Metolachlor detection in grain using N-doped carbon quantum dots and the intramolecular charge transfer effect

Herein, nitrogen is doped into carbon quantum dots (N-CQDs) using a hydrothermal method for the rapid detection of metolachlor in grain. The morphological features, elemental compositions, and optical properties of the N-CQDs are then analyzed and investigated using transmission electron microscopy, X-ray photoelectron spectroscopy, and fluorescence spectroscopy, respectively. Based on the principle of intramolecular charge transfer, a fluorescent probe is constructed for the rapid detection of metolachlor. Under optimal experimental conditions, the fluorescence intensity change values of the N-CQDs and metolachlor concentration have a good linear relationship when the concentration of metolachlor is in the range of 0.0125-2.5 µg mL${}^{-1}$. An evaluation of the method shows that the method has good selectivity, reproducibility, and stability, with a limit of detection of 1.63 µg kg${}^{-1}$ and a limit of quantification of 3.92 µg kg${}^{-1}$. The spiked recoveries of six real samples are tested using a spiked recovery assay that yielded spiked recoveries in the range of 105.05-87.13%, and their relative standard deviations (n = 3) ranged from 4.62% to 0.61%, indicating that the method can be used for detection in actual samples with good precision and stability. (© 2024 Wiley‐VCH GmbH)