Surface properties and nanoparticles morphology: the keys to understand the reactivity of semiconductor oxides

Nowadays semiconductor oxide nanocrystals are widely employed in dye sensitized solar cells (DSSCs) and in phototocatalysis. In these applications the relevant phenomena are occurring at the surface of the nanoparticles, therefore the investigation of the relations between particles morphology and surface properties is crucial to understand their reactivity and to improve their performance. Spectroscopic methods are very effective in unravelling structure and reactivity of oxide surface sites. In particular, the IR spectroscopy of adsorbed carbon monoxide, used as molecular probe, allows to obtain information at molecular level on the different exposed surfaces. In our study we show that the spectroscopic results combined with first-principles calculations and high resolution transmission electron microscopy (HRTEM) provide a powerful tool to correlate the spectral features with surface properties and particles morphology. The information obtained with this approach represent the initial point for a further investigation of the reactivity of the different nanoparticles surfaces. In this respect, we studied on different oxides (TiO2, ZnO, MgO) the in situ growth of colored acetylene polymers, which could act as potential sensitizers to improve the visible light photoactivity of the material.