Nitrogen-doped fluorescent carbon dots for highly sensitive and selective detection of tannic acid

Herein, a facile approach for highly sensitive and selective detection of tannic acid (TA) was proposed with the nitrogen-doped fluorescent carbon dots (NCDs) as a novel fluorescent probe, using sodium citrate and aminopyrazine as precursors. The as-synthesized NCDs exhibited multiple advantages including high quantum yield (11.8%), good water solubility and satisfactory stability. In addition, the NCDs displayed excitation-independent emission behavior with fluorescence emission peak remaining at 389 nm under excitation of 270-350 nm. Significantly, the fluorescence quenching of as-fabricated NCDs was observed with the increasing TA concentration, and the calibration curve displayed a wide linear region ranging from 0.40 to 9.0 μmol L^-1 with a detection limit of 0.12 μmol L^-1. This fluorescent probe also performed well in determining TA in beer samples with average recoveries of TA ranging from 96.1% to 104.4% and the relative standard deviation less than 5%, which provided a reliable, rapid and simple method to determine TA in real samples. Thus, this method offered a valuable insight for its practical applications.