Investigation On The Electrochemical Properties And The Applications Of Carbon Nanotubes

Carbon nanotubes have attracted the attention of many scientists worldwide. The small dimensions, strength and the remarkable physical properties of the structures of carbon nanotubes make them a very unique material with a whole range of promising applications. Depending on their atomic structure, carbon nanotubes behave electrically as metal or as a semiconductor. Their subtle electronic properties suggest that carbon nanotubes have the ability to promote electron-transfer reactions when used as an electrode in chemical reactions. But as a nanotube is such an unusual macromolecule, it leads to indissolubility and chemical reaction cannot occur. However, chemical reactions might happen on nanotubes when some changes in the structure of nanotubes take place and some active functional groups appear on it, such as hydroxyl and carboxyl. Electroanalytical applications have been found for determining some biomolecules recently, but the carbon nanotubes are only regarded as a kind of modified material to some traditional electrodes, such as, casting carbon nanotubes on Pt, Au and glassy carbon electrode or intercalating carbon nanotubes on graphite electrode. If carbon nanotubes were considered as a potential electrode material (not only modifying material), systematical investigations of the properties on the basis of carbon nanotube electrodes are needed.The chemical modification of carbon nanotubes was carried out using different chemical treatment methods. These modified carbon nanotubes were characterized by TEM image and FTIR spectra. The properties of the conductance and electrochemistry of the carbon nanotube film electrodes are measured by thermal resistivity and cyclic voltammetry experiments. The results showed that two important factors controlled their electrochemical properties: one is the active functional group; another is activation energy of the carbon nanotube film. Among these measurements, the two factors were matched best by 10 minute nitric acid treated carbon nanotube electrode; and this electrode showed the optimal electrochemical behaviors: small background current, flat wide potential windows, well-defined quasi-reversible cyclic voltammetric responses for the familiar redox couples of Fe3+ / Fe2+, Fe(CN)63- / Fe(CN)64- and Hydroquinone / quinone, and rapid electronic transfer constants. Such properties suggest that the carbon nanotube electrode is a novel and promising electrode material.The carboxyl-modified carbon nanotube electrode was applied in bioelectroanalysis. The results showed that the electrode had strong electrocatalysis to dopamine, epinephrine, sulfadiazine and ascorbic acid in comparison with the glass carbon electrode, where the catalysis greatly raised the oxidation currents of dopamine, epinephrine, sulfadiazine; and negatively shifted oxidation potential of ascorbic acid. These behaviors are due to the porous and tubular structure of carbon nanotubes and the active groups on the end of carbon nanotubes. Trace dopamine or epinephrine in the presence of a large excess of ascorbic acid has been determined selectively with high sensitivity at the carbon nanotube electrode, and the limited determination reached 10–7 mol L-1; and satisfactory results of the detection were obtained for the low level sulfadiazine at the carbon nanotube electrode.The complete electrochemical combustion toxic organic compound of phenol into CO2 or elimination of toxic abiotic compounds of azide and hydrazine was found at low level of concentration on the carboxyl modified carbon nanotube electrode, which might be used in electrochemical treatment of toxic components in wastewater. Due to the carboxyl modification of the carbon nanotubes, a large quantity of hydroxyl radicals existed in the electrode, which provided the condition of the electrochemical combustion; and because of the porous tubule of the structure of the carbon nanotube, the molecule or ion in solution could easily pass the tubes and reach the sites of the hydroxyls. The conglomeration of such nanoscale struct...