| In recent years, increasing research interest has been focusing on carbon nanotubes, owing to their significant mechanical strength, high surface area, excellent electron transmission and good chemical atability. Because of the enique structural characteristics, it is very prone to produce defects, for example, high-energy electron radiation or ultrasound will make multi-wall carbon nanotubes forme more dislocation and defects. Therefore, compared to other variations, graphite carbon nanotubes have stronger and more flexible response to the active site, having a unique electrical properties. This paper is divided into the following three parts:For the first part, we have done a more detailed introduction from the structure, nature, characterization and its applications of the carbon nanotubes. So we put forward the idea of this paper.For the second part, the modified electrode was made by the drop method. We use it to study the oxidation of ascorbic acid separately from the electrolyte pH, the concentration of carbon nanotube dispersion, the dispersion of carbon nanotubes coated droplet volume, etc.,systemly. The results show that acidic environment of PH value is 5.8, in the concentration of 1mg/3ml of carbon nanotube dispersion, ascorbic acid redox reaction will take place on the electrode surface. However, when the drop is greater than 4μL, the occurrence of ascorbic acid at the electrode surface redox reaction will be hindered.For the third part, we have used TPP(SH)2, with self-assembly techniques, preparing modified electrode and used many electrochemical methods(CV,EIS,SECM) to characterize this modified electrode. The results indicate that at the surface of gold electrode can be successful to prepare modified electrode with a layer of porphyrin assembly. This electrode can be used to separated ascorbic acid from dopamine. Within the linear range of ascorbic acid concentration (from 1.0×10-3M to 5.0×10-6M), concentration and peak current of ascorbic acid wear a good linear relationship,and the detection limit can reach to 1.0×10-7M.
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