Fluorescence turn off azastilbene sensor for detection of pesticides in vegetables: An experimental and computational investigation

Abstract

Pesticides are detected in agricultural commodities and the environment as a result of indiscriminate pesticide application. To detect the pesticides in real-time and with reasonable accuracy, several technologies are being used hand in hand. This paper describes a technique based on the fluorescence property of an azastilbene derivative, for the detection of some common pesticides, namely, acetamiprid, imidacloprid, dimethoate, edifenphos, λ-cyhalothrin, and quinalphos. The azastilbene derivative exhibited pesticide concentration-dependent fluorescence quenching (turn off) linearity in the range of 0 to 0.15 mM with micromolar range (∼2µM) limit of detection. The quenching efficiency was highest for quinalphos (Stern Volmer quenching constant, 2.5x103 L mol−1). The most stable pesticide-fluorophore complex was also formed by quinalphos, corroborated by favorable molecular docking-based binding affinity and Density Functional Theory (DFT) calculations. The turn-off sensor was also employed for the detection of quinalphos in cabbage samples and was found to be quite efficient when compared with the validation method. The outcomes of the present study, augmented by molecular modeling and quantum mechanical calculations provide an insight into the ground state and excited state chemistry of pesticide-fluorophore complexes. Moreover, in a nutshell, the current study will aid in the development of a simple and effective sensor for detecting pesticides in agricultural commodities and the environment.