拉曼光谱分析法-课件

拉曼光谱分析法拉曼光谱分析法1RemoteRamanAnalysis

onPlanetaryMissionsToallowRamanspectroscopyatrangeof10'sofmeters.ThisNASA-fundedprojectisaimedatMarslandersorlandersonotherplanets,butalsohasterrestrialuses.RemoteRamanAnalysis

onPlan2激光拉曼光谱基本原理Rayleigh散射：弹性碰撞；无能量交换，仅改变方向；Raman散射：非弹性碰撞；方向改变且有能量交换；Rayleigh散射Raman散射E0基态，E1振动激发态；E0+h0，

E1+h0激发虚态；获得能量后，跃迁到激发虚态.（1928年印度物理学家RamanCV发现；1960年快速发展）

h

E0E1V=1V=0h0h0h0h0+

E1+h0E0+h0h(0-

)激发虚态激光拉曼光谱基本原理Rayleigh散射：Rayleigh散3基本原理1.Raman散射Raman散射的两种跃迁能量差：

E=h(0-

)产生stokes线；强；基态分子多；

E=h(0+

)产生反stokes线；弱；Raman位移：Raman散射光与入射光频率差；ANTI-STOKES0-

RayleighSTOKES0+

0h(0+

)E0E1V=1V=0E1+h0E2+h0

h

h0h(0-

)基本原理1.Raman散射ANTI-STOKES0-4Rayleigh/RamanTransitionsIRAbsorptionsRayleigh/RamanTransitionsIR5Rayleigh/RamanTransitionsandSpectraRayleigh/RamanTransitionsa6Rayleigh/RamanTransitionsandSpectraRayleigh/RamanTransitionsa7TheSpectrumAcompleteRamanspectrumconsistsof:•aRayleighscatteredpeak(highintensity,samewavelengthasexcitation)•aseriesofStokes-shiftedpeaks(lowintensity,longerwavelength)•aseriesofanti-Stokesshiftedpeaks(stilllowerintensity,shorterwavelength)•spectrumindependentofexcitationwavelength(488,632.8,or1064nm)SpectrumofCCl4,usinganAr+laserat488nm.TheSpectrumAcompleteRamans8RamanSpectroscopyAnotherspectroscopictechniquewhichprobestherovibrationalstructureofmolecules.C.V.Ramandiscoveredin1928;receivedNobelPrizein1931.Canprobegases,liquids,andsolids.Mustusealasersourceforexcitation.Resurgenceinrecentyearsduetothedevelopmentofnewdetectorswithimprovedsensitivity.ShiftbackawayfromFT-RamantodispersiveRamanwithmultichanneldetectorsystems.RamanSpectroscopyAnotherspec9InfraredandRamanSpectraofBenzeneIRRamanInfraredandRamanSpectraof10拉曼光谱与红外光谱分析方法比较拉曼光谱与红外光谱分析方法比较11SomeRamanAdvantagesHerearesomereasonswhysomeonewouldprefertouseRamanSpectroscopy.•Non-destructivetosamples(minimalsampleprep)•Highertemperaturestudiespossible(don’tcareaboutIRradiation)•Easilyexaminelowwavenumberregion:100cm-1readilyachieved.•Bettermicroscopy;usingvisiblelightsocanfocusmoretightly.•Easysampleprep:waterisanexcellentsolventforRaman.Canprobesamplethroughtransparentcontainers(glassorplasticbag).SomeRamanAdvantagesHereare12WatchforFluorescenceSpectrumofanthracene.A:usingAr+laserat514.5nm.B:usingNd:YAGlaserat1064nm.Wanttouseshortwavelengthbecausescatteringdependson4thpoweroffrequency.…BUT…Wanttouselongwavelengthtominimizechanceofinducingfluorescence.WatchforFluorescenceSpectrum13红外活性和拉曼活性振动①红外活性振动

ⅰ永久偶极矩；极性基团；ⅱ瞬间偶极矩；非对称分子；红外活性振动—伴有偶极矩变化的振动可以产生红外吸收谱带.②拉曼活性振动

诱导偶极矩=E非极性基团，对称分子；拉曼活性振动—伴随有极化率变化的振动。对称分子：对称振动→拉曼活性。不对称振动→红外活性

Eeer红外活性和拉曼活性振动①红外活性振动红外活性振动—伴有偶极矩14SelectionRuleforRamanScatteringMustbechangeinpolarizabilityNon-PolargroupssuchasC-S,S-S,C=C,CC(triplebond),N=Nandheavyatoms(I,Br,Hg)strongscatterersSymmetricstretchingvibrationsaremuchstrongerscatterersthanasymmetricstretchingvibrationsSelectionRuleforRamanScatt15PolarizationEffectsPolarizationEffects16对称中心分子CO2，CS2等，选律不相容。无对称中心分子（例如SO2等），三种振动既是红外活性振动，又是拉曼活性振动。选律1234拉曼活性红外活性红外活性振动自由度：3N-4=4拉曼光谱—源于极化率变化红外光谱—源于偶极矩变化对称中心分子CO2，CS2等，选律不相容。选17PolarizationofCCl4

PolarizationofCCl418PolarizationofCHCl3

PolarizationofCHCl319Raman位移

对不同物质：不同；对同一物质：与入射光频率无关；表征分子振-转能级的特征物理量；定性与结构分析的依据；Raman散射的产生：光电场E中，分子产生诱导偶极距=E

分子极化率；Raman位移对不同物质：不同；20由拉曼光谱可以获得有机化合物的各种结构信息：2）红外光谱中，由CN，C=S，S-H伸缩振动产生的谱带一般较弱或强度可变，而在拉曼光谱中则是强谱带。3）环状化合物的对称呼吸振动常常是最强的拉曼谱带。1）同种分子的非极性键S-S，C=C，N=N，CC产生强拉曼谱带，随单键双键三键谱带强度增加。拉曼光谱与有机结构由拉曼光谱可以获得有机化合物的各种结构信息：2）红外光谱中，214）在拉曼光谱中，X=Y=Z，C=N=C，O=C=O-这类键的对称伸缩振动是强谱带，反这类键的对称伸缩振动是弱谱带。红外光谱与此相反。5）C-C伸缩振动在拉曼光谱中是强谱带。6）醇和烷烃的拉曼光谱是相似的：I.C-O键与C-C键的力常数或键的强度没有很大差别。II.羟基和甲基的质量仅相差2单位。III.与C-H和N-H谱带比较，O-H拉曼谱带较弱。4）在拉曼光谱中，X=Y=Z，C=N=C，O=C=O-这类键22红外与拉曼谱图对比红外光谱：基团；拉曼光谱：分子骨架测定；红外与拉曼谱图对比红外光谱：基团；23红外与拉曼谱图对比红外与拉曼谱图对比24RamanandInfraredSpectraofH-C≡C-HAsymmetricC-HStretchSymmetricC-HStretchC≡CStretchRamanandInfraredSpectraof25Vibrationalmodesofmethane(CCl4)Infraredinactive,RamanactivevibrationsInfraredactive,Ramaninactivevibrations314cm-1776cm-1463cm-1219cm-1Vibrationalmodesofmethane(26InfraredandRamanSpectrumofCCl4776cm-1314cm-1463cm-1219cm-1InfraredspectrumRamanspectrumInfraredandRamanSpectrumof272941，2927cm-1

ASCH22854cm-1

SCH21029cm-1

（C-C）803cm-1环呼吸

1444，1267cm-1

CH22941，2927cm-1ASCH22854cm-1283060cm-1r-H)1600,1587cm-1c=c)苯环1000cm-1环呼吸787cm-1环变形1039,1022cm-1单取代3060cm-1r-H)1600,1587cm-129RamanSpectroscopyRelativelysimpleandnon-destructivestructureanalysistechniqueofcarbonmaterialsPowerfultoolforthestructuralcharacterizationofdiamondoramorphouscarbonmaterials.DLCDiamondRamanSpectroscopyRelativelys30RemoteRamanAnalysis

onPlanetaryMissionsToallowRamanspectroscopyatrangeof10'sofmeters.ThisNASA-fundedprojectisaimedatMarslandersorlandersonotherplanets,butalsohasterrestrialuses.RemoteRamanAnalysis

onPlan31NSOMRamanImagingSpectrumofpotassiumtitanylphosphate.FromHansHallenatNCSU.Squaresare5x5µmsquareofthismaterialdopedwithRb.Anear-fieldscanningmicroscopewasusedandtheRamansignalwasusedtokeythesubstrateresponse.NSOMRamanImagingSpectrumof32ChemicalMappingFocuslasertosmallspot.TunespectrometertoparticularRamantransitionpeak.Rasterscanthesampleunderthelaserbeam,recordintensitychanges.Resultantmapcorrelateswithsubstance.Acquireanentirespectrumateverypoint,thenchoosethefeaturewithwhichtokeytheimage.MotorizedstagefromRenishawforchemicalmapping.Thisisadrugtablet.Theyellowcorrespondstotheactiveingredient.Particlesareinthe10’sofµmrange.ChemicalMappingFocuslaserto33ChemicalImagingNowdefocusthelaser(notasmallspotbutrather“baths”thesampleinlaserradiation).Passtheemittedradiationthroughanarrowbandpassfilter,adjustedtoaparticularwavelength,chosentobeacertainRamanband.FocusthislightontheCCDcamera.BrightregionscorrespondtolocationsofsubstancegivingrisetoRamansignal.Mixtureofcocaineandsugar.Brightspotsarecocaine.ChemicalImagingNowdefocusth34Applications-ArtRestorationThis12centuryfrescoonachurchwallinItalyneededtoberestored.Whatpaintstouse?Ramananalysisclearlyidentifiedthepaintsandpigmentsthatwereoriginallypresent,permittingacorrectchoiceofcleaningmaterialsandsubsequentrepaintingtorestoreitsoriginalcondition.Applications-ArtRestoration35Applications-PaintChipsForensicanalysisofpaintchipsinvehicleaccidents.Oftenmultiplelayers.CananalyzewithIRbystrippingsuccessivelayers.ImageedgewithmicroRaman.Layers1and3turnedouttoberutilephaseTiO2-awhitepaint.Layer2wasaGoethite,aredpigmentandcorrosioninhibitor.Layer4wasmolybdateorange,acommonredpaintinthe70’sinNorthAmericaandstillusedintheU.K.today.Layer5wasasilicatebasedpaint.DataarisingfromacaseinvestigatedbyLAPD.Applications-PaintChipsFore36Applications-GemForgeryIn1999anewprocesswasdeveloped–calledGEPOL–wherebybrowntypeIIadiamondscouldbetreatedtobecomeindistinguishablefromnaturallycleardiamonds.Ramanpresentedwaytodistinguishthem.NaturallycleardiamondOriginallybrowndiamondApplications-GemForgeryIn137Applications-BulletProofGlassIdentifypoly(carbonate)frompoly(methylmethacrylate).Bothusedforshatter-proofglassApplications-BulletProofGl38Applications-SunscreenFormulationsHerearethespectraof5commonsunscreeningredients.Ramanisabletodeterminefromaspectrumonthearmthenatureofthesunscreenbeingused.A:ODPABA(octylN,N-dimethyl-p-aminobenzoicacid)B:OMC(octylp-methoxycinnamate)C:BZ3(oxybenzone)D:OCS(octylsalicylate)E:DBM(dibenzoylmethane)G.R.Luppnowetal.,J.Raman.Spec.34,743(2003).Applications-SunscreenFormu39激光Raman光谱仪

laserRamanspectroscopy激光光源：He-Ne激光器，波长632.8nm；

Ar激光器，波长514.5nm，488.0nm；散射强度1/4单色器：

光栅，多单色器；检测器：光电倍增管，光子计数器；激光Raman光谱仪

laserRamanspectr40傅立叶变换-拉曼光谱仪FT-Raman

spectroscopy光源：Nd-YAG钇铝石榴石激光器（1.064m）；检测器：高灵敏度的铟镓砷探头；特点：（1）避免了荧光干扰；（2）精度高；（3）消除了瑞利谱线；（4）测量速度快。傅立叶变换-拉曼光谱仪FT-Ramanspectrosco41SourcesRamanintensityisweakandtheexcitationsourcemustbestrongtogeneratesufficientsignal.Sourcemustbemonochromaticsothatspectrumissufficientlyuncomplicated.Intenselampscanwork,butwhenmonochromatized,haveverylittlepower.Scatteringefficiencyincreasesasn4:thebluerthelight,themorethescattering.Thebluerthelight,thegreaterthechanceofproducingfluorescence.Lasersareusedalmostexclusively.Ar+Ion:488.0and514.5nmKr+Ion:530.9and647.1nmHe:Ne:632.8nmDiodeLasers:782and830nmNd:YAG:1064(532whendoubled)nmIjustchecked.Hereisa500mWArionlaserforsaleoneBayfor$1000.SourcesRamanintensityisweak42Sources-1Experimentusedtorequireconsiderableexcitationpower Ionlasers,40Wcw He:Ne,10Wcw YAG,1J/10nspulse(100MWaveragepulse)Butdetectorshaveimprovedsomuch,thesourcepowerrequirementshavebeendecreased. Diodelaser,25mW otherlaserscanbemadecorrespondinglysmaller.Sources-1Experimentusedtore43DetectorsScatteredlightislowintensity,sohighgainPMT’shavebeenusedinthepast.ThiswasusedforscannedandFT-Ramaninstrumentationformanyyears.NowcooledCCDarraysareused;experimentisnowmultichannel.CooledNIRdetector,1024x256pixelarray,26µmsquarepixels.FromJobinYvon.DetectorsScatteredlightislo44拉曼光谱分析法拉曼光谱分析法45RemoteRamanAnalysis

onPlanetaryMissionsToallowRamanspectroscopyatrangeof10'sofmeters.ThisNASA-fundedprojectisaimedatMarslandersorlandersonotherplanets,butalsohasterrestrialuses.RemoteRamanAnalysis

onPlan46激光拉曼光谱基本原理Rayleigh散射：弹性碰撞；无能量交换，仅改变方向；Raman散射：非弹性碰撞；方向改变且有能量交换；Rayleigh散射Raman散射E0基态，E1振动激发态；E0+h0，

E1+h0激发虚态；获得能量后，跃迁到激发虚态.（1928年印度物理学家RamanCV发现；1960年快速发展）

h

E0E1V=1V=0h0h0h0h0+

E1+h0E0+h0h(0-

)激发虚态激光拉曼光谱基本原理Rayleigh散射：Rayleigh散47基本原理1.Raman散射Raman散射的两种跃迁能量差：

E=h(0-

)产生stokes线；强；基态分子多；

E=h(0+

)产生反stokes线；弱；Raman位移：Raman散射光与入射光频率差；ANTI-STOKES0-

RayleighSTOKES0+

0h(0+

)E0E1V=1V=0E1+h0E2+h0

h

h0h(0-

)基本原理1.Raman散射ANTI-STOKES0-48Rayleigh/RamanTransitionsIRAbsorptionsRayleigh/RamanTransitionsIR49Rayleigh/RamanTransitionsandSpectraRayleigh/RamanTransitionsa50Rayleigh/RamanTransitionsandSpectraRayleigh/RamanTransitionsa51TheSpectrumAcompleteRamanspectrumconsistsof:•aRayleighscatteredpeak(highintensity,samewavelengthasexcitation)•aseriesofStokes-shiftedpeaks(lowintensity,longerwavelength)•aseriesofanti-Stokesshiftedpeaks(stilllowerintensity,shorterwavelength)•spectrumindependentofexcitationwavelength(488,632.8,or1064nm)SpectrumofCCl4,usinganAr+laserat488nm.TheSpectrumAcompleteRamans52RamanSpectroscopyAnotherspectroscopictechniquewhichprobestherovibrationalstructureofmolecules.C.V.Ramandiscoveredin1928;receivedNobelPrizein1931.Canprobegases,liquids,andsolids.Mustusealasersourceforexcitation.Resurgenceinrecentyearsduetothedevelopmentofnewdetectorswithimprovedsensitivity.ShiftbackawayfromFT-RamantodispersiveRamanwithmultichanneldetectorsystems.RamanSpectroscopyAnotherspec53InfraredandRamanSpectraofBenzeneIRRamanInfraredandRamanSpectraof54拉曼光谱与红外光谱分析方法比较拉曼光谱与红外光谱分析方法比较55SomeRamanAdvantagesHerearesomereasonswhysomeonewouldprefertouseRamanSpectroscopy.•Non-destructivetosamples(minimalsampleprep)•Highertemperaturestudiespossible(don’tcareaboutIRradiation)•Easilyexaminelowwavenumberregion:100cm-1readilyachieved.•Bettermicroscopy;usingvisiblelightsocanfocusmoretightly.•Easysampleprep:waterisanexcellentsolventforRaman.Canprobesamplethroughtransparentcontainers(glassorplasticbag).SomeRamanAdvantagesHereare56WatchforFluorescenceSpectrumofanthracene.A:usingAr+laserat514.5nm.B:usingNd:YAGlaserat1064nm.Wanttouseshortwavelengthbecausescatteringdependson4thpoweroffrequency.…BUT…Wanttouselongwavelengthtominimizechanceofinducingfluorescence.WatchforFluorescenceSpectrum57红外活性和拉曼活性振动①红外活性振动

ⅰ永久偶极矩；极性基团；ⅱ瞬间偶极矩；非对称分子；红外活性振动—伴有偶极矩变化的振动可以产生红外吸收谱带.②拉曼活性振动

诱导偶极矩=E非极性基团，对称分子；拉曼活性振动—伴随有极化率变化的振动。对称分子：对称振动→拉曼活性。不对称振动→红外活性

Eeer红外活性和拉曼活性振动①红外活性振动红外活性振动—伴有偶极矩58SelectionRuleforRamanScatteringMustbechangeinpolarizabilityNon-PolargroupssuchasC-S,S-S,C=C,CC(triplebond),N=Nandheavyatoms(I,Br,Hg)strongscatterersSymmetricstretchingvibrationsaremuchstrongerscatterersthanasymmetricstretchingvibrationsSelectionRuleforRamanScatt59PolarizationEffectsPolarizationEffects60对称中心分子CO2，CS2等，选律不相容。无对称中心分子（例如SO2等），三种振动既是红外活性振动，又是拉曼活性振动。选律1234拉曼活性红外活性红外活性振动自由度：3N-4=4拉曼光谱—源于极化率变化红外光谱—源于偶极矩变化对称中心分子CO2，CS2等，选律不相容。选61PolarizationofCCl4

PolarizationofCCl462PolarizationofCHCl3

PolarizationofCHCl363Raman位移

对不同物质：不同；对同一物质：与入射光频率无关；表征分子振-转能级的特征物理量；定性与结构分析的依据；Raman散射的产生：光电场E中，分子产生诱导偶极距=E

分子极化率；Raman位移对不同物质：不同；64由拉曼光谱可以获得有机化合物的各种结构信息：2）红外光谱中，由CN，C=S，S-H伸缩振动产生的谱带一般较弱或强度可变，而在拉曼光谱中则是强谱带。3）环状化合物的对称呼吸振动常常是最强的拉曼谱带。1）同种分子的非极性键S-S，C=C，N=N，CC产生强拉曼谱带，随单键双键三键谱带强度增加。拉曼光谱与有机结构由拉曼光谱可以获得有机化合物的各种结构信息：2）红外光谱中，654）在拉曼光谱中，X=Y=Z，C=N=C，O=C=O-这类键的对称伸缩振动是强谱带，反这类键的对称伸缩振动是弱谱带。红外光谱与此相反。5）C-C伸缩振动在拉曼光谱中是强谱带。6）醇和烷烃的拉曼光谱是相似的：I.C-O键与C-C键的力常数或键的强度没有很大差别。II.羟基和甲基的质量仅相差2单位。III.与C-H和N-H谱带比较，O-H拉曼谱带较弱。4）在拉曼光谱中，X=Y=Z，C=N=C，O=C=O-这类键66红外与拉曼谱图对比红外光谱：基团；拉曼光谱：分子骨架测定；红外与拉曼谱图对比红外光谱：基团；67红外与拉曼谱图对比红外与拉曼谱图对比68RamanandInfraredSpectraofH-C≡C-HAsymmetricC-HStretchSymmetricC-HStretchC≡CStretchRamanandInfraredSpectraof69Vibrationalmodesofmethane(CCl4)Infraredinactive,RamanactivevibrationsInfraredactive,Ramaninactivevibrations314cm-1776cm-1463cm-1219cm-1Vibrationalmodesofmethane(70InfraredandRamanSpectrumofCCl4776cm-1314cm-1463cm-1219cm-1InfraredspectrumRamanspectrumInfraredandRamanSpectrumof712941，2927cm-1

ASCH22854cm-1

SCH21029cm-1

（C-C）803cm-1环呼吸

1444，1267cm-1

CH22941，2927cm-1ASCH22854cm-1723060cm-1r-H)1600,1587cm-1c=c)苯环1000cm-1环呼吸787cm-1环变形1039,1022cm-1单取代3060cm-1r-H)1600,1587cm-173RamanSpectroscopyRelativelysimpleandnon-destructivestructureanalysistechniqueofcarbonmaterialsPowerfultoolforthestructuralcharacterizationofdiamondoramorphouscarbonmaterials.DLCDiamondRamanSpectroscopyRelativelys74RemoteRamanAnalysis

onPlanetaryMissionsToallowRamanspectroscopyatrangeof10'sofmeters.ThisNASA-fundedprojectisaimedatMarslandersorlandersonotherplanets,butalsohasterrestrialuses.RemoteRamanAnalysis

onPlan75NSOMRamanImagingSpectrumofpotassiumtitanylphosphate.FromHansHallenatNCSU.Squaresare5x5µmsquareofthismaterialdopedwithRb.Anear-fieldscanningmicroscopewasusedandtheRamansignalwasusedtokeythesubstrateresponse.NSOMRamanImagingSpectrumof76ChemicalMappingFocuslasertosmallspot.TunespectrometertoparticularRamantransitionpeak.Rasterscanthesampleunderthelaserbeam,recordintensitychanges.Resultantmapcorrelateswithsubstance.Acquireanentirespectrumateverypoint,thenchoosethefeaturewithwhichtokeytheimage.MotorizedstagefromRenishawforchemicalmapping.Thisisadrugtablet.Theyellowcorrespondstotheactiveingredient.Particlesareinthe10’sofµmrange.ChemicalMappingFocuslaserto77ChemicalImagingNowdefocusthelaser(notasmallspotbutrather“baths”thesampleinlaserradiation).Passtheemittedradiationthroughanarrowbandpassfilter,adjustedtoaparticularwavelength,chosentobeacertainRamanband.FocusthislightontheCCDcamera.BrightregionscorrespondtolocationsofsubstancegivingrisetoRamansignal.Mixtureofcocaineandsugar.Brightspotsarecocaine.ChemicalImagingNowdefocusth78Applications-ArtRestorationThis12centuryfrescoonachurchwallinItalyneededtoberestored.Whatpaintstouse?Ramananalysisclearlyidentifiedthepaintsandpigmentsthatwereoriginallypresent,permittingacorrectchoiceofcleaningmaterialsandsubsequentrepaintingtorestoreitsoriginalcondition.Applications-ArtRestoration79Applications-PaintChipsForensicanalysisofpaintchipsinvehicleaccidents.Oftenmultiplelayers.CananalyzewithIRbystrippingsuccessivelayers.ImageedgewithmicroRaman.Layers1and3turnedouttoberutilephaseTiO2-awhitepaint.Layer2wasaGoethite,aredpigmentandcorrosioninhibitor.Layer4wasmolybdateorange,acommonredpaintinthe70’sinNorthAmericaandstillusedintheU.K.today.Layer5wasasilicatebasedpaint.DataarisingfromacaseinvestigatedbyLAPD.Applications-PaintChipsFore80Applications-GemForgeryIn1999anewprocesswasdeveloped–calledGEPOL–wherebybrowntypeIIadiamondscouldbetreatedtobecomeindistinguishablefromnaturallycleardiamonds.Ramanpresentedwaytodistinguishthem.NaturallycleardiamondOriginallybrowndiamondApplications-GemForgeryIn181Applications-BulletProofGlassIdentifypoly(carbonate)frompoly(methylmethacrylate).Bothusedforshatter-proofglassApplications-BulletProofGl82Applications-SunscreenFormulationsHerearethespectraof5commons