A copper nanocluster incorporated nanogel: Confinement-assisted emission enhancement for zinc ion detection in living cells

In this work, copper nanoclusters (CuNCs), in which cysteine served as both a reducing agent and a protection ligand, were synthesized, and impregnated into a nanogel of glycol chitosan (GC), forming a CuNCs@GC nanocomposite. The stability of CuNCs incorporated into a nanogel was significantly improved, while their photoluminescence (PL) intensity of CuNCs@GC could be tuned by controlling the pH of the system. The nanocomposite was used as a platform for the "turn on" detection of Zn2+, making use of the effect of aggregation induced emission (AIE) enhancement. By adjusting the pH of the system to 7.4, the PL of CuNCs@GC was turned down so as to minimize the background signal. In the presence of Zn2+, the nanoclusters in CuNCs@GC changed from the dispersed state to the aggregated state, which resulted in an increase of the PL intensity. A linear response between the PL intensity and the concentration of Zn2+, in the range from 1.5 mu M to 750 mu M, was obtained, achieving a detection limit of 1.0 mu M. Furthermore, the CuNCs@GC nanocomposite was found to be applicable to live cell imaging, owing to the high biocompatibility and protective effects of GC.