Influence of the purification process on the semiconducting content of single-walled carbon nanotubes synthesized by arc discharge

Single-walled carbon nanotubes (SWCNTs) were synthesized by arc discharge and then purified by a two-step process including thermal and acid treatments. As-synthesized, thermal-treated, and fully purified (thermal- and acid-treated) samples were characterized using thermogravimetric analysis, continuous resonant Raman scattering, and ultraviolet-visible-near infrared (UV-Vis-NIR) absorption spectroscopy. Thermal and acid treatments eliminate carbonaceous particles and metal catalyst particles, respectively, resulting in high-purity SWCNTs. Continuous resonant Raman scattering and UV-Vis-NIR absorption spectroscopy demonstrated that the metallic content of the arc-synthesized SWCNTs varied according to the purification process; as-synthesized (∼15%), thermal-treated (∼30%), and thermal/acid-treated (∼25%). Transparent conducting films were prepared using three different purity grades and their properties were analyzed. Thermal-treated nanotubes displayed superior performance compared with the other samples owing to its higher metallic content and smaller bundle diameters.