Site-Specific Electronic Properties of [Ag25(SR)18]- Nanoclusters by X-Ray Spectroscopy

We present the site-specific electronic properties of Ag₂₅(SR)₁₈ and Au₂₅(SR)₁₈ using X-ray spectroscopy experiments and quantum simulations. To overcome the final state effect observed in X-ray photoelectron spectroscopy (XPS), a unique method was developed to reliably analyze the charge transfer behavior of the NCs. Density functional theory calculations were combined with XPS to provide more insight into the electronic properties of the NCs. The differences in the XPS valence bands of these two NCs were further compared and interpreted using the relativistic effect. The first derivative of the X-ray absorption near-edge structure (XANES) spectrum was further used as a tool to sensitively probe the bonding properties of Ag₂₅(SR)₁₈. By combining the experimental XANES data and their site-specific quantum simulations, the large impact of the staple motif on the bonding properties of the NC was demonstrated. These findings highlight the unique electronic properties of each atomic site in Ag₂₅(SR)₁₈; the effective X-ray analysis techniques developed here can offer new opportunities for the site-specific study of other NCs.