納米材料的濕法合成

1、論文中英文摘要作者姓名：孫旭平論文題目：納米材料的濕化學(xué)合成及新穎結(jié)構(gòu)的自組裝構(gòu)建作者簡介：孫旭平，男，1972年08月出生，2000年09月師從于中國科學(xué)院長春應(yīng)用化學(xué)研究所汪爾康研究員，于2006年03月獲博士學(xué)位。中文摘要圍繞論文題目“納米材料的濕化學(xué)合成及新穎結(jié)構(gòu)的自組裝構(gòu)建”，我們開展了一系列研究工作。通過濕化學(xué)途徑，在貴金屬納米粒子及其二維納米結(jié)構(gòu)和導(dǎo)電聚合物納米帶的合成方面進(jìn)行了深入研究。同時，利用界面自組裝及溶液自組裝技術(shù)，構(gòu)建了一些新穎結(jié)構(gòu)。本論文研究工作的主要內(nèi)容和創(chuàng)新點表現(xiàn)在以下幾個方面：(1)首次提出了一步加熱法制備多胺化合物保護(hù)的貴金屬納米粒子。我們利用多胺化合物(包

2、括聚電解質(zhì)和樹枝狀化合物)作為還原劑和保護(hù)劑，直接加熱貴金屬鹽和多胺化合物的混合水溶液，在不加入其它保護(hù)劑和還原劑的情況下，一步制備得到了穩(wěn)定的貴金屬金和銀的納米粒子。我們在實驗中發(fā)現(xiàn)，樹枝狀化合物聚丙烯亞胺能對反應(yīng)生成的金納米粒子的大小及成核和生長動力學(xué)進(jìn)行有效控制。我們還發(fā)現(xiàn)，室溫下直接混合濃的陽離子聚電解質(zhì)分支型聚乙烯亞胺和濃的HAuCl4水溶液可得到高濃度的、穩(wěn)定的膠體金。這種一步合成法操作簡單且方便易行，是一種制備多胺化合物保護(hù)的貴金屬納米粒子的通用方法；同時，本方法合成的納米粒子表面帶正電荷，可用作加工納米粒子功能化薄膜的構(gòu)建單元。(2)首次提出了一種無表面活性劑的、無模板的、大規(guī)

3、模制備導(dǎo)電聚合物聚鄰苯二胺納米帶的新方法。我們通過在室溫下直接混合鄰苯二胺和HAuCl4水溶液，在沒有表面活性劑或“硬模板”存在的條件下，獲得了長度為數(shù)百微米、寬度為數(shù)百納米、厚度為數(shù)十納米的聚鄰苯二胺。納米帶的自發(fā)形成可歸因于反應(yīng)中生成的金納米粒子催化的鄰苯二胺的一維定向聚合。本方法方便快速，無需加入表面活性劑或使用“硬模板”，且可用于大規(guī)模制備。止匕外，我們通過在室溫下直接混合AgNO3和鄰苯二胺水溶液，也獲得了大量的一維納米結(jié)構(gòu)，并發(fā)現(xiàn)其形貌可通過調(diào)節(jié)實驗參數(shù)而改變。我們還發(fā)現(xiàn)，當(dāng)溶液pH降低時，這些一維結(jié)構(gòu)將分解成水溶性的低聚體，而如果再次升高pH,這些低聚體又將自組裝形成一維納米結(jié)構(gòu)

4、。各種數(shù)據(jù)表明，這種一維納米結(jié)構(gòu)是由鄰苯二胺被AgNO3氧化后所生成的低聚體在溶液中自組裝而形成的。（3）發(fā)展了一系列可大量制備沿（111）晶面優(yōu)先生長的單晶金二維結(jié)構(gòu)（包括納米片及微米盤）的濕化學(xué)合成方法。在室溫下直接混合HAuCl4和鄰苯二胺水溶液，我們得到了大量的、呈六角形的、納米厚度的單晶金片，其尺寸達(dá)1.5m,鄰苯二胺和HAuCl4間的摩爾比是納米片形成的關(guān)鍵，這種納米片不僅能應(yīng)用于光學(xué)領(lǐng)域，還可用于加工具有獨(dú)特機(jī)械性能的新型結(jié)構(gòu)材料。我們通過直接加熱濃的HAuCl4和線型聚乙烯亞胺混合水溶液，也獲得了大量的金納米單晶片，其尺寸可達(dá)40仙m,反應(yīng)物濃度是獲得納米片的關(guān)鍵因素，這種具有

5、大的（111）晶面的單晶金片有望用做掃描隧道顯微鏡（STM）的基底。此外，通過加熱草酸-HAuCl4混合水溶液，我們還得到了大量的、尺寸達(dá)4m的、呈六角形的金二維結(jié)構(gòu)，但其厚度大于100nm,為微米盤，其大小和厚度可通過草酸的用量得到控制。（4）發(fā)展了一種基于溶液中的配位組裝的、室溫下方便合成有機(jī)-無機(jī)配位聚合物雜化材料的單分散亞微米膠體球的新方法。在室溫下直接混合H2PtCl6和對苯二胺水溶液，通過對苯二胺和PtCl62-在溶液中的配位自組裝，我們得到了亞微米尺寸的、單分散的、配位聚合物球形膠體球。實驗表明，粒子大小和多分散度可由反應(yīng)物間的摩爾比和濃度進(jìn)行控制，獲得單分散膠體球的最佳實驗條件

6、是1:1摩爾比和適中的濃度。本研究結(jié)果具有比較重要的意義：（1）它提供了一個溫和的、室溫條件下獲得單分散膠體粒子的合成方法，從而避免了獲得單分散的無機(jī)材料膠體粒子所必須的高溫反應(yīng)條件；（2）這種膠體粒子是一種新的雜化材料，它結(jié)合了兩種組分的優(yōu)點而具有多種屬性，因而可用在許多領(lǐng)域；（3）這種膠體粒子在強(qiáng)還原劑如NaBH4存在的情況下，由于其中的Pt陽離子組分被還原而發(fā)生分解，因此可用做易分解的膠體粒子模板加工中空球。止匕外，我們通過室溫下直接混合鄰苯二胺的N-甲基叱咯烷酮溶液和AgNO3水溶液，得到了亞微米的球形銀膠體粒子（平均粒徑達(dá)850nm）0實驗結(jié)果還表明，升高溫度有利于更大尺寸的銀粒子的

7、生成，溶劑對純的銀粒子沉淀物的獲得起著比較關(guān)鍵的作用。這些亞微米粒子的形成經(jīng)歷了兩個階段：（1）超飽和溶液中納米主粒子的成核；（2）形成的主粒子聚集成更大的均勻的粒子。（5）我們發(fā)展了一種在表面琉基功能化的電極表面有效固定Ru（bpy）32+的新方法。本方法同時運(yùn)用了溶液自組裝和固體表面自組裝兩種技術(shù)，即：先將Ru（bpy）32+和檸檬酸根陰離子保護(hù)的金納米粒子的水溶液按照一定比例混合，得到了Ru（bpy）32+-金納米粒子聚集體,然后把少量聚集體的懸浮液直接滴在表面琉基功能化的電極表面，從而實現(xiàn)Ru（bpy）32+在電極表面的有效固定。該方法簡單易行，制備的電極具有很好的穩(wěn)定性和電化學(xué)發(fā)光性

8、能，因而在固態(tài)電化學(xué)發(fā)光檢測方面具有很好的應(yīng)用前景；止匕外，該方法還可用于在固體表面構(gòu)建Au納米粒子多層膜。(6)發(fā)展了一種通過加熱3-曝吩丙二酸(3-thiophenemalonicacid,TA)和H2PtCl6混合水溶液直接制備小的Pt納米粒子的新方法，并通過對該膠體溶液用Ru(bpy)32+處理，得到了2+Ru(bpy)3-Pt納米粒子聚集體。通過對在裸電極表面的聚集體進(jìn)仃俯環(huán)電勢掃描，使得聚集體中的TA分子發(fā)生電化學(xué)聚合而在電極表面形成了穩(wěn)定的聚合物膜；由于該膜有效地避免了聚集體從電極表面脫落，從而我們得到了非常穩(wěn)定的、具有極好電化學(xué)發(fā)光性能的膜。本工作不但提供一種方便制備Pt納米粒

9、子的新途徑，而且還發(fā)展了一種在任何表面直接加工電化學(xué)發(fā)光檢測器的新方法，在固態(tài)電化學(xué)發(fā)光檢測方面具有重要應(yīng)用價值。(7)通過在室溫下直接混合H2PtCl6和Ru(bpy)3cl2水溶液，我們獲得了具有新穎形貌的、含有Ru(bpy)32+的微結(jié)構(gòu)。實驗結(jié)果表明，金屬價態(tài)、金屬種類及反應(yīng)物摩爾比和濃度對微結(jié)構(gòu)的形貌有重要影響，形成的微結(jié)構(gòu)都具有很好的電化學(xué)發(fā)光性能。這些微結(jié)構(gòu)給我們提供了一種新的功能材料，將在毛細(xì)管電泳或毛細(xì)管電泳微芯片的固態(tài)電化學(xué)發(fā)光檢測方面有著很好的應(yīng)用前景。關(guān)鍵詞：納米材料，濕化學(xué)，自組裝，電化學(xué)發(fā)光Wet-ChemicalRoutestothePreparationofNa

10、momaterialsandSelf-Assembly-BasedFabricationofNovelStructuresSunXupingABSTRACTBoththewet-chemicalpreparationofnanomaterialsandself-assembly-basedfabricationofnovelstructureshavebeenpaidconsiderableattention.Wecarriedoutseveralstudiesonthepreparationofnoblemetalnanoparticlesanditstwo-dimensionalnanos

11、tructuresandconductingpolymersnanobeltsviawet-chemicalroutes.Ontheotherhand,wefabricatedsomenovelstructuresthroughself-assemblyonplanarsolidsubstratesorinsolutions.Especially,theapplicationofsomestructuresinthefieldofsolid-stateelectrochemiluminescencedetectionisalsoexplored.Wehavedevelopedaheat-tre

12、atment-basedstrategyfortheone-steppreparationofpolyamine-protectednoblemetalnanoparticle.Withtheuseofthird-generationpoly(propyleneimine)(PPIG3)dendrimertosimultaneouslyactbothasthereducingagentandprotectiveagent,stablenoblemetalgoldnanoparticleshavespontaneouslyformedbyheatingasolutioncontainingHAu

13、Cl4andPPIG3.Asaresult,anadditionalstepofintroducingareducingagentaswellasaprotectiveagentisnolongerneeded.Itisfoundthatthesize,thenucleationandgrowthkineticsofthegoldnanoparticlesthusformedcanbetunedbychangingtheinitialmolarratioofPPIG3togold.Similarly,highlystableAgnanoclusterswithnarrowsizedistrib

14、utionhavebeenpreparedbyheatingaAgNO3/PPIG3aqueoussolutionwithouttheadditionalstepofintroducingotherreducingagentsandprotectagents.Itisfoundthatas-obtainedparticleisincoexistenceofAgandAg2Oandincreasingtemperatureresultsinboththedecreaseinnumberofsmallparticlesandtheincreaseinsizeoflargeparticles.Ina

15、ddition,suchthermalprocesshasbeensuccessfullyusedtoprepareamine-functionalizedpolyelectrolyte-protectedgoldnanoparticlesbydirectlyheatinganaqueoussolutioncontainingHAuCl4andpolyelectrolytes.FourpolyelectrolytesincludingN-3-(trimethoxysilyl)propylpolyethylenimine(Si-PEI),branchedpolyethylenmine(BPEI)

16、,linearpolyethylenimine(LPEI)andpoly(allylaminehydrochloride)(PAH)wereusedinourstudyandwell-stabilizedgoldnanoparticleswithrelativelynarrowsizedistributionwereobtained.Becausegoldnanoparticlesthusformedcanbecombinedwiththepropertiesofthepolyelectrolytesused,theyholdpromiseforuseinthebiomedicalandbio

17、analyticalfieldandontheotherhand,asbuildingblocksforthecreationofnanoparticles-containingthinfilms.ThisstrategywillbegeneraltootherpolyelectrolyteswiththesamechemicalstructureasthesefourpolyelectrolytesusedandtothepreparationofothernanoparticlessuchasAgnanoparticles.Furthermore,wehavefoundthathighly

18、concentrated,well-stablegoldcolloidscanbepreparedbydirectmixofconcentratedHAuCl4andBPEIaqueoussolutionsatroomtemperature.Wehavedevelopedforthefirsttimeanovelbutsimplesurfactantless,templatelessmethodforpreparingconductingpolymerpoly(o-phenylenediamine)nanobeltsonalargescale.ThemixofHAuCl4ando-phenyl

19、enediamineaqueoussolutionsatroomtemperatureresultsintheformationofalargequantityofprecipitate.Lowermagnificationscanningelectronmicroscopy(SEM)imageindicatesthattheprecipitateconsistsofalargequantityofuniformone-dimensionalstructures.HighermagnificationSEMimagefurtherrevealsthesestructuresaretranspa

20、rentnanobeltswithseveralhundredmicrometersinlength,severalhundrednanometersinwidth,andseveraltennanometersinheight.AlsoobservedintheseSEMimagesareanumberofnanoparticles.TheX-raydiffraction(XRD)analysisoftheresultingprecipitaterevealstheformationofamorphouspoly(o-phenylenediamine)polymerswithlargercr

21、ystallinesizeaswellascrystallinegold.ElementalanalysisoftheresultingprecipitateusingsecondaryelectronsbySEMindicatesthebeltsarepoly(o-phenylenediamine)polymersbuttheparticlesaregoldparticles.Thepossibleformationofthenanobeltscanbeexplainedasfollows:ThereductionofHAuCl4byo-phenylenediamineleadstothef

22、ormationofgoldnanoparticleswiththeoccurrenceofo-phenylenediamineoligomersfirst,thengoldnanoparticlesproducedserveasactivecatalyststocatalyzetheorientedoxidativepolymerizationofothero-phenylenediaminemonomersbyHAuCl4alongtheoligomersproduced,resultingintheformationofpoly(o-phenylenediamine)nanobelts.

23、Furthermore,wehavefoundthatmixingofAgNO3ando-phenylenediamineinaqueousmediumresultsintheformationofuniformone-dimensionalstructures.However,theformationofsuch1Dstructureinvolvesthefollowingtwostages:(1)Theoxidationofo-phenylenediaminebyAgNO3leadstotheformationofindividualo-phenylenediamineoligomers.

24、(2)Theresultingindividualoligomersself-assemblytoformuniformlarger1Dstructures.Interestingly,decreasingmediumpHcanbreakthese1Dstructuresaparttoformindividualoligomers,orviceversa.Itisalsofoundthatboththeconcentrationandmolarratioofreactantshaveconsiderableinfluencesonthemorphologiesofthestructuresth

25、usformed.Wehavedevelopedseveralwet-chemicalapproachesforthelarge-scalepreparationoftwo-dimensional,single-crystallinegoldstructuresincludingnanoplatesandmicrodisks.Themixofanappropriatevolumeofanaqueoussolutionoffreshlypreparecb-phenylenediamineandHAuCl4atroomtemperaturewith1:1molarratioofo-phenylen

26、ediaminetogoldgraduallyleadstoalargequantityofprecipitate,whichiscollectedbycentrifugation,washedseveraltimeswithTHFandwater,andthensuspendedinwater.ThelowermagnificationSEMimageindicatesthattheprecipitateconsistsofalargeamountofparticles,whilethehighermagnificationSEMimageclearlyrevealsthattheparti

27、clesaremicrometer-scaleplates(about1.5pminsize),mainlyhexagonalinshape.Thedistancebetweentwoplanesofoneplatestandingagainsttheglasssubstrateindicatesthattheseplatesarenanoplates.Thecorrespondingenergy-dispersiveX-rayspectrum(EDS)showsthesenanoplatesarepuremetallicgold.Twosurfaceplasmonabsorptionband

28、satabout680and925nmwhicharisefromthelongitudinalplasmonresonanceofgoldparticlesareobservedforthesegoldnanoplates,providinganotherpieceofevidencefortheformationofanisotropicgoldparticles.Itsuggeststhatthequantityofo-phenylenediamineinthesolutioniscrucialtoyieldinggoldnanoplatesandwemaysuggestthato-ph

29、enylenediaminemoleculesserveasasofttemplateandkineticallycontrolthegrowthratesofvariousfacesofgoldparticlesbyselectivelyadsorbingontothecrystallographicplanes,thusresultingintheformationoflargesingle-crystallinegoldnanoplates.Theimportanceoftheplatelet-likegoldparticlesisnotrestrictedtooptics;except

30、ionallyinterestingmaterialswithuniquemechanicalpropertiescanbeobtainedwithsuchcolloids.Apolyamineprocesshasalsobeensuccessfullyusedforthehigh-yieldpreparationofsingle-crystallinegoldnanoplateswithseveral10叩insize,mainlyhexagonalinshape,carriedoutbyheatingaconcentratedaqueoussolutionofLPEIandHAuCl4at

31、100C.Thefollowingexperimentalfacts(1)therearenogoldbyproductswithothershapesexceptthenanoplatesexistingintheresultingproductsand(2)addingNaBHtothecolorlesssupernatantaftertheterminationofreactiongivesnogoldparticlesduetothedepletionofHAuCl4inthemixturebyLPEIindicatethatthisheat-treatment-basedpolyam

32、ineprocessisahigh-yieldapproachforthepreparationoflargegoldnanoplates.Itisfoundthattheconcentrationofreactantsiscrucialtotheformationofnanoplates.As-preparedgoldnanoplateswithalargeAu(111)facemayholdpromiseforscanningtunnelingmicroscopy(STM)substrates.Furthermore,heatinganaqueousoxalicacid/HAuCl4sol

33、utionhasbeenproventobeaneffectiveandfacileapproachforthelarge-scaleproductionofmicrosized,single-crystalline,hexagonalgoldmicroplateswithathicknessabove100nm.Boththesizeandthethicknessoftheseplatescanbecontrolledbythemolarratioofoxalicacidtogold.Itisalsofoundthattheconcentrationofreactantsstronglyin

34、fluencestheformationofthegoldplates.Wehavedemonstratedanovelcoordination-basedstrategytothefabricationofsubmicrometer-scale,monodisperse,sphericalcolloidsoforganic-inorganichybridmaterials.Themixofp-phenylenediamineandH2PtCl6aqueoussolutionsatroomtemperatureresultsintheformationofalargeamountofpreci

35、pitate.LowmagnificationSEMimageofas-preparedprecipitateindicatesthattheprecipitateconsistsofalargequantityofmonodisperse,submicrometer-scaleparticlesabout420nmindiameter.HighermagnificationSEMimagerevealsthattheseparticlesaresphericalinshapeandwell-separatedfromeachother,andalocalmagnificationofasin

36、glecolloidalspherebytransmissionelectronmicroscopy(TEM)indicatesthattheresultingparticleshaveelectron-microscopicallyperfectlysmoothsurface.Thechemicalcompositionoftheresultingcolloidswasdeterminedbyenergy-dispersedspectrum(EDS)andtheoccurrenceofthepeaksofPt,Cl,C,andNindicatesthatthecolloidsareprodu

37、ctsofp-phenylenediamineandH2PtCl6.Apossibleformationprocessisbrieflypresentedasfollowing:Whenp-phenylenediamineandPtCl62-aremixedtogether,thetwonitrogenatomsontheparapositionsofonep-phenylenediaminearomaticringcancoordinatetotwodifferentPt(IV)cations,resultinginp-phenylenediamine-bridgedstructure,an

38、dthePtspeciescontainedinas-formedstructurecanfurthercaptureotherp-phenylenediaminemoleculesbycoordinationinteractionsalongdifferentdirections.Thiscoordination-inducedassemblyprocesscanproceedrepeatedlyuntilthedepletionofreactantsinthesolution,resultingintheformationoflargecoordinationpolymers,finall

39、y.Itisfoundthattheparticlesizeandpolydispersitycanbecontrolledbythemolarratioandconcentrationofreactants,however,theoptimumexperimentalparametersfortheproductionofmonodispersecolloidsare1:1molarratioandmoderateconcentrationofthetworeactants.Ourobservationsaresignificantforthefollowingreasons.(1)Itpr

40、ovidesamild,roomtemperatureroutetofinecolloids,avoidingtheuseofhightemperature,whichiscrucialtotheformationoffinecolloidsofinorganicmaterials.(2)Suchcolloidsarenewhybridmaterialswithversatilepropertiesprovokedbycombiningthemeritsoftwosourcesandmayfindapplicationsinmanyfields.(3)Suchcolloidsareeasily

41、brokenupbyastrongreducingreagent,suchasNaBH4,becauseofthereductionofthePtcationscontainedtherein,andtherefore,theyholdpromiseaseasilydecomposablecolloidaltemplatesforthefabricationofhollowspheresforavarietyofapplications.Wehavealsodemonstratedtherapidpreparationofuniform,large,sphericalAgsphereswith

42、relativelylowpolydispersitythroughasimplewet-chemicalroute.TheformationofAgparticleswithabout750nmindiameteroccursinasingleprocess,carriedoutbydirectmixofAgNO3aqueoussolutionando-phenylenediamineN-methyl-2-pyrrolidone(NMPD)solutionatroomtemperature.TheformationofmonodisperseAgcolloidsinourpreviousst

43、udycanbeexplainedasfollows:AgNO3isreducedbyo-phenylenediaminetoformmetallicAgatoms.Withelapsedtime,newAgatomsaregeneratedinthissystemandnucleationoccursastheconcentrationofAgatomsreachescriticalsupersaturation,resultingintheformationofnuclei.Thenucleigrowtonanoscaleprimaryparticlesbyfurtheradditiono

44、fAgatoms,andthentheprimaryparticlesaggregatetoformlargeAgsphereswithrelativelynarrowsizedistribution.Itisfoundthatthatincreasingtemperatureresultsinincreasingparticlesize.WehavefoundthatthemixofAgNO3ando-phenylenediamineaqueoussolutions,underotherwiseidenticalconditions,yieldsprecipitateconsistingof

45、alargequantityoflargesphericalAgparticlesandbelt-shapedstructurescorrespondingtotheoxidativeproductsofo-phenylenediaminebyAgNO3.NMPDisapowerfulsolventwithlowtoxicityandbroadsolubility,completelysolubleinwateratalltemperaturesandsolubleinmostorganicsolvents.WethereforechooseNMPDinourpresentstudyasane

46、ffectivecosolventtodissolvetheoxidativeproductsofo-phenylenediamineinatimelymanner,preventingthemfromprecipitatingwithAgparticlesandleadingtotheformationofpureAgspheres.Wehavedevelopedanovelmethodbasedonbothsolution-andplanarsolidsubstrate-basedassemblytechniquesforeffectiveimmobilizationofRu(bpy)32

47、+onsulfhydryl-derivatedelectrodesurfacesforsolid-stateelectrochemiluminescenedetectionapplication.Thewholeimmobilizationprocessinvolvesthefollowingtwosteps:(1)TheadditionofRu(bpy)32+cationsintocitrate-cappedgoldnanoparticles(AuNPs)solutionresultsintheformationofaRu-AuNPsprecipitateduetoelectrostatic

48、interactions-drivenassemblyofthepositivelychargedRu(bpy)32+cationsandthenegativelychargedcitrateionscoatingontheAuNPs;(2)ThesuspensionofRu-AuNPswasplacedonthesulfhydryl-derivatedITOelectrodesurface.Theenergy-dispersedspectrum(EDS)oftheresultingprecipitateindicatestheprecipitateconsistsofRu(bpy)2+and

49、AuNPs.TheabsenceofthepeakofSelementintheEDSmaybeattributedtothefollowingtworeasons:(1)ThecontentofSelementitselfistoolowtobedetected.(2)ThesulfhydrylgroupsarelocatedbelowtheRu-AuNPsfilm,andthesubstrateisnearlycompletelycoveredbytheRu-AuNPsfilm.Itisfoundthatthemodificationofsubstratewithsulfhydrylgro

50、upandtheresultantstrongAu-SinteractionsbetweensulfhydrylgroupandAuNPsarecrucialtotheeffectiveimmobilizationofsuchRu-AuNPsonthesurfaceandthereisnostablefilmformedonbareITOsurface.TheRu-AuNPs-modifiedITOelectrodeisquitestable,exhibitsexcellentelectrochemiluminescenebehavior,andhenceholdsgreatpromisefo

51、rsolid-stateelectrochemiluminescenedetectionincapillaryelectrophoresis(CE)oraCEmicrochip.ItprovidesanewmethodologyforfabricationofstableRu(bpy)32+-containingstructuresonasolidelectrodesurfaceforsolid-stateelectrochemiluminescenedetectionand,ontheotherhand,alsoprovidesaninterestingmethodofimmobilizat

52、ionofnanoparticlesonthesurfacesforapplications.WehavedevelopedasimplethermalprocessforthepreparationofsmallPtnanoparticles,carriedoutbyheatingaH2PtCl6/3-thiophenemalonicacid(TA)aqueoussolutionwithouttheadditionofotherreducingagentsandprotectiveagents.TheformationofsuchPtnanoparticlescanbeattributedt

53、othedirectredoxbetweenTAandPtCl62-.ItisfoundthatsuchPtnanoparticleswerequitestableforseveralmonthswithoutanyobservableaggregation,indicatingthatTAservesasaveryeffectiveprotectiveagentfortheformationofPtnanoparticles,whichcanbeattributedtothefactthatthesulfuratominTAhasaverystrongnucleophilicitywithl

54、one-pairelectronsandsuchalone-pairelectroncanformatypeofdonor-acceptorcomplexwiththePtatomontheparticlesurface,yieldingTA-protectedPtnanoparticles.ThefollowingtreatmentofsuchcolloidalPtsolutionwithRu(bpy)32+causestheassemblyofPtnanoparticlesintoaggregates.Giventheacidicreactioncondition,thePtparticl

55、esurfaceismainlycoveredbyprotonatedcarboxylicacidgroupsandthustheelectrostaticinteractionsbetweenpositivelychargedRu(bpy)32+andPtnanoparticlesareonlypartiallyresponsiblefortheformationoftheaggregates.Ontheotherhand,bothTAandRu(bpy)32+arerichinetypebondsandthestrongintermolecular-1interactionsbetweenthemalsocontributetotheformationoftheaggregatesviaself-assembly.Themostattractivepointisthatdirectlyplacingsuchaggregatesonanybaresolidelectrodesurfacescanproduceverystablefilmsexhibitingexcellentelectrochemiluminescencebehaviors.Theformationofthestablefilmoftheaggregatesonabareelectrodesurfacecan