Smartphone assisted fluorescent sensor for Fe3+ and ascorbic acid determination based on off-on carbon dots probe

Iron ions (Fe 3+ ) and ascorbic acid (AA) are of great significance to living organisms. Herein, carbon dots (C-dots)-based “off-on” fluorescent probe was designed for Fe 3+ and AA analysis. In presence of Fe 3+ , 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 Fe 3+ in range of 10–500 µM with a limit of detection (LOD) of 0.9 µM. Interestingly, when AA was introduced to the C-dots-Fe 3+ system, the fluorescence of C-dots was significantly recovered, which could be ascribed to the oxidation-reduction reaction between Fe 3+ and AA. Based “off-on” fluorescent C-dots probe, the linear range of 5–500 µM was obtained with LOD of 0.4 µM. Moreover, the AA-induced fluorescence enhancement can be recognized by smartphone, which greatly extends the application in resource-limited areas.