Purification of Single-Walled Carbon Nanotubes by a Highly Efficient and Nondestructive Approach

Abstract

Single-walled carbon-nanotubes (SWCNTs) in their as-grown state contain a large quantity of impurities such as catalytic particles and encapsulating graphitic shells. Previous purification approaches usually depended upon severe oxidation. But such oxidation in either a gas phase or a liquid phase induces structural destruction and a big loss of the SWCNT material. In this study, a new method is reported that involves transformation of catalytic iron particles to iron oxide at a low temperature of 400 °C, removal of graphitic shells by reaction with the encapsulated iron oxide at a high temperature of 800–900 °C, and final elimination of iron oxide particles by HCl. Experimental results, based on transmission electron microscopy, Raman spectroscopy, thermogravimetric analysis, and near-infrared spectroscopy, show that catalytic particles and encapsulating graphitic shells can be removed. More importantly, this highly efficient purification induces little damage to the graphitic structure of SWCNTs. These ...