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 Au-8 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 similar to 2-3 nm. STM studies on Au-7 suggest that Au-7 exists as individual clusters rather than forming larger particles on the surface. (C) 2007 Elsevier B.V. All rights reserved.