New metric for evaluating the purity of single-walled carbon nanotubes using ultraviolet–visible-near infrared absorption spectroscopy

Accurate purity evaluation of single-walled carbon nanotubes (SWCNTs) forms the basis for an improvement of material quality during synthesis and purification. We propose a novel purity evaluation method of as-produced and purified SWCNTs by using ultraviolet–visible-near infrared absorption spectroscopy. Our approach integrates the absorption peaks from the interband electronic transitions of semiconducting and metallic tubes after the linear subtraction of π-plasmon contribution in optical absorption spectra from SWCNT-containing samples. For the constructed sample sets prepared by mixing designed amounts of highly pure SWCNTs and carbonaceous impurities, this method has demonstrated quite a good closeness of the measured purities to the designed ones. Our novel purity-evaluation method has also verified its usability for a set of arc-produced samples having different SWCNT purities, prepared by isothermal oxidation at 275∼475 °C.