Solvent- and Cation-Controlled Aggregation-Induced Emission of Thiolate-Protected Cu Nanoclusters

Aggregation-induced emission (AIE) is an intriguing approach to address the low quantum yield (QY) of metal nanoclusters (MNCs). In this work, solvent- and cation-induced aggregation of Cu NCs were investigated. The TEM, MALDI, and TGA analyses confirmed the formation of spherical MNCs with the composition Cu 9 MBA 6 (where MBA = 4-mercaptobenzoic acid). The synthesized Cu NCs exhibited a featureless absorption spectrum, a broad emission at 640 nm, and a QY of 0.20%. These synthesized Cu NCs were treated with Zn 2+, and an extended sheet-like structure was observed in TEM and SEM images. The emission was enhanced up to 14 times compared to pure Cu NCs, with a small blue shift (620 nm). An ordered network-like structure was obtained when it was treated with EtOH, with 15 times PL enhancement and a red shift (650 nm). Here, we propose that Zn 2+ -induced emission involves the electrostatic interaction between the surface ligand of the NCs and the incoming cation. However, the solvent-induced aggregation involved the directional intercluster Cu(I)···Cu(I) metallophilic interaction. This investigation supports the idea of using solvents and cations that provide sheet- and network-like structures upon aggregation, respectively. This study provides a mechanistic understanding of two different AIE pathways and gives a new approach to designing luminogen materials for various imaging and LED applications.