Purification and defect elimination of single-walled carbon nanotubes by the thermal reduction technique

A thermal reduction (TR) technique is used to purify single-walled carbon nanotubes (SWNTs) and to reduce chemical defects from their lattice structure. This technique is mainly comprised of two processes, high-temperature reactions of raw SWNTs in a pressurized hydrogen chamber followed by a slow annealing under vacuum. Analyses by TEM, TGA, XRF, and XRD of SWNT samples before and after the purification reveal that over 90% of the carbonaceous impurities formed during the syntheses of SWNTs (by carbon arc, laser ablation, and HiPCO) are eliminated. Post-purification IR spectroscopic analyses show no evidence of hydrogen in the SWNT samples and AFM studies suggest that the samples contain very few chemical defects. In addition, analyses by TEM and Raman spectroscopy do not reveal any significant structural damage of the SWNTs purified by the TR technique.