Self-Sorting of 10-µm-Long Single-Walled Carbon Nanotubes in Aqueous Solution

Single-walled carbon nanotubes (SWCNTs) are a class of 1D nanomaterials that exhibit extraordinary electrical and optical properties. However, many of their fundamental studies and practical applications are stymied by sample polydispersity. SWCNTs are synthesized in bulk with broad structural (chirality) and geometrical (length and diameter) distributions; problematically, all known post-synthetic sorting methods rely on ultrasonication, which cuts SWCNTs into short segments (typically <1 µm). It is demonstrated that ultralong (>10 µm) SWCNTs can be efficiently separated from shorter ones through a solution-phase "self-sorting". It is shown that thin-film transistors fabricated from long semiconducting SWCNTs exhibit a carrier mobility as high as ≈90 cm² V^-1 s^-1 , which is ≈10 times higher than those which use shorter counterparts and well exceeds other known materials such as organic semiconducting polymers (<1 cm² V^-1 s^-1 ), amorphous silicon (≈1 cm² V^-1 s^-1 ), and nanocrystalline silicon (≈50 cm² V^-1 s^-1 ). Mechanistic studies suggest that this self-sorting is driven by the length-dependent solution phase behavior of rigid rods. This length sorting technique shows a path to attain long-sought ultralong, electronically pure carbon nanotube materials through scalable solution processing.