现代仪器分析SFG.ppt

ApplicationofSumfrequencygenerationvibrationalspectroscopyincharacteringpolymersurface聚合物表面和界面的表征 和频振动光谱 Reporter TanJiaojun2012 12 10 Contents Page Lackofsurfaceselectivity Background Quasi surface Principle PrincipalandphenomenonofSFG Sumfrequencyspectrumsystem 5mainunits Principle Principle Appearance Functions Mono layerNodamage Interfacespeci c StructureOrientation Crystallize Stress induced Environmentalresponse Blendsbehavior SFGinpolymercharacter Advantage Functions Samplepreparation Attention 1 Spincoating injection 2 Cleansurface sample substrate bypiranhasolution Analysis Analysis 1 Charactercompositionandstructureofsurface IndicatingthatsurfaceisdominatedbyOCH3ratherthanpolyethylene thoughtheamountofadditivesaddedissosmallthattheycannotbedetectedbyIRandRamanspectroscopies 2926 OCH3 JieWang ZoltanPaszti J Am Chem Soc 2002 124 24 pp7016 7023 1 Charactercompositionandstructureofsurface Analysis DISCUSSION Analysis 2 GlasstransitionofthePPsurfaces Fig TheratioofthestrengthsoftheCH2symmetricstretchtotheCH3symmetricstretchforAPPandIPPasafunctionoftemperature Semicrystallinepolymer Amorphouspolymer Analysis 2 GlasstransitionofthePPsurfaces Blends YiLiu MarieC messer J Phys Chem B 2003 107 36 9774 9779 Blends A fMMA 0 03 B fMMA 0 06 C fMMA 0 09 D fMMA 0 11 Analysis 3 StructuresandSegregationofPS PMMABlends FigureWatercontact angleofblendsbefore o andafter annealing FigureSFGofblends Sampleswereannealedinavacuumat150 for20h YiLiu MarieC messer J Phys Chem B 2003 107 36 9774 9779 Analysis 3 StructuresandSegregationofPS PMMABlends Analysis 4 Environmentalresponse Prospect SFGhavebeenusedsuccessfullytoprobeburiedinterfacinvariousfieldsofresearch Buttherearemanyprolemstobesolved 1 IR IR visiblespectroscopy2 doublyresonantSFGspectroscopymolecularchirality3 developmentofhigh powertuneablelasersources Thankyou TJJ 原理 IR visiblesumfrequencygenerationspectroscopyusestwolaserbeamsthatoverlapatasurfaceofamaterialortheinterfacebetweentwomaterials Anoutputbeamisgeneratedatafrequencyofthesumofthetwoinputbeams Thetwoinputbeamshavetobeabletoaccessthesurface andtheoutputbeamneedstobeabletoleavethesurfacetobepickedupbyadetector 2 Oneofthebeamsisavisiblewavelengthlaserheldataconstantfrequencyandtheotherisatunableinfraredlaser BytuningtheIRlaser thesystemcanscanoverresonancesandobtainthevibrationalspectrumoftheinterfacialregion 1 Asanonlinearopticalprocess thepolarizationwhichgeneratestheoutputdependsontheelectricfieldsofthetwoinputbeams Asasecond ordernonlinearprocess SFGisdependentonthe2ndordersusceptibility 2 Thefactthatthe2ndordersusceptibility athirdranktensor becomeszeroincentrosymmetricmedia limitswhatsamplesareaccessibleforSFG Centrosymmetricmediaincludethebulkofgases liquids andmostsolidsundertheassumptionoftheelectric dipoleapproximation whichneglectsthesignalgeneratedbymultipolesandmagneticmoments 2 Ataninterfacebetweentwodifferentmaterialsortwocentrosymmetricmedia theinversionsymmetryisbrokenandanSFGsignalcanbegenerated Thissuggeststhattheresultingspectrarepresentathinlayerofmolecules Asignalisfoundwhenthereisanetpolarorientation 2 3 Sumfrequencygenerationspectroscopy SFG isatechniqueusedtoanalyzesurfacesandinterfaces Thisnonlinearlaserspectroscopymethodwasdevelopedin1987andrapidlyappliedtodeducethecomposition orientationdistributions andsomestructuralinformationofmoleculesatgas solid gas liquidandliquid solidinterfaces InatypicalSFGsetup twolaserbeamsmixatasurfaceandgenerateanoutputbeamwithafrequencyequaltothesumofthetwoinputfrequencies SFGhasadvantagesinitsabilitytobemonolayersurfacesensitive abilitytobeperformedinsitu forexampleaqueoussurfacesa