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

Abstract

We report element-specific X-ray spectroscopy results on the structure and bonding of Au24Pt, a thiolate-protected bimetallic nanocluster. Platinum L3-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 Au13 core. Comparison of Au24Pt with the structure of Au25 by gold L3-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.