Water-Dispersible Multiwalled Carbon Nanotubes Obtained from Citric-Acid-Assisted Oxygen Plasma Functionalization

A new and safe method has been developed to functionalize multiwalled carbon nanotubes (MWCNTs) with fewer surface defects, which significantly increases their dispersibility in water. MWCNTs are pretreated in pure ethanol by a supersonic homogenizer. Then, the mixture is dried and soaked in weak citric acid solution. Finally, the MWCNTs in the citric acid solution are treated with radio frequency (13.56 MHz) oxygen plasma. As a result, many carboxyl functional groups are attached onto the MWCNT surfaces and stable dispersion of the MWCNTs in water is obtained. The treatment conditions are optimized in this study.