Protonation Effects on the Branching Ratio in Photoexcited Single-Walled Nanotube Dispersions
The ensemble PL quantum yield for raw single-walled carbon nanotubes (SWNTs) dispersed in sodium cholate (SC) is {approx}5 times greater than that for the same raw SWNTs dispersed in sodium dodecyl sulfate (SDS) and {approx} 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{sub 2} and E{sub 1} excitation show that protonation significantly affects the E{sub 2} {yields} E{sub 1} relaxation process, which has typically been assumed to occur with unit efficiency. The E{sub 2} {yields} E{sub 1} relaxation is 5 times more efficient in producing E{sub 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.
- Research Organization:
- National Renewable Energy Lab. (NREL), Golden, CO (United States)
- Sponsoring Organization:
- USDOE
- DOE Contract Number:
- AC36-99-GO10337
- OSTI ID:
- 940668
- Journal Information:
- Nano Letters, Vol. 8, Issue 4, 2008
- Country of Publication:
- United States
- Language:
- English
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