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 degrees C for 1 h under a moisture-saturated N-2 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 similar 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. (c) 2009 Elsevier Ltd. All rights reserved.