DFT Study of Adsorption of Methyl Red on the Surface of Pure, Pyrrolidine-Functionalized, Silicon- and Germanium-Doped Zigzag (6,0) Carbon Nanotubes

In the present study, the adsorption of methyl red on the surface of pure zigzag (6, 0) carbon nanotube was investigated using the density functional theory calculations. The role of the pyrrolidine functional group, as well as doped-silicon and germanium atoms in the adsorption of the methyl red was investigated. The natural bond orbital and the quantum theory of atoms in molecules calculations were performed for further understand of the intermolecular interactions between methyl red and the studied nanotubes. The values of adsorption energy and its negative sign indicate that the adsorption of methyl red on the functionalized and doped derivatives of zigzag (6, 0) carbon nanotubes is favorable. According to the results, the pyrrolidine functionalized zigzag (6, 0) carbon nanotube, E-ads = -0.57 eV, has a better performance for methyl red adsorption.