The present study explores the oxygen storage capacity of YBaCo4O7+δ prepared by a glycine-complex decomposition method. We reported for the first time that the YBaCo4O7+δ sample was successfully synthesized at such a low temperature of 800 °C by this method. The YBCO-800 N sample exhibited a faster oxygen absorption/desorption speed than that of high calcination temperature samples, and the time required for complete oxygen storage/release was 5 and 6 min at 360 °C, respectively. Moreover, the superior performance observed for this product in the temperature swing adsorption process makes it a promising candidate in oxygen production technologies. This research demonstrated that the glycine-complex decomposition method is an effective method for improving the oxygen storage property of YBaCo4O7+δ and provides a new insight into designing other novel oxygen storage materials.

In this work, two-dimensional crystalline C3N4 (CCN) was obtained by promoting the self-condensation reaction of dicyandiamide in an air atmosphere via the molten salt method. Studies show that compared with polymer-C3N4 (PCN) ((9.8 m2/g)), CCN has a larger specific surface area (77.1 m2/g)) and better crystallinity. Additionally, the resistance of CCN in the air is 40 MΩ, 1250 times lower than that of polymer-C3N4 (PCN) (∼50000 MΩ). Secondly, when 50 ppm toluene gas analysis flows into the CCN based gas sensor at room temperature, the gas response value is 350. The CCN based gas sensor works for 60 days, or after 25 cycles continuously, the gas response value remains at about 350 (Rg/Ra), which is due to the excellent crystallinity, optimized π conjugate system, and enhanced interlayer van der Waals of CCN. Additionally, the critical effect of crystallinity on the gas sensitivity of carbon nitride is also discussed in detail.

Molybdenum sulfide selenide (MoS2-xSex) solid solution nanoparticles were investigated to modify the crystal structure of molybdenum disulfide (MoS2) for improving the nitric oxide (NO) detection performance at room temperature. The hydrothermal reaction followed by post-annealing treatments was used to engineer the structural, morphological, and electronic properties of MoS2-xSexnanoparticles. MoS2-xSexsamples with different selenium addition ratios (x= 0, 0.2, 1, 1.8, and 2) were prepared to understand the optimum condition for NO detection. The gradual addition of the selenium atom expanded the interlayer distance and increased the lattice parametera=bfrom 3.148(0.1) Å forx= 0 to 3.279(0.08) Å forx= 2. The chemical bonding of Mo-S expands, while Mo-Se bonding compresses in MoS2-xSexsolid solution. The particle size also decreased after selenium addition from 500 nm forx= 0 to 80 nm forx= 2. The band gap also gradually decreased after selenium addition from 1.66 to 1.44 eV, which is related to an increase in the conductivity. The NO detection performance of MoS2-xSexwithx= 1 showed the highest NO detection performance with a response value of around 48% due to its small particle size, high adsorption energy, high charge transferability, and good stability. MoS2-xSexwithx= 1 detection performance was relatively stable under different humidity conditions and also was very sensitive to the NO gas molecule compared to volatile organic compound gases as well as hydrogen gas. This indicates that thex= 1 nanoparticle is very promising to be applied as a NO detection device at room temperature.

Lanthanide-substituted YMnO3+δ nanoparticles with the hexagonal phase, denoted as R0.25Y0.75MnO3+δ (R = Er, Dy, Tb, Gd, and Sm), have been successfully synthesized by the polymerized complex method. The substitutions did not largely affect the morphologies and specific surface area of the obtained R0.25Y0.75MnO3+δ nanoparticles. From the evaluation for the oxygen storage/release properties, the oxygen storage capacity (OSC) increased significantly by the Tb substitution, and the oxygen absorption/release rate strongly depended on the ion size of the substituted lanthanides. It was found that Tb4+ existed in Tb0.25Y0.75MnO3+δ after oxygen absorption, demonstrating that the remarkable increase in the OSC of the Tb-substituted sample was due to the oxidation of not only Mn3+ to Mn4+ but also Tb3+ to Tb4+. In addition, the unit cell volume increasing with the R ion size, which can lead to the promotion of the oxygen diffusion in the crystal structure, was the factor leading to the increase of the oxygen absorption rate. Especially, Sm0.25Y0.75MnO3+δ showed an excellent OSC of 3 + δ= 3.34 (the weight increase rate was 2.64 wt %) even under a rapid temperature swing rate of 20 °C/min.

A unique structural transformation of a lepidocrocite-type layered titanate, K0.8Ti1.73Li0.27O4, into a rutile-type TiO2 has recently been realized via dilute HCl treatment and subsequent drying at room temperature for producing rutile-nanoparticle-decorated protonated layered titanate exhibiting highly efficient photocatalytic activity. Herein, the authors report synthesis of a lepidocrocite-type layered cesium titanate with nominal compositions of <inline-formula>
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This study proposed a new layer modification technique, “layer charge control”, for layered perovskites, and the structures of the obtained charge neutral [CeTa₂O₇] perovskite sheet were characterized theoretically and experimentally.

© 2020 The Ceramic Society of Japan. All rights reserved. Attention has recently been paid to oxyfluorides, one of the mixed anion materials, because they possess unique properties for many kinds of application fields. Because the general synthesis processes for oxyfluorides are based on troublesome methods, novel safe and facile processes are required. In this study, MoO3 was solvothermally reacted with KF, RbF, and CsF at 200 °C to form potassium, rubidium, and cesium molybdenum oxyfluorides. The reaction of MoO3 with KF and RbF led to the formation of K3MoO3F3 and Rb3MoO3F3 with a known structure, respectively, while the reaction of MoO3 with CsF induced an unknown phase which should be Cs3MoO3F3 with the similar structure to those of K3MoO3F3 and Rb3MoO3F3. A3MoO3F3 (A = K, Rb, and Cs) has not been synthesized under liquid phase until now, and this research clarified this kind of the solvothermal reaction can lead to the formation of unique oxyfluorides at low temperature. In addition, Cs3MoO3F3 was converted into Cs3Mo2O6F3 by treatment with methanol, suggesting the instability of Cs3MoO3F3. This kind of conversion reaction from one oxyfluoride to the other oxyfluoride has not been reported, and the development of such chemical conversion may lead to the formation of new oxyfluorides.

NaMoO3F and Na5W3O9F5 were synthesized by solvothermal reaction of MoO3 and WO3, respectively, with NaF in nonaqueous solvents. These reactions were realized at low temperatures (150-200 °C) without the use of HF. This synthesis method is much more facile and safe procedure compared with general synthesis methods for oxyfluorides which includes hydrothermal reaction under a presence of HF or solid-state reaction at high temperatures in vacuum sealed tube or under high pressure. In the case of the reaction of MoO3 with NaF, the kind of solvent largely affected the obtained morphologies of NaMoO3F. The morphology in the case of acetonitrile as a solvent was rodlike with a micrometer-scale size, while that in the case of ethanol was polyhedral with a size of several hundred nanometers. In addition, the solvothermal reaction of WO3 with NaF led to the formation of Na5W3O9F5. Also, the difference of solvents for the solvothermal reaction affected the obtained particle sizes. The effect of the solvents on the morphologies of the obtained oxyfluorides probably resulted from the difference of the solubility of NaF and the subsequent dissolution ratio of MoO3 or WO3 in the used solvents. Our synthesis method can expand the applicability of oxyfluorides by providing a new phase and/or unique morphology.

<p>NiO with polar (111) facets was successfully synthesized from the transformation of a layered NiOHCl, exhibiting excellent NO_x detection and degradation activity.</p>

Toluene is one of the harmful volatile organic compounds (VOCs) for both human health and environments. Thus, to prevent the hazardous effect of toluene, fast detection at an early stage is needed. CuO shows the merit for a wide range responsivity to VOCs but suffers from small response value, slow response/recovery speeds, and low durability. Herein, we report a facile preparation of CuO/Ti3C2Tx MXene hybrids via electrostatic self-assembly. The CuO nanoparticles (∼7 nm) were uniformly dispersed on the surface and the interlayers of the Ti3C2Tx MXene, forming hybrid heterostructures. The CuO/Ti3C2Tx MXene exhibited the improved toluene gas sensing response (Rg/Ra) of 11.4, which is nearly 5 times higher than that of the pristine CuO nanoparticles (2.3) to 50 ppm of toluene at 250 °C. Due to the different work function (φ), the Schottky junction was established at the interface of CuO/Ti3C2Tx MXene, acting as a hole trapping region (HTR) at the Ti3C2Tx MXene side. Compared to other hybrid 2D materials such as MoS2 and rGO, which possess a higher work function, the CuO/Ti3C2Tx MXene maintained better toluene sensing performance. Thus, the work function is critical for designing a high sensing performance of hybrid metal oxides/2D materials. The hybridization of CuO with Ti3C2Tx MXene improved not only enhancement of the response time but also the selectivity and the responses (270 s) and recovery times (10 s) compared with those of CuO, due to high conductivity of the metallic phase in Ti3C2Tx MXene. Such excellent performance showed the promising applications of metal oxides/2D hybrid materials for VOCs gas sensing.

IF=3.25

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Oxynitrides with narrow band gap are promising materials as visible-light sensitive photocatalysts, because introduction of nitrogen ions can negatively shift the position of valence band maximum of the corresponding oxides to negative side. (Zn1+xGe)(N2Ox) with wurtzite structure is one of the oxynitride materials. (Zn1+xGe)(N2Ox) with nanotube morphology was synthesized by nitridation of Zn2GeO4 nanorods at 800 degrees C for 6 h. During the nitridation process, the nanorod with smooth surface was transformed into nanotube with rough surface in spite of no template for formation of tube structure. The nanotube formation can be caused by ordered morphological transformation from Zn2GeO4 nanorod during the nitridation. (Zn1+xGe)(N2Ox) nanotube exhibited a large specific surface area due to its nanotube morphology and the ability to be responsive to visible light because of the narrow band gap of 2.76 eV. Compared to (Zn1+xGe)(N2Ox) synthesized by conventional solid state reaction, the optimized (Zn1+xGe)(N2Ox) nanotube possessed enhanced photocatalytic NO, decomposition activity under both ultraviolet and visible light irradiation.

Microspherical particles of Rh-doped SrTiO3 (SrTiO3:Rh) having size of 1-2 mu m were synthesized by a spray drying (SD) method employing a water-soluble ammonium trilactatotitanate. When the calcination temperature increased up to 1200 degrees C, primary particles grew significantly while the microspherical morphology of the secondary particles was kept. Dynamic light scattering analysis proved well-dispersive nature of the SD sample. Photocatalytic activities of SrTiO3:Rh synthesized by the SD method, solid state reaction (SSR), and a poly-merizable complex (PC) method were evaluated for H-2 evolution using an electron donor such as methanol, Fe2+, or [Co(bPY)(3)](2+) and Z-scheme water splitting combined with BiVO4 of an O-2-evolving photocatalyst and either Fe3+/2+, [Co(bpy)(3)](3+/2+), or reduced graphene oxide as an electron mediator. SrTiO3:Rh prepared by the SD method showed much higher activities for all Z-scheme water splitting than the samples synthesized by the SSR method. Activities of the SD sample for Z-scheme water splitting using electron shuttles, Fe3+/2+ and [Co(bpy)(3)](3+/2+), were slightly higher or comparable to those of the PC sample whereas the SD sample achieved higher activity in Z-scheme water splitting based on interparticle electron transfer. In addition, even when the mass of SrTiO3:Rh used for the Z-scheme system with Fe3+/2+ was decreased from 50 mg to 30 mg, the SD sample still showed high activity while the activity decreased for the SSR and PC samples. Thus, usefulness of the SD method to obtain highly active SrTiO3:Rh with well-dispersive nature has been demonstrated.

A facile solvothermal synthesis in an ethanol/acetic acid mixture for the fabrication of SnO2 with a controllable hierarchical spherical size and micro-/mesoporosity is presented. SEM, TEM and N2 adsorption/desorption investigation unveiled that the obtained SnO2 spheres exhibited a particle size in the range of 0.6–1.6 μm and a pore size of about 1.4–1.9 nm depending on the volume ratio of acetic acid to ethanol in the reaction mixture, and the spheres were constructed by nanoscale particles. Due to its micro-/mesoporous structure, the SnO2 spheres exhibited large specific surface areas over 100 m2/g. When 10 vol. % of acetic acid at 200 °C for 20 h was used for the reaction, the obtained SnO2 possessed a higher specific surface area of 145 m2/g (SnO2_10). The gas sensing property of SnO2_10 without an additional noble metal co-catalyst exhibited a large toluene sensing response (Ra/Rg) of 20.2 at 400 °C, which was about 6 times higher and acceptable selectivity compared to those of other samples. The study found that the sensing performance in the SnO2 hierarchical spheres was influenced by several factors e.g. particle morphology, pore size and specific surface area rather than only a single parameter. Therefore, a precise control of those influencing parameters may lead to the optimum sensing property. These findings are important for the further development of the micro-/mesoporous metal-based oxide as an alternative successor for toluene gas sensor material.

GaN:ZnO solid solution nanoparticles and films were synthesized by using ZnGa2O4 nanoparticles with a particle size of below 25 nm obtained hydrothermally as a precursor. Nitridation of powder ZnGa2O4 nanoparticles led to the formation of GaN:ZnO nanoparticles. The nitrided samples have higher specific surface area than those obtained by conventional method, which induces higher photocatalytic NOx decomposition activity. In addition, a transparent coating film with ZnGa2O4 nanoparticles was converted to GaN:ZnO film after nitridation. The nitrided film absorbs UV and blue light and is transparent for light of wavelength over 500 nm (the transmittance is over 90 %). This means that the nitridation does not lead to the formation of scattering domains by the large-size particles and cracks. This method for film preparation is much cheaper than conventional CVD and sputtering processes. These results strongly suggest the utility of ZnGa2O4 nanoparticles not only for the formation of GaN:ZnO solid solution nanoparticles with high specific surface area but also for the preparation of transparent GaN:ZnO solid solution films.

Extremely stable gas sensors at elevated temperature (T > 400 °C) with rapid detection of hydrogen gas are urgently demanded especially for hydrogen production industry which typically involves a high-temperature system. Gallium nitride (GaN) possesses excellent physicochemical properties and is expected to be one candidate for high temperature gas sensor. In this work, the GaN preparation from α–GaOOH precursors by a direct nitridation method under NH3 flow is presented. The nitridation was done at various temperatures to obtain GaN with different oxygen contents, which played a vital role in gas sensing response of thick film GaN in various concentration of H2 gas at 500 °C. The sensitivity of the obtained GaN with 2.07 wt.% of oxygen content was 10 times higher than that sample with the lowest oxygen content (1.9 wt.%) and the sensitivity drastically decreased when the oxygen content was 2.53 wt.%. The sensors also demonstrated high stability as indicated by their repeatable feature after being exposed at a various concentration of H2 (150–750 ppm). Furthermore, the GaN showed higher sensitivity than that of β–Ga2O3 sensor.

Composite type photocatalyst F-TiO2/(N,C)-TiO2 consisted of anatase-type TiO2 with fluorine-doping (F-TiO2) and TiO2 with nitrogen and carbon-doping ((N,C)-TiO2) was prepared by simple physical mixing to exhibit higher visible-light responsive photocatalytic nitrogen oxide (NO) decomposition activity than those of F-TiO2 and (N,C)-TiO2. Transient absorption measurement clarified that the composite possessed longer carrier lifetime compared to that of each material (F-TiO2 or (N,C)-TiO2), resulting in higher photocatalytic activity. In the composite, photoexcited holes and electrons, which are not in impurity level but in valence and conduction band, respectively, should photocatalytically decompose NO, judging from the redox potential of O-2/O-2(center dot-) and the band positions of F-TiO2 and (N,C)-TiO2. The mechanism for higher visible-light photocatalytic activity, or longer carrier lifetime can be explained by charge transfer between F-TiO2 and (N,C)-TiO2 through their impurity levels. The charge transfer should make photoexcited carries spatially separated to enhance the photo catalytic activity.

Various types of coating films were obtained from hydrothermally synthesized Nb-doped TiO2 (NTO) and CsxWO3 (CWO) nanoparticles. The coating films possessed multifunctionality including near infrared (NIR) absorption and photocatalysis abilities. The NTO and CWO nanoparticles were synthesized by a unique solvothermal reaction in which water induced by an esterification reaction between alcohol and carboxylic acid can act as a hydrolyzing agent for metal precursors. NTO was synthesized by the unique solvothermal reaction for the first time. The reaction accompanied by the reduction of Ti4+ to Ti3+ led to the formation of nanoparticles with both NIR absorption and photocatalytic properties. The effect of the ethanol-acetic acid ratio on the morphology of the obtained NTO was investigated, and the larger amount of acetic acid led to a larger nanoparticle size, indicating the size controllability. The two types of coating film, including CWO and NTO nanoparticles, were obtained for comparison: (1) coexistent coating film: one side of the quartz glass was coated with a dispersion, including both CWO and NTO nanoparticles, and (2) double-sided coating film: a quartz glass coated with a CWO dispersion on one side and an NTO dispersion on the other side. The double-sided coating led to higher multifunctionality. Furthermore, the optimized condition for the double-sided coating was investigated by using various NTO particles obtained using different ethanol-acetic acid ratios.

The synthesis of silver nanoparticles (AgNPs) within the interlayer space of transparent layered titania nanosheet (TNS) films is investigated. A considerable number of silver ions (approximate to 70% against the cation exchange capacity of the TNS) are intercalated in the TNS films using methyl-viologen-containing TNSs as a precursor. The silver ion (Ag+)-containing TNS films are treated with aqueous sodium tetrahydroborate (NaBH4), resulting in a gradual color change to bright blue. Various structural analyses clearly show that crystalline AgNPs are generated within the interlayer space of the TNSs. The NaBH4-treated films show intense and characteristic near-infrared (NIR) extinction spectra up to 1800 nm. The tability of the AgNPs within the TNS against oxygen and moisture is also investigated, and 96% and 82% of the AgNPs remain after standing in air for 1 month and 1 year, respectively. The NIR extinctions of the AgNP-containing TNS films are further extended by employing different preparation procedures, for example, using sintered TNS films as starting materials and irradiating the Ag+-containing TNSs with ultraviolet (UV) light. The obtained AgNP-containing TNS films exhibit photochemical activities in the production of hydrogen from ammonia borane under visible-light irradiation and the decomposition of nitrogen monoxide under UV-light irradiation.

SrTiO3 is an excellent photocatalyst due to its high photocorrosion resistance and thermal stability. In this study, we synthesized SrTiO3 nanoparticles with high specific surface areas by the hydrothermal method at reduced temperature. Titanium(IV) bis(ammonium lactato)dihydroxide (TALH) solution and strontium hydroxide octahydrate [Sr(OH)2·8H2O] were used as starting materials. SrTiO3 nanoparticles were directly synthesized by hydrothermal heating at 150°C for 72120 h. The synthesized nanoparticles had diameters of 2040 nm, and the SrTiO3 powder heated for 72 h exhibited the highest specific surface area of 33.1 m2/g. This sample also showed the highest degradation rate for NO gas.

Gallium oxynitride (GaON) nanoparticles were synthesized through three steps
(i) hydrothermal treatment of an aqueous solution containing Ga(NO3)3, hexamethylenetetramine (HMT), and acetylene black, (ii) calcination, and (iii) nitridation. The presence of acetylene black in the hydrothermal treatment is effective for the synthesis of Ga2O3 nanoparticles after the calcination. The intermediate obtained after the hydrothermal reaction possessed no detectable Ga particles in the TEM observation, although the presence of Ga was confirmed in the EDS measurement. This means that acetylene black (AB), in this study, cannot play a simple role as a template. The GaON nanoparticles obtained from the Ga2O3 nanoparticles through nitridation possessed a higher oxygen content than that from Ga2O3 obtained by hydrothermal synthesis without acetylene black and the subsequent calcination. The obtained GaON nanoparticles show higher photocatalytic NOx decomposition activity than bulk GaON synthesized under the same conditions except without acetylene black in the hydrothermal reaction, because of the longer absorption edge and the higher specific surface area. In addition, the effect of nitridation temperature and time on the obtained GaON nanoparticles and their photocatalytic activity was also investigated. Consequently, nanoparticle morphology of a precursor for GaON is important not only for high surface area but also for high visible-light response.

Synthesis and characterization of functional nanoparticles and their applications for smart window are reviewed. Various kinds of nanomaterials and their composites are successfully synthesized by solvothermal process. Thin films on glass substrate can be fabricated by doctor blade method using nanoparticles as starting materials. The mixed valence state tungsten-based homogeneous nanomaterials possess excellent infrared (IR) light shielding properties, implying their potential applications for the heat ray shielding and indoor energy saving effect in summer. On the other hand, VO2 monoclinic-based nanoparticles possess smart and excellent thermochromic properties, show excellent heat ray shielding effect in summer and heating effect of winter indoors. Also, multifunctionality of thin films can be realized by fabricating the composites with various functional components, implying their potential applications for IR shielding, photocatalysis and self-cleaning at the same time. The design of composites and structure of thin films might result in the enhancement or properties of practice applications on window materials.

© 2018 The Royal Society of Chemistry. Particulate Ta 3 N 5 , a material that responds to visible light for photoelectrochemical O 2 evolution, was glued to a metallic GaN conducting layer. The electrode was able to oxidize water with 1.8-fold higher efficiency than that without GaN. The GaN layer blocked the hole current from Ta 3 N 5 to the back-contact metal layer and prevented hole-electron recombination.

Direct nitridation process has been performed to synthesize morphology controllable aluminum nitrides (AlN). Three different morphologies of gamma-AlOOH were treated under NH3 flow at 1400 degrees C for 4 h. Hydrazine (N2H4) was employed in this study as a nitriding agent to promote nitridation reaction. In the presence of hydrazine, a high purity of aluminum nitride (AlN) could be achieved with less than 5 wt.% of oxygen impurities. Interestingly, after being exposed to elevated temperatures, the initial morphology was still retained. Whereas the TEM measurement indicated surface roughening due to the release of H2O. The investigation of sintering behavior of the prepared AlN powders revealed that plate-like morphology had the lowest shrinkage completing temperature (1574 degrees C).

We investigated a new one-pot synthesis method for β-TaON oxynitride using (C6N9H3)n (melon) as a solid nitrogen source. β-TaON single phase was obtained from Ta2O5 using melon heating under a separated and sealed condition in a quartz glass tube. The oxygen and nitrogen contents of prepared β-TaON were almost 100% of the theoretical values.

Environmentally friendly soft chemical processes, including solvothermal/hydrothermal process and mechanochemical process, for the synthesis of mixed anion type visible-light induced photocatalysts are introduced in this review paper. Titania and strontium titanate based anion doped photocatalysts can be effectively prepared at such low-temperature as below 200 degrees C. Especially, the mechanochemical process is a useful method for the synthesis of various mixed ions doping functional materials at low temperatures. The mixed anion type photocatalytic compounds consisted of N/O, N/F/O, S/O, N/C/O, show excellent visible light absorption ability and photocatalytic activities, indicating the potential applications in environmental purifications. Full-spectra active long wavelength light induced photocatalyst, full-time active photocatalyst system and infrared radiation (IR) shielding multifunctional photocatalysts will be introduced also.

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 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.

An improved variation of highly active/durable O-2-evolving LaTiO2N powder-based photoelectrode has been fabricated by pre-cleaning the powder with mild polysulfonic acid and by homogeneous deposition of CoOx co-catalyst aided by microwave annealing. The treatment in aqueous solution of poly(4-styrene sulfonic acid) results in removal of surface LaTiO2N layers, forming fine pores in the crystallites. The CoOx co-catalyst by microwave deposition in Co(NH3)(6)Cl-3/ethylene glycol homogeneously covers the particle surface. The LaTiO2N powder is fabricated into particle-transferred electrodes on Ti thin film supported on solid substrate. The modified LaTiO2N grains on the electrode serve as a highly active O-2-evolving photoanode achieving 8.9 mA cm(-2) of the photocurrent density at 1.23 V versus reversible hydrogen electrode (RHE) in 0.1 M NaOH (pH 13) under solar-simulator irradiation Airmass 1.5 Global (AM 1.5G). The activity has been much improved, compared with conventional LaTiO2N treated in mineral acid or with CoOx deposited by impregnation. The new electrode also exhibits better durability in fixed-potential chronoamperometric tests under AM 1.5G irradiation.

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.

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.

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.

AST-type zeolite with a plate morphology can be synthesized by topotactic conversion of a layered silicate (beta-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.

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.

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.

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.