Detection of silver through amplified quenching of fluorescence from polyvinyl pyrrolidone–stabilized copper nanoclusters

Silver ion detection with ultra-high sensitivity was established. We synthesized copper nanoclusters (CuNCs) with blue fluorescence through a one-pot process. Instead of a direct quencher toward the CuNCs, silver ions activated the strong oxidation from persulfate and subsequently converted divalent manganese ion into manganese dioxide (MnO 2 ). The surface charges of MnO 2 and the CuNCs brought them together and quenched the fluorescence from the latter. Due to silver ions’ role as the catalyst in the process, it cycled and even a small amount leads to a significant fluorescence change. This signaling provided the determination of silver ions in the range 5 pM~1 nM, with a detection limit of 1.2 pM. The method is selective, and its applicability was validated through practical water sample analyses. Graphical abstract