Iron Ion‐Mediated Nitrogen‐Doped Carbon Dot Fluorescence Sensing for Accurate Detection of Fluoroquinolone in Food

Safety incidents involving the presence of fluoroquinolones (FQs) residues in animal‐derived food are frequently reported, posing a significant threat to human health. Here, we constructed a fluorescence sensing method using iron ions as a bridge for the detection of FQs in food. Iron ions significantly weakened the fluorescence intensity of N‐CDs by forming a non‐fluorescent substance through coordination with C = N on N‐CDs, which caused a static burst by the electron transfer effect (ET), and the fluorescence changed from “on” to “off.” Since the FQs have a strong chelating effect with Fe 3+ , the quenched fluorescence is restored by the competitive binding of FQs with Fe 3+ , which results the fluorescence was “on.” The detection of FQs was achieved by the change of fluorescence intensity, for which the limit of detection (LOD) was 4.40 µmol/L. Compared with existing methods, the proposed method has a wider linear range of 5–900 µmol/L. For real samples including tap water, milk, and honey, the recoveries of FQs determination ranged from 91.31% to 107.50%. These results indicate that the fluorescence detection method constructed in this study offers a novel strategy for detecting FQs residues in real samples.