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Abstract: Solid state 1H, 29Si and 31P MAS NMR have been used to investigate the microstructure of phosphosilicate gels prepared by a modified sol–gel method involving hydrolysis of silicon precursors in a solely aqueous environment at 50°C. Gels with molar compositions 5, 10, 20 and 30mol% P2O5 in P2O5–SiO2 were studied. After drying to 400°C the gels have very similar structures formed by a siloxane framework containing silanol groups and trapped molecules of orthophosphoric acid together with a very small amount, of pyrophosphoric acid. Unlike the gel samples previously synthesized by the hydrolysis of the silicon precursor in alcoholic solution at room temperature, the co-polymerization of phosphorus and silicon is much reduced. Although co-polymerization increases with phosphorus content, it still represents less than 50% of the phosphorus in the 30mol% P2O5 gel. Furthermore there is no evidence for six-coordinated silicon in the glassy matrix. [Copyright &y& Elsevier]

Abstract: The performances of Nb2O5–SiO2 catalysts prepared by sol–gel technique in the epoxidation of soybean oil with hydrogen peroxide have been investigated. The most active catalyst showed a good activity in epoxidation reaction but also a low selectivity to epoxide. The low selectivity has been attributed to the presence on the surface besides the Lewis acid sites, that promote the epoxidation, also of strong Brønsted acid sites, that promote the reaction of ring epoxide opening by hydrolysis. [Copyright &y& Elsevier]

Two synthetic strategies were developed for in-situ modification of a silica sol gel matrix in a PEEK tubing, to obtain a hybrid monolith with entrapped lipases. A suitable combination of the sol-gel precursors (tetramethoxysilane, methyltrimethoxysilane and n -propyltrimethoxysilane) was found, for the simultaneous improvement of the monolith adhesion to the tubing internal surfaces and of the catalytic properties of the entrapped enzyme. The effects of the immobilization procedure were characterized as regards both the catalytic properties of the enzyme, as well as the secondary structure of lipases by FTIR. The catalytic efficiency of the entrapped enzyme was better preserved in more hydrophobic microenvironment. The improved stability of the biocatalysts allows further industrial applications. [ABSTRACT FROM AUTHOR]

A method is developed for rapid preparation of titania substrates using a sol–gel preparation route in combination with an amphiphilic block copolymer (BCP) template, acting as structure directing agent. The method consists in performing the spin coating of an initial solutions of BCP and titania species in a controlled atmosphere using a flux of solvent vapors (Rapid-Flux-Solvent-Atmosphere, RFSA method). The method is demonstrated in the case of thin films of polystyrene- b -poly(oxyethylene) BCP (PS-PEO) with cylindrical morphology of PEO domains in the PS matrix, characterized by the selective inclusion of titanium species inside the PEO cylinders. Upon removal of the organic matrix by heat treatment at 600 °C, titania substrates of different morphology are obtained depending on the concentration of titania precursor and processing conditions. The method allows preventing the negative effect of hydrolysis and condensation reactions of Ti species and titania substrates with morphology reminiscent of that one achieved in the hybrid nanostructured thin films are obtained. The RFSA method is simple, direct, and it is of particular interest for systems that require a short processing time to eliminate the solvent and to obtain regular nanostructured thin-films over large area. Merit figures such as the degree of hexagonal order and the degree of coverage of the surface with titania motifs are identified to characterize the hybrid composites and titania substrates. [ABSTRACT FROM AUTHOR]

Highlights: [•] Catalytic activity of a class II hybrid ZrO2-acetylacetonate gel-derived material. [•] Oxidative degradation of phenantrene in aqueous solution without light irradiation. [•] Free radicals formed by an intramolecular ligand-to-metal electron transfer mechanism. [Copyright &y& Elsevier]

Abstract: The main aspects of the sol–gel synthesis of ZnO thin films were critically examined with particular reference to the optimization of the process parameters that influence specific properties of the films, such as the transparency, the crystallization behavior and the electrical resistivity. Starting from zinc acetate dihydrate, anhydrous ethanol and triethanolamine, a valuable sol–gel route was set. This route allowed the preparation of transparent ZnO thin films by dip-coating. Triethanolamine, thanks to its high chelating efficiency towards Zn2+, permitted to prepare stable zinc acetate dihydrate solutions wholly at room temperature. The structural, optical and morphological characteristics of the films were examined by glancing incidence X-ray diffraction, UV–vis spectroscopy and atomic force microscopy. Single layer films, with a thickness of about 120nm, characterized by a high adhesion force (about 140Kgcm−2), were obtained. The crystallization behavior of dip-coated amorphous films was explored in the 500–600°C range; polycrystalline films, formed by randomly oriented ZnO nanocrystals (about 20nm), with an average transmittance higher than 90% in the visible region, were obtained. Finally, a strong influence of annealing environment on electrical resistivity was observed. [Copyright &y& Elsevier]

Abstract: New nanodispersed Cu–ZrO2 systems (containing 0 and 8.3mol% Cu) were synthesized by sol–gel method. Homogeneous gels were prepared starting from Zr propoxide and Cu(NO3)2·2.5H2O. The materials were characterized by XRD, TG/DTA, N2 adsorption, TPR techniques and N2O surface oxidation. In the Cu-containing material part of Cu2+ ions were incorporated into the zirconia lattice and strongly influenced the crystallisation behaviour of zirconia matrix. After treatment at 450–600°C, the materials contained ZrO2 nanocrystals of the tetragonal polymorph. The samples heat treated up to 450°C showed high surface areas in the range 140–180m2/g. Copper oxide species with different reducibility were detected by TPR measurements. The H2 reduction treatments gave rise to metallic copper with very high dispersion. The catalysts showed high activity for the oxidative steam reforming of methanol. A noticeable activity was observed also with the not pre-reduced catalyst, although a previous reduction in H2 led to a higher selectivity and H2 production. [Copyright &y& Elsevier]