Ultracentrifugation of single-walled nanotubes

Density gradient ultracentrifugation (DGU), an approach for sorting single-walled carbon nanotubes (SWNTs) by their physical and electronic structures that combines several desirable attributes for their large-scale production, including scalability, compatibility with a diverse range of raw materials, and iterative repeatability, has been discussed. DGU works by exploiting subtle differences in buoyant density, so the buoyant density of a SWNT must be directly related to its physical and electronic structure for DGU to be successful. Easily controlled parameters, such as surfactant chemistry, initial density gradient profile, and ultracentrifugation acceleration and time offered by DGU technique provide flexibility for a broad range of raw SWNT materials. DGU can be repeated iteratively as following a DGU round, the best fraction to be placed into a next gradient and the process repeated. This allows nearly arbitrary levels of purity to be achieved through multiple iterations.