A sensitive sensor based on carbon dots for the determination of Fe³⁺ and ascorbic acid in foods

Iron ions (Fe3+) and ascorbic acid (AA) are of great significance to living organisms. Herein, carbon dots (C-dots)-based "off-on" fluorescent probe was designed for Fe3+ and AA analysis. In presence of Fe3+, the fluorescence of C-dots was immediately quenched, and the quenching mechanism was deduced to be inner filter effect (IFE). The fluorescent C-dot probe shows response to Fe3+ in range of 10-500 mu M with a limit of detection (LOD) of 0.9 mu M. Interestingly, when AA was introduced to the C-dots-Fe3+ system, the fluorescence of C-dots was significantly recovered, which could be ascribed to the oxidation-reduction reaction between Fe3+ and AA. Based "off-on" fluorescent C-dots probe, the linear range of 5-500 mu M was obtained with LOD of 0.4 mu M. Moreover, the AA-induced fluorescence enhancement can be recognized by smartphone, which greatly extends the application in resource-limited areas.