Chitosan – Graphite – Maghemite – a Flexible, Superparamagnetic Nanocomposite Comprising of Microcapacitors

In this work, an eco-friendly “green” nanocomposite of chitosan containing graphite and maghemite (g-Fe2O3) nanoparticles were prepared by solution casting method. The effect of g-Fe2O3 nanoparticles on structural, electric and dielectric properties of Chitosan-graphite (Cs-graphite) composites was investigated. The dielectric constant of Cs-graphite composites increased with incorporation of g-Fe2O3 nanoparticles. Among the composites Cs-20% graphite - 20% g-Fe2O3 has dielectric constant of ~16.5 at 1 MHz at room temperature. With increase in temperature the dielectric constant varied significantly. The conductivity of Cs-graphite is enhanced by one order of magnitude with addition of g-Fe2O3 nanoparticles, and the value is found to be 5.7x10-6 S/cm. Various parameters such as dielectric constant, dielectric loss, electric modulus, conductivity, activation energy were analyzed. Magnetic measurement of g-Fe2O3 nanoparticles and the PNCs showed superparamagnetic behaviour. A model is proposed to explain the observed dielectric behavior of polymer nanocomposites (PNCs). The formation of microcapacitors by incorporation of maghemite nanoparticles between graphite is proposed.