用一种溶剂相助工艺制备PS@Ag 核壳复合胶体小球和空心银球

@AgCore-shellcomplexcolloidsandhollowAgspheresbyasolvent-assitedrouteJianhuiZhang*,HuaiyongLiu,ZhenlinWang,andNaibenMingNationalLaboratoryofSolidStateMicrostructures,DepartmentofPhysics,NanjingUniversity,Nanjing210093(China)Email:[e-mail]-assistedroutehasbeenexploredtouniformlycoatpolystyrene(PS)colloidswithsilverandpreparethecorrespondinghollowspheres.ThesilvernanocrystalsaresynthesizeddirectlyinthesurfacelayerofthePScolloidsswelledbyacetone,andthesurfacemodificationofthePScoreisunnecessary.Aseedinggrowthtechniqueusingcontinuousdropadditionof10%HCHOsolutionisdevelopedtogrowthesilvernanocrystals.AfterremovingthePScore,thehollowsilverspheresareobtained.Thecoverage,thickness,androughnessoftheshellcanbeeffectivelymodifiedbyvaryingtheamountofacetoneandHCHO,andtheas-preparedcompositespherescancrystallizedirectlyintolong-rangeorderedstructure.Ourcoatingrouteisfacileandversatile,andcanbeextendedtocoatPScolloidswithothermetalandpreparethecorrespondinghollowmetalspheres.Keywords:solvent-assistedroute,coating1IntroductionFabricationofmetal-coatedlatexcore-shellparticlesandthecorrespondinghollow[1],photoniccrystal[2-4],catalysis[5-6],biochemistry[7]ofpotentialusesaschemicalsensors,etc.Avarietyofrouteshavebeenexploredforcoatinglatexparticleswithmetal.Theearliermethodsinvolvetheactivationofthelatexsurfaceby“seeds”ofadifferentmetal,suchaspalladium[8],followedbythedepositionofthedesiredmetal.Otherearlierwet-chemistrymethodsinvolvetheimmersionofthelatexparticlesintoasolutionoftherespectivemetalprecursor,andsubsequentreduction[9].Inthesemethods,eitherrelativelythickmetalcoatingsinthemicrometersizeregimehavebeenobtained[8],oronlyasmallpotionofthelatexparticleshasbeencoveredbyametallayerofirregularthickness,leavingalargenumberofnoncoatedlatexparticles[9].Thermalevaporationtechniquesorsputteringalsobeusedearlytocoatthelatexparticleswithmetal[10-11],merelymetalislandsandpartialcoverageareusuallyachievedbythesemethods.Self-assembley[12]andinsituchemicalreduction[13]havebeenrecentlyexploitedtodepositmetalondielectriccore.Inmostcase,thedegreeofsurfacecoverageislowerthan30%andthemetalliccoatingisnon-uniform,owningtotheinterpatricleCoulombrepulsionand/orthepassivationofmetallicnanoparticlescausedbycappingagents(e.g.citrate)[12].Subsequently,atwo-stepmethodinvolvingtheself-assemblyseedingandsubsequentseedinggrowthhasbeeninvestigated,resultingincompleteandsmoothgoldnanoshellsonlatexbeads[14].Morerecently,thelayer-by-layer(LBL)self-assemblyofpolyelectrolytesandmetalnanoparticlesonthelatexcoresurfacehasbeensuccessfullyexploitedtoprepareuniformandcompletemetalshellwithcontrolledthicknessonlatexsphere[4,15].However,boththeabovetwomethodsarelimitedbythecomplexoperationandadditionalpreparationofmetalnanoparticles.Here,wereportafacileandversatileapproachbasedonsolvent-assistedsurfacelayerseedingandseedinggrowthtechniqueusingcontinuousdropadditionofreductantsolutiontoprepareuniformsilvershellwithcontrolledthicknessonpolystyrene(PS)colloidsandthecorrespondinghollowsilverspheres.Therearethreeadvantagesofourcoatingrouteasfollows:1)thesurfacefunctionalizationormodificationofcoreisavoided;2)silverseedsaresynthesizeddirectlyinthesurfacelayerofcore,notonlytheadditionalpreparationofsilvernanoparticlescanbeavoided,butalsothecombinationofcoreandseedsaswellasthe)thethicknessandroughnessofthesilvershellcanbeeffectivelycontrolledbythegrowthtechniqueusingcontinuousdropadditionofreductantsolution,andthecompositecolloidscancrystallizeintolong-rangeorderedstructure.2ExperimentalsectionScheme1.FabricationprocedureofcoatingPScolloidswithsilverandthecorrespondinghollowsilverspheresThefabricationprocedureofcoatingPScolloidswithsilverandthecorrespondinghollowsilverspheresisshowninsheme.1.ThePScolloidssynthesizedbyemulsionpolymerizingmethod[16]wereimmersedinthemixedsolventofethanolandacetone(25vol.%)saturatedwithAgNO3undermagneticstirringfor30minutesatroomtemperature.Duringthetreatmentprocess,thesurfacelayerofthePScolloidswasswelledbyacetoneandpermeatedbythesilverions.Theswollencolloidswerewashedwithethanolbycentrifugationandultrasonicdispersion,anddispersedinethanol.Subsequently,2wt.%NaH2PO2wasaddedtoreducethesilverionsintheswollenlayerforonehour.ThecolloidsafterseedingwerewashedwithethanolanddispersedintheaqueousethanolcontainingAgNO3(0.2M),C6H5O7Na3·2H2O(0.1M)andmodest(10%)dilutedwithethanolwasaddeddropwisetogrowthesilvernanoparticles,andincreasethecompactandthicknessofthesilvershell.Thedropvolumeandintervalareabout0.02mland10seconds,respectively.ThethicknessanduniformityofthesilvershellcanbeeffectivelymodifiedbyvaryingtheamountofHCHO.Finally,thesilver-PScompositeswereimmersedintoluenefor12hourstoremovethePScoreandpreparethehollowsilverspheres.Theabovecomposite