2014-11微波诱导化学化学反应

(三）微波诱导合成法Microwave-assistedsynthesis1.微波简介2.微波与无机化学合成微波的定义微波是频率在0.3~300GHz，即波长在100~0.1cm范围内的电磁波。HzcmJ/mol电磁波频率波长能量粒子运动10201018101610141012101010810-1010-810-610-410-2110210111091071051031010-1g射线X射线真空紫外紫外可见红外远红外微波无线电波核内重排内层电子跃迁外层电子跃迁分子振动分子转动偶极子转向极化界面极化离子跳跃弛豫微波的波长在0.1cm-100cm之间,因而只能激发分子的转动能级跃迁物质对微波的吸收分子的运动包括分子平动、转动、核的振动及电子的运动。分子的总能量E总可表示为式中的Ee、Ev、Er、E分别代表电子能、振动能、转动能和平动能，除平动能之外，前三项都是量子化的，叫分子的内部运动能。分子能态的跃迁会吸收或发射一定的能量，表现为一定频率v光子的吸收或发射，它们之间的关系是大家熟悉的玻尔频率条件：evrtEEEEE总Evhcv亦称波数。升温速率(T-T0)/t=0.566·10-10·e2fE2/rCp微波加热原理介质微波加热主要靠：偶极子转向极化；界面极化实际介质微波有效损耗：eeff＝ed+eMW+eed:偶极损耗；eMW：界面损耗；e：电导损耗介质的复介电常数Dielectricconstant：e＝e1－ie2e1介电常数实部；e2：介电常数虚部f:微波频率；E:电场强度；r：介质密度；Cp：介质比热微波加热原理E.T.Thostenson,T.-W.Chou,Composites,PartA30(1999)1005PowerAbsorbedperUnitVolumeDielectricLossFactor,e2TransparentRespectiveReflectingQuartzAluminaThermoplasticsThermosetsWaterElectrolytesSiliconAluminumSteelLiquidResins微波反应发生器microwavefurnacemicrowavefurnace磁控管的组成permatron['pə:mətrɔn]波导的实图waveguidetube波导器件就是用来完成微波传送、相互连接、耦合以及改向等传输磁控管是微波的发生装置,磁控管阴极发射的电子受电场加速并随速度增大而受到增大的正交磁场的洛仑兹力作用，那些具备足够能量的电子才能以曲线路径达到加有交变高频电压的阳极，这些达到阳极的电子将其所获得的能量全部交给高频场，并维持高频场振荡，持续向外发射微波能量。微波与无机化学合成•早在1967年，N.H.Williams就报道了用微波加快某些化学反应的实验研究结果•1986年加拿大的RaymondJ.Gigure等人发现用微波辐射4-氰基苯氧离子与氰苄SN2亲核取代反应可以使反应速率提高1240倍，并且产率也有不同程度的提高。人们才开始重视用微波控制化学反应。由于微波具有坷物质高效．ApplicationsofMicrowaveonMaterialsSynthesis•1)Oxides(Semiconductors)orNitride•2)Nobalmetals•3)硫化物sulfide和硒化物selenide•4)Carbonnanotube•5)纳米复合物材料Nanocomposites•6)OthersMicrowave-assitedSynthesisofAl-DopedZnONanoneedlesthroughUseofaSeedLayer3)Topreparethesubstrate,a10nmthickTifilmasanadhesionlayerwasdepositedona(100)Siwaferbyrfsputteringinavacuumchamber.A40nmZnfilmwasdepositedontopoftheTilayer.Theresultingsubstratewastransferredintothesolutionandthesubstrate-containingsolutionwasirradiatedbyatemperature-controlledmicrowavesynthesissystem(2.45GHz),ExperimentalSection1)ToobtainthesolutioncontainingZn2+andAl3+withthemolarratioof6:1,zincacetatedihydrate(Zn(CH3COO)2·2H2O,99%)andaluminumchloride(AlCl3,99.99%)wereusedassourcesofzincandaluminumcationsprecursors,respectively.2)Ammonia-water(28.0～30.0wt)wasusedtoprovidehydroxideanions.A100mLtransparentaqueoussolutioncontainingzincacetatedihydrate(0.264g),aluminumchloride(0.0269g)andammonia-water(5mL)wasmadeatroomtemperature(solutionA,pH11.2).4)Afterirradiation,thesubstratewasremovedtakenandthesolutionwasfilteredthroughapolycarbonatemembranefilterwithaporediameterof100nm.5)Theresiduepowderwaswashedseveraltimeswithdeionized(DI)water,andthendriedinanovenat60Cfor12h.ThesubstratewaswashedbyultrasonicationinDIwaterfor10min,afterwhichitwasdriedinanovenat60Cfor12h.SEMimagesofanAl-dopedZnOnanoneedlearraysynthesizedinexperimentA(Zn2+/Al3+molarratioof6:1intheprecursorsolution,pH11.2):(a)topview;(b)obliqueview(45°tilt);(c)TEMimageofanAl-dopedZnOnanoneedle;lowerinsetin(c),SAEDpattern;upperinsetin(c),HRTEMimage.TheHRTEMimagewasobtainedatthecenterofthecirclein(c).95Cfor40min.highlyoriented1DZnOcrystalswithsharpneedlelikestructures.ZnOcrystalswithsharptipshavebeenreportedtobesuitableforthefieldemittercathodeapplications.anaveragelengthof~1.3μm,asharptipofdiameter~10nm.highlycrystalline,Microwave-AssistedShape-ControlledBulkSynthesisofNobleNanocrystalsandTheirCatalyticProperties2)NobalmetalsThemetalnanostructureshavebeenthefocusofintensiveresearchinthepastseveraldecadesduetotheirpotentialapplicationsinfabricatingelectronic,optical,optoelectronic,andcatalyticpropertiestailoredbycontrollingtheirsize,shape,composition,andcrystallinity.Bulkandshape-controlledsynthesisofgold(Au)nanostructureswithvariousshapessuchasprisms,cubes,andhexagonsisdescribedthatoccursviamicrowave-assistedspontaneousreductionofnoblemetalsaltsusinganaqueoussolutionofR-D-glucose['glu:kəus]葡萄糖,sucrose['sju:krəus]蔗糖,,andmaltose['mɔ:ltəus]麦芽糖.Theexpeditiousreactioncanbeappliedtothegenerationofnanospheresofsilver(Ag),palladium(Pd),andplatinum(Pt).TEMimagesofAunanostructuressynthesized(lowconcentrationofsugar)usingmicrowaveirradiationwith(a)sucrose,蔗糖(b)R-D-glucose,葡萄糖or(c,d)maltose.麦芽糖Theinsetsshowcorrespondingelectrondiffractionpatterns.Inatypicalexperiment,anaqueoussolutionofHAuCl4(5mL,0.01N)wasplacedina20mLglassvesselandthenmixedwith300mgofR-D-glucose.Thereactionmixturewasexposedtohigh-intensitymicrowaveirradiation(1000W,PanasonicMWovenequippedfor30-45s.prismscubeshexagonsMicrowaveSynthesisofCdSeandCdTeNanocrystalsExperimentalSectionSolutionsofCdSA(Cadmiumstearate)andTOPSewerepreparedbydispersingCdSA(1.0mmol,679.36mg)into20mLofanalkaneofchoicebysonication,whilea1MsolutionofTOPSewaspreparedunderargonusingSepowder(0.01mol)dissolvedin10mLofTOP.Thereactionmixturewasaddedtoa10mLreactionvesselunderambientconditionsconsistingofa1:5molarratioofcadmiumtoseleniumstocksolutionswithHAD(hexadecylamine十六烷基胺)addedinanequimolarratiotoTOP.TOPTri-n-octylphosphine分子结构Thereactionmixturewasheatedinthemicrowavecavitytoatemperatureof240Cduringa30srampperiodatapowerof300W.Themixturewasthenallowedtoreactfor30sat240Candimmediatelycooledtoroomtemperature(1min)usi