Promoted off-on recognition of H 2 O 2 based on the fluorescence of silicon quantum dots assembled two-dimensional PEG-MnO 2 nanosheets hybrid nanoprobe.

An "off-on" assay system for H ₂ O ₂ determination was developed based on assembling ultra-bright fluorescent silicon quantum dots (SiQDs) and PEG-MnO ₂ nanosheets. Among them, SiQDs acted as fluorometric reporter, which can effectively eliminate the interference of plant pigments under excitation of 365 nm. PEG-MnO ₂ nanosheets played dual function of nanoquencher and H ₂ O ₂ recognizer. Unlike previous reports, the quenching mechanism of SiQDs by PEG-MnO ₂ nanosheets is attributed to both the associative effect of inner filter effect and the static quenching effect. Thus, the fluorescence intensity of SiQDs at 445 nm decreased with increasing concentration of PEG-MnO ₂ nanosheets. After addition of H ₂ O ₂ , PEG-MnO ₂ nanosheets were reduced to Mn ²⁺ , consequently resulting in the recovery of the SiQDs fluorescence. Combined with these properties, an off-on fluorescent method was built for determination of H ₂ O ₂ in plant leaves with high sensitivity and selectivity. The present method has two linear ranges: from 0.05 to 1 μM with a detection limit of 0.09 μM and from 1 to 80 μM with a detection limit of 4.04 μM. Graphical abstract Schematic representation of the mechanism of SiQD/PEG-MnO ₂ nanoprobe for determination of H ₂ O ₂ .