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

We have used IR and Raman spectroscopy 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 from arc-derived soot and after high temperature annealing. We have carried out a systematic study to define the different outcomes stemming from different purification protocols, e.g., DO, DO/HCl, DO/HNO$_{3}$, H$_{2}$O$_{2}$, H$_{2}$O$_{2}$/HCl, where the first step is either dry oxidation (DO) in flowing air or wet oxidation in refluxing H$_{2}$O$_{2}$ to remove amorphous carbon. The second step is an acid reflux step to remove the residual growth catalyst (Ni-Y). Using IR transmission through thin films of nanotubes, we resolve structure due to functional groups, which are present in the as-prepared material (e.g., -COC-), and groups added through the chemical processing (e.g., -COOH, -OH). After high temperature vacuum annealing at 1100$^{o}$C, most of oxygen-containing groups were removed. $^{\dag }$This work was supported, in part, by the NSF NIRT program (DMR- 0304178).