Luminol chemiluminescence induced by silver nanoparticles in(4)

188N.Lietal./JournalofPhotochemistryandPhotobiologyA:Chemistry

215 (2010) 185–190

Fig.4.Time-dependentUV–visabsorptionspectraduringthereactionbetweenCuSO4andAgNPsinthepresenceofNaBr.5selectedspectrawererecordedat2.5,5.0,10.0,18.0and32.0saftertheadditionofCuSO4inthemixingsolutionoftheAgcolloidwithNaBr.TheinsetsdisplaythecorrespondingtemporalSPRabsorptionatca.410nm(SPRabsorptionnaximumwavelength)atatimeintervalof0.5second.Conditions:1×10 3mol/LofCuSO4,0.01mol/LofNaBr,3×10 4mol/LofAg.

55.2 ,73.3 exactlycorrespondedtothepeaksof(200),(220),(222),(420)ofAgBr,respectively.Otherpeaksat27.3 ,45.1 ,53.5 exactlycorrespondedtothepeaksof(111),(220),(311)ofCuBr,respectively.TheresultsindicatedthatCuBrandAgBrwereareductionproductandanoxidationproduct,respectively.ItstronglysupportedthatAgNPscouldbeoxidizedbyCuSO4bytheaidofNaBr.Besides,Cu(I)compoundswereoneofmainproductsinthereaction.

Furthermore,Cu2pX-rayphotoelectronspectraofthereac-tionproduct,thebrownpowders,derivedfromtheprecipitates,areshowninFig.6(B).Allbindingenergies(BE)werecalibratedwithrespecttotheC1sBEat284.6eV.AscanbeseenfromFig.6,theCu2pspectrumoftheprecipitateswascurve- ttedintofourcomponentsat932.0,934.4,951.8,and954.3eV.Thecomponentsat932.0and951.8eVwereattributedtotheCu(I),whichisingoodagreementwithCu(I)2pXPSofpureCuBrasshowninFig.6(A).Thecomponentsat934.4and954.3eVwereattributedtoCu(II),beingingoodagreementwithCu(II)2pXPSofCu(II)inreportedresults[33].Additionally,thecomponentsat941.8and943.7eVinFig.6(B)belongtotheCu(II)3pspectrum.ThedataofXPSdemon-stratedthattheaverageatomicratio(Cu(I)/Cu(II))was1.6:1

on

Fig.5.(A)TypicalXRDpatternofCuBr.(B)XRDpatternoftheprecipitatefromtheCuSO4–AgNPs–NaBrreactionsystem.(C)TypicalXRDpatternof

AgBr.

Fig.6.X-rayphotoelectronspectraof(A)Cu2pofpureCuBrand(B)Cu2poftheprecipitatefromtheCuSO4–AgNPs–NaBrreactionsystem.

thesurfaceofprecipitates,indicatingthatCu(I)wasmainformofCu.

Therefore,thereactionbetweenCuSO4andAgNPsinthepres-enceofNaBrproducedCu(I)complexinits nalproducts.IthasbeenreportedthatCu(I)canreactwiththedissolvedoxygentoproducesuperoxide[34,35].TheCLoftheluminol/superoxidesys-tem,whichwasoneofthecommonCLsystems,hasbeenstudieddeeplyinthepast[36–38].ItisreasonabletosuggestthattheinjectionofluminoltotheCu(I)solutioncouldyieldCLemission.Subsequently,theCLreactionofCuBrwiththeluminolwasexam-ined.CuBrwasdissolvedintoaNaBrandHClsolution.AsshowninFig.7,themixtureofothercocomitants(AgNPs–AgNO3–NaBr)wasexployedinCLtestandnoconsiderableCLsignalappearedwiththeinjectionofluminol.However,whenluminolwasinjectedintotheCuBrsolution,aconsiderableCLemissionwasobserved.Con-sideringAgNPsorAg(I)complexmightcoexistwithCu(I)complex,AgNPsorAgNO3wasalsoaddedintotheCuBrsolutionfortheCLtests.InthepresenceofAgNO3orAgNPs,avisibleincreasein

the

Fig.7.Chemiluminescencekineticcurves.(a)Controlsolution:themixtureofAgNPs–AgNO3–NaBr.(b)CLoftheCu(I)complexsolutionwithluminol(dotline).Coexistreagents,AgNO3(c)(shotline)orAgNPs(d)(shotdotline)wereaddedintotheCuBrsolutionforCLtests.TheinsetsdisplaystheinhibitioneffectofSODontheCu(I)–luminolCL.Conditions:1×10 4mol/LCuBrin0.01mol/LNaBrand0.1mol/LHClsolution,3×10 4mol/LAg,1×10 5mol/LAgNO3,1×10 4mol/Lluminolin0.1mol/Lcarbonatebuffers(pH10.0).Controlsolution:3×10 4mol/LAg,1×10 5mol/LAgNO3,0.01mol/LNaBr.