A ratiometric fluorescence sensor based on starch/polyacrylamide/deep eutectic solvent hydrogel for visual and nondestructive detection of methyl parathion on foods.

The abuse of organophosphorus pesticides, such as methyl parathion (MP), often leads to environmental pollution and food safety issues. It is necessary to establish a rapid and non-destructive method for MP detection. Herein, a starch-based ratiometric fluorescence hydrogel was constructed by introducing carbon quantum dots and Eu3+ as the detection and background fluorescence source, respectively. The starch-based hydrogel exhibited good mechanical performances with an elongation of 976% and a compression ratio of 70%, being validated by microscopic characterizations and density functional theory (DFT) calculations. Moreover, the high adsorption energy (-65.3 kcal/mol) obtained from DFT between the hydrogel and MP proved its high selectivity for MP. The visual sensor had a limit of detection of 0.4 μM, good sensitivity, stability and reusability for MP detection. This study provides a visual and nondestructive detection approach for determination of pesticide residues and guides intelligent application of fluorescent hydrogel-sensors.