▎ 摘　　要

In this study, we report a green and eco-friendly method for direct synthesis of graphene sheet from natural graphite under simple conditions and in situ anchored with MnO2 via an environmental route. A wet mechanochemical approach is used to exfoliate the graphite to graphene sheet by using citric acid as a non-toxic and friendly intercalator agent instead of strongly corrosive acids such as sulfuric and nitric acids at the shortest time and environmental condition. We carried out various microscopic and spectroscopic measurements such as UV-visible spectroscopy, Fourier transform Infrared (FT-IR), Thermogravimetric Analysis (TGA), X-ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FESEM), Transmission Electron Microscopy (TEM) Atomic Force Microscopy (AFM) and Handle Raman Microscopy to confirm the exfoliation of natural graphite to graphene under mild condition. Moreover, we took nanoindentation test for investigation of mechanical properties of graphene sheets. The hardness and elastic modulus obtained from this analysis are about 4.1 and 37.2 GPa, receptivity. At the following work, one pot preparation of graphene-MnO2 nanocomposite can be performed on the large scale and be utilized in a wide variety of applications. This synthesis, which is economically suitable, is performed without any reduction agent and much purification. Facile synthesis of graphene and graphene-MnO2 nanocomposite via a green and simple way makes it scalable to apply in many fields. (C) 2017 Elsevier B.V. All rights reserved.