Raman-induced Kerr effect spectroscopy of single-wall carbon nanotubes aqueous suspensions in the range 0.1-10 and 100-250 cm-1

Abstract

Here, we study a low (less than 0.1 μg/ml) concentration aqueous suspension of single-wall carbon nanotubes (SWNTs) by Raman-induced Kerr effect spectroscopy (RIKES) in the spectral bands 0.1-10 and 100-250 cm-1. This method is capable of carrying out direct investigation of SWNT hydration layers. A comparison of RIKES spectra of SWNT aqueous suspension and that of milli-Q water shows a considerable growth in the intensity of low wavenumber Raman modes. These modes in the 0.1-10 cm-1 range are attributed to the rotational transitions of H2O2 and H2O molecules. We explain the observed intensity increase as due to the production of hydrogen peroxide and the formation of a low-density depletion layer on the water-nanotube interface. A few SWNT radial breathing modes (RBM)are observed (ωRBM = 118.5, 164.7 and 233.5 cm-1) in aqueous suspension, which allows us to estimate the SWNT diameters (∼2.0, 1.5, and 1 nm, respectively). Copyright © 2011 John Wiley & Sons, Ltd.