Purification of single-walled carbon nanotubes using a supercritical fluid extraction method

Metal catalyst used in the production of single-walled carbon nanotubes (SWNTs) can be effectively removed from the as-grown nanotubes by an in situ chelation/supercritical fluid carbon dioxide extraction method. A pretreatment procedure using bulk electrolysis with ethylenediaminetetraacetic acid significantly improve, the efficiency of supercritical fluid extraction probably by removing the amorphous carbon associated with the metal from the SWNTs. More than 98% of the iron impurity can be removed from the as-grown SWNTs using this two-step purification method without obvious damage to the nanotube structures according to our spectroscopic data.