Fluorescence turn-on and turn-off sensing of pesticides by carbon dot-based sensor

This paper describes a simple fluorescence-based method using carbon dots (C-Dots) with a green chemistry synthesis method for the detection of commonly used pesticides, such as atrazine, chlorpyrifos, imidacloprid, lindane, and tetradifon in aqueous solution. The C-Dots are synthesized from gelatin using a hydrothermal route and have amine, carboxyl, and hydroxyl groups on the surface. Because of these functionalities, the C-Dots are directly coordinated to the highly reactive -NO2 and -NH groups of imidacloprid with a high binding affinity (3.24 x 10(6)) and selectivity, which switches the C-Dots to the more isolated state than its initial non-isolated state resulting in an enhancement of the C-Dots' fluorescence (turn-on). In contrast, to the other four pesticides, the fluorescence of the C-Dots gets quenched (turn-off). The pesticide-C-Dot interactions are mainly a static type via a ground state non-fluorescent complex formation with an insignificant contribution from the diffusion controlled electron transfer reaction. The as-fabricated C-Dots display different binding characteristics with the different pesticides which are helpful in distinguishing the target pesticides with very low detection limits of 0.013 mu M for imidacloprid and 0.04 mu M for tetradifon which are comparable to the previously reported values. The results of time-resolved fluorescence lifetime and anisotropy experiments support the results. In addition, the electrochemical detection approach confirmed the findings. The recovery efficiency of 92-97%, in real river water suggested that the fabricated nanoprobe would be a good, useable sensor in practical applications. Thus, the current investigation is helpful for designing a new, easy, eco-friendly, and efficient sensing method for pesticide monitoring.