Fast microwave-assisted purification, functionalization and dispersion of multi-walled carbon nanotubes

Microwave-assisted purification, chemical functionalization and dispersion of multi-walled carbon nanotubes (MWNTs) are reported. To prevent sidewall functionalization, removal of residual catalyst was carried out using weak, dilute acids and complexing agents. Further covalent derivatization by attaching hydrophilic groups to the sidewall improved aqueous dispersibility to reach 1 mg/mL in deionized water and 0.5 mg/mL in ethanol. Oxidized MWNTs containing -COOH could be used for further functionalization, such as, amidation. The MWNTs were found to be less reactive and had lower solubility than the single-walled carbon nanotubes (SWNTs). Electron microscopy, Fourier Transform Infrared Spectroscopy, Thermogravimetric Analyses and Atomic Absorption spectrometry studies were used to characterize the aimed-MWNTs.