Gold Oxide Nanoparticles with Variable Gold Oxidation State

Gold-oxide-containing nanoparticles have been produced in a range of partial to full oxidation conditions, where the nanoparticle electronic structure and stoichiometry have been characterized. Our results indicate that with the increase of the oxidation degree in these nanoparticles the gold oxidation state possibly changes from lower oxides with monoor divalent metal to the higher oxide with the trivalent gold. At intermediate oxidation conditions our observations are consistent with a radially segregated structure of such nanopaiticles-with the core containing mainly oxide and the surface covered with few monolayers of metallic gold. These results have been possible to obtain combining the vapor aggregation method for the nanoparticle fabrication and synchrotron-based photoelectron spectroscopy for their characterization. The deposition of the oxidized nanoparticles has showed that the species assigned as containing lower oxide could be preserved in the landing and then studied on a substrate for a limited time. The possible lower oxide formation in nanoparticles is discussed in connection to the enhanced catalytic activity of gold nanoparticles.