Metallic single‐wall carbon nanotubes separated by density gradient ultracentrifugation

A density gradient ultracentrifugation (DGU) technique recently applied for separation of single‐wall carbon nanotubes (SWNTs) over diameter also appeared to be efficient for the nanotube separation according to their electronic structure. In this work we used DGU for extraction of a highly metallic (>97 wt%) nanotube fraction from a raw soot of arc‐discharge SWNTs. The process parameters (the surfactant type and concentration, the treatment time, the approach to the gradient formation) have been optimized. A variation of surfactant concentration allowed obtaining the highly metallic nanotube fractions with different dominant diameter distribution resulting in the “blue” or “green” top fractions. Sodium taurodeoxycholate (TDOC) was efficiently used for DGU separation of raw, non‐purified SWNTs. The fractions have been studied with the UV–Vis–NIR absorption and Raman spectroscopy.Photograph of the SWNT solution after DGU.