Hydrothermal treatment to prepare hydroxyl group modified multi-walled carbon nanotubes

Multi-walled carbon nanotubes (MWNTs) bearing hydroxyl groups (MWNTols) on the exterior surface have been synthesized by an alkaline-mediated hydrothermal treatment of MWNTs under autogenous pressure at 180 °C. X-Ray photoelectron spectroscopy shows that the content of hydroxyl groups increases with the concentration of sodium hydroxide utilized. FT-IR spectroscopy shows that hemiketals were incorporated into the structure of MWNTols. The prepared MWNTols are highly soluble in polar solvents such as water, methanol, butanone and tetrahydrofuran, to give robust stable black solutions. Transmission electron microscopy reveals that the diameter, length and morphology of MWNTs are well retained in MWNTols. MWNTols are redox active on their exterior surface, where hydroxyl groups, upon reaction with Ce(IV) ions, transform to radical species and initiate polymerization of N-isopropylacrylamide (NIPAM).