A ratiometric fluorescence probe based on dual quantum dots for methyl parathion detection in agricultural products

Methyl parathion (MP) is an organic phosphorus pesticide widely used for pest control of various crops, however, the residual MP can enter the human body and damage the nervous system. Therefore, it is necessary to effectively monitor MP residues. Based on dual-fluorescent quantum dots, this study establishes a ratio fluorescence sensing platform for MP detection, wherein the probe is β-cyclodextrin (β-CD) modified molybdenum disulfide quantum dots (MoS2 QDs) called β-CD-MoS2 QDs. Under alkaline conditions, MP is hydrolyzed into p-nitrophenol (p-NP) and enters the hydrophobic cavity of β-CD, quenching the blue fluorescence of MoS2 QDs whose quenching degree of fluorescence intensity (I400) correlates with the concentration of MP, while the fluorescence intensity (I540) of gQDs remains unchanged and is selected as reference signal. The quantitative detection of MP is conducted by calculating the ratio of fluorescence intensities (I540/I400). The probe detected MP in the range of 0.05–25 ppm with a detection limit of 0.032 ppm which is proved to meet the requirements for biological sample detection according to the methodological validation results. The probe has been successfully applied for the detection of MP in apples and vegetables, confirming its applicability for MP detection in crops.