Study On Novel Materials Of Surface Molecularly Imprinted And Recognizing Polymers With Their Application In Electrochemical Sensors

Molecular imprinting technique has become a promising way to prepare molecularly imprinted polymers (MIPs) with tailored selectivity for analytes. MIPs exhibit an affinity for the template molecule over other structurally related compounds. MIPs have some advantages containing their predetermination, specificity and practicability for molecular recognition. However, traditional MIPs have many limitations, such as incomplete template removal, low-affinity binding and slow mass transfer. Therefore, researchers develop surface MIPs materials on the surface of matrix using surface imprinting technique, which enables the template-imprinting sites to situate at the surface or in the proximity of the materials, providing the advantages of favorable selectivity and fast association/dissociation kinetics. Therefore, surface imprinting technique can synthesize materials with high selectivity and amount of adsorption for targets. These materials can also be prepared with surface molecular recognition technique. Using this method, the support matrix was grafted with functional groups or polymers. The materials of surface MIPs and recognizing polymers have been applied in electrochemical sensors and separation media. Analytical methods based on these surface materials can greatly increase the sensitivity and selectivity. After modifying surface MIPs and recognizing materials onto the electrochemical sensor, their combination can lead to high sensitivity and selectivity for electrochemical detection.In this dissertation, we laid our emphasis on the novel materials of surface MIPs and recognizing polymers. Through free radical polymerization, four kinds of surface imprinting materials were prepared with vinyl groups functional SiO2-coated graphene oxide, reduced graphene oxide, boronic acid-functionalized graphene oxide, and octavinyl-polyhedral oligomeric silsesquioxane as the support matrix. In addition, a novel material of surface recognizing polymers on multiwalled carbon nanotubes (MWCNTs) was prepared. These materials belonged to composites. We combined materials with electrochemical sensors to detect dopamine of biological molecule, rutin of drug molecule, environmental pollutants, which had good selectivity, stability and sensitivity. This dissertation opens up a new and effective way to develop the fields including surface imprinting technique, electrochemical sensors, bioanalysis, the determination of drug and environmental pollutants.The dissertation contains six chapters. The primary research work is as follows:Chapter1. OverviewThe chapter gave a comprehensive overview for the principle, development and application of molecular imprinting technique. The development and application of surface molecular imprinting technique was highlighted. We introduced the classification, preparation and application of surface MIPs materials. In addition, we put emphasis on introducing the research and application of electrochemical sensors modified with surface MIPs materials. Moreover, we introduced the preparation and application of surface recognizing materials. Finally, we expounded our research significance and main contents of the dissertation.Chapter2. The preparation of surface molecularly imprinted polymers material based on SiO2-coated graphene oxide and its electrochemical sensing dopamineA novel imprinting route based on graphene oxide was proposed for preparing a surface molecularly imprinted polymers material based on SiO2-coated GO (GO/SiO2-MIPs). The sensor based on GO/SiO2-MIPs was applied to the specific determination of dopamine (DA) with satisfactory results. In this route, SiO2-coated GO sheets were synthesized in a water-alcohol mixture with sol-gel technique. Prior to polymerization, the vinyl groups were introduced onto the surface of GO/SiO2through chemical modification with γ-methacryloxypropyl trimethoxysilane (γ-MAPS). Through free radical polymerization, GO/SiO2-MIPs were successfully obtained by the copolymerization in presence of vinyl groups functionalized GO/SiO2, dopamine, methacrylic acid and ethylene glycol dimethacrylate. GO/SiO2-MIPs were characterized by Fourier transform infrared spectrometer (FTIR), Thermal gravimetric analysis (TGA), Raman spectroscopy, Scanning electronic microscopy (SEM) and Atomic force microscopy (AFM). The electrochemical characteristics of GO/SiO2-MIPs modified electrode was investigated by cyclic voltammetry and differential pulse voltammetry (DPV). The DPV current response of GO/SiO2-MIPs sensor was nearly3.21times that of the non-imprinted polymers. In addition, the GO/SiO2-MIPs sensor could recognize DA from its relatively similar molecules of norepinephrine and epinephrine. The GO/SiO2-MIPs sensor had a wide linear range over DA concentration from5.0×10-8to1.6×10-4M with a detection limit of3.0×10-8M (S/N=3). The preparation for GO/SiO2-MIPs was easy. And this paper combined surface imprinting technique and electrochemical sensor to achieve the high selective and sensitive determination for DA. This method should be expected to be used in life science and clinical analysis.Chapter3. The preparation of surface molecularly imprinted polymers material based on reduced graphene oxide and its electrochemical sensing4-nitrophenolA surface molecularly imprinted polymers material based on reduced graphene oxide (RGO-MIPs) was prepared. The sensor based on RGO-MIPs was applied to the specific determination of4-nitrophenol (4-NP) in environmental samples. RGO-MIPs were synthesized using RGO as the support matrix,4-NP as the template molecule, methacrylic acid as the functional monomer, and EGDMA as the cross-linking agent. RGO-MIPs were characterized by FTIR, TGA, Raman spectroscopy and SEM. The electrochemical characteristics of RGO-MIPs sensor were investigated by differential pulse voltammetry. The RGO-MIPs sensor exhibited a high adsorption and good selectivity toward4-NP compared with some phenolic and nitroaromatic compounds. In addition, RGO-MIPs sensor had high sensitivity for4-NP. The RGO-MIPs sensor had a wide linear range over4-NP concentration from0.01to100.0μM with a detection limit of0.005μM (S/N=3). The electrochemical sensor based on RGO-MIPs shows high sensitivity, selectivity and rapid response, and provides a novel method for detecting4-NP in environmental water samples.Chapter4. The preparation of surface molecularly imprinted polymers material based on boronic acid-functionalized graphene oxide and its electrochemical sensing dopamineA surface molecularly imprinted polymers material based on boronic acid-functionalized graphene oxide (GOBA-MIPs) was prepared. The sensor based on GOBA-MIPs was applied to the specific determination of dopamine (DA). Boronic acid-functionalized graphene oxide was synthesized in the presence of3-aminobenzeneboronic acid, EDC·HCl and NHS. GOBA-MIPs were prepared using boronic acid-functionalized graphene oxide as the support matrix, DA as the template molecule, acrylamide as the functional monomer, and EGDMA as the cross-linking agent. The electrochemical characteristics of GOBA-MIPs sensor were investigated by cyclic voltammetry and differential pulse voltammetry. It has been demonstrated that this homogeneous and stable molecular imprinting material showed a double-recognition for DA with the specific cavities and boronic acid groups which contained in the materials. The experiment results showed that GOBA-MIPs had a high adsorption capacity toward DA with3.49times current response compared with non-imprinted polymers. The GOBA-MIPs sensor had a wide linear range over DA concentration from0.5to100.0μM with a detection limit of0.2μM (S/N=3). This work innovatively combined boronic acid-functionalized technique with surface imprinting to achieve double-recognition for DA.Chapter5. The preparation of surface molecularly imprinted polymers material based on POSS and its application in electrochemical detecting rutinA surface molecularly imprinted polymers material based on polyhedral oligomeric silsesquioxane (POSS-MIPs) was prepared. The sensor based on POSS-MIPs was applied to the specific determination of rutin in tablets. Through free radical polymerization, POSS-MIPs were prepared using octavinyl-POSS as the support matrix, rutin as the template molecule, acrylamide as the functional monomer, and EGDMA as the cross-linking agent. POSS-MIPs were characterized by TGA and SEM. The electrochemical characteristics of POSS-MIPs sensor were investigated by cyclic voltammetry and differential pulse voltammetry. The experiment results showed that POSS-MIPs exhibited a high adsorption capacity toward rutin with3.31times current response compared with non-imprinted polymers. In addition, the POSS-MIPs sensor could recognize rutin from its relatively similar molecules of kaempferol and quercetin. Its selectivity coefficient for rutin over kaempferol or quercetin was larger than6.0. The POSS-MIPs sensor had a wide linear range over rutin concentration from1.0to70.0μM with a detection limit of0.5μM (S/N=3). This work provides new ideas for the preparation and application of POSS composite.Chapter6. The preparation of surface poly(acrylamide) material based on MWCNTs and its application in electrochemical detecting methyl parathionIn this chapter, a surface poly(acrylamide) material based on MWCNTs (MWCNTs-PAAM) was prepared using vinyl-functionalized MWCNTs as the support matrix, acrylamide as the monomer. MWCNTs-PAAM had high content of amide groups, which had affinity for methyl parathion (MP) through p-π and hydrogen-bond interaction. So MWCNTs-PAAM had a certain recognition for MP. MWCNTs-PAAM were characterized by FTIR, TGA and SEM. The electrochemical characteristics of MWCNTs-PAAM modified electrode were investigated by cyclic voltammetry and differential pulse voltammetry. The selectivity of MWCNTs-PAAM sensor was investigated. The MWCNTs-PAAM modified electrode exhibited a high adsorption and strong affinity for methyl parathion compared with some metal ions and nitroaromatic compounds. The MWCNTs-PAAM modified electrode had a wide linear range over MP concentration from5.0×10-9to1.0×10-5M with a detection limit of2.0×10-9M (S/N=3). The MWCNTs-PAAM modified electrode was proved to be a suitable sensing tool for the fast, sensitive and selective determination of methyl parathion in environmental water samples.