The Sensitive Turn-On Fluorescence Detection of Ascorbic Acid Based on Iron(III)-Modulated Nitrogen-Doped Graphene Quantum Dots.

A rapid, selective and sensitive sensor based on the Fe(III) modulated nitrogen-doped graphene quantum dots (N-GQDs) was developed and applied as fluorescence sensor for ascorbic acid (AA) detection. The N-GQDs was one-step synthesized in an easy and green way using citric acid as the carbon source and urea as nitrogen source. The sensor was based on the different quenching effects of Fe(III) and Fe(II) on the fluorescence intensity of N-GQDs. The fluorescence of N-GQDs was quenched by Fe(III) via the strong selective coordination interaction between them. In the presence of AA, Fe(III) can be transformed to Fe(II) ascribed to the oxidation-reduction reaction, leading to the recovery of fluorescence. On the basis of this principle, a fluorescence sensor for AA detection was constructed. Under optimal conditions, the method showed a response to AA within a concentration range of 1.0-90 μmol L(-1) with a good linear relationship and the detection limit for AA was 18 nmol L(-1). The developed sensor was successfully applied for the determination of AA in beverage samples with quantitative recoveries from 95.3 % to 104.3 %.