Adsorption of NO2 molecules on single-walled carbon nanotubes: A Computational Electronic Energies and Relative Stabilities Study

The combining processes of adsorption on all different sites of surface and open ends of SWCNTs are mainly exothermic and the relaxed geometries are generally less stable. The obtained results reveal that the interaction between NO2 molecule and the open-ended armchair (4, 4) SWCNT is weak and may be considered as chemisorption process.. In the contrary, the interaction between NO2 molecule and the open ended zigzag (5,0) SWCNT is rather strong and can be concluded as a physisorption process. The chemisorption of NO2 molecule has appreciable adsorption energy. This may be attributing to electronic configuration of p electrons on the surface and carbon doped atoms on the open ends of these models of SWCNTs. Thus, the adsorption of NO2 molecule over the surface and on the open ends of the SWCNTs would affect their electronic conductance and mechanical properties, which could serve in the gas sensor signal. It can be concluding that the remarkable charge transfer from SWCNTs to NO2 molecule falls out due to the decrease of the gap of HOMO–LUMO energy. Keywords: Physisorption, chemisorptions, conductance, energy gap, HOMO – LUMO energy.