Study On The Fabrication Of Novel Electrochemical Sensor And Its Application In Detecting Chlorpyrifos

With the continuous development of economy and the rapid growth of agricultural production,the use of pesticides is also increasing.Excessive quantity and unreasonable use of pesticides will directly lead to over the standard of pesticide residues in environment and agricultural products.With the improvement of living standards,people pay more attention to the quality of life,and the requirements for diet and living environment are also increasing.The problem of pesticide residues has gradually become one of the hotspots of attention.Chlorpyrifos?CPF?,as an effective and toxic broad-spectrum insecticidal and acaric agent,is currently one of the most widely used organophosphorus pesticides in agricultural production.Chlorpyrifos residues in environment and agricultural products can be transferred to the human body through the enrichment of food chain,which seriously threatens the safety of human life.Therefore,it is necessary to develop a simple,rapid and effective method to detect chlorpyrifos.In this thesis,there are two kinds of chlorpyrifos imprinted polymers were prepared via molecular imprinting technology with the chlorpyrifos as template molecules,methacrylic acid?MAA?as functional monomers,Ethyleneglycol dimethacrylate?EGDMA?as crosslinker and 2,2'-Azobis?2-methylpropionitrile??AIBN?as initiator.Three kinds of chlorpyrifos molecularly imprinted electrochemical sensors were prepared based on nano platinum,gold nanoparticles,carbon nanotubes,graphene and their composites.The physical and chemical properties of the materials were characterized by scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,fourier transform infrared spectroscopy?FT-IR?and differential pulse voltammetry?DPV?.The selection of electrolyte,the concentration of the material,the pH value of the electrolyte and the adsorption time were optimizedThe selection of electrolyte,the concentration of material,the pH value of electrolyte and the adsorption time were optimized.Then the performance of chlorpyrifos imprinted electrochemical sensor was investigated in the linear response range,the limit of detection,repeatability,stability and selectivity.Finally,they were used for the analysis and detection of the actual samples.The main contents are as follows:?1?Preparation and application of a electrochemical sensor for chlorpyrifos by precipitation polymerization:the chlorpyrifos molecularly imprinted polymer?MIPs?was prepared by precipitation polymerization,and coated it on the surface of the glassy carbon electrode to constructe a molecularly imprinted electrochemical sensor?MIPs/GCE?.The properties of MIPs were determined by means of SEM,TEM,FT-IR,BET and electrochemical characterization.Under the optimal experimental conditions,the properties of the prepared MIPs/GCE were investigated.The selectivity is good under the interference of three structural analogues,and it can be applied to the analysis and detection of real samples.The recovery rate is between93%and 108%.?2?Preparation and application of a electrochemical sensor modified with multi walled carbon nanotubes and graphene oxide for chlorpyrifos by surface imprinting technique:the molecularly imprinted polymers?MIPs-SiO₂?were prepared via surface imprinting technique using silica?SiO₂?as the carrier.The carboxylated multi walled carbon nanotubes?c-CNTs?and graphene oxide?GO?were compounded to produce Gr-CNTs composites,and a layer of chitosan?CS?solution was modified on the surface of the modified electrode.Finally,a chlorpyrifos imprinted electrochemical sensor?MIPs-SiO₂/CS/Gr-CNTs/GCE?was constructed by using drop coating method to modify MIPs-SiO₂ on the surface of the modified electrode.The performance and morphological characteristics of MIPs-SiO₂ and Gr-CNTs were investigated by means of SEM,TEM,FT-IR,BET and XRD.Under the optimal experimental conditions,the properties of the prepared MIPs-SiO₂/CS/Gr-CNTs/GCE were investigated.The linear response range of the sensor is 1×10^-101×10^-5 mol L^-1,and the limit of detection is 1.85×10^-11 mol L^-1.The selectivity is good under the interference of three structural analogues,and it can be applied to the analysis and detection of real samples.The recovery rate is between 92.24%and 107.93%.?3?Preparation and application of a electrochemical sensor modified with PtAu doped on multi walled carbon nanotubes and graphene oxide for chlorpyrifos by surface imprinting technique:optimizing the preparation of the electrode material of chlorpyrifos imprinted electrochemical sensor.That is,PtAu double nanoparticles were doped on the Gr-CNTs composites to make PtAu-GrCNTs composites.A chlorpyrifos imprinted electrochemical sensor?MIPs-SiO₂/PtAu-GrCNTs/GCE?was constructed by using drop coating method to modify MIPs-SiO₂ on the surface of the modified electrode.The performance and morphological characteristics of MIPs-SiO₂and PtAu-GrCNTs were investigated by means of SEM,TEM,FT-IR,BET and XRD.Undertheoptimalexperimentalconditions,thepropertiesof MIPs-SiO₂/PtAu-GrCNTs/GCE were investigated.The linear response range of the sensor is 1×10^-111×10^-5 mol L^-1,and the limit of detection is 6.5127×10^-12 mol L^-1.The selectivity is good under the interference of three structural analogues,and it can be applied to the analysis and detection of real samples.The recovery rate is between91%and 108.46%.