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 depositi on technique on the basis of mesoporous silica with different contents of g rafted TiO2 were investigated. For these samples, the chemical shifts of ad sorbed water, the thickness of the hydrate shell, and the free surface ener gy of aqueous medium were measured using the H-1 NMR method. It was estimat ed that the chemical shift (delta) of the adsorbed water is between 2.6 and 3.8 ppm. For the sample with 7.7 wt % TiO2, the signal of strongly bonded water with delta = 1.3 ppm is present in the spectra of adsorbed water. Pro bably this signal is caused by the water molecules, which form the electron -donor complexes with Ti atoms. With increasing TiO2 concentration, the fre e surface energy (Delta G(Sigma)) 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 % Ti O2 and then increases up to 130 mJ/m(2) for the sample with 7.7 wt % TiO2 c oncentration. The values of Delta G(Sigma) for porous and nonporous materia ls were compared.