Exciton dynamics probed in carbon nanotube suspensions with narrow diameter distribution

Abstract

We report on a pump -probe study of CoMoCAT nanotube suspensions with narrow chirality distribution. Visible pump pulses and a white light continuum are used for resonant excitation of the strongest dipole allowed E 22 subband exciton in the semiconducting (6, 5) tube and for broadband probe of the resulting spectral transients between 1300 nm and 480 nm, respectively. Transient spectra show signatures of both photobleaching (PB) and photoabsorption (PA) with practically identical decay-but slightly different risetimes. The experiments reveal that apparent variations of decay rates at different wavelengths do not reflect dynamics of different relaxation processes but are a consequence of the superposition of PB and blue-shifted PA response.

Ultrafast Spectral Exciton Diffusion in Single-Wall Carbon Nanotubes Studied by Time-Resolved Hole Burning

“…34,35 The spectra can be well described by a superposition of Lorentzian photobleach (PB) and photoabsorption (PA) signals centered at 987 nm and 982 nm respectively. [36][37][38][39][40] At early times, the transient spectra of Fig. 1b) are substantially narrower than the typical FWHM of the exciton band of 60 meV, observed in the ground state absorption spectrum of Fig.…”

Optical properties of structurally sorted single‐wall carbon nanotube ensembles

“…The 981 nm feature is associated with the first subband E 11 exciton transition in the (6,5) tube which is here estimated to account for about 36% of the absorption signal by semiconducting tubes in the 800 nm-1250 nm range. The other most dominant and partially overlapping absorption features in this frequency range are those of the (5,4) at 844 nm, (6,4) at 882 nm, (9,1) at 922 nm, (8,3) at 963 nm, (7,3) at 998 nm, (7,5) at 1022 nm, as well as features in a more strongly congested region around 1150 nm. The purple coloration of the topmost bands can be attributed the energetic position of the higher lying E 22 subband excitons which for the dominant (6,5) tube, for example lies at 571 nm.…”

“…Spectroscopic studies of carbon nanotube ensembles as colloidal suspensions have received much attention of the past several years [1][2][3][4][5][6][7]. Traditionally, suspensions are prepared by sonication of raw nanotube soot with amphiphilic surfactants such as sodium cholate (SC), sodium dodecyl sulfate (SDS), or DNA in water [1].…”

Elucidation of the Electronic Structure of Semiconducting Single-Walled Carbon Nanotubes by Electroabsorption Spectroscopy

“…TPA or transient absorption techniques used to determine the binding energy of the optical exciton in the n 1 manifold (Ex1) are not useful for this, as nonlinear absorptions to states in the n 2 manifold will be masked by the linear absorption to Ex1. Interference effects between Ex2 and the n 1 continuum band, suggested from relaxation studies of Ex2 [13,14], are also difficult to verify directly. Clearly, measurements that can probe much broader energy regions of S-SWCNTs are called for.…”

“…High resolution will also allow direct detection of mA g . We find strong evidence for Fano-type coupling between Ex2 and n 1 continuum states [13,14]. Syntheses of chirality enriched S-SWCNTs are allowing a variety of sophisticated spectroscopic measurements.…”