Fluorescent Detection of Fenitrothion Combined with Portable Smartphone-Integrated Hydrogel Platform Based on Arg/MTU-AuNCs

Fenitrothion (FTN), a widely used organophosphorus pesticide, raises significant concerns for food safety and environmental health, creating a demand for sensitive and rapid detection methods. In this study, as the first attempt, a red-emitting gold nanocluster (Arg/MTU-AuNCs) was synthesized for FTN detection. The introduction of arginine (Arg) and 4-hydroxy-2-mercapto-6-methylpyrimidine (MTU) significantly improves the fluorescence properties of AuNCs via Au-S and hydrogen bonds. After the addition of FTN, the fluorescence intensity of Arg/MTU-AuNCs varies with FTN concentration due to the static quenching, thus enabling its sensitive detection. The probe exhibits a linear detection range for FTN of 2.00-90.00   μg/L and a limit of detection of 0.72   μg/L. Furthermore, the probe exhibits high selectivity against common interfering substances (e.g., metal ions, anions, and coexisting pesticides). When used for analysis of real samples including tea, mulberry leaves, and oranges, the method achieves recoveries ranged from 90.50% to 108.67%. In addition, a fluorescent hydrogel sensing platform was constructed by combining the probe with agarose hydrogel, and portable detection of FTN was realized through a smartphone. This work offers an effective and portable approach for rapid FTN monitoring, with significant potential for food safety and environmental applications.