Protonation Effects on the Branching Ratio in Photoexcited Single-Walled Nanotube Dispersions

Jeffrey L. Blackburn, Timothy J. McDonald, Wyatt K. Metzger, Chaiwat Engtrakul, Garry Rumbles, Michael J. Heben

Research output: Contribution to journalArticlepeer-review

42 Scopus Citations


The ensemble PL quantum yield for raw single-walled carbon nanotubes (SWNTs) dispersed in sodium ctiolate (SC) is ∼5 times greater than that for the same raw SWNTs dispersed in sodium dodecyl sulfate (SDS) and ∼10 times greater than the quantum yield of purified SWNTs dispersed In SC. Absorbance and Raman spectra indicate that purified SC-dispersed SWNTs and raw SDS-dispersed SWNTs are hole-doped by protonation. Experiments comparing PL emission efficiency using E 2 and E 1 excitation show that protonation significantly affects the E 2 → E 1 relaxation process, which has typically been assumed to occur with unit efficiency. The E 2 → E 1 relaxation is 5 times more efficient in producing E 1 PL when SWNTs are unprotonated and protected by the SC surfactant. The results provide clear evidence that extrinsic factors, such as residual acids and the specific nature of SWNT-surfactant and SWNT-solvent interactions, can significantly affect measured SWNT luminescence quantum yields.

Original languageAmerican English
Pages (from-to)1047-1054
Number of pages8
JournalNano Letters
Issue number4
StatePublished - Apr 2008

NREL Publication Number

  • NREL/JA-590-42384


  • branching ratio
  • carbon
  • efficiency
  • excitation
  • luminescence
  • nanotubes
  • raman spectra
  • relaxation
  • sodium
  • sulfates


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