Preparation of high-quantum-yield fluorescent carbon dots derived from Paliurus ramosissimus and their dual-functional sensing of erythromycin and Hg2+

In this study, sulfur and nitrogen co-doped fluorescent carbon dots (S,N-CDs) were synthesized via a hydrothermal method using Paliurus ramosissimus as a natural and sustainable carbon source. The as-prepared S,N-CDs exhibited a high quantum yield of 73.3% in ethanol, along with pronounced solvent-dependent and excitation-dependent fluorescence properties. Fluorescence sensing investigations demonstrated that the S,N-CDs possessed excellent selectivity toward erythromycin (EM) and Hg 2+ , with limits of detection of 0.27 μM and 38 nM, respectively. The quenching process was attributed to a static quenching mechanism, and satisfactory anti-interference performance was observed. Furthermore, a smartphone-assisted visual detection strategy was established based on the distinct fluorescence color variation of S,N-CDs in response to different EM concentrations, achieving a detection limit as low as 0.41 μM. Spike-and-recovery experiments revealed recoveries of 87.97%–95.52% in rainwater samples and 100.88%–107.11% in milk samples, with relative standard deviations (RSDs) below 3%, indicating favorable practical applicability. Overall, the developed S,N-CDs fluorescent probe combines high sensitivity, strong selectivity, and environmental friendliness, providing a promising platform for the rapid detection of multiple contaminants in environmental and food matrices and broadening the application scope of plant-derived carbon dots.