Synthesis of $TiO2$ nanoparticles on the Au(111) surface

The growth of titanium oxide nanoparticles on reconstructed Au(111) was investigated by scanning tunneling microscopy and x-ray photoelectron spectroscopy. Ti was deposited by physical-vapor deposition at $300K$⁠. Regular arrays of titanium nanoparticles form by preferential nucleation of Ti at the elbow sites of the herringbone reconstruction. The titanium oxide nanoclusters were synthesized by subsequent exposure to $O2$ at $300K$⁠. Two-and three-dimensional titanium oxide nanocrystallites form during annealing in the temperature range from $600to900K$⁠. At the same time, the Au(111) surface assumes a serrated ⟨110⟩-oriented step-edge morphology suggesting step-edge pinning by titanium oxide nanoparticles. The oxidation state of the titanium oxide nanoparticles varies with annealing temperature. Specifically, annealing to $900K$ results in the formation of stoichiometric $TiO2$ nanocrystals as judged by the $Ti(2p)$ binding energies measured in the x-ray photoelectron data. The nanodispersed $TiO2$ on Au(111) is an ideal system to test the various models proposed for the enhanced catalytic reactivity of supported Au nanoparticles.