Hydrogen-bonding network promoted fluorescence in chiral lysine-based carbon dots for ultrasensitive detection of tannic acid in food.

The detection of tannic acid (TA) is essential for evaluating the flavor quality of food and beverages, while excessive intake may lead to health issues such as abdominal pain and diarrhea. In this work, chiral carbon dots (CDs) were synthesized via an electrochemical method using chiral lysine as a precursor. The as-prepared L-Lys-CDs can be served as an efficient fluorescent probe for accurate TA detection, demonstrating high sensitivity, excellent selectivity, a wide linear range (5-75 μg/mL), and a low detection limit (2.61 μg/mL). Practical application in real food samples (red wine, black tea, or apple juice) achieved satisfactory recoveries of 93.3-106.3%. Furthermore, mechanistic studies reveal that the remarkable fluorescence enhancement of L-Lysine-based CDs originates from an extensive surface hydrogen-bonding network, which enhances the rigidity of surface polymer chains and promotes radiative relaxation. This work not only presents a robust sensor but also offers novel insights into the chirality-fluorescence relationship in CDs.