Bezrodna T. Spectroscopic investigations of structure and molecular interactions peculiarities in heterogeneous nanosystems based on titanium dioxide.

The thesis is devoted to the investigations of interaction mechanisms between organic polar molecules and TiO2 particles depending on TiO2 crystalline structure (anatase, rutile), thermal treatment and its surface modification by different transition metals (Cu, Mn, Cr, Co, Ni, Fe). The stochiometric composition O/Ti (~ 2) and nanocrystals sizes (~ 5-15 nm) of TiO2 polydisperse samples have been determined. The main anatase surface active centers have been found out to be Brensted and Lewis acids, while in the case of rutile there are only Lewis ones. The hydrate covering of TiO2 particle surface is formed by adsorbed water molecules, interacting with the hydroxyls of TiO2 surface by relatively weak (~ 5 kcal/mol) and strong (~ 7 kcal/mol) hydrogen bonds. Nitrobenzene molecules interact with TiO2 surface by means of weak Van-der-Vaals forces. It has been found out that weak hydrogen bonds of -CN…HO-Ti type form in heterogeneous systems based on 5CB liquid crystal and polydisperse TiO2. Metal cations, being adsorbed on TiO2 surface have a polarizing effect on 5CB molecules, according to values of their polarizing potentials. In all studied heterogeneous systems with benzophenone the last one exists simultaneously in its stable ?-crystal and ?-amorphous. Benzophenone molecules form relatively strong hydrogen bonds with the hydroxyls of TiO2 surface via their CO groups and also coordination ones with Lewis centers on the TiO2 surface. Molecular interactions of different polar organic molecules with polydisperse TiO2 have been shown to be an efficient method for the characterization of different active centers on the TiO2 surface