Chitosan - Carbon Nanotube - Maghemite nanocomposites – A Flexible Negative Dielectric Constant Material

In this work, the nanocomposites of chitosan containing carbon nanotubes (CNT) and maghemite nanoparticles have been prepared by solution casting method. Techniques such as Raman spectroscopy, SEM, TEM, dielectric relaxation spectroscopy, and VSM studies were made.  The incorporation of CNT in to the chitosan matrix and also the interaction between the CNT and the maghemite nanoparticles were studied using Raman spectroscopy. The dielectric constant of Chitosan-CNT composites turned from positive to negative at low frequency when CNT concentration increased from 10 to 20wt%. Interestingly, addition of 20wt% of maghemite nanoparticles into the Cs-CNT nanocomposites affected both the dielectric property and the conductivity of the composite. VSM measurement shows that the prepared maghemite nanoparticles and the Cs-CNT-maghemite nanocomposites are superparamagnetic materials. Observed dielectric characteristics and the electrical conductivity of the samples have been explained by using a model. Tuning of negative permittivity in the chitosan-CNT nanocomposites by using maghemite nanoparticles could be useful as metamaterials.