Hybrid core-shell nanocomposites based on silicon carbide nanoparticles functionalized by conducting polyaniline: Electron paramagnetic resonance investigations

Electron paramagnetic resonance (EPR) investigations were carried out on hybrid core-shell nanocomposites based on silicon carbide nanoparticles (SiC) and polyaniline (PANI) doped with camphor sulfonic acid (CSA). Charge carrier concentrations and thermal activations in low and high conducting polymers arranged as thin layers (2-5 nm) on the nanoparticle surfaces were investigated in a wide temperature range [4-430 K]. The EPR results and analyses are supported by complementary investigations of the macroscopic electrical conductivity and vibrational properties probed by Raman spectrometry. Temperature-dependent EPR measurements indicate paramagnetic susceptibilities with Curie-Weiss-like features and thermally activated spins. In contrast to the annealing stability of the nanocomposites, kinetic phenomena were witnessed on the EPR spectra of highly doped PANI. These phenomena correlate with the occurrence of transverse bipolarons which lead to irreversible structural changes in the polymer backbone. Polaron and bipolaron contributions to the electronic transport mechanism and the stability of the materials after annealing were found to be caused by doping rates of both the bare PANI and the nanocomposites.