Preparation by the Sol-Gel Method

The photochromisms of spiroindolinobenzopyrans trapped in glass prepared by the sol-gel method have been stuied.36,37... 

Figure 6. Photocurrent-bias characteristics of TIO2 coating films with different thicknesses prepared by the sol-gel method. (Reproduced with permission from Ref. 10. Copyright 198 The Ceramic Society of Japan.)...

Siouffi, A.M. (2003). Silica gel-based monoliths prepared by the sol-gel method facts and figures J. Chromatogr. A 1000, 801-818. 

Encapsulation of proteins in transparent porous silicate-glasses prepared by the sol-gel method. Science, 255, 1113-1115. 

The way of enzyme entrapment has been described79 proposing the application of sol-gel matrices. The optodes of urea sensor were prepared by the sol-gel method and were stored in a refrigerator. As the pH sensitive dye the bromothymol blue was used. Since it is best acting in pH range 6 to 7.6, the pH of sol-gel bulks obtained in the experiment was chosen as pH 6. Before measurements, the optodes were incubated in the temperature 36.6°C. 

L.M. Ellerby, C.R. Nishida, F. Nishida, S.A. Yamanaka, B. Dunn, J.S. Valentine, and J.I. Zink, Encapsulation of proteins in transparent porous silicate glasses prepared by the sol-gel method. Science 255, 1113-1115 (1992). 

The copper-ceria catalysts in WGS were found to be nonpyrophoric and stable, showing little or no deactivation during the experiments. The Civ,2Ce(J802 y catalyst prepared by coprecipitation method showed good catalytic activity for the WGS reaction. The Cu0, Ce0 902 v catalysts prepared by the sol-gel method were found to be less active, which could be due to the lower number of active... 

The CiijCe, r02 v nanostructuied catalyst prepared by the sol-gel method is a very efficient and selective CO oxidation catalyst even under the highly reducing conditions which are present in a PrOX reactor. It is energy efficient toward the PEM fuel cell technology, because it oxidizes CO... 

J. D. Protein-doped monolithic silica columns for capillary liquid chromatography prepared by the sol-gel method applications to frontal affinity chromatography. Anal Chem... 

The initial interaction of Ru3(CO)i2 with the surface of several oxides has been extensively studied by EXAFS and IR spectroscopy [70,100]. Representative studies of materials prepared from Ru3(CO)i2 and zeolites ]101, 102] or MCM-41 related supports [97] have also been reported. Ru/Si02 has also been prepared by the sol-gel method, using Ru3(CO)i2 and tetramethoxysilane as precursors [98] spheroidal metal particles homogeneously dispersed into the sihca matrix with a size range from 1 to 4nm were obtained after decarbonylation at 573 K under He, followed by H 2-treatment. 

Bei Z, Ren D, Cui X, Shen J, Yang X, Zhang Z (2004) Photoelectrochemical properties and crystalline structure change of Sb-doped TiOz thin films prepared by the sol-gel method. J Mater Res 19 3189-3195... 

Fluorhydroxyapatite solid solutions can be prepared by the sol-gel method [134,135]. Cheng et al. reported the control of fluoride content in fluorhydroxyapatite solid solutions by the amounts of triethanolamine (N(CH2CH20H)3) and trifluoroacetic acid (CF3COOH) in the mixed ethanol solutions of Ca(N03)2 and P0(CH2CH20H)x(0H)3 x with a Ca/P ratio of 1.67 [134]. After evaporation of the mixed ethanol solution at 150°C on a hot plate, the powder obtained, comprising a homogeneous mixture of calcium nitrate crystallites and amorphous calcium phosphates, is then heated at 500 or 900°C for 1 h to be transformed into the pure apatitic phase. 

Several examples discussed below illustrate the method two of the examples have been chosen because they have interesting properties and uses, discussed later on in this book. Many other materials have been prepared by the sol-gel method, and other sol-gel preparations have been employed for the materials chosen. Therefore, these examples should be taken as illustrative and not as the main uses of the method. 

Harmer et al.196 used 1,1,2,2-tetrafluoroethanesulfonic acid in the alkylation of para-xylene with 1-dodecene. The silica-embedded catalyst prepared by the sol-gel method showed much higher activity than the neat acid (almost complete conversion in 15 min at 100°C over the sol-gel-derived material versus 10% conversion, using the same molar amounts of acid). Practically no leaching was detected and the catalyst could be recycled with a slight decrease in conversion. It is in sharp contrast with silica-supported triflic acid, which showed much lower activity due to the loss of volatile triflic acid. 

UV light induced refractive index change has been observed in organic polysilane (PS)-silica and PS-titania hybrid thin films prepared by the sol-gel method.135 The magnitude of the refractive index change was found to be 0.16 for 50 wt % PS-silica and 0.18 for 50 wt % PS-titania hybrid thin films. It was demonstrated that the refractive index change of the hybrid thin films is due to the photodecomposition of PS. These findings indicate potential usefulness of the hybrid thin films as optical devices with refractive index modulated structures. 

Chiba, R., Yoshimura, F., Sakurai, Y., Tabata, Y., and Arakawa, M. A Study of Cathode Materials for Intermediate Temperature SOFCs Prepared by the Sol-gel Method, Solid State Ionics, 175,23 (2004). 

Lopez et al. [27] prepared Pd/SiC>2 catalysts under both acidic (pH = 3) and basic (pH = 9) conditions in the sol-gel step and reported that an acid medium promotes the formation of small metal crystallites. This finding is consistent with the formation of a micro-porous silica gel network at a low pH. By comparing samples prepared by the sol-gel method and impregnation, these authors found in the former a stronger metal-support interaction which they ascribed to the square planar palladium complex used as a precursor. Finally, their results showed that the method of preparation as well as the conditions used in each method impact on how these catalysts deactivate in the hydrogenation of phenylacetylene. 

Zaspalis and Burggraaf [47] have summarized typical membrane reactor configurations, different membrane/ catalyst combinations, and a large number of membrane reactor studies. Their article clearly shows that inorganic membranes prepared by the sol-gel method, with their dual ability in catalysis and separation, have many unique advantages over other product forms. At the same time, it is important to realize that the parameters which affect a membrane s characteristics and the advantages which the sol-gel process offers are similar to what has been presented thus far. 

Thin-film preparation can be coupled to other synthetic strategies such as sol-gel synthesis. For example, Qide et al. presented a synthesis of Ti02 thin films prepared by the sol-gel method (Qide et al., 2003). The interest in thin films of Ti02 lies in the application of these films to photocatalysis. Ti02 has been shown to be photocatalytic with respect to the oxidation of organic contaminants such as chloroform (Fujishima et al., 1999) ... 

Photocatalysis on I itanium-Silicon Binary Oxides Prepared by the Sol-Gel Method... 

As shown in Fig. 65, titanium-silicon binary oxides prepared by the sol-gel method exhibit a characteristic photoluminescence spectrum near 480 nm upon excitation at 280 nm. The absorption and photoluminescence spectra are attributed to the charge-transfer processes on the highly dispersed tetrahedral titanium oxide species embedded in the Si02 matrices (168, 200, 201). When the titanium content of the oxides was decreased, the intensity of the photoluminescence spectrum increased, and its peak wavelength shifted to shorter wavelengths. 

These hhns are prepared by the sol-gel method using heat treatment. The Si02 him is formed using a Si02 sol solution and the Sn02 hhn is formed using... 

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