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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 .

An "off−on" assay system for H2O2 determination was developed based on assembling ultra-bright fluorescent silicon quantum dots (SiQDs) and PEG-MnO2 nanosheets. Among them, SiQDs acted as fluorometric reporter, which can effectively eliminate the interference of plant pigments under excitation of 365 nm. PEG-MnO2 nanosheets played dual function of nanoquencher and H2O2 recognizer. Unlike previous reports, the quenching mechanism of SiQDs by PEG-MnO2 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-MnO2 nanosheets. After addition of H2O2, PEG-MnO2 nanosheets were reduced to Mn2+, consequently resulting in the recovery of the SiQDs fluorescence. Combined with these properties, an off-on fluorescent method was built for determination of H2O2 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. [ABSTRACT FROM AUTHOR]

In this manuscript, a simple ratio fluorescent nanoprobe based on the hybrid of silicon oxide quantum dots (Si-O QDs) and Ag nanoclusters (Ag NCs) was developed. Benefiting from the inner filter effect (IFE) and fluorescent resonance energy transfer (FRET) effect, Si-O QDs and Ag NCs could from the stable probe in microenvironment of plant. The probe was used to measure the H 2 O 2 concentration generated by mitochondria in vitro via recording the I 455 /I 680 fluorescence ratio. Furthermore, this hybrid probe was applied to monitor the wound-induced H 2 O 2 in lettuce leaf, and realized the visualized fluorescence qualitative detection H 2 O 2 in vivo. • H 2 O 2 detection probe based on silicon oxide quantum dots and siliver nanoclusters. • IFE and FRET effect keep the stability of this sensor • The probe has good sensitivity for H 2 O 2 detection in the range of 0.008−60 mM. • This probe was used to detect the H 2 O 2 of plant mitochondria in vitro. • This hybrid probe realized the visualized fluorescent detection of H 2 O 2 in leaf. A silicon oxide quantum dots (Si-O QDs) and Ag nanoclusters hybrid nanosensing probe with dual-emission and small nanocrystals that acts as an "off-on" ratio fluorescent probe for hydrogen peroxide (H 2 O 2) detection was developed. The probe was used to measure the H 2 O 2 concentration generated by mitochondria in vitro via recording the I 455 /I 680 fluorescence ratio. Furthermore, this hybrid probe was applied to monitor the wound-induced H 2 O 2 in lettuce leaf, and realized the visualized fluorescence qualitative detection H 2 O 2 in vivo via laser scanning confocal microscope. The working mechanism of the probe is also investigated. Inner filter effect (IFE) estimation, Fourier transform infrared (FTIR) spectra and high-resolution transmission electron microscopy (HRTEM) images were applied to study the quenching mechanism and recovering reason of Si-O QDs fluorescence. The results show that the blue fluorescence of Si-O QDs can be quenched by Ag NCs via the IFE and fluorescent resonance energy transfer (FRET) effect. After adding H 2 O 2 , the surface groups of Ag NCs was changed and the IFE and FRET effects between the Si-O QDs and Ag NCs are disabled, thus the quenched Si-O QDs luminescence can be regularly recovered. [ABSTRACT FROM AUTHOR]