Correlation between Raman spectroscopy and electrical conductivity of graphite/polyaniline composites reacted with hydrogen peroxide

The aim of this work is to correlate the Raman spectroscopic studies to the electrical properties of graphite/polyaniline composites (G/PANI) reacted with hydrogen peroxide. Raman spectroscopic studies have been performed for G/PANI composites with different graphite weight concentrations (y% = 0, 10, 20, 50). As expected, Raman bands situated at 1350 and 1580 cm(-1) coming from graphite lattice appear, and their intensity increases with increasing graphite concentrations. The measured Raman region (1170-1800 cm(-1)) of PANI reacted with hydrogen peroxide was convoluted and fitted with seven Lorentzian curves. Three Lorentzian curves centred at 1609, 1578 and 1336 cm(-1) are investigated. We find that the band at 1578 cm(-1) attributed to the C=C stretching vibration in the quinonoid ring (Q) is slightly shifted to 1584 cm(-1) and its intensity increases during the reaction with hydrogen peroxide. However, the peaks at 1609 and 1336 cm(-1) attributed respectively to the C-C stretching of the benzenoid ring (B) and C-N+. vibration of delocalized polaronic structures (protonation band-PB), keep the same position and their intensities decrease. This could be interpreted as a deprotonation of imines nitrogen atoms in PANI. These results were correlated with the electrical percolation behaviour which occurs in the composite. Indeed, the electrical conductivity of G/PANI composites treated with H2O2 increases with increasing G weight concentration, only when this later becomes higher than a critical concentration yc known as the percolation threshold. We find that the percolation behaviour is linked to the intensity decrease of B and PB bands and to the intensity increase of Q band.