Patent ID: 7135158

Claim:
A method of purifying single wall carbon nanotubes comprising the steps of: synthesizing said single wall carbon nanotubes by an arc discharge with a carbon electrode comprising a metal catalyst consisting of Ni, Y and Ti thereby preparing single wall carbon nanotubes including an impurity which comprises the metal catalyst where the single wall carbon nanotubes grow linearly from multi-shell carbons which are spherically formed multilayers of graphite carbons formed around particles of the metal catalyst, and amorphous carbon formed around the multi-shell carbons; then, oxidizing the single wall carbon nanotubes including the impurity removing multi-shell carbons to expose the metal catalyst and removing a part of the amorphous carbon; then, refluxing the single wall carbon nanotubes in an acid solution for dissolving and removing a large part of the metal catalyst; then, again oxidizing the single wall carbon nanotubes removing the remaining amorphous carbon; and then, again refluxing the single wall carbon nanotubes in an acid solution removing the remaining metal catalyst.