Investigation of photo-induced diffusion of oxygen into carbon nanotube for oxidation process

A controlled and less destructive way of purification of as-grown carbon nanotube (CNT) is a challenging task for the scientific community. A new approach for oxidation of as-grown CNTs using ultraviolet (UV) light lamp is investigated in this paper. For this purpose, the experiment was conducted in a UV lamp chamber consists of a layer of reflective aluminum foil inside to ensure the entire sample would have an even exposure to UV. The experiments were performed under ambient condition. In this study, we vary the exposure time of oxidation. The removal of non-nanotube material after UV light exposure is confirmed by field emission scanning electron microscopy and Raman spectroscopy. Raman spectra show that D band becomes narrow which is consistent with highly purified nanotube. We observed that the intensity of G and D* bands increased rapidly with increasing the UV light exposure time for oxidation. Intensity ratio I D*/I D increases continually with increasing the oxidation time which confirms the reduction of impurities from the MWNTs. Fourier transform infrared spectroscopy confirms the presence of defect sites where some oxygenated functional groups are attached.