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