  We have studied the visible and infrared radiation emitted by multi-walled
carbon nano-tubes of different diameters when exposed to 2.45 GHz microwaves. A
comparison of the spectra suggests that multi-walled carbon nano-tubes with
larger diameters emit radiation of greater intensity than those with smaller
diameters. Furthermore, the multi-walled carbon nano-tubes continued to emit
visible and infrared radiation over the course of several microwave-irradiation
cycles, with no degradation in the intensity of the emitted radiation. A
comparison of Raman D- to G-band peak-intensity ratios revealed that
microwave-irradiation did not significantly impact the multi-walled carbon
nano-tubes' defect densities. The results of our experiments suggest that
multi-walled carbon nano-tubes may have the potential for use in lighting
technologies, and that ohmic heating caused by the polarization of the
multi-walled carbon nano-tubes in the microwave field is likely responsible for
the observed emissions of visible and infrared radiation.
