Fabrication of Stable and Luminescent Copper Nanocluster-Based AIE Particles and Their Application in β-Galactosidase Activity Assay.

Thiolated copper nanoclusters (CuNCs) with aggregation-induced emission characteristic are becoming a novel luminescent material, but it is still a challenging task to retain its bright luminescence in a neutral solution. In this work, we report a new copper nanocluster with aggregation-induced emission (AIE) enhancement property using a hydrophobic molecule as the protecting ligand, and brightly luminescent AIE particles of copper nanocluster were prepared via hydrophobic interaction. These CuNCs AIE particles possess uniform rod-like shapes, with sizes in hundreds of nanometer, and an intense luminescence; more importantly, its luminescence remains stable in neutral and alkaline solutions. It is found that 4-nitrophenol is able to effectively quench the luminescence of CuNC AIE particles through strong hydrophobic interaction and electron transfer between them. This strong quenching effect was adopted to develop a luminescent assay for β-galactosidase at physiological condition. This work presents a demonstration of preparing CuNC AIE particles with bright luminescence at neutral condition and gives an example of the use of AIE particles in monitoring the enzyme activity.