Electrical properties in pmma/carbon-dots nanocomposite films below the percolation threshold

An investigation of the thermal, electrical and dielectric properties of original nanocomposite materials based on the incorporation of carbon dots, synthesized in organic solvents, in a poly(methyl methacrylate) (PMMA) is presented. Thermal analysis was performed using differential scanning calorimetry. Electrical and dielectric measurements were carried out in the frequency range from 100 Hz to 1 MHz and at temperatures between 200 and 400 K. The data were analyzed using two formalisms: (i) AC conductivity that has been found to follow the Jonscher’s power law with double exponents, and (ii) electric modulus that permits to identify two dielectric relaxation processes. The first one, appearing at low-frequency, was attributed to the conduction effect which is consistent with the Havriliak-Negami model, and the second one, appearing at high-frequency was associated with the interfacial polarization effect. Furthermore, the analysis of the temperature dependence of AC conductivity using the Arrhenius representation indicated the existence of two mechanisms basically governing the conductivity.