Nitrogen doping of CVD multiwalled carbon nanotubes: Observation of a large g-factor shift

► High quality nitrogen doped multiwalled carbon nanotubes were synthesized using the floating catalyst CVD method. ► Systematic ESR measurements of the carbon products produced, in the temperature range of 293-400 K showed line widths that were in general very large ∼ kOe. ► A large g-factor shift in samples of N-CNTs from that of the free electron g-factor was observed. Further, the shift increased with increasing temperature. The large g shift has been analysed in terms of Elliott-Wagoner and Bottleneck models. ► The temperature dependence of the g shift in the N-CNT samples rules out the Elliott-Wagoner type spin-orbit coupling scenario. ► The large g shift and temperature dependence can be qualitatively explained in terms of Bottleneck model.