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 (MnO 2 ) 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 MnO 2 into Mn 2+ , which induced the aggregation of AuNPs. Both the decomposed MnO 2 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 MnO 2 -based fluorescence assay. Furthermore, this amplification strategy was successfully applied to detect AA in food samples.