Green reduction of graphene oxide using eucalyptus leaf extract and its application to remove dye

Reduction of graphene oxide (RGO) utilizing green methods such as plants has attracted much attention due to its efficiency, eco-friendly features and low cost. However, the key components in plant extracts and their bioreduction functions concerning GO are still not well understood. In this study, the GO was reduced by Eucalyptus leaf (EL) extract. The optimal conditions for bioreduction were at volume ratio of leaf extract (10 g L^-1) and GO (0.5 g L^-1) solution of 1:4 for 8 h at 80 °C. The RGO was characterized with Scanning Electron Microscopy (SEM), Energy Dispersive X-ray Spectroscopy (EDS), transmission electron microscopy (TEM), and Fourier Transform Infrared Spectroscopy (FTIR). Results confirmed the oxygen-containing groups in GO were efficiently removed, formation of capping layer on the surface of RGO, and good dispersion of RGO in aqueous solution. Furthermore, biomolecules were identified by Gas Chromatography-Mass Spectrometer (GC-MS), where eucalyptols, aldehydes, terpineols, alcohols, amides and ethers of Eucalyptus leaf extract may act as reducing and capping agents for the formation of RGO. Finally, the methyl blue (MB) adsorption on EL-RGO, activated carbon, graphite powder and commercial graphene were investigated separately. The order of the maximum adsorption capacity of different adsorbents emerged as: EL-RGO > commercial graphene > activated carbon > graphite powder.