MOLECULAR AND ELECTRONIC STRUCTURES OF DEFORMED SINGLE-WALLED CARBON NANOTUBES AND THE ADSORPTION OF DIVALENT METAL IONS ON GRAPHENE OXIDE SHEET

Abstract

The graphene studies are divided into two parts, a single-walled carbon nanotube (SWCNT) and graphene oxide (GO) sheet. Firstly, the molecular and electronic properties of SWCNTs can be modified by deforming their structures under high pressure. The aim of this study was to investigate the energy band gap using quantum calculations, in relation to molecular structures of armchair and zigzag SWCNTs of various sizes and shapes deformed by applied forces. To model an increase in pressure, the degree of flatness (eta) of the SWCNTs was adjusted. From obtained results, with increased eta values in all studied SWCNTs, the bond lengths at the flattened region were dramatically lengthened, while those at tube edge region were slightly decreased. As a function of the mechanical deformation, an electronic band gap is reduced leading to a change of semiconductor-metallic property for armchair SWCNTs. On the other hand, an electronic band gap is enhanced leading to a change of metallic-semiconductor property of zigzag SWCNTs. These results may contribute to a more refined design of new nano-electronic devices. Secondly, the adsorptions of divalent metal ions (Cd2+, Cu2+, Hg2+and Zn2+) on GO sheet with some functional groups, including hydroxyl, epoxy, carbonyl and carboxyl groups, were studied by density functional theory (DFT). From the binding energies of these divalent metals on the GO surface, the adsorption efficiency of metal ions can be ordered as Cu2+ > Hg2+ > Zn2+ > Cd2+. Moreover, we found that the divalent metal ions likely interacted between the two epoxy groups. Understanding the behavior by which divalent metal ions adsorb on the GO surface it would be useful to design effective controls of the heavy metal pollution in industrial waste.