How do you process the nanotubes?

Singlewall nanotube – SWNT
Multiwall nanotube – MWNT

When the material is made (as-produce) the nanotubes comes straight out of the reactor with the approximate concentration of 95% MWNT (90% in the case of SWNT) nanotube vs. non-nanotube material. These nanotubes are then processed and purified. This step yields an increase in purity of the tubes which are sold as “Purified Open Material”. This step uses a Heat and Acid Wash process, which removes the non-nanotubic material. (Non-Nanotubic material is usually comprised of amorphous and graphitic carbon, and metal catalyst. Also, process may shorten the nanotubes by “end eroding” during the acid wash which removes the ends caps of the nanotubes.

A summary of the steps follows:

Heat nanotubes in air to 300C to expose the carbon surface and oxidize the metal catalyst.
Sonicate and wash in nitric acid and/or HCL to remove the metal catalyst, amorphous carbons and to open the ends of the nanotubes.
Clean with solvent and hot air dry. (acetone, ether and etc.)