Fabrication, Characterization And Application Of Carbon Nanotubes Electrode In Bioelectrochemistry

The electrochemical characteristics of graphite electrode modified with carbon nanotube were investigated. Extensive studies were made on the applications of the electrodes to bioelectrochemistry and analytical chemistry for NAD(P)H, Hb, HRP, GOx. The method presented here can be easily extended to immobilize and obtain the direct electrochemistry of other redox enzymes or proteins. The main research works are expressed as follows:1. The carbon nanotube electrode was fabricated, and characterized with FT-IR spectroscopy, Raman spectrum, X-ray powder diffraction (XRD), scan electron microscopy(SEM), and Transmission electron microscopy (TEM); The electrochemical behaviors of CNT/GC electrode was studied by Cyclic voltammetry method using probe molecule Fe(CN)6 ".2. NADPH can be directly oxidized on the CNT/GC electrode at low potential. The oxidation peak of NADPH was at bout -4 mV under 10 mV/s scan rate, which reduce excel potential by 720 mV; The perfect linear range between the oxidation peak current and the concentration of NADPH was between 5 x10-7 mol/L and 1 x 10-3 mol/L, with the lowest monitor limitation of 1 x 10-7 mol/L NADPH.3. Hb and HRP was immobilized on the CNT/GC electrode using nation as binder. The results showed CNT has promotion effects on the direct electron transfer of Hb and HRP. The direct electron transfer rate of Hb and HRP was both greatly enhanced after it was immobilized onto the surface of CNT. Cyclic voltammetric results showed a pair of well-defined redox peaks, which corresponded to the direct electron transfer of Hb (or HRP). The electrochemical parameters such as apparent heterogeneous electron transfer rate constant (ks) were estimatedrespectively. The dependence of E01 on solution pH indicated that the direct electron transfer reaction of Hb (or HRP) is a one-electron transfer coupled with a one-proton transfer reaction process. The experimental results also demonstrated that the immobilized Hb and HRP retained their bioelectrocatalytic activity to the reduction of H2O2.4. CNT have promotion effects on the direct electron transfer of glucose oxidase (GOx), which was immobilized onto the surface of CNT. Cyclic voltammetric results showed a pair of well-defined redox peaks, which corresponded to thedirect electron transfer of GOx( E01= -0.466 V, pH 6.9). Apparent heterogeneouselectron transfer rate constant (ks) were estimated. The dependence of E01 on solution pH indicated that the direct electron transfer reaction of GOx is a (2e-2H+) transfer reaction process. The experimental results also demonstrated that the immobilized GOx retained its bioelectrocatalytic activity to the oxidation of glucose, suggesting the electrode may find use in biosensors or biofuel cells (for example, it may be used as a bioanode in biofuel cells).5. A method for fabrication of the ordered carbon nanotube (OCNT) film, which was template synthesized within the highly ordered pores of a commercially available alumina template membrane , modified glassy carbon electrode ( OCNT/ GC) was established. The OCNT/GC electrode showed excellent electrocatalytic activity toward dopamine electrochemical reaction without introducing any electro-chemically active group into CNT film or activating the electrode electro-chemically. DA undergoes ideal reversible electrochemical reaction on OCNT/GC electrode at low scan rate with an excellent stability and reproducibility. NADH can be directly oxided on CNT/ GC electrode with the oxidation peak potential of - 4 mV (10 mV/s), which is lower than ever before. The CNT/ GC electrode might be used in biosensors because the highly ordered CNT may present steric effect on more efficient redox reactions of biomolecules.