C60–polymer nanocomposites: evidence for interface interaction Original Research Article

Polyaniline–fullerene (PA–C60) composites have been studied by Surface Enhanced Raman scattering (SERS) spectroscopy and X-ray diffraction. They were obtained by mixing solutions of polyaniline–emeraldine base (PA–EB) and C60, as well as by chemical synthesis from aniline, sulfuric acid and potassium dichromate, with addition of C60. The Raman bands peaking at 1330–1370 cm−1, associated with a protonated structure were used as indicative for changes of the PA–EB phonon spectrum resulting from C60 doping. The two types of compounds show different SERS spectra, also dependent on the metallic support used (Au or Ag). Variation of the SERS spectra with the type of metallic support is related to a chemical interface interaction between composite and metal. In mixture samples, a doped polymeric chain (with ionically attached C60−) was evidenced by an increased fraction of quinoid rings. The SERS spectra of the chemically synthesized PA–C60 reveals the existence of two polymeric structures: a doped PA (doped with C60− ions) and an undoped one, the latter with a structure of ‘pendant chain’ type. Structural (XRD) data reveal the presence of C60 nano-zones, with a lattice parameter increase of 0.3–0.6%, attributed to slight oxidation. Detailed analysis of the fcc(111) line asymmetry suggests, in mixture samples, a boundary zone with an ‘expanded’ lattice, induced by ionic interface effects.