Silica-titania thin films

Martin A.J. Green M. Sol-gel nano-porous silica-titania thin films with liquid fill for optical interferometric sensors. Proc. Soc. Photo-Instrumentation Eng. 1990 1328 352-362... 

Sol-gel optical sensors were developed for many different applications the determination of pH [160], measuring the absorbance of common pH indicators immobilized in thin-film silica matrices [161,162] or as a coating in fiber-optics, where the evanescent wave absorption is measured [163,164], and sensors based on fluorescent pH indicators in hybrid matrices [165,166] were also developed, showing excellent reproducibility and reversibility. Zirconia in hybrid films doped with methyl-red showed reversible response to acid and base vapors [167]. Silica-titania thin films with entrapped sensing molecules have been developed as pH sensors [168]. 

Organic fluorescent dyes trapped in silica and silica-titania thin films by the sol-gel method. Photophysical, film and cage properties. /. Non-Cryst. Solids, 74, 395-406. 

Titania and silica glass thin films Au, Pt Photoreduction of HAuCl and K.2PtCl4 in ethanol-water in the presence of poly(N-vinyl-2-pyrrolidone) or poly(methyl vinyl ether led to metal particles (sizes depended on solvent composition the smallest, 2.8 nm in diameter, was obtained in 100% alcohol) which were mixed with Ti(i-OC3H7)4 and acetylacetone under N2. Subsequent to 30 minutes of stirring, exposure to moisture produced Ti02-embedded metal particles 74... 

Alberius, P. C. A. Frindell, K. L. Hayward, R. C. Kramer, E. J. Stucky, G. D. Chmelka, B. F. 2002. General predictive syntheses of cubic, hexagonal, and lamellar silica and titania mesostructured thin films. Chem. Mater. 14 3284-3294. 

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. 

Instead of the system silica/silicate also other systems such as titania/titanate, zirconia/zirconate can be used as a reference system [xiv]. The response time of freshly fabricated thick-film sensors based on thin-film /3-alumina is very short (about 15 ms at 650 °C). After several weeks of operating this time increases 10 times (150 ms) [xv]. Solid electrolyte C02 sensors using Ni/carbonate composite as measuring electrode are suited for measuring of C02 in equilibrated water gases [xiv]. Using semiconducting oxides and carbonates like ITO (indium tin oxide) Nasicon-based C02 sensors are able to measure at room temperature [xvi]. 

PC.A. Alberius, K.L. Frindell, R.C. Hayward, E.J. Kramer, G.D. Stucky, and B.F. Chmelka, General Predictive Syntheses of Cubic, Hexagonal, and Lamellar Silica and Titania Mesostructured Thin Films. Chem. Mater., 2002, 14, 3284—3294. 

While silica is probably the most frequently encountered oxide surface, other materials particularly alumina, titania and zirconia also have considerable use and spectroscopic characterization is beneficial. One study mentioned above explored the potential for modifying alumina, zirconia, titania and thoria surfaces in a marmer similar to silica [6]. While bonding of the moiety is usually the method of choice, in some cases adsorption is sufficient. For example, polyacrylates adsorbed on alumina are a useful dispersent in the production of certain ceramic products. The successful adsorption of these compounds on aluminia has been monitored by FTIR using the carbonyl stretching frequency for the acrylate species which appears between 1602-1606 cm [15]. Polybutadiene which has been adsorbed on alumina for use as a chromatographic phase can be detected by FTIR [16]. A similar adsorption process has also been tested on zirconia [17,18]. It has also been shown that FTIR can be used to detect Langmuir-Blodgett layers on the metal surfaces of thin-film devices [19]. 

Shimomura K., Tsurami T., Ohba Y., Daimon M. Jpn. Preparation of lead zirconate titanate thin film by hydrothermal method. J. Appl. Phys. 1991 31 2174—2177 Syms R.R.A., Holmes A.S. Deposition of thick silica titania sol-gel films on Si substrates. J. Non-Cryst. Solids 1994 170 223-233... 

Hilsing N., Launay B., Doshi D., Kickelbick G. Mesostructured silica-titania mixed oxide thin films. Chem. Mater. 2002 14 2429-2432... 

Alternative modification methods for sol-gel coatings of silica, titania and silica titania using ultraviolet irradiation and water vapor. Thin Solid Films, 351 (12), 91-94. 

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