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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 Au13core. Comparison of Au24Pt with the structure of Au25by 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.

With the recent successful synthesis of an increasing number of atomically precise thiolate–gold nanoclusters (NCs), there are growing demands for a better understanding of their atomic structures and structure–property relationships in response to composition change. Herein, we present X-ray experimental results on structural and electronic properties of a recently synthesized gold–thiolate nanocluster, Au19(SR)13, in comparison with the structurally well-known Au25(SR)18reference. The atomic structure of Au19(SR)13was first probed with extended X-ray absorption fine structure (EXAFS). A multishell EXAFS fitting method (consisting of one Au–S and three Au–Au shells) allowed for a detailed structural comparison of the two nanoclusters, which revealed a sizable increase of the bond distances between the surface–surface and surface–staple Au atoms upon the decrease of Au atoms in the nanocluster. X-ray photoemission experiments and ab initio calculations further demonstrated the sensitive change of electronic properties of the nanoclusters when the cluster composition was varied, that is, the Au19(SR)13nanocluster has a differently shaped and positively shifted Au 5d band relative to Au25(SR)18. These experimental findings highlight the sensitivity of the local structure and electronic properties of thiolate-gold nanoclusters to even a small change of the metal core from Au13to Au11.

While recent advances in the synthesis and crystallography of gold–thiolate nanoclusters have led to enormous progress in understanding the structure and bonding of gold thiolate nanomaterials, the changes in structure experienced by these nanomaterials in different conditions, such as low temperature and solvation, is still largely lacking. Herein, we report a temperature- and solvation-dependent extended X-ray absorption fine structure (EXAFS) study of thiolate-protected Au25nanoclusters. The structural changes experienced by Au25in response to low temperature and different solvation environments are illustrated in great detail using a site-specific EXAFS fitting approach consisting of one Au–S and three Au–Au shells. EXAFS simulations as well as ab initio calculations of the local density of states are used to support the EXAFS analysis and correlate the structural characteristics of Au25with its electronic properties. These experimental and theoretical studies point out the existence of the interplay between the “metallic” behavior of the Au13core and the “molecular” behavior of the six RS–Au–S(R)–Au–SR “staple” units within Au25, which may shed light on its catalytic mechanism and aid in the design and synthesis of other gold–thiolate nanoclusters by balancing the metallic and molecular interactions.

Understanding the atomic structure and structure−property relationship of Au−thiolate clusters is essential for advancing their fundamental studies and applications. However, a precise determination of the solution-phase structure and bonding of these clusters, albeit of its paramount importance in synthesis, processing, and applications, is still lacking. We report here solution-phase X-ray absorption spectroscopy (XAS) studies of thiolate-protected Au38nanoclusters. A significant bond expansion associated with an increase of Au d-electron density of states (DOS) has been observed upon solvation of Au38in toluene. These findings are accounted for by projected DOS calculations, which further illustrate the unique electronic behavior of Au38from a site-specific perspective. The impact of these findings on tuning the properties of Au−thiolate clusters is also discussed.