Scalable and Precise Synthesis of Thiolated Au_10–12, Au₁₅, Au₁₈, and Au₂₅ Nanoclusters via pH Controlled CO Reduction

Abstract

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 (Au 10–12, Au 15, Au 18, and Au 25 ) 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 Au 18 (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 (Au 10–12, Au 15, and Au 18 ) in large quantities that are not available in the current NC synthesis due to the lack of direct and scalable synthetic protocols.