Growth and photocatalytic behavior of transparent reduced GO–ZnO nanocomposite sheets

Abstract

Reduced graphene oxide–zinc oxide (rGO–ZnO) nanocomposites were grown on solid substrates by rapid thermal treatment of Langmuir–Blodgett transferred GO–Zn composite sheets in oxygen ambient. The changes induced by uptake of Zn2+ ions and subsequent thermal treatment on surface morphology, micro-structure, composition and optical properties of composite sheets were investigated by atomic force microscopy, high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron spectra (XPS), Fourier transform infrared (FT-IR) and Raman measurements. The morphological features of composites are practically independent of subphase Zn concentration and are largely determined by the temperature of rapid thermal treatment. FT-IR results indicate the presence of zinc carboxylate in composites and HR-TEM results confirm the formation of ZnO nanoparticles upon subsequent oxidation. XPS and Raman measurements show that rapid thermal treatment in oxygen ambient results in decrease of carbon-oxygen functional groups and increase in graphitic carbon content leading to the reduction of GO in the composites. The average optical transmittance of rGO–ZnO composites in the visible region is found to be ∼87%. Photocatalytic studies carried out on methylene blue (MB) overlayer coated rGO–ZnO composites show reduction in concentration of MB with increasing duration of UV irradiation. The transparent two-dimensional rGO–ZnO composite solid state structures thus facilitate efficient adsorption and degradation of MB molecules, without any composite aggregation.