Abstract

Designing superior probes to detect trace amounts of picric acid (PA) is of huge importance for homeland security and environmental protection. In this study, a simple and rapid fluorescent sensor was developed for the highly selective and sensitive detection of PA in aqueous solution using cysteine stabilized copper nanoclusters (Cys-CuNCs) as a probe. The synthesized Cys-CuNCs were characterized by UV-visible, fluorescence, Fourier-transform infrared spectroscopy (FT-IR), high resolution transmission electron microscopy (HR-TEM), zeta potential and fluorescence lifetime measurements. The HR-TEM image shows that the Cys-CuNCs were spherical in shape with an average diameter of 2.2 nm. The prepared Cys-CuNCs were green luminescent under UV light and show maximum emission at 494 nm, when excited at 370 nm. The emission intensity of Cys-CuNCs was significantly quenched by the addition of PA, while addition of other nitro compounds induced meagre quenching of Cys-CuNCs, suggesting the high selectivity of Cys-Cys-CuNCs. This drastic change is ascribed to the strong inner filter effect (IFE) and static quenching between PA an Cys-CuNCs. The present sensor system exhibits a good linear response to PA ranging from 2.5 to 25 mu M with a correlation coefficient of 0.9930, and the limit of detection was found to be 0.19 mu M (S/N = 3). In addition, the developed sensing method was successfully applied to determine PA in tap and lake water samples.