Highly sensitive and selective sensing of lead (II) ions in Paris polyphylla using fluorescence-enhanced sulfur quantum dots in deep eutectic solvent micelles.

Heavy metal residues in Chinese herbal medicines (CHMs) have raised significant concerns due to their inherent toxicological implications for human health. Therefore, there is an imperative requirement to establish an effective and sensitive method for detecting heavy metal ions. In this study, sulfur quantum dots (SQDs) were fabricated through a sonication-assisted HO etching approach, and the spectral characteristics of SQDs in deep eutectic solvent (DES) micelles were studied. This study found that SQDs significantly aggregate in the long alkyl chains of surfactant-like DES, thereby enhancing the luminescent intensity of SQDs. A fluorescent probe that acts as a "turn-off" was developed using DES-sensitized SQDs to determine Pb. The detection mechanism of this probe for Pb was further analyzed. Under optimized experimental conditions, the linear range of Pb concentrations was determined to be 20-100 μM, with a detection limit of 1.61 μM. Validation studies of the method demonstrated that the sensitivity of the established sensor was 1.7-fold greater than that of the bare SQDs probe. Furthermore, the established method was verified using Pb in Paris polyphylla as the research subject, yielding a satisfactory recovery rate. In short, the DES-sensitized SQDs fluorescent platform is a sensitive, simple, and effective method for detecting Pb in complex samples.