g-C3N4 nanosheets as “on-off-on” selective fluorescence biosensor to detect ascorbic acid via redox reaction

A novel fluorescence probe was built by using graphitic carbon nitride (g-C 3 N 4 ) nanosheets . Fluorescence of the g-C 3 N 4 nanosheet solution was effectively quenched by Fe 3+ via photoinduced electron transfer (PET). Moreover, the linear detection range for Fe 3+ was 0–43.33 nM with a limit of detection of 4 nM. Fluorescence recovery of g-C 3 N 4 was observed upon addition of ascorbic acid (AA) to the g-C 3 N 4 nanosheet–Fe 3+ system, and the paramagnetic Fe 3+ was reduced to diamagnetic Fe 2+ by blocking PET. An “on–off–on” fluorescence response was observed through the oxidation–reduction between Fe 3+ and AA. Furthermore, a wide linear detection range for AA was found in 0–26.67 nM. Thus, this system can play a dual role in the selective and sensitive detection of Fe 3+ and AA in aqueous media via “on–off–on” fluorescence response.