An approach to produce single and double layer graphene from re-exfoliation of expanded graphite

Abstract

We report the production of high quality single and double layer graphene from sonication and centrifugation of re-exfoliated expanded graphite (EG) in an organic solvent. The prepared graphene-sheets are identified by Ultraviolet–visible spectroscopy and characterized using different techniques. Transmission and scanning electron microscopy observations show that the graphene-sheets have an area of ∼(12 × 10) μm 2. The selected area electron diffraction analysis and Raman spectroscopy have confirmed the presence of single layer graphene-sheet. The I(2D)/I(G) ratio from the Raman spectrum of graphene is found to be ∼1.7 which suggests the presence of single and double layer graphene. Scanning probe microscopy studies reveals that on re-exfoliation of EG, thickness of graphene layer decreases from 6–7 nm to 0.75–1.075 nm. This suggests that re-exfoliation overcomes the problem of insufficient oxidation or inadequate pressure that builds-up during first thermal exfoliation of graphite intercalated compound. The photoluminescence spectrum of graphene shows the emission of blue light at ∼390 nm which indicates the presence of some functional groups. These graphene-sheets should facilitate the manipulation and processing of graphene based material for various applications.