Dynamics and transient absorption spectral signatures of the single-wall carbon nanotube electronically excited triplet state

Jaehong Park, Pravas Deria, Michael J. Therien

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59 Scopus citations

Abstract

We utilize femtosecond-to-microsecond time domain pump-probe transient absorption spectroscopy to interrogate for the first time the electronically excited triplet state of individualized single-wall carbon nanotubes (SWNTs). These studies exploit (6,5) chirality-enriched SWNT samples and poly[2,6-{1,5-bis(3-propoxysulfonic acid sodium salt)}naphthylene]ethynylene (PNES), which helically wraps the nanotube surface with periodic and constant morphology (pitch length = 10 ± 2 nm), providing a self-assembled superstructure that maintains structural homogeneity in multiple solvents. Spectroscopic interrogation of such PNES-SWNT samples in aqueous and DMSO solvents using E 22 excitation and a white-light continuum probe enables E 11 and E 22 spectral evolution to be monitored concomitantly. Such experiments not only reveal classic SWNT singlet exciton relaxation dynamics and transient absorption signatures but also demonstrate spectral evolution consistent with formation of a triplet exciton state. Transient dynamical studies evince that (6,5) SWNTs exhibit rapid S 1→T 1 intersystem crossing (ISC) (τ ISC ∼20 ps), a sharp T 1→T n transient absorption signal (λ max(T 1→T n) = 1150 nm; full width at half-maximum ≈ 350 cm -1), and a substantial T 1 excited-state lifetime (τ es ≈ 15 μs). Consistent with expectations for a triplet exciton state, T 1-state spectral signatures and T 1-state formation and decay dynamics for PNES-SWNTs in aqueous and DMSO solvents, as well as those determined for benchmark sodium cholate suspensions of (6,5) SWNTs, are similar; likewise, studies that probe the 3[(6,5) SWNT]* state in air-saturated solutions demonstrate 3O 2 quenching dynamics reminiscent of those determined for conjugated aromatic hydrocarbon excited triplet states.

Original languageEnglish
Pages (from-to)17156-17159
Number of pages4
JournalJournal of the American Chemical Society
Volume133
Issue number43
DOIs
StatePublished - 2 Nov 2011

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