Ab Initio Study of the Size-Dependent Effect on the Covalent Functionalization of Single Walled Carbon Nanotubes with Hydroxyl, Amine and Carboxyl Groups

We have investigated the sidewall functionalization of several (n, 0) zigzag Single Wall Carbon Nanotubes (SWNTs) by the hydroxyl, amine and carboxyl groups with n varying from 5 to 23 by using ab initio calculations. The results show that the stability of the OH, NH2 and COOH groups depends on the size of carbon nanotubes. The binding energies and structural properties have been determined and discussed. A transition has been observed when nanotube diameter is near 8 angstrom. This behavior is confirmed by electronic structure results. As a rule, the functionalization of SWNTs can be enhanced in the case of tubes with small diameters. The study of carbon nanotubes with different diameters is relevant to the full understanding of their properties.