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Citethis:J.Mater.Chem.C,2015,3,2086

Multifunctionalpolypyrene/silicahybridcoatingswithstableexcimer?uorescenceandrobustsuperhydrophobicityderivedfromelectrodepositedpolypyrene?lms?

LianyiXu,aFaqinTong,aXueminLu,aKaiLubandQinghuaLu*a

A?uorescentandrobustsuperhydrophobiccoatingbasedona?uorinatedpolypyrene/silicahybrid(FPSH)?lmwasreported.Thishybrid?lmiscomposedofanunderlyingpolypyrene?lmandoverlyingsilicalayers.Thepolypyrene?lmiselectrodepositedonanindiumtinoxideglasselectrodebycyclicvoltammetrytoprovideapetal-likehierarchicalroughstructureandstrong?uorescencewithone-stepelectrochemicalpolymerization.Notably,the?uorescenceemissionofthispolypyrene?lmderivesfromtheexcimerforms,reportedhereforthe?rsttime.Thesilicalayersarefabricatedbyatwo-stepchemicalvapordepositiontoobtainasupportingsilicabackboneandalow-energysurface.SeveralcriticaltestswereperformedontheFPSH?lms,con?rmingthatthe?lmisnotonlyathermallystable,anti-acid/alkali,andanti-impactself-cleaningsurface,butalsopresentsastronggreen?uorescenceemission.

Received20thNovember2014Accepted13thJanuary2015DOI:10.1039/c4tc02653ebiningmaterialswithappropriateroughnessandlow-surface-energyinaCassiestate,inwhichthecavitiesoftheroughstructurecannotbeinltratedbywater.3,4Thistypeofcoatinghasawiderangeofpotentialapplicationsinmanytechnologicalandscienticelds,suchasself-cleaningcoatings,5anti-bio-foulingcoatings,6microuidics,7oil–waterseparation,8andbio-tech-nology.9Asaresult,themulti-functionalizationofsuper-hydrophobiccoatingshasrecentlyreceivedspecialattention,leadingtoanintensivedevelopmentofenvironmentallyresponsiveself-cleaningsurfaces,10,11transparentsuper-hydrophobiccoatings,12–14andothermaterials.Amongthevariousmulti-functionalcoatings,luminescentself-cleaning

SchoolofChemistryandChemicalEngineering,StateKeyLaboratoryofMetalMatrixComposite,ShanghaiJiaoTongUniversity,800DongchuanRoad,Shanghai,200240,People'sRepublicofChina.E-mail:qhlu@sjtu.edu.cn

SouthwestWeiyuMiddleSchoolVIA,671YishanRoad,Shanghai,200030,People'sRepublicofChina

?Electronicsupplementaryinformation(ESI)available:Polymerizationdegree,cross-sectionalSEMimageofthelm,silicalayerthickness,microcrystallineoligopyrene,absoluteuorescencequantumyield,andhydraulicpressureresistance.SeeDOI:10.1039/c4tc02653e

coatingshavegeneratedparticularinterest,sinceCharetal.rstreportedthepreparationofauorescentsuper-hydrophobicsurfacebylayerbylayer(L-b-L)depositionusingchargedblockcopolymermicelles(BCMs)withhydrophobicQDsoruorescentdyeswithintheircores.15,16Chenetal.developedaQD-baseduorescentsuperhydrophobicsurfaceviaafacileinterfacialself-assemblytechnique.16bThesecoat-ingsmaybeusefulinmanyphotoelectric,sensing,andopticalimagingdevices,aswellasself-cleaningmaterialsinair.

However,afewstudiesrevealedthatthepreparationofsuchuorescentsuperhydrophobicsurfacesisusuallylimitedtoonlyafewuorescentmaterials(suchasQDsoruorescentdyes)andtechnologies(forexampleself-assembly),16potentiallyrestrictingtheirfurtherdevelopment.Newtechnologiesandmaterialsarehighlyrequiredforthesimpledesignandquickfabricationofsucharobustuorescentsuperhydrophobiccoating.Amongthevariousluminescentmaterials,uorescentp-conjugatedpolymersareparticularlyinterestingbecauseoftheirtunableandstableuorescenceandmachinability.15,17,18Polypyrene,asarepresentativeofp-conjugatedpolymers,isanimportantphotoluminescencematerialwithahighuores-cencequantumyield.18–25Mostinterestingly,polypyrenelmscanbeeasilypreparedonelectrodesbyusingone-stepelectro-chemicaldeposition.18,24Inourpreviouswork,18wefoundthattheelectrodepositedpolypyrenelmusuallyformedanano/micro-metrichierarchicalroughstructure,whichisadvanta-geousforthefabricationofasuperhydrophobiccoating.26Thus,thepolypyrenelmmaybeapromisingcandidateforthefacilefabricationofuorescentsuperhydrophobiccoatings.

2086|J.Mater.Chem.C,2015,3,2086–2092Thisjournalis?TheRoyalSocietyofChemistry2015

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(a)Successivecyclicvoltammogramsoftheelectro-polymerizationofapolypyrene?lmontheITOelectrodeina0.03Mpyrene/ACNsolutioncontaining0.2MLiClO4asasupportingelec-trolyte;jdenotesthecurrentdensity.Insets:schematicreactionoftheelectrochemicalpolymerizationofpolypyrene(top)andphotographoftheresultantpolypyrene?lmontheITOglassexhibitingayellowFig.1

TransformIonCyclotronResonanceMassSpectrometer(FT-ICRMS)(SolariXXR7.0T,America).ThewideangleX-raydi?raction(XRD)patternwasobtainedusingaD8ADVANCEX-rayPolycrystallineDi?ractometer(Bruker,Germany).Thetransmissionelectronmicroscopyimagesandthemicroscopicelectrondi?raction(ED)patternswereobtainedbyusingaJEM-2010HTAnalyticalTransmissionElectronMicroscope(JEOL,Japan).Staticwatercontactanglemeasurementswereper-formedusingthesessiledropmethodonaContactAngleSystemOCA20(DataPhysicsInstrumentsGmbH,Germany)inair.Thecontactanglesreportedherewerethemeanvaluesmeasuredwitha4mLwaterdropletatthreedi?erentpositionsoneachsample.Waterslidingangles(SA)weredeterminedbycolor(bottom).(b)Preparationprocedureof?uorescentrobustsuper-hydrophobiccoatingsbyusinganelectrodepositedroughpolypyrene?lmasaphotoluminescentmaterial.Inthiswork,weproposeanewapproachforthepreparationofuorescentrobustsuperhydrophobiccoatingsbasedonauorinatedpolypyrene/silicahybrid(FPSH)lm(Fig.1).Thishybridlmiscomposedofanunderlyingpolypyrenelmandoverlyingsilicalayers.Theformeriselectrodepositedonanindiumtinoxide(ITO)glasselectrodebycyclicvoltammetry(CV),providingsimultaneouslyapetal-likehierarchicalroughstructureandstronguorescenceviaone-stepelectrochemicalpolymerization(Fig.1a).Thesilicalayersarefabricatedbytwo-stepchemicalvapordeposition(CVD)ontheunderlyingpoly-pyrenelm.Firstly,tetraethoxysilane(TEOS)isdepositedtoimprovethemechanicalresistanceofthepolypyrenelm;secondly,a1H,1H,2H,2H-peruorooctyltriethoxysilane(POTS)lmprovidesthelow-energysurface.Aerthedeposition,theFPSHlmpresentsnotonlyathermallystablesuper-hydrophobicsurfacewithacid/alkaliandwater-dropletimpactresistance,butalsoexhibitsstronggreenuorescenceemission(Fig.1b).Inaddition,wealsoreportedaninterestingchangeofuorescencepropertiesfromthepolypyreneemissioninsolu-tiontotheexcimeremissioninsolidpolypyrenelms.Notably,thegreenuorescenceofthispolypyrenelmderivesfromtheexcimerforms,demonstratedhereforthersttime.

Experimental

Materials

Commercialacetonitrile(ACN)ofhigh-performanceliquidchromatographygradewasprovidedbyShanghaiLingfengChemicalReagentCompanyandwasusedwithoutfurtherpurication.Pyrene(Adamas,98%),tetraethoxysilane(TEOS)(Aladdin,98%),ammoniasolution(Aladdin,25–28%),1H,1H,2H,2H-peruorooctyltriethoxysilane(POTS)(AlfaAesar,97%),andanhydrouslithiumperchlorate(LiClO4)(J&K,99%)wereuseddirectlywithoutfurtherpurication.Characterization

Fieldemissionscanningelectronmicroscopy(FE-SEM)wasperformedbyusingaNovaNanoSEMinstrument(FEI,Amer-ica).ThepolymerizationdegreewasdeterminedbyaFourier

Thisjournalis?TheRoyalSocietyofChemistry2015slowlytiltingthesamplestageuntila4mLwaterdropstartedmoving.Theadhesionforcebetweenthedropletandthesamplewasassessedbyusingahigh-sensitivitymicro-electro-mechanicalbalancesystem(DataPhysicsDCAT11,Germany).Thesamplesurfacewasdrawnnearandretractedfroma4mLwaterdropletsuspendedonahydrophobicmetalringat0.05mmsà1underambientconditions(relativehumidityof$40%).ChemicalcompositionsofthesurfacesweredeterminedbyXPSonaKratosAxisUltraDLDspectrometer(KratosAnalytical-AShimadzu,Japan)withamonochromaticAlKaradiationsource(1486.6eV)andatakeo?angleof90??.FluorescencespectraweredetectedbyusinganF-4500uorescencespectrophotometer(Hitachi).UV-visspectraofthelmsontheITOsubstrateweremeasuredonaPerkin-ElmerLambda20UV-visspectrometer.Thephotographsandthemoviesweretakenwithacamera.TheabsoluteuorescencequantumyieldwasmeasuredbyusingaQuantaMaster40withanintegratingsphere(PhotonTech-nologyInternationalInc.).TheinsituuorescenceintensityundervarioustemperatureswasestimatedbyusingaQM/TM/IMSteady-State&Time-ResolvedFluorescenceSpectrouo-rometer(PhotonTechnologyInternationalInc.).Theimpactofthewaterdropletonthecoatingwascapturedusingahigh-speedcamera(MotionStudioCamerasSDK,IDT,Inc.).TheuorescenceimagesofaFPSHlmwerecapturedwithaninverteduorescencemicroscope(IX71,Olympus)equippedwithaCCDcamera.Electrochemicalexperiments