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TiO2 films prepared by template-assisted sol–gel method were characterized by X-ray diffraction spectroscopy, scanning and atomic force electron microscopy, and Fourier transform infrared (FT-IR) spectroscopy. Based on the hexane adsorption–desorption analysis, the films have a surface area of 390–540 m2/g with pore size distribution narrowly centered around 10 nm. Optimal component ratio and condition of heat treatment of mesoporous titania films have been found. Photocatalytic activity of the coatings was determined by the destruction of stearic acid layers, monitored using FT-IR spectroscopy and laser desorption–ionization (LDI) mass spectrometry. Under UV illumination, all the used films reach hydrophilicity with water contact angle of 0°. As the result, hydrophobic fat acid molecules undergo self-association and active desorption from the hydrophilic surface during mass-spectrometric experiment.

The effect of nanosized porous films (average density 10 g/m 2 ) of TiO 2 . TiO 2 /SiO 2 , and SiO 2 on the photostability of adsorbed methylene blue (MB) dye during UV irradiation in air was investigated by optical spectroscopy and laser-induced mass spectrometry. The effectiveness of the photodecomposition of MB decreases in the order TiO 2 > TiO 2 /SiO 2 > SiO 2 with rate constants 1E-2, 0.6E-2, and 0.3E-2 min -1 respectively. A mechanism including the participation of both excited states of the dye molecules and photoexcited titanium dioxide is proposed for the photodecolorization of MB adsorbed on the surface of the investigated films.Acridine, xanthene, thiazine, triphenylmethane, and other dyes that absorb visible light and have bright colors are of enormous scientific and technical interest on account of their use in chemical and biological processes, laser technology, optical data processing, creation of light-resistant systems, textile industry, etc. At the same time dyes are some of the most widespread contaminants of the environment as a consequence of their stability and consequent ineffective natural biodegradation. Heterogeneous photocatalysis using mostly TiO 2 in the anatase form ([1, 2] and the references therein) is used as an alternative to the traditional poorly effective methods for the purification of contaminated water, such as flocculation, adsorption with activated charcoal, or biopurification. The action of UV irradiation in TiO 2 leads to the generation of electron-hole pairs, which initiate the formation of active OH* radicals capable of decomposing the majority of organic compounds in solutions. The overwhelming majority of publications on the photodegradation of dyes by titanium-containing catalysts have been devoted to analysis of the photocatalysis processes in aqueous solutions, and rhodamines (6G or B) or methylene blue (MB) have often been used as model dyes. Insufficient attention has been paid to study of the state of adsorbed molecules of the dye and its photodegradation at the surface of the photocatalysts in the absence of a solvent [3,4]. In the mean time this problem is urgent not only from the standpoint of the investigation of adsorption as the initial stage of photocatalysis (most authors do not discuss the fate of the dye molecule at the surface of the photocatalyst at all, although it is the surface that has a great effect on the kinetic of the process at the early stages) but is also of independent importance during the design of optical cells with controllable spectral characteristics. The tendency of the adsorbed molecules of dyes to associate and aggregate also affects their photostability and capacity for photodegradation.Earlier we recorded for the first time the calcination fine-structure fluorescence spectra of aromatic hydrocarbons adsorbed on silica with selective laser excitation in the region of the 00 transition at low temperature and detected reversible 0040-5760/07/4304-0235