Defect-induced chemisorption of nitrogen oxides on (10,0) single-walled carbon nanotubes: Insights from density functional calculations.

The interactions of NO(x) (x=1,2,3) with the defective semiconducting (10,0) carbon nanotubes were studied by the density functional theory. Optimized geometries, binding energies, and electronic structures of the NO(x)-adsorbed nanotubes were determined on the basis of calculations. Effects of the defect density and the electric field on the binding energy and charge transfer have been investigated. In sharp contrast with the case of perfect nanotube, the adsorption of NO(x) at the defect site of (10,0) tube is generally chemical, and after the chemisorption of one NO(2) or one NO(3) the carbon nanotubes with various defects behave as conductors, while the consecutive adsorption of the second NO(2) or the second NO(3) makes these tubes become semiconductors again. Calculations show that the NO(2) adsorption at a topological defect is a barrier-free process, while the NO(3) adsorption experiences a barrier due to transition of the pi<-->s electronic configuration of the NO(3) moiety.