纳米材料的湿法合成

1、论文中英文摘要作者姓名：孙旭平论文题目：纳米材料的湿化学合成及新颖结构的自组装构建作者简介：孙旭平，男，1972年08月出生，2000年09月师从于中国科学院长春应用化学研究所汪尔康研究员，于2006年03月获博士学位。中文摘要围绕论文题目“纳米材料的湿化学合成及新颖结构的自组装构建”，我们开展了一系列研究工作。通过湿化学途径，在贵金属纳米粒子及其二维纳米结构和导电聚合物纳米带的合成方面进行了深入研究。同时，利用界面自组装及溶液自组装技术，构建了一些新颖结构。本论文研究工作的主要内容和创新点表现在以下几个方面：(1)首次提出了一步加热法制备多胺化合物保护的贵金属纳米粒子。我们利用多胺化合物(包

2、括聚电解质和树枝状化合物)作为还原剂和保护剂，直接加热贵金属盐和多胺化合物的混合水溶液，在不加入其它保护剂和还原剂的情况下，一步制备得到了稳定的贵金属金和银的纳米粒子。我们在实验中发现，树枝状化合物聚丙烯亚胺能对反应生成的金纳米粒子的大小及成核和生长动力学进行有效控制。我们还发现，室温下直接混合浓的阳离子聚电解质分支型聚乙烯亚胺和浓的HAuCl4水溶液可得到高浓度的、稳定的胶体金。这种一步合成法操作简单且方便易行，是一种制备多胺化合物保护的贵金属纳米粒子的通用方法；同时，本方法合成的纳米粒子表面带正电荷，可用作加工纳米粒子功能化薄膜的构建单元。(2)首次提出了一种无表面活性剂的、无模板的、大规

3、模制备导电聚合物聚邻苯二胺纳米带的新方法。我们通过在室温下直接混合邻苯二胺和HAuCl4水溶液，在没有表面活性剂或“硬模板”存在的条件下，获得了长度为数百微米、宽度为数百纳米、厚度为数十纳米的聚邻苯二胺。纳米带的自发形成可归因于反应中生成的金纳米粒子催化的邻苯二胺的一维定向聚合。本方法方便快速，无需加入表面活性剂或使用“硬模板”，且可用于大规模制备。止匕外，我们通过在室温下直接混合AgNO3和邻苯二胺水溶液，也获得了大量的一维纳米结构，并发现其形貌可通过调节实验参数而改变。我们还发现，当溶液pH降低时，这些一维结构将分解成水溶性的低聚体，而如果再次升高pH,这些低聚体又将自组装形成一维纳米结构

4、。各种数据表明，这种一维纳米结构是由邻苯二胺被AgNO3氧化后所生成的低聚体在溶液中自组装而形成的。（3）发展了一系列可大量制备沿（111）晶面优先生长的单晶金二维结构（包括纳米片及微米盘）的湿化学合成方法。在室温下直接混合HAuCl4和邻苯二胺水溶液，我们得到了大量的、呈六角形的、纳米厚度的单晶金片，其尺寸达1.5m,邻苯二胺和HAuCl4间的摩尔比是纳米片形成的关键，这种纳米片不仅能应用于光学领域，还可用于加工具有独特机械性能的新型结构材料。我们通过直接加热浓的HAuCl4和线型聚乙烯亚胺混合水溶液，也获得了大量的金纳米单晶片，其尺寸可达40仙m,反应物浓度是获得纳米片的关键因素，这种具有

5、大的（111）晶面的单晶金片有望用做扫描隧道显微镜（STM）的基底。此外，通过加热草酸-HAuCl4混合水溶液，我们还得到了大量的、尺寸达4m的、呈六角形的金二维结构，但其厚度大于100nm,为微米盘，其大小和厚度可通过草酸的用量得到控制。（4）发展了一种基于溶液中的配位组装的、室温下方便合成有机-无机配位聚合物杂化材料的单分散亚微米胶体球的新方法。在室温下直接混合H2PtCl6和对苯二胺水溶液，通过对苯二胺和PtCl62-在溶液中的配位自组装，我们得到了亚微米尺寸的、单分散的、配位聚合物球形胶体球。实验表明，粒子大小和多分散度可由反应物间的摩尔比和浓度进行控制，获得单分散胶体球的最佳实验条件

6、是1:1摩尔比和适中的浓度。本研究结果具有比较重要的意义：（1）它提供了一个温和的、室温条件下获得单分散胶体粒子的合成方法，从而避免了获得单分散的无机材料胶体粒子所必须的高温反应条件；（2）这种胶体粒子是一种新的杂化材料，它结合了两种组分的优点而具有多种属性，因而可用在许多领域；（3）这种胶体粒子在强还原剂如NaBH4存在的情况下，由于其中的Pt阳离子组分被还原而发生分解，因此可用做易分解的胶体粒子模板加工中空球。止匕外，我们通过室温下直接混合邻苯二胺的N-甲基叱咯烷酮溶液和AgNO3水溶液，得到了亚微米的球形银胶体粒子（平均粒径达850nm）0实验结果还表明，升高温度有利于更大尺寸的银粒子的

7、生成，溶剂对纯的银粒子沉淀物的获得起着比较关键的作用。这些亚微米粒子的形成经历了两个阶段：（1）超饱和溶液中纳米主粒子的成核；（2）形成的主粒子聚集成更大的均匀的粒子。（5）我们发展了一种在表面琉基功能化的电极表面有效固定Ru（bpy）32+的新方法。本方法同时运用了溶液自组装和固体表面自组装两种技术，即：先将Ru（bpy）32+和柠檬酸根阴离子保护的金纳米粒子的水溶液按照一定比例混合，得到了Ru（bpy）32+-金纳米粒子聚集体,然后把少量聚集体的悬浮液直接滴在表面琉基功能化的电极表面，从而实现Ru（bpy）32+在电极表面的有效固定。该方法简单易行，制备的电极具有很好的稳定性和电化学发光性

8、能，因而在固态电化学发光检测方面具有很好的应用前景；止匕外，该方法还可用于在固体表面构建Au纳米粒子多层膜。(6)发展了一种通过加热3-曝吩丙二酸(3-thiophenemalonicacid,TA)和H2PtCl6混合水溶液直接制备小的Pt纳米粒子的新方法，并通过对该胶体溶液用Ru(bpy)32+处理，得到了2+Ru(bpy)3-Pt纳米粒子聚集体。通过对在裸电极表面的聚集体进仃俯环电势扫描，使得聚集体中的TA分子发生电化学聚合而在电极表面形成了稳定的聚合物膜；由于该膜有效地避免了聚集体从电极表面脱落，从而我们得到了非常稳定的、具有极好电化学发光性能的膜。本工作不但提供一种方便制备Pt纳米粒

9、子的新途径，而且还发展了一种在任何表面直接加工电化学发光检测器的新方法，在固态电化学发光检测方面具有重要应用价值。(7)通过在室温下直接混合H2PtCl6和Ru(bpy)3cl2水溶液，我们获得了具有新颖形貌的、含有Ru(bpy)32+的微结构。实验结果表明，金属价态、金属种类及反应物摩尔比和浓度对微结构的形貌有重要影响，形成的微结构都具有很好的电化学发光性能。这些微结构给我们提供了一种新的功能材料，将在毛细管电泳或毛细管电泳微芯片的固态电化学发光检测方面有着很好的应用前景。关键词：纳米材料，湿化学，自组装，电化学发光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