Electrochemical functionalization of single-walled carbon nanotubes with polyaniline evidenced by Raman and FTIR spectroscopy

Using Raman and Fourier transform infrared (FTIR) spectroscopy, we show that depending on the acid medium used, i.e. HCl and H2SO4, electrochemical polymerization of aniline on a single-walled carbon nanotubes (SWNTs) film leads to a covalent functionalization of SWNTs with polyaniline (PANI) and a PANI doped with carbon nanotube fragments, respectively. For polymer-functionalized SWNTs, the Raman scattering suggests an additional nanotubes roping with PANI as a binding agent. A post chemical treatment with the NE4OH solution of polyrner-functionalized SWNTs involves an internal redox reaction between PANI and carbon nanotubes. As a result, the polymer chain undergoes a transition from the semi-oxidized state into a reduced one. Besides, the FTIR spectrum of PANI-functionalized SWNTs display an intense absorption band with two components at 773 and 755 cm(-1), which are associated with the vibration of deformation of the benzene and the quinoid ring, respectively. This indicates a strong hindrance effect produced by the binding on the polymer chain of SWNTs.