A rapid and sensitive turn-on fluorescent probe for ascorbic acid detection based on carbon dots-MnO2 nanocomposites

Ascorbic acid (AA) is a significant small biomolecule and plays a key role in many biochemical processes. In this work, a rapid turn-on fluorescent probe was developed for sensitive and selective sensing of AA based on carbon dots-MnO2 nanocomposites. The nanocomposites were constructed by in situ synthesis of MnO2 nanosheets in carbon dot (C-dot) solution, and the fluorescence of C-dots was quenched with the formation of the nanocomposites due to the fluorescence resonance energy transfer (FRET) from C-dots to the generated MnO2 nanosheets. Once AA was introduced into the system, MnO2 nanosheets were reduced to Mn2+ and the fluorescence of C-dots would be recovered. Under the optimized conditions, this method shows rapid and sensitive response toward AA, the assay time is 2 min and the limit of detection is 68 nM. Moreover, the carbon dots-MnO2 nanocomposite based fluorescence sensing system was successfully employed to determine AA in commercial tablets with satisfactory results. Taking full advantage of C-dots and MnO2 nanosheets, this probe shows remarkable properties including easy operation, low cost and good biocompatibility, and has great potential to be used in biological and clinical diagnostic applications.