Understanding Optical Activity in Single-Walled Carbon Nanotubes from First-Principles Studies

The origin of optical activity in single-walled carbon nanotubes (SWNTs) is investigated by performing first-principles calculations of the circular dichroism (CD) spectrum. The calculated CD is in excellent agreement with experiments, which is understood in terms of the density of states and optical absorption, providing the nanotubes' absolute configuration. These results determine which nanotubes are present or not in CD measurements and their chirality, providing a framework to understand the enantioselectivity process in recent experiments. Additionally, these results offer theoretical support to understand chirality at the nanoscale and convey selectivity in synthesis, separation, and analysis using carbon nanotubes, which are important issues in molecular recognition, nanocatalysts, DNA assembly, as well as in biofunctionalization based on SWNT technology.