Electronic Structure and Bonding of Icosahedral Core–Shell Gold–Silver Nanoalloy Clusters Au144–xAgx(SR)₆₀

Atomically precise thiolate-stabilized gold nanoclusters are currently of interest for many cross-disciplinary applications in chemistry, physics, and molecular biology. Very recently, synthesis and electronic properties of “nanoalloy” clusters Au 144– x Ag x (SR) 60 were reported. Here density functional theory is used for electronic structure and bonding in Au 144– x Ag x (SR) 60 based on a structural model of the icosahedral Au 144 (SR) 60 that features a 114-atom metal core with 60 symmetry-equivalent surface sites and a protecting layer of 30 RSAuSR units. In the optimal configuration the 60 surface sites of the core are occupied by silver in Au 84 Ag 60 (SR) 60 . Silver enhances the electron shell structure around the Fermi level in the metal core, which predicts a structured absorption spectrum around the onset (∼0.8 eV) of electronic metal-to-metal transitions. The calculations also imply element-dependent absorption edges for Au(5d) → Au(6sp) and Ag(4d) → Ag(5sp) interband transitions in the “plasmonic” region, with their relative intensities controlled by the Ag/Au mixing ratio.