Single-probe cascade determination of multiple analytes by a tandem reaction of copper nanoclusters

A new type of red-emitting copper nanoclusters (Cu NCs) was synthesized and applied to the sequential detection of multiple analytes. Remarkably, a fluorescent and colorimetric dual-mode response was achieved via a tandem reaction of the Cu NCs with hyperoxide and carboxylic acid. As a fluorescent probe, the Cu NCs were first oxidized by hyperoxide, resulting in prominent fluorescence quenching with a low detection limit (0.4 µM). Subsequently, the oxidized Cu NCs could clearly distinguish the carboxylic acid through a color change in the solution. An excellent linear relation was established between the fluorescence/absorbance intensity and the corresponding hyperoxide/formic acid concentrations. The mechanisms of fluorescence quenching and colorimetric response were investigated. Leveraging this tandem reactivity, the Cu NCs were successfully employed to identify the different oxidation degrees of 1,4-dioxane. This work provides a new strategy for the cascade detection of multiple analytes by single metal nanoclusters.