A Fluorescent Sensor for Rapid Detection of Three Insecticide Residues Using N, S-Doped Carbon Quantum Dots

Due to the potential risks, pesticide residue analysis has attracted widespread attention. In this study, an “off-on” fluorescence sensor for rapid detection of three target insecticide residues has been developed based on the cascade reaction system caused by acetylcholinesterase/choline oxidase dual enzyme. N and S-doped carbon quantum dots (N, S-CQDs) were used as the fluorescent probe. The substrate acetylcholine chloride was hydrolyzed to choline by acetylcholinesterase. Subsequently, choline oxidase oxidized the resulting choline to betaine and H 2 O 2 , and the generated H 2 O 2 quenched the fluorescence of N, S-CQDs. The selected insecticides inhibited acetylcholinesterase activity, and therefore the sensing system's fluorescence was recovered. The linear ranges for indoxacarb, propamocarb, and fenobucarb were 3.0×10 −3 –8.0×10 −2 mg/L, 2.0×10 −3 –5.5×10 −2 mg/L, and 2.2×10 −3 –6.5×10 −2 mg/L, respectively. The corresponding limits of detection ranged from 2×10 −3 to 3×10 −3 mg/L. For spiked concentrations between 5 µg/L and 0.1 mg/L, the average recoveries of the selected insecticides ranged from 99.6% to105%, with relative standard deviations in the range of 1.2% to 4.8%. The proposed method presents the advantages of simple operation without using requiring specialized apparatus, fast speed, low cost, and environmental friendliness. These benefits make it suitable for rapid detection of the selected insecticide residues in real samples. Graphical In the present study, a fluorescence sensor was developed based on enzyme-mediated cascade reaction on N, S-CQDs. N, S-CQDs in the sensor present excellent fluorescence properties. Three target insecticides can be rapidly detected in real samples with easy operation and cost-effectiveness. The selected insecticides can be detected with the LODs from 2.0 ng/mL to 3.0 ng/mL.