A facile synthesis of water-soluble carbon dots as a label-free fluorescent probe for rapid, selective and sensitive detection of picric acid

In this work, novel water-soluble and blue fluorescent carbon dots (C-dots) were synthesized using one-pot hydrothermal method with malonic acid and urea, and were then used as a label-free fluorescent probe for selective, sensitive, and rapid determination of picric acid (PA). The sizes of the as-prepared C-dots were mainly distributed in the range of 1.5–3.0   nm with an average diameter of 2.5   nm. Moreover, the C-dots displayed blue fluorescence with an emission peak at 395   nm (320   nm excitation), which also showed good stability and anti-photobleaching ability. Interestingly, the fluorescence of C-dots could be selectively quenched by PA within 10   s. Based on this phenomenon, a label-free fluorescence assay was proposed for specific determination of PA. The fluorescence intensity of probe showed a linear response to PA in the concentration range of 0.1 to 26.5   μM with a low detection limit of 51   nM (S/N   =   3). Finally, the resultant fluorescent probe was successfully applied to the detection of PA in real water samples.