Theoretical And Experimental Studies Of New Electrochemical Sensors Based On Bi-functional Monomers And Dual-templates Molecularly Imprinted Polymer

Due to unique selective recognition and high sensitivity,molecularly imprinted electrochemical sensor(MIES)is of great value in the environmental monitoring and analytical fields.According to the results of computer simulation and molecular imprinting technology,this thesis reveals the molecular recognition mechanism and constructs two new types of electrochemical sensors.The main research contents of this thesis are as follows:(1)Using sulfamethazine as a template molecule,methacrylic acid(MAA),methyl methacrylate(MMA),methacrylamide(MAM),thiophene(Th),pyrrole(Py),3,4-ethylene dioxythiophene(EDOT)as functional monomers,the theoretical models of the surface molecular imprinting system were established.By calculating the binding energy,the optimal functional monomer was screened out.For the first time the ?-? stacking effect between the unsaturated ring groups in sulfamethazine and functional monomers was investigated.This was critical for further studying the molecular recognition mechanism between sulfamethazine and functional monomers.Based on the theoretical study,the molecularly imprinted polymer(MIP)was prepared by one-step electro-polymerization of bifunctional monomers.Using GQDs-Pt NPs nanocomposites as carrier,a new MIP electrochemical sensor was developed.In this sensing system,GQDs-Pt NPs nanocomposites can increase the charge transfer rate between the MIP and the substrate electrode.The combination of methacrylic acid and 3,4-ethylenedioxythiophene as bi-functional monomers can not only provide a large number of binding sites,but also form ?-? stacking effect between sulfamethazine and the monomers,which could further enhance the molecularly imprinted effectiveness.Under the best experimental conditions,the linear range of the sensor was 0.1 nmol/L~0.1 mmol/L.The detection limit of sulfamethazine reached 0.023 nmol/L.Compared with those earlier reported sulfamethazine electrochemical sensors,the MIP-GQDs-Pt NPs/GCE sensor has the advantages of high sensitivity,good selectivity,wide linear range,easy preparation and low cost.(2)Using acephate,imidacloprid as template molecules,o-phenylenediamine,resorcinol and dopamine as functional monomers,the advanced DFT-GGA-PBE algorithm was used to construct the most stable configuration of the template and monomers.By calculating the binding energy,the resorcinol was screened out as optimal functional monomer.Based on this theoretical study,double template molecular imprinted polymer was synthesized by electro-polymerization method.Using GQDs-Au NPs nanocomposite as carrier,double template molecularly imprinted electrochemical sensor of acephate and imidacloprid was successfully prepared.In this sensing system,the dual template molecularly imprinted polymer could not only save the production cost,but also give the sensor two kinds of detection capabilities.Moreover,the GQDs-Au NPs nanocomposite enhanced the electron transfer capability between the MIP membrane and the electrode active center.Therefore,the sensitivity of the sensor was greatly improved.Under the best experimental conditions,the linear ranges of acephate and imidacloprid were 0.1 nmol/L~0.1 mmol/L and 1 nmol/L~0.1 mmol/L,respectively.The detection limits were 0.034 nmol/L and 0.211 nmol/L.The sequential detection of acephate and imidacloprid was achieved for the first time.Compared with those earlier reports,the sensor in this work is better in terms of lower detection limit,wider linear ranges and cost.The MIP-GQDs-Au NPs/GCE sensor is highly valuable for food safety and environmental control.