Fundamental properties of TiO$_{2}$ nanostructures: the effects of the size confinement and the surface coverage

The titanium dioxide (TiO$_{2}$) complexes are widely investigated for their multipurpose capabilities. We discuss here a characterization of anatase TiO$% _{2}$ 0D clusters (NCs) and 1D nanowires (NWs) in the framework of ab initio DFT calculations. Based on both theoretical and experimental evidences, we defined an anatase TiO$_{2}$ NC by modifying a perfect bipyramidal morphology and then used this NC as a chain repetition unit in the anatase NW. We studied the size confinement and analyzed the effect of surface coverage by functionalization with simple water-derived adsorbates. We found that the structural reconstruction fit the available experimental data, that the band gap shift depends on the crystallinity and that the hydration is important in stabilizing the nanostructures.