Enrichment Mechanism of Semiconducting Single-Walled Carbon Nanotubes by Surfactant Amines
- 27 April 2009
- journal article
- research article
- Published by American Chemical Society (ACS) in Journal of the American Chemical Society
- Vol. 131 (19), 6775-6784
- https://doi.org/10.1021/ja809054c
Abstract
Utilization of single-walled carbon nanotubes (SWNTs) in high-end applications hinges on separating metallic (met-) from semiconducting (sem-) SWNTs. Surfactant amines, like octadecylamine (ODA) have proven instrumental for the selective extraction of sem-SWNTs from tetrahydrofuran (THF) nanotube suspensions. The chemical shift differences along the tail of an asymmetric, diacetylenic surfactant amine were used to probe the molecular dynamics in the presence and absence of nanotubes via NMR. The results suggest that the surfactant amine head is firmly immobilized onto the nanotube surface together with acidic water, while the aliphatic tail progressively gains larger mobility as it gets farther from the SWNT. X-ray and high-resolution TEM studies indicate that the sem-enriched sample is populated mainly by small nanotube bundles containing ca. three SWNTs. Molecular simulations in conjunction with previously determined HNO3/H2SO4 oxidation depths for met- and sem-SWNTs indicate that the strong pinning of the amine surfactants on the sem-enriched SWNTs bundles is a result of a well-ordered arrangement of nitrate/amine salts separated with a monomolecular layer of H2O. Such continuous 2D arrangement of nitrate/amine salts shields the local environment adjacent to sem-enriched SWNTs bundles and maintains an acidic pH that preserves nanotube oxidation (i.e., SWNTn+). This, in turn, results in strong interactions with charge-balancing NO3− counterions that through their association with neutralized surfactant amines provide effective THF dispersion and consequent sem enrichment.Keywords
This publication has 42 references indexed in Scilit:
- Sorting carbon nanotubes by electronic structure using density differentiationNature Nanotechnology, 2006
- Structure-Based Carbon Nanotube Sorting by Sequence-Dependent DNA AssemblyScience, 2003
- Separation of Metallic from Semiconducting Single-Walled Carbon NanotubesScience, 2003
- DNA-assisted dispersion and separation of carbon nanotubesNature Materials, 2003
- A Route for Bulk Separation of Semiconducting from Metallic Single-Wall Carbon NanotubesJournal of the American Chemical Society, 2003
- Interaction of Oxidized Single-Walled Carbon Nanotubes with Vaporous Aliphatic AminesThe Journal of Physical Chemistry B, 2002
- End-group and defect analysis of soluble single-walled carbon nanotubesChemical Physics Letters, 2001
- Carbon NanotubesPublished by Springer Nature ,2001
- Dissolution of Single-Walled Carbon NanotubesAdvanced Materials, 1999
- Fullerene PipesScience, 1998