701 research outputs found
Universal temperature dependence of optical excitation life-time and band-gap in chirality assigned semiconducting single-wall carbon nanotubes
The temperature dependence of optical excitation life-time, Gamma, and
transition energies, E_ii, were measured for bucky-papers of single-wall carbon
nanotubes (SWCNTs) and inner tubes in double-wall carbon nanotubes (DWCNTs)
using resonant Raman scattering. The temperature dependence of Gamma and E_ii
is the same for both types of samples and is independent of tube chirality. The
data proves that electron-phonon interaction is responsible for temperature
dependence of E_ii(T). The temperature independent inhomogeneous contribution
to Gamma is much larger in the SWCNT samples, which is explained by the
different SWCNT environment in the two types of samples. Gamma of the inner
tubes for the bucky-paper DWCNT sample is as low as \sim 30 meV, which is
comparable to that found for individual SWCNTs
Encapsulating C59N azafullerene derivatives inside single-wall carbon nanotubes
Filling of single-wall carbon nanotubes with C59N azafullerene derivatives is
reported from toluene solvent at ambient temperature. The filling is
characterized by high resolution transmission electron microscopy and Raman
spectroscopy. The filling efficiency is the same as for C60 fullerenes and the
tube-azafullerene interaction is similar to the tube-C60 interaction. Vacuum
annealing of the encapsulated azafullerene results in the growth of inner
tubes, however no spectroscopic signature of nitrogen built in the inner walls
is detected.Comment: To appear in Carbo
Interaction between concentric Tubes in DWCNTs
A detailed investigation of the Raman response of the inner tube radial
breathing modes (RBMs) in double-wall carbon nanotubes is reported. It revealed
that the number of observed RBMs is two to three times larger than the number
of possible tubes in the studied frequency range. This unexpected increase in
Raman lines is attributed to a splitting of the inner tube response. It is
shown to originate from the possibility that one type of inner tube may form in
different types of outer tubes and the fact that the inner tube RBM frequency
depends on the diameter of the enclosing tube. Finally, a comparison of the
inner tube RBMs and the RBMs of tubes in bundles gave clear evidence that the
interaction in a bundle is stronger than the interaction between inner and
outer tubes.Comment: 6 pages, 7 figures, submitted to Eur. Phys. J.
Fine Structure of the Radial Breathing Mode in Double-Wall Carbon Nanotubes
The analysis of the Raman scattering cross section of the radial breathing
modes of double-wall carbon nanotubes allowed to determine the optical
transitions of the inner tubes. The Raman lines are found to cluster into
species with similar resonance behavior. The lowest components of the clusters
correspond well to SDS wrapped HiPco tubes. Each cluster represents one
particular inner tube inside different outer tubes and each member of the
clusters represents one well defined pair of inner and outer tubes. The number
of components in one cluster increases with decreasing of the inner tube
diameter and can be as high as 14.Comment: 5 pages, 3 figure
Spin gap and Luttinger liquid description of the NMR relaxation in carbon nanotubes
Recent NMR experiments by Singer et al. [Singer et al. Phys. Rev. Lett. 95,
236403 (2005).] showed a deviation from Fermi-liquid behavior in carbon
nanotubes with an energy gap evident at low temperatures. Here, a comprehensive
theory for the magnetic field and temperature dependent NMR 13C spin-lattice
relaxation is given in the framework of the Tomonaga-Luttinger liquid. The low
temperature properties are governed by a gapped relaxation due to a spin gap (~
30K), which crosses over smoothly to the Luttinger liquid behaviour with
increasing temperature.Comment: 5 pages, 1 figure, 1 tabl
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