High Yield Separation of (6,5) Semiconducting Single-Walled Carbon Nanotubes Using a Gel Chromatography Method

Abstract

Single-chirality semiconducting carbon nanotubes are superior to common semiconducting materials in specific electrical and optical applications; therefore, there is a strong need for large-scale production of these carbon nanotubes. In this study, we successfully separated (6,5) semiconducting Single-Walled Carbon Nano tubes (SWCNTs) in high yield using highly concentrated CoMoCAT SWCNTs as the starting solution. We used a gel filtration method with various surfactant protocols for separation of (6,5) SWCNTs and compared the purity of separated SWCNTs from these methods to elucidate the effect of surfactant on the separation purity when highly concentrated CoMoCAT SWCNTs are used for separation. We observed that sodium dodecyl sulfate (SDS) aqueous solution alone did not effectively separate semiconducting (sc)-SWCNTs. Most of the sc-SWCNTs adsorbed on gel remained when a low concentration of SDS solution was used, or all sc-SWCNTs were desorbed from the gel when high concentration of SDS solution was used. However, when small amount of sodium deoxycholate (DOC) was added as a co-surfactant in the SDS:DOC mixture, high purity (6,5) separation was achieved. DOC exclusively adsorbed onto small-diameter (6,5) SWCNTs over other large-diameter SWCNTs, enabling the selective desorption of (6,5) SWCNTs from other large diameter sc-SWCNTs in the gel. This method is capable of separating high purity and high quantity (6,5) SWCNTs. Since the (6,5) SWCNT has a band gap (1.17 eV) that is comparable with those of common semiconducting materials, this method can be used to supply large quantities of single-chirality semiconducting carbon nanotubes for industrial applications.