Surface oxidation and effect of electric field on dispersion and colloids stability of multiwalled carbon nanotubes

Chemical functionalization is a procedure to oxidize the surface of materials. Multiwalled carbon nanotubes (MWCNTs) were purified and functionalized using oxidizing mixture acids (sulfuric and nitric acids). The effect of purification and functionalization on the decrease of MWCNTs length and solubility in polar solvents was studied. The length of MWCNTs decreased when the purification and functionalization time was increased. The functionalization of MWCNTs was confirmed by Raman spectroscopy measurements. It was found that, by functionalization the solubility and colloidal stability of MWCNTs were increased in polar media like water and methanol. We found also dispersion status of functionalized MWCNTs in water is evidently improved by applying an AC electric field of 25 V at low frequency and proper applying time.