Development of defects in ZnO/RGO composites under wet chemical synthesis

ZnO/reduced graphene oxide (RGO) heterostructures were fabricated using a simple two-step wet chemical technique and post-annealing treatment. ZnO nanoparticles with different sizes (20-200 nm) and shapes were randomly distributed on mono- and/or multi-layered RGO sheets. The microstructures of the ZnO/RGO composites examined using transmission electron microscopy indicated that the heterostructures are polycrystalline in nature, implying the possibilities of diverse defects present in the samples. The photoluminescence spectra examinations revealed the enhancement of defect-level emission peaks observed at a relatively long wavelength ranges (i.e., 779 nm, 666 nm, and 574 nm) as compared with the band to band transition observed at relatively short wavelengths (i.e., 378 nm).