Interestingly, the glutathione capped Au-nanoclusters presented here showed a unique optical performance compared with their homological AuNPs with larger size. The luminescence intensity of the AuNCs could be enhanced due to the formation of aggregates. The AuNCs were then employed as a visual probe for the detection of Pb2+ based on the aggregation-induced emission enhancement (AIEE) property of the AuNCs. When the luminous glutathione capped AuNCs probes encountered Pb2+ ions, they rapidly formed aggregates through GSH–Pb2+ interaction in 1 minute, resulting in an enhanced luminescence intensity. The enhanced luminescence intensities showed a linear dependence on the concentrations of Pb2+ with satisfactory selectivity towards 12 kinds of divalent metal ions. More importantly, the probe can also be used for on-site testing to inspect Pb2+ contamination by using a portable UV flashlight.
