Study On The Electropolymerization Membranes And Their Applications In Neonicotinoids Pesticides Determination

Molecularly imprinted polymers (MIPs) exhibit an affinity for the target molecule over other structurally related compounds. Electrochemical sensor based on MIPs can lead to good mechanical stability, high selectivity and easy preparation. Surface imprinting technique, almost whole template imprinting sites are situate at the surface or in the proximity of the materials, which providing the advantages of favorable selectivity and fast association/dissociation kinetics. The MIPs films prepared by electropolymerization have superior properties with respect to adherence to the transducer surface as well as simplicity and express of prepare. Moreover, the electropolymerization enables easy control of the film thickness and morphology as well as high reproducibility. The introduction of conducting nanomaterials would improve the electrochemical response and the effective surface area of the electrode, which would produce more imprinting sites on the surface of MIPs.The neonicotinoids pesticide imidacloprid is being extensively used in agricultural crops and its residual period can be as long as25days. So far, the most used method for the detection of neonicotinoid pesticides is high performance liquid chromatography. Although this method have shown sensitivity and specificity for the detection of imidacloprid, they are expensive, time consuming, require complicated sample pretreatments and connot be used for on-line monitoring. Tacking the high electroactivity of imidacloprid into consideration, electrochemical analytical technique for imidacloprid determination is an attractive method. To eliminate the presence of excess analogs interferents influence, combine the advantages of molecular imprint technique and electrochemical technique, we could come true the target of selectivity recognize imidacloprid from practical composite samples.In this dissertation, electropolymerization method is used as the basic approach for construct MIPs, combined the advantages of nanomaterials as the support matrix, we fabricate three kinds of MIPs electrochemical sensors to detect imidacloprid, which have good selectivity, sensitivity and stability. This dissertation opens up a new way to develop the fields of surface imprinting technique, the determination of pesticide residual in environmental and fruit. The primary research work is as follows:Chapter1. OverviewIn this chapter, we comprehensive summarize the research status of molecular imprinted technique. Especially, we highlight the preparation approach and application of electropolymerization method. Then we introduce the nanomaterials and their applications in MIPs electrochemical sensors. In addition, we introduce the detection methods of pesticide residual and their development prospect. Finally, we expound our research significance and main contents of the dissertation.Chapter2. Molecularly imprinted sensor based on electropolymerized poly(o-phenylenediamine) membranes at reduced graphene oxide modified electrode for imidacloprid determinationIn this paper, a novel electrochemical sensor based on imprinted PoPD membranes at RGO modified electrode for selective and sensitive detection of imidacloprid was fabricated. RGO was dropped onto the surface of GCE to amplify the electrocatalytic activity. The imprinted PoPD membranes were then synthesized onto RGO surface by elctropolymerization using oPD as the monomer and imidacloprid as the template. The imprinted sensor exhibited good selectivity toward imidacloprid in comparison with other similar interferents. Under the optimal experimental conditions, the current response of the imprinted sensor was linear to the imidacloprid concentration in the range of0.75μmol/L to70.00μmol/L with a detection limit of0.40μmol/L (S/N=3). The imprinted electrochemical sensor was successfully employed for the selective determination of imidacloprid in real samples.Chapter3. Molecularly imprinted porous silicate sensor for electrochemical determination of imidacloprid based on graphene/metalloid polymer hybridsA novel molecularly imprinted porous silicate sensor was successfully fabricated for imidacloprid determination by integrating electropolymerization with RGO/MPHs-GO nanocomposite materials. Both of RGO and MPHs-GO were employed to enhance the electrochemical active surface area and electrode electrical conductivity, further to increase the amount of effective imprinted sites. Meanwhile, the SiO2on the surface of Au@SiO2(MPHs) could be electropolymerized with pretreated silica sol and an intimate thin gel film were then deposited on the electrode surface. The prepared RGO/MPHs-GO MIPs sensor exhibited not only high selectivity toward imidacloprid in comparison to other interferents, but also a wide linear range over imidacloprid concentration from0.50μmol/L to50.00μmol/L with a detection limit of0.30μ.mol/L (S/N=3). Moreover, the imprinted porous silicate sensor was successfully applied to the selective detection of imidacloprid with satisfactory results.Chapter4. A novel composite of cyclodextrin-reduced graphene oxide hybrid nanosheets and surface molecularly imprinted polycarbazole for electrochemical sensing imidaclopridThis paper reports a surface molecularly imprinted polymers polycarbazole membranes at the (3-CD-RGO modified electrode for electrochemical sensing of imidacloprid. The results obtained from a series of electrochemical experiments proved that this electrochemical sensor had a good adsorption capacity and a fast mass transfer rate for imidacloprid. The response of the imprinted sensor was linearly proportional to the concentration of imidacloprid over the range of0.10μ.mol/L to40.00μmol/L with the detection limit of0.07μmol/L (S/N=3). Besides, this novel electrochemical sensor was applied to the detection of imidacloprid in river water samples with satisfactory results.