Enhancing stability through ligand-shell engineering: A case study with Au25(SR)18 nanoclusters

While thiolate-protected Au nanoclusters (NCs) have drawn considerable interest in various fields, their poor stability in aqueous solution remains a major hurdle for practical applications. Here, we report a unique strategy based on ligand-shell engineering to improve the stability of thiolated Au NCs in solution. By employing two thiol-terminated ligands having oppositely charged functional groups on the surface of the NCs, we demonstrate that the electrostatic attraction between the oppositely charged functional groups of neighboring ligands could amplify the coordination among surface ligands, leading to the formation of pseudo-cage-like structures on the NC surface that could offer higher protection to the Au core in aqueous solution. The strategy developed in this study could be extended to other metal NCs, further paving the way toward practical applications.