Trajectory of the Selective Dissolution of Charged Single-Walled Carbon Nanotubes

Abstract

Single-Walled Carbon Nanotubes (SWCNTs) are materials with an array of remarkable physical properties determined by their geometries, however, SWCNTs are typically produced as a mixture of different lengths and electronic types. Consequently, many methods have been developed to sort the as-produced SWCNT samples by their physical cha-racteristics, often requiring aggressive and unscalable techniques to overcome the strong bundling forces between the nanotubes. Previously, it has been shown that negatively charging SWCNTs can lead to their thermodynamically-driven dissolution in polar solvents, and moreover that this process can selectively dissolve different SWNCT species, albeit with contrasting claims of selectivity. Here we carefully investigate dissolution as a function of charge added to the SWCNT starting material, using a range of complementary techniques. We uncover a far richer dependence on charge of SWCNT dissolution than previously reported. At low charge added, amorphous carbons preferentially dissolve, followed sequentially by metallic, larger diameter semiconducting SWCNTs, and finally smaller diameter semiconducting SWCNTs. At an optimal value, the dissolution yield is maximized across all species, however at higher charge than this we find the larger diameter and metallic SWCNTs are so charged they are no longer soluble, leaving smaller diameter SWCNTs in solution. Our results therefore clearly demonstrate two interconnected mechanisms for dissolution: on one hand charging of the SWNCTs based on their respective electron affinities on the other the solution thermodynamics. This work reconciles contrasting reports in the literature, provides a blueprint for scalable SWCNT separation and more generally demonstrates the..