A simple, one-pot, low temperature and pressure route for the synthesis of RGO/ZnO nanocomposite and investigating its photocatalytic activity

Abstract

A simple, low temperature and pressure, catalyst-free reflux method was reported for the synthesis of reduced graphene oxide (RGO)/ZnO nanocomposite (NC). Formation of ZnO Nanoparticles (NPs) on the surface of Graphene oxide (GO) sheets was led to reduction of GO and fabricating RGO/ZnO NC. The photoluminescence (PL) analysis showed two broad and intense peaks in PL spectra of ZnO and RGO/ZnO samples which are assigned to the electronic transition from zinc interstitial levels (IZn) to Zinc vacancy levels (VZn) and from conduction band to the oxygen vacancy levels (VO), respectively. Broad and intense peaks in PL spectra of ZnO NPs synthesized by our method makes many photogenerated e-h pairs in trap levels due to large number of trap levels. Hybridizing ZnO NPs with GO considerably improve photocatalytic activity of samples due to transferring these electrons to GO sheets and preventing e-h recombination. XRD and FT-IR analyses confirmed that the as-obtained NC is in the form of RGO/ZnO instead of GO/ZnO. Synthesizing NCs by this route largely enhanced photocatalytic activity of NCs, because this synthesis route generates many trap state energy levels such as VO, VZn and IZn subband energy levels in the band gap of ZnO NPs. These numerous trap states -compared to that of RGO/ZnO NCs obtained by other methods- play an important role in the photocatalytic performance of synthesized NCs by enhancing the visible light absorption due to the resulting ZnO band gap narrowing.