Structural and electronic properties of group-IV tin nanotubes and their effects on the adsorption of SO2 molecules: Insights from DFT computations

Abstract

The structural and electronic properties of pristine and SO2 adsorbed buckled tin nanotubes were investigated using density functional theory calculations. The effects of SO2 gas adsorption on the electronic structure of the nanotubes were analyzed in detail. SO2 molecule was initially positioned on the armchair and zigzag stanene based nanotubes with orientations through both interacting sulfur and oxygen sites. The results suggest that the considered armchair nanotubes have direct bandgaps at the K point, indicating the semiconductor characteristics of these nanotubes. Thus, these nanotubes are efficient candidates for gas sensing applications. Moreover, the considered (9, 0) and (10, 0) zigzag nanotubes also exhibit semiconductor behavior. Among the armchair nanotubes, the highest (most negative) adsorption energy belongs to (8, 8) armchair nanotube, which indicates that SO2 interaction with (8, 8) nanotube is energetically most favorable. The adsorption energy slightly increases with increasing the nanotube diameter. Besides, the adsorption of the SO2 molecule on the nanotube surface through its oxygen atoms is more favorable in energy than that through its central sulfur atom. The projected density of states of the interacting tin and oxygen atoms show the formation of chemical bonds between these atoms, as evidenced by the accumulation of electronic density at the middle of the newly formed bonds. Based on charge density difference calculations, we found the charge accumulation on the adsorbed SO2 molecule, which represents that SO2 acts as a charge acceptor.