Scalable and precise synthesis of thiolated Au10-12, Au 15, 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 (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 Au 18) in large quantities that are not available in the current NC synthesis due to the lack of direct and scalable synthetic protocols. © 2013 American Chemical Society.