再剥离膨胀石墨制备石墨烯

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

S.R.Dhakate a ,*,N.Chauhan a ,S.Sharma a ,J.Tawale b ,S.Singh b ,P.D.Sahare c ,R.B.Mathur a

a

Physics and Engineering of Carbon,Division of Materials Physics and Engineering,National Physical Laboratory,Council of Scientific and Industrial Research,Dr.K.S.Krishnan Marg,New Delhi 110012,India b

Division of Material Characterization,National Physical Laboratory,Council of Scientific and Industrial Research,Dr.K.S.Krishnan Marg,New Delhi 110012,India c

Department of Physics and Astrophysics,Delhi University,Delhi 110017,India

A R T I C L E I N F O Article history:

Received 19November 2010Accepted 31December 2010Available online 14January 2011

A B S T R A C T

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 pre-pared 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)l m 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 $1.7which 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 6–7nm to 0.75–1.075nm.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 graph-ene shows the emission of blue light at $390nm which indicates the presence of some functional groups.These graphene-sheets should facilitate the manipulation and process-ing of graphene based material for various applications.

Ó2011Elsevier Ltd.All rights reserved.

1.Introduction

Graphene,as the fundamental two-dimensional (2D)carbon structure with exceptionally high crystal and electronic qual-ity,has emerged as a rapidly rising star in the field of material science.It is the thinnest known and the strongest ever mea-sured material in the universe [1].Graphene,as defined,is a 2D crystal,composed of monolayers of carbon atoms ar-ranged in a honeycombed network with six-membered rings [2]which is the interest of both theoretical and experimental researchers worldwide.The name comes from graphite and

alkene;graphite itself consists of many graphene-sheets stacked together by weak van der Waals forces.This attrib-uted to the monolayer of carbon atoms densely packed into honeycomb structure [3–5].T wo features of graphene make it an exceptional material.First,despite the relatively crude ways it is still being made,graphene exhibits remarkably high quality resulting from a combination of the purity of its carbon content and orderliness of the lattice into which its carbon atoms are arranged.The quality of its crystal lattice is also responsible for remarkably high electrical conductivity of graphene.Its electrons can travel without being scattered

0008-6223/$-see front matter Ó2011Elsevier Ltd.All rights reserved.doi:10.1016/j.carbon.2010.12.068

*Corresponding author:Fax:+911145609310.

E-mail address:dhakate@mail.nplindia.ernet.in (S.R.Dhakate).