We present femtosecond laser induced photobleaching of individually isolated single-wall carbon nanotubes.
Monodispersed single-wall carbon nanotubes fixed in aqueous gel were exposed under tightly focused femtosecond
laser light. We measured photoluminescence spectra of single-wall carbon nanotubes before/after the laser irradiation.
Because of unique excitonic band structures of single-wall carbon nanotubes, we clearly observed strong selectivity in
the chirality and the orientation of carbon nanotubes depending on the wavelength and polarization of laser light. We
also observed the difference from the case of continuous wave laser irradiation in the chirality selectivity and the
efficiency of photobleaching.
We present evidence that, when laser light was tightly focused into aqueous suspension of
mono-dispersed single-wall carbon nanotubes (SWCNTs), density of nanotubes was locally
increased at the focus spot of light. We prepared mono-dispersed HiPco SWCNTs in an aqueous
surfactant solution by sonication and following ultracentrifugation. We built a confocal Raman
microscope system equipped with a 633 nm He-Ne laser, and launched the laser light into SWCNTs
suspension filled in a glass micro-cell by a high numerical aperture objective lens (N.A.=1.35).
We monitored temporal change in Raman spectrum of SWCNTs excited by the laser light. We
clearly observed significant intensity increase of a particular radial breathing mode, however the
increase of the Raman signal did not last permanently, rather showed transient response. This
result implies that SWCNTs with particular chirality were selectively accumulated by optical
gradient force of Raman-probing laser light. We discuss the independent behavior of the radial
breathing modes, with respect to the wavelength of the laser light and the chirality of corresponding