Purification and Preparation of Single-Walled Carbon Nanotube Films

We describe a simple process for the removal of metal catalysts and the dispersion of single-walled carbon nanotubes (SWNTs) in aqueous and organic solvents without damaging the structure of the nanotubes. The metal catalyst was removed by using a sodium hydroxide (NaOH) - ethyl alcohol (EtOH) solution. Dispersion of purified nanotubes was accomplished by using a polymer wrapping functionalization. Raman and scanning electron microscope analyses were performed to confirm the purity and the dispersion of the treated tubes. The bundle size of the dispersed SWNTs was elucidated using the atomic force microscopy technique and the size was measured as 2 - 5 nm. Transparent and conducting carbon nanotube films were prepared on glass substrates by using a spin-coating method. Optical transmission and sheet resistance measurements showed that the randomly-oriented, dispersed nanotubes film had an average sheet resistance of 974 Omega/square and a flat optical transmission of similar to 77 % at 600 nm. In this simple and scalable process, the sheet resistance and the optical transmission of the film were controlled by using the number of coatings and the concentration of the solution.