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1、FastElectrochemistryofConductivePolymerNanotubes:Synthesis,Mechanism,andApplicationSEUNGILCHOANDSANGBOKLEE*DepartmentofChemistryandBiochemistry,UniversityofMaryland,CollegePark,Maryland20742RECEIVEDONSEPTEMBER18,2007CONSPECTUSonductivepolymersexhibitseveralinter
2、estingandCimportantproperties,suchasmetallicconductivityandreversibleconvertibilitybetweenredoxstates.Whentheredoxstateshaveverydifferentelectrochemicalandelec-tronicproperties,theirinterconversiongivesrisetochangesinthepolymers’conformations,dopinglevels,conduc
3、tivi-ties,andcolors,usefulattributesiftheyaretobeappliedindisplays,energystoragedevices,actuators,andsensors.Unfortunately,therateofinterconversionisusuallyslow,atbestontheorderafewhundredmilliseconds,becauseoftheslowtransportofcounterionsintothepolymerlayertoba
4、lancecharge.Thisphenomenonisoneofthegreatestobstaclestowardbuildingrapidlyresponsiveelectrochem-icaldevicesfeaturingconductivepolymers.Oneapproachtoenhancingtheswitchingspeedisdecreasingthediffusiondistanceforthecounterionsinthepolymer.Wehavefoundthatnanotubular
5、structuresaregoodcandidatesforrealizingrapidswitchingbetweenredoxstatesbecausethecounterionscanbereadilydopedthroughoutthethinnanotubewalls.Althoughthesynthesisofconductivepolymernanotubescanbeper-formedusingelectrochemicaltemplatesynthesis,thesynthetictechnique
6、sandunderlyingmechanismscontrollingthenano-tubemorphologiesarecurrentlynotwellestablished.WebeginthisAccountbydiscussingthemechanismsforcontrollingthestructuresfromhollownanotubestosolidnano-wires.Theappliedpotential,monomerconcentration,andbaseelectrodeshapeall
7、playimportantrolesindeterminingthenano-tubes’morphologies.Amechanismbasedontheratesofmonomerdiffusionandreactionallowsthesynthesisofnanotubesathighoxidationpotentials;amechanismdictatedbythebase-electrodeshapedominatesatverylowoxidationpotentials.Thestruc-tureso
8、ftheresultingconductivepolymernanotubes,suchasthoseofpoly(3,4-ethylenedioxythiophene)(PEDOT)andpolypyr-role,canbecharacterizedusingscanningelectronmicroscopyandtransm