Structural characterization and diameter-dependent oxidative stability of single wall carbon nanotubes synthesized by the catalytic decomposition of CO

Low T oxidation followed by brief sonication in hot HCl has been optimized to remove Fe catalyst residues from HiPco material with minimal loss of tubes. One pass reduces Fe from 6–10 to 0.6–1.6 at.% with 60% yield, most of the loss being Fe. Raman scattering reveals a broad diameter distribution with a mean of 1.0–1.1 nm. After purification we find excellent correlation between oxidation temperature and Raman spectra whereby the oxidation rate varies inversely with tube diameter. This can be explained by the larger strain associated with greater curvature of small tubes.