Mechanism and Mitigation of Irreversible Material Loss within Gel-Based Single-Walled Carbon Nanotube Purification Schemes

Abstract

Sephacryl-based separation of single-walled carbon nanotubes (SWCNTs) has afforded the enrichment of samples according to both type (metal/semiconducting) and band structure (chirality). However, Sephacryl-based procedures suffer from low process efficiency, in that some of the purified SWCNTs remain irreversibly bound on the gel. This work focuses on the elucidation of mechanistic aspects relating to the irreversible retention of SWCNT by Sephacryl S200 and identification of strategies to reduce material loss. By probing system parameters such as SWCNT or sodium dodecyl sulfate (SDS) concentration during adsorption, loading ratio (number of SWCNTs vs. number of gel binding sites), and the effect of kosmotropic additives on process elution efficiency, this work identifies inhomogeneous features belonging to SWCNTs as the primary factor which promotes their irreversible retention. Process elution efficiency is found to be negatively correlated with increased SDS surfactant concentration and increased SWNT loading, and methods are identified to mitigate material losses in Sephacryl-based SWCNT separation schemes. Application of NaF, a strong kosmotropic agent, to elute SWCNTs from Sephacryl is found to increase process elution efficiency from 54% to 88% compared to SDS surfactant alone. Collectively, this work both improves upon and provides valuable insight into the purification of SWNT with Sephacryl.

Gel Chromatography for Separation of Single-Walled Carbon Nanotubes

“…For example, the addition of NaF greatly increased the elution efficiency from 54% to 88%. This study suggests that the arrangement of SDS plays an important role in the elution of SDS-SWNT assemblies [89]. The gel synthesized by polymerization with only MBA and APS exhibited higher elution efficiency than many non-Sephacryl gels.…”

“…For example, the addition of NaF greatly increased the elution efficiency from 54% to 88%. This study suggests that the arrangement of SDS plays an important role in the elution of SDS-SWNT assemblies [ 89 ].…”

Preparing high-concentration individualized carbon nanotubes for industrial separation of multiple single-chirality species

“…24 and 25 ). With an increase in the loading amount, the proportion of irreversibly adsorbed SWCNTs decreased rapidly from 70% to ~15%, which originated from the quasirandom irreversible adsorption in gel chromatography 53 . Compared with reversible adsorption, irreversible adsorption sites exhibited stronger affinity with SWCNTs.…”