Protonation of Carbon Single-Walled Nanotubes Studied Using 13C and 1H-13C Cross Polarization Nuclear Magnetic Resonance and Raman Spectroscopies

Chaiwat Engtrakul, Mark F. Davis, Thomas Gennett, Anne C. Dillon, Kim M. Jones, Michael J. Heben

Research output: Contribution to journalArticlepeer-review

66 Scopus Citations

Abstract

The reversible protonation of carbon single-walled nanotubes (SWNTs) in sulfuric acid and Nation was investigated using solid-state nuclear magnetic resonance (NMR) and Raman spectroscopies. Magic-angle spinning (MAS) was used to obtain high-resolution 13C and 1H-13C cross polarization (CP) NMR spectra. The 13C NMR chemical shifts are reported for bulk SWNTs, H2SO4-treated SWNTs, SWNT-Nafion polymer composites, SWNT-AQ55 polymer composites, and SWNTs in contact with water. Protonation occurs without irreversible oxidation of the nanotube substrate via a charge-transfer process. This is the first report of a chemically induced change in a SWNT 13C resonance brought about by a reversible interaction with an acidic proton, providing additional evidence that carbon nanotubes behave as weak bases. Cross polarization was found to be a powerful technique for providing an additional contrast mechanism for studying nanotubes in contact with other chemical species. The CP studies confirmed polarization transfer from nearby protons to nanotube carbon atoms. The CP technique was also applied to investigate water adsorbed on carbon nanotube surfaces. Finally, the degree of bundling of the SWNTs in Nation films was probed with the 1H-13C CP-MAS technique.

Original languageAmerican English
Pages (from-to)17548-17555
Number of pages8
JournalJournal of the American Chemical Society
Volume127
Issue number49
DOIs
StatePublished - 14 Dec 2005

NREL Publication Number

  • NREL/JA-590-38727

Keywords

  • carbon single-walled nanotubes
  • cross polarization
  • nuclear magnetic resonance (NMR) spectroscopy
  • protonation
  • raman spectroscopy

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