Highly sensitive and visual detection of methyl parathion based on ratiometric fluorescent probe using triple-excitation B, N co-doped carbon dots by means of the internal filter effect

The extensive use of methyl parathion (MP) has resulted in both immediate and long-term health hazards to humans. Therefore, developing a practical and efficient on-site detection system for MP is essential. In this study, o -phenylenediamine and 4-vinylphenylboronic acid are used as precursors for synthesis of triple excitation boron and nitrogen co-doped carbon dots (B, N-CDs) utilizing a one-step solvothermal process. Significantly, MP hydrolyzes to p-nitrophenol in a highly alkaline environment, and the absorption bands of this compound partially coincide with the excitation spectra of B, N-CDs. Three excitation peaks show different responses to MP: the two shorter-wavelength excitation peaks are significantly quenched, while the longer-wavelength excitation shows minimal quenching. This phenomenon facilitates the development of a ratiometric fluorescence sensor utilizing the internal filter effect (IFE) targeting sensitive MP detection. The sensor has a low limit of detection (LOD) of 74 nM and a wide linear response spanning 0.074 to 100 μM, indicating its potential applicability in food monitoring. Moreover, a visual detection platform incorporating lateral flow assay strips technology is employed for MP analysis in fruits and vegetables. The system maintains relative standard deviations (RSDs) below 2.32 % while achieving satisfactory recovery rates ranging from 98.1 % to 103.3 %. Thus, this study offers a novel effective strategy for on-site MP detection in the food-related environment.