Near-Infrared Photoluminescence of Single-Walled Carbon Nanotubes Prepared by the Laser Vaporization Method

Single-walled carbon nanotubes (SWNTs) prepared by pulsed laser vaporization, dispersed, and surfactant-stabilized in near-infrared transparent D 2 O show weak photoluminescence (PL) from ∼1300 up to >1750 nm corresponding to the lowest electronic interband transitions of semiconducting tubes. The characteristic features of this PL, such as a multiple peak emission and a strong excitation wavelength dependence (investigated for λ exc from 457 up to 1064 nm), are similar to those reported recently for SWNTs with smaller diameters of around 1 nm (O'Connell et al. Science 2002, 297, 593). The luminescence is significantly polarized with an anisotropy value r of up to 0.32, depending on the excitation and emission wavelengths. The PL data can be used for the structural assignment of emitting tubes; however, in agreement with the results of O'Connell et al., these data are only qualitatively consistent with the tight-binding model widely applied for SWNTs. The luminescence is sensitive to chemical treatment/interactions of SWNTs; much weaker and broader PL was observed above 1300 nm for dispersions of acid-treated tubes in D 2 O, whereas raw SWNTs in N,N -dimethylformamide show practically no PL. The Raman spectra of dispersed SWNTs differ from those of the solid samples.