Characteristics of the Hydration Layer Structure in Porous Titania−Silica Obtained by the Chemical Vapor Deposition Method

The titania−silica samples prepared by means of the chemical vapor deposition technique on the basis of mesoporous silica with different contents of grafted TiO 2 were investigated. For these samples, the chemical shifts of adsorbed water, the thickness of the hydrate shell, and the free surface energy of aqueous medium were measured using the 1 H NMR method. It was estimated that the chemical shift (δ) of the adsorbed water is between 2.6 and 3.8 ppm. For the sample with 7.7 wt % TiO 2, the signal of strongly bonded water with δ = 1.3 ppm is present in the spectra of adsorbed water. Probably this signal is caused by the water molecules, which form the electron−donor complexes with Ti atoms. With increasing TiO 2 concentration, the free surface energy (Δ G Σ ) at first decreases from 160 mJ/m 2, for the initial silica gel, to 90 mJ/m 2 for the sample containing 4.5 wt % TiO 2 and then increases up to 130 mJ/m 2 for the sample with 7.7 wt % TiO 2 concentration. The values of Δ G Σ for porous and nonporous materials were compared.