New Insights on the Bonding Properties of BCC-like Au₃₈S₂(SR)₂₀ Nanoclusters from X-ray Absorption Spectroscopy

X-ray spectroscopy techniques have been known as a useful tool for the study of structure and bonding properties of gold nanoclusters (NCs), and such information has been proven valuable to advance their fundamental research and applications. Herein, we report new insights on the bonding properties of body-centered cubic (BCC)-like Au₃₈S₂(SR)₂₀ nanoclusters from Au L₃-edge X-ray absorption spectroscopy. The first-derivative X-ray absorption near edge structure (XANES) is shown as a sensitive tool to detect the surface structure and bonding properties of the Au NCs. On the basis of the XANES experimental results and quantum calculations, Au–Au bond distance from the NC surface sites is found to be directly related to the early region of the Au L₃-edge XANES spectral features. Extended X-ray absorption fine structure analysis shows significantly shorter Au–Au bond distances in BCC-like Au₃₈S₂(SR)₂₀ in comparison with those in bi-icosahedral like Au₃₈(SR)₂₄ NCs. The contraction of Au–Au bonding upon solvation suggests the importance of thiolate ligand type in influencing the NC bonding properties.