Separation of Metallic and Semiconducting Single-Wall Carbon Nanotubes Using Sodium Hyodeoxycholate Surfactant

Although gel chromatography has demonstrated excellent structural separation ability with semiconducting single-wall carbon nanotubes (SWCNTs), structural separation of metallic SWCNTs remains a challenge due to their weak interactions with dextran-based gel media. In this work, we report a cholate derivative, sodium hyodeoxycholate (SHC), and apply it to the separation of metallic and semiconducting SWCNTs. The results demonstrate that the adsorbability of metallic SWCNTs coated by SHC and SDS surfactants on dextran-based gel can be dynamically enhanced through the addition of NaOH, and the difference in the adsorption order between metallic and semiconducting SWCNTs remains sufficiently large for their separation. In the absence of SHC, the separation efficiency and purity of metallic SWCNTs are dramatically reduced. On the basis of SHC-based mixed surfactants, diameter-controllable separation is achieved for both metallic and semiconducting SWCNTs ranging in diameter from 1.2 to 1.8 nm. The high-purity metallic SWCNTs obtained exhibit lower baseline absorption and a higher Raman radial breathing mode to G-band intensity ratio compared with that obtained by the conventional method, which is contributed by the effective removal of amorphous carbon and nanotube bundles. This work provides an effective strategy for single chirality and enantiomeric separation of metallic SWCNTs.