Defluorination-assisted nanotube-substitution reaction with ammonia gas for synthesis of nitrogen-doped single-walled carbon nanotubes

Nitrogen-doped single-walled carbon nanotubes (N-doped SWCNTs) were synthesized by reacting fluorinated SWCNTs with ammonia gas at reaction temperatures of 300-600 °C. In the N-doped SWCNTs synthesized at 400 °C (N_400°C-doped SWCNTs), nitrogen atoms were introduced into the nanotube framework at a concentration of 3.04 at.%, the concentrations of the pyridinic-, pyrrolic-, graphitic-, and pyridine-N-oxide-type nitrogen species were 1.22, 1.36, 0.34, and 0.08 at.%, respectively, and their percentages with respect to the total nitrogen species were 40.1, 44.7, 11.2, and 2.6%, respectively. The volume resistivity of films of the N_400°C-doped SWCNTs was 2.3 ± 1.1 Ω · cm, indicating that they can be classified as semiconductors. Finally, it was found that the thermopower of the N_400°C-doped SWCNTs was negative at room temperature in air, indicating that they exhibited n-type conduction.