US Patent 7115864 - SWNT Purification Using Heating Under Oxidizing Conditions

http://www.freepatentsonline.com/7115864.pdf

During fabrication procedures of single walled nanotubes often amorphous carbon particles will be formed among an aggregation of the nanotubes. This patent from Smalley's group at Rice (with priority all the back to 1996) claims a basic method of purifying the nanotubes. Claim 1 reads:

1. A method for purifying single-wall carbon nanotubes comprising: a) providing a mixture containing single-wall carbon nanotubes and at least one other reaction product formed in a method for producing single-wall carbon nanotubes; b) heating the mixture under oxidizing conditions; and c) recovering a purified product having a higher concentration of single wall carbon nanotubes than the mixture.