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

Abstract

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.