Chemical surface treatment for highly improved dispersibility of multi-walled carbon nanotubes in water

In order to increase the dispersibility of multi-walled carbon nanotubes (MWNTs) in water without any additives, various acid treatments were used. Generally, acid treatment used to remove or purify carbon nanotubes. MWNTs treated with a mixture of nitric and sulfuric acids showed high dispersion stability by means of UV-visible spectrophotometry and higher crystallinity than other samples. In addition, it was clearly shown that acid treatment efficiently removed the impurities of MWNTs, which was proven by thermogravimetric analysis. In particular, one of functional groups, cyano (C-N) bonding characterized by Fourier transform-infrared after acid treatment were formed the surface of MWNTs.