TY - JOUR
T1 - Dynamics and transient absorption spectral signatures of the single-wall carbon nanotube electronically excited triplet state
AU - Park, Jaehong
AU - Deria, Pravas
AU - Therien, Michael J.
PY - 2011/11/2
Y1 - 2011/11/2
N2 - 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.
AB - 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.
UR - http://www.scopus.com/inward/record.url?scp=80054999136&partnerID=8YFLogxK
U2 - 10.1021/ja2079477
DO - 10.1021/ja2079477
M3 - Article
C2 - 21970339
AN - SCOPUS:80054999136
SN - 0002-7863
VL - 133
SP - 17156
EP - 17159
JO - Journal of the American Chemical Society
JF - Journal of the American Chemical Society
IS - 43
ER -