Rapid determination of organophosphorus insecticides residue in fruit juice by a fluorescence sensor based on carbon quantum dots

Nitrogen doped carbon quantum dots (N-CQDs) were synthesized by a hydrothermal method. A fluorescence sensor for rapid determination of organophosphorus pesticides residue was developed using the N-CQDs based on acetylcholine enzyme inhibition. Cu²⁺ effectively quenched the strong fluorescence of N-CQDs, which could be recovered due to the complexation between copper ions and thiocholine, the hydrolysis product of acetylthiocholine catalyzed by acetylcholinesterase. Organophosphorus pesticides inhibited the activity of acetylcholinesterase, resulting in fluorescence quenching of N-CQDs. Fluorescence inhibiting efficiency depends on the concentration of the analytes, and therefore, the sensor could be used for quantitative analysis of organophosphorus pesticides residue. The average recoveries of the analytes ranged from 85.33 % to 110.67 % at the spiked concentrations of 0.015 mg/L, 0.04 mg/L and 0.1 mg/L, and the limits of detection were 2.89 ∼6.40 ng/mL. The developed method had the advantages of simple operation, fast speed, low cost, expensive apparatus-free, and environmental friendliness, which could be used for rapid screening of organophosphorus pesticides residue in real samples.