One-step ratiometric fluorescence sensing of ascorbic acid in food samples by carbon dots-referenced lanthanide probe

We report a ratiometric fluorescence sensor formed via the self-assembly of the lanthanide ion Eu3+ and blueemitting carbon dots (CDs) for the direct detection of ascorbic acid (AA). The obtained sensor exhibited the characteristic emission of 2,6-pyridinedicarboxylic acid (DPA)-sensitized Eu3+ (Eu?DPA) at 615 nm and the weak emission of CDs at 440 nm under excitation at 283 nm. After the addition of AA, the fluorescence emission of Eu?DPA, which served as the AA recognition site, was significantly quenched, whereas the emission of CDs changed slightly, resulting in a ratiometric fluorescent response toward AA. A wide linear range from 0.5 ?M to 820 ?M was achieved in the detection of AA with an LOD of 60 nM. Moreover, this CDs/Eu?DPA sensor, which displayed excellent sensitivity and selectivity, was successfully applied for the determination of AA in fruits, vegetables and beverage samples, suggesting a great potential for applications in foods.