Electrochemical Characterization And Bioelectrochemical Studies On Nitrogen-doped Carbon Nanotubes

The study of immobilizing biomolecules on the carbon nanotubes and their biochemistry applications are greatly concerned, which shows that CNTs-modified electrode can obviously promote the electron transfer. However, as we know, the surface on the structure of CNTs, including the defect and functioning group, directly affect the electrochemical properties of the nanotubes, such as solubility, and biocompatibility. Recently, some research reported that the structure and electrochemical properties of CNT can be improved by doping other elements ,such as B or N. In this paper, the newly prepared bamboo-like nitrogen doping carbon nanotubes were used as novel nanomaterials for the application in the bioelectrochemical field. In addition, the electrochemical reactivity of electrode modified by carbon nanotubes with different sizes was also assessed and compared.The main results and conclusions are summarized as follows:1. The novel chemically modified electrodes were constructed by casting nitrogen-doped multi-walled carbon nanotube(CNx) on glass carbon electrode. Electrochemical behaviors of CNx modified electrode in K3Fe(CN)6/0.1MKCl were investigated by cyclic voltammetry. And bioelectrocatalysis of dopamine(DA), uric acid(UA), acrobic acid (AA) and NADH were studied at CNx modified glass carbon electrode. The results showed this CNx modified electrodes presented good electrocatalytic behavior to these biomolecules and good selectivity, which can be attributed to the existence of a large amount of active sites on the surface of CNx nanotubes introduced by nitrogen doping .2. The CV results of Mb/ CNx nanotubes modified electrode shows a pair of well-defined, quasi reversible redox peaks centered at approximate–0.33V (vs.SCE) in pH7.0 phosphate buffer solution. It reflects the characteristic of Mb Fe(Ⅲ)/ Fe(Ⅱ) redox couple with fast heterogeneous electron transfer rate. The Mb incorporated into CNx nanotube films exhibits good bioelectrocatalytic activities for the reduction of hydrogen peroxide and nitrite. The results demonstrate that the CNx nanotubes may improve the protein loading with the retention of bioactivity and promote the direct electron transfer greatly. It can be attributed to the existence of a large amount of active sites on the surface of CNx nanotubes and a suitable biocompatible C-N microenvironment introduced by nitrogen doping.3. The electrochemical activity of multi-walled carbon nanotubes(MWNTs) with different sizes, including four different MWNTs with the same length and different diameter, two different MWNTs with the same diameter and different length, has been assessed and compared. The various MWNTs modified electrodes were prepared by immobilizing the suitable amount of MWNTs onto a glassy carbon electrode, and their voltammetric responses to ferricyanide, Uric acid and Dopamine were examined. The corresponding cyclic voltammetric data showed that the electrochemical and electrocatalytic activities are depended on the nanotube length. The electrochemical reactivity of short MWNT(S-MWNT) is better than that of long MWNT(L-MWNT), which may be mainly attributed to the existence of the more open ends of S-MCNT relative to L-MWNT. In addition, the diameter of MWNTs proved to have little effect on the electrochemical reactivity of MWNTs modified electrode.4. The modified electrodes were constructed by casting single-walled carbon nanotube on glass carbon electrode. Electrochemical behaviors of SWNT modified electrode in K3Fe(CN)6/0.1MKCl were investigated by cyclic voltammetry. Furthermore, bioelectrocatalytic of dopamine(DA), uric acid(UA), acrobic acid (AA) and NADH were studied at single-walled nanotube modified glass carbon electrode. The results showed this SWNT modified electrodes also presented good electrocatalytic behavior to these biomolecules.