1.Introduction Supported Au nanoparticles have been extensively investigated in heterogeneous catalysis since the seminal work of Haruta’s research group,in part because of their high activity in some reactions,especially CO oxidation[1–5].Although many studies have been performed,two problems still remain:aggregation of Au nanoparticles and their catalytic reaction 1. Introduction Supported Au nanoparticles have been extensively investigated in heterogeneous catalysis since the seminal work of Haruta’s research group, in part because of their high activity in some reactions, especially CO oxidation [1-5]. Although many studies have been performed, two problems still remain: aggregation of Au nanoparticles and their catalytic reaction