Dopant Location, Local Structure, and Electronic Properties of Au24Pt(SR)18 Nanoclusters

We report element-specific X-ray spectroscopy results on the structure and bonding of Au24Pt, a thiolate-protected bimetallic nanocluster. Platinum L-3-edge extended X-ray absorption fine-structure (EXAFS) data, in association with X-ray photoelectron spectroscopy (XPS) compositional analysis, was used to identify the location of the Pt dopant to be in the center of the icosahedron Au-13 core. Comparison of Au24Pt with the structure of Au-25 by gold L-3-edge EXAFS clearly shows contraction of both metal-thiolate and metal-metal bond distances, caused by Pt doping. The doping effect on the electronic properties of Au24Pt was further evaluated by high-resolution Au 4f core-level XPS and ab initio calculations, which elucidate the importance of bimetallic (Pt-Au) bonding and bond contraction effects on the properties of Pt-doped thiolate-gold nanoclusters.