Facile spectroscopic approach to obtain the optoelectronic properties of few-layered graphene oxide thin films and their role in photocatalysis

Abstract

Herein, we report the synthesis of few-layered graphene oxide (GO), reduced graphene oxide (rGO), and rGO/ZnO thin films on a glass substrate by the combination of spin coating, low temperature thermal annealing, and radio frequency (RF) sputtering. A spectroscopic approach was applied for the very first time to calculate the optical and dielectric properties of GO thin films. The GO thin film was characterised for structural, optical, morphological, and surface chemical state composition properties by X-ray diffraction, UV-visible spectroscopy, atomic force microscopy, field emission scanning electron microscopy, and X-ray photoelectron microscopy. The chemical state analysis of O1s and C1s spectra evidently proved the successful reduction of GO at 200-300 °C. The change in grain size, lattice strain, and dislocation density was studied after the reduction of GO to rGO, and the band gap analysis was performed through Tauc plot relation. The optical conductivity of the GO films was estimated by the UV technique. Moreover, the dielectric constant and dielectric loss of GO and rGO thin films were also studied, and the samples annealed at high temperature showed comparatively low loss. Due to the high conductivity and low band gap of few-layered rGO, its composite with RF-sputtered ZnO (rGO/ZnO) was studied for its ability to photocatalytically degrade 2-chlorophenol.