Gas adsorption on inorganic nanotubes can be considered as a great issue for both essential research and applied application of this kind of nanotubes. The adsorptive characteristics of SWNTs in the gas phase caused their use as gas sensors of pollutant gases, storage of fuels, and removal of hazardous pollutants from gas streams. With the successful synthesis of silicon nanotubes (SiNTs), a few attentions has been paid to their application in hydrogen storage studies. Compared to carbon, silicon has more electrons in the outer shells, therefore, SiNT may exhibit a stronger van der Waals attraction to nonpolar gases than CNTs. However, the interaction between SiNTs and other molecular gases than H2 has not been investigated. Therefore, in this study the adsorption of carbon monoxide, oxygen, nitrogen and methane molecules with both inside and outside of armchair (5,5) SiNT, were investigated by using density functional theory method.
