Study On Piezoelectric Sensor Technology Using Profenofos And Permethrin Molecularly Imprinted Polymer As Recognition Elements

Because of the pesticide abuse in agriculture,the pesticide residues in foodstuff exceed the national standard limit. It is necessary to establish the fast, on-spot detection method for the pesticide residue to guarantee the public's health as the present detection methods on pesticides can not do so.Molecularly imprinted polymers (MIPs) are polymers prepared in presence of a template that serves as a mould for the formation of template-complementary binding sites. Thus, MIPs can be created to recognize a target molecule with affinity and selectivity comparable to natural receptors and were called as"artificial antibody". And these materials can withstanding much harsher conditions than antibodies, such as high temperature, pressure, and organic solvents. These properties have made them extremely attractive for solving problems in the fields of preparative chemical separations, purification and sensor development, or for the removal of specific molecular targets from complex mixtures.In this dissertation, the preparation conditions of molecularly imprinted polymer microspheres, such as solvents, the volume of solvent and the amount of MAA and EGDMA, were optimized by precipitation polymerization in order to obtain desired uniform microspheres. Then, the microspheres in nanometers can be made in acetonitrile.Using profenofos and permethrin as template, the optimized precipitation polymerization method was employed to prepare their molecularly imprinted polymer microspheres.The Scanning Electron Microscopy XL60(SEM XL60)was used to describe the shape and size of the obtained polymer microspheres, and the results showed that the uniform, global nano-metric imprinted polymer microspheres were obtained, the size of them ranged from 500nm to 1500nm.The adsorption properties of the obtained imprinted polymer microspheres were analyzed by the equilibrium rebinding experiments and concluded their apparent maximum number (Qmax) and equilibrium dissociation constant(Kd) by Scatchard analysis. The results showed that the template bound on the imprinted polymer microspheres was larger than that on the non-imprinted polymer microspheres, which indicated that the imprinted sites formed in the imprinted polymer microspheres. The rebinding experiments of template and analogues on the polymer showed that the obtained imprinted microspheres have good selectivity to the template.Used as the recognition elements, the obtained polymer particles were coated on the surface of the electrode to develop the MIPs-QCM sensor.The prepared MIPs sensitive film on the electrode was observed employing Atomic force microscopy (AFM)。The AFM photograph showed that the microspheres on the film surface were well-distributed and it's thickness was 400 nm approximately.The detection conditions were optimized to analyze profenofos and the sensor exhibits a liner relationship between the frequency shift and profenofos concentration(y= 0.139 x + 2.26), and the detection limit was 19.5 ng/mL.