UV-ozone treatment of multi-walled carbon nanotubes for enhanced organic solvent dispersion

Abstract

Treatment of multi walled carbon nanotubes (MWNTs) with UV-ozone (UVO) under ambient conditions has a dramatic effect on the nature of the surface oxidation, leading to the production of quinines, esters, and hydroxyl functional groups. Using a 60 min exposure time, the solubility in polar organic solvents was increased by as much as 320%, compared to raw carbon nanotubes (CNTs), which is comparable to the effect of a vigorous acid treatment. Interestingly, the UVO exposure had no effect on the aspect ratio of the CNTs. The results of thermogravimetric analyses suggest that UVO treated CNTs have almost the same thermal stability as raw CNTs, suggesting that an insignificant number of defects are produced during the ozonation procedure. Moreover, surface resistance measurements showed that, due to their preserved higher aspect ratio, UVO modified CNTs induced a higher electrical conductivity in polymer matrices. These findings clearly demonstrate that a solvent-free UVO treatment can produce solvent-dispersible CNT powders without accompanying morphological defects, offering the potential for producing a versatile CNT solution.