Understanding thiol-induced etching of luminescent gold nanoclusters

Abstract

This study reported that lysozyme Type VI (Lys VI)-stabilized Au₈ clusters serve as a model to probe how distinct types of alkanethiol ligands affect the core etching of AuNCs. By monitoring the fluorescence of Au₈ clusters, we determined that thioglycolic acid (TGA)-induced core etching of Au₈ clusters was substantially faster at pH 9.0 than it was at pH 3.0. This can be attributed to more efficient electron injection from TGA to Au₈ clusters at pH 9.0, facilitating the core etching of Au₈ clusters. Because long-chain mercaptoalkanoic acids attached to Au₈ clusters are considerably disordered and exhibit a high density of gauche defects, the ability of mercaptoalkanoic acid to etch Au₈ clusters increased when the alkyl chain length was decreased. The thiol analogs exhibited the following trend in the core etching of Au₈ clusters at pH 9.0: TGA > 2-mercaptoethanol > 1-octanethiol. These results indicate that the carboxyl group of ligand is a key element for the core etching of Au₈ clusters. We also disclosed that Au₈ clusters can protect Lys VI activity against denaturation and act as a fluorescent probe to detect thimerosal in vaccines.