Impedance spectroscopy characterization of relaxation mechanisms in gold-chitosan nanocomposites

Au-Chi nanocomposites with different AuNPs additions were investigated. The dispersion of AuNPs in polymer matrix was observed using s-SNOM analysis. The dielectric properties as a function of temperature show two relaxation processes: (1) a primary alpha-relaxation process, at low temperatures; (2) a second low frequency relaxation at temperatures between 70 degrees C and 150 degrees C identified as the sigma-relaxation often associated with short range ion mobility. In nanocomposite films, the sigma-relaxation process overcomes the alpha-relaxation process so that the glass transition is no longer detected. The dielectric nonlinear properties (tunability) shown an increase of dipolar moment with AuNPs additions and this results are in good correlation with matrix modification in FTIR investigation. (C) 2014 Elsevier Ltd. All rights reserved.