Novel one-step synthesis of amine-stabilized aqueous colloidal gold nanoparticles

新型氨基修饰的纳米金的快速合成

Novel one-step synthesis of amine-stabilized aqueous colloidal gold nanoparticles

PhysicalandMaterialsChemistryDivision,NationalChemicalLaboratory,Dr.HomiBhabhaRoad,Pune411008,India

Received24thFebruary2004,Accepted4thMay2004

FirstpublishedasanAdvanceArticleontheweb19thMay2004

Downloaded by TONGJI UNIVERSITY LIBRARY on 23 March 2013Published on 19 May 2004 on http://www.wendangwang.com | doi:10.1039/B402823F

Wedemonstrateasimpleone-stepprocessforthesynthesisofwater-dispersedsphericalgoldnanoparticlesusingthemultifunctionalmoleculeoleylamine(OLA)thatelectrostaticallycomplexeswithaqueouschloroaurateions,reducesthem,andsubsequentlycapsthenano-particlesthusformed.Thegoldparticlesthusformedwereofthefccphaseandwerefairlymonodispersewithparticularconcentrationsofcappingmolecules.

AfterBrustetal.1demonstratedalkanethiolcappedAunano-particlesformationinabiphasicmixture,therehasbeenanenormousefforttofunctionalizetheseparticleswithterminallyfunctionalizedalkanethiolsorarenethiolates.2However,thesegoldnanoparticlesarepreparedinorganicsolventsandtheywereredispersibleinnonpolarandweaklypolarorganicsolvents.3Goldparticlesarealsopreparedbychemicalreduc-tionofachlorideprecursorunderaqueousconditions:forexample,thewell-knownTurkevichmethod4involvesreduc-tionofHAuCl4bysodiumcitrateinwaterwhileSchmidhasdemonstratedthatthereductionofAuCl(PR3)byB2H6leadstoAu55nanoclusters.5However,astudyoftherecentliteraturerevealstheneedfornewpreparativemethodsleadingtomonodisperseparticlesofadjustablesizeandshape.6Develop-mentofsynthesisprotocolsforrealizingmonolayer-protectedwater-dispersiblegoldnanoparticles,ontheotherhand,hasreceivedconsiderablylessattentionandwouldhaveimmediateapplicationsincatalysis,sensors,molecularmarkers,andinparticular,biologicalapplicationssuchasbiolabelinganddrugdelivery.Recognizingthatthesolubilityofgold,andinsomeinstancessilver,monolayer-protectednanoclusters(MPCs)inwater/stronglypolarorganicsolventswouldbedominatedbytheterminalfunctionalityofthecappingmonolayer,7anumberofdifferentthiol-coordinatedfunctionalgroupssuchastio-pronin,8glutathione,9succinicacid,10sulfonicacid11andammoniumions12havebeenshowntoresultinMPCsthatarereadilydispersibleinwater.

Recentlytherehavebeenseveralreportswheretertiaryamine/amineadductswereusedtoformAgnanoparticlesusingorganometallicAgcomplexesinorganicmedium.13AsimilarapproachwasalsoundertakenforAuaminesupramolecularcomplexesintoluenewhichleadstoAuparticlesafterdecomposition.14Inaddition,thereisthedemonstrationthataminederivativescomplexwithgoldnanoparticlesinamannersimilartothatofthiolderivativesandrecentlytryptophanhasbeenusedtosynthesizeAunanoparticles.15Inaveryrecentdevelopment,Aunanoclusterswerealsosynthesizedusing

{Electronicsupplementaryinformation(ESI)available:FTIR,TEM,UV-visandXRDresults.Seehttp://www.wendangwang.com/suppdata/jm/b4/b402823f/aminophenoxyethyletherasareducingagentatanaqueous–chloroforminterface,wherethepHwascontrolledtotransfertheorganicmoleculefromchloroformtotheaqueousphase.Insharpcontrasttooursystemwhichindicatesverypreciseparticlesizecontrolwithamineconcentration,thereportedmethodhasmuchlesscontrolovertheparticlesizeandtheyarehighlypolydispersedandinterlinked(particlesize¢100nm)andrevealsthephasetransfertochloroformwithlongtermstirring.15fUsingaminechemistryforreductionaswellassurfacemodi cation,wehaveshownforthe rsttimethatgoldnanoparticlescanbepreparedinwaterdirectlybycomplexa-tionwithalkylaminemoleculeswhereitactsasreducingagentandthensubsequentlystabilizesthegoldparticles.Preparationofgoldnanoparticleswascarriedoutinasimpleone-potprocess.Thetypicalprocedureisaddressedinthereferencessection.16Thisnewapproachopensuptheexcitingpossibilityofsurfacemodi cationofgoldnanoparticleswithaminoacidswherebindingwiththegoldnanoparticlessurfacemaybeaccomplishedthroughtheaminefunctionality.Inthiscom-munication,wereportour ndingthatcappingaqueousgoldnanoparticleswiththeaminemoleculesstabilizestheparticlesinsolutionnearlycovalentlyandalsorendersthemwater-dispersible.Theamine-cappednanoparticlesmaybeobtainedintheformofadrypowderafterevaporationoftheaqueouscomponent,thispowderbeingextremelystableinairandreadilyredispersibleinwateraswellasnonaqueoussolvents.Developmentofprotocolsforthesynthesisofwater-dispersiblenanoparticleshasimmenseapplicationsinavarietyof elds,butclearlymoresoinbiorelatedareassuchasbiolabelingandbiosensing.Weuseinthisstudyprimaryaminescontaininglongalkylchainssincethesecompoundsareknowntoself-assembleandhavebeenusedastemplatingagentsforthesynthesisofmesoporousmaterials.17Thegoldnanoparticlesisolatedasapowder(2.45g,94%yieldbasedongold)werealsoreadilyredispersedinnonpolarsolventssuchastolueneandhexaneaswellasaqueousmedia,showingnosignofpre-cipitationformonthswhileas-preparedparticleswerestableformonthsinwateraswell.

Fig.1aandbshowtheUV-visspectraandtheXRDpatternofgoldnanoparticlespreparedunderaqueousconditionswithamineat0.1Mconcentrationrespectively.Themaximumataround520nmisapeculiarcharacteristicofthegoldsurfaceplasmonband.18aForthehighestconcentrationofamineasreducing/stabilizingagentthesurfaceplasmonbandappearsat522nmandremainsatthesamemaximumfortheOLAconcentrationof0.05M.Afurtherdecreaseintheamineconcentrationshiftsthebandat529nmsuggestinganincreaseintheparticlesize.Theplasmonbandshiftsto544nm(OLA;561023M)andgraduallybroadensandshiftsto571nm

J.Mater.Chem.,2004,14,1795–1797

1795

DOI:10.1039/b402823f

ThisjournalisßTheRoyalSocietyofChemistry2004

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