The g-C3N4/BSA@MnO2 nanocomposites fluorescent off-on probe for detection and imaging of ascorbic acid in living cells

g-C3N4/BSA@MnO2 fluorescent off-on probe was constructed for sensitive and selective detection of ascorbic acid (AA). BSA@MnO2 nanoparticles using bovine serum albumin (BSA) as a template were anchored on the surface of graphite-phase carbon nitride nanosheets (g-C3N4 NSs) via electrostatic attraction to synthesize the g-C3N4/BSA@MnO2 nanocomposites. The fluorescence of g-C3N4 NSs was quenched by BSA@MnO2 nanoparticles (NPs) via fluorescence resonance energy transfer (FRET) and recovered in the presence of AA via the redox reaction between AA and MnO2. The nanocomposites therefore realized the fluorescent off–on detection of AA. Asatisfactory linear range of 0–120 μM and a limit of detection of 133 nM were obtained. The nanoprobe was applied for the detection of AA in food and drug samples as well as the fluorescent images of exogenous AA in Raw cells. The results showed that the nanoprobe possessed excellent properties for AA detection and broadened the biochemical analysis applications of g-C3N4-based nanomaterials.