Comparative analysis of various methods of purification of single-walled carbon nanotubes

A comparative analysis of the purification methods for single-walled carbon nanotubes (SWNTs) obtained by electric-arc-discharge synthesis is carried out. The purification methods include air oxidation of the initial material at various temperatures, treatment and/or oxidation in solutions of inorganic acids, microfiltration of the suspension of the initial and/or oxidized materials, and various combinations of these methods. The purity of the SWNTs obtained is determined with the help of Raman spectroscopy. It is shown that the best results can be obtained using a purification method including the following consecutive stages: treatment and oxidation of the initial material in nitric acid, microfiltration of the suspension of the oxidized material in aqueous solutions of surface-active substances through track membranes, drying, air oxidation, and vacuum annealing at various temperatures. The purity of the SWNTs obtained attains 70–80%.