Chemistry of mass-selected Au clusters deposited on sputter-damaged HOPG surfaces: The unique properties of Au8 clusters

Mass-selected Au clusters consisting of less than 10 atoms were deposited on sputter-damaged HOPG surfaces. Oxidation and reduction of the Au clusters were studied using X-ray photoelectron spectroscopy. Only Au8 can be significantly oxidized by oxygen and reduced by CO, and the result is different from those for Au clusters deposited on silica. The chemical properties of mass-selected clusters are dissimilar to those of Au nanoparticles larger ∼2–3 nm. STM studies on Au7 suggest that Au7 exists as individual clusters rather than forming larger particles on the surface.