Spectroscopy of single-walled carbon nanotubes in aqueous surfactant dispersion

Optical studies of single-walled carbon nanotubes (SWNTs) dispersed in aqueous surfactant suspensions have made significant progress since the discovery of their bright band-gap fluorescence in the near-infrared region [M. J. O'Connell et al., Science 297, 593-596 (2002)]. In this article we report the systematic investigation of the effect of chemical purification and oxidation on the spectroscopic properties of SWNTs. The SWNTs samples we prepared differ for the percentage of impurities present, the amount of defects introduced in their graphitic structure and/or the functional groups expressed on their surface. The generation of carboxylic groups on the nanotubes surface by oxidative treatment was validated by means of thermal gravimetric analysis and ATR/Fourier transform IR spectroscopies, as well as Raman spectroscopy. We have solubilized pristine, purified SWNTs (p-SWNTs) and oxidized SWNTs (o-SWNTS) in Milli-Q water using sodium dodecylbenzene sulphonate (SDBS). While our Vis-NIR Absorption spectra of p-SWNTs and o-SWNTS dispersions in aqueous SDBS solution show the loss of the resolution of the characteristic van Hove singularities, NIR Photoluminescence spectra are characterized by structured emission peaks. (C) 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim