Ultrafast energy transfer of one-dimensional excitons between carbon nanotubes: a femtosecond time-resolved luminescence study

Abstract

Excitation energy transfer has long been an intriguing subject in the fields of photoscience and materials science. Along with the recent progress of photovoltaics, photocatalysis, and photosensors using nanoscale materials, excitation energy transfer between a donor and an acceptor at a short distance (≤1-10 nm) is of growing importance in both fundamental research and technological applications. This Perspective highlights our recent studies on exciton energy transfer between carbon nanotubes with interwall (surface-to-surface) distances of less than ∼1 nm, which are equivalent to or shorter than the size of one-dimensional excitons in carbon nanotubes. We show exciton energy transfer in bundles of single-walled carbon nanotubes with the interwall distances of ∼0.34 and 0.9 nm (center-to-center distances ∼1.3-1.4 and 1.9 nm). For the interwall distance of ∼0.34 nm (center-to-center distance ∼1.3-1.4 nm), the transfer rate per tube from a semiconducting tube to adjacent semiconducting tubes is (1.8-1.9) × 10(12) s(-1), and that to adjacent metallic tubes is 1.1 × 10(12) s(-1). For the interwall distance of ∼0.9 nm (center-to-center distance ∼1.9 nm), the transfer rate per tube from a semiconducting tube to adjacent semiconducting tubes is 2.7 × 10(11) s(-1). These transfer rates are much lower than those predicted by the Förster model calculation based on a point dipole approximation, indicating the failure of the conventional Förster model calculations. In double-walled carbon nanotubes, which are equivalent to ideal nanoscale coaxial cylinders, we show exciton energy transfer from the inner to the outer tubes. The transfer rate between the inner and the outer tubes with an interwall distance of ∼0.38 nm is 6.6 × 10(12) s(-1). Our findings provide an insight into the energy transfer mechanisms of one-dimensional excitons.

Ultrafast luminescence kinetics of metallic single-walled carbon nanotubes: Possible evidence for excitonic luminescence

“…The residual S-SWNTs might form bundles with M-SWNTs and give rise to the E 11 -and E 22 -band luminescence with a very short decay time. In our previous studies of bundles of bare SWNTs, 21,23 we reported that the energy transfer rate (per nanotube) of the E 11 exciton from a S-SWNT to an adjacent M-SWNT is ∼1.1 ×10 12 s −1 . In the case where a S-SWNT is surrounded by six M-SWNTs in the two-dimensional triangular lattice (closely packed SWNTs), the transfer rate is estimated to be ∼6.6 ×10 12 s −1 , i.e., the decay time of the E 11 band luminescence is expected to be ∼150 fs.…”

“…[20][21][22][23] We used a 0.3-mm-length cell to achieve a higher time resolution by diminishing a difference in propagation time in the sample between an excitation pulse and a luminescence signal, which is due to a difference in their group velocities. The excitation intensity was ∼2 (μJ cm −2 )/pulse [∼8 ×10 12 (photons cm −2 )/pulse].…”

Photoluminescence of poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) in the visible region

“…11,13 The excitation light with a wavelength of 400 nm (3.10 eV) was obtained by the second harmonic generation of the output of the laser. The steady state PL spectra were obtained using a home-built measurement system with an excitation light of a CW laser diode at 402 nm (corresponding photon energy 3.08 eV).…”

Trion dynamics in hole-doped single-walled carbon nanotubes

“…Hole-doping into SWNTs was done by adding HCl solution. Luminescence kinetics were measured by using time-resolved luminescence spectroscopy based on the frequency up-conversion technique [6]. We used a mode-locked Ti:sapphire laser operating at 82 MHz with a pulse width and wavelength of 80 fs and 800 nm, respectively.…”