Simple and Complete Purification of Single-Walled Carbon Nanotube Materials

When used in a variety of projected applications and basic studies, carbon single-walled nanotubes (SWNTs) must be thoroughly purified. A three step purification process producing materials with >98 wt.-% purity is described. A dilute nitric acid reflux digests, functionalizes, and redistributes the non-nanotube carbon fractions to form a uniform and reactive coating on the SWNTs that can be removed by oxidation. Purity evaluations by Raman spectroscopy, inductively coupled plasma spectroscopy (ICPS), and thermogravimetric analysis (TGA) illustrate that very few tubes are consumed. The use of TGA and ICPS defines a technique by which the components in raw and process materials may be accurately determined on a weight percent basis.