Study On Surface Molecularly Imprinting Technology Based On Nanomaterials And Their Applications In Specific Recognition Of Pesticide

Since the Second World War, chemical pesticides played a huge role in ensuring agricultural production and protecting human health. However, based on the toxic pesticides, the effect of them is very serious. And in recent years, more and more people have got cancer, and a lot of them are young. Most of these cases come from the contaminate of food vegetables. Organophosphate pesticides (OPs) and neonicotinoid insecticide, as commonly used herbicide and pesticides in our country, are high toxic, refractory and may cause dizziness, nausea, diarrhea, limbs, and so on. By now, the analytical protocols used to determine these common pesticides are mainly based on gas chromatography (GC), high performance liquid chromatography (HPLC) or coupled to mass spectrometry (MS) and enzymoimmunoassay (ELISA). However, all of these methods require large and expensive instruments and cannot be suitable for field or online monitoring. Recently electrochemical detection has been used in on-site measurement and various sensors because of its sensitivity, simplicity and lower cost. However, the moderated selectivity of these electrochemical method can be considered as a main problem.The molecular imprinting technique is an attractive method for the generation of polymer-based molecular recognition elements tailor-made for a given target or group of target molecules. Because of the ease of mass production, high stability and low cost of MIPs, this technology has potential wide applications in many scientific and technical fields, such as solid-phase extraction (SPE), chromatographic separation, membrane separations, sensors, drug releases and catalysts. However, a variety of traditional imprinted materials suffer from some drawbacks including small binding capacity, slow mass transfer and irregular materials’shape. In recent years, scientists have made considerable efforts to overcome these problems by adapting a nanofabrication technique such as mesoporous silica particles and polyaniline nanofibers. This technique is based on the small dimension with extremely high surface-to-volume ratio of nano-imprinting materials, and then the imprinting technique can create more effective recognition sites than the only use of porogens in traditional approaches.The main work of my paper is focusing on the study of the novel principle for the rapid determination of some common pesticides by the molecular imprinting technique. In this thesis, based on the functional alloy nanoparticles and multiwalled carbon nanotube as supporting matrix, we have synthetized sensitive, selective and easy-to-use molecularly imprinted materials for the detection of these pesticides by combination of molecularly imprinted technology and electrochemical sensor. We studied the characterization of the prepared molecularly imprinted materials by FT-IR, UV-Vis spectrum, transmission electron microscopy (TEM) and scanning electronic microscopy (SEM). And the electrochemical behavior of these pesticides was discussed by differential pulse voltammetry (DPV), cyclic voltammetry (CV), electrochemical impedance spectroscopy and so on. The primary research work is as follows:Chapter1:OverviewIn chaper1, we mainly introduced the varieties of pesticides, noxious effect of it and the development of determination for pesticide residue. Then based on the basic principle and development of molecularly imprinted technology, we focus on the research and application of the technology combining molecularly imprinted technology with sensor. Finally, we emphatically pointed out the purpose and significance of the dissertation, its innovation spot and content as well.Chapter2:Fe3O4@Au Sphere Molecular Imprinting with Self-Assembled Monolayer for the Recognition of Parathion-MethylA novel surface molecular imprinting technique based on spherical molecular imprinted monolayer (SMIM) was prepared from3-mercaptopropionic acid self-assembled on core-shell Fe3O4@Au nanoparticles (NPs) with preadsorbed templates (parathion-methyl) which widespread used in agricultural production. The proposed imprinted sensor was characterized by transmission electron microscope (TEM), FT-IR and UV-visible absorbance spectrum analysis. The result obtained from a series of electrochemical experiments proved that the prepared sorbent had a good adsorption capacity and a fast mass transfer rate to parathion-methyl. The response of the SMIM was linearly proportional to concentration of parathion-methyl over the range of2.0×10-7to1.0×10-4mol L-1, with a lower detection limit of1.0×10-7mol L-1. The selectivity of the sensor was tested by measuring parathion-methyl in the presence of some possible interferent compounds such as imidacloprid, diuron, propanil, parathion and paraoxon obtaining satisfactory results. This imprinted electrochemical sensor was successfully employed to detect parathion-methyl with a simple surface molecular imprinting and self-assembled process which could easily and rapidly remove parathion-methyl by cyclic voltammetry.Chapter3:A molecularly imprinted polymer based on the functionalized multiwalled carbon nanotubes for the electrochemical detection of parathion-methylA novel composite of vinyl group functionalized multiwalled carbon nanotubes (MWCNTs) molecularly imprinted polymer (MIP) was synthesized and applied as a molecular recognition element to construct an electrochemical sensor for parathion-methyl in this paper. The special molecular recognition properties of parathion-methyl mainly dominated by π-π, p-π interaction and hydrogen bonding formed among functional monomer, template and matrix. A series of electrochemical experiment results proved that the prepared material had a good adsorption capacity and a fast mass transfer rate to parathion-methyl. The good selectivity of the sensor allowed fine discriminations of parathion and paraoxon, which own the similar structures to parathion-methyl. The response of the MIPs was linearly proportional to the concentration of parathion-methyl over the range of2.0×10-7to1.0×10-5mol L-1with a lower detection limit of6.7×10-8mol L-1(S/N=3). Meanwhile, this sensor was applied to detect parathion-methyl in pear and cucumber with the average recoveries between94.9%and106.2%(RSD<5%). The results mentioned above show that the novel electrochemical sensor is an ideal device to determine parathion-methyl real-time in real samples.Chapter4:Detection of imidacloprid based on imprinted porous silicate film at functionalized multi-walled carbon nanotubes modified carbon electrodeA novel sensitive and selective imprinted porous silicate film at functionalized multi-walled carbon nanotubes modified carbon electrode was successfully constructed for the detection of imidacloprid. The special molecular recognition properties of imidacloprid mainly dominated by p-π, π-π interaction formed among functional monomer, template and matrix. The proposed imprinted sensor was characterized by using scanning electron microscope (SEM) and electrochemical methods. The response of the imprinted porous silicate film was linearly proportional to the concentration of imidacloprid over the range of2.0×10-8to4.0×10-5molL-1with the detection limit of1.0×10-8mol L-1.Meanwhile, this sensor was proved to be aversatile sensing tool for the selective detection of imidacloprid in real samples.