Synthesis and Dielectric Relaxation Spectroscopy of Graphene Oxide Nanoparticles: Effects of Frequency, Thickness, and Temperature
Graphene oxide (GO) nanoparticles were synthesized by the modified Hummers method from graphite powder. The synthesized GO nanoparticles were characterized by UV–visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), and Raman spectroscopy. The SEM and HRTEM analysis showed that the nanoparticles ranged in size from 1 nm to 100 nm. The crystalline properties of the GO sheets were confirmed by XRD analysis. The FTIR results confirmed the presence of oxygen-containing functional groups on the surface of GO nanosheets. The dielectric relaxation spectroscopy of the synthesized GO was studied in the frequency range of 10−2 Hz to 105 Hz. The dielectric loss tangent as a function of frequency shows a separate relaxation peak and increases up to 6 mm thickness, beyond which it decreases. The dielectric permittivity increases with the thickness of GO pellets up to 6 mm and then decreases, which may be due to an increase in resistivity. The electrical conductivity of GO increases continuously with increasing temperature, confirming the positive temperature coefficient (PTC) of higher conductance. From the dielectric study, it is observed that the dielectric permittivity and electrical conductivity of GO strongly depend upon the thickness and extent of temperature.