Synthesis of fluorescein modified carbon quantum dots and application of dual emission ratio fluorescent probes for highly selective detection of chlorothalonil

Chlorothalonil (CHT) is a class 2B carcinogen that is capable of remaining in the environment for long periods, has an obvious bioconcentration phenomenon, and may pollute groundwater, thus it is essential to construct a simple detection method for chlorothalonil. However, common single emission fluorescent probes or dual emission fluorescent probes constructed from multi-component mixtures have low selectivity and anti-interference ability. In this work, a simple two-step hydrothermal method was used to synthesize fluorescein-modified carbon quantum dots (F-CQDs), and a dual-emission fluorescent probe was constructed to detect chlorothalonil concentration. The study found that in the presence of a certain amount of Fe 2+ , the fluorescence intensity of the fluorescence emission peaks of F-CQDs located at 435 nm and 508 nm gradually decreased with the increase of CHT concentration within 2 min. This fluorescent probe has specific recognition for CHT and shows a significant linear relationship in the range of 0.1664–3.0695 μM, with a detection limit as low as 8.6 × 10 −3  μM. The probe was successfully applied to the detection of CHT residual content in environmental water with a satisfactory average recovery, and the present study provides a new method for the preparation of dual-emission fluorescent probes and the detection of organic pesticides and shows great potential in environmental monitoring.