??
第26卷??第1期2011年2月新??型??炭??材??料NEWCARBONMATERIALSVo.l26??No.1
??
Feb.2011
ArticleID:??1007??8827(2011)01??0021??05
Preparationofgraphenenanosheetsthroughdetonation
WANGCan,??ZHANLiang,??QIAOWen??ming,??LINGLi??cheng
(StateKeyLaboratoryofChemicalEngineering,EastChinaUniversityofScienceandTechnology,Shanghai
200237,China)
Abstract:??Graphenenanosheetsweresynthesizedusinggraphiteoxideasaprecursorbydetonation.Thecomposition,
andstructureofgraphenenanosheetswerecharacterizedbyX??raydiffraction,X??rayphotoelectronspectroscopy,scan??ningandtransmissionelectronmicroscopy,selectedareaelectrondiffraction,andRamanspectroscopy.Resultsindicatedthattheas??preparedmaterialwastransparentandwrinkled,andcomprised2??5grapheneswithahighlycrystallinestruc??ture.Theexfoliationandreductionofgraphiteoxidetographenenanosheetswasinducedbytheself??generatedthermalenergyandshockwaveofdetonation.Keywords:??Graphenenanosheets;Graphiteoxide;Detonation;Exfoliation
+
CLCnumber:??TQ127.11Documentcode:??A
1??Introduction
Grapheneisasheetofcarbonatomsboundto??
2
getherwithdoubleelectronbonds(calledasspbond)inathinfilmonlyoneatomthickandisabas??icbuildingblockforzero??dimensionalfullerenes,one??dimensionalcarbonnanotubes,andthree??dimen??
[1]
sionalgraphite.SinceitsdiscoverybyNovoselovandGeimin2004,ithasattractednumerousinvesti??gationsintoitsnovelfundamentalpropertiesandprac??
[2]
ticalapplications.Owingtoitshighvaluesofmob??ilityofchargecarriers,specificsurfaceareaandYoung??smodulus,grapheneandchemicallymodifiedgraphenearepromisingcandidatesascomponentsinapplicationssuchasnanoelectronicdevices,energy
[3??5]
storagematerials,andpolymercomposites.
????Manyapproacheshavebeendevelopedtopreparegraphenematerials,mainlyincludingmicromechani??calorchemicalcleavageofgraphite,epitaxialgrowthonsiliconcarbideoronmetalsubstrates,andbottom??
[6??11]
upapproachesbychemicalsynthesis.However,reproducibleproductionofgraphenesheetsinbulkquantityisstillachallenge.Recently,Schnieppandcoworkersreportedamethodtoproducefunctional??izedsinglegraphenesheetsinbulkquantitiesthroughthermalexpansionofgraphiteoxide(GO).ThemechanismofexfoliationismainlytheexpansionofCO2evolvedintotheintersticesbetweenthegraphene
??Receiveddate:2010??12??02;??Reviseddate:2011??02??13
sheetsduringrapidheating.Itiswellknownthat
afastdecompositionofexplosivescanproducehightemperatureandpowerfulshockwave.Makinguseofdetonationtechnologytopreparegraphitenanopow??
[14]
dershasbeenexplored.
????Herein,wepreparedgraphenenanosheets(GNS)bydetonation,involvingcompleteoxidationofnaturalgraphite(NG),rapiddecompositionofex??plosives,andexfoliationofGO.Theas??preparedGNSweresystematicallycharacterized,andtheexfo??liationmechanismofGOwasproposed.
[12??13]
2??Experimental
GOwaspreparedfromflakeNG(~30??m,HuayiCo.,Ltd,Shanghai)byamodificationof
[15]
Staudenmaiermethod.NG(5g)wasreactedwithconcentratednitric(45mL)andsulfuricacid(90mL)withpotassiumchlorate(55g).Thereac??tionflaskwasplacedinanicebath,andthepotassi??umchloratewasaddedslowlytoavoidsuddenin??creaseintemperature.Thereactionwasallowedtoholdfor120htofullyoxidizeNGintoGO.TheGOwasthoroughlywashedwithdeionizedwateruntilthepHofthefiltratewasneutra.lTheGOslurrywasdriedandstoredinavacuumovenat60 untiluse.????ExfoliationofGOpreparedabovewasperformedbyplacingpremixedGO(2g)andpicricacid(2g)
??Foundationitem:NationalNaturalScienceFoundationofChina(50730003),ProgramforNewCenturyExcellentTalentsinUniversity(NCET-07-0285)andtheFundamentalResearchFundsfortheCentralUniversities.
??Correspondingauthor:LINGLi??cheng.E??mai:llchling@ecus.tedu.cn
??Authorintroduction:WANGCan(1983-),male,Ph.D.,engagedintheresearchofcarbonnanotubesandgraphene.
E??mai:lwhcj021@yahoo.com.cn
??EnglisheditionavailableonlineScienceDirect(http:????www.sciencedirec.tcom??science??journal??18725805).??DOI:10.1016/S1872??5805(11)60063??2
!22!
??新??型??炭??材??料第26卷
inasealedstainlesssteelpressurevessel(10mL).Thedetonationwasinducedbyarapidheating(50 /min)to200 .Whenthedetonationoccurs,about20MPapressure(shockwave)and900 tem??peratureweregeneratedinsidethevesse.lAfterthedetonation,thevesselwascooledinair,gaseousproductsgeneratedwerereleased,andthesolidprod??uctswerecollected.
????X??raydiffraction(XRD)measurementswereperformedusingaRigakuD/max2500XX??raydif??
o
fractometeroperatedwithastepsizeof0.02withCuK??radiation.Scanningelectronmicroscopy(SEM)wascarriedoutonaFETQuanta200FEG.Transmis??sionelectronmicroscopy(TEM)andSelectedareaelectrondiffraction(SAED)wascarriedoutonaFEI
2
TECNAIGS??TWINoperatedat200kV.RamanspectroscopywasperformedbyusingaRenishawMi??cro??Raman2000with514nmargonionlaser.X??rayphotoelectronspectroscopy(XPS)wasperformedonaKratosAXISUltrausingMganode.
Fig.1??XRDpatternsofNG,GOandGNS
3??Resultsanddiscussion
3.1??XRDpatterns
Forasuccessfulexfoliation,itisessentialtocompletelyeliminatetheintergraphenespacingassoci??atedwithNGduringtheoxidationstage.TheXRDpatternsofNG,GO,andGNSareshowninFig.1.NGshowedasharpandintensivepeakat2 =
o
26.6,indicatingahighlyorderedcrystalstructurewithaninterlayerspacingof0.336nm.Afteroxida??tionfor120h,the002diffractionpeakofNGdisap??peared,revealingafulloxidationofNG.Theinter??layerspacingofGOwas0.81nm,whichisclosetothereportedvalueof0.83nmdependingontheratiobetweenGOandwater.Theincreaseintheinterlayerspacingshouldbeattributedtotheoxygen??containingfunctionalgroupsbondedtothegrapheneshee.tIncontras,tnoapparentpeaksweredetectedinthepat??ternfortheas??preparedGNS,indicatingacompleteeliminationofstackedlayerstohighdegreeofexfoli??ation.Thisfeatureissimilartothatofchemicallyre??
[16]
ducedgraphene.3.2??SEMandXPSspectra
Figs.2aand2bshowtheSEMimagesofNGandGO,respectively.Duringtheoxidationprocess,thesizesofNGflakesdecreasedfrom30to10??mofGO.AlthoughtheinterlayerspacingofGOisroughlywiceofNG,thesurfacemorphologywasnott
changedseriously.Theappearanceofbrightedgesandsmoothstagesacrosstheareaarisesfromthepres??enceofoxygenatedfunctionalgroups.Fig.2cshowstheSEMimageofGNSderivedfromthedetonation
ofGO,withanexpanded,looseandporousstruc??
ture.Thetopview(Fig.2d)ofGNparticlerevealstheagglomerationofrippledsilk??likeGNS.Thesideview(Fig.2e)ofGNparticlefurtherconfirmstheappearanceoftransparentGNSwithwrinklesandfolds.Comparingwiththeworm??likestructureofex??foliatedgraphitereportedabove,suchGNSgavemuchthinnerthicknessandhigherdegreeofGOexfo??
[17]
liation.
XPSanalysiswascarriedouttoinvestigatetheelementcompositionofGOandGNS,asshowninFig.2f.Twopeakscenteredat284.5eVand532.6eVcanbeassignedtoC1sandO1ssignals.QuantitativeanalysisofGOshowedaC/Omolarratioof2/1,attributedtotheoxygen??containingfunc??tionalgroupsattachedtothegraphenesheets,which
[7]
isconsistentwiththeliteraturereport.ForGNSob??tainedfromdetonation,XPSgaveaC/Omolarratioof10/1,whichresultedfromthedecompositionofoxygengroups.Suchanoxygencontentissimilartothatofhydrazine??reducedgrapheneoxide,indicatingthereductionofGOinthedetonationprocess.3.3??TEMandSAEDpattern
Figs.3aand3bshowtheTEMimagesofas??pre??paredGNS.ThetransparentGNSwerecorrugatedwithsizeofafewsquaremicrometers.Thelowcon??trastfeatureindicatesthesmallthickness.Thecorru??gationisintrinsictoGNS,whichresultsfromthefactthatthe2Dmembranestructurebecomesthermody??namicallystableviabending.Fig3cshowsahigh??resolutionTEMimageofasinglegraphene.Thevisi??blegraphiticlatticesrevealedthattheGNSonlycon??sistof2??5graphiticlayers.TheSAEDpatternofthefeaturelessregionshowsthetypicalhexagonallyor??deredlatticeofcarboningraphene(Fig.3d).Thesharpdiffractiondotsconfirmthehighcrystallinestructureoftheas??preparedGNS.TheintensityratioofI{1100}/I{2110}<1isauniquefeaturefor第1期WANGCaneta:lPreparationofgraphenenanosheetsthroughdetonation??
!23!
Fig.2??SEMimagesof(a)NG,(b)GOand(c)GNSparticle.(d)Topviewand
(e)SideviewofGNparticleshownin(c).(f)XPSspectraofGOandGNS
Fig.3??(a,b)TEMand(c)highresolutionTEMimagesofGNS.(d)SAEDpatternoftransparentregion
multilayergraphene.Therefore,theTEMand
SAEDresultsdemonstratedthattheobtainedGNSweregraphenewithafewlayers.3.4??Ramanspectroscopy
Ramanspectroscopyisapowerfulnondestructivetooltocharacterizecarbonaceousmaterials.TheG
2
bandcorrespondstotheE2gphononsofCspatoms,whereastheDbandisabreathingmodeork??pointphotonsofA1gsymmetry.TheintensityratioofDandGbands,ID/IG,isameasureofdisorderdegreeand
2
averagesizeofthespdomains.Fig.4showsRamanspectraofNG,GO,andGNS.NGexhibitedastrong
-1
Gbandat1582cmandarelativelyweakDbandat
[18]
1350cm.ForGO,theGbandbroadenedsignifi??cantlyandshiftedupwardtohigherfrequencyof
-1
1595cm,andID/IGincreasedto1.5,indicating
2
thereductioninsizeofthein??planespdomainsduetotheextensiveoxidation.ForGNS,theGband
-1
sharpenedandshiftedbackto1585cm,andID/IGdecreasedto0.75,indicatingtherestoreofthein??plane2
spdomains,duetoagraphitic?self??healing#inheattreatmen.tThe2DbandisthemostprominentfeatureintheRamanspectrumofgraphene,anditspositionandshapearesensitivetothenumberoflayersofgra??
[19]
phene.TheGNSexhibitedasingle,symmetrical2D
-1
bandat2700cm,correspondingtothegraphenewithafewlayers.TheRamanresultsprovidefurther-1
!24!
??新??型??炭??材??料第26卷
Fig.4??RamanspectraofNG,GOandGNS,intheregionofthe(a)DandGbandsand(b)2Dbands
evidencetothesynthesisofgraphenewithafewlay??ersbydetonation.3.5??Mechanismofexfoliation
Basedontheaboveanalysis,theexfoliationmechanismofGOisproposedinFig.5.Firs,tNGwascompletelyoxidizedintoGO,resultinginabun??dantoxygen??containingfunctionalgroupsbondedtothebasalplanesofthegraphitestructure.Second,thedetonationofGOwasinducedbyarapidheatingandtheself??generatedenormousthermalenergyandapowerfulshockwaveatamicrosecondscale.Las,tGOwasrapidlyheatedtohightemperatureanditsox??ygen??containingfunctionalgroupsdecomposedintoCO2andH2O.Theexpansionofthegasesevolvedin??totheintersticesbetweentheadjacentgraphitesheetsresultedintheexfoliationofGO.ThereductionofGOwassimultaneouslycompletedaccompaniedwiththedecompositionoffunctionalgroups.Theshock??waveformedduringthedetonationshearedGOintosmallfragments.
Acknowledgment
ThisworkhasbeensupportedbytheNationalNaturalScienceFoundationofChina(50730003),ProgramforNewCenturyExcellentTalentsinUni??versity(NCET??07??0285),andtheFundamentalRe??searchFundsfortheCentralUniversities.
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爆炸法合成石墨烯
王??灿,??詹??亮,??乔文明,??凌立成
(华东理工大学化学工程国家重点实验室,上海200237)
摘??要:??以石墨氧化物为前躯体,采用爆炸法合成石墨烯。利用XRD,SEM,XPS,TEM,SAED和Raman等测试手段对石墨烯的形貌,成份和结构进行表征。结果表明,石墨氧化物在爆炸产生的热量和冲击波的作用下发生完全剥离并被还原成石墨烯。新合成的石墨烯呈透明褶皱状,含有2层~5层石墨层,并具有较好的晶体结构。关键词:??石墨烯;石墨氧化物;爆炸;剥离
基金项目:国家自然科学基金(50730003),教育部新世纪优秀人才支持计划(NCET-07-0285),中央高校基本科研业务费专项资金.通讯作者:凌立成.E??mai:llchling@ecus.tedu.cn
作者介绍:王灿(1983-),男,湖北人,博士,主要从事纳米碳管和石墨烯的研究.E??mai:lwhcj021@yahoo.com.cn
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