A simple and highly effective process for the purification of single-walled carbon nanotubes synthesized with arc-discharge

We developed a simple and highly effective process for the purification of single-walled carbon nanotubes (SWCNTs) synthesized with arc-discharge. The new process consists of two steps: (i) ultrasonic filtration of an aqueous acid solution of the SWCNTs, and (ii) heat-treatment at 430 °C for 1 h under a moisture-saturated N2 atmosphere. This simple process results in the remarkably effective removal of impurities such as amorphous carbon, carbon nanoparticles, and metallic catalysts. Further, the whole purification process can be completed within 5 h, which is much faster than conventional acid purification processes, which require 50 h, and much less destructive than other conventional purification methods. In a gram-scale purification, the proposed purification method gave us 150 mg of purified SWCNTs with the purity of 96.2 wt% out of 1.0 g of as-prepared SWCNTs, which corresponds to ∼72% yield as for the initial composition of SWCNTs in the as-prepared soot. Field emission scanning electron microscopy, high resolution transmission electron microscopy, thermogravimetric analysis, X-ray diffractometry, and Raman spectroscopy were used to determine the effects of the new purification process on the SWCNTs.