Enhanced visible-light photocatalytic activity of rGO-ZnO composite thin films prepared by SILAR method

This study reported the first-time preparation of reduced graphene oxide (rGO) and zinc oxide (ZnO) composite (rGO-ZnO) thin films through successive ionic layer adsorption and reaction (SILAR) method. The effects of rGO and heat treatment on the structural, morphological, chemical, optical, vibrational and photocatalytic properties of composite films were investigated. The structural results showed that ZnO and rGO-ZnO thin films could be obtained without heat treatment. The rGO-ZnO composite showed improved crystallinity and homogeneity compared to ZnO, with formation of flower-like structures. The presence of graphene derivatives in the composite films was validated using Raman spectroscopy. Chemical composition analysis showed an increase in the carbon content in rGO-ZnO composite. Optical transmittance in the visible range was reduced from 90% for ZnO to 51% for rGO-ZnO. Moreover, the bandgap energy of ZnO decreased from 3.33 to 3.04 eV with the presence of rGO and heat treatment. The rGO-ZnO composite thin films exhibit enhanced visible-light photocatalytic discoloration of Orange G dye, which is attributed to bandgap narrowing with improved visible light response and charge separation. The approach described here provides a simple and efficient way to synthesise rGO-ZnO composite thin films with potential applications for a wide range of environmental issues.