Direct Electrochemistry And Electrocatalysis Of Redox Proteins Immobilized In Nanomaterials Modified Electrode

In general the direct electron transfer rate of redox protein with the electrode is slow. The reasons can be summarized as follow:most proteins have larger molecular weight and their electrical activity group or redox center was far from the electrode surface and usually deeply buried within the protein molecules; the orientation of the protein in the electrode surface is negative. So it is difficult for electron to transfer between proteins and electrode. Also the impurities in solution can be adsorbed on the electrode surface and hinder electron transfer between proteins and electrode. Nanomaterials have exhibited unique optical, electrical and catalytic properties with good biocompatibility, high activity and selectivity. When nano-materials are used as the modifier on the electrode, the specific physical and chemical properties of the nanomaterial itself with the large electrode surface area and good adsorption properties can result in the increase of the current response with low detection limit.In this paper different nanomaterial are used as modifiers to fabricate several kinds of proteins modified electrodes with the direct electrochemistry and electrocatalysis of proteins investigated in details. The thesis can be summarized as follows:1. A composite bionanomaterial was prepared by combining chitosan, lithium cobalt oxide (LiCoO2) nanoparticle and hemoglobin (Hb). Then it was further applied on the surface of a carbon ionic liquid electrode (CILE) fabricated with1-hexylpyridinium hexafluorophosphate (HPPF6) as the modifier. Ultraviolet visible and Fourier transform infrared spectroscopic results indicated that Hb molecules in the composite film retained the native structure. The direct electrochemical behaviors of Hb in the composite film were further studied in pH3.0phosphate buffer solution (PBS). A pair of well-defined and quasi-reversible cyclic voltammetric peaks of Hb was obtained with the formal potential (E0’) at-0.297V (vs. SCE). The fabricated Hb sensor exhibits excellent good bioelectrocatalytic activity towards TCA in the range from2.0to15.0mmol/L with a detection limit of0.04mmol/L (at S/N=3).2. A novel, biocompatible sensing strategy based on Cu3Mo2O9nanosheets for immobilizing the Hb molecules was adopted. Direct electron transfer and bioelectrocatalytic activity of Hb after incorporation into the composite film were investigated. UV-Vis and FT-IR spectroscopy confirm that Hb retained its native structure in the composite. A pair of inreversible redox waves of Hb appeared on the cyclic voltammograms, which indicated that the direct electron transfer of Hb was realized on the modified electrode. The Hb modified electrode exhibited good electrocatalytic activity toward to the reduction of trichloroacetic acid (TCA) in the range0.5-36.0mmol/L.3. CILE was further in situ electrodeposited with graphene (GR) and gold nanoparticles step by step to get a Au/GR nanocomposite modified CILE. Myoglobin (Mb) molecules were further immobilized on the Au/GR/CILE surface with Nafion film to get the modified electrode denoted as Nafion/Mb/Au/GR/CILE. Cyclic voltammetric experiments indicated that a pair of well-defined quasi-reversible redox peaks appeared in pH3.0PBS with the formal potential (E0’) located at-0.197V (vs. SCE), The fabricated Mb sensor exhibits excellent good bioelectrocatalytic activity towards TCA in the range from0.4to20.0mmol/L with a detection limit of0.13mmol/L (at S/N=3).4. Mb was immobilized on the surface of a modified CILE, which was electrodeposited with graphene (GR) and nickel oxide nanoparticles step by step. The modified electrode was denoted as Nafion/Mb/NiO/GR/CILE. Cyclic voltammetric experiments indicated that pair of well-defined and quasi-reversible redox peaks appeared, which indicated that the direct electrochemistry of Mb were realized. The Mb modified electrode exhibited excellent bioelectrocatalytic activity towards TCA in the range from0.69to30.0mmol/L with a detection limit of0.23mmol/L (at S/N=3).