Preparation of carbon quantum dot fluorescent probe from Caesalpinia sappan L. for the detection of ciprofloxacin and antibacterial applications

This study demonstrates a one-step hydrothermal synthesis of bright yellow phosphorus-doped carbon quantum dots (P-CQDs) using Caesalpinia sappan L. as carbon source. Comprehensive characterization through TEM, XPS, UV-Vis and FTIRspectroscopy confirmed the successful formation of P-CQDs. The obtained P-CQDs exhibited exceptional selectivity and was capable of detecting ciprofloxacin across a wide linear range of 0.01–0.1 µM, with a LOD determined to be 2.06 nM. Antimicrobial assays revealed MIC values of 7.14 µg/mL and 8.33 µg/mL against S. aureus and E. coli, respectively. Practical application studies confirmed their efficacy for rapid CIP detection in milk samples, establishing a novel sensing platform for food safety monitoring. This work provides valuable insights into the multifunctional applications of carbon dots in food chemistry and biomedical fields.