对硝基苯甲酸在水溶液和银胶中的紫外拉曼光谱(英文)

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【关键词】紫外 对硝基苯甲酸 PNBA 拉曼光谱 

【出版日期】2005-03-30

【摘要】本文给出了紫外激发下的PNBA水溶液的拉曼光谱图,并对图中峰位做了相应的归属认证。本文还报道了PNBA在银胶中的表面非增强拉曼散射现象,并分析了导致该现象可能的原因

【刊名】光散射学报

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ThisreportprovidestheUVRamanspectraofPNBAinaqueoussolutionandsilvercolloid Wefindthatthere snotanyenhancementofPNBAinsilvercolloidexcitedby 32 5nm Andpossiblereasonsarediscussed PNBAisusuallydissolvedtoorganicsolventratherthantoaqueoussolventtoobtaintheRamanspectrumbecauseofthelowsolubilityinaqueoussolution TheearlyspectraofPNBAinsilvercolloidconsistoftwodifferenttypes Onetypeofthespectraisfeaturesofthestrongbandslocatedat 1 60 0cm- 1 ,1 35 5cm- 1 ,1 1 1 5cm- 1 ,875cm- 1 ,resembletothenormalRamanofp -nitrobenzoatesaltinethanoloraqueoussolution[1 ] Theotherischaracteristicoftwoweakbandsat 1 35 5cm- 1 and 1 1 1 5cm- 1 ,astrongbandat 1 460cm- 1 andastrongdoubletnear 1 1 5 0cm- 1 Butsomeauthorshavearguedthatthosebandsofthelattertypeareduetoazodibenzoate[2 ] TheUVRamanspectrumwehaverecordedisinagreementwiththeformer ,showninFig 1a ,andthetwoprominentbandsoccurat 1 35 3cm- 1 and 1 60 4cm- 1 ,respectivelyduetoNO2 andringstretch ingvibration Twomediumintensitybandsappearat 867cm - 1and 1 1 1 1cm- 1 ,respectivelyattributedtoC -Nanti-symmetrystretchingandC -Hvibration Anotherrelativeweakbandemergesat 62 6cm- 1 TheUVRamanspectrumofaqueousPNBAsolutionissimilartothatofPNBAinethanol,whoseconcentrationishigherthanthatinaqueoussolution ,about 3mg/ml Buttheformergivesmoreinforma ionthanthelatter It sevidentthatanadditionalweakbandappearsat 1 1 78cm- 1 Andthereareseveralweakbandsbetween 1 35 0cm- 1 and 1 60 0cm- 1 ,respectivelyat 1 44 2cm- 1 ,1 461cm- 1 ,1 492cm- 1 It sworthwhiletonotethere snotanyenhancementaftersilvercolloidisaddedintoaqueousPNBAsolution ,showninFig 1b WhenanaliquotsilvercolloidisaddedintoaqueousPNBAsolution ,theinter actionbetweenthemtakesplaceimmediately Wenotonlyobservethecolorchangeofmixture,butalsoobtainthevisibleSERS ,whichcouldelucidatetheinteractionbetweenthemoleculesandthesilverparti cles Butwecouldn tobserveanyenhancementwiththeUVexcitation WecallitSurface -UnenhancedRamanScattering (SUERS) ThepoorperformanceofenhancementinUVregioncanbeexplainedbytheabsenceofbothsurface- plasmonresonanceandchargetransferexcitation Thesurfaceplasmonresonanceconditionisthattherealpartofdielectricconstantmustbenegativeandtheimaginarypartshouldapproachtozeroasmuchaspossible Silverworksbestbecauseitsdielectricconstantisalmostrealandnegativeinthevisiblere gion There snosurface - plasmonresonancebecausetherealpartofdielectricconstantforAgispositivewhiletheimaginarypartincreasesrapidlyfortransitionbetweenenergybandsinultravioletregion Thechargetransfer (CT)excitationoccursfromthehighestoccupiedstateofthemetaltotheelec tronaffinitylevelofthemolecule TheenergyrequiredforthisCTexcitationisfoundtobecomereso nancewiththelaserfrequenciesusedinSERSexperiments Thephotonenergyofultravioletusedinex perimentsisabout 3 8evsotheCTexcitationconditioncan tbesatisfiedinthisregion Fig.1 theUVRamanspectraofPNBAbefore (a)andafter (b)beingmixedwithsilvercolloid对硝基苯甲酸在水溶液和银胶中的紫外拉曼光谱(英文)紫外;;对硝基苯甲酸(PNBA);;拉曼光谱本文给出了紫外激发下的PNBA水溶液的拉曼光谱图,并对图中峰位做了相应的归属认证。本文还报道了PNBA在银胶中的表面非增强拉曼散射现象,并分析了导致该现象可能的原因[1] H Ratinen,M Kiviharju,SpectrochimActaA 1989,45(7):729. [2] R S Venkatachalam,F J Boerio,P G RothJ RamanSpectrosc,1988,19:281.

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