© 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.

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.

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.

© 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.

© 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.

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.

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.

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.

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.

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.

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.

© 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.

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.

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.

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.

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.

© 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.

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.

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.

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.

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.

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.

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.

© 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.

© 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.

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.

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.
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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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)).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

(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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 & Co. KGaA.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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 ° 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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

The luminescence characteristics of tris(2.2'-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.

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 <----> 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].

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.

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.

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.

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.

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.

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.

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.

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.

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)).

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Intercalation of 4,4'-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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

孔径が2nm以上の均一メソ孔を有するメソポーラスマテリアルが,規則的な孔配列や特異な空間の提供等から応用面を含め関心を集めている.新規メソポーラスマテリアル合成には分子集合体が重要な役割を果たしている.組成・構造の多様化,孔径・形態の制御,応用展開等,最近急激に研究が進展しているメソポーラスマテリアルの合成について紹介する.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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%).

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%.

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.

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.

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.

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.

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.

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.

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(>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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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 & Francis Group, LLC. All rights reserved.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.