An efficient strategy for the purification of cloth-like single walled carbon nanotube soot produced by arc discharge

High purity single walled carbon nanotubes (SWCNTs) were prepared from arc discharge produced cloth-like soot by a new purification strategy, in which liquid oxidation and steam oxidation were combined with a freeze-drying process to remove the metallic and carbonaceous impurities. The process gives a product of >98% purity, which is acquired from a gram-scale dirty raw soot with an overall yield of ∼75% of the SWCNTs. The purity of the samples was characterized by thermogravimetric analysis, scanning and transmission electron microscopy, Raman and Vis–NIR spectroscopy, and magnetometry. A highly pure SWCNT sample with relative purity of 170.4% and IG/ID value of 78.92 is achieved. Experiments showed that HNO3/HCl refluxing combined with freeze-drying is the key process that renders the crude SWCNTs hydrophilic with a large surface area, and thus remarkably increases the efficiency of the steam treatment to remove most of the carbonaceous impurities.