Reproducible high-yield purification process of singlewalled carbon nanotubes was developed by combining two-step processes of thermal annealing in air and acid treatment. The process involves the thermal annealing in air with the powders rotated at temperatures of 470 °C for 50 min, which burns out the carbonaceous particles, and an acid treatment with HCl for 24 h, which etches away the catalytic metals. Control of the annealing temperature and rotation of the sample are crucial for high yield. Our reproducible optimal purification process provides a total yield of about 25 ∼ 30 wt % with less than 1 wt % of transition metals, which was confirmed by the thermogravimetric analysis. Bundling and length control depending on the different acid treatments will be further discussed.

We have investigated the effect of Nafion and its resulting interaction with single-walled carbon nanotubes (SWCNTs) on the solubility and dispersion properties of SWCNTs in bisolvent. Nafion was used as a polymeric dispersant, providing both electrostatic and steric stabilization in the preparation of a stable and homogeneous suspension of SWCNTs. A correlation was made between solubility and nanodispersion of SWCNTs. Optical spectroscopy showed that the solubility and nanodispersion of SWCNTs increased with the addition of 1-propanol and were greatest at a volume mixture of water/1-propanol of 80/20. We propose a mechanism of improved solubility and nanodispersion of SWCNTs, which is strongly correlated with the adsorption behavior of Nafion on SWCNTs, the surface potential of SWCNTs, and the solubility of Nafion in a liquid medium; amphiphilic Nafion enhances the dispersion of SWCNTs in the mixture of hydrophilic water and relatively hydrophobic 1-propanol.