Raman and IR Spectroscopy of Chemically Processed Single-Walled Carbon Nanotubes

IR and Raman spectroscopy has been used to study the evolution of the vibrational spectrum of bundled single-walled carbon nanotubes (SWNTs) during the purification process needed to remove metal catalyst and amorphous carbon present in arc-derived SWNT soot. We have carried out a systematic study to define the different outcomes stemming from the purification protocol (e.g., DO, DO/HCl, DO/HNO3, H2O2, H2O2/HCl), where dry oxidation (DO) or refluxing in H2O2 was used in a first purification step to remove amorphous carbon. The second step involves acid reflux (HCl or HNO3) to remove the residual growth catalyst (Ni−Y). During strong chemical processing, it appears possible to create additional defects where carbon atoms are eliminated, the ring structure is now open, localized CC bonds are created, and O-containing groups can be added to this defect to stabilize the structure. Evolution of SWNT skeletal disorder obtained via chemical processing was studied by Raman scattering. Higher intensity ratios of R...