The Innermost Three Gold Atoms Are Indispensable To Maintain the Structure of the Au18(SR)14 Cluster

Abstract

The physical and chemical properties of thiolate-protected metal nanoclusters are highly dependent on their cluster composition. Such physicochemical properties could be further enriched by incorporating two noble metals inside one cluster. Here we report an efficient synthesis of thiolate-protected (AuAg)18 clusters (or Au18-xAgx(SR)14 clusters) by adopting a simple CO-reduction method. The composition and electronic/optical properties of the Au18-xAgx(SR)14 clusters are rationally tuned by adjusting the feeding ratio of Ag-to-Au. The experimental data also suggest that the incoming Ag atoms would first replace the Au atoms in the core and a maximum of six Ag atoms can be incorporated into the structure of Au18(SR)14. More interestingly, doping more than six Ag atoms leads to the collapse of the Au9 core, and the incoming Ag atoms would only go into the motif sites. A detailed investigation on the compositional and optical properties of the as-doped AuAg clusters finally highlights the crucial role of th...