Scalable Method for the Reductive Dissolution, Purification, and Separation of Single-Walled Carbon Nanotubes

As synthesized, bulk single-walled carbon nanotube (SWNT) samples are typically highly agglomerated and heterogeneous. However, their most promising applications require the isolation of individualized, purified nanotubes, often with specific optoelectronic characteristics. A wide range of dispersio...

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Bibliographic Details
Published in:ACS nano 2012-01, Vol.6 (1), p.54-62
Main Authors: Fogden, Siân, Howard, Christopher A, Heenan, Richard K, Skipper, Neal T, Shaffer, Milo S. P
Format: Article
Language:English
Subjects:
Agglomeration
Chemical Fractionation - methods
Crystallization - methods
Dispersions
Dissolution
Nanostructure
Nanostructures - chemistry
Nanostructures - ultrastructure
Nanotubes
Particle Size
Purification
Separation
Single wall carbon nanotubes
Sodium
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Summary:As synthesized, bulk single-walled carbon nanotube (SWNT) samples are typically highly agglomerated and heterogeneous. However, their most promising applications require the isolation of individualized, purified nanotubes, often with specific optoelectronic characteristics. A wide range of dispersion and separation techniques have been developed, but the use of sonication or ultracentrifugation imposes severe limits on scalability and may introduce damage. Here, we demonstrate a new, intrinsically scalable method for SWNT dispersion and separation, using reductive treatment in sodium metal-ammonia solutions, optionally followed by selective dissolution in a polar aprotic organic solvent. In situ small-angle neutron scattering demonstrates the presence of dissolved, unbundled SWNTs in solution, at concentrations reaching at least 2 mg/mL; the ability to isolate individual nanotubes is confirmed by atomic force microscopy. Spectroscopy data suggest that the soluble fraction contains predominately large metallic nanotubes; a potential new mechanism for nanotube separation is proposed. In addition, the G/D ratios observed during the dissolution sequence, as a function of metal:carbon ratio, demonstrate a new purification method for removing carbonaceous impurities from pristine SWNTs, which avoids traditional, damaging, competitive oxidation reactions.
ISSN:1936-0851
1936-086X
DOI:10.1021/nn2041494