Study On Preparation Of Novel Molecular Imprinting Nano Membrane Materials And Its Electrochemical Sensing

Molecularly imprinted polymers （MIP） has became an important syntheticmaterials, because of its molecular recognition ability to mimic natural receptor,structure-activity predetermination, specific recognition and extensive practical. In theresearch of MIP, development and application of molecularly imprinted polymer filmis the most attractive subject. MIP membrane provides synthetic receptors with highselectivity and stability. And electrochemical sensors could offer high sensitivity, lowcost, with possibility of easy design, manufacture, automation and miniaturization.MIP film as the recognition element to build a new generation of electrochemicalsensors and biosensors have considerable prospect. It is a hot topic with electricitypolymerization method for preparation of molecularly imprinted polymer film. Byadiusting the polymerization rate and time can be obtained different density polymerfilm, and the polymer film can be formed on the any shape and size electrode surface.But the template molecule of the imprinted membrane is difficult to elution, the lowconductivity, poor regeneration and reversible etc., limiting the application ofmolecularly imprinted membrane in electrochemical sensors. Therefore looking fornew monomers and preparation methods to extend the application of molecularlyimprinted membrane electrochemical sensor has an important significance.This research is trying to introduce nano-materials combined with molecularimprinting technique and prepare novel electrochemical sensors. Base on molecularlyimprinted nano-composite membrane preparation and molecularly imprintedpolymerization membrane electrochemical sensor applications, use differentfunctional monomers and electric polymerization method to overcome the difficultiesof the traditional imprinted matrix, combination of molecular imprinting technology,nano-materials and electrochemical sensor. Successfully constructed a series ofelectrochemical sensors for imprinted matrix as sensitive components, and researcheda series of characteristics of the imprinted membrane.A novel electrochemical sensor based on molecularly imprinted polymer film has been developed for aspirin detection. The sensitive film was prepared byco-polymerization of p-aminothiophenol （p-ATP） and HAuCl4on the Au electrodesurface. First, p-ATP was self-assembled on the Au electrode surface by the formationof Au–S bonds. Then, the acetylsalicylic acid （ASA） template was assembled ontothe monolayer of p-ATP through the hydrogen-bonding interaction between aminogroup （p-ATP） and oxygen （ASA）. Finally, a conductive hybrid membrane wasfabricated at the surface of Au electrode by the copolymerization in the mixingsolution containing additional p-ATP, HAuCl4and ASA template. Meanwhile, theASA was spontaneously imprinted into the poly-aminothiophenol gold nanoparticles（PATP–AuNPs） complex film. The amount of imprinted sites at the PATP–AuNPsfilm significantly increases due to the additional replenishment of ASA templates.With the significant increasing of imprinted sites and doped gold nanoparticles, thesensitivity of the molecular imprinted polymer （MIP） electrode gradually increased.The molecularly imprinted sensor was characterized by electrochemical impedancespectroscopy（EIS）, differential pulse voltammetry（DPV）, and cyclic voltammetry（CV）. The linear relationships between current and logarithmic concentration wereobtained in the range from1nmol L^-1to0.1μmolL^-1and0.7μmol L^-1to0.1mmolL^-1. The detection limit of0.3nmol L^-1was achieved. This molecularly imprintedsensor for the determination of ASA has high sensitivity, good selectivity andreproducibility, with the testing in some biological fluids also has good selectivity andrecovery.Capacitive detection of methyl-parathion （MP） was carried out on apolyquercetin （Qu）–polyresorcinol （Re）–gold nanoparticles （AuNPs） modifiedelectrode using a molecular imprinting technique and electropolymerization method.Cyclic voltammetry and electrochemical impedance spectroscopy （EIS）measurements were used to monitor the process of electropolymerization. Uncoveredsurface areas were plugged with dodecanethiol to make the layer dense， and theinsulating properties of the layer were studied in the presence of[Fe（CN）6]3/[Fe（CN）6]4redox couples and by the use of AC impedance measurements. The template molecules and the non-bound thiol were removed fromthe molecularly imprinted polymer film capacitance sensor surface with an acidicsolution of ethanol. The sensor’s linear response range was between70nmol L^-1and1μmol L^-1， with a detection limit of0.34nmol L^-1. The presented research providesa fast, sensitive and real-time method for detecting organophosphate pesticides. Inwater and in organic samples, the modified electrode has good antiinterferencecapabilities and stability （distilled water, tap water, river water, and rain watersamples all have good recovery）. Moreover, the MIPC sensor can detect MP on fruitsurfaces within72h after spraying pesticides.The third part of this thesis using molecular imprinting technique, dopamine asthe template molecules, o-phenylenediamine as a functional monomer, usingelectricity polymerization method successfully constructed a electrochemical sensorwith which dopamine has a specific selection on the glassy carbon electrode surfacemodified with a multi-walled carbon nanotubes. The molecularly imprinted sensorwas characterized by cyclic voltammetry （CV）, differential pulse voltammetry（DPV）, and electrochemical impedance spectroscopy （EIS）. The presentedresearch provides a fast and sensitive method for detecting dopamine. The sensor’slinear response range was between0.6μmol L^-1and50μmol L^-1, with a detectionlimit of3.3nmol L^-1. This method has good selectivity, high sensitivity, goodrepeatability and doesn’t need purification step, providing a simple and controllablemethod to detect dopamine. The non-imprinted electrode is unselective and failed torecognize dopamine.