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Photoluminescence (PL) spectroscopy was applied to determine shifts of electronic interband transition energies, E11 and E22, of semiconducting single-walled carbon nanotubes (SWNTs) under hydrostatic pressure of several kbar in a diamond anvil cell. Our results show that the energy shifts depend not only on the (n,m) structure (helicity) of nanotubes, but also on nanotube aggregation and interaction with the surrounding medium. The latter factors are also affected by application of pressure. This can explain a discrepancy between the experimental data and theoretical predictions for ‘ideal’ (non-interacting) SWNTs under hydrostatic pressure deformation. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

We report on the ‘on-line’ photoluminescence (PL) detection of individual single-walled carbon nanotubes (SWNTs) in water-surfactant dispersions. This was achieved by using a near-infrared confocal laser luminescence microscope specially optimized for the PL spectroscopy of SWNTs . A detection of single nanotubes was possible by using dispersions with a relatively low concentration of nanotubes and reducing the PL acquisition time so that a ‘switch-on-switch-off’ behavior of emission peaks was observed, which reflected a random diffusion of different nanotubes through the laser focus volume. These results demonstrate the analytical potential of PL spectroscopy using SWNTs as luminescent markers. © 2005 American Institute of Physics [ABSTRACT FROM AUTHOR]

Significant shifts of photoluminescence (PL) emission-excitation resonances have been observed by freezing and cooling of water-surfactant dispersions of single-walled carbon nanotubes (SWNTs) down to 16 K. The PL resonances correspond to E11S, E22S electronic energies of specific (n,m) nanotubes. The shifts occur mainly in the interval of ∼150–200 K, are reversible and similar for SWNT dispersions with different surfactants and viscosity-increasing additives. The sign of the shifts is determined by the (n-m) mod 3 rule, whereas the shift magnitude depends on a chiral angle, being the smallest for the large angles. These results are in agreement with tight-binding model calculations of Yang et al. for SWNTs under uniaxial compression (apparently caused by thermal contraction of the ice matrix in our case). This indicates a high sensitivity of electronic properties of SWNTs to mechanical strain and suggests an extended, ‘rod’-like configuration of nanotubes in frozen dispersions. © 2004 American Institute of Physics [ABSTRACT FROM AUTHOR]

We have applied the efficient FTIR-Luminescence technique to map the near-infrared photoluminescence (PL) of individual micelle-isolated single-walled carbon nanotubes (SWNTs) in a broad UV-visible-NIR excitation range. Monochromatic light of xenon and tungsten halogen lamps was used for PL excitation. Such PL maps provide a rich information about characteristic electronic transitions in SWNTs. The PL intensity shows a nonlinear behavior, when excited with nanosecond laser pulses. This is likely due to quenching interactions between multiple electronic excitations generated and propagating in nanotubes. This effect is similar for different, selectively excited nanotubes and allows us to estimate the PL lifetime (electronic relaxation time) in micelle-isolated nanotubes as ∼100 ps. © 2003 American Institute of Physics [ABSTRACT FROM AUTHOR]