石墨烯

Preparationofpolyvinylpyrrolidone-decoratedhydrophilicgrapheneviainsituballmillingJuxiangLin1•DanqingChen1•JingDong1•GuohuaChen1Received:9June2015/Accepted:20August2015/Publishedonline:1September2015SpringerScience+BusinessMediaNewYork2015AbstractGraphenesheetswereprocessedbyinsituball-millinggraphiteflakesinanethanolsolutionofpolyvinylpyrrolidone(PVP).Resultsshowedexfoliationofgraphiteintographene,withsurfacesdecoratedwithPVP.ThisnewPVP-functionalizedgraphenecouldbefurtherdispersedinvarietiesofpolarsolvents,includingethanol,dimethylformamide,andwater.Resultinghomogeneoussolutionhasmorethan4monthsofstoragestability,withthehighestconcentrationofgraphenereaching1.7300mg/ml.IntroductionGraphenehasattractedtremendousattentionssinceitsdiscoverybyNovoselovandGeimin2004[1].Thisuniquematerialhasfoundusesinmanytechnologicalfields,suchasnanoelectronics,devices,energystorage,sensors,andnanocomposites[2–4].Amongthem,theresearchingra-phene-basednanocompositesisoneofthemostpromising.Forexample,graphenecansignificantlyimprovetheelectricalandmechanicalpropertiesofpolymer[5].Unfortunately,likecarbonnanotubesandmanyothernanomaterials,graphenesheetshaveahighsurfaceareaandsurfaceenergy,easilyresultingintheformationofagglomerates[6].Toeliminateoralleviatesuchanissue,thereareeffortstomodifygraphenewithvarietiesofchemicals,byformationofcovalentlyornon-covalentlybondedsurfaces[7–10].Frequently,thesemodificationsrequiretoxicchemicalsandinvolvecomplicatedproce-dures.Asaresult,neitheraretheygreennorenergysaving.Recently,mechanochemicalstrategyofmillingprocesseshasbeenappliedtogenerategraphenefrombulkgraphite[11].Somereportssuggestedagooddispersibilitycanbenefitaftertheprocess.Forinstance,Jeonetal.[12]preparededge-functionalizedgraphenenanosheetsinthepresenceofdryice.Theproductswerehighlydispersableinsolvents.Similarly,hydroxyl-functionalizedgraphenesheetswereexfoliatedfromgraphitebyYanetal.inthepresenceofpotassiumhydroxide[13].Ourgrouppreparedpolystyrene(PS)-functionalizedgraphenenanosheetsbyballmilling[14].ResultinggraphenenanosheetscanbefurtherdispersedinPSmatrixandshowedanextraordi-naryelectricalproperty.Comparedwithothermodificationapproaches,mechanochemicalapproachintegratesprepa-rationandfunctionalizationofgrapheneinone-stepandthereforeisbothstraightforwardandenvironmentallyfriendly.PVP,asawater-solubleandbiocompatiblepolymer,hasbeenusedasadispersantinvariousfieldssuchastextiles,pharmaceuticals,cosmetics,andadhesives[15].Recently,ithasalsobeenreportedthatPVPcanbecoatedontographenesurfacestopreventtheaggregation.Forinstance,Bourlinosetal.usedsonicationtocoatPVPoversurfacesofgraphene[16].Inspiredbythiswork,weextendtheElectronicsupplementarymaterialTheonlineversionofthisarticle(doi:10.1007/s10853-015-9373-6)containssupplementarymaterial,whichisavailabletoauthorizedusers.&[e-mail][e-mail]@[e-mail]1DepartmentofPolymerScience&Engineering,HuaqiaoUniversity,Xiamen361021,People’sRepublicofChina123JMaterSci(2015)50:8057–8063DOI10.1007/s10853-015-9373-6surfacetreatmentstrategywithball-millinggraphiteinsideasolutionofPVP.Wefoundtheresultinghydrophilicgraphenecanbeeasilydispersedinpolarorganicsolventsandwaterathighconcentrations.ExperimentalsectionMaterialsGraphitepowder(8000mesh)wasplacedinadesiccatorpriortouse.Anhydrousethanol,N,N-dimethylformamidewerepurchasedfromGuangdongXilongChemicalReagentCo.,Ltd.Polyvinylpyrrolidone(PVP)wasobtainedfromSinopharmChemicalReagentCo.,Ltd,China.Otherrawmaterialswereusedasreceived.Experimentalset-upTheballmillingwascarriedoutinaverticallystirredmill,withdetailsshowninFig.A1(supplementarydata1).Rotationalspeedofthestirrerwasadjustedcontinuouslyfrom90to1300rpm.Wear-resistantzirconiamillingbeads,withdiametersof0.5–5mm,wereusedasgrindingmedia.Preparationofpolyvinylpyrrolidone-decoratedhydrophilicgraphenesheets(PVP-GS)Graphiteflakes(1.0g)andPVP(0.005g)wereweightedandpremixedinastirringballmill(Fig.1a).Then40mlethanol(EtOH)wasaddedandthemixturewassubjectedtoacontinuousballmillingat90rpmforupto48h(zirconiamillingbeads,200g)(Fig.1b).Finalmixturewasdispersedinethanol(100ml)andfilteredthrougha0.22-lmPTFEmembrane,followedbyrinsingwithwateratleast5times(Fig.1c)andthendriedinavacuumovenat80Cforfurtheruse.CharacterizationSampleswerecharacterizedbyScanningElectronMicro-scopy(SEM),High-resolutionTransmissionElectronMicroscopy(HRTEM),X-raydiffraction(XRD),andRamanspectroscopy.SEMwastakenonaJSM-6700Ffield-emittingscanningelectronmicroscopewithanoper-atingvoltageof5kV.Thedistancebetweenthesampleanddetectorwas7.5mm.High-resolutiontransmissionelectronmicroscopy(HRTEM)imagesweretakenwithH-7650(HITACHI)todeterminethelayersofthegraphenesheets.X-raydiffraction(XRD)patternswererecordedwithaD8-Advanceinstrument(BrukerAXS)usingCuKaradiationgeneratedatavoltageof40kVandacurrentof40mA.Therangeof2hwasfrom5to40withascan-ningrateof5perminute.RamanspectroscopywastakenwithaHe–Nelaser(532nm)astheexcitationsource(SuperLabRamIIsystem).Fouriertransforminfrared(