Oxygen functionalization of multiwall carbon nanotubes by Ar/H2O plasma treatment

To increase the applicability of multiwall carbon nanotubes (MWCNTs), oxygen-containing functional groups were introduced on the surfaces of MWCNTs by using microwave-excited Ar/H2O surface-wave plasma. X-ray photoelectron spectroscopy and Raman spectroscopy were used to determine dependencies of Ar/H2O gas partial pressure, treatment time and microwave power. The oxygen functionalization of MWCNTs by plasma can be achieved very rapidly, about 10 min. The C–O and O–C═O fractions firstly increase and then decrease with increasing Ar partial pressure. The C–O and O–C═O fractions increase with increasing microwave power from 400 W to 700 W. A slight increase of the R (ID/IG ratio) value for the treated MWCNTs indicated disordering in the surface microstructure of MWCNTs coincident with the introduction of surface oxygen. The oxygen-containing groups introduced on the surfaces of MWCNTs by plasma treatment are hydrophilic. The dispersion of plasma treated MWCNTs is therefore improved.

Research Highlights
► The oxygen-containing functional groups were introduced on MWCNT surfaces by plasma treatment.
► The C-O and O-C=O fractions increases and then decreases with increasing Ar partial pressure.
► The C-O and O-C=O fractions increases with increasing microwave power from 400 to 700 W.