Effect On The Electronic Property Of Carbon Nanotube Grafted By Functional Groups Or Been Doped

The super high strength, ductility, nanometer scale and large aspect ratio of carbon nanotubes (CNTs) make it an ideal reinforcement additive for composites. Also, the good electrical conductivity, high thermal conductivity, good thermal and chemical stability of CNTs could make the composites versatile. Surface decoration by grafting carboxyl & hydroxyl groups on CNTs are often applied to achieve special functionality in the preparation of CNTs composite, Nano-device and Nano-biology area. In this paper, we have studied the effect of grafted groups on electrical properties of CNTs, which is theoretically of great importance.Based on the density-functional theory and the first-principle method, the electronic distribution and the density of states of the armchair (5,5) and zigzag (8,0) and (9,0) single-walled carbon nanotubes grafted by carboxyl or hydroxyl are calculated. A geometry optimization of SCNTs is performed by using BLYP function in DMol3 program, then, the variations of electronic distribution and DOS are calculated by adopting the DMol3 and CASTEP program. It has been found that the electronic structure of the grafted SCNTs changes significantly, namely, the electron density of states near Fermi level, the delocalized degree of the highest occupied molecular orbital, and accordingly the transport properties of SCNTs decreased as the number of hydroxyl functional groups grafted increased.Although the transportation ablity of SCNT decreases no matter what groups (carboxyl or hydroxyl) are grafted on its surface, the decreased scope is different. The effect on the density of state of hydroxyl is stonger than that of carboxyl, and the density of state for armchair CNT decreases faster than zigzag CNT by the grafted functional group.The investigation of the fluorine doping effect on electrical performance of CNTs has been conducted. Results indicate that the absolute value of Fermi energy decreases for three kinds of CNTs doped with fluorine in the the form of replacement, which is beneficial for field emission. Difference in extent of the Fermi energy and decrease of band-gap energy for three kinds of CNTs show that CNT with one end open is favorable for the preparation of field emission electrode.