A strategy based on CsPbBr 3 quantum dots (QDs) is described for the determination of ziram pesticide. A facile and inert gas-free method was used for the synthesis of CsPbBr 3 QDs. The obtained CsPbBr 3 QDs displayed turn-off fluorescence behavior for ziram. The fluorescence intensity of the CsPbBr 3 QDs ( E x / E m = 365/516 nm) was inversely proportional to the concentration of ziram (0.10 to 50.0 ppm) with a detection limit of 0.086 ppm. Notably, satisfactory recoveries (100 ± 0.25 to 107 ± 5.72%) were obtained in spiked fruit samples, which demonstrated that this method is capable of detecting ziram in real samples. In addition, the mechanism for the detection of ziram was investigated in detail. According to the results, this mechanism can be tentatively explained by fluorescence quenching originating from the increased surface defects and the structural changes of the CsPbBr 3 QDs. The detection ability of this strategy shows promising applicability in food safety. Graphical abstract
Determination of dithiocarbamate fungicides using chromatography is not available for real-time and on-site residue analysis. Herein, a novel fluorescent assay for dithiocarbamate fungicides ziram based on the boron-doped carbon nanodots (B-CDs) and tyrosinase was established. The fluorescent B-CDs with maximum excitation and emission at 490 and 540 nm were synthesized by hydrothermal reaction. PCV can combine with the B-CDs, leading to a fluorescent quenching effect. Tyrosinase can catalyze the PCV oxidation, thus fluorescent intensity of the B-CDs recovers due to the consumption of PCV. While ziram can inhibit tyrosinase activity, resulting in less oxidation of PCV and more quenching effect of the B-CDs. Fluorescence was first employed to enzymatic ziram assay to improve sensitivity. This assay demonstrates a higher sensitivity for ziram (LOD: 0.46 μg L -1 ) compared to other optical assays and feasibility of determining ziram residue in environmental and food samples (Recovery: 73.9–92.6%, RSD: 2.53–6.57%).
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