This work reports a novel one-pot hydrothermal synthesis of N-CQDs using Solanum nigrum L. as sustainable carbon source and triethylamine as nitrogen provider. The resulting N-CQDs were systematically characterized with TEM, SEM, FT-IR, XPS, XRD, and UV–Visible. Significantly, the N-CQDs exhibited substantial antimicrobial efficacy against both S. aureus and E. coli bacterial strains, with minimum inhibitory concentration values of 1.2 mg/mL and 1.1 mg/mL, respectively. Moreover, the N-CQDs demonstrated pronounced fluorescence enhancement upon interaction with ciprofloxacin, displaying exceptional selectivity and sensitivity, with a calculated LOD of 316 nM. The feasibility of employing N-CQDs as fluorescent probes for ciprofloxacin detection was systematically validated through practical application in honey analysis. This study introduces a novel approach for the fabrication of N-CQDs derived from natural botanical sources, underscoring their potential dual functionality as fluorescent sensors and antimicrobial materials.

In this study, S-CQDs were fabricated through a green and secure hydrothermal process, the carbon source was derived from the traditional Chinese medicinal herb Solanum nigrum and thiourea served as the sulfur precursor.