Luminol chemiluminescence induced by silver nanoparticles in

JournalofPhotochemistryandPhotobiologyA:Chemistry215 (2010) 185–190

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JournalofPhotochemistryandPhotobiologyA:

Chemistry

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LuminolchemiluminescenceinducedbysilvernanoparticlesinthepresenceofnucleophilesandCu2+

NaLi,JieGu,HuaCui

CASKeyLaboratoryofSoftMatterChemistry,DepartmentofChemistry,UniversityofScienceandTechnologyofChina(USTC),230026Hefei,Anhui,PRChina

articleinfoabstract

Itwasfoundthatsilvernanoparticles(NPs)inthepresenceofnucleophilesandCu2+couldinduceluminoltoproducechemiluminescence(CL).TheAgNPs–NaBr–CuSO4–luminolsystemwaschosenasamodelsystemtostudytheCLmechanism.UV–visabsorptionspectrashowedthatsilvernanoparticlesinthepresenceofNaBrcouldreactwithCuSO4beforeinjectionofluminol.TheX-raydiffractionpat-ternsandX-rayphotoelectronspectrademonstratedthatCu(I)complexwasakeyreactionproductinAgNPs–NaBr–CuSO4system.Besides,itwasalsofoundthatsuperoxidedismutasecouldinhibittheCL,revealingthatasuperoxideanionwasinvolvedintheCLreaction.Onthisbasis,itwassuggestedthattheluminolCLinducedbysilvernanoparticlesinthepresenceofNaBrandCu2+derivedfromCu(I)complexformedviathereductionofCuSO4byAgNPsbytheaidofNaBr,whichreactedwiththedissolvedoxygentogeneratethesuperoxideanion;thenthesuperoxideanionreactedwithluminoltoproduceCL.Br asanucleophilewasconsideredtodecreasetheoxidationpotentialofsilvernanoparticlessothatCu(II)isreadilyreducedtoCu(I)andtobindtoCu(I)preventingCu(I)fromdismutationinwater.Asexpected,othernucleophilessuchasCl ,I andthiosulfate,whichwerealsoef cienttodecreasetheoxidationpotentialofAgNPsandbindtoCu(I),couldalsoinducetheluminolCL.

© 2010 Elsevier B.V. All rights reserved.

Articlehistory:

Received4May2010

Receivedinrevisedform30July2010Accepted17August2010

Available online 24 August 2010Keywords:

AgnanoparticleNucleophile

ChemiluminescenceLuminol

1.Introduction

Inrecentyears,nanoparticles(NPs)havebeenwidelystudiedfortheirexcellentproperties[1–3]andtheirpotentialapplicationsinmicroelectronics,optics,electronics,magneticdevices,andcataly-sis[4–8].Intheseinvestigations,anumberofreportsfocusonthepropertiesofNPsinthepresenceofnucleophiles[9–11].Absorp-tionofthesenucleophilesonsilverNPscandrasticallychangetheiropticalpropertiesandredoxreactivity[12,13].Thesilveratomsonthesurfacearecoordinativelyunsaturated.Onemayexpectthatunoccupiedorbitalsexistonthesurfaceintowhichanucleophilicreagentcandonateanelectronpair.Theconsequenceisnotonlyachangeintheopticalabsorptionofthecolloidalparticlesbutalsoachangeintheirreactivity.Theinteractionofsurfaceatomswithnucleophilesleadstoapartialoxidationofsurfaceatoms,whiletheinteriorofcolloidalparticlesreceivesacorrespondingnegativechargewhichcanbepickedupbytheelectronacceptors.Cu2+hasbeenusedasatypicalelectronacceptortotesttheenhancedredoxcapabilityofthesilverNPsinthenucleophiles.Withoutthenucle-ophiles,additionofCu2+couldnotresultintheoxidationofsilverparticles.TheFermileverofsilverNPsmodi edbynucleophileswassigni cantlyshiftedtowardanegativepotential,andismore

Correspondingauthor.Tel.:+865513606645;fax:+865513600730.E-mailaddress:hcui@(H.Cui).1010-6030/$–seefrontmatter© 2010 Elsevier B.V. All rights reserved.doi:10.1016/j.jphotochem.2010.08.016

negativethanthestandardredoxpotentialoftheCu2+/Cu+cou-ple.Asaresult,thereducingabilityofsilverNPsinthepresenceofnucleophilesisenhancedsothatCu2+couldoxidizesilverparticlesbytheaidofthenucleophiles.Besides,otherelectronacceptorshavebeeninvestigatedtotesttheenhancedredoxcapabilityofthesilverparticlesinthepresenceofnucleophiles.Thefactthattheoxidationofmetalbyoxygenisfacilitatedbyanucleophilicreagentiswell-known[9,10,13].CytochromecwasalsofoundtoundergoreductionwhenintroducedintoasuspensionofcolloidalsilvermixedwithaqueousBr andI inmicromolarconcentration[14].

Aclassofhomogeneouschemicalreactions,chemilumines-cence(CL)reactionsaccompaniedbylightemissions,havebeenintensivelyinvestigatedformanyyears.Recently,metalNPswereemployedintheCLstudyasacatalyst,reductant,luminophor,andenergyacceptor[15–27].However,NPsinthepresenceofnucle-ophileswiththeenhancedreducingabilitywererarelyinvestigatedforCLreactions.Inourpreviouswork,itwasfoundthatinthepres-enceofKI,silverNPsasareductantcouldinducetheliquid-phaseCLoflucigenin[18].Furthermore,theCLbehavioroflucigenin-Agcol-loidinthepresenceofothernucleophilessuchasthiourea,sodiumthiosulfate,cysteine,mercaptoaceticacid,andmercaptopropionicacidwasexplored.InsteadofAgNPs,AuandPtwerealsoexaminedforinducinglucigeninCLinthepresenceofvariousnucleophiles.Inthepresentwork,luminolCLreaction,anotherimportantCLreac-tion,inducedbysilverNPsinthepresenceofnucleophileswas