Integrated experimental and theoretical study of surface properties of TiO2 nanoparticles.

Nanostructured titania is rising an increasing interest as one of the key materials for the actual setting of sustainable processes based on the use of sunlight as source of energy. A relevant target is the disclosure of the main structural and surface features that can rule the performances of titania. In this respect, this Ph.D. thesis has been devoted to the study of surface properties of TiO2 nanoparticles with the combined use of IR spectroscopy of adsorbed probe molecules/groups (OH/H2O, CO) and theoretical modeling. The experimental study of the TiO2 surface sites, with a relevant role for the surface chemistry, allowed to individuate some vibrational bands, due to surface defective sites of TiO2 P25 (Degussa), a kind of benchmark for the photocatalytic applications of titania. The use of this material represents a source of complexity in this kind of investigations, since the roughness of nanocrystals borders causes the presence of a wide heterogeneity of surface sites with different local structures. Therefore, a TiO2 sample with nanoparticles of regular shape and exposing defined surfaces, has been studied. The a priori knowledge of the surface sites structure has allowed the unambiguous assignment of some of the vibrational bands of the IR spectra of adsorbed probe molecules. These data have been used as reference for the simulation of the IR spectra of adsorbed CO, that allowed the assignment of other signals not attributed on the only basis of experimental data. The role of the TiO2 surface has also been studied through the TiO2-biomolecules interaction, that provided evidence of the catalytic role of TiO2 surface in promoting the formation of peptidic bond among adsorbed biomolecules.