X-ray Spectroscopic Studies of Gold-thiolate Nanoclusters

Abstract

Structural characterization of nanomaterials represents one of the largest challenges in modern nanoscience. Recent advances in the synthesis and crystallography of gold-thiolate nanoclusters have led to enormous progress in understanding the properties of these materials, however, many questions still exist about how the structure and bonding of these nanoclusters vary with cluster size, composition and material phase. The precisely defined size and composition of gold-thiolate nanoclusters offers a great opportunity to systematically illustrate the structure and bonding of these materials from an atomic-site-specific perspective. Towards this end, X-ray absorption and photoemission spectroscopies were employed in the study of compositionally precise gold-thiolate nanoclusters. First, a high-precision, site-specific illustration of the bonding in a 144 Au atom nanocluster is presented. Following this, a comparison of the structure of a 38 Au atom nanocluster in the solid state and solution-phase is presented and discussed in terms of local structural and electronic effects. Finally, the structural changes experienced by a 25 Au atom nanocluster in response to temperature and solvation are observed from a site-specific perspective. In addition, size-specific bonding trends for these clusters are presented from both the sulfur and gold perspectives. This work represents the first X-ray absorption spectroscopy study of compositionally precise gold-thiolate nanomaterials. These studies help to develop a thorough picture of the bonding properties of gold thiolate nanoclusters, and have potential implications for the development and application of gold-thiolate nanomaterials.