Scalable and Precise Synthesis of Thiolated Au10–12, Au15, Au18, and Au25 Nanoclusters via pH Controlled CO Reduction

Large-scale production of thiolated Au nanoclusters (NCs) of tunable sizes is pivotal to realizing their practical applications. Here, we present a simple one-pot synthesis method for gram-scale production of various discrete-sized Au NCs (Au10–12, Au15, Au18, and Au25) protected by different thiol ligands. The key design in our method is to use a gaseous reducing agent, carbon monoxide (CO), to support a mild reaction environment for a slow and well-controlled growth of Au NCs. The pH of the reaction solution was further used to fine-tune the reduction kinetics for the NC growth, leading to the formation of various sized Au NCs. The monodispersity of our products was verified by a number of characterization techniques (e.g., UV–vis, electrospray ionization (ESI)-MS, and X-ray photoelectron spectroscopy (XPS)). NMR spectroscopy was also used to investigate the structure of as-synthesized thiolated Au NCs, which suggested that Au18(SG)14 NCs adopt a core–shell structure with two binding modes of the thiol ligands. The synthetic strategy developed in this study produced three small thiolated Au NCs (Au10–12, Au15, and Au18) in large quantities that are not available in the current NC synthesis due to the lack of direct and scalable synthetic protocols.