Pyrene functionalized organic cation receptor-based "turn-on" fluorescence approach for monitoring of chlorpyrifos in food, soil, and water samples

Background: The unregulated use of pesticides by farmers, for crop productivity results in widespread contamination of organophosphates in real environmental samples, which is a growing societal concern about their potential health effects. The conventional approaches for the monitoring these organophosphate-based pesticides which include immunoassays, electrochemical methods, immunosensors, various chromatography techniques, along with some spectroscopic methods, are either costly, sophisticated, or involves the use of different metal complexes. Therefore, there is an urgent need for sensitive, quick, and easy-to-use detection techniques for the screening of widely used organophosphate-based pesticides.

Results: Herein, we demonstrates the metal-free detection of CPF pesticide in aqueous medium, based on the organic nanoparticles of benzimidazole-based cationic receptor (R1-ONPs), and thoroughly analyzed using advanced techniques such as AFM, FESEM, and DLS etc. The photophysical investigations revealed that developed R1-ONPs exhibited high selectivity towards chlorpyrifos with an enhancement in fluorescence emission. Further, the observed pyrene excimer-based "turn-on" fluorescence mechanism, and the interaction between developed sensor and chlorpyrifos has been validated utilizing ¹H, and ³¹P NMR spectroscopy. The developed sensor can effectively quantify chlorpyrifos up to a detection limit of 18.9 nM (3σ method) with a range of 0-120 μM as well as below the cutoff limit set by FAO. Moreover, the real-time application of developed sensor (R1-ONPs) was evaluated to monitor chlorpyrifos in spiked food, water, and soil samples with good (%) recovery.

Significance: The development of metal-free, pyrene-excimer-based "Turn-On" fluorescent sensor offers a novel, eco-friendly strategy for the detection of chlorpyrifos in aqueous medium. Additionally, its ability to quantify the chlorpyrifos at levels as low as those set by FAO makes it more efficient tool for monitoring the environmental toxicity ensuring better protection for human, and animal health.