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

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• 作者：Jeffrey L. Blackburn ; Timothy J. McDonald ; Wyatt K. Metzger ; Chaiwat Engtrakul ; Garry Rumbles ; Michael J. Heben
• 刊名：Nano Letters
• 出版年：2008
• 出版时间：April 2008
• 年：2008
• 卷：8
• 期：4
• 页码：1047 - 1054
• 全文大小：1627K
• 年卷期：v.8,no.4(April 2008)
• ISSN：1530-6992

文摘

The ensemble PL quantum yield for raw single-walled carbon nanotubes (SWNTs) dispersed in sodium cholate (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 E₂ and E₁ excitation show that protonation significantly affects theE₂ → E₁ relaxation process, which has typically been assumed to occur with unit efficiency. The E₂ → E₁ relaxation is 5 times more efficient in producing E₁ 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.