Study On Electrochemical Sensors For Detection Of Catechol And Other Phenols Based On Nanocomposites

Phenolic contaminants are very important target in environment. Phenols are widely used in the production processes of some products such as plastics, dyes, pesticides, papers, and petrochemicals. As a result, phenols are often found in waters, soils and sediments. Because most phenols exhibit a high degree of toxicity and adverse effects upon biota and humans, the European Union and the World Health Organization(WHO) have listed some of these compounds as priority pollutants and determined their maximum permissible levels in surface, ground and drinking waters. The majority of the phenols is a high toxic substances, which is discharged into natural water bodies primarily by industrial waste water. In our country, fourteen categories of compounds are identified as priority pollutants in the water, and the fifth category is phenolic pollutants. Therefore, the preparation of a fast, simple, sensitive chemical biosensor to achieve real-time monitoring is of greatest importance.Catechol exist extensively in the environment. As a recognized harmful material, it has a great influence on human health and environment. Catechol has inhibitory effect on central nervous system, can also affect the white blood cells in the synthesis of DNA and cause chromosomal aberrations. Catechol is the production of a variety of chemical products, the basic materials of pesticides and intermediate, it is very common in the environment. So the monitoring of catechol and phenolics received the attention of the general public.SBA-15 Mesoporous molecular has been used in many fields such as catalysis,absorption,separation and biological along with nano materials, due to the advantages of high surface area, ordered and tunable pore structure, containable hole wall thickness,high thermal and hydwthermal stability and facile modification of surface properties. Especially as a new carrier, it has aroused wide concern for its incomparable superiority with the other carriers. After amino-functionalization, SBA-15 modified with the macro-molecule protein through the connection of covalent bond by the cross linking reaction with glutaraldehyde,can be applied in the field of biological chemical sensors.In this paper, we prepared the electrochemical sensors for the determination of Catechol(CC) with the combination of mesoporous material and layer-by-layer self-assembly technique. The research ideas were outlined as follows:(1) mesoporous material was used as the carrier of polyphenol oxidase(PPO) due to the advantages of high surface area, and facile modification of surface properties, and then the electrochemical biosensors based on this substrate were fabricated with high sensitivity, good reproducibility and stability,(2) the electrochemical sensor for the determination of Catechols was prepared based on the premium properties of the mesoporous materials and other nanomaterials,Combining with the new type of sensitive elements and the use of layer-by-layer self-assembly technique.The detailed materials including three major components are summarized as follows:1 A novel electrochemical sensor for Catechol(CC) Based on mesoporous SBA-15/Au Nanoparticles/cobalt hexacyanoferrate(Co HCF) modified Glassy Carbon Electrode.A novel electrochemical sensor for catechol was developed based on the ordered mesoporous molecular sieve SBA-15, Au nanoparticles and cobalt hexayanoferrate(Co HCF) on a glassy carbon electrode. The method of electrodeposition was used to to immobilize the gold nanoparticles on glassy carbon electrode surface. The good electron transfer activity might be attributed to the effect of cobalt hexayanoferrate(Co HCF). As a electron transfer media with good redox catalytic activity, the layer-by-layer modification system consisted of mesoporous SBA-15 and other materials were used in the preparation of a novel electrochemical sensor for catechol. The mesoporous materials were characterized by X-ray diffraction(XRD) and N2 adsorption/desorption isotherms(BET). And the modified electrode was characterized by scaning elcronmoroscopy(SEM) and transmission electron microscopy(TEM). Cyclic voltammetry and electrochemical impedance spectroscopy experiments were carried out to investigate the electrochemical properties of the modified electrode. The sensor exhibits good amperometric response towards catechol(CC) due to the advantages of high surface area of mesoporous materials, and the excellent conductivity of Au NPs. Under the optimal experimental conditions, the current is linear with the concentration of catechol in the range from 3.0×10-7~5.10×10-5 M, with a detection limit of 5.0×10-8 M(S/N= 3) and a correlation coefficient of 0.998. The electrochemical sensor showed good performance in reproducibility, stability and interference experiments.2 Rutin Biosensor Based on Glassy Carbon Electrode Modified with MPs(FDU-15), Au Nanoparticles and polyphenol oxidase(PPO)Using three block copolymer F-127 as the template agent, an orderly mesoporous phenolic resin polymer MPs(FDU-15) was prepared by the method of Evaporation-Induced Self Assembly(EISA). A Rutin electrochemical sensor was fabricated by immobilizing MPs(FDU-15)/Au nanoparticles composite and polyphenol oxidase(PPO) on the surface of glassy carbon electrode. The electrochemical behavior of the Rutin sensor was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The sensor exhibits good amperometric response towards Rutin because of the excellent conductivity of MPs(FDU-15) and Au NPs. Under the optimal experimental conditions, the current is linear with the concentration of Rutin in the range from 3.0×10-7 ~8.5×10-6 M, with a detection limit of 6×10-8 M(S/N = 3) and a correlation coefficient of 0.999.3 Hydroquinone(HQ) Biosensor Based on Glassy Carbon Electrode Modified with Au Nanoparticles, NH2-SBA-15, L-Tyrosine and polyphenol oxidase(PPO)NH2-SBA-15 mesoporous material was prepared by using tetraethyl orthosilicate(TEOS) and(3-Aminopropyl)trimethoxysilane(APTMS) to enabling SBA- 15 functionality. polyphenol oxidase(PPO) was immobilized on the electrode surface using the method of glutaraldehyde(GA) covalent. NH2-SBA-15 and gold nanoparticles composite membrane can promote the electrical activity between electrode interface and solution, improve the performance of electrode catalytic reaction, selectively increase the electrochemical surface area. The electrochemical behavior of the HQ biochemical sensor was investigated by cyclic voltammetry and electrochemical impedance spectroscopy. The sensor exhibits good amperometric response towards HQ. Under the optimal experimental conditions, the current is linear with the concentration of HQ in the range from 1.5×10-6 to 0.9×10-5 M, with a detection limit of 3×10-7 M(S/N = 3) and a correlation coefficient of 0.997.