Self-organized and reversibly dispersible pellets of multi-walled carbon nanotubes

Hydrophobic surfaces of multi-walled carbon nanotubes (CNTs) were oxidized by boiling a mixture of CNTs and concentrated acid. A self-organized pellet which can be reversibly dispersed was produced by dehydrating the oxidized CNT solution. Scanning electron microscope pictures showed that the pellet consisted of highly aligned nanotubes. Fourier transformation infrared and X-ray photoelectron spectroscopy indicated that oxygen-containing surface groups were introduced during the acid oxidation. Although an increased number of defects was shown by Raman spectroscopy, X-ray diffraction indicated that graphene layer organization remained after treatment. Thermal stability of treated CNTs was investigated and comparisons between pristine, treated, and heated CNTs were made. This well-packed and soluble pellets can provide ideal samples to study bulk CNT nanostructured materials and CNT composites.