Congcong Wang, Chang Liu, Rulin Jia, Hongda Li, Rui Zhang
With the development of agricultural industrialization, compound sodium nitrophenolate (CSN), a broadly used plant growth regulator, is prone to excessive residues in agricultural products arising from overapplication or improper usage. Thus, the preparation of high-efficiency fluorescent sensing systems for fast and precise detection of CSN is extremely meaningful for safeguarding the quality and safety of agricultural commodities. In this research, N,S-doped carbon quantum dots (N,S-CQDs) featuring with green fluorescence emission were successfully synthesized by means of microwave-assisted carbonization. The morphology, crystal structure, and functional group information for the as-prepared N,S-CQDs were systematically characterized. These obtained characterization results indicated that the prepared N,S-CQDs showed a regular sphere shape with the mean diameter of 2.41 nm. Optical property investigations revealed that the N,S-CQDs displayed a maximum emission peak at 520 nm under the excitation of 425 nm, accompanied by a quantum yield of fluorescence of 26.17%. Furthermore, the N,S-CQDs demonstrated excellent optical stability and remarkable resistance to salt interference. Under optimized detection conditions, the N,S-CQDs probe displayed a highly selective fluorescence quenching response toward CSN. Simultaneously, good linear dependence relations were also collected within the concentration ranges of 6-120 μmol/L and 120-360 μmol/L, with a low detection limit value of 0.24 μmol/L. Mechanistic studies on the fluorescence quenching behavior suggested that obvious quenching process was primarily dominated by the combined effect of three factors. Validation experiments conducted on simulated samples and real lettuce samples confirmed that the proposed method could effectively detect CSN residues in actual agricultural samples, manifesting promising application potential.