A multi-step treatment to effective purification of single-walled carbon nanotubes

An efficient procedure for the purification of single-walled carbon nanotubos (SWCNTs) based on chemical treatment and physical separation is proposed and studied step-by-step by high-resolution transmission electron microscopy, thermogravimetric analyses, and nitrogen adsorption techniques. Impure raw samples prepared by the arc-discharge method containing SWCNTs, amorphous carbon, graphitic particles, carbon shells, metallic catalysts, and fullerenes were employed in this study. The procedure reported herein was used to remove each impurity of the sample in a step-by-step way. Gas-phase oxidation and the popular oxidation by heating in nitric acid were avoided to minimize damages to structure of the SWCNTs and to keep eventual chemical modifications of sample to a minimum. This new procedure is efficient and appropriate for the obtention of highly pure SWCNTs with minimal damage to the walls and minimal modification in the length of the tubes. The amount of each kind of impurity present in the raw material yielded in an arc-reactor was quantitatively estimated. Results of specific surface area and t-plots are also discussed.