Study Of Modified Electrodes Based On New Materials And Their Applications In Electrochemical Biosensor

Electrochemical biosensors have valuable applications in chemistry, biology, environmental science, food industry, and medicine because of its excellent selectivity, high sensitivity, rapid response, low cost, continuous detection, easy to be miniaturized. Nanostructured materials are attractive in the developement of biosensors due to their novel optical, electrical, electrocatalytic and biocompatible properties. The performance of the resulting biosensors could be greatly improved with the application nanomaterials. In this thesis, nanomaterials such as poly (lactic-co-glycolic acid), graphene oxide, and ordered mesoporous carbon and silicon composite material were applied for the preparation of electrochemical biosensors. The developed biosensors for glucose and hydrogen peroxide show high sensitivity, low detection limit and rapid response. The details are described as follows:(1) A novel graphene oxide (GO) / prussian blue (PB) hybrid film was constructed by electropolymerizing Prussian Blue onto the GO modified glassy carbon electrode, and its electrochemical behaviors were studied. Raman spectra were used to investigate the successful formation of the GO/PB hybrid film. Electrochemical experiments showed that the graphene oxide greatly enhanced electrochemical reactivity of the PB. The GO/PB hybrid film modified electrode was used for sensitive detection of hydrogen peroxide. The sensor exhibited a wide linearity range from 5.0×10-6 to 1.2×10-3 M with a detection limit of 1.22×10-7 M (S/N=3), high sensitivity of 408.7uA·mM-1·cm-2 and good reproducibility. Furthermore, with glucose oxidase (GOD) as a model, the GO/PB/GOD/chitosan composite-modified electrode was also constructed. The resulting biosensor exhibited good amperometric response to glucose with linear range from 0.1 to 13.5 mM at 0.1 V, good reproducibility and detection limit of 3.43×10-7 M (S/N=3). In addition, the biosensor presented high selectivity and long-term stability. Human serum samples were assayed to demonstrate the practical use of the proposed biosensor and the recovery was good. These results indicated that it is feasible to apply the proposed biosensor to determine glucose in real samples. Therefore, the PB/GO hybrid films-based modified electrode may hold great promise for electrochemical sensing and biosensing applications.(2)The silicon-carbon nanocomposite material (MCSi) were used for immobilization of myoglobin (Mb) and preparation Mb-MCSi film modified electrode. Direct electron transfer of Mb between MCSi film and electrode surface and its electrocatalytic behavior were studied. X-ray diffraction (XRD), transmission electron microscopy (TEM), N2 adsorption-desorption were used to characterize the MCSi. Electrochemical impedance spectroscopy (EIS) was used to confirm the adsorption of Mb onto the MCSi film. The Mb immobilized in MCSi film retained its near-native conformations as characterized by the UV spectroscopy. At the same time, Mb-MCSi modified electrode showed good electrocatalytic activity for reduction of H2O2.With the range of 1.0-20.0uM, the catalytic peak current has a good linear relationship with the concentration of H2O2.(3)A biodegradable material of poly (lactic-co-glycolic acid) (PLGA) and, room temperature ionic liquid (ILs) (1-butyl-3-methylimidazolium tetrafluoroborate ([BMIM]BF4) was used as an immobilization matrix to entrap proteins and its bioelectrochemical properties were studied. Hemoglobin (Hb) was chosen as a model protein to investigate the composite system. The influences of scan rate, pH, interferent, et al. were discussed. The proposed biosensor showed good electrochemical response, selectivity, reproducibility and high sensitivity to H2O2 with the detection limit of 2.37×10-7 M (S/N=3) and displayed excellent in the range of 5.0×10-6 to 8.05×10-3 M, the catalytic reduction current of H2O2 was proportional to its concentration.