous Solutions of Sodium Metasilicate and Cationic Surfactants

    Chem. Commun./Royal Soc. Chem.   1998;22  1998年11月

  • Pyrolytic Conversion of Precursors prepared in Ti(NMe<2<)<4<-Diamine Systems

    Appl. Organomet./John Wiley &Sons   12;10-11  1998年10月

    DOI

  • Control of Interlayer Microstructures of a Layered Silicate by Surface Modification with Organochlorosilanes

    J. Am. Chem. Soc./Am. Chem. Soc.   120;29  1998年07月

    DOI

  • Synthesis of Mesoporous Aluminophosphates and Their Adsorption Properties

    Microporous Mesoporous Mater./Elsevier   22;1-3  1998年06月

    DOI

  • Synthesis and structures of carrier doped titanates with the Ruddlesden-Popper structure (Sr0.95La0.05)(n+1)TinO3n+1 (n = 1, 2)

    W Sugimoto, M Shirata, M Takemoto, S Hayami, Y Sugahara, K Kuroda

    SOLID STATE IONICS   108 ( 1-4 ) 315 - 319  1998年05月  [査読有り]

     概要を見る

    Carrier doping in Srn+1TinO3n+1 (n = 1, 2) was conducted by the substitution of La for Sr and the simultaneous introduction of oxygen vacancies. Single-phase products of (Sr0.95La0.05)(n+1)TinO3n+1-delta(n = 1, delta = 0.05; n = 2, delta = 0.125) were synthesized by the solid-state reaction of Sr2TiO4 (or Sr3Ti2O7), La2O3 and Ti. When TiO2 was used as one of the starting compounds to maintain oxygen stoichiometry, compounds with higher n were observed besides the object phases. Structural refinement by Rietveld analysis revealed that the a-axis expands while the c-axis contracts with La doping. The contraction of the c-axis is attributed to a shortened (Sr,La)-O distance, since the TiO6 octahedra elongated in both a and c directions with doping. The change in the structure is discussed on the basis of the size of the substituting ion. The resistivity of the single-phase products was semiconducting with a very weak temperature dependence down to 80 K. (C) 1998 Elsevier Science B.V. All rights reserved.

  • Thermotropic Behavior of the Silica-Alkyltrimethylammonium Chloride Mesostructured Materials

    Chem. Mater./Am. Chem. Soc.   10;5  1998年05月

    DOI

  • Synthesis of Oriented Inorganic-Organic Nanocomposite Films from Alkyltrialkoxysilane-Tetraalkoxysilane Mixtures

    J. Am. Chem. Soc./Am. Chem. Soc.   120;18  1998年05月

    DOI

  • Synthesis and Structures of Carrier Doped Titanates with the Ruddleesden-Popper Structre (Sr<0.95<La<0.05<)<n+1<Ti<n<O<3n+1-d<(n=1, 2)

    Solid State Ionics/Elsevier   108  1998年05月

    DOI

  • A Kaolinite-NMF-Methanol Intercalation Compound as a Versatile Intermediate for Further Intercalation Reaction ofKaolinite

    J. Mater. Res./Mater. Res. Soc.   13;4  1998年04月

    DOI

  • Esterification of the Silanol Groups in the Mesoporous Silica Derived from Kanemite

    J. Porous Mater./Kluwer   5 ;2  1998年04月

  • Synthesis of Mesoporous Aluminophosphates by using Surfactants with Long Alkyl Chain Length and Triisopropylbenzene as a Solubilizing Agent

    Chem. Commun./Royal Soc. Chem.   1998;5  1998年04月

  • Synthesis and Structures of Carrier Dpoed Titanates with the Ruddleesden-Popper Structre (Sr0.95La0.05)n+1TinO3n+1-d (n=1, 2)

    Solid State Ionics   108, pp.315-319  1998年03月

    DOI

  • Synthesis of Mesoporous Aluminophosphates by Using Surfactants with Long Alkyl Chain Length and Triisopropylbenzene as a Solubilizing Agent

    Chem. Commun.   pp.559-560  1998年03月

    DOI

  • Esterification of the Silanol Groups in the Mesoporous Silica Derived form Kanemite

    J. Porous Mater.   5, pp.127-132  1998年03月

  • Esterification of the Silanol Groups in the Mesoporous Silica Derived from Kanemite

    Tatsuo Kimura, Kazuo Kuroda, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Journal of Porous Materials   5 ( 2 ) 127 - 132  1998年  [査読有り]

     概要を見る

    Silanol groups in the mesoporous silica derived from a layered silicate, kanemite (NaHSi2O5 · 3H2O), were esterified with alcohols (CnH2n+1OH
    n = 2, 4, and 8). Most of the silanol groups in the mesopores were modified with ethanol though some silanol groups remained after the reactions with 1-dutanol and 1-octanol. With the increase in the alkyl chain lengths of the alcohols, the pore sizes of the esterified products decreased and the hydrophobicity increased.

    DOI

  • Preparation of a Hybrid Preceramic Precursor for Al-Si-N-C Nanocomposites via a Molecular Building Block Approach

    Chem. Lett.   pp.191-192  1998年01月

    DOI

  • The Relationship Between Structural Variation and Electrical Properties in the Spinel MgV2-xTixO4

    J. Phys. Chem. Solids   59;1, pp.83-89  1998年01月

    DOI

  • Preparation of Soluble AlN Precursors in a LiAlH4-CH3NH2・HCl-(CH3)2NH・HCl System

    Chem. Lett.   pp.1227-1228  1997年12月

  • Preparation of Inorganic-Organic Nanocomposites through Intercalation of Organoammonium Ions into Layered Silicates

    Bull. Chem. Soc. Jpn.   70, pp.2593-2618  1997年11月

    DOI

  • Inorganic-Organic Layered Materials Derived via the Hydrolysis and Polycondensation of Trialkoxy(alkyl)silanes

    Bull. Chem. Soc. Jpn.   70,pp.2847-2853  1997年11月

    DOI

  • Preparation of Transparent Silica-Surfactant Nanocomposite Films with Controlled Microstructures

    Bull. Chem. Soc. Jpn.   70,pp.2833-2837  1997年11月

    DOI

  • Preparation of Aluminum Nitride from Precursors with Cage-type Structures (HAlNR)n (R=Et,iPr)

    Proc. 14th Int. Jpn-Korea Seminar Ceram.   pp.405-410  1997年10月

  • Formation of Layered Inorganic-Organic Nanocomposites by the Hydrolysis and Polycondensation of Alkyltriethoxysilane

    Proc. 14th Int. Jpn-Korea Seminar Ceram.   pp.284-288  1997年10月

  • Synthesis of a Hexagonal Mesostructured Aluminophosphate

    Chem. Lett.   pp.983-984  1997年10月

    DOI

  • 層状ケイ酸塩—古くて新しい層状物質—

    化学と工業   50;8, pp.1083-1085  1997年08月

  • 可溶性セラミック前駆体からの窒化アルミニウムの合成

    無機マテリアル   4[5],pp.280-286  1997年07月

    DOI

  • Intercalation of a Crown-Ether into Layered Silicates

    Clay Sci.   10;[2], pp.185-194  1997年06月

    DOI

  • Pyrolytic Preparation of Gallium Nitride from [Ga(Net2)3]2 and Its Ammonolysis Compound

    Mater.Res. Soc. Proc.   468,pp.93-98  1997年04月

  • The rare-earth dependence on the solid solution formation and electrical properties of KCa2-xRXNb3O10 (R=Nd, Sm, Gd and Ce)

    D Hamada, W Sugimoto, Y Sugahara, K Kuroda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   105 ( 4 ) 284 - 287  1997年04月

     概要を見る

    The solid solution KCa2-xRxNb3O10 (R = Nd, Sm, Gd and Ce) was prepared by solid-state reaction using KCa2Nb3O10, KNbO3, Nb2O5, Nb and rare-earth oxides, The solubility limit of the solid solutions was extended with an increase in the ionic radii of the rare earths. All the solid solutions exhibited similar semiconductive behavior with a linear log p-T relationship over a wide temperature range. These results suggest that the conduction mechanism is independent of the type of rare earths and also the unit-cell parameters, which. agrees well with the tunneling conduction model with a vibrating barrier.

    DOI

  • Preparation of stoichiometric and nonstoichiometric magnesium titanate spinels

    W Sugimoto, N Kaneko, Y Sugahara, K Kuroda

    JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   105 ( 2 ) 101 - 105  1997年02月

     概要を見る

    Polycrystalline samples of stoichiometric spinels, Mg1+xTi2-xO4 (0 less than or equal to x less than or equal to 1.0), and spinels with cation diversity, Mg((1+x)y)Ti2-xO4 and Mg(1+x)Ti((2-x)y)O-4 (x=0.4215, y=0.95-1.05), and oxygen deficiency Mg1+xTi2-xO4-delta (x=0.4215, delta=0.05-0.30) were prepared by solid-state reaction of MgO, TiO2 and Ti to examine the effects of the composition and holding time on the structure of the spinel phase, the impurity phase formation behavior and the electrical properties, In addition to Mg2TiO4 (x=1) prepared at 1300 degrees C under an ambient atmosphere, samples were prepared at 1250 degrees C under an argon atmosphere, Compositional analyses revealed that volatilization of compounds and oxidation during firing were negligible, The variation in the unit cell parameter a of the spinel phase indicated solid-solution formation for all stoichiometric samples in spite of the presence of impurities, The impurity-phase formation behavior was strongly dependent upon synthetic conditions, x-value, and induced nonstoichiometry, Other than the insulating Mg2TiO4, resistivity measurements indicated that all samples were semiconducting below room temperature. No distinct variation in resistivity behavior was observed for samples with different holding time or with induced nonstoichiometry.

    DOI

  • Polymerization Reactions in an Al(Obus)3-(COOH)2 System

    J. Sol-Gel Sci. Tech.   8;[1-3],pp.95-99  1997年02月

    DOI

  • Preparation of stoichiometric and nonstoichiometric magnesium titanate spinels

    Wataru Sugimoto, Naohiro Kaneko, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Journal of the Ceramic Society of Japan   105   101 - 105  1997年01月  [査読有り]

     概要を見る

    Polycrystalline samples of stoichiometric spinels, Mg1+xTi2-xO4(0≤x≤1.0), and spinels with cation diversity, Mg(1+x)yTi2-xO4and Mg1+xTi(2-x)y,O4(x=0.4215, y=0.95-1.05), and oxygen deficiency Mg1+xTi2-xO4-δ(x=0.4215, δ=0.05-0.30) were prepared by solid-state reaction of MgO, TiO2and Ti to examine the effects of the composition and holding time on the structure of the spinel phase, the impurity phase formation behavior and the electrical properties. In addition to Mg2TiO4(x=1) prepared at 1300°C under an ambient atmosphere, samples were prepared at 1250°C under an argon atmosphere. Compositional analyses revealed that volatilization of compounds and oxidation during firing were negligible. The variation in the unit cell parameter a of the spinel phase indicated solid-solution formation for all stoichiometric samples in spite of the presence of impurities. The impurity-phase formation behavior was strongly dependent upon synthetic conditions, x-value, and induced nonstoichiometry. Other than the insulating Mg2TiO4, resistivity measurements indicated that all samples were semiconducting below room temperature. No distinct variation in resistivity behavior was observed for samples with different holding time or with induced nonstoichiometry.

    DOI

  • Polymerization reactions in an Al(OBu(s))(3)-(COOH)(2) system

    Y Sugahara, Takaya, I, J Chiba, K Kuroda

    JOURNAL OF SOL-GEL SCIENCE AND TECHNOLOGY   8 ( 1-3 ) 95 - 99  1997年  [査読有り]

     概要を見る

    Reactions in an Al(OBu(s))(3)-(COOH)(2) (OA)-tetrahydrofuran (THF)/(CD3)(2)SO (DMSO-d(6)) system (Al(OBu(s))(3):THF:DMSO-d(6):OA = 1:5:5:x, x = 0.01-3) were studied, without the addition of water and the process was monitored by NMR. When x less than or equal to 10.3, homogeneous solutions were obtained, whereas white precipitates formed with x greater than or equal to 0.7. The formation of sec-butyl alcohol was evident with x greater than or equal to 0.6, indicating that oxalate groups coordinate to aluminum to release sec-butyl alcohol. C-13 NMR spectra of the solutions after 1 day suggest the presence of polymeric species if 0.03 less than or equal to x less than or equal to 0.6. The addition of a small amount of water resulted in the formation of a white precipitate (Al(OBu(s))(3):THF:DMSO-d(6):OA:H2O = 1:5:5:0.3:y, y = 0.03-0.3), indicating that water, possibly formed by esterification in the Al(OBu(s))(3)-OA-THF/DMSO-d(6) system, does not take a major role in the present system.

    DOI

  • Preparation of soluble AIN precursors in a LiAlH<inf>4</inf>-CH<inf>3</inf>NH<inf>2</inf>·HCl-(CH<inf>3</inf>)<inf>2</inf>NH-HCl system

    Seiichi Koyama, Yasuo Saito, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Chemistry Letters   ( 12 ) 1227 - 1228  1997年  [査読有り]

     概要を見る

    Novel AlN precursors have been prepared by reactions in a LiAlH4-CH3NH2·HCl-(CH3)2NH·HCl system with several nominal CH3NH2·HCl:(CH3)2NH·HCl (M:D) ratios (M:D=4:1, 6:1 and 8:1). Considerable amounts of precursors were soluble in both tetrahydrofuran and benzene. Soluble precursors consist of polymeric/oligomeric species possessing both [H2AlNMe2] and [HAlNMe] units, and ring-type (H2AlNMe2)3was also present only if M:D=4:1. The precursors were converted into single-phase AIN with relatively high ceramic yields (up to 58 %) by pyrolysis at 1600°C under Ar.

    DOI

  • The rare-earth dependence on the solid solution formation and electrical properties of KCa<inf>2-x</inf>R<inf>x</inf>Nb<inf>3</inf>O<inf>10</inf>(R=Nd, Sm, Gd and Ce)

    Daisuke Hamada, Wataru Sugimoto, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Journal of the Ceramic Society of Japan   105   284 - 287  1997年01月  [査読有り]

     概要を見る

    The solid solution KCa2-xRxNb3O10(R=Nd, Sm, Gd and Ce) was prepared by solid-state reaction using KCa2Nb3O10, KNbO3, Nb2O5, Nb and rare-earth oxides. The solubility limit of the solid solutions was extended with an increase in the ionic radii of the rare earths. All the solid solutions exhibited similar semiconductive behavior with a linear log p-T relationship over a wide temperature range. These results suggest that the conduction mechanism is independent of the type of rare earths and also the unit-cell parameters, which agrees well with the tunneling conduction model with a vibrating barrier.

  • 29Si NMR Study on Co-hydrolysis Processes in the Si(OEt)4-RSi(OEt)3-EtOH-Water-HCl Systems (R=Me, Ph); Effect of R Groups

    J. Mater.Chem.   7[1],pp.53-60  1997年01月

    DOI

  • Adsorption and aggregation of a cationic cyanine dye on smectites

    M Ogawa, R Kawai, K Kuroda

    JOURNAL OF PHYSICAL CHEMISTRY   100 ( 40 ) 16218 - 16221  1996年10月  [査読有り]

     概要を見る

    The adsorption and aggregate formation of a cationic cyanine dye, 1,1'-diethyl-2,2'-cyanine, on montmorillonite and saponite have been investigated for aqueous suspensions and cast films. In aqueous suspensions, the cyanine dye cations formed J-aggregates on montmorillonite, while they distribute molecularly on saponite. On the other hand, the dye formed J-aggregates on both montmorillonite and saponite in the cast films. Thus, the spectroscopic features of the cyanine dye reflected the difference between montmorillonite and saponite in organizing guest species, This difference suggests that the cyanine dye can be organized in a controlled manner by the selection of host materials. The J-aggregates formed on the layered silicates may be useful for the study of optical properties of the aggregates because of their stable and confined microstructure.

    DOI

  • Adsorption isotherm of water vapor and its large hysteresis on highly ordered mesoporous silica

    S Inagaki, Y Fukushima, K Kuroda, K Kuroda

    JOURNAL OF COLLOID AND INTERFACE SCIENCE   180 ( 2 ) 623 - 624  1996年06月  [査読有り]

     概要を見る

    The first and second adsorption-desorption isotherms of water vapor on a new mesoporous material derived from kanemite have been measured. The isotherms show unusual type V isotherms and large hysteresis. The type V isotherms, which have never been observed for the other adsorbates, suggest that the mesoporous material has a hydrophobic surface, although the hydrophobicity decreased after treatment with water vapor because of rehydration of the surface. The significantly large hysteresis could be explained by the difference in contact angle between adsorption and desorption. (C) 1996 Academic Press, Inc.

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  • Silica-based mesoporous molecular sieves derived from a layered polysilicate kanemite - A review

    Kazuyuki Kuroda

    Journal of Porous Materials   3 ( 2 ) 107 - 114  1996年  [査読有り]

     概要を見る

    Synthesis of highly ordered mesoporous materials derived from a layered polysilicate kanemite has been reviewed. Silica-surfactant mesostructured materials are obtained by the reaction of kanemite with alkyltrimethylammonium ions. Calcination of silica-surfactant mesophase materials yields ordered mesoporous molecular sieves. Substantial replacement of alkyltrimethylammonium ions for interlayer Na ions and careful adjustment of pH in the reaction media are necessary for the preparation of ordered mesoporous silica. Formation processes of the silicate-surfactant mesophase materials have been monitored by in-situ powder X-ray diffraction technique which has indicated the presence of a lamellar phase before the appearance of a hexagonal phase. Comparison of these materials with MCM-41 is briefly mentioned. The properties and potential applications of these materials are also briefly outlined. © 1996 Kluwer Academic Publishers.

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  • Syntheses of Highly Ordered Mesoporous Materials, FSM-16, Derived from Kanemite

    Shinji Inagaki, Akihiko Koiwai, Noritomo Suzuki, Yoshiaki Fukushima, Kazuyuki Kuroda

    Bulletin of the Chemical Society of Japan   69 ( 5 ) 1449 - 1457  1996年  [査読有り]

     概要を見る

    The synthetic conditions of highly ordered and thermally stable mesoporous molecular sieves from a layered silicate kanemite are established. We divided the formation process of the mesoporous materials from kanemite into two elemental processes: i) exchange of Na+ in the interlayer of kanemite for alkyltrimethylammonium cations and ii) condensation of silicates and formation of a three dimensional silicate framework. Higher pH (over 11.5) at the cation-exchange process and the subsequent pH adjustment at 8.5 at the condensation process were best suited for the formation of mesoporous products with high regularity and thermal stability. Removal of partially dissolved kanemite during the cation-exchange process avoided the formation of amorphous materials as a by-product. Structures of some intermediate silicate/surfactant complexes supported the proposed folded sheets mechanism for the formation of the mesoporous molecular sieves. Syntheses by using alkyltrimethylammonium with different alkyl-chain lengths are also reported.

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  • Preparation of AlN from poly(ethyliminoalane) via pyrolysis

    Seiichi Koyama, Hikaru Takeda, Yasuo Saito, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Journal of Materials Chemistry   6 ( 6 ) 1055 - 1058  1996年  [査読有り]

     概要を見る

    Aluminium nitride (AlN) powder has been prepared by pyrolysing poly(ethyliminoalane) under Ar (at 1600 °C for 2 h) and NH3-N2 (at 600 °C for 2 h under NH3 and at 1350 °C for 8 h under N2) atmospheres, and the products have been characterized by X-ray powder diffraction, solid-state 27Al NMR spectroscopy, elemental analysis, scanning electron microscopy, and nitrogen adsorption measurement. The only crystalline product was AlN, in which carbon and oxygen were hardly present by solid-solution formation. A considerable amount (17.1 mass%) of carbon remained in the product pyrolysed under Ar, whereas most of carbon was removed during the pyrolysis under NH3-N2 (0.1 mass%). The AlN particles obtained by pyrolysis under NH3-N2 were finer than those obtained by pyrolysis under Ar. The ceramic yields were 50% (Ar) and 57% (NH3-N2)
    the latter value is close to the theoretical yield (58%).

    DOI

  • Characterization of aluminum nitride from a precursor poly (isopropyliminoalane)

    Yasuo Saito, Seiichi Koyama, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Journal of the Ceramic Society of Japan   104   143 - 145  1996年01月  [査読有り]

     概要を見る

    Aluminum nitride (AlN) was prepared by pyrolysis of poly(isopropyliminoalane) under Ar and NH3/N2atmospheres. X-ray powder diffraction analysis revealed that the only crystalline phase was AlN, whose lattice constants showed that possible amounts of carbon and oxygen in the lattice should be very small. Chemical analyses showed the presence of carbon only in the product pyrolyzed in Ar; almost all carbon was removed by pyrolysis in NH3/N2. The ceramic yield for two-step pyrolysis in Ar (1000°C for 2h, 1600°C for 2h) was 32%, while that for pyrolysis in NH3/N2(600°C for 2h in NH3, 1350°C for 8h in N2) was 47%.

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  • Preparation and electrical properties of KCa2-xLaxNb3O10

    D Hamada, M Machida, Y Sugahara, K Kuroda

    JOURNAL OF MATERIALS CHEMISTRY   6 ( 1 ) 69 - 72  1996年01月  [査読有り]

     概要を見る

    Electron-doped layered perovskite KCa2-xLaxNb3O10 was prepared from KNbO3, Nb2O5, Nb, La2O3 and KCa2Nb3O10 at 1200 degrees C for 10 h under Ar. Essentially single-phase KCa2-xLaxNb3O10 with plate-like morphology was obtained with 0 less than or equal to x less than or equal to 0.3, and lattice parameters increased with increasing x. All the La-doped products showed semiconducting behaviour. Linear (log rho)-T relationships were clearly observed, but the resistivity behaviour deviates from the linear relationship at lower temperatures. A possible conduction mechanism is discussed.

    DOI

  • FORMATION OF SILICA-SURFACTANT MESOPHASES STUDIED BY REAL-TIME IN-SITU X-RAY-POWDER DIFFRACTION

    S OBRIEN, RJ FRANCIS, SJ PRICE, D OHARE, SM CLARK, N OKAZAKI, K KURODA

    JOURNAL OF THE CHEMICAL SOCIETY-CHEMICAL COMMUNICATIONS   ( 23 ) 2423 - 2424  1995年12月  [査読有り]

     概要を見る

    Real-time in situ energy dispersive synchrotron X-ray powder diffraction data provides evidence for the formation of an intermediate lamellar silica-surfactant intercalate during the synthesis of the hexagonal-mesophase derived from the layered polysilicate kanemite, whereas no intermediate phases are observed during the formation of the silica-surfactant mesophase that leads to the mesoporous material MCM-41.

    DOI

  • Photoluminescence of tris(2,2′-bipyridine)ruthenium(II) ions intercalated in layered niobates and titanates: Effect of interlayer structure on host-guest and guest-guest interactions

    Teruyuki Nakato, Kazuhiko Kusunoki, Katsuaki Yoshizawa, Kazuyuki Kuroda, Masao Kaneko

    Journal of Physical Chemistry   99 ( 51 ) 17896 - 17905  1995年12月  [査読有り]

     概要を見る

    Intercalation compounds of layered niobates and titanates with tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+, bpy = 2,2′-bipyridine) ions were synthesized and their photoluminescent behavior was investigated. K4Nb6O17, HTiNbO5, and H2Ti4O9were used as the host. Ru(bpy)32+ions were intercalated by displacement of pre-intercalated alkylammonium ions or direct reaction and were densely present in the interlayer spaces. Luminescence lifetimes of the intercalated Ru(bpy)32+ions showed concentration quenching of the emission. The guest displacement technique yielded some intercalation compounds where alkylammonium ions were co-intercalated with Ru(bpy)32+ions, and the co-intercalated photoinactive ions suppressed the concentration quenching to some extent. Ru(bpy)32+ions were distorted and in close contact with the host lattices in the interlayer spaces of the samples whose interlayer spacing was small. Luminescence decay of these intercalation compounds was fast, suggesting that the emission of the intercalated Ru(bpy)32+ions was quenched by the host lattices. © 1995 American Chemical Society.

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  • Formation of a Methoxy-Modified Interlayer Surface via the Reaction between Methanol and Layered Perovskite HLaNb<inf>2</inf>O<inf>7</inf>·xH<inf>2</inf>O

    Shun Takahashi, Teruyuki Nakato, Shigenobu Hayashi, Yosbiyuki Sugahara, Kazuyuki Kuroda

    Inorganic Chemistry   34 ( 20 ) 5065 - 5069  1995年09月  [査読有り]

     概要を見る

    The reactions between methanol (CH3OH, CH3OD, CD3OD,13CH3OH) and layered HLaNb2O7·xH2O were investigated. X-ray powder diffraction (XRD) analysis showed that a peak corresponding to the basal spacing of HLaNb2O7·xH2O (1.05 nm) disappeared and a new peak appeared at 1.18 nm. Carbon-13 NMR spectra revealed the presence of two environments of the methyl group; the broad 67 ppm signal is ascribed to the rigid species located in the interlayer space, and the 50 ppm signal is ascribed to mobile methanol on the external surface. The amount of the latter species was negligibly small. Deuterium NMR spectra revealed the presence of a Pake doublet with an effective quadrupole coupling constant (QCC) of 47 kHz and an asymmetry factor (η) of zero, indicating that the CD3O group was rigidly bound to the interlayer surface. In addition, when both CD3OD and CH3OD were used, no signal corresponding to the OD group was observed. Hence, although XRD results can be interpreted as intercalation of methanol, the2H NMR results indicate that methanol was dissociatively adsorbed to the interlayer surface. The observed very high thermal stability of the methyl group is consistent with methoxy formation. The structure of the product is discussed on the basis of the results with larger n-alcohols. © 1995, American Chemical Society. All rights reserved.

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  • Solid-State Ion Exchange Reactions between Homoionic-Montmorillonites and Organoammonium Salts

    Makoto Ogawa, Akira Hagiwara, Tokuhiko Handa, Chuzo Kato, Kazuyuki Kuroda

    JOURNAL OF POROUS MATERIALS   1 ( 1 ) 85 - 89  1995年03月  [査読有り]

     概要を見る

    Organoammonium-montmorillonite intercalation compounds were prepared by solid-state ion exchange reactions which we have developed recently in order to understand the nature of the solid-state intercalation reactions. The reactions were carried out by grinding the mixtures of homoionic-montmorillonites and organoammonium (dodecyltrimethylammonium, tetramethylammonium, and tetrabutylammonium) halides (chloride, bromide, and iodide) at room temperature. Both of the counter anions of the organoammonium salts and the interlayer exchangeable cations of montmorillonite are concerned with the solid-state ion exchange reactions, indicating that the solid-solid reactions are thermodynamically governed. The solid-state ion exchange reactions lead to novel and different reactivities and intercalation compounds from those of conventional solution methods.

    DOI

  • Photofunctions of Intercalation Compounds

    Makoto Ogawa, Kazuyuki Kuroda

    Chemical Reviews   95 ( 2 ) 399 - 438  1995年  [査読有り]

    DOI

  • Intercalation of p-Nitroaniline into Tetramethylammonium Saponite Film under Electric Field and Its Optical Second Harmonic Generation

    Makoto Ogawa, Masaru Takahashi, Kazuyuki Kuroda

    Chemistry of Materials   6   715 - 717  1994年06月  [査読有り]

    DOI

  • ORIENTED MICROPOROUS FILM OF TETRAMETHYLAMMONIUM PILLARED SAPONITE

    M OGAWA, M TAKAHASHI, C KATO, K KURODA

    JOURNAL OF MATERIALS CHEMISTRY   4 ( 4 ) 519 - 523  1994年04月  [査読有り]

     概要を見る

    Tetramethylammonium saponite film has been prepared and its structure has been characterized. By casting the aqueous suspension of the tetramethylammonium-saponite, a transparent film was obtained. The film is composed of oriented silicate particles with ab planes parallel to the substrate. The interlayer tetramethylammonium ions provide micropores in the interlayer space and the micropores are interconnected in the direction parallel to the silicate sheet. The film is regarded as a unique immobilizing medium for photoactive species because of the transparency and the anisotropic microporous structure.

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  • Synthesis and characterization of highly ordered mesoporous material; FSM-16, from a layered polysilicate

    S. Inagaki, Y. Fukushima, K. Kuroda

    Studies in Surface Science and Catalysis   84   125 - 132  1994年01月  [査読有り]

     概要を見る

    Development of preparation conditions of highly ordered mesoporous SiO2materials(FSM-16) derived from a layered polysilicate has been summarized and a “folded sheets: mechanism for their formation has been presented. When Na ions in the interlayer region of kanemite were exchanged for alkyltrimethylammonium ions, organoammonium/silicate complexes were obtained and mesoporous silica materials were prepared by calcination of those complexes. When the exchange reaction was carried out at a relatively low pH(∼8.5), the exchange ratio was low and highly ordered pore structures of the mesoporous silica could not be confirmed although the formation of uniform pore size was realized. Increasing the pH(∼11.5) improved the exchange ratio and consequently realized highly porous materials with a regular hexagonal array of uniform channels. The condition of high pH(&gt;11.5) increased a fraction of dissolved silica species. Removal of the dissolved species from the system was necessary to prepare pure FSM-16. The improvement of the reguarlity and purity of FSM-16 by increasing the pH and filtration supported the “folded sheets” mechanism for its formation. The Q4/Q3ratios of SiO4tetrahedra in the silicate/organic complexes prepared by the optimum procedure were in good agreement with those calculated by the folded sheets model and the observed N2absorption behavior suggested an uniform pore-size of FSM-16. © 1994, Elsevier Science B.V.

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  • Layered Silicate-Organic Interncalation Compounds as Photofunctional Materials

    Makoto Ogawa, Kazuyuki Kuroda, Chuzo Kato

    Studies in Surface Science and Catalysis   83   171 - 178  1994年01月  [査読有り]

     概要を見る

    The alkylammonium-exchanged swellable layered clay minerals have been prepared and used as immobilizing media for photoactive organic compounds. Anthracene, pyrene and p-aminoazobenzene were incorporated into the interlayer spaces of the long-chain alkylammonium exchanged-smectites. It was revealed from the photoprocesses of the intercalated species that the adsorptive properties of the host materials varied depending on the arrangements of the interlayer alkylammoniumions. Besides the hydrophobic modification by long chain alkylammonium ions. 2-dimensional microporous structure was obtained by pillaring with tetramethylammonium ion. © 1994, Kodansha Ltd.

    DOI

  • 29Si-NMR study of hydrolysis and initial polycondensation processes of organoalkoxysilanes. II. Methyltriethoxysilane

    Yoshiyuki Sugahara, Seigo Okada, Shuji Sato, Kazuyuki Kuroda, Chuzo Kato

    Journal of Non-Crystalline Solids   167   21 - 28  1994年01月  [査読有り]

     概要を見る

    The hydrolysis and initial polycondensation processes of methyltriethoxysilane (MTES) have been investigated by high-resolution29Si-nuclear magnetic resonance spectroscopy (29Si-NMR). MTES was hydrolyzed in the system with MTES:ethyl alcohol:water:HCL = 1:4:x:y; x = 1, 2, 3, 6; y = 1 × 10-4, 1 × 10-2. Signals due to end and middle groups of polysiloxanes formed sub-regions on the basis of the number of hydroxyl groups attached to silicon, and the sub-region for silicon possessing more hydroxyl groups was observed at a lower field. Based on signal intensities, the signals due to the dimers (Me(HO)2SiOSi(OH)2Me and Me(HO)2SiOSi(OH)OEt)Me) and the trimer (Me(HO)2SiOSiMe(HO)OSi(OH)2Me) (MeCH3, EtC2H5) were identified. © 1994.

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  • Novel polysiloxane formation process from dimethyldiethoxysilane in the presence of oxalic acid - Code: BP10

    J. Chiba, Y. Sugahara, K. Kuroda

    Journal of Sol-Gel Science and Technology   2   153 - 156  1994年01月  [査読有り]

     概要を見る

    Polysiloxane formation in dimethyldiethoxysilane (DMDES)-ethyl alcohol (EtOH(D))-oxalic acid (OA) (DMDES:EtOH(D):OA=1:2:0.5) and DMDES-dimethylsulfoxide (DMSO)-OA (DMDES:DMSO:OA=1:2:0.5) systems was investigated by gas chromatography-mass spectrometry and 29Si-nuclear magnetic resonance. While the DMDES-EtOH(D)-OA system was homogeneous, the DMDES-DMSO-OA system consisted of two immiscible phases. In both systems, ethoxy-terminated linear oligomers ((EtO)Me2SiO(Me2SiO)nSiMe2(OEt); n=0-4, Et = C2H5, Me = CH3) and cyclic tetramer ((Me2SiO)4) were identified. The reaction mechanism for polysiloxane formation is discussed. © 1994 Kluwer Academic Publishers.

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  • Intercalation of n-Alkylamines into Perovskite-related Layered Niobic Acid HBiNb<inf>2</inf>O<inf>7</inf>·nH<inf>2</inf>O

    Teruyuki Nakato, Masato Nakade, Kazuyuki Kuroda, Chuzo Kato

    Studies in Surface Science and Catalysis   90   285 - 290  1994年  [査読有り]

     概要を見る

    n-Alkylammonium-HxBiNb2O7intercalation compounds were synthesized by the reaction of perovskite-related layered oxide HBiNb2O7·nH2O with n-alkylamines. HBiNb2O7·nH2O was not completely converted to the intercalation compounds except for the methylammonium-intercalate. The intercalating capability of HBiNb2O7·nH2O was much lower than those of other previously reported perovskite-related layered niobates such as HCa2Nb3O10. The poor reactivity was assumed to be related to unusual irreversible dehydrating behavior of HBiNb2O7·nH2O. On the other hand, the interlayer structure was similar to that of the n-alkylammonium-HxCa2Nb3O10intercalates in contrast to the difference in the reactivity. © 1994 Kodansha Ltd.

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  • PHOTOPHYSICAL PROBE STUDY OF ALKYLAMMONIUM MONTMORILLONITES

    M OGAWA, T AONO, K KURODA, C KATO

    LANGMUIR   9 ( 6 ) 1529 - 1533  1993年06月  [査読有り]

     概要を見る

    Intercalation of anthracene and pyrene into two types of alkylammonium-montmorillonites (octadecyltrimethylammonium and dioctadecyldimethylammonium types) is carried out by solid-solid reactions which we have developed recently. The arene molecules are solubilized at extremely high concentrations in the two-dimensional interlayer spaces of the alkylammonium-montmorillonites with retaining the ordered structure. Fluorescence spectra of the intercalated arenes show that two different types of adsorption occurred. The arenes in the octadecyltrimethylammonium-montmorillonite are aggregated and those in the dimethyldioctadecylamraonium-montmorillonite are rather dispersed between the alkyl chains in the interlayer spaces. The alkylammonium-montmorillonites are novel two-dimensional media to organize poorly water soluble species.

    DOI

  • PHOTOCHEMICAL BEHAVIOR OF INTERCALATION COMPOUNDS OF LAYERED NIOBATES WITH METHYLVIOLOGEN

    T NAKATO, K KURODA, C KATO

    CATALYSIS TODAY   16 ( 3-4 ) 471 - 478  1993年05月  [査読有り]

     概要を見る

    Intercalation compounds of three layered niobates with methylviologen (1,1'-dimethyl-4,4'-bipyridinium ion) were synthesized and their photochemical behavior was investigated. All the host niobates successfully intercalated methylviologen dications, and there were structural differences among the samples. UV irradiation of the intercalation compounds caused photoinduced electron transfer from the hosts to the guest to form methylviologen radical cations. The radical cations were characterized by their high stability, which had a relation to the structure of the intercalation compounds. Co-intercalation of photochemically inactive ions (K+ or propylammonium ions) with methylviologen extremely well stabilized the radical cations.

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  • Intercalation of a free-base porphyrin into layered tetratitanic acid

    Teruyuki Nakato, Yumiko Iwata, Kazuyuki Kuroda, Masao Kaneko, Chuzo Kato

    Journal of the Chemical Society, Dalton Transactions   ( 9 ) 1405 - 1409  1993年  [査読有り]

     概要を見る

    An intercalation compound of layered H2Ti4O9 with 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin (H2tmpyp4+) was synthesised by a guest-exchange method using the NPrH3+-HxTi4O9 intercalation compound as intermediate. The porphyrin is present as the free base without protonation. Its molecules are arranged with their planes inclined to the [Ti4O9]2- layers because of the high charge density of the host layers. Whereas the fluorescence spectrum of the intercalated H2tmpyp4+ indicated that the porphyrin is present as a monomer without stacked aggregation, the fluorescence decayed as rapidly as that of solid powders of H2tmpyp4+ 4I-, suggesting the porphyrin molecules interact with one another in the interlayer space.

    DOI

  • Synthesis of highly ordered mesoporous materials from a layered polysilicate

    S. Inagaki, Y. Fukushima, K. Kuroda

    Journal of the Chemical Society, Chemical Communications   ( 8 ) 680 - 682  1993年  [査読有り]

     概要を見る

    The ion exchange reaction of interlayer Na+ ions of a layered polysilicate kanemite with alkyltrimetnylammonium ions, followed by calcination, gives highly ordered mesoporous materials with a hexagonal array of uniform channels.

    DOI

  • Novel controlled luminescence of tris(2,2′-bipyridine)ruthenium(II) intercalated in a fluortetrasilicic mica with poly(vinylpyrrolidone)

    Makoto Ogawa, Misako Inagaki, Nobuhiro Kodama, Kazuyuki Kuroda, Chuzo Kato

    Journal of Physical Chemistry   97 ( 15 ) 3819 - 3823  1993年  [査読有り]

     概要を見る

    Tris(2,2′-bipyridine)ruthenium(II) (Ru(bpy)32+)-fluortetrasilicic mica (TSM)-poly(vinylpyrrolidone) (PVP) intercalation compounds were prepared, and the photoluminescent behavior of intercalated Ru(bpy)32+was investigated. The luminescence maxima of intercalated Ru(bpy)32+shifted gradually toward the blue with decreased loading of Ru(bpy)32+, reflecting the change in the polarity and/or rigidity of the microenvironment of Ru(bpy)32+, presumably caused by cointercalated PVP. Moreover, Ru(bpy)32+self-quenching was suppressed even at its high concentration loading. It was supposed that cointercalated PVP prevented self-aggregation by surrounding Ru(bpy)32+in close contact in the sterically limited interlayer spaces. © 1993 American Chemical Society.

    DOI

  • EVIDENCE FOR THE FORMATION OF BI-2(SR2-XCAX)CUOY WITH THE 2201 STRUCTURE

    S SERA, Y SUGAHARA, K KURODA, C KATO

    PHASE TRANSITIONS   41 ( 1-4 ) 205 - 208  1993年  [査読有り]

     概要を見る

    The formation of the solid solution Bi-2(Sr2-xCax)CuOy with the 2201 structure has been demonstrated by comparing its lattice parameters with those in Bi2+xSr2-xCuOy and Bi-2(Sr2-xMgx)CuOy systems. The solid-solution range of Bi-2(Sr2-xCax)CuOy has been found to be 0 less than or equal to x less than or equal to 0.15 under the present experimental conditions.

    DOI

  • Synthesis of la<inf>1-x</inf>M<inf>x</inf>TiO<inf>3</inf>(M = Na, K; 0≤x≤ 0.4) and the electrical properties

    Hiroshi Yamamoto, Tomoyuki Tahara, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Phase Transitions   41 ( 1-4 ) 137 - 141  1993年  [査読有り]

     概要を見る

    Polycrystalline materials of La1-xMxTiO3(M = Na, K;0≤x≤0.4) were prepared by solid-state reactions under an Ar atmosphere and their electrical properties were investigated as possible candidates for superconducting oxides. XRD analysis showed that the formation of orthorhombic perovskite-type compounds were obtained when × = 0 (LaTiO3) and that pseudo-cubic or cubic phases were obtained when ϗ ≥ 0.1. The lattice constants of the products decreased when × increased, suggesting the formation of solid solutions. There were small deficiencies of the alkali metals. The products in both systems showed semiconductor to metal transitions as temperature decreased when x≥0.1, and striking decreases of resistivity around 25 K were observed in both systems. © 1993, Taylor &amp; Francis Group, LLC. All rights reserved.

    DOI

  • Photochemical behavior of perovskite-related layered niobates HA2Nb3O10 (A = Ca, Sr) intercalated with methylviologen

    Teruyuki Nakato, Kazuhiko Ito, Kazuyuki Kuroda, Chuzo Kato

    Microporous Materials   1 ( 4 ) 283 - 286  1993年  [査読有り]

     概要を見る

    Intercalation compounds of layered niobates HA2Nb3O10 (A = Ca, Sr), which have perovskite-type oxide layers, with methylviologen dications have been synthesized. Although the two intercalation compounds were structurally similar, they exhibited different photochemical behavior. UV irradiation of the MV2+-intercalates caused electron transfer from the host to methylviologen dications in the HCa2Nb3O10 system, whereas photoreduction of Nb ions in the host lattice was observed in the HSr2Nb3O10 system. © 1993.

    DOI

  • PREPARATION OF AN INTERCALATION COMPOUND OF LAYERED TITANIC ACID H2TI4O9 WITH METHYLENE-BLUE

    T NAKATO, Y IWATA, K KURODA, C KATO

    JOURNAL OF INCLUSION PHENOMENA AND MOLECULAR RECOGNITION IN CHEMISTRY   13 ( 3 ) 249 - 256  1992年07月  [査読有り]

     概要を見る

    Intercalation of methylene blue into layered titanic acid H2Ti4O9 was examined by a guest exchange method using a propylammonium-HxTi4O9 intercalation compound as the intermediate. Methylene blue cations were arranged in the interlayer space obliquely to the layer surface. The visible spectrum of the intercalation compound suggested that the methylene blue cations were in an associated state in the interlayer spar-e of H2Ti4O9. The intercalated methylene blue cations underwent a reversible electrochemical redox reaction in the dark, indicating that intercalation compounds of H2Ti4O9 can be applied to a modified electrode.

    DOI

  • Luminescence of Tris(2,2'-bipyridine)ruthenium(II) Incorporated in Mica-Organic Polymer Intercalation Compounds

    Makoto Ogawa, Misako Inagaki, Kazuyuki Kuroda, Chuzo Kato, Nobuhiro Kodama

    Molecular Crystals and Liquid Crystals Science and Technology. Section A. Molecular Crystals and Liquid Crystals   216 ( 1 ) 141 - 144  1992年06月  [査読有り]

     概要を見る

    Luminescence of Ru(bpy)32+ incorporated in a swelling mica-poly(vinylpyrrolidone)(PVP) intercalation compound was investigated. In the sterically limited interlayer space of mica, Ru(bpy)32+ was forced to be surrounded by PVP in close contact, showing a novel controlled luminescent behavior. © 1992, Taylor &amp
    Francis Group, LLC. All rights reserved.

    DOI

  • Syntheses of Intercalation Compounds of Layered Niobates with Methylviologen and Their Photochemical Behavior

    Teruyuki Nakato, Kazuyuki Kuroda, Chuzo Kato

    Chemistry of Materials   4 ( 1 ) 128 - 132  1992年02月  [査読有り]

     概要を見る

    Intercalation of methylviologen (1, 1ʹ-dimethyl-4, 4ʹ-bipyridinium ion) into two layered niobates (K4Nb6O17 and HNb3O8) and the photochemical behavior of the resulting compounds were investigated. UV irradiation of the intercalation compounds caused photoinduced electron transfer from the hosts to the guest
    the formation of methylviologen radical cations was observed. This behavior was affected by the structure of the intercalation compounds. The radical cations were less stable in HNb3O8, where they were more densely packed, than in K4Nb6O17. Co-intercalation of photoinactive species with methylviologen significantly stabilized the radical cations in both of the hosts. The differences in the photochemistry apparently arises from structural differences. © 1992, American Chemical Society. All rights reserved.

    DOI

  • Clay-organic nano-composite; preparation of a kaolinite-poly (vinylpyrrolidone) intercalation compound

    Yoshiyuki Sugahara, Tomohide Sugiyama, Tetsuji Nagayama, Kazuyuki Kuroda, Chuzo Kato

    Nippon Seramikkusu Kyokai Gakujutsu Ronbunshi/Journal of the Ceramic Society of Japan   100 ( 1160 ) 413 - 416  1992年  [査読有り]

     概要を見る

    A kaolinite-poly(vinylpyrrolidone) intercalation compound has been prepared by the intercalation of an N-vinyl-2-pyrrolidone monomer (VP) and subsequent heat treatment. The intercalation of VP was achieved by treating a kaolinite-ammonium acetate intercalation compound with a VP aqueous solution. The basal spacing decreased from 14.2 to 12.6 , and infra-red spectroscopy (IR) and solid-state 13C nuclear magnetic resonance with cross polarization and magic angle spinning techniques (13C CP/MAS NMR) showed the displacement of ammonium acetate by VP. When the kaolinite-VP intercalation compound was heated at 200°C for 1 h, the basal spacing did not vary. The IR and 13C CP/MAS NMR spectra showed the disappearance of vinyl groups and became similar to those of poly(vinylpyrrolidone) (PVP). These results clearly indicate the polymerization of VP between the layers of kaolinite.

    DOI

  • PREPARATION OF ALUMINUM NITRIDE FROM POLY(ISOPROPYLIMINOALANE)

    Y SUGAHARA, T ONUMA, O TANEGASHIMA, K KURODA, C KATO

    NIPPON SERAMIKKUSU KYOKAI GAKUJUTSU RONBUNSHI-JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   100 ( 1 ) 101 - 103  1992年01月  [査読有り]

     概要を見る

    Aluminum nitride (AIN) was formed by two-step pyrolysis of poly (isopropyliminoalane) in Ar. The product pyrolyzed at 1000-degrees-C was an amorphous material. Solid-state Al-27-nuclear magnetic resonance spectroscopy (NMR) showed that an AlN-like structure was present in the product. Heat treatment of the pyrolyzed product at 1600-degrees-C yielded crystalline AlN from the amorphous material.

    DOI

  • 29Si-NMR study of hydrolysis and initial polycondensation processes of organoalkoxysilanes. I. Dimethyldiethoxysilane

    Yoshiyuki Sugahara, Seigo Okada, Kazuyuki Kuroda, Chuzo Kato

    Journal of Non-Crystalline Solids   139   25 - 34  1992年01月  [査読有り]

     概要を見る

    The hydrolysis and initial polycondensation processes of dimethyldiethoxysilane (DMDES) have been investigated by high-resolution29Si nuclear magnetic resonance spectroscopy (NMR) in a variety of acidic system (DMDES:ethyl alcohol:water:HCl = 1:4:x:y; x = 2 or 4, 1 × 10-5≤ y ≤ 1 × 10-2). On the basis of the behavior of signal intensities, those due to the following monomers and oligomers have been identified: Me2Si(OEt)(OH), Me2Si(OH)2, Me2(HO)SiOSi(OH)Me2, Me2(EtO)SiOSi(OH)Me2, Me2(EtO)SiOSiMe2OSi(OH)Me2, Me2(HO)SiOSiMe2OSi(OH)Me2, (Me2SiO)3, Me2(HO)SiO(SiMe2O)2Si(OH)Me2, and (Me2SiO)4(where Me = CH3, Et = C2H5). It was shown that the substitution of the hydroxyl group for the ethoxy group resulted in an upfield shift of a signal, which was not consistent with the previous observations in tetra-functional alkoxysilane systems. In the course of the polycondensation process, cyclization reactions became predominant to form a considerable amount of the cyclic tetramer directly from the completely hydrolyzed dimer (Me2(HO)SiOSi(OH)Me2). © 1992 Elsevier Science Publishers B.V.

    DOI

  • Polysiloxane formation from a tetraethoxysilane-ethyl alcohol-oxalic acid system

    Yoshiyuki Sugahara, Shuji Sato, Kazuyuki Kuroda, Chuzo Kato

    Journal of Non-Crystalline Solids   147-148 ( C ) 24 - 29  1992年  [査読有り]

     概要を見る

    Polysiloxane formation in a tetraethoxysilane (TEOS)-ethyl alcohol (EtOD(H))-oxalic acid (OA) system without the addition of water was investigated by 29Si nuclear magnetic resonance spectroscopy (29Si-NMR). In the system with TEOS:EtOD(H):OA = 1:6:1, considerable amounts of linear oligosiloxanes possessing only ethoxy groups formed, and (EtO)3SiOSi(OEt)3, (EtO)3SiOSi(OEt)2OSi(OEt)3, and (EtO)3Si(OSi(OEt)2)2OSi(OEt)3 were identified. When the amount of OA increased to TEOS:EtOD(H):OA = 1:6:2, the polymerization rate increased considerably. The observed Si-species scarcely possessed hydroxyls, suggesting unique siloxane formation in this system. © 1992 Elsevier Science Publishers B.V. All rights reserved.

    DOI

  • Solid-state intercalation of acrylamide into smectites and Na-taeniolite

    Makoto Ogawa, Yasuyuki Nagafusa, Kazuyuki Kuroda, Chuzo Kato

    Applied Clay Science   7 ( 4 ) 291 - 302  1992年  [査読有り]

     概要を見る

    Various clay minerals of the smectite group could form intercalation compounds with acrylamide by solid-solid reaction at room temperature and within a few minutes of contacting the reactants. Taeniolite, a synthetic fluor-mica with a higher layer charge density than smectites, gave an only incomplete intercalation. The propensity of the minerals for intercalating acrylamide was correlated with their reactivity towards ethylene glycol. Because of their rapidity and simplicity, solid-solid reactions provide a new way of introducing organic species into the interlayer spaces of smectites. © 1992.

    DOI

  • Solid-state intercalation of naphthalene and anthracene into alkylammonium-montmorillonites

    Makoto Ogawa, Hidenori Shirai, Kazuyuki Kuroda, Chuzo Kato

    Clays and Clay Minerals   40 ( 5 ) 485 - 490  1992年  [査読有り]

     概要を見る

    Intercalation of naphthalene and anthracene into alkyltrimethylammonium (CnH2n+1(CH3)3N+
    n = 8, 12, 14, 16, and 18)-montmorillonites was carried out by novel solid-solid reactions at room temperature. Octyltrimethylammonium(C8)-montmorillonite did not form an intercalation compound with either naphthalene or anthracene. Naphthalene was intercalated into both dodecyltrimethylammonium(C12)- and octadecyltrimethylammonium(C18)-montmorillonites to give intercalation compounds. On the other hand, the solid-solid reaction between dodecyltrimethylammonium(C12)- or tetradecyltrimethylammonium(C14)-montmorillonite and anthracene gave only partly intercalated compounds while hexadecyltrimethylammonium(C16)- and octadecyltrimethylammonium(C18)-montmorillonites gave single phase intercalation compounds. The hydrophobic interactions between alkylammonium-montmorillonites and the aromatic compounds are thought to be the driving force for the solid-state intercalation. The extent of the increase in the basal spacing may also be involved in the different reactivity. © 1992, The Clay Minerals Society.

    DOI

  • Photochemical hole burning of 1,4-dihydroxyanthraquinone intercalated in a pillared layered clay mineral

    Makoto Ogawa, Tokuhiko Handa, Kazuyuki Kuroda, Chuzo Kato, Toshiro Tani

    Journal of Physical Chemistry   96 ( 20 ) 8116 - 8119  1992年  [査読有り]

     概要を見る

    A tetramethylammonium-saponite-1,4-dihydroxyanthraquinone intercalation compound was prepared and a persistent spectral zero-phonon hole was obtained at liquid helium temperatures by Kr+ laser light irradiation (520.8 nm). This is the first example of persistent hole formation of 1,4-dihydroxyanthraquinone in crystalline inorganic matrices. In spite of the high concentration of 1,4-dihydroxyanthraquinone (ca. 1.5 mol kg-1), a narrow hole with the initial width of 0.25 cm-1 (4.6 K) was obtained with no distinct decrease in burning efficiency (&gt
    1.0 × 10-4) if compared with those doped in ordinary polar polymers or organic glasses. The microscopic geometry of the compound is discussed on the basis of hole formation properties as well as X-ray powder diffraction and 13C NMR observation. © 1992 American Chemical Society.

    DOI

  • Intercalation of 2, 2′-Bipyridine and Complex Formation in the Interlayer Space of Montmorillonite by Solid-Solid Reactions

    Makoto Ogawa, Toshinobu Hashizume, Kazuyuki Kuroda, Chuzo Kato

    Inorganic Chemistry   30 ( 3 ) 584 - 585  1991年02月  [査読有り]

    DOI

  • Preparation of intercalation compounds between V2O5 gel and bipyridyl metal complexes

    Teruyuki Nakato, Tsuyoshi Ise, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Materials Research Bulletin   26 ( 4 ) 309 - 315  1991年  [査読有り]

     概要を見る

    The intercalation of tris-bipyridyl metal complexes (M(bpy)3 2+, M=Ru, Ni, and Co) into the interlayer region of vanadium pentoxide gel (V2O5·nH2O) was confirmed for the first time. The intercalation of the guest species was conducted by the reaction of the complexes with undried V2O5 gel. The saturated amount of adsorbed M(bpy)3 2+ was less than the ion exchange capacity of the V2O5 gel because of bulkiness of M(bpy)3 2+. The transition temperature to orthorhombic V2O5 was higher than that of original V2O5 gel, indicating the stabilization of the layered structure by the intercalation. © 1991.

    DOI

  • POLYMERIZATION OF HYDROLYSIS PRODUCTS OF METHYLTRIETHOXYSILANE IN AQUEOUS-SOLUTIONS

    HASEGAWA, I, S SAKKA, Y SUGAHARA, K KURODA, C KATO

    NIPPON SERAMIKKUSU KYOKAI GAKUJUTSU RONBUNSHI-JOURNAL OF THE CERAMIC SOCIETY OF JAPAN   98 ( 7 ) 647 - 652  1990年  [査読有り]

     概要を見る

    The structure and distribution of chemical species of hydrolysis and polycondensation products of methyltriethoxysilane in aqueous solutions containing sodium ions have been studied with the trimethylsilylation technique and by 29Si n. m. r. spectroscopy. 11 trimethylsilylated derivatives of the products were obtained from the solutions. The recovery of methyltrisilanol (CH3Si(OH)3) was higher than that of the monosilicic acid in an aqueous sodium silicate solution at the same Si concentration and the same sodium ion-to-silicon molar ratio, suggesting that polymerization of silicate anions is easier than that of hydrolysis products of methyltriethoxysilane in aqueous solutions. On the basis of the distribution, assignment of 29Si n. m. r. peaks corresponding to low-molecular weight species formed from methyltriethoxysilane is discussed.

    DOI

  • Direct synthesis of intercalation compounds between a layered double hydroxide and an anionic dye

    In Yong Park, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Dalton Transactions   ( 10 ) 3071 - 3074  1990年  [査読有り]

     概要を見る

    Intercalation compounds between a layered double hydroxide and an anionic dye were directly synthesized by hydrolysis of mixed solutions of aluminium nitrate, magnesium nitrate, and the anionic dyes (indigo carmine or new coccine). The intercalated indigo carmine anions are possibly arranged with their molecular planes perpendicular to the hydroxide layers. The basal spacings of the new coccine intercalates suggested that the configuration of the new coccine anions in the interlayers changed upon washing. Intercalation of the dyes by anion exchange from layered double hydroxides with NO3- or Cl- as the interlayer anions was also conducted for comparison.

    DOI

  • Synthesis of layered polysilicic acid-acrylamide intercalation compounds and polymerization in the interlayer spaces

    T. Yanagisawa, C. Yokoyama, K. Kuroda, C. Kato

    Bulletin of the Chemical Society of Japan   63 ( 1 ) 47 - 50  1990年  [査読有り]

     概要を見る

    Layered polysilicic acid-arylamide intercalation compounds were synthesized by the reaction of H-magadiite (H2Si14O29.xH2O) and H-kenyaite (H2Si20O41.xH2O) with acrylamide saturated aqueous solutions. The formation of the intercalation compounds were ascertained by X-ray powder diffraction, IR, 13C-CP MAS NMR, DTA, and chemical analysis. However, when H-magadiite was used, a part of the intercalated acrylamide molecules was oligomerized during the intercalation. A heat treatment of the layered polysilicic acid-acrylamide intercalation compounds led to a polymerization of the acrylamide in the interlayer spaces.

    DOI

  • Chemical and electrochemical intercalation of a viologen into V2O5 xerogel films

    Ikou Kato, Teruyuki Nakato, Kazuyuki Kuroda, Chuzo Kato

    Colloids and Surfaces   49 ( C ) 241 - 245  1990年  [査読有り]

     概要を見る

    Heptylviologen was intercalated into V2O5 xerogel films by chemical and electrochemical methods. Chemical intercalation occurred by the reaction of a V2O5 xerogel film with a propylene carbonate (PC) solution of heptylviologen (HV). The viologen was present as a solvated form in the interlayer of V2O5 gel. A reversible intercalation-deintercalation of HV was carried out by electrochemical reduction-oxidation of the V2O5 xerogel film in a PC solution of HV. The electrochemical intercalation took place only when the interlayer region of V2O5 gel was expanded by PC. © 1990.

    DOI

  • The preparation of alkyltrimethylammonium-kanemite complexes and their conversion to microporous materials

    T. Yanagisawa, T. Shimizu, K. Kuroda, C. Kato

    Bulletin of the Chemical Society of Japan   63 ( 4 ) 988 - 992  1990年  [査読有り]

    DOI

  • Preparation of complex copper aluminum double hydroxide phases from copper (II) ammine complex solutions

    In Yong Park, Kazuyuki Kuroda, Chuzo Kato

    Solid State Ionics   42 ( 3-4 ) 197 - 203  1990年  [査読有り]

     概要を見る

    A complex copper aluminum double hydroxide phase with sulfate anions (sulfate phase), Cu0.67Al0.33(OH)2(SO4)0.15(CO3) 0.015·0.5H2O, was prepared by adding a mixed solution of aluminum sulfate and sodium hydroxide to a copper (II) ammine complex solution. Although the X-ray powder diffraction pattern of the sulfate phase was different from those of hydrotalcite-like compounds, the SEM, IR, thermoanalytical data, and anion exchange behavior suggested that the structure was lamellar. The basal spacing depended on the interlayer anion and increased in the following sequence: CO2- 3 s ̌Cl-&lt
    Br-&lt
    SO2- 4&lt
    NO- 3 &lt
    CH3OO-. Thermal decomposition processes were also investigated. © 1990.

    DOI

  • Organic derivatives of layered polysilicates III. Reaction of magadiite and kenyaite with allydimethylchlorosilane

    Tsuneo Yanagisawa, Masatoshi Harayama, Kazuyuki Kuroda, Chuzo Kato

    Solid State Ionics   42 ( 1-2 ) 15 - 19  1990年  [査読有り]

     概要を見る

    Organic derivatives of layered polysilicate Na-magadiite (Na2Si14O29·xH2O) and K-kenyaite (K2Si20O41·xH2O) were synthesized by by the reaction of the alkyltrimethylammonium-polysilicate intercalation compounds with allyldimethylchlorosilane as the silylating reagent. A part of silanol groups on the SiO2 layer was silylated and furthermore the allyl groups were eliminated during the reaction to form Si(CH3)2OH groups. © 1990.

    DOI

  • CARBOTHERMAL REDUCTION PROCESS OF PRECURSORS DERIVED FROM ALKOXIDES FOR SYNTHESIS OF BORON-DOPED SIC POWDER

    Y SUGAHARA, Y TAKEDA, K KURODA, C KATO

    JOURNAL OF MATERIALS SCIENCE LETTERS   8 ( 8 ) 944 - 946  1989年08月  [査読有り]

    DOI

  • Kaolinite-pyridine intercalation compound derived from hydrated kaolinite

    Yoshiyuki Sugahara, Shigeo Satokawa, Ken Ichi Yoshioka, Kazuyuki Kuroda, Chuzo Kato

    Clays and Clay Minerals   37 ( 2 ) 143 - 150  1989年  [査読有り]

     概要を見る

    A kaolinite-pyridine intercalation compound was prepared using hydrated kaolinite as an intermediate. Hydrated kaolinite having a basal spacing of 10 angstrom was treated with pyridine to form a well-ordered intercalation compound having a basal spacing of 12.0 angstrom. Infrared spectroscopy indicated the presence of hydrogen bonding between the hydroxyls of the kaolinite and the pyridine. 29Si nuclear magnetic resonance spectroscopy with cross polarization and magic-angle spinning revealed that intercalated pyridine affected the environment of silicon. The mono-substituted pyridine derivatives were also intercalated with hydrated kaolinite. On the basis of the basal spacings of the intercalation compounds and the stabilities of the derivatives between the layers, the pyridine appeared to be in an approximately perpendicular position, with the nitrogen facing the gibbsitic sheets.

    DOI

  • Preparation of nitrides from 1:1 type clay minerals by carbothermal reduction

    Yoshiyuki Sugahara, Jyunji Miyamoto, Kazuyuki Kuroda, Chuzo Kato

    Applied Clay Science   4 ( 1 ) 11 - 26  1989年  [査読有り]

     概要を見る

    In order to investigate the possibility of the use of 1:1 type clay minerals as raw materials for nitride production, kaolinite and antigorite were converted into nitrides by carbothermal reduction. Kaolinite or antigorite was mixed with carbon in two separate experiments. The resulting mixture was heated in N2. Kaolinite was converted into β'-sialon and AIN. Kaolinite was initially transformed into cristobalite and mullite, which were then reduced. In addition to the nitrides, SiC and α-Al2O3 also formed as the reactions proceeded. Essentially, both the SiO2 and Al2O3 components were converted into nitrides and oxynitrides by carbothermal reduction. From the antigorite-carbon mixture, α- and β-Si3N4 were obtained. Forsterite initially crystallized and was reduced. Additionally, MgSiN2 and MgO formed during the conversion. α-Fe and FexSi were also detected. MgSiN2 seemed to act as an intermediate for Si3N4 formation. Therefore, all the Mg-containing phases can not be present as nitrides finally
    magnesium was lost as the reactions proceeded. © 1989.

    DOI

  • Preparation of V2O5 gel-viologen intercalation compounds

    Teruyuki Nakato, Ikuo Kato, Kazuyuki Kuroda, Chuzo Kato

    Journal of Colloid And Interface Science   133 ( 2 ) 447 - 451  1989年  [査読有り]

     概要を見る

    Methyl, heptyl, and benzyl viologens were intercalated into the interlayer space of vanadium pentoxide gel (V2O5 · nH2O) by ion exchange. Intercalated methyl and benzyl viologens were present in monolayer arrangements in which the viologens lie parallel to the oxide layer. Heptyl viologens were intercalated in a transversal arrangement with respect to the host layer. The difference among those arrangements in the interlayer region was ascribed to the different sizes of the dications used. © 1989 Academic Press, Inc.

    DOI

  • Formation of hydrotalcite-acrylate intercalation compounds and their heat-treated products

    M. Tanaka, I. Y. Park, K. Kuroda, C. Kato

    Bulletin of the Chemical Society of Japan   62 ( 11 ) 3442 - 3445  1989年  [査読有り]

    DOI

  • Photoreduction of methylviologen in the interlayer of K&lt;inf&gt;4&lt;/inf&gt;Nb &lt;inf&gt;6&lt;/inf&gt;O&lt;inf&gt;17&lt;/inf&gt;

    Teruyuki Nakato, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Chemical Communications   ( 16 ) 1144 - 1145  1989年  [査読有り]

     概要を見る

    Methylviologen was directly intercalated into the interlayer space of K&lt
    inf&gt
    4&lt
    /inf&gt
    Nb&lt
    inf&gt
    6&lt
    /inf&gt
    O&lt
    inf&gt
    17&lt
    /inf&gt

    the u.v. irradiated intercalation compound showed a stable blue colour even under an air atmosphere.

    DOI

  • Silicate anions formed in tetramethylammonium silicate methanolic solutions as studied by &lt;sup&gt;29&lt;/sup&gt;Si nuclear magnetic resonance

    Isao Hasegawa, Sumio Sakka, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Chemical Communications   ( 4 ) 208 - 210  1989年  [査読有り]

     概要を見る

    The Si&lt
    inf&gt
    8&lt
    /inf&gt
    O&lt
    inf&gt
    20&lt
    /inf&gt
    &lt
    sup&gt
    8-&lt
    /sup&gt
    silicate anion is selectively formed in tetramethylammonium silicate methanolic solution from the SiO &lt
    inf&gt
    4&lt
    /inf&gt
    &lt
    sup&gt
    4-&lt
    /sup&gt
    silicate anion or at the expense of Si &lt
    inf&gt
    6&lt
    /inf&gt
    O&lt
    inf&gt
    15&lt
    /inf&gt
    &lt
    sup&gt
    6-&lt
    /sup&gt
    and highly cross-linked polymeric silicate anions which are once formed.

    DOI

  • Synthesis of a viologen-tetratitanate intercalation compound and its photochemical behaviour

    Hirokatsu Miyata, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases   84   2677 - 2682  1988年12月  [査読有り]

     概要を見る

    Methyl viologen has been intercalated into the interlayer space of layered tetratitanic acid by a method involving the displacement of guest molecules using an n-propylammonium tetratitanate intercalation compound. The viologen tetratitanate intercalation compound changed colour to blue when irradiated by a mercury lamp under vacuum conditions or a nitrogen atmosphere. The formation of radical cations was confirmed by visible and e.s.r. spectroscopy. The electron donor for the photoreduction is thought to originate from the tetratitanate layers. The colour was stable as long as the vacuum conditions were maintained, and fading did not occur rapidly even after the introduction of air, requiring &gt; 1 h for the colour to fade completely. These results indicate remarkable stability of the viologen radical cations in this intercalation compound.

    DOI

  • THE CARBOTHERMAL REDUCTION PROCESS OF A MONTMORILLONITE POLYACRYLONITRILE INTERCALATION COMPOUND

    Y SUGAHARA, K KURODA, C KATO

    JOURNAL OF MATERIALS SCIENCE   23 ( 10 ) 3572 - 3577  1988年10月  [査読有り]

     概要を見る

    To develop a carbothermal reduction process for the conversion of oxides to nitrides, a montmorillonite-polyacrylonitrile (PAN) intercalation compound was applied as a precursor. Montmorillonite-carbon mixtures were heated as well as the intercalation compound in N2 at 1100 to 1500° C for comparison. From the intercalation compound, β-sialon, AIN and SiC were mainly formed. Oxides were reduced without their crystallization. On the other hand, in the reactions of the mixtures, some oxides and other kinds of nitride were obtained as principal products in addition to these phases. Furthermore, the intercalation compound was more favourable than the mixtures having a larger amount of carbon in terms of the reduction of oxides and the formation of nitrides. These observations suggest that the layered structure of the intercalation compound led to an effective and specific carbothermal reduction process. © 1988 Chapman and Hall Ltd.

    DOI

  • NITRIDE FORMATION BY THE CARBOTHERMAL REDUCTION OF A ZEOLITE POLYACRYLONITRILE INCLUSION COMPOUND

    Y SUGAHARA, H HIRAIWA, K KURODA, C KATO

    JOURNAL OF MATERIALS SCIENCE   23 ( 9 ) 3181 - 3186  1988年09月  [査読有り]

     概要を見る

    An inclusion compound between zeolite and polyacrylonitrile has been applied as a precursor for the carbothermal reduction process. By heat treatment at 1400 to 1600° C in N2, β-sialon was mainly obtained. The X phase, α-Si3N4, the 15R-AlN phase, AIN, and mullite also formed under certain firing conditions. On the other hand, α-Si2N4was detected as the principal crystalline phases as well as β-sialon in the products from zeolite-carbon mixtures. Hence, the use of the inclusion compound was advantageous for β-sialon production in the conversion of zeolite to nitrides. © 1988 Chapman and Hall Ltd.

    DOI

  • THE FORMATION OF SIC-AIN SOLID-SOLUTION BY THE CARBOTHERMAL REDUCTION PROCESS OF MONTMORILLONITE

    Y SUGAHARA, K SUGIMOTO, H TAKAGI, K KURODA, C KATO

    JOURNAL OF MATERIALS SCIENCE LETTERS   7 ( 7 ) 795 - 797  1988年07月  [査読有り]

    DOI

  • Preparation of Silicon Carbide and Aluminum Silicon Carbide from a Montmorillonite–Polyacrylonitrile Intercalation Compound by Carbothermal Reduction

    Yoshiyuki Sugahara, Ken‐Ichi ‐I Sugimoto, Kazuyuki Kuroda, Chuzo Kato

    Journal of the American Ceramic Society   71 ( 7 ) 325 - 327  1988年  [査読有り]

     概要を見る

    Both silicon carbide and aluminum silicon carbide have simultaneously been obtained directly from naturally occurring aluminosilicate by carbothermal reduction for the first time. A precursor of a montmorillonite–polyacrylonitrile (PAN) intercalation compound was heated at 1700°C in Ar. For comparison, montmorillonite–carbon mixtures were similarly heated. α‐SiC, β‐SiC, and Al4Si2C5 formed from the montmorillonite–PAN intercalation compound. Mainly α‐Al4SiC4 was obtained with ternary carbides from the montmorillonite–carbon mixtures in addition to a large amount of β‐SiC. Hence, aluminum silicon carbide formation was affected by the mixing condition of the starting materials. Copyright © 1988, Wiley Blackwell. All rights reserved

    DOI

  • Evidence for the formation of interlayer polyacrylonitrile in kaolinite

    Y. Sugahara, S. Satokawa, K. Kuroda, C. Kato

    Clays &amp; Clay Minerals   36   343 - 348  1988年01月  [査読有り]

     概要を見る

    A kaolinite-polymer intercalation complex was apparently formed for the first time by the polymerization of acrylonitrile between the kaolinite layers. A kaolinite-ammonium acetate intercalation complex was dispersed in acrylonitrile monomer. The monomer was apparently incorporated between the layers by displacing intercalated ammonium acetate. After the removal of excess monomer, the intercalation complex was heated to cause polymerization. The resulting kaolinite-polyacrylonitrile (PAN) intercalate showed a basal spacing of ~13-14 A. On heating the complex at 220°C for 1 hr in air, the spacing decreased slightly. The hydrogen bond between the hydroxyls of kaolinite and probably the C≡N group of PAN was not affected after heating at 220°C. Even after heating at 400°C, the layers expanded. Because the starting kaolinite-ammonium acetate intercalation complex decomposed at a much lower temperature, these observations strongly suggest the presence of PAN between the layers. -Authors

    DOI

  • The preparation of boron-doped silicon carbide powder by the carbothermal reduction of oxides derived from the hydrolyzed methyltriethoxysilane

    Yoshiyuki Sugahara, Yasuharu Takeda, Kazuyuki Kuroda, Chuzo Kato

    Journal of Non-Crystalline Solids   100 ( 1-3 ) 542 - 546  1988年  [査読有り]

     概要を見る

    A precursor prepared from a methyltriethoxysilane ((CH3)Si(OC2H5)3, MTES)-B(OC2H5)3-polyacrylonitrile (PAN) composition was used for the synthesis of boron-doped SiC by carbothermal reduction. Initially, MTES was hydrolyzed with HCl (MTES: H2O: HCl = 1 : 1 : 0.01) for 1 h in a sealed vessel. The number-average molecular weight measurement and a NMR spectrum revealed that the species in the solution were mainly oligometric. With the addition of B(OC2H5)3, no significant changes in the distribution of the Si containing species were detected. The mixing of the hydrolyzed solution with a PAN-dimethylsulfoxide solution led to a homogeneous solution. After the evaporation of the solvents and the subsequent heat treatment at 220° C, brown precursor powder was obtained. By the heat treatment at 1600° C in Ar, it was converted to boron-doped SiC powder. © 1988.

    DOI

  • Synthesis of methylviologen-HTiNbO5 intercalation compound and its photochemical behavior

    Teruyuki Nakato, Hirokatsu Miyata, Kazuyuki Kuroda, Chuzo Kato

    Reactivity of Solids   6 ( 2-3 ) 231 - 238  1988年  [査読有り]

     概要を見る

    A novel intercalation compound composed of layered titanoniobic acid (HTiNbO5) and methylviologen was synthesized and its photochemical behavior was investigated. Although methylviologen could not be intercalated into the interlayer region of titanoniobic acid directly, the intercalation compound was obtained by guest exchange with the propylammonium-HTiNbO5 intercalation compound. When the viologen intercalated compound was irradiated by UV light under an N2 atmosphere or under a vacuum, the compound turned blue. Visible spectroscopy and ESR indicated the formation of viologen radical cations. The phenomenon was thought to be due to the electron transfer from the oxygen-deficient layered oxide to the viologen. The oxidation of the viologen radical cations did not occur under O2-free conditions
    therefore the oxygen was responsible for the bleaching. © 1988.

    DOI

  • Organic derivatives of layered polysilicates. I. Trimethylsilylation of magadiite and kenyaite

    Tsuneo Yanagisawa, Kazuyuki Kuroda, Chuzo Kato

    Reactivity of Solids   5 ( 2-3 ) 167 - 175  1988年  [査読有り]

     概要を見る

    Organic derivatization of layered polysilicates (magadiite Na2Si14O29·xH2O and kenyaite K2Si20O41·xH2O) was performed by reaction of the tetraalkylammonium polysilicate intercalation compounds with chlorotrimethylsilane ((CH3)3SiCl) as the silylating agent. The formation of the organic derivatives was confirmed by X-ray powder diffraction, IR, 29Si MAS NMR, and elemental analysis, and revealed the bonding between the trimethylsilyl groups and the interlayer silanol groups. The advantage of using tetraalkylammonium polysilicate intercalation compounds as intermediates for organic derivatization is elucidated. © 1988.

    DOI

  • AlN formation from a hydrotalcite-polyacrylonitrile intercalation compound by carbothermal reduction

    Yoshiyuki Sugahara, Norimasa Yokoyama, Kazuyuki Kuroda, Chuzo Kato

    Ceramics International   14   163 - 167  1988年01月  [査読有り]

     概要を見る

    As a precursor for AlN production by carbothermal reduction, a hydrotalcite (layered magnesium-aluminum double hydroxide)-polyacrylonitrile (PAN) intercalation compound has been prepared for the first time. After the layers were expanded by the replacement of the interlayer anions with the CH3(CH2)11OSO3-ions, the acrylonitrile monomer was intercalated and subsequently polymerized. By the heat treatments at 1100°C-1600°C in N2, AlN, MgO and MgS formed. MgO was detected in the products heated up to 1300°C. MgS formation was observed in the reactions below 1500°C. On heating at 1600°C, single phase submicron AlN grains were obtained. © 1988.

    DOI

  • The formation of β-sialon in the carbothermal reduction process of montmorillonite-polyacrylonitrile intercalation compounds at 1100°C

    Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Ceramics International   14 ( 1 ) 1 - 5  1988年  [査読有り]

     概要を見る

    Only β-sialon was obtained from n-alkylammonium-montmorillonite-polyacrylonitrile (PAN) intercalation compounds in the carbothermal reduction process at 1100°C in N2. Very little oxide crystallized during the conversion. However, an amorphous phase was still present after treatment for 6 h. The main constituent metals in montmorillonite (Si, Al, Mg, and Fe) were mostly retained during the treatment. Since similar XRD patterns were obrained from two kinds of intercalation compounds, having different carbon contents, the suppression of the formation of other phases was not subject to the amount of carbon. When a montmorillonite-carbon mixture having a larger amount of carbon was heated at 1150°C for 6 h, oxides were mainly formed. Therefore, the intimate mixing in the 2D structure of the intercalation compounds resulted in a lower threshold temperature for β-sialon formation, at which other phases did not form. © 1988.

    DOI

  • Synthesis of montmorillonite-viologen intercalation compounds and their photochromic behaviour

    Hirokatsu Miyata, Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases   83   1851 - 1858  1987年12月  [査読有り]

     概要を見る

    The photochemical properties of four different viologen di-cations (V2+,1,1′-dipropyl-, 1,1′-diheptyl-, 1,1′-diphenylmethyl- and 1,1′-diphenylethyl-4,4′-bipyridinium di-cations) intercalated into the interlayer space of montmorillonite have been studied. The colour of the intercalation compounds which were co-intercalated by poly(vinyl pyrrolidone) (PVP) changed to blue when irradiated by a mercury lamp, showing the formation of the radical cations. Their characteristic absorptions appeared at ca. 610 and 400 nm in their visible spectra. Since the viologens were present in their cationic forms in the interlayer space it was thought that PVP acted as an electron donor for the photochemical reduction of the viologens. The intensity decay of the radical cations was very slow in comparison with the species in PVP matrices, indicating their remarkable stability.

    DOI

  • The effect of tetramethylammonium ions on the distribution of silicate species in the methanolic solutions

    Isao Hasegawa, Sumio Sakka, Kazuyuki Kuroda, Chuzo Kato

    Journal of Molecular Liquids   34 ( 4 ) 307 - 315  1987年  [査読有り]

     概要を見る

    The effect of the addition of tetramethylammonium ions on the distribution of silicate species in the methanolic solutions was studied by the trimethylsilylation technique. Tetramethylammonium ions affected silicate species formed in the hydrolysis of tetraethoxysilane, causing the singular formation of the cubic octameric silicate species in the methanolic solution. The recovery was higher in the methanolic solution than in the aqueous system. It was found that the presence of water was necessary for the singular formation, suggesting an interaction among silicate species, tetramethylammonium ions and water. It was also found that the formation of the cubic octamer started immediately after preparation of the solution. © 1987.

    DOI

  • Trimethylsilylation of the hydrolysed and polycondensed products of methyltriethoxysilane

    Isao Hasegawa, Sumio Sakka, Kazuyuki Kuroda, Chuzo Kato

    Journal of Chromatography A   410 ( C ) 137 - 143  1987年  [査読有り]

     概要を見る

    Trimethylsilylation was applied to the hydrolysed and polycondensed products of methyltriethoxysilane in an aqueous solution containing sodium ions. Five trimethylsilylated derivatives of methylsilsesquioxanes present in the solution were detected by gas chromatography and identified by combined gas chromatograph-mass spectrometry. © 1987.

    DOI

  • SYNTHESES OF NITRIDE AND CARBIDE CERAMICS FROM INTERCALATION COMPOUNDS BY CARBOTHERMAL REDUCTION.

    Kazuyuki Kuroda, Yoshiyuki Sugahara, Chuzo Kato

    British Ceramic Proceedings     15 - 20  1986年10月  [査読有り]

     概要を見る

    To establish a new method for the carbothermal reduction process, the conversion of the montmorillonite-polyacrylonitrile (PAN) intercalation compound to nitride and carbide ceramics was studied. In the case of Ar atmosphere, the formation of SiC was observed above 1200 degree C. alpha -SiC was detected above 1300 degree C, while beta -SiC was formed above 1200 degree C. As oxides, Mg-Al-O compound was detected above 1300 degree C. On the other hand, the formation of beta -sialon and SiC was observed by the treatment in N//2 atmosphere above 1200 degree C. AlN was also detected above 1300 degree C. In these processes, the reaction route became unique because of preventing the crystallization of oxides. This fact was ascribed to the presence of PAN in the interlayer space.

  • NITRIDATION OF SEPIOLITE BY CARBOTHERMAL REDUCTION

    Y SUGAHARA, K KURODA, C KATO

    JOURNAL OF MATERIALS SCIENCE LETTERS   4 ( 7 ) 928 - 931  1985年  [査読有り]

    DOI

  • Preparation of mixed isopropyl/trimethylsilyl derivatives of boric acid, (Me3SiO)nB(OiPr)3-n(n = 1-3), and their GC-M

    Hiroaki Wada, Shunji Araki, Kazuyuki Kuroda, Chuzo Kato

    Polyhedron   4   653 - 656  1985年01月  [査読有り]

     概要を見る

    Boric acid was trimethylsilylated with Me3SiCl/(Me3Si)2O in the presence of 2-propanol. The resulting mixture was analysed by using a combi. © 1985.

    DOI

  • Synthesis of β‐Sialon from a Montmorillonite‐Polyacrylonitrile Intercalation Compound by Carbothermal Reduction

    Yoshiyuki Sugahara, Kazuyuki Kuroda, Chuzo Kato

    Journal of the American Ceramic Society   67  1984年01月  [査読有り]

     概要を見る

    To develop a new type of carbothermal reduction for the preparation of nitrides, a montmorillonite‐polyacrylonitrile intercalation compound was heated inflowing N2 using intercalated polyacrylonitrile as a reducing agent. Nitridation occurred at &gt;1150°C, and β‐sialon was obtained, with the formation of β‐Sic and AlN. Copyright © 1984, Wiley Blackwell. All rights reserved

    DOI

  • Preparation of alkyl-substituted partial trimethylsilyl silicates from olivine

    Kazuyuki Kuroda, Tetsuhiro Koike, Chuzo Kato

    Journal of the Chemical Society, Dalton Transactions   ( 9 ) 1957 - 1960  1981年  [査読有り]

     概要を見る

    The direct trimethylsilylation reaction of olivine has yielded partial trimethylsilyl derivatives of ortho- and di-silicates whose unsilylated silanol groups have been esterified with the alcohol used as the organic solvent in the trimethylsilylating reagent. Gas chromatographic-mass spectroscopic measurements indicate the presence of the tri-, di-, and mono-alkyl-substituted trimethylsilyl derivatives of monosilicic acid [SiO4(SiMe3)4-nRn
    n = 1-3] in addition to the fully silylated monomeric derivative [SiO4(SiMe3)4]. Dimeric derivatives have also been detected which contain both the completely trimethylsilylated derivative [Si2O7(SiMe3)6] and alcohol-esterified derivatives [Si2O7(SiMe3)6-nRn
    n = 1-4]. The ratio of the esterified products varies with the volume of alcohol or water in the silylating reagent as well as with the reaction time.

    DOI

  • TRIMETHYLSILYL DERIVATIVES OF MONOMERIC AND OLIGOMERIC SILICIC ACIDS EXTRACTED IN TETRAHYDROFURAN

    K KURODA, C KATO

    JOURNAL OF INORGANIC & NUCLEAR CHEMISTRY   42 ( 2 ) 295 - 296  1980年  [査読有り]

    DOI

  • Esterification of partially trimethylsilylated derivatives of hemimorphite

    Kazuyuki Kuroda, Chuzo Kato

    Journal of the Chemical Society, Dalton Transactions     1036 - 1039  1979年12月  [査読有り]

     概要を見る

    Partial trimethylsilyl derivatives have been prepared from hemimorphite, Zn4Si2O7(OH)2·H2O by direct trimethylsilylation and analysed by means of combined gas-liquid partition chromatography-mass spectrometry. Silanol groups of the hemimorphite which are not trimethylsilylated are esterified by the alcohol used as the organic solvent in the trimethylsilylating reagent.

    DOI

  • Trimethylsilylation of hemimorphite

    Kazuyuki Kuroda, Chuzo Kato

    Journal of Inorganic and Nuclear Chemistry   41   947 - 951  1979年01月  [査読有り]

     概要を見る

    Trimethylsilyl derivatives were prepared from hemimorphite by the reaction between the mineral and the trimethylsilylating reagent which was the reaction mixture of hexamethyldisiloxane, chlorotrimethylsilane and an organic solvent (the direct method of trimethylsilylation of silicates). The silylated derivatives were analyzed by gas chromatography and the gas chromatographic patterns varied with the kind of organic solvents used in the trimethylsilylating reagent. The fully silylated derivative of disilicic acid, [(CH3)3Si]6Si2O7, was obtained in a high selectivity when acetone or tetrahydrofuran was used, whereas incompletely trimethylsilylated products occurred in a high yield when an alcohol was used as the silylating reagent. A combined gas chromatography-mass spectrometric analysis of the incompletely silylated derivatives indicated that unsilylated silanol groups were esterified with an alcohol. The trimethylsilylated products obtained from hemimorphite by the Lentz method, whose trimethylsilylating reagent was the reaction mixture of hexamethyldisiloxane, hydrochloric acid, water and an organic solvent, contained incompletely trimethylsilylated derivatives even in the reaction system containing acetone or tetrahydrofuran. These incompletely silylated derivatives were considered to be the silanol-containing partial trimethylsilyl derivatives of disilicic acid on the basis of the GC-MS data. © 1979.

    DOI

  • Synthesis of polyorganosiloxane retaining SiO4 framework from inosilicate mineral by trimethylsilylation

    Kazuyuki Kuroda, Chuzo Kato

    Polymer   19   1300 - 1302  1978年01月  [査読有り]

     概要を見る

    A polyorganosiloxane retaining a SiO4tetrahedral framework has been synthesized by the reaction of an inosilicate mineral (para-wollastonite) with a trimethylsilylating reagent. The glassy product dissolved in a wide range of organic solvents but was insoluble in water. The analyses of the product by means of infra-red spectroscopy, X-ray powder diffraction and elemental analysis indicated that trimethylsilyl side groups were linked to the SiO4framework. The thermal stability of the product was determined by thermal analysis. © 1978.

    DOI

  • Trimethylsilylation of biotite

    Kazuyuki kuroda, Chuzo Kato

    Clays and Clay Minerals   25   407 - 410  1977年01月  [査読有り]

     概要を見る

    Organic solvent soluble organosilicate compounds retaining silicate backbone were obtained by the reaction between biotite and trimethylsilylating reagent. The soluble product which was formed at room temperature or at reflux temperature was a viscous liquid and was soluble in a wide range of organic solvents, but insoluble in water. Molecular weights of the soluble products and their thin-layer chromatograms made it clear that the soluble products consisted of several trimethylsilylated derivatives of silicic acids which were mainly the derivatives of mono- and disilicic acid. The influence of reaction temperature for the trimethylsilylation reaction also was discussed. © 1977.

    DOI

▼全件表示

Misc

  • Formation of ordered silica-organic hybrids by self-assembly of hydrolyzed organoalkoxysilanes with long organic chains

    Kazuyuki Kuroda, Atsushi Shimojima

    Materials Research Society Symposium - Proceedings   707   61 - 72  2002年12月

     概要を見る

    Various layered hybrid films prepared from organoalkoxysilanes with long organic chains, based on the self-assembly of the hydrolyzed species, are reviewed. Morphological control of transparent and oriented films was achieved by cohydrolysis and polycondensation with tetraalkoxysilanes, followed by dip- or spin-coating. In addition to alkytrialkoxysilanes, alkyldimethylmonoalkoxy- and alkylmethyldialkoxy-silanes were also used as the structural units, implying that the inorganic-organic interface can be designed at a molecular level. In these cases, co-condensation in the precursor solution plays an essential role in the formation of homogeneous and ordered films. Alkenyltriethoxysilanes with terminal C=C bonds were also employed to prepare layered hybrid films. Interlayer chains were polymerized upon UV irradiation, and the resulting films exhibited a significant increase in the hardness if compared with the films before polymerization. Hybrid films thus obtained are a new class of materials and of great interest for a wide range of materials chemistry.

  • Formation of ordered silica-organic hybrids by self-assembly of hydrolyzed organoalkoxysilanes with long organic chains

    Kazuyuki Kuroda, Atsushi Shimojima

    Materials Research Society Symposium - Proceedings   703   71 - 82  2002年01月

     概要を見る

    Various layered hybrid films prepared from organoalkoxysilanes with long organic chains, based on the self-assembly of the hydrolyzed species, are reviewed. Morphological control of transparent and oriented films was achieved by cohydrolysis and polycondensation with tetraalkoxysilanes, followed by dip- or spin-coating. In addition to alkyltrialkoxysilanes, alkyldimethylmonoalkoxy- and alkylmethyldialkoxy-silanes were also used as the structural units, implying that the inorganic-organic interface can be designed at a molecular level. In these cases, co-condensation in the precursor solution plays an essential role in the formation of homogeneous and ordered films. Alkenyltriethoxysilanes with terminal C=C bonds were also employed to prepare layered hybrid films. Interlayer chains were polymerized upon UV irradiation, and the resulting films exhibited a significant increase in the hardness if compared with the films before polymerization. Hybrid films thus obtained are a new class of materials and of great interest for a wide range of materials chemistry.

  • Synthesis of NaLnNbC (Ln=La, Nd, Sm, Gd) an their structures and electrical properties

    Wataru Sugimolo, Masahiro Nailo, Yoshiyuki Sugahara, Kazuyuki Kuroda

    Materials Research Society Symposium - Proceedings   547   267 - 272  1999年12月

     概要を見る

    Polycrystalline samples of NaiLnbO (Ln=La, Nd, Sm, Gd) were synthesized by solid-state reactions. Reduced niobates were obtained as single-phase perovskites for x=0.05 and 0.1 when Ln=La and Nd and x=0.05 when Ln=Sm. The Gd-substituted samples could not be prepared under the synthetic conditions studied. Compositional analysis of the products revealed a slight amount of sodium loss during synthesis. The structural parameters obtained from Rietveld analysis revealed an increase in unit-cell volume. All of the obtained samples showed semiconducting behavior. Similar semiconducting behavior was observed for the same x value, suggesting the weak influence of the different Ln species to the electrical properties. © 1999 Materials Research Society.

  • Synthesis of A1-xA′xNbO3 (A = Na+, K+; A′ = La3+, Sr2+) and its electrical properties

    W. Sugimoto, T. Tahara, Y. Sugahara, K. Kuroda

    Materials Research Society Symposium - Proceedings   453   361 - 366  1997年

     概要を見る

    Polycrystalline samples of A1-xA′xNbO3 (A = Na+, K+; A′ = La3+, Sr2+) were prepared by solid-state reactions and the relationship between the structure and electrical properties was examined. Single-phase products were obtained for Na1-xLaxNbO3 (x≤0.1), K1-xLaxNbO3 (x≤0.15), Na1-xSrxNbO3 (x≤0.3), and K1-xSrxNbO3 (x≤0.5). The structures of the sodium-containing compounds and potassium-containing compounds were indexed according to a pseudocubic and cubic symmetry, respectively. The resistivity measurements showed semiconductive behavior for the lanthanum-containing samples. The strontium-containing samples showed semiconducting properties for x≤0.2, while a transition to metallic conduction at low temperature was observed for x&gt;0.2.

  • Pyrolytic preparation of gallium nitride from [Ga(NEt2)3]2 and its ammonolysis compound

    S. Koyama, Y. Sugahara, K. Kuroda

    Materials Research Society Symposium - Proceedings   468   93 - 98  1997年01月

     概要を見る

    Gallium nitride (GaN) was prepared by the pyrolytic conversion of both [Ga(NEt2)3]2 and its ammonolysis product at 600°C for 4 h under Ar. The pyrolyzed residues were analyzed by X-ray powder diffraction and scanning electron microscopy, and the pyrolysis processes of the precursors under He were investigated by thermogravimetry-mass spectrometry. The XRD pattern of the pyrolyzed residue of [Ga(NEt2)3]2 showed well-resolved peaks due to a mixture of cubic and hexagonal close-packed layers of GaN. The broad XRD pattern of the pyrolyzed residue of the ammonolysis product was also attributed to the mixture of cubic and hexagonal close-packed layers of GaN. For the pyrolysis of [Ga(NEt2)3]2, the evolution of hydrocarbons was extensively observed at relatively high temperature, but a large amount of carbon (11 mass%) was still detected in the pyrolyzed residue. On the other hand, the amount of carbon was only 1.1 mass% in the pyrolyzed residue of the ammonolysis product. The pyrolysis results of the ammonolysis product under Ar were very similar to those of [Ga(NEt2)3]2 under NH3.

  • Mesoporous Materials with Uniform Pore Size; Synthesis and Their Applications.

    Yoshiaki Fukushima, Shinji Inagaki, Kazuyuki Kuroda, Kazuyuki Kuroda

    NIPPON KAGAKU KAISHI   1995 ( 5 ) 327 - 333  1995年

     概要を見る

    We have proposed a folding sheet mechanism to form mesoporous crystal from a layered polysilicate, kanemite. This report reviews the structure of layered poly silicates, their intercalation properties, condensation reactions between the polysilicate layers, the mechanism of forming mesoporous materials (FSM) and their applications. SiO4-tetrahedral sheets and interlayer cations form sodium disilicate (Na2Si2O5) and kanemite (NaHSi2O5). An exchange for organic cations gave silicate/organic complexes. When we used kanemite as a host material, we observed a condensation reaction between the unit sheets besides the cation exchange. Removing the organic cations by calcination formed mesoporous materials. Cation exchange at pH = 12 folded the SiO4-tetrahedral sheets without the condensation. Following pH adjustment at 8.5 promoted the condensation between adjacent sheets and gave a silicate/organic complex with hexagonal symmetry. Highly ordered crystals with uniform pores were obtained by calcination at 550°C. We call this mechanism and materials folding sheets mechanism and folded sheets mesoporous materials (FSM), respectively. Complexes with layered structure were also made by using a surfactant with cylindrical shape, or by adding an alcohol. The mesoporous crystals (FSM) are expected to be useful as adsorbents, catalysts or host materials for making nano-cluster of metals or semi-conductors. © 1995, The Chemical Society of Japan. All rights reserved.

    DOI

  • Layered inorganic-organic nanocomposites: Application to photofunctional materials and conversion to inorganic microporous materials

    Kazuyuki Kuroda, Makoto Ogawa, Tsuneo Yanagisawa, Chuzo Kato

    Materials Research Society Symposium Proceedings   286   335 - 346  1993年01月

     概要を見る

    Layered inorganic-organic nanocomposites can be prepared by intercalation of organic compounds into various two dimensional inorganic compounds, such as clay minerals and layered polysilicates. Two different roles of organic guest species are described in the application of intercalation compounds to development of functional materials. The first case shows that organic substances with peculiar photochemical properties can be incorporated in the nanometer-scaled interlayer spaces. Luminescence behavior and photochemical hole burning (PHB) of layered inorganic-organic nanocomposites are investigated from the viewpoint of host-guest interactions. The luminescence maxima of intercalated Ru(bpy)32+ incorporated into fluor-tetrasilicic mica cointercalated with poly(vinylpyrrolidone) shifted gradually toward blue with the decrease in the loading of Ru(bpy)32+. Ru(bpy)32+ was effectively isolated to suppress self quenching due to aggregation even at its high concentration loading. 1,4-Dihydroxyanthraquinone which is known to show a PHB reaction was intercalated into a tetramethylammonium pillared clay mineral and persistent spectral zero-phonon hole was observed at liquid helium temperatures. In spite of the high concentration of 1,4-dihydroxyanthraquinone, a narrow hole was obtained with no distinct decrease in burning efficiency if compared with those doped in ordinary polar polymers or organic glasses. In the second case, intercalation of organic substances into a layered polysilicate induces the change of the layered structure to form a three-dimensional silicate network by condensation of silanol groups in adjacent layers. This phenomenon indicates that novel microporous materials with controlled pore sizes can be prepared through inorganic-organic nanocomposites.

  • Preparation of copper-aluminum double hydroxides by a coprecipitation method

    In Yong Park, Kazuyuki Kuroda, Chuzo Kato

    Waseda Daigaku Rikogaku Kenkyusho Hokoku/Bulletin of Science and Engineering Research Laboratory, Waseda University     1 - 6  1989年12月

     概要を見る

    Copper-aluminum double hydroxides were prepared by coprecipitation from mixed solutions of copper sulfate and aluminum sulfate. The double hydroxides formed when Al3+/(Cu2+ + Al3+) in the initial solution was in the range between 0.25 and 0.35. However, chemical analyses showed that the aluminum contents of the formed double hydroxides were higher than those of the initial solutions. In addition, the basal spacings of the products were similar. These results suggested that the copper-aluminum double hydroxides formed could not be assigned to the hydrotalcite-like compounds. Sulfate anions were present in the interlayer region and no carbonate anions were detected. The anion exchange for chloride anions was confirmed. The aging effect in the preparative stage and the thermal behavior of the double hydroxides were also investigated.

  • SYNTHESIS OF SILICON CARBIDE FROM MONTMORILLONITE-POLYACRYLONITRILE INTERCALATION COMPOUNDS BY CARBOTHERMAL REDUCTION.

    Yoshiyuki Sugahara, Ken ichi Sugimoto, Kazuyuki Kuroda, Chuzo Kato

    Memoirs of the School of Science and Engineering, Waseda University     61 - 75  1987年12月

     概要を見る

    To apply intercalation compounds as precursors for carbide production by carbothermal reduction, n-CH//3(CH//2)//nNH//3** plus -montmorillonite polyacrylonitrile (PAN) intercalation compounds (n equals 5, 11) were converted into SiC. For the comparison, montmorillonite-carbon mixtures were also applied to the conversion. They were heated at 1100-1600 degree C for 1 h in Ar. From the intercalation compound with n equals 5, both alpha - and beta -SiC were detected. beta -SiC formed by the treatments above 1200 degree C, while alpha -SiC was obtained on heating above 1300 degree C. As oxides, only the Mg-Al-O compound crystallized, and no Si-containing oxides formed. The same products were obtained from the intercalation compound with n equals 11. However, it showed the lower reactivity in spite of its larger carbon content. On the other hand, only beta -SiC formed as carbide by heating the montmorillonite-carbon mixtures above 1200 degree C. Silicates of mullite and cordierite were obtained in addition to spinel, the Mg-Al-O compound, and alpha -Al//2O//3. These observations suggest that the presence of PAN in the interlayer space strongly affected the carbothermal reduction process.

  • Si//3N//4 FORMATION IN THE CARBOTHERMAL REDUCTION PROCESS OF A MAGADIITE-POLYACRYLONITRILE INTERCALATION COMPOUND.

    Yoshiyuki Sugahara, Yasuyuki Nomizu, Kazuyuki Kuroda, Chuzo Kato

    Yogyo Kyokai Shi/Journal of the Ceramic Society of Japan   95   124 - 129  1987年01月

     概要を見る

    Silicon nitride was formed from a magadiite (layered polysilicate)-polyacrylonitrile (PAN) intercalation compound through a novel process of carbothermal reduction. SiO//2 from magadiite was reduced above 1400 degree C without the formation of any crystalline oxides. On heating above 1400 degree C, both alpha - and beta -Si//3N//4 were detected, and the additional formation of alpha - and beta -SiC was observed by heating at 1600 degree C. On the other hand, the reactions for the synthesis from a magadiite-carbon mixture involved the formation of cristobalite as well as alpha - and beta -Si//3N//4, and beta -SiC. In addition, it was also indicated that the mixture was less reactive for the formation of Si//3N//4.

    DOI

  • PREPARATION OF A MAGADIITE-POLYACRYLONITRILE INTERCALATION COMPOUND AND ITS CONVERSION TO SILICON CARBIDE.

    Yoshiyuki Sugahara, Ken ichi Sugimoto, Tsuneo Yanagisawa, Yasuyuki Nomizu, Kazuyuki Kuroda, Chuzo Kato

    Yogyo Kyokai Shi/Journal of the Ceramic Society of Japan   95   117 - 123  1987年01月

     概要を見る

    A magadiite (layered polysilicate)-polyacrylonitrile (PAN) intercalation compound was first prepared to investigate its potential as a precursor for the synthesis of non-oxide ceramics by carbothermal reduction. Acrylonitrile monomer was intercalated and polymerized in the interlayer space of a C//1//2H//2//5N(CH//3)//3** plus -magadiite complex. After the cyclization of PAN by the heat treatment in air, the compound was heated in Ar flow for 2 h. Above 1300 degree C, beta -SiC was formed without the formation of any crystalline SiO//2 phases.

    DOI

  • FORMATION OF BORON NITRIDE AND BORON CARBIDE BY PYROLYSIS OF CONDENSATION PRODUCTS OF BORIC ACID AND ETHANOLAMINES.

    Hiroaki Wada, Kazuaki Nojima, Kazuyuki Kuroda, Chuzo Kato

    Yogyo Kyokai Shi/Journal of the Ceramic Society of Japan   95   130 - 134  1987年01月

     概要を見る

    Boron nitride was from boric acid-diethanolamine or -triethanolamine condensation products by their pyrolysis in a nitrogen flow. The condensation products obtained from boric acid-diethanolamine system (molar ratio 1:1 and 2:3) were glassy solids and had a polymeric structure containing the B-O-C bond. Monomeric triethanolamine borate, which contained both B-O-C and coordinate B-N bonds, was formed from boric acid-triethanolamine system. Pyrolysis of these condensation products in N//2 flow at 1400 degree C yielded boron nitride. A small amount of B//4C was also formed, depending on the molar ratio or on the carbon content of the condensation products.

    DOI

  • CARBIDE FORMATION FROM A MONTMORILLONITE-POLYACRYLONITRILE INTERCALATION COMPOUND BY CARBOTHERMAL REDUCTION.

    Yoshiyuki Sugahara, Kenichi Sugimoto, Kazuyuki Kuroda, Chuzo Kato

    Yogyo Kyokai Shi/Journal of the Ceramic Society of Japan   94   38 - 43  1986年01月

     概要を見る

    The montmorillonite-polyacrylonitrile (PAN) intercalation compound was heated in Ar flow for the application of clay-organic complexes to the preparation of carbide through the carbothermal reduction. beta -SiC was formed at 1200 degree C and both alpha -SiC and beta -SiC were detected above 1300 degree C. SiO//2 component was reduced without forming any crystalline compounds, while Al//2O//3 component formed Mg-Al-O compound. Compared with the reactions of a montmorillonite-carbon mixture, it was clarified that the presence of PAN in the interlayer space led to the formation of alpha -SiC and suppressed the crystallization of oxides.

    DOI

  • PREPARATION OF BORON NITRIDE AND BORON CARBIDE BY THERMAL TREATMENT OF BORIC ACID-GLYCERIN CONDENSATION PRODUCT AS A PRECURSOR.

    Hiroaki Wada, Kazuyuki Kuroda, Chuzo Kato

    Yogyo Kyokai Shi/Journal of the Ceramic Society of Japan   94   61 - 65  1986年01月

     概要を見る

    Boron-containing ceramics were synthesized by the heat treatment of the condensation product of boric acid and glycerin in N//2 or Ar. The condensation product was a transparent, glassy solid. It was found that the dehydration was completed and the formation of a compound with the structure (C//3H//5O//3B)n containing B-O-C bonding was revealed. The heat treatment of the condensation product between 900 degree C and 1250 degree C yielded boric oxide and amorphous carbon regardless of gas used. When it was heated in N//2 above 1300 degree C, boron nitride (BN) and boron carbide (B//4C) were detected by XRD and IR analyses. The crystallinity of BN and B//4C increased with the rise of heating temperature. However, heating time affected only the crystallinity of BN. The crystallite size of BN calculated by the Scherrer equation was about 50 A at 1300 degree C and 100 A at 1400 degree C. When the condensation product was heated in Ar above 1300 degree C, the formation of B//4C and graphite was observed.

    DOI

  • EFFECT OF THE PREPARING CONDITIONS OF HYDROUS TITANIUM OXIDES ON THEIR URANIUM ADSORPTION PROPERTIES.

    Hiroaki Wada, Satoshi Matsumiya, Kazuyuki Kuroda, Chuzo Kato

    Waseda Daigaku Rikogaku Kenkyusho Hokoku/Bulletin of Science and Engineering Research Laboratory,     67 - 75  1983年01月

     概要を見る

    Hydrous titanium oxides precipitated from homogeneous solution containing urea and titanium sulfate solution had the highest adsorption capacity. A decrease in uranium uptake was caused by the increase in crystallinity of the sample. When the samples were washed with water at room temperature, uptake increased with increase in the final pH of the solution. For samples washed with hot water, uptake remained constant regardless of final pH. The uptake increased with temperature above 70 degree C.

  • SYNTHESIS AND PROPERTIES OF INORGANIC-ORGANIC COMPLEXES - INTERCALATION COMPOUNDS OF CLAY MINERALS AND TRIMETHYLSILYL DERIVATIVES OF ORTHOSILICATE.

    Chuzo Kato, Kazuyuki Kuroda

    Memoirs of the School of Science and Engineering, Waseda University     145 - 163  1982年01月

     概要を見る

    Two methods for preparing novel inorganic-organic complex materials were investigated; the intercalation of organic molecules into the interlamellar space of clay mineral (montmorillonite), and direct organic derivatization of orthosilicate (olivine). Some Ca-montmorillonite amino acid complex films were prepared and their volume resistivities were measured by means of a high resistance meter. The volume resistivities of these films increased with the increase in the amont of amino acid added. The volume resistivity of every heat-treated complex film was greater than that of its original complex film because of the dehydration of the adsorbed water which was thought to be the charge carrier. In the case of aminocaproic acid-montmorillonite complex, polymerization of aminocaproic acid in the interlayer space as well as the dehydration of adsorbed water by heat treatment were effective for an improvement of the insulation of montmorillonite films.

  • ADSORPTION OF URANYL COMPLEX ION BY VARIOUS ZINC HYDROXIDES.

    Hiroaki Wada, Ichiro Iida, Kazuyuki Kuroda, Chuzo Kato

    Waseda Daigaku Rikogaku Kenkyusho Hokoku/Bulletin of Science and Engineering Research Laboratory,     79 - 85  1982年01月

     概要を見る

    Zinc hydroxides and composite adsorbents containing iron or aluminum were prepared by several methods in order to investigate the effect of preparation conditions on uranium adsorption properties. Adsorption experiments were conducted using artificial sea water to which 0. 72 mol dm** minus **3 sodium chloride was added.

▼全件表示

受賞

  • IMMA Lifetime Achievement Award

    2015年08月   International Mesostructured Materials Association  

    受賞者: 黒田 一幸

  • 第67回日本化学会賞

    2015年01月   日本化学会   メソポーラスシリカ類の創製と展開  

    受賞者: 黒田 一幸

  • 平成25年度錯体化学会貢献賞

    2013年11月   錯体化学会   ナノ空間を有する無機固体化学に関する研究  

    受賞者: 黒田 一幸

  • 平成25年度科学技術分野 文部科学大臣賞表彰

    2013年04月   文部科学省   メソ多孔体合成の先駆的研究  

    受賞者: 黒田 一幸

共同研究・競争的資金等の研究課題

  • 無機ナノ構造体の精密合成とその熱電変換特性

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(A))

  • バイオイメージングへの応用に向けたコロイド状メソポーラスシリカ粒子の外表面被覆

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(挑戦的萌芽研究)

  • ホウ酸有機誘導体からの窒化物,炭化物の合成

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(一般研究(C))

  • 酸化物系層状物質へのインタ-カレ-ションと機能発現

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(一般研究(C))

  • 無機層状化合物の3次元化による新規多孔材料の開発

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(試験研究(B))

  • 多孔質媒体としての有機アンモニウムイオン修飾粘土フィルムを用いた光機能材料の開発

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(一般研究(C))

  • ミクロ空間反応場を利用する分子機能材料の設計と展開

    科学研究費助成事業(北海道大学)  科学研究費助成事業(総合研究(B))

  • 特殊反応場を生かした触媒反応とそのための触媒材料

    科学研究費助成事業(東京工業大学)  科学研究費助成事業(重点領域研究)

  • バイオミメティックセラミックスの先導的研究

    科学研究費助成事業(岡山大学)  科学研究費助成事業(基盤研究(B))

  • ケイ素-酸素結合を持つ巨大シリケートクラスターの探索

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(萌芽的研究)

  • プレセラミック物質を用いた窒化アルミニウム-窒化チタン固溶体の合成

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(C))

  • 層状ペロブスカイト―有機複合体の作製及びその光応答性電気伝導への応用

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(B))

  • バイオミメティックセラミックスの先導的研究

    科学研究費助成事業(岡山大学)  科学研究費助成事業(基盤研究(C))

  • 分子集合体を利用した無機有機メソ構造材料及びメソポーラス材料のケミカルデザイン

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(B))

  • ミクロ・メソ多孔性結晶内における新反応場の構築

    科学研究費助成事業(鳥取大学)  科学研究費助成事業(基盤研究(C))

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    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(B))

  • 層状オクトシリケートの有機修飾による新規ケイ酸塩骨格の構築

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(萌芽研究)

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    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(B))

  • 精密に設計された構造単位からの規則的シリカ系ナノ構造体の創製

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(B))

  • 新規メソ多孔体の物質探索

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(特定領域研究)

  • シロキサン部位を有するブロックコポリマーのミクロ相分離によるシリカナノ細孔の創製

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(萌芽研究)

  • サイズや次元の異なる構造単位を用いたシリカ系物質の高次構造制御

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  • シロキサン系ビルディングユニットからのコロイドの精密合成

    科学研究費助成事業(早稲田大学)  科学研究費助成事業(基盤研究(A))

  • コロイド状メソポーラス有機シリカナノ粒子によるレアメタルイオンの複数同時分離回収

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  • ナノスケール改質によるナノ構造形態制御

    文部科学省 

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    文部科学省 

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    文部科学省 

  • 環境触媒プロセスの開発

    文部科学省 

▼全件表示

特定課題研究

  • 新規熱電変換材料創製に資する無機材料合成技術の開発

    2018年  

     概要を見る

    物質中の規則性ナノ空間と熱電性能との相関を実証することを目指し、ナノ空間のサイズや形状、配列を精密に制御した金属酸化物作製手法の確立を目的とした。優れた熱電特性が期待されているものの、従来手法では作製が困難とされていたN,Nb共ドープTiO2の規則性細孔配列を有するナノ多孔体を作製することに成功した。NbドープTiO2ナノ多孔体を作製後、細孔形状を保持しつつNをドープする多段階的な反応により作製が可能となることを明らかにした。層状LiCoO2ついても多段階合成の有効性も示した。この作製手法の確立は無機材料合成技術の開拓や新規熱電変換材料の創製に貢献しうる非常に重要な成果である。

  • 多孔性金属酸化物の精密合成に基づく物性制御

    2017年  

     概要を見る

    多孔性金属酸化物結晶の構造と骨格密度を制御する手法を確立するとともに、空隙率をシームレスに制御することで、細孔径・細孔形状・細孔配列・空隙率が物性に与える影響を解明することを目的とし、本年度は、ナノ細孔が規則集積した無機ナノ構造体を鋳型に用い、その転写によって作製した多孔性金属酸化物結晶の熱物性を測定した。本研究では、ナノ細孔の形状・サイズ・配列が精密制御されたNドープTiO2を作製した。作製した多孔体試料と無孔質試料の熱伝導率を比較し、熱伝導率は密度から予想される値よりも大幅に低減したことを明らかにした。

  • 水素結合を利用したかご型シロキサンの配列制御による結晶性多孔体合成法の開発

    2017年  

     概要を見る

    ゼオライトなどの結晶性シロキサン構造体は種々応用されており、これらをビルディングブロックアプローチで合理的に構築することが期待されているが、それらの規則的集積法が従来存在しなかった。昨年度までにシラノール基を修飾した二重四員環型シロキサンの分子結晶の作製に成功しており、本年度はクロロシランを用いて結晶のシラノール基をシロキサン結合に変換した。これにより、細孔の構造を保持したままシロキサン結合形成が進行し、分子結晶の結晶構造を反映した結晶性多孔体の作製を達成した。

  • ケイ素アルコキシドのオリゴマー合成に向けた置換基交換反応の開発

    2016年  

     概要を見る

    本研究課題では、アルコキシシロキサンオリゴマーの新規合成手法の開発を目的に、(1) トリメチルシリル(TMS)基のアルコキシシリル基への置換反応の反応条件、(2)ケイ酸塩からのシロキサン骨格の抽出条件、(3) 上記置換反応を用いたアルコキシシロキサンオリゴマーの合成の三つを検討した。(1)では、上記置換反応において、高い変換率(98%)を示す反応条件を見出した。(2)では、直鎖状のシロキサン骨格を有するケイ酸塩のTMS化において、反応条件を検討したが、シロキサン骨格の崩壊の抑制は困難であった。(3)では、TMS基の置換反応を用いてアルコキシシロキサンオリゴマーの合成に成功し、TMS基の変換率は原料のシロキサン骨格の構造により変化した。

  • シリコン基板をシリカ源とするメソポーラスシリカ薄膜の作製

    2015年  

     概要を見る

    Techniques of single nanometer-scalepatterning are required for fabrication of higher-density integrated circuitsand memories. However, single nanometer-scale patterning remains challengingeven today because such an extremely short pitch cannot be fabricated by the conventionalnanopatterning techniques such as photolithography. Expensive mask and photosensitivepolymer are also required for photolithography processes. We have succeeded in fabricating silica-based materials with nanogroove structures at the interfacesbetween Si substrates and lyotropic liquid crystals using soluble silicatespecies generated from Si substrates under basic conditions. Cationicsurfactants were coated on Si substrates. The substrates were exposed to aqueousammonia vapor and they were washed to remove the surfactants. A thin layer on Sisubstrates with an ordered semicircle groove structure, the periodicity anddepth of which are around 5 nm and 2 nm, respectively, was observed.

  • 無機機能材料設計に資するビルディングブロックの精密合成と集積

    2014年   下嶋 敦, 和田 宏明

     概要を見る

    機能と集積がプログラムされたナノ粒子や層状酸化物などの精密集積に関する成果を得た。機能性官能基を表面に有するナノ粒子集積に向けて、コロイド状メソポーラスシリカナノ粒子表面に、異なる官能基を有する2種のナノ粒子を作製し、これらの粒子が交互積層した膜作製に成功した。層状ケイ酸塩上の水酸基を利用し、表面官能基間距離を制御し、2 種類の官能基が交互配列した表面を持つ物質を創製し、新規触媒の作製が可能であることを示した。さらに、合成時におけるシリカコロイド結晶の粒子間隙へのカーボンの充填により結晶化に伴うシリカコロイド結晶の形状変化を抑制することができた。

  • メソ構造を利用したアンカーリング界面の設計と金属薄膜の密着性評価

    2013年  

     概要を見る

    本研究は、薄膜界面のメソ構造の設計およびメソスケールの構造が機械的特性に与える影響の調査を目的として行った。1. メソポーラスシリカ薄膜の作製筒状細孔が2次元的に並んだ2次元メソポーラスシリカ薄膜(2D-MPS)と球状細孔が3次元的に連結した3次元メソポーラスシリカ薄膜(3D-MPS)の2種類の薄膜を作製した。テトラエトキシシラン、界面活性剤、エタノール、水、塩酸を混合した最適なゾル前駆溶液を調製し、次にシリコン基板上へスピンコート法で成膜した。最後に、膜を焼成し界面活性剤を除去した。作製した薄膜をX線回折分析・走査型電子顕微鏡観察(SEM)を用いて構造を評価し、目的とする2次元メソポーラスシリカ薄膜(2D-MPS)と3次元メソポーラスシリカ薄膜(3D-MPS)の作製を確認した。2. メソポーラスシリカ薄膜の表面処理メソポーラスシリカ薄膜表面の大部分に存在する薄いシリカ層を除去するため、温和な化学エッチングを用い、そのエッチング条件を検討した。SEMによる表面の構造分析およびX線光電子分光分析による組成分析により、薄膜表面にオープンなメソ孔を露出させることに成功した(open2D-MPS, open3D-MPS)。3. 表面メソ細孔への銅の導入と銅薄膜の作製真空蒸着によりMPS上に銅薄膜を作製した。メソポーラスシリカ薄膜表面に露出したメソ孔内へ銅を導入するために、蒸着速度を検討した。2次元メソポーラスシリカ薄膜上に作製した銅薄膜の場合(Cu/open2D-MPS)、SEMを用いた剥離させた銅側の表面観察により、2次元メソポーラスシリカ薄膜の表面メソ孔内へ銅が導入されたことを確認した。4. 銅薄膜の密着性評価 2次元メソポーラスシリカ薄膜の場合、銅のメソ孔への入り込みが確認できたので、2次元メソポーラスシリカ薄膜を用いた場合(Cu/open2D-MPS)において、Pull-off テストを用いて、銅薄膜の密着試験を行った。メソ細孔を持たないデンスなシリカ薄膜上に作製した銅薄膜の場合と比較したところ、2次元メソポーラスシリカ薄膜を用いた場合(Cu/open2D-MPS)、密着性が向上した。以上から、メソスケールのアンカーリング界面が密着性に影響を及ぼすことが示唆された。

  • 無機ナノシート構造を活用した無機ナノ材料の設計

    2006年  

     概要を見る

    無機層状物質(層状ポリケイ酸塩、カオリナイトなど)、ナノシート(層状ニオブ酸塩K4Nb6O17)を用いた無機有機ナノ誘導体、ナノ構造体を合成し、その組成・構造制御による機能発現に向けた基礎的知見を得ることを目的とし研究した。無機有機層状複合体は二次元的に制限された場を生かした吸着剤、反応場への応用可能性を有している。層状ケイ酸塩カネマイト (NaHSi2O5・3H2O)の層間環境の親・疎水性を制御することを目的とし、カネマイト層間へ両親媒性分子である非イオン界面活性剤ポリオキシエチレンアルキルエーテルのインターカレーションを試みた。直接反応ではインターカレートしなかったが、ヘキサデシルトリメチルアンモニウムイオンをインターカレートさせた層間化合物を中間体としてカネマイト―ポリオキシエチレンアルキルエーテル層間化合物の合成に成功した。また、層状粘土鉱物カオリナイトをホスホン酸で修飾することにより層間環境を親水化し、水のインターカレーション、デインターカレーションによる層間距離の変化やヘキサデシルトリメチルアンモニウムイオンのインターカレーションを実現した。無機ナノシートが巻くことで得られるナノチューブは、その壁にシートの重なりによる層状構造を有している。このような層状物質は、従来の平板状の結晶形態を有する層状物質とは異なる性質が期待される。K4Nb6O17系ナノシートから得られるナノチューブ層間へのトリスビピリジンルテニウム錯体及びメチルビオロゲンのインターカレーションを様々な濃度、温度で行った結果、トリスビピリジンルテニウム錯体及びメチルビオロゲンの濃度によって層間への導入量の制御が可能であった。また、ナノチューブは元のK4Nb6O17層状物質に比べ高いインターカレーション能を示し、低温、短時間で反応が進行した。

  • 層状ポリケイ酸塩構造を基盤とした段階的アプローチによるナノ細孔シリカの創製

    2005年  

     概要を見る

    層状ケイ酸塩オクトシリケートの層間に有機アンモニウムイオンをインターカレートし、それを中間体としてジアルコキシジクロロシラン類で層間のSiOH基を修飾することに成功した。29Si固体NMR、元素分析、熱分析などの手段を活用し、層間でのシリル基の配列について調べ、層状オクトシリケートが有する層表面結晶構造に由来する規則的な修飾を明らかにした。この方法により、新たな二次元系層状ケイ酸塩の設計が可能であることを初めて明らかにしたものである。また、修飾体のアルコキシド基の加水分解と形成するシラノール基の縮合反応を利用して、層間架橋による三次元化と新たな細孔形成の可能性を明らかにできた。さらに、層間を連結可能なシリル化剤を反応させることで、親水・疎水性能を制御可能なことも新たに明らかにした。この方法は種々の層状ケイ酸塩に適用可能であり、マガディアイト、ケニアアイトなどへも展開できる。

  • Ti系及びNb系層状酸素酸塩層間での光増感色素組織化による新規ナノ複合材料の構築

    2000年   菅原 義之, 小川 誠

     概要を見る

     Ti、Nb系層状結晶は厚さ約1 nmの半導体層が積層した規則構造を有し、インターカレーション能を有する。本研究ではTi, Nb系層状結晶-光増感色素複合体の合成、構造、および可視光誘起電子移動について検討した。可視光誘起電子移動反応は、光エネルギー変換という観点から注目され、多くの検討が行われているが、本研究は高い秩序性・規則構造を有する系を用いた点で新規なアプローチと言える。 まず、酸処理してプロトン型とした層状チタン酸塩(CsXTi2-X/4□X/4O4, Na2Ti3O7)にヘキシルまたはプロピルアンモニウムイオンをインターカレートし、光増感色素であるシアニン色素の溶液と反応させることにより色素のインターカレーションを試みた。XRD、吸収・蛍光スペクトル測定から、色素会合体と層状半導体が交互に積層したナノ複合体の合成を確認した。蛍光測定では、励起色素から半導体層への電子移動によると予想される消光を観察した。ESRスペクトルでは、可視光照射に応答して色素のラジカルジカチオンに帰属されるシグナルが現れた。さらに可視光照射に応答する伝導度も増加した。層が絶縁体であるモンモリロナイトを用いた場合、これらの現象は観察されなかったことから、色素会合体と半導体ホストが関与した可視光誘起による電子移動反応が起きたものと考えられる。またESRシグナルの減衰曲線から、用いるホストやシアニン色素の種類によって逆反応の速度を制御できることも見いだした。同様の方法でフタロシアニンの導入にも成功し、現在、より詳しい検討を進めている。 また合成法の改良により、複合体を「2次元異方性を持つ透明薄膜」として得ることに成功している。さらに単結晶の層状ニオブ酸塩をホストとして用いた場合、色素の配列を3次元的に制御できることも明らかにしつつある。このように、より高い秩序性、異方性を有する系では、従来用いられてきた粉末系では得られなかった知見の集積が可能になる点で、その意義は極めて高い。

  • International Symposium on Zeolites and Microporous Crystals

    1997年   菊地 英一, 山崎 淳司, 菅原 義之, Mark E. Davis

     概要を見る

    最近のミクロ孔結晶の基礎及び応用面の展開はめざましいものがある。さらに研究代表者らが世界で初めて報告したメソポーラスシリカの研究も最近急激に展開している。これらの物質は、従来の分離、吸着、触媒関連の展開にとどまらず、環境保全のキーマテリアルの一つとしても注目を集めている。このため、近年ゼオライトおよびミクロ孔質結晶に関する国際会議は増加しつつある。その中で、日本のゼオライト研究会(現ゼオライト学会)は、1989、1993の過去2回のシンポジウムを開催し、世界にその研究交流の場を提供し、多くの情報発信を行ってきた。本研究会において、1997年のシンポジウムを早稲田大学において開催することが決定され、本特定課題助成費のメンバーを早稲田大学での中心チームとして活動を進める拠点を設定した。 本研究の目的は、上記背景をふまえて、表記国際シンポジウムの開催に向けて、Researchtopicsの選定、招待講演者・依頼講演者の選定、国内国外研究者への連絡や各種討議を行うことであった。本シンポジウムの内容として、鉱物学、結晶化学、合成、キャラクタリゼーション、イオン交換、吸着と拡散、ホストゲスト相互作用、触媒、応用の等非常に広範囲の検討がなされた。代表者及び分担者の多くは、96年8月のソウルにおけるゼオライト国際会議にも出席し、本シンポジウムの成功に向けての各種活動を行った。Davis教授とは、電子メールでのやりとりを中心に内容の打ち合わせ等を行った。 これらの研究成果に基づき、97年8月、国際会議場にて、ZMPC97を成功裏に開催することができた。会議録は、Elsevier社からMicroporous Mesoporous Materialsの特別号として98年7月出版され、全ての活動を終了した。

  • 無機層状物質の層間・界面の設計

    1997年   菅原 義之, 小川 誠

     概要を見る

    無機層状物質の層間・表面は機能発現の特異な場を提供している。層間における有機分子の配向制御による光機能発現や、層間の官能基の固定による分離機能の発現などが期待される。従来、層間化合物形成能を生かしたナノ複合体形成の研究は数多くあるが、本研究では、更なる展開の一つとして、層間あるいは層表面における、より高度な構造制御の可能性を探り、機能制御の高度化の手法を見出すことを目的とした。本研究では、無機層状物質の中でも特に層状ケイ酸塩に着目し、その層間化合物形成能を生かした設計を行った。 層間に界面活性剤イオンを導入することにより疎水化し、その有機化した層間にアゾベンゼンを導入し、層間で光異性化することを初めて明らかにした。またクラウンエーテルの取り込みも可能であることを示した。この結果をさらに発展させ、クラウンエーテルが特定のイオンと安定な錯体を形成する性質を利用して、クラウンエーテル共存下での層間イオン交換反応が進行するという新しい層間化合物合成法が本研究より生まれた。 また本研究の成果として、カオリナイトーメタノール層間化合物の合成とこれを中間体としたゲスト交換法による種々のカオリナイトー有機層間化合物の合成に成功した。従来不可能とされてきた種々の有機ゲスト分子の取り込みが可能となり、層間の修飾技術の高度化を図ることができた。 さらに層状ケイ酸塩マガディアイトを用い、その層間表面をシリル化処理した。アルキルジメチルクロロシラン及びアルキルトリクロロシランによるシリル化を行った結果、層間の親水・親有機的性質の制御が用いるシリル化剤の種類と量によって制御可能であることを明らかにした。この性質を生かし、アルコール及び炭化水素の吸着実験を行った結果、アルコールの選択的な取り込みを明らかにすることができた。これは層間の親水・親有機的環境の制御の結果であると考えられる。

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