OSCAR has demonstrated that, amongst the relevant parameters controlling the gold NP catalytic activity, there are the charge transferred from the metal-oxide support to the NP and the type of NP growth mode (nucleation vs growth process). As a further step, the effect on the charged state of Au/TiO2 caused by the exposure to reactive gases (CO and O2) has been evaluated by X-ray photoemission spectroscopy (XPS) after reactions. It suggests that O2 principally interacts with Ti sites located on the bare surface and not with those already interacting with Au NPs. During the project, the development of existing techniques and of new approach methods has been also achieved. The validation of surface differential reflectivity spectroscopy (SDRS) for studying NP growth in vacuum has been attained by comparing SDRS data to the results obtained by other in situ complementary techniques. In addition, the groundwork for extending the use of SDRS in reactive conditions has been laid by establishing the technical specifications required for running it in near ambient pressures. As a further step, an innovative method that allows to control defect type in TiO2 substrates have been applied for the first time for growing Au NPs. It showed that a larger quantity of charge can be transferred at interface with respect to the use of traditional preparation methods. These results are of high importance because they indicate that the present method may potentially increase the catalytic performances of the Au/TiO2(110) interface, and more in general, the properties of the oxide-based interfaces. In order to extend the results of Au/TiO2(110) to titania phase mixtures and nanostructures, the structural and electronic properties of TiO2 anatase and thin films have been explored. For this purpose, an original method based on Ti LMV Auger spectra taken by XPS has been developed. It allows at laboratory to quantify polymorph and exposed facets in titania phase mixtures. The present quantification method opens interesting perspectives for the characterization of metal-oxide phases and orientations, particularly for thin films which may escape the sensitivity of X-ray diffraction measurements. The formation of titania ultrathin films on polar ZnO substrates has also been studied. Titania films have been grown by evaporating metal Ti on ZnO in ultra-high vacuum followed by annealing treatments. It has been demonstrated for the first time that the polarity of the surface plays a crucial role in the interface reactivity and thermal stability of the film. Depending on the Zn- and O- termination of the (0001) polar surface, Ti forms TiO2 or (Ti, Zn, O) compounds, respectively, with a much lower activation temperature on the O-terminated surface.
