Extraction of High-Purity Single-Chirality Single-Walled Carbon Nanotubes through Precise pH Control Using Carbon Dioxide Bubbling

Abstract

The preparation of single-chirality single-walled carbon nanotubes (SWCNTs) is of great importance to comprehensively understand their physical properties and applications. The high-purity separation of single-chirality SWCNTs has been reported using gel chromatography with a mixed surfactant system, but further improvements are necessary to enhance the purity of the resulting single-chirality SWCNTs. In this study, we focused on using pH as a parameter to improve the separation purity and investigated its influence on mixed surfactant-based purification. The pH of the mixed surfactant solution was precisely controlled with carbon dioxide bubbling with an accuracy of approximately 0.1. Using this eluent with a series of different pH values, we achieved diameter-selective separation of the SWCNTs. Moreover, we found that the residual metallic SWCNTs could be completely removed under the proper pH condition. Finally, on the basis of these findings, we produced single-chirality SWCNTs with a purity of more than 99% without residual metallic SWCNTs.

Science and applications of wafer-scale crystalline carbon nanotube films prepared through controlled vacuum filtration

“…Figure 11 b demonstrates an absorption spectrum for the obtained suspension, where only transitions associated with (6,5) SWCNTs are observed, such as E 11 , E 22 , E 33 , and their phonon sidebands. The chirality purity is estimated to be greater than 99% [96,98]. As the polarization of the incident light rotates, the attenuation of the transmitted light changes accordingly.…”

Direct observation of cross-polarized excitons in aligned single-chirality single-wall carbon nanotubes

“…Before separation, the surfactant concentrations of the filtrate were adjusted to 0.5% SDS and 0.5% SC. The pH of the solution strongly influences the adsorption of residual metallic SWCNTs [21], and thus, we used pH-adjusted surfactant solutions. The pH-adjusted solutions were loaded on gel beads, and the adsorbed (6,5) SWCNTs were eluted with a stepwise increase of the concentration of sodium deoxycholate (DOC).…”

High‐Efficiency Separation of (6,5) Carbon Nanotubes by Stepwise Elution Gel Chromatography

“…Table shows the purity of (6,5) SWCNTs estimated in the previous works using the same way that we used in this work, which shows the present result is relatively high. If further control pH parameter in gel chromatography as described in recent work, it is possible to improve the separation purity . However, this is not conducted in this work.…”

“…Because the optical and electronic properties of SWCNTs are highly dependent on their structures, large scale production of single‐chirality SWCNTs is very important for their practical applications, such as high‐performance field effect transistor (FETs) and their integrated circuits . To obtain single‐chirality SWCNTs, various separation methods have been developed to date, including density gradient ultracentrifugation (DGU), DNA‐based ion exchange chromatography (DNA), aqueous two‐phase extraction (ATP), and gel column chromatography . All methods can separate single‐chirality SWCNTs, but the throughput, that is the most important points for the researchers who need a bulk quantity of single‐chirality species, is different.…”