Site-specific bonding analysis of Pt- and Pd-doped Au ₂₅ (SR) ₁₈ nanoclusters using EXAFS simulations

Thiolate-protected Au nanoclusters such as Au 25 (SR) 18 are receiving increasing attention for their unique structural and electronic properties, especially when modified via single-atom doping. In this study, we employed extended X-ray absorption fine structure (EXAFS) simulations to investigate the effects of substituting the central Au atom with Pd and Pt in Au 25 (SR) 18 , generating Au 24 Pd(SR) 18 and Au 24 Pt(SR) 18 nanoclusters. Site-specific EXAFS spectra for the central, surface, and staple atomic sites as well as the averaged overall spectrum based on these key sites were analyzed to assess changes in coordination environments and bonding characteristics. Our findings reveal that while the doped central atoms exhibit bulk-like bonding, the surface Au atoms show the most pronounced structural changes, significantly influencing the overall EXAFS features. In contrast, the staple sites are less affected by single-atom doping and retain the original molecule-like properties. These results highlight the sensitivity of EXAFS in single-atom doping investigations of metal nanoclusters and the importance of site-specific analysis for their potential applications, such as in designing single-atom alloy nanocluster catalysts.