专业英语写作作业.docx

专业英语写作作业.docx

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专业英语写作作业

Non-enzymaticDetectionofGlucosebasedonDendrite-likegoldnanostructures

Abstract

Dendrite-likegoldnanostructures（DGNs）weredirectlyelectrodepositedontothesurfaceofaglassycarbonelectrode（GCE）viathepotentiostaticmethodwithoutanytemplates,surfactants,orstabilizers.Theeffectsofthedepositiontime,potentialandtheconcentrationofprecursorsolutionontheevolutionofthenanostructureandontheelectrocatalyticactivityoftheDGNsweresystematicallyinvestigatedusingscanningelectronmicroscopy（SEM）,transmissionelectronmicroscopy（TEM）andelectrochemicalmethodsincludingcyclicvoltammetry,linearvoltammetryandchronoamperometry.TheresultsconfirmedthatDGNshavegoodelectrocatalyticactivitytowardstheelectro-oxidationofglucoseinaneutralphosphatebuffersolution（PBS,pH7.4）.Anon-enzymaticglucosesensorfabricatedwiththeDGNsasanelectrocatalystshowedaquickresponse（lessthan2s）,alowdetectionlimit（0.05mM）,awideandvaluablelinearrange（0.1-25mM）,ahighsensitivity（190.7μAcm-2mM-1）andgoodrepeatabilityandstability.Inaddition,thecommonlyinterferingspecies,suchasascorbicacid（AA）,uricacid（UA）,and4-acetaminophen（AP）,didnotcauseobviousinterferencebecauseoftheuseofalowdetectionpotential（0.15Vvs.Ag/AgCl）.Thisworkdemonstratesasimpleandaneffectivesensingplatformforthenon-enzymaticdetectionofglucose.

Keywords：

Dendrite-likegoldnanostructures;Electrodeposition;Glassycarbonelectrode;Glucoseoxidation;Non-enzymaticglucosesensor

1.Introduction

Glucosesensorshavebeenextensivelystudiedoverthepasttwentyyearsbecauseoftheirapplicationsinthepreventionandtreatmentofdiabetesmellitus,fromwhichmillionsofpeoplesuffer[1].Therefore,therehasbeenanincreasingdemandforthedevelopmentofinexpensiveglucosesensorsthathavehighselectivity,sensitivity,andgoodstability[2,3].Moststudiesarebasedonglucoseoxidase（GOx）boundtoelectrodetransducers,inwhichhydrogenperoxideisproducedfromtheoxidationofglucoseandcanbeamperometricallydetectedtobestoichiometricallyrelatedtoglucoselevels.Althoughenzymaticdetectionshowsahighsensitivityandagreatselectivity,thesensitivitytotheenvironmentandtheinstabilityaretheprimarydifficultiestoovercome.Inaddition,theoxidationofH2O2usuallyrequiresarelativelyhighpositivepotential（usuallyover+0.6Vvs.SCE）[4,5].Manyotherelectroactivespeciesthatcommonlycoexistinbiologicalfluids,suchasascorbicacid（AA）,uricacid（UA）,and4-acetamidophenol（AP）,canalsobeoxidizedatsuchhighpotentials,andtheirelectrochemicalsignalsthusseverelyaffecttheselectivityofthebiosensors[6].

Toovercometheseproblems,manyattemptshavebeendevotedtodevelopnon-enzymaticglucosebiosensorusingnoblemetalnanomaterialstosubstitutetheenzymeaselectrocatalyst.Themajorityofthesesensorsrelyonthecurrentresponseofglucoseoxidationdirectlyatthesurfaceofthenanomaterialsmodifiedelectrode.Thusthenon-enzymaticbiosensorexhibitedmuchhigherstabilityforalongperiodandresistanceabilitytotheenvironmentalfactorsthantheglucosebiosensorusingenzyme[7,8].Todate,alargeamountofmetalsandoxidenanoparticles,suchasPd[1,6],Pt[9-13],Au[2,14-19],CuxO[3,20]andCeO2[21],havebeenimplementedinelectrochemicalcatalyticreactions.Amongthesematerials,non-enzymaticbiosensorsusingCunanomaterialsaselectrocatalystforglucosesensing,analkalinesolutionenvironmentisusuallyrequired.AlthoughPtnanomaterialsshowhighcatalyticpropertiesinneutralbufferstoglucosemolecules,theirintrinsicactivitiesarenormallysuppressedbecausetheyareeasilypoisonedbyintermediatesandproductsgeneratedduringtheexperimentalprocesses[22].Auasapotentialcandidatehasattractedmuchattentionfortheuniquepropertiesofitsnanostructures,suchasgoodconductivity,usefulelectrocatalyticactivity,andbiocompatibility[23,24].Moreover,nanosizedgoldstructuresexhibitsuperiorpoisonresistivitytowardtheelectro-oxidationofglucoseduetotheirlargesurface-to-volumeratioandthepresenceofhighlyactivebindingsitesonthesurfaceoftheparticles[25].Therefore,usingAunanostructurematerialasacatalystwouldbeexpectedtomeettheneedofnon-enzymaticdetectionofglucose.

Manymethodshavebeenusedtoobtaingoldnanostructures,suchasself-assemblywithpolymers[26-28],seed-mediatedgrowth[29-32]andthermal-drivenattachment[33].However,theapplicationofsurfactants,bridgingagentsandorganicsolutionsinthereactionsmightreducetheelectrocatalyticactivityofAunanoparticlesduetoblockingoftheactivesites.SochallengesstillexistinthepreparationofAunanostructureswithacleansurfaceandahighcatalyticability.Ontheotherhand,dendrite-likegoldnanostructures（DGNs）havereceivedconsiderableinterestsfortheirlargerspecificsurfaceareaandtheextensiveapplicationsinsuperhydrophobicproperty,diversecatalyticfields,suchaselectro-oxidationofethanolandglucose[19,24].Itiswellknownthatelectrodeswithincreasedspecificsurfaceareascanprovideimprovedperformanceforkineticallycontrolledreactions,suchasglucoseoxidation.However,theinfluenceofthespecificsurfaceareaondiffusion-controlledreactionsistiny,forexample,mostinterference（AAandUA）oxidationontheelectrodes.Thus,fabricatingelectrodeswithhighsurfaceareasisapromisingmethodtoincreasetheelectrochemicalresponseofglucosewhilelimittheimpactofinterferencesreactions[12,22].Thismeansthatdendrite-likegoldnanostructureswithlargersurfaceareawillleadtoahighersensitivityforglucosedetection,aswellasabetterselectivity.However,toourknowledge,asystematicstudyonthenon-enzymaticdetectionofglucoseusingDGNshasnotbeenreported.

Inthiswork,thedendrite-likegoldnanostructureswasfabricatedbyapotentiostaticmethodwhichisverysimpleandclean.TheobtainedDGNswithextremelyincreasedspecificsurfaceareadisplayedahighcatalyticactivityintheoxidationofglucose.Moreover,thenormalinterferencesthatcoexistinphysiologicalconditions,suchasAA,UA,andAP,canbeeffectivelyavoidedduetothehighspecificsurfaceareaandthelowerdetectionpotential.Theinfluenceoftheelectrodepositingconditions,suchasthedepositiontime,depositionpotentialandtheconcentrationofprecursorsolution,wasalsoinvestigatedtofindouttheimpactfactorsonthemorphologyofthegoldnanostructuresandthecatalyticperformanceintheoxidationofglucose.ItisinterestinglyfoundthatthecatalystmaterialofDGNsgeneratedundertheoptimizedelectrodepositingconditionsshowsarapidresponseandhighsensitivitytowardsthecatalyticoxidationofglucose.

2.ExperimentalSection

2.1.Materials

HAuCl4·3H2OwaspurchasedfromAldrichCo.,Ltd.Ascorbicacid（AA）,uricacid（UA）,4-acetaminophen（AP）,glucose,absolutealcohol,Na2HPO4·12H2O,NaH2PO4·3H2O,concentratedsulfuricacid（H2SO4）andKClwereobtainedfromtheSinopharmChemicalRegentCo.Ltd.Allthechemicalswereofanalyticalgrade.Aphosphatebuffersolution（PBS,0.1M,pH7.4）waspreparedfromNa2HPO4·12H2OandNaH2PO4·3H2O.Solutionsofglucose,AA,UAandAPwerepreparedusingPBS.Rod-shapedglassycarbonelectrodes（GCE,3mmindiameter）wereobtainedfromtheGaossUnionInstrumentCompany,Wuhan,China,andbulkgoldelectrode（2.0mmindiameter）wasorderedfromBAS.Co.Ltd.Bothoftheelectrodeswerepolishedsequentiallywithslurriesof0.3and0.05μmaluminatocreateamirrorfinish,andthentheywashedsequentiallyinpurewater,ethanolandpurewaterwhilesonicatingfor1minineach.Afterwashing,theelectrodeswerethoroughlyrinsedwithpurewateranddriedwithnitrogengas.Inalltheprocedures,thepurewaterweusedwaspreparedwithaKertoneUltrapureWaterSystemP60-CY（KertoneWaterTreatmentCo.Ltd,resistivity>18MΩ.cm）.Additionally,alltheexperimentalmeasurementswerecarriedoutatroomtemperature.

2.2.Apparatuses

ThesizeandmorphologyoftheAunanostructuresdepositedontheglassycarbonelectrodesurfaceswerecharacterizedwithscanningelectronmicroscopy（SEM）andtransmissionelectronmicroscopy（TEM;FEITECNAI20,USA）.Alltheelectrochemicalmeasurementswerecarriedoutwitha550electrochemicalworkstation（GaossUnionInstrumentCompany,Wuhan,China）inaconventionalthree-electrodecell.ForSEMcharacterization,weusedaremovableglassycarbonelectrodethatcouldbedirectlyexaminedunderthescanningelectronmicroscope.ForTEMcharacterization,thedendrite-likegoldnanostructureswerefirstscrapedfromtheGCelectrodeandthendispersedinpurewaterwithsonicationfor1hour.Subsequently,10μLofthesuspensionwascastedonacoppermesh,anddriedunderambientconditions,andfinallytransferredintothemicroscopeforobservation.

2.3.ProceduresforpreparingtheDGN-modifiedGCelectrode

DirectelectrodepositionoftheDGNsontotheGCelectrodesurfacewascarriedoutviaapotentiostaticmethod[19,34,35].First,theprecursorsolutionwaspreparedbydissolvingapredeterminedamountofHAuCl4·3H2Ointoa0.1MKClsolution.Then,thetreatedGCelectrodewasimmersedintotheelectrolytesolutionandusedastheworkingelectrode.AcleanplatinumwireandaAg/AgClelectrodewereusedasthecounterandreferenceelectrodes,respectively.Finally,theelectrodepositionwasperformedunderpotentiostaticmode.Theresultingelectrodeswerethoroughlyrinsedseveraltimeswithpurewater.Inthiswork,wesystematicallyinvestigatedtheeffectsoftheelect