Three-Dimensional Variable Range Hopping and Thermally Activated Conduction Mechanism of Polypyrrole/Zinc Cobalt Oxide Nanocomposites

Abstract

Zinc cobalt oxide (ZCO) nanoparticles and zinc cobalt oxide/polypyrrole (ZCO/PPy) nanocomposites were synthesized by hydrothermal and in situ chemical polymerization routes, respectively. X-ray diffraction (XRD) patterns of PPy and ZCO/PPy nanocomposites show the amorphous nature of PPy, while there is the presence of dominant crystalline peaks of ZCO in the PPy matrix. Field-emission scanning electron microscopy (FESEM) depicts a spherical geometry and shows a decrease in the particle size with an increase in the ZCO weight percentage, while the transmission electron microscopy (TEM) images depict the core–shell-type formation of particles with aggregated ZCO nanoparticles as a core embedded in the PPy shell. The Fourier transform infrared (FTIR) spectra of ZCO/PPy nanocomposites show all the asymmetrical stretching vibrations of PPy and ZCO along with an increase in intensities of the respective metal oxides peaks and slight shifts in a few bands. Further, the transport studies, i.e., direct current (DC) conductivities of the ZCO/PPy nanocomposites, were studied as a function of temperature (300–453 K) and reveal semiconducting transport behavior. The analysis of DC conduction in PPy and ZCO/PPy suggests that the conduction of charge carriers follows the three-dimensional Mott variable range hopping (3D-VRH) model at a lower temperature, while it follows a thermally activated conduction model at high temperature.