Nondestructive purification of single-walled carbon nanotube rope through a battery-induced ignition and chemical solution approach

A two-step method for the purification of single-walled carbon nanotube (SWCNT) rope containing substantial catalyst particles embedded in carbonaceous shells was developed. The first step was the triggering of rope ignition using a 9-V battery, which resulted in pre-oxidization of the carbon shells on the Fe₃C catalyst and oxidation of the exposed Fe₃C to form Fe₂O₃. In addition, SWCNTs with open-end structures due to ignition-induced cutting remained. In the second step, both oxalic acid (H₂C₂O₄) and hydrochloric acid (HCl) were used as the reactants to remove the Fe₂O₃ particles. No damage on the SWCNT walls after H₂C₂O₄ or HCl purification was found. In addition, adsorption of H₂C₂O₄ was also found on the H₂C₂O₄ purified SWCNT rope and it can be effectively removed by heating the rope at 200 °C in vacuum for 40 min. Samples were characterized by SEM, TEM, Raman spectroscopy, TGA, FTIR, XPS, and UV-Vis-NIR.