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Preparation, Properties, and Applications of Low-Dimensional Molecular Organic Nanomaterials

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Preparation, Properties, and Applications of Low-Dimensional Molecular Organic Nanomaterialsof,and

Preparation, Properties, and Applications of

    Low-Dimensional Molecular Organic

    Nanomaterials

    JOURNALOFELECTRONICSCIENCEANDTECHNOLOGYVOL.8,NO.1,MARCH2010

    Preparation,Properties,andApplicationsof Low-DimensionalMolecularOrganicNanomaterials Jun-ShengYu,Zhao-LmYuan,GuangZhongXie,andYa-DongJiang (Invitedpaper)

    Abstracfnrecentyears,greatprogresshasbeen

    madeinresearchanddevelopmentofsmal1.molecule organicmaterialswithvariouslow-.dimensionalnano. structures.Thispaperpresentsacomprehensivereview ofrecentresearchprogressinthisfield,including preparation,electronicandoptoelectronicproperties andapplications.First,anintroductiongivestothe reprecipitation,softtemplatesmethods,andprogressin synthesisandmOrphOlOgicalcontroloflow.dimensional small-moleculeorganicnanomaterials.Theirunique opticalandelectronicpropertiesandresearchprogress intheseaspectsarereviewedanddiscussedindetail. Applicationsbasedonlow-dimensionalsmal1.molecule organicnanomaterialsarebrieflydescribed.Finally, someperspectivestothefutnredevelopmentofthisfield areaddressed.

    /ndexTerms---Low-dimensionalnanostruetures,

    on/offfluorescenceswitches,optoelectronicproperties, reprecipitationmethod,small-moleculeorganic

    nanomaterials.

    doi:10.39690.issn.1674862X.2010.01.001

    1.Intr0ducti0n

    Overthepasttwodecades,nanoscienceand

    technologyhavebeendevelopedrapidly,andasignificant progresshasbeenmade.Amongthem,alotofattentionhas beendrawntonanomaterialsduetotheirquantumsize

    effect["

    ,

    quantumconfmementeffects[,

    surfaceeffectpl,

    quantumtunnelingeffectt4j,andsoon.Theseeffectsresult inuniquepropertiesnal1omaterialssuperiortothoseof

    tl1eirbulkcounterpartsIJ.Therefore.thenanomaterialshave

    stimulatedlotsofresearchinterest.Uptilnow.,llano

    ManuscriptreceivedDecemberl5,2Oo9:revisedJanuary10, 2010.

    ThisworkwaspartiallysupportedbytheNationaINaturalScienceFound. ationofChina(NSFC)underGrantNo.60736005and60425101.1.tlle FoundationforInnovativeResearchGroupsoftheNSFCunderGrantNo 60721001,ProvincialProjectundergrantNo.9140A02060609DZ0208 andNo.20090185110020,ProgramforNewCenturyExcellentTalentsin UniversityunderGrantNo.NCET-06.0812andNo.08.0088.SRFfor ROCS,SEMunderGrantNo.GGRYJJO8.05.andYoungExcellent ProjectofSichilanProvinceunderGrantNo.09ZQ026-074. J.-S.l'Z.?L.Yuan,Q-Z.Xie,andY-D.JiangarewithStateKey LaboratoryofThinSolidFillandIntegratedDevices.Schoo1of OptoelectronicInformation,UniversityofElectronicScienceand

    TechnologyofChina,Chengdu,610054,Chinafe.mail: jsyu@uestc.edu.cn)

    Fromtheviewpointofmaterials,ingeneral,nanoma- terialscanbedividedintoinorganicmaterials,macromole. cularmaterialsandsmall-moleculecompounds.Todate, inorganicnanomaterialshavebeenmostwidelyinvesti- gated,moreove~greatachievementshavebeenobtainedin variousaspects,includingpreparation,shapecontroll2J,

    morphology-dependentpropertiesl3,

    andapplications[.f.

    Anotherimportantareaofnanomaterialsisthose composedofmacromolecular-polymer,graphenehasalso beenstudiedextensivelyinrecentyears.Asmanykindsof polymernanomaterialssuchaspolyprroleandpolyaniline havegoodoptoelectronicproperties,environmentalstability, andpotentialapplicationinbiomedicinet.optoelec. tronicsl,andetc.,manyscientistspaidmuchattention tothesenanomaterials.Recently,graphenewithnano. structuressprangupgraduallyduetotheirex~aordinary electronic,thermal,mechanicalproperties,andpotential applicationsinvarioustechnologicalfieldst7l?.J Besidesinorganicandmacromolecularnanomaterials, smallmoleculeorganicnanomaterialshavebeenaresearch subject.SinceNakanashiandco.workersfirstfabricated smallmoleculeorganicmicrocrystalsbyarepreciFIitation methodin1992t.moreandmoreresearchattentionhas beenpaidtosmall-moleculeorganicnanomateialsbecause Oft}leirinterestingproperties[01-[30landpotentialappli. cationsinvariousfields,suchasopticalwaveguidest~j,and

optoelectronicdevicespJ.2L341'4o.Sofar,sOmeclassesOf

    smal1.moleculeorganicnanomaterials,e.g.,perylene[20J_231,

    pyreneL,andsoon,havebeensuccessfullypreparedand theirpropertiessuchasopticaland/oreleconicproperties

    havealsobeeninvestigatedindetail.Recentl~interestingly, someapplicationsbasedonsmallmoleculeorganicllano.

    materialshavebeenreported[3~1.401.HoweveLCUlTent

    researchprogressinsmall-moleculeorganicnanomaterials lagsfarbehindtheirinorganiccounterparts,whichmay mainlybeascribedtotwofactors.Ontheonehand.itis verydifficulttopreparesmallmoleculeorganicmaterials

    intolongtermstablenanostructuresduetotheirthermal instability,poormechanicalpropertiesandlowmelting temperatures.Ontheotherhand,owingtooptoelectronic propertiesofsmall-moleculeorganicnanomaterialswith relatedtochargetransferexcitons[28JandFrenkel excitons.theiroptoelectronicpropertiesaremorecom. 4JOURNALOFELECTRONICSCIENCEANDTECHNOLOGVOL.8,NO.1,MARCH2010

    plicatedcomparedtothoseofinorganicnanomaterials, whichresultinmanydifficultiesofresearchinsmal1. moleculeorganicnanomaterials.Asresearchersmadegreat effortsandadeeperunderstandinginthisarea.rapid developmentofsmal1.moleculeorganicnanomaterialsis underway.

    Itisworthytopointoutthatmorphologiesof

    nanomaterialshavegreatinfluenceontheirspecific properties.Inparticular,differentmorphologiesofsmall

    moleculeorganicnanomaterialsshowquitedistinct properties,e.g.,zero.dimensional(0D)smal1.

    moleculeorganicnanostructuressuchasnanoparticles displayedsize.dependentopticalproperities[23I28Optical

    andeleconicpropertiesofnanomaterialswithvarious dimensionalnanostructureswereobviouslydifferenttJ. Therefore.morphologicalmanipulationofsmallmolecule

    organicnanomaterialsisnecessaryforpracticalapplica

    tions[26,'Thisindicatesthatlotsofeffortshouldbepaid toobtainthedesiredmorphologiesbypropersynthetic strategy

    Inthisarticle.wereviewtherecentresearchprogress matmainlyfocusesonsmal1.moleculeorganicmaterials withlow.dimensionalr0DandlD1nanostructures.This reviewisorganizedasfollows.Section2elaborates commonpreparationroutesoforganicnanomaterials includingreprecipitationandsofttemplatesmethods.In Section3,optoelectronicpropertiesofsmal1.molecule organicnanomaterialsareilluminatedindetail.Section4 brieflyliststheirapplicationsinoptoelectronicfield.Finally, wedrawasummarizationandpredictthefuture

    developmentofstudyinthisfield.

    2.PreparationMethods

    uptonow,somemethodshavebeenusedtofabricate smal1.moleculeorganicnanomaterialsaccordingto previousreports,suchasthesupercriticalfluidsmethodt41J. 1aserablation[42.

    hardtemplates[29andvapor

    depositiont34.【们.thesemethodsweresummarizedin

    43].451.Herein,wefocusonintroducingthe

    reprecipitationandsofttemplatesme[hodsthatwere conventionallyusedtosynthesizelow.dimensional

smallmoleculeorganicnanomaterials.

    2.1ReprecipitatiOnMethod

    SinceNakanashiandco.workerspioneeredtofabricate organicnanocrystalsviaareprecipitationmethod.this methodhasbeenadoptedtosynthesize0Dand/or1D smallmoleculeorganicnanomaterialsbyseveral groups[19-【】,[2-.l'3?.Thismethodmainlyinvolvesina rapidmixingofasmallamountofthetargetcompound/ goodsolventsolutionwithexcessofapoorsolvent,owing tothesolvophobictendencybetweentargetcompound moleculesandthepoorsolvent,thetargetcompoundwould groworaggregatetotorlTlaspeciticnanostucture. 0bviously,ithassomeadvantagessuchassimplicity, lowcost,andshort-period.

    一一Fig.1.FESEMimagesofas-preparedsomeorganichallO

    structuresbythereprecipitationmethod,whereA:CNMBE

    nanoparticles[4,

    B:perylenenanoparticles471,C:MeSqnano-

    wires[311,

    andD:DMPMPnanoribbons[2.

    Usingthismethod,someclassesoforganicnano

    materialshavebeensuccessfullyprepared,e.g., 1cyano-trans1,2-bis(4'-methylbipheny1)ethylene(CN

    MBnanoparticles[46,

    perylenenanoparticles[o.lI47,

    tetracenenanoparticles,methyl-squarylium(MeSq) nanowiresp",2--dimethylaminopheny1)etheny1]phenyl- methylene.propanedinitrile(DAPMP)nanorib.bons.J.etc. Thetypicalfield.emissionscanningelectronmicroscopy

    (FESEM)imagesareshowninFig.1.Itcanbeseenthat

    as-preparednanostructuresaresmoothanduniform. Moreover,theas-prepared1Dnanostructureshavebeen verifledassinglecrystalline[26,【】bvtheselected.area

    electrondiffraction(SAED)rnotshownhere).Recently,a fewofresearchersextendedtheirinterestsindoping organicnanostructures,somehybridsnanostructuresbased ontwokindsormorethantwokindsofsmal1.molecule organicmaterialswereachievedbythereprecipitation method[4',5050.

    2.2SoftTemplatesMethod

    AlthoughreprecipitationisafacileapproachtoObtain somekindsofsmal1.moleculeorganicnanomaterials.itis onlysuitableforafewkindsofsmal1.moleculeorganic materialstoformnanostructures.Accordingl~many researchersiedtoexploreothermethodssuchassoft

    templatesmethodtosynthesizesmal1.moleculeorganic nanomaterials.Softtemplatesmethodisthatthetarget compoundsolutionentersintotemplatessuchassurfactant micelles[24'3.thenthetargetcompoundisinducedinto nanostructures.Recentl~bysofttemplatesmethod.several groupssuccessfullyfabricatedsomekindsofsmal1. moleculeorganicmaterialswith1Dnanostructuresuchas nanowires,nanorods,andnanofibers[24'32I5l.Fig.2A,B,

    andCshowtheFESEMmorphologiesoftheprepared pyrenenanowires.9.10diphenylanthracene(DPA)

    nanorodsand1,3.diphenyl2.pyrazolineP)nanofibers,

    respectively.Itcanbeobviouslyfoundthattheasprepared

    xties,andApplicationsofLow-DimensionalMolecularOrganicNanomaterials

    veryregular,whichoriginatefromEspecially,asfaraspotentialapplicationsinvarious

    :factantmicelles.Fig.2Ddisplaysoptoelectronicdevicesareconcerned,

manyresearchersare

    aanorods,theTEMresultsbasicallyveryinterestedinoptica1.electronicandoptoelectronic gYobservedwithSEM(Fig.2B).propertiesofsmal1.moleculeorganicnanomaterials.Itwas DdepictsSAEDpatternsofDPAfoundthattheoptical

    ,electronicandoptoelectronic

    D

    ..

    pa.wefoun

    .

    da1

    .ongepropertiesofsmal1.moleculeorganicnanomaterialsare

    LmdlcatetheunitOrmsingle'crystalfundamentallydifferentfromthoseofinorganiccounter.

    ?lnaddition?throughagreatdealofpartsduetoweakintermolecularinteractionforcesofVan dmattheshapeandsizeofthedeWaalsorhydrogenbondstypesinorganicmaterials 'econtrolIedougl1changingtheMoreover

    ,owingtouniqHenanoscalesize,theiroptical,

    rg!compoundto0urlactant?I_heelectronic,andoptoelecnicpr0pertiesarealsoemire1y .

    o^0ancn0ctueandthedifferentfromth0se0ftheirmon0merandbulksolid.With 嚣锄e:sadeeperunderstandingandinvestigatinofsmall-moleculeAhsomegroups242J,

    5?.

    sso,]~mina

    .....

    ng

    ,

    of

    ,,.

    lowertaretcomDound/SurfactantorgnmatenalgreaIprogresSnaSbeenmadem

    itusuallyformsshericalmicells,opt?al,eIeconcandoptoelectron. icpropertie

    .

    s?Intll'

    ;etcompounurfactantmolarratiOs,se .

    ctl0nJ

    .

    wereVlewrecem

    .

    researchprogress1nOpticaJ,

    formrod.1ikemicells.Whichactaselectronlcandoptoelectronlcpropertiesofsmall.molecu

    le

    thetargetcompoundintoIDOanlcnanomaterials? dElectronicProperties

    ;havebeenmadetosynthesize

    afsmallmoleculeorganicmaterials, ~tionsarealsoprincipalresearch '

    as-preparedorganicnanostructuresby hereA:pyrenenanowires[.B:DPA fibers[511.andD:TEMimagesofDPA ?

    ?

    \潦一潦

    Nanoparticles

    esoforganicnanostructuresofdifferent

     [24

    3.1OptiealProperties

    Nakanishietal,tJfirstreportedthesize.dependent

    opticalpropertiesofperylenenanocrystalsinl996.As showninFig.4.itcanbeseenmatopticalpropertiesofthe nanocrystalsareobviouslydifierentfromperylenesolution and/orbulkcrysta1.bOmabsorptionandlight.emitting peaksareblue.shiftedwithdecreasingcrystalsize(spectra AandB).nlisblueshifisconsideredfromtworeasons.

    oneisthechangeoflatticestateandappea.ranceoflattice soiling.asaresul~theCoulombicinter.actionenergy betweenmoleculesbecomessmallet,leadingtowiderband gaps;theotherreasonmaybetheelecicfieldefflectOf

    surroundingmediathroughthesurfaceofmicrocrystals. Subsequently,opticalpropertiesofsomeorganic nanomaterialssuchas9.l0-bis(4.fN-carbazoly1)- pheny1)anthracene(BCPA)[52,CuTCNQI53,transquina.

    cridonetj,l,1,4,4-tetrapheny1.1,3.butadiene(TPB)[5swere studiedindetail.Recently,Yaoeta1.embarkedonafew reseatchworksonopticalpropertiesofsmal1.molecule organicnanomaterials,e.g..meyreportedsize.dependent opticalpropertiesofthenanoparticlesof.3.5

    triphenyl-2-pyrazolinerTP).and1-phenyl-3((dimethy?

    lamino)-styry1)-5?((dimethylamino)pheny1)-2-pyrazoline DDP),size-tunableemissionfromthenanoparticlesof l,3-diphenyl?5-(2?anthry1)-2-pyrazoline(DAP),multiple emissionfromthenanoparticlesOf1.3-diphenyl5

    pyrenyl-2-pyrazoline(DPP)aswelastunableand

    switchableemissionfromdopedoranicnano.

    materials[49I5.Somegroupsfoundthatf1uorescent

    emissionoforganicnanoparticlesaremuchstrongerthan t}latofthesolutionduetothesynergeticeffectofformation J-aggregationandintramolecularplanarizationinorganic

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