Study of single walled carbon nanotube functionalization by means of surface enhanced Raman spectroscopy

Abstract

Raman spectroscopy is known to provide information about the quality of the single walled carbon nanotubes (SWCNT). The information is based on the intensity ratio of D and G spectral modes and the frequency of RBM modes. However due to resonance nature of Raman spectrum of the nanotubes this method is not suitable to detect functionalization of the nanotubes. Surface enhanced Raman spectroscopy (SERS) is known to enhance the Raman bands up to fourteen orders of magnitude. Preferable adsorption sites for small silver nanoparticles are expected to be the functional groups of SWCNT; therefore SERS technique allows detecting small amounts of functional groups despite strong resonance Raman from backbone of SWCNT. In this study functionalized nanotubes were dispersed in silver colloid and dried on the standard silver plate for Raman measurements. Spectra of SWCNT without colloid in the spectral range between 50 and 1800 cm -1 exhibit only four main spectral features: G, D, and RBM modes between 200 and 400 cm -1 . Spectra of SWCNT with the colloid exhibit several additional spectral bands which do not belong to the colloid. These bands attributed to vibrations of C-O, C-C and O-H from the functional groups and the carbon atom of the SWCNT attached to the corresponding group. The bands associated with the vibrations involving O atom is an indication that silver nanoparticles interact with the functional group attached to SWCNT.