US Patent 7868333 - Demetallization of CNTs

http://www.freepatentsonline.com/7868333.html

The fabrication processes for carbon nanotubes usually results in metallic residue that needs to be removed prior to use of the nanotubes. This patent from E.I. du Pont teaches a purification technique which removes the metallic residue without damaging or oxidizing the nanotubes. Claim 1 reads:

1. A process comprising:

a) forming a first suspension of carbon nanotubes containing metal residues in a first solvent;

b) contacting the first suspension with an active metal agent to form a second suspension of carbon nanotubes containing metal residues;

c) contacting the second suspension with carbon monoxide gas to form carbon monoxide-treated carbon nanotubes; and

d) isolating the carbon monoxide-treated carbon nanotubes;

wherein steps (a), (b) and (c) are performed in an airless atmosphere.