Controlling Aggregation-Induced Emission in Bimetallic Gold-Copper Nanoclusters via Surface Motif Engineering

Aggregation-induced emission (AIE) has been significantly explored to enhance luminescence properties. Here, we synthesized bimetallic AuCu nanoclusters (NCs) and studied their AIE by reconstructing the surface motif from -SAu(I)S Au(I)S to -SAu(I)SCu(I)S, as evident from X-ray photoelectron spectroscopy (XPS) and microscopy studies. A significant blue shift in the emission band of Au NCs is observed with the change of the Au/Cu molar ratio. We observed enormous emission enhancement with decreasing temperature due to suppression of the intramolecular motion of surface ligands. A 200-fold emission enhancement occurs due to the aggregation of ultrasmall-sized AuCu NCs in a less polar medium of the waterethanol mixture. An increase in the radiative rate supports the effect of the Au(I)Cu(I) metallophilic interaction. A decrease in the nonradiative rate confirms the restriction of ligand motions in the aggregated state. Metal cluster-based AIE-type materials pave the way to design highly luminescent materials for potential applications in sensing, biolabeling, light-emitting diodes (LEDs), and other fields.