Synthesis of AuCu Nanoclusters with Isomeric Mercaptobenzoic Acid Ligands.

Au-based alloy nanoclusters (NCs) have attracted significant interest due to their unique properties, including chirality, magnetism, luminescence, and size-dependent characteristics. Despite their promising potential, further efforts are required to explore a broader range of ligands and alloy NCs to fully unlock their capabilities. Here, [AuCu(MBA)] alloy NCs (MBA = mercaptobenzoic acid) were synthesized from [Au(MBA)] seed NCs using MBA isomers as etching agents. The [Au(MBA)] NCs were fragmented and reassembled with Cu ions into [AuCu(MBA)] NCs. This process, driven by MBA ligands, was monitored by time-dependent electrospray ionization mass spectrometry and optical spectroscopies. Theoretical calculations suggested a tetrahedral geometry for the [AuCu(MBA)] NCs stabilized by interligand interactions. Notably, the quantum yield of [AuCu(-MBA)] NCs increased ∼14-fold compared to that of [Au(-MBA)] NCs. These results offer a novel approach for synthesizing water-soluble, size-focused Au-based alloy NCs, opening up the investigation of new gold alloy clusters with enhanced properties and broader applications.