水热法制备纳米ZnS.docx

水热法制备纳米ZnS.docx

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水热法制备纳米ZnS

HydrothermalPreparationofZnSNanowires

Abstract:

NanowiresofZnSweresynthesisedbyusingasurfactantassistedhydrothermalapproach.Thesynthesisisbasedondecorupositionofdipyridylzincthiocyanatewithcetyltriruethylaruruoniumbromide（CTAB）asasurfactant.ThenanostructurewascharacterizedbySEM,XRDandEDX.HR-TEM.Theexperiruentalresultsindicatethatthereactiontirueandconcentrationofsurfactantplaykeyrolesindeterruiningthefinalruorphologiesofnano-ZnS.AndCTABactsasamolecule-directingteruplateforthegrowthofnanowires.

摘要：

以十六烷基三甲基溴化铵（CTAB）为表面活性剂，利用水热法通过二吡啶硫氰酸锌分解制备了ZnS纳米线，并用SEM、XRD.EDX和HR-TEM等方法对其纳米结构进行了表征。

实验结果表明，反应时间和表面活性剂浓度是决定纳米ZnS最终形貌的关键凶素．CTAB起到了纳米线生长的分子一诱导模板作用。

Nanostructurehasarosetreruendousinterestaruongtheresearchersworkinginallfieldsincludingphysicstobioscience.Frombasicsciencetotechnologistsfortheirimprovedphysicalandchemicalpropertiesandapplicationssuperiortotheirbulkcounterparts.Sincethefirstdiscoveryofcarbonnanotubes.one-dimensional（ID）semiconductormaterialssuchasnanorods.nanowires.nanotubesandnanobelts/nanoribbonshaveattractedextensiveinterestbecauseoftheirfundamentalphysical.chemical,optical,electricalandmagneticproperties,andtheirpotentialapplicationsinnano-scaledevices.ItiswellknownthatIDnanostructurecanplayanimportantrolebothasinterconnectandfunctionalunitsinfabricatingelectronic,optoelectronic.electrocheruicalandelectroruechanicaldeviceswithnanoscaledimension.1Dnanostructurehavebeensynthesizedthroughavarietyofsynthesistechniquesuchastemplate-directedsynthesisc5l,Vaporsolidgrowth,vapor-liquid-solid（VLS）growthm.solu-tion-liquid-solid（SLS）growthcs]etc.Avarietyofmetalc9Lsemiconductingoxidesuo]indifferentIDnanoformshavebeenreportedsofar.

Outofthesematerials.zincsulfide.aII-VIsemiconductor.isoneof'themoststudiedmaterialsforitswiderangeoftechnologicallyimportantproperties.ZincSulfide（ZnS）hasawidebandgapof3.72eVforcubicphasec"and3.77eVfortheatrooruteruperature.Itisalight-eruittingdiodes,injectionlasers.cathoderaytubes,flatpaneldisplaysandIRwindows.ZnSisalsoimportantforphotoluminescence.electroluminescence.etc.Recently,opticalwaveconfiningandlasinghasbeendemonstratedinZnSnanoribbonsU3lInrecentyears,nanocrystallineZnShasattractedmuchattentionbecausepropertiesinnanoformsdiffersignificantlyfromthoseoftheirbulkcounterparts.Therefore.Muchefforthasbeendevotedtocontrolthesize.morphologyandcrystallinityoftheZnSnanocrystalswithaviewtotunetheirphysicalproperties.

Inthisstudy,wepresentarelativelysimpleandeffectiveprocedureforsynthesisofl-DZnSviahydrothermalreactionat2000Cusingadipyridylzincthiocyanatecolloidalsolution,cetyltrimethylammoniumbromide（CTAB）asasurfactant.Theinfluenceofsurfactantandreactiontimeonthemorphologyhasbeeninvestigated.

1Experiment

HydrothermalreactionofZnSnanowirewithsurfactantCTAB

AllreagentswereanalyticalgradeCTAB（0,0.12,0.240r1.44mmoI-L~1）and3mLofmethoxyethanolsolutionofdipyridylzincthiocyanate（0.24mmolL-'）wereputintoTeflonlinedautoclaveof50mLcapacity,andthenwasfilledwithdoubledistilledwaterupto80%ofthetotalvolume.Afterbeingsealed,theautoclavewasheatedt0200OCandmaintainedfor2h.andthencooledtoroomtemperature.Theresultingblacksolidfractionwaswashedwithdeionizedwaterandthenwithabsoluteethanol.Finallytheproductsweredriedundervacuumat400C.

有表面活性剂的硫化锌纳米线的水热反应

实验时把所有的试剂析，不同等级的CTAB和3毫升联吡啶硫氰酸甲氧基乙醇溶液放入盛有50毫升的聚四氟乙烯容器内，然后加入蒸馏水直至占总体积的百分之八十。

之后加热到二XX保持两个小时，接着冷却至室温。

把生成的黑色固体用等离子水冲洗接着再用纯酒精清洗一次，最后把产品放到四十度真空中干燥。

。

1.2Characterization

Highresolutiontransmissionelectronmicroscopy（HRTEM）observationsweredoneonHitachimodesH700A-2apparatusequippedwithanEDAXEDSdetectorwithanacceleratedvoltageof200kV.Highresolutionscanningelectronmicroscopy（HR-SEM）imageswereobtainedbyOPTONCSM-950withanacceleratedvoltageof160kV.UV-VspectrawererecordedonaUnicoUV-2201UV-Visspectrometerwithrueasuredwavelengthrangefrom900nmto200nmandslitof1muandscanspeedof300nm.min-l.X-raydiffraction（XRD）patternswereobtainedonaRigakuD/Max2550XwithCuKceradiation（40kV.200ruA.A=0.154186nm）and20rangeof200-800andscanspeedof0.020.s-'.PLstudywasperformedonHitachiF-2500withslitof1nmandscanspeedof300nm.min-l.

在装有一个200千伏的加速电压的设备的高分辨率的日立H700A-2上进行电子显微检测.,高分辨率扫描显微图像通过OPTONCSM-950用160伏特的加速电压来获得.通过UnicoUV-2201UV-V分光仪波长在九百纳米到二百纳米、缝宽为1微米、扫描速率为300纳米每分钟得到紫外光谱。

X衍射图像铜电子辐射在D/Max2550X衍射机，扫描速率为0.020.s-'.缝宽1nm。

扫描速率为每分钟300纳米在HitachiF-2500上进行试验

2Resultsanddiscussion

2.1EffectoftheconcentrationofCTABonthemorphologyofnano-ZnS

Figs.la-dshowSEMimagesoftheZnSnanostructuresynthesizedwithvariedamountsofCTABsurfactant.TheseiruagesclearlyrevealthatthemorphologyofZnSnanostructurevariessignificantlywiththeamountofCTAB.TheshapeofZnSnanostructurevariesfrorusphericalattheratioofZn:

CTAB=I:

O（Fig.la）tohigh-yieldwireslikeattheratioofZn:

CTAB=1:

6（Fig.ld）

withthereactiontimeof2h.ThesimilarphenomenawereobservedfromUV-VisspectraofZnSnanostructure（Fig.2）.CurveainFig.2showstheabsorptionofZnSnanostructurepre-paredwithoutCTABandthereisapeakatabout337nrucorrespondingtoabandgapof3.68eV.abulkcubicZnSreportedinreference[14lWiththeincreaseofCTAB.theabsorptionpeakshiftsshorter（blue）to330nm（Curveb）,325nm（Curvec）and289nm（Curved）,respectively,whichcorrespondstoabandgapofhexagonalZnS.ThebandgapofbulkhexagonalZnSis3.80eV['4].SOitsuggeststhatthepresenceofCTAB

2.2Effectofreactiontimeonthemorphologyofnano-ZnS

InadditiontotheeffectofCTABconcentration.reactiontimeisanotherimportantfactorthatinfluencestheshapeandsizeofZnSnanostructure.Acomparisonbetwe.entheimagesofZnSnanostuctures,preparedwiththesameCTABconcentrationandwithvarious（0.5and2h）reactiontimes.showsthetime-relatedshapeevolutionprocessofZnSnanostructure.Asmentionedabove.thenanowiresobtainedwithl.44mmol.L-IofCTABwithareactiontirueupt00.5hconsistonlyofafewin-dividualwire-likestructureswithawidthof40nmandalengthof150nruaswellasthesphericallyshapedZnS（60nmindiameter）（Fig.3a）.After2hofsynthesis.theyieldofwire-shapedZnSincreases:

wire-likestructureswithawidthof60nmandale.ngthof2000nmareseen（Fig.3b）.Inallthecasesde.scribed（reactionwithsurfactant）,attheshorterreactiontimedurationrespectively（0.5h）weseeonlythebeginningoftheevolutionofZnSfromcubicshapedwire-likemorphologicalasserublies.whileafter2hofsynthesis,theZnSnanowiresyieldincreaseswithincreasingsizesofZnScrystal.Fromthetime-relatedshape-evolutionprocess,itseemsthatincrasingthere.actiondurationt02h,usingvariousCTABconcentrationsleadstoahighyieldofwire-likestructures.

2.3FurthercharacterizationofZnSnanostructure

Fig.4a,bandcaretheXRDpatternsofthesynthesizedZnSnanostucturepreparedwithoutCTABandinpresenceof0.24mruol-L-'.1.44rumol.L-10fCTABwiththereactiontimeof2h.respectively.AlltheofZnSnanostucturepreparedwithoutCTAB（a）andinpresenceof'0.24mmolL-I（b）,（c）of'CTABwiththereactiontimeof'2h,respectivelvdiffractionpeaksinFig4acanbeindexedtocubicZnS（PDFCardNo.5-566）andinFig.4b,ccanbeindexedtohexagonalphaseZnS（PDFCardNo.12-688）,whichisingoodagreementwiththeresultsobtainedfromUVVisspectra（Fig.2）.NoimpuritiessuchasZn.NioorintermediaryphasezincsulfidesaredetectedintheXRDpatternsofFig.4bandc.ButthecharacteristicdiffractionpeaksinFig.4bislessobviousthanthoseinFig.4c,whichindicatesthattheconcentrationofCTAB

dlfectsthecrystalintegrality.

TypicalEDXpattemofas-obtainedZnSsampleisshowninFig.5.TheresultsshowthattheZnSnanowiresarecoruposedofZnandSandtheratioofZntoSis1.08:

l,inagreementwiththeexpectedvalue.EnergylkeVInFig.6,HR-TEMimageofZnSshowsthattheyarecomposedofabout7nmZnSnanocrvstalsasseruFig.6TEMimageof'ZnSnanowireandHR-TEMimageoftheZnSnanowire（inset）preparedusing1.44mmolL-lof'CTABwiththereactiontimeof'2hbliesbecauseneck-likeconnectionsaruongtheadjacentnanocrystalsareclearlyobserved.Thelatticeplanesof'ZnSnanocrystalsareclearlyvisibleintheinsetofFig.6.Fig.7illustratesthephotoluminescence（PL）spectrumofZnSnanowireswithanexcitationwavelengthof335nm.Theappearanceofanarroweruissionpeakatabout452muisweak.Abroadbandatabout520nmisalsoobserved.whichcanbedividedintotwopeaksat523muand533nm,repectively,deruonstratingthatthesenonawiresruayhavepotentialapplicationsinop-

toelectronicdevices.

Thenucleationandgrowthconditionsofnano-ZnSwereexaruinedwithoutandwithvariousconcentrationsofcationicsurfactantCTAB.ThisgrowthprocesscouldberelatedtotheinteractionoforientedsurfactantchainsandformattedZnSnanowires.Uniformandorderedchainstructure（16carbonatoms）iseasilyadsorbedonthesurfaceofZnScolloidalparticles.

WhenthesurfaceofthecolloidalZnSadsorbsCTAB.theactivitiesofcolloidgreatlydecreaseandthegrowthrateofthecolloidinsomecertaindirectionwillbeconfined.TheadditionofmoreCTABinthecolloidalsolutionruodifiesthegrowthkineticsofthegrowingcolloids.whichfinallyleadstoanisotropicgrowthofnanocrystals.Investigationshavebeendonewithdifferentconcentratio