Study On Functional Carbon Nanotubes And Relative Experiments

Since carbon nanotubes were first discovered in 1991, they have generated great interests among scientists worldwide. Carbon nanotubes (CNTs) can be either metallic or semiconducting depending on their chiralities. The unique structure, mechanical and electronic properties of both the single-walled and multi-walled CNTs have made them very promising materials for a wide variety of applications. In this study, we experimentally studied the electrical,piezoresistive and electrochemical properties of CNT films.We firstly investigated the chemical modification of CNTs with different acid treatments. The modified CNTs were characterized by TEM and FTIR. It was found that the end of CNTs were opened and connected with carboxyl groups. The change of the resistance ratio of the CNT films (with different diameters) as a function of temperature was measured. The result showed that all samples resistance ratio dropped when the temperature was increased, indicating a nonmetallic characteristic. An electrical model was also built to account the activation energy of the CNT film. The result indicated that the activation energy of the CNT film was reduced with increased CNT diameter The piezoresistive properties of CNT film were investigated in our experiments, we found that the resistance change of chemical treated MWNT films exceeded that of pristine MWNT films in the same strain. For the chemical treated MWNT films with different diameters, the resistance change was more pronounced for smaller diameter CNTs. The relationship of the gauge factor and strain did not show an apparent trend.For pristine MWNT films, the gauge factor increases sharply at first and then decreases with increasing microstrains. However, for chemical treated MWNT films the gauge factor exhibits an increase with increasing microstrains. The gauge factor of both pristine and chemically treated CNT films shows a very strong increase trend as the temperature increases. In addition, the size-dependent piezoresistive effect of MWNT films was investigated. We found that the films with smaller diameter exhibited better performance in piezoresistive effect than the films with larger diameter. The cause of the stress-induced resistance in the films has been discussed in detail.The carboxyl-modified CNT of N-Doped was obtained by nitric acid treatment. The electrochemical properties of CNT film electrodes were controlled by two important factors: one was the activation energy of the CNT film; the other was the active functional group. Because of porous structures of CNTs and the active groups at the end of CNTs, CNTs can be used as the excellent catalyst for the oxidation of dopamine, which can also be used to determine dopamine in the presence of a large excess of ascorbic acid with high sensitivity and selectivity.