SERS studies on single-walled carbon nanotubes submitted to chemical transformation with sulfuric acid Original Research Article

Surface-enhanced Raman scattering (SERS) at 676.44 nm and 1064 nm excitation wavelengths was used to investigate chemical transformation of single-walled carbon nanotubes (SWNTs) deposited on a gold support. Sulfuric acid was used as the chemical reagent. Special attention was paid to the changes in the Raman bands associated to radial and tangential vibration modes. Partial restoration of the Raman spectra by a subsequent alkaline treatment indicates a transformation with a certain degree of reversibility. The recovery reaction achieved with a 0.5 M KOH solution showed that the variations of tangential and radial band groups are not correlated. The intensity changes of the radial bands is a principal indicator for the chemical transformation of the SWNTs. Particular attention was paid to radial bands at 164 and 176 cm−1, observed with 1064 nm and 676.44 nm excitation wavelength, respectively, and their 14 cm−1 up-shifted replicas i.e. the bands at 178 and 190 cm−1. A different behavior of these bands in the anti-Stokes side was observed.