Strongly fluorescent cysteamine-coated copper nanoclusters as a fluorescent probe for determination of picric acid.

This paper describes the synthesis of fluorescent copper nanoclusters (CuNC) with a fluorescence quantum yield as high as 2.3% after modification with cysteamine. The modified CuNC are shown to be viable probes for the determination of picric acid (PA). Fluorescence drops with increasing concentration of PA which can be detected fluorometrically with a 0.14 μM limit of detection. This is much lower than required by the People's Republic of China Surface Water Environmental Quality Standard (2.2 μM). The probe was successfully applied to the determination of PA in spiked tap water, lake water and river water. Graphical abstract Copper nanoclusters (CuNC) have weak fluorescence but after the modification with cysteamine, the fluorescence of CuNC is strongly enhanced. The fluorescence of such cysteamine-coated copper nanoclusters (CuNC-CA) is reduced upon the addition of picric acid (PA) through an inner filter effect (IFE).