Enhanced detection of ascorbic acid with cascaded fluorescence recovery of a dual-nanoquencher system

An innovative strategy with target-triggered cascade fluorescence recovery of a dual-nanoquencher system was developed to detect ascorbic acid (AA). Herein, manganese dioxide (MnO2) nanosheets and gold nanoparticles (AuNPs) were used as nanoquenchers simultaneously. Owing to their synergistic effects, the fluorescence of 2,3-diaminophenazine (DAP) was decreased efficiently, thus minimizing the background fluorescence. The introduction of AA triggered the decomposition of MnO2 into Mn2+, which induced the aggregation of AuNPs. Both the decomposed MnO2 and aggregated AuNPs possess weak quenching abilities towards DAP. Such a cascade amplification strategy enhanced the detection sensitivity for AA with a LOD as low as 6.7 nM, which was two orders of magnitude lower than that of MnO2-based fluorescence assay. Furthermore, this amplification strategy was successfully applied to detect AA in food samples.