| Dimethoate is an organophosphorus pesticide,it is often used as an insecticide in agricultural production.However,due to excessive or inappropriate use of dimethoate,it can enter the human body and ecological environment through biological enrichment,food chain and other methods,which will pose a certain threat to human health and the global environment.At present,different detection methods have been reported to analyze the dimethoate residue in food,but the instruments used in the traditional methods are relatively expensive,the operation is complicated,and the maintenance cost of the instrument is also high,which is not suitable for on-site detection.Therefore,it is urgent to explore a method for dimethoate determination which is simple,stable,fast,and sensitive.The unique optical properties of quantum dots and the selective recognition of molecularly imprinted polymers were utilized in this experiment.A fluorescence sensor using molecularly imprinted polymer(MIP)-coated Cd Se/Zn S quantum dots(QDs)as the molecular recognition probe was constructed for the fast and high-throughput determination of dimethoate.This method can achieve stable,fast,high-throughput detection of dimethoate with high-sensitivity,and can utilized for the detection of dimethoate in environmental samples and food samples.The details are as follows:MIP-coated QDs were synthesized using one-step reversed-phase microemulsion method in the presence of hydrophobic Cd Se/Zn S QDs.Copolymerization was performed by using 3-aminopropyltriethoxysilane as the functional monomer,tetraethoxysilane as the crosslinker,and dimethoate as the template.MIP-coated QDs were used as the fluorescent probe for dimethoate recognition.The fluorescence of the MIP-coated QDs could be quenched by dimethoate when dimethoate becomes rebound on theimprinting sites of the MIP.In the experiment,MIP-coated QDs was characterized by transmission electron microscope(TEM),fourier transform infrarde sepctrometer(FT-IR),and fluorescence spectrum.And the stability of MIP-coated QDs was studied.The p H that affects the performance of the fluorescence sensor was optimized.The experimental results showed that the optimal p H was 7.4.The performances of the constructed fluorescence sensor were tested,including the establishment of standard curve,selectivity,repeatability.The experimental results showed that under the optimal detection conditions,the fluorescence quenching value of the constructed fluorescence sensor had a linear relationship with the concentration of dimethoate in the range of 5.0 μg/L-150.0 μg/L,and the correlation coefficient was 0.9958.The sensor showed good selectivity towards dimethoate compared with fenthion,acephate,trichlorfon.At the same time,the fluorescent sensor was used to separately detect dimethoate,dimethoate and structural analogues at the same concentration.The results showed that fluorescence intensity values of MIP-coated QDs were basically the same,and structural analogues can hardly interfere with dimethoate detection.The dimethoate recognized by MIP-coated QDs was eluted with a certain volume ratio of ethanol/acetic acid mixed solution for regeneration.After regeneration,the recognition probe MIP-coated QDs were used in the dimethoate solution again.After six cycles,the quenching value of MIP-coated QDs fluorescence intensity gradually decreased and retained93% of the initial quenching value.The dimethoate content in the environmental samples and food samples were detected using the method of spike and recovery experiment,and good results were obtained with the recoveries ranging from 89.8% to 98%. |
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