Relative Optical Absorption of Metallic and Semiconducting Single-Walled Carbon Nanotubes

Abstract

While it is well-known that tube−tube interaction causes changes (peak red-shift and suppression) in the optical absorption of single-walled carbon nanotubes (SWNTs), we found in this work that, upon bundling, the optical absorption of metallic SWNTs (M₁₁) is less affected compared to their semiconducting counterparts (S₁₁ or S₂₂), resulting in enhanced absorbance ratio of metallic and semiconducting SWNTs (A_M/A_S). Annealing of the SWNTs increases this ratio due to the intensified tube−tube interaction. We have also found that the interaction between SWNTs and the surfactant Triton X-405 has a similar effect. The evaluation of SWNT separation by types (metallic or semiconducting) based on the optical absorption should take these effects into account.