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1、3168J.Phys.Chem.C2009,113,3168–3175ASelf-TemplatedRoutetoHollowSilicaMicrospheresTieruiZhang,†QiaoZhang,†JianpingGe,†JamesGoebl,†MinweiSun,‡YushanYan,‡Yi-shengLiu,§,
2、ChinglinChang,
3、JinghuaGuo,§andYadongYin†,*DepartmentofChemistryandDepartmentofChemicalandEnVironmentalEngineering,UniVer
4、sityofCalifornia,RiVerside,California92521,DepartmentofPhysics,TamkangUniVersity,Tamsui251,Taiwan,andAdVancedLightSource,LawrenceBerkeleyNationalLaboratory,Berkeley,California94720ReceiVed:NoVember25,2008;ReVisedManuscriptReceiVed:December29,2008Asimple,mild,andeffectiveself-templateda
5、pproachhasbeendevelopedtodirectlyconvertsolidSiO2microspheresintohollowstructures.ThereactioninvolvesinitialpartialdissolutionofsilicacoresinaNaBH4solutionandsubsequentshellformationduetotheredepositionofthesilicatespeciesbackontothecolloidsurfaces.TheincreasingconcentrationofNaBO2asth
6、eresultoftheslowdecompositionofNaBH4inwaterisfoundtoberesponsiblefortheregrowthofthesilicashell.Thismethodallowstheproductionofhollowsilicasphereswithsizesrangingfrom∼70nanometerstoseveralmicrometers,largelydeterminedbythesizeofthestartingsilicacolloids.Thesolid-to-hollowtransformation
7、mechanismisinvestigatedindetailbytransmissionelectronmicroscopy(TEM),scanningelectronmicroscopy(SEM),FourierTransformInfrared(FTIR)spectrometry,X-rayabsorptionspectroscopy(XAS),N2adsorption-desorption,andX-raydiffraction(XRD).Wealsostudythereactionconditionsthatallowcontroloverthewallt
8、hickness,surfacemorphology,andshellporosity.1.IntroductioninanaqueoussolutionofNaBH4,undergoaspontaneousmorphologychangefromsolidtohollowspheres.31TheManysyntheticprocedureshavebeendevelopedinrecentformationofhollowsilicaspheresisbasedonthespontaneousyearsforthepreparationofhollowmicro
9、-andnanostructures,dissolutionandregrowthofsilicaatthenanometerscale.Suchlargelybecauseoftheirwideapplicationsindrugdelivery,aprocessisdifferentfromthewell-demonstratedsacrificialphotoniccrystals,sensing,energy-storagemedia,andnano-1-8templatingproceduresinmanyregards:(a)Thismethodisv