Polymerization of the aniline can be conrmed by the presence of spectral peaks near 1473 and 1552 cm-1 for PANI doped samples, which are attributed to the stretching C=C and C=N modes for quinonoid
and benzenoid units of PANI, respectively, for the HCl doped PANI .
The second is associated with the excitation produced at the quinonoid
rings [16, 17].
When PANI salt is exposed to elevated temperature, the changes at the molecular level manifest themselves by the loss of doping acid molecules and formation of phenazine-like or quinonoid
Peaks at 1,591 and 1,490 [cm.sup.-1] corresponding to C = C stretching vibrations of quinonoid
and benzenoid rings, respectively .
de Souza et al., "Gastroprotective effect of barbatusin and 3-beta-hydroxy-3-deoxibarbatusin, quinonoid
diterpenes isolated from Plectranthusgrandis, in ethanol-induced gastric lesions in mice," Journal of Ethnopharmacology, vol.
Menna-Barreto, and eyal, "The evaluation of quinonoid
compounds against Trypanosoma cruzi: Synthesis of imidazolic anthraquinones, nor-[beta]-lapachone derivatives and [beta]-lapachone-based 1,2,3-triazoles," Bioorganic & Medicinal Chemistry, vol.
Kaufman, "Reduction of quinonoid
dihydrobiopterin to tetrahydrobiopterin by nitric oxide synthase," Journal of Biological Chemistry, vol.
However, there are some studies pointing out that EGCG of high concentration can cause self-oxidization and function as the prooxidant [28-31] by producing hydroxyl radicals, hydrogen peroxide, and quinonoid
intermediates causing cytotoxicity .
Peak at1302 [cm.sup.-1](C-N stretching of the benzenoid ring ,1141 [cm.sup.-1] (C-H in-plane deformation) The main absorption bands of pure polyaniline at 1567 [cm.sup.-1] and 1480 [cm.sup.-1] for the C=C stretching deformation of benzonoid and quinonoid
rings, Peak at 813 [cm.sup.-1] (C-H out-of-plane deformation in the p-disubstituted benzene ring ), peak at 3349 [cm.sup.-1] N-H stretching vibration mode .
The characteristic peaks at 1562 [cm.sup.-1] and 1495 [cm.sup.-1] are due to the presence of quinonoid
and benzenoid rings, respectively.
According to literature reports [33-35] the N1s spectra of polyaniline can be described with four components at 398.20, 399.40, 400.7, and 402.6 eV, which can be assigned to different polyaniline units: quinonoid
, benzenoid, protonated benzenoid, and protonated quinonoid
, respectively (Figure 1).
Sanyal, "Separation methods of quinonoid
constituents of plants used in oriental traditional medicines," Journal of Chromatography B, vol.