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

ABSTRACT 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.