Nitrogen‐Doped Carbon Quantum Dots for Tannic Acid Analysis in Complex Food Matrices

The rapid, sensitive, and cost‐effective detection of tannic acid (TA) in complex food matrices is essential for improving food safety standards. To meet this demand, nitrogen‐doped carbon quantum dots (N‐CDs) were prepared using a one‐pot hydrothermal reaction using L‐malic acid, citric acid, and tris(2‐aminoethyl) amine as precursors. The excitation wavelength of the N‐CDs was 430 nm, and the emission wavelength was 490 nm. Transmission electron microscopy (TEM), atomic force microscopy (AFM), X‐ray photoelectron spectroscopy (XPS), Fourier transform infrared (FT‐IR) spectroscopy, and X‐ray diffraction (XRD) were used to characterize the prepared N‐CDs, and the results revealed a uniform morphology and a nitrogen‐rich surface structure. In addition, we found that the N‐CDs exhibited excellent selectivity for TA, primarily attributed to the fluorescence quenching effect of TA on the N‐CDs. Therefore, a fluorescent sensor for TA detection was constructed based on the N‐CDs, with a linear detection range of 0.500‐250 µM ( R 2 = 0.99987) and a detection limit of 0.15 µM ( S/N = 3). The practical applicability of the sensor was demonstrated by analyzing TA in beer, red wine, and apple juice, achieving recoveries ranging from 101% to 116% and RSDs between 3.0% and 5.4%. The fluorescence assay results were closely related to the HPLC‐DAD validation results, highlighting the accuracy of the method. The N‐CDs‐based detection platform offers the advantages of simplicity, sensitivity, and reliability, providing a promising tool for routine TA monitoring in food safety applications.