A Molecular Imprinting Electrochemical Sensor For Phenol Determination

Recently phenol has become typical in the waste water due to its strong toxicity and difficulty for degradation. Therefore, to develop fast, efficient, sensitive sensors for phenol detection is of great scientific importance and environmental value related to the protection of people’s health. Although the existing electrochemical sensors have the advantages of rapidness and sensitive activity, but they are still lack of specific recognition and easily to be interfered by the other components. To solve this problem, people atarted to seek new materials for electrochemical sensors with specific recognition.Molecular imprinting technology (MIT) is a kind of important method for well-tailoring materials with specific recognition selectivity. The synthesized Molecularly imprinted polymers (MIPs) based on MIT are possessing of a large number of holes with fixed-size and fixed-stereo shape, in which the functional groups are well-ordered and highly matched with the target molecules. As a results, the MIPs could selectively recognize and consequently combine with the target molecules due to their memorizing functions. In this paper, using the MIPs as the specific recognition material, carbon nanotubes as the sensitization material, the molecularly imprinted electrochemical sensor with specific recognition for phenol was prepared and characterized by infrared spectrometry (IR), ultraviolet spectroscopy (UV), differential pulse voltammetry (DPV), X-ray diffraction(XRD), etc. The structure, the selective recognition, the reproducibility, the sensitivity and the detection limit of the obtained molecularly imprinted electrochemical sensor were investigated as well.The thesis is divided into five chapters as follows:In chapter one, the research progress of molecularly imprinted technology and relative sensitization materials, the significance and the main research content were introduced.Chapter 2 introduced the experiment instruments, reagents, experiment- al process and the characterization method used in the research.In chapter 3, the mechanism of phenol electrooxidation on multi-wall carbon nanotube modified glassy carbon electrode (MWNTs-COOH/GCE) was studied by cyclic voltammetry (CV) in phosphate buffer solution (PBS). The results showed that the electrooxidation of phenol was controlled by both diffusion and adsorption. The mechanism was as follows:phenol was irreversibly electrooxidized to benzoquinone in the positive scan, and benzoquinone was then reduced to hydroquinone and catechol in the negative scan, which could further occur reversibly redox reaction. The existence of hydroquinone and catechol would affect the sensitivity and accuracy of the electrochemical measurement of phenol.Chapter 4 presented a surface molecularly imprinted polymer based on SiO2 nanoparticles by using graft polymerization, with polyethyleneimine (PEI) as the functional monomer, phenol as the template molecule, ethylene glycidyl ether as the cross-linking agent. SiO2 nanoparticles encapsulated in the net structure of prepared polymer was removed by an acidic etch process, to get the MIP for phenol. The built MIP/MWNTs-COOH/GCE sensor was tested by CV and DPV in PBS contained phenol. The results showed that MIP/MWNTs -COOH/GCE was highly specific recognition and good responsibility for phenol and anti-interfered by hydroquinone and catechol during the testing process, which exhibited good linear response from 1 × 10-8 M to 4×10-7 M with a detection limit of 3.4×10-8 M, the correlation coefficient(R2) was found to be 0.985.The fifth chapter summarized the conclusions obtained in the research, at the same time, the development prospect was proposed as well.