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Simultaneous separation of high-purity semiconducting and metallic single-walled carbon nanotubes by surfactant concentration-controlled gel chromatography

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Abstract Gel chromatography methods have successfully achieved separation of metallic (M-) and/or semiconducting (S-) single-walled carbon nanotubes (SWNTs) from their mixtures with high purity. However, the optimum surfactant concentrations for… Click to show full abstract

Abstract Gel chromatography methods have successfully achieved separation of metallic (M-) and/or semiconducting (S-) single-walled carbon nanotubes (SWNTs) from their mixtures with high purity. However, the optimum surfactant concentrations for gel chromatography methods are different for high-purity separation of S- and M-SWNTs; therefore, only one of S- or M-SWNTs can be obtained with high purity. In this work, we developed a new gel chromatography method for the simultaneous separation of both high-purity S-SWNTs and high-purity M-SWNTs, by adding steps to optimize surfactant concentrations of the SWNT solution prior to the separation of each SWNT. High-purity S-SWNT with a large diameter was obtained first with a high surfactant concentration (2 wt%), and then the remaining solution’s surfactant concentration was lowered to 1.5 wt% by dialysis or dilution to perform consecutive gel chromatography to separate the highly pure S-SWNT with a medium diameter. The remaining solution’s surfactant concentration was further lowered to 1 wt% to separate highly pure M-SWNTs. Through this study, we demonstrated that high purity M-SWNTs can be obtained only when all S-SWNTs are successfully separated first. Small-diameter S-SWNTs are least stable in a sodium dodecyl sulfate (SDS) dispersion among SWNTs and can be separated by a gel with a high surfactant concentration (2 wt%), while large-diameter S-SWNTs are more stable in SDS dispersions than small-diameter S-SWNTs and can therefore be separated by gel when the SDS concentration is low (1 wt%). M-SWNTs are most stable in SDS dispersions; therefore, they pass through all columns, are not adsorbed to gels, and can be collected at the end of the process. The optimum concentrations for high-purity separation of each kind of SWNTs were also investigated using their adsorption kinetics and experimental data.

Keywords: gel chromatography; purity; separation; surfactant concentration; high purity

Journal Title: Applied Surface Science
Year Published: 2020

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