Theoretical Study of (CO) _{n=1, 2} Adsorption on the (6,0) Zigzag Single-walled Carbon Nanotube

Abstract

The behavior of the carbon monoxide and carbon dioxide [(CO) _{n=1, 2}] adsorbed on the external surface of (6,0) zigzag single-walled carbon nanotube (SWCNT) was studied by using density functional calculations. Parallel and perpendicular bonding geometries of CO and CO₂ adsorbed on the (6,0) CNT surface were considered. Geometry optimizations were carried out at the B3LYP/6–31G* level of theory using the Gaussian 98 suite of programs. We present the nature of the (CO) _{n=1, 2} interaction in selected sites of the nanotube. Our results show that the pristine carbon nanotubes cannot significantly detect (CO) _{n=1, 2} molecules. The calculated binding energy for CO in O-down configuration is higher than that in C-down, and the values of dipole moments for the most stable configuration of CNT-CO showed slight changes with respect to the pristine models. The calculated results showed that the C–O bond lengths remain almost unchanged in the most stable configuration of (CO)_{n=1, 2} –CNT. The calculated BE for CO₂ in perpendicular orientation is higher than that in parallel orientation. Furthermore, the adsorption of CO and CO₂ on the CNT are not changed the band gap and electrical conductance of the pristine CNT. The DOS and HOMO and LUMO for the CNT models showed that the pristine CNT cannot significantly detect CO and CO₂ molecules.

Keywords:

• Carbon nanotube
• adsorption
• DFT
• energy gap
• binding energy
• HOMO
• LUMO