Colorimetric based on-site sensing strategies for the rapid detection of pesticides in agricultural foods: New horizons, perspectives, and challenges

Agricultural food crop yields have increased enormously due to the implementation of chemical pesticides; however, their excessive and uncontrolled use has led to food contamination, as well as environmental, aquatic, and agricultural pollution. Therefore, on-site monitoring of pesticide residues in agricultural food products is crucial to ensure global food and environmental safety. Conventional pesticide detection strategies are time-consuming and unsuitable for on-site or on-field detection of pesticides. Among the current approaches for field detection of pesticides, including colorimetric, non-colorimetric, electrochemical, and optical sensing strategies, colorimetric sensing strategies exhibit the most promising potential for the on-site detection of pesticide residues due to their quick detection, easy fabrication, and high selectivity and sensitivity, in addition to being readable by the naked eye. Nonetheless, although pesticide quantification methods have been extensively described in the literature, only a few studies have conducted on-site pesticide residue analyses. Therefore, this study provides a comprehensive overview of the major advances in colorimetric sensing approaches based on nanoparticle aggregation, label-free hydrogel particles, lateral flow immunoassays (LFAs), integrated digital readers, portable field detection, and paper-based sensors for the on-site detection of pesticide residues in food crops. Moreover, this review also compares the analytical performances of the aforementioned strategies and discusses the new horizons, perspectives, and challenges associated with the development of portable devices. Therefore, we believe that this review provides important insights that might serve as the basis for the fabrication of novel colorimetric sensors with applicability in materials science, environmental science, food science, nanoscience, and biotechnology.