Site-selective substitution of gold atoms in the Au24(SR)20 nanocluster by silver.

The synthesis and structure determination of atomically precise alloy nanoclusters have attracted much attention in recent research. Herein, we report a new alloy nanocluster Au 24- x Ag x (TBBM) 20 ( x ∼ 1) synthesized via a ligand-exchange-induced size/structure transformation method. Its X-ray structure is obtained successfully and the dopant Ag is found to occupy three special positions in the kernel, rather than equivalently over all the kernel sites. This selective occupancy is interesting and DFT calculation results suggest that the relative oxidation state (rationalized as difference in the charge) of the Ag when doped into the cluster is likely determining the most favorable doping positions. This work provides a new strategy for controlled synthesis of new Au-Ag nanoclusters and also reveals a new scenario for the doping position of Ag atoms in Au-Ag bimetal nanoclusters. [ABSTRACT FROM AUTHOR]