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A variety of advanced functions such as hydrophilicity and hydrophobicity are required for transparent glass plates recently. This paper reports a new procedure to produce transparent silica thin films on glass plates obtained from sodium silicate as inexpensive silica source by its dip coating and subsequent deposition of silica with (NH 4 ) 2 SO 4 solution. When the thin films were prepared using bovine serum albumin (BSA), the resulting transparent films became more hydrophobic than that obtained without BSA and had good adhesion with water droplet, the so-called “petal effect”. Water droplet on the silica thin film did not slide down even when the substrate turned vertically and upside down. Although no BSA was included in the silica thin film, BSA contributed to the formation of nano-sized asperity structures in the film, producing more hydrophobic (less hydrophilic) property and the petal effect. [ABSTRACT FROM AUTHOR]

Abstract: Silica hollow particles (microcapsules) are one of the exciting subjects in materials chemistry in both basic and applied researches. Our previous paper reported a new preparation method of silica hollow particles having unique shell with macropore holes, which resemble diatomaceous earth in morphology, by interfacial reaction method using W/O/W emulsion as a reaction field. The preparation procedure of these unusual silica particles inherently requires the addition of suitable amounts of sodium polymethacrylate to the sodium silicate solution as the internal water phase of the W/O/W emulsion. For revealing the detailed mechanism of the formation of the shells with macropore holes, silica thin films using the similar solutions were examined as a model system of the interfacial reaction method, because both processes produce silica thin matrices such as shell or as film, respectively. Some silica thin films with macropore dents were formed by immersing dip-coated films of sodium silicate and sodium polymethacrylate into NH4HCO3 aqueous solution. FE-SEM/EXD observation indicated that the modest phase separation of sodium silicate and the polymethacrylate occurred in the dip-coated films before the immersion into NH4HCO3 solution. Moreover, infrared spectrometry studies revealed that the addition of sodium polymethacrylate to sodium silicate changed the bonds of the silicate significantly to promote the condensation. The experimental observations in these model studies strongly suggested that the shell with macropore holes in diatomaceous earth like silica hollow particles are formed by the removal of the aggregated and the phase-separated polymethacrylate during the formation of silica matrix of the particle shell. [Copyright &y& Elsevier]

Abstract: Although the versatilities of zeolitic materials are widely known to chemists and materials scientists, their exclusive microporosity sometimes causes various defections especially in the diffusion of reactant and product molecules in catalytic reactions. Silica–alumina/epoxy-resin composite materials were obtained from TMOS (tetramethoxysilane), aluminum acetylacetonate and bisphenol A diglycidyl ether with a cyclic acid anhydride as both condensation and curing reagents. Hydrothermal treatment of the composite materials with TPAOH (tetra-n-propylammonium hydroxide) crystallized the amorphous silica–alumina part to the MFI zeolite crystalline phase and induced the phase separation of epoxy-resin domain from the zeolite phase at the same time, forming both zeolite microporosity and mesoporosity in the solid catalyst after calcination. The mesoporous MFI zeolite thus prepared had a good catalytic activity in liquid phase Friedel–Crafts benzylation reaction. The mesoporous channels fabricated in the MFI zeolite material enhanced the diffusion of reactants and products in the solid matrix, and thus it showed a better catalytic activity in the benzylation of toluene together with the high selectivity of the mono-substituted para-isomer. The new methodology reported in this paper to produce the mesoporous zeolite materials will promote the chemistry and the applications of zeolite catalysts and related materials. [Copyright &y& Elsevier]

Silica-zirconia (SiO2-ZrO2) materials including bisphenol A (BPA) were prepared by a sol-gel method using tetraethoxysilane, zirconium complexes and acetic anhydride in organic solution. The removal of BPA from SiO2-ZrO2 materials is expected to form BPA-imprinted sites in the solid matrices. Both the molecular shape and the positions of OH groups of BPA were considered to be imprinted. The acidic sites induced by isomorphously substituted Zr atom in silica matrix play the role in recognizing the OH groups of BPA. A BPA imprinted SiO2-ZrO2 material preferentially adsorbed BPA and steroid hormones from the mixed solution of other reference molecules. [ABSTRACT FROM AUTHOR]

Abstract: Mesoporous silica/polymer sulfonate composite materials were prepared by simply mixing hexadecyltrimethylammonium bromide, polymer sulfonates and TEOS (tetraethoxysilane) in alkaline aqueous solution. Nafion and poly(sodium 4-styrenesulfonate) were employed as polymer sulfonates. XRD patterns and nitrogen adsorption–desorption isotherms showed that the precipitates obtained had mesostructure similar to MCM-41. Especially, the crystallinity of hexagonal structure of composite materials synthesized with Nafion was high. From all the results obtained here, it is concluded that the polymer sulfonate resins might be incorporated in the wall framework of mesoporous silica matrix. However, when the excess amount of Nafion was mixed, the acid sites of Nafion were significantly lost in the obtained materials. These composite materials present new classes of organically modified mesoporous silicas, where organic polymers are incorporated in the framework of mesoporous silica. They were used as catalysts for α-methylstyrene dimerization and Friedel–Crafts alkylation reaction of aromatics. [Copyright &y& Elsevier]

It is well known that a silica surface cannot adsorb duplex DNA in common aqueous solution (not chaotropic solution) because of the electrostatic repulsion of the silica surface and polyanionic DNA. However, we recently found that when duplex DNA in phosphoric acid form (or in acidic solution) was used, DNA was successfully adsorbed into mesoporous silicas even in low-salt aqueous solution. The adsorption behaviors of DNA into mesoporous silicas were influenced by the pore diameter sizes. Mesoporous silicas with 2.80- or 3.82-nm peak pore diameters adsorbed DNA the best in diluted NaCl solution. Formation of the hydrogen bond between P(O)OH groups in DNA and adsorbed water, SiOH groups, or both on silica surfaces is regarded as a main factor in this adsorption. The coincidence of the pore sizes and DNA diameter realizes this unique adsorption promoted by the effect of encompassing DNA With the inner surface of mesoporous silica. Although there is no clear direct evidence for including duplex DNA in the mesopores yet, this adsorption technique is expected to provide a new tool for DNA science, because DNA in the pore size 2-5 nm in diameter has to be in unusual disentangled thread form. [ABSTRACT FROM AUTHOR]

Since the discovery of MCM-41 more than ten years ago, many investigations have explored the suitability of hexagonal mesoporous silicas for potential practical applications. These range from catalysis and optically active materials to polymerization science, separation technology and drug delivery, with recent successes in the fabrication of hybrid mesoporous organosilicas expected to open up further application possibilities. Because the pore voids of this class of materials exhibit relatively narrow pore size distributions in the range of 2–4 nm in diameter, mesoporous silicas can selectively include organic compounds and release them continuously at a later stage. The functionalization of MCM-41 pore voids with photoactive derivatives provides influence over the material's absorption behaviour, but full control over the release process remains difficult. Here we show that the uptake, storage and release of organic molecules in MCM-41 can be regulated through the photocontrolled and reversible intermolecular dimerization of coumarin derivatives attached to the pore outlets. Successful functionalization requires uncalcined MCM-41 still filled with the template molecules that directed the formation of its pores, to ensure that coumarin derivatives attach preferentially to the pore outlets, rather than their inside walls. We find that this feature and the one-dimensional, isolated nature of the individual pores allow for efficient and reversible photocontrol over guest access to the material's interior. [ABSTRACT FROM AUTHOR]