Herein, a new double-enzymes-modulated fluorescent assay based on the quenching of upconversion nanoparticles (UCNPs) by Fe 3+ was constructed for sensitive determination of OPs. OPs can inhibit the activity of acetylcholinesterase to reduce the production of choline and further lead to the lack of H 2 O 2 in the presence of choline oxidase. Therefore, Fe 2+ cannot be converted into Fe 3+ , resulting in “turn-on” fluorescence of UCNPs. Under optimal conditions, an excellent linear correlation between the inhibition efficiency and the logarithm of the chlorpyrifos concentration was achieved with a detection limit (LOD) of 6.7 ng/mL in the range of 20–2000 ng/mL. The recovery for chlorpyrifos in apples and cucumbers was 89.5–97.1%. The results were consistent with those obtained by GC–MS. Overall, the integration of UCNPs into the double-enzymes-mediated Fe 3+ /Fe 2+ conversion endows this method with desirable rapidity, sensitivity, selectivity, stability, operational simplicity, and strong anti-interference capability, holding great potential in the application of food safety.
Fengyue Zhao,Juan Xiao,Shipeng Geng,Yi Wang,Panagiotis Tsiakaras,Shuqin Song
Fe 3+ /Fe 2+ interconversion is one of the key factors for heterogeneous electro-Fenton degradation of organic pollutants. In this study, MIL-101Fe-derived carbon wrapping Fe 7 S 8 nanocomposite (Fe 7 S 8 /C-1-600) exhibits outstanding rhodamine B (RhB) degradation ability with extremely low iron leaching and high recyclable degradability within 60 min in a wide pH range. Moreover, Fe 7 S 8 /C-1-600 presents a much higher activity for RhB degradation than Fe 3 O 4 counterpart without sulfidation, which could be mainly attributed to the accelerated Fe 3+ /Fe 2+ cycling by iron with both multiple valences (Fe 0 , Fe 2+ , and Fe 3+ ) and sulfur species (S 2− and S 2 2− ) of the catalyst. The enhancement of H 2 O 2 adsorption and activation into OH on Fe 7 S 8 surface is confirmed by density functional theory calculations with respect to that on Fe 3 O 4 . Interestingly, SO 4 · − can be generated by reacting S 2 2− with dissolved O 2 and subsequently converted into ·OH, which further facilitates RhB degradation. These findings may shed a new insight into the potential application of metal sulfides for wastewater treatment.
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