環(huán)境工程專業(yè)英語 課件 U5L1 Electrochemical Sensors for Environmental Monitoring

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ElectrochemicalSensorsforEnvironmentalMonitoringProfessionalEnglishforEnvironmentalEngineering

Electroanalyticalchemistrycanplayaveryimportantroleintheprotectionofourenvironment.Inparticular,electrochemicalsensorsanddetectorsareveryattractiveforon-sitemonitoringofprioritypollutants,aswellasforaddressingotherenvironmentalneeds.Suchdevicessatisfymanyoftherequirementsforon-siteenvironmentalanalysis.ElectrochemicalSensorsforEnvironmentalMonitoring

Introduction

ElectrochemicalformaldehydedetectorTheyareinherentlysensitiveandselectivetowardselectroactivespecies,fastandaccurate,compact,portableandinexpensive.Suchcapabilitieshavealreadymadeasignificantimpactondecentralizedclinicalanalysis.Yet,despitetheirgreatpotentialforenvironmentalmonitoring,broadapplicationsofelectrochemicalsensorsforpollutioncontrolarestillintheirinfancy.Introduction

ElectrochemicalSensorsforEnvironmentalMonitoring

Severalelectrochemicaldevices,suchaspH-oroxygenelectrodes,havebeenusedroutinelyforyearsinenvironmentalanalysis.Recentadvancesinelectrochemicalsensortechnologywillcertainlyexpandthescopeofthesedevicestowardsawiderangeoforganicandinorganiccontaminantsandwillfacilitatetheirroleinfieldanalysis.Introduction

ElectrochemicalSensorsforEnvironmentalMonitoring

OxygenelectrodespHelectrodesTheseadvancesincludetheintroductionofmodified--orultramicroelectrodes,thedesignofhighlyselectivechemicalorbiologicalrecognitionlayers,ofmoleculardevicesorsensorarrays,anddevelopmentsintheareasofmicrofabrication,computerizedinstrumentationandflowdetectors.Introduction

ElectrochemicalSensorsforEnvironmentalMonitoring

Thepurposeofachemicalsensoristoprovidereal-timereliableinformationaboutthechemicalcompositionofitssurroundingenvironment.Ideally,suchadeviceiscapableofrespondingcontinuouslyandreversiblyanddoesnotperturbthesample.Suchdevicesconsistofatransductionelementcoveredwithabiologicalorchemicalrecognitionlayer.Inthecaseofelectrochemicalsensors,theanalyticalinformationisobtainedfromtheelectricalsignalthatresultsfromtheinteractionofthetargetanalyteandtherecognitionlayer.Principles

ElectrochemicalSensorsforEnvironmentalMonitoring

Differentelectrochemicaldevicescanbeusedforthetaskofenvironmentalmonitoring(dependingonthenatureoftheanalyte,thecharacterofthesamplematrix,andsensitivityorselectivityrequirements).Mostofthesedevicesfallintotwomajorcategories(inaccordancetothenatureoftheelectricalsignal):amperometricandpotentiometric.Principles

ElectrochemicalSensorsforEnvironmentalMonitoring

Amperometricsensorsarebasedonthedetectionofelectroactivespeciesinvolvedinthechemicalorbiologicalrecognitionprocess.Thesignaltransductionprocessisaccomplishedbycontrollingthepotentialoftheworkingelectrodeatafixedvalue(relativetoareferenceelectrode)andmonitoringthecurrentasafunctionoftime.Theappliedpotentialservesasthedrivingforcefortheelectrontransferreactionoftheelectroactivespecies.Principles

ElectrochemicalSensorsforEnvironmentalMonitoring

Theresultingcurrentisadirectmeasureoftherateoftheelectrontransferreaction.Itisthusreflectingtherateoftherecognitionevent,andisproportionaltotheconcentrationofthetargetanalyte.Inpotentiometricsensors,theanalyticalinformationisobtainedbyconvertingtherecognitionprocessintoapotentialsignal,whichisproportional(inalogarithmicfashion)totheconcentration(activity)ofspeciesgeneratedorconsumedintherecognitionevent.Principles

ElectrochemicalSensorsforEnvironmentalMonitoring

Suchdevicesrelyontheuseofionselectiveelectrodesforobtainingthepotentialsignal.Apermselectiveion-conductivemembrane(placedatthetipoftheelectrode)isdesignedtoyieldapotentialsignalthatisprimarilyduetothetargetion.Suchismeasuredunderconditionsofessentiallyzerocurrent.Potentiometricsensorsareveryattractiveforfieldoperationsbecauseoftheirhighselectivity,simplicityandlowcost.Principles

ElectrochemicalSensorsforEnvironmentalMonitoring

Theyarehowever,lesssensitiveandoftenslowerthantheiramperometriccounterparts.Inthepast,potentiometricdeviceshavebeenmorewidelyused,buttheincreasingamountofresearchonamperometricprobesshouldgraduallyshiftthisbalance.Principles

ElectrochemicalSensorsforEnvironmentalMonitoring

Theremarkablespecificityofbiologicalrecognitionprocesseshasledtothedevelopmentofhighlyselectivebiosensingdevices.Electrochemicalbiosensorsholdaleadingpositionamongthebioprobescurrentlyavailableandholdgreatpromiseforthetaskofenvironmentalmonitoring.ElectrochemicalBiosensors

ElectrochemicalSensorsforEnvironmentalMonitoring

Suchdevicesconsistoftwocomponents:abiologicalentitythatrecognizesthetargetanalyteandtheelectrodetransducerthattranslatesthebiorecognitioneventintoausefulelectricalsignal.Agreatvarietyofschemesforimplementingtheelectrochemicalbiosensingapproach,basedondifferentcombinationsofbiocomponentsandelectrodetransducershavebeensuggested.Theserelyontheimmobilizationofenzymes,antibodies,receptorsorwholecellsontoamperometricorpotentiometricelectrodesElectrochemicalBiosensors

ElectrochemicalSensorsforEnvironmentalMonitoring

Chemicallayerscanalsobeusedforimpartingahighdegreeofselectivitytoelectrochemicaltransducers.Whileconventionalamperometricelectrodesservemainlyforcarryingtheelectricalcurrent,powerfulsensingdevicescanbedesignedbyadeliberatemodificationoftheirsurfaces.Basically,themodificationofanelectrodeinvolvesimmobilization(onitssurface)ofreagentsthatchangetheelectrochemicalcharacteristicsofthebaresurface.ChemicallyModifiedElectrodesforEnvironmentalMonitoring

ElectrochemicalSensorsforEnvironmentalMonitoring

Inclusionofreagentswithintheelectrodematrix(e.g.carbonpaste)isanotherattractiveapproachformodifyingelectrodes.Suchmanipulationofthemolecularcompositionoftheelectrodethusallowsonetotailortheresponsetomeetspecificsensingneeds.Thenew“mercury-free”surfacesaddressalsogrowingconcernsassociatedwithfieldapplicationsoftheclassicalmercurydropelectrode.ChemicallyModifiedElectrodesforEnvironmentalMonitoring

ElectrochemicalSensorsforEnvironmentalMonitoring

Themostsensitiveelectroanalyticaltechnique,strippinganalysis,ishighlysuitableforthetaskoffieldmonitoringoftoxicmetals.Theremarkablesensitivityofstrippinganalysisisattributedtoitspreconcentrationstep,inwhichtracemetalsareaccumulatedontotheworkingelectrode.Thisstepisfollowedbythestripping(measurement)step,inwhichthemetalsare“stripped”awayfromtheelectrodeduringanappropriatepotentialscan.Stripping-BasedMetalSensors

ElectrochemicalSensorsforEnvironmentalMonitoring

About30metalscanthusbedeterminedbyusingelectrolytic(reductive)depositionoradsorptiveaccumulationofasuitablecomplexontotheelectrodesurface.Strippingelectrodesthusrepresentauniquetypeofchemicalwheretherecognition(accumulation)andtransduction(stripping)processesaretemporallyresolved.Shortaccumulationtimes(of3-5min)arethussufficientforconvenientdowntothesub-ppblevel,withshorterperiods(1-2min)allowingmeasurementsofppbandsub-ppbconcentrations.Stripping-BasedMetalSensors

ElectrochemicalSensorsforEnvironmentalMonitoring

Thetimeconsumingdeaerationstephasbeeneliminatedbyusingmodernstrippingmodes(e.g.potentiometricorsquare-wavestripping),thatarenotpronetooxygeninterferences.Strippinganalysiscanprovideusefulinformationonthetotalmetalcontent,aswellascharacterizationofitschemicalform(e.g.oxidationstate,labilefraction,etc.).Overlappingpeaks,formationofintermetalliccompoundsandsurfactantadsorptionrepresentthemostcommonproblemsinstrippinganalysis.Stripping-BasedMetalSensors

ElectrochemicalSensorsforEnvironmentalMonitoring

lonselectiveelectrodesofferdirectandselectivedetectionofionicactivitiesinwatersamples.Suchpotentiometricdevicesaresimple,rapid,inexpensiveandcompatiblewithon-lineanalysis.Theinherentselectivityofthesedevicesisattributedtohighlyselectiveinteractionsbetweenthemembranematerialandthetargetion.lonandGasSelectiveElectrodes

ElectrochemicalSensorsforEnvironmentalMonitoring

Dependingonthenatureofthemembranematerialusedtoimpartthedesiredselectivity,ionselectiveelectrodescanbedividedintothreegroups:glass,solid,orliquidelectrodes.Manyionselectiveelectrodesarecommerciallyavailableandroutinelyusedinvariousfields.lonandGasSelectiveElectrodes

ElectrochemicalSensorsforEnvironmentalMonitoring

Electrochemicalsensortechnologyisstilllimitedinscope,andhencecannotsolveallenvironmentalmonitoringneeds.Yet,avastarrayofelectrochemicalsensorshasbeenappliedinrecentyearsformonitoringawiderangeofinorganicandorganicpollutants.Wearecontinuouslywitnessingtheintroductionofnewelectrochemicalsensingdevices,basedonawiderangeofchemicalorbiologicalrecognitionmaterials.Conclusions

ElectrochemicalSensorsforEnvironmentalMonitoring

Inaddition,massproductiontechniques(adaptedfromthemicroelectronicindustry)enablethefabricationofextremelysmallandreproducible,andyetinexpensive(disposable),sensingdevices.Suchdevicesarebeingcoupledwithlightanduser-friendlymicroprocessor-basedinstrumentation.Conclusions

ElectrochemicalSensorsforEnvironmentalMonitoring

Fast-respondingelectrochemicalsensorsarealsobeingadaptedfordetectioninon-linemonitoringorflow-injectionsystems(asneededforcontinuousmonitoringorfieldscreeningapplications).Otheradvancesofselectiveandstablerecognitionelements“smart”sensorsandmoleculardevices,remoteelectrodes,multiparametersensorarraysormicromachiningandnanotechnology,arecertaintohaveamajorimpactonpollutioncontrol.Conclusions

ElectrochemicalSensorsforEnvironmentalMonitoring

Additionaleffortsshouldbegiventothedevelopmentofnewimmobilizationprocedures(thatincreasethestabilityofthebiocomponent),tothedesignofnewelectrocatalysts(thatfacilitatethedetectionofadditionalprioritypollutants),tothereplacementofclassicalmercuryelectrodeswithwell-definedsolidsurfaces,toaddressthefoulinganddegradationofelectrochemicalsensorsduringuse,tothedevelopmentofimmunoassay-basedelectrochemicalsensorsandofremoteelectrodesforunattendedoperations,andintroductionofmulti-sensorsystemsforsimultaneousmonitoringofseveralprioritycontaminants.Conclusions

ElectrochemicalSensorsforEnvironmentalMonitoring

On-goingcommercializationefforts,coupledwithregulatoryacceptance,shouldleadtothetranslationoftheseandfutureresearcheffortsintolargescaleenvironmentalapplication.Conclusions

ElectrochemicalSensorsforEnvironmentalMonitoring

名詞性從句一、主語從句

英語中的主語從句主要有兩種：一種是主語從句位于主句之前；一種是主語從句位于主句之后。由從屬連詞、連接副詞或連接代詞引導(dǎo)的句子一般位于主句之前，而由先行詞“it”引導(dǎo)的特殊句子位于主句之后。對于這兩種句型，因具體情況不同，翻譯時也需有所不同。一般來說，可采用順序譯法、逆序譯法、綜合譯法和分譯譯法。(1)WhetherthatUFOwasaspaceshipfromouterspaceorjustaflockofflyingbirdsstillremainsapuzzle.譯文：不明飛行物是來自外太空的太空船，還是僅僅是一群飛行的鳥，仍然是個謎。(順序譯法)。(3)Itseemedinconceivablethatthepilotcouldhavesurvivedthecrash.譯文：駕駛員在飛機墜毀之后，竟然還能活著，這真是難以想象的事。（逆序譯法）

Translation

名詞性從句二、賓語從句

一般來說，賓語從句包括動詞賓語從句和介詞賓語從句兩種。1.動詞賓語從句動詞賓語從句的翻譯方法與主語從句的翻譯方法大體相同，可采用順序譯法，逆序譯法和綜合譯法三種翻譯方法，例如：

(1)Smeltingexperimentsinthisfurnacedemonstratedthatiswaspossibletocarryoutcompletedesulphurizationofsulphideconcentratesautogenously.譯文：在該爐上進行的冶煉試驗表明，硫化精礦完全脫硫是可行的。（順序譯法）。(3)Heaskedonlythathebeallowedtocontinuehisworkundisturbed.譯文：他唯一的要求是允許他不受干擾地繼續(xù)工作。（綜合譯法）Translation

名詞性從句二、賓語從句

一般來說，賓語從句包括動詞賓語從句和介詞賓語從句兩種。2.介詞賓語從句介詞后作賓語的句子叫介詞賓語從句。這種從句往往用連接代詞“whatwhich/who”或連接副詞“how/when/why/where/whether”等引導(dǎo)。當(dāng)然，有時也可以和連詞“that”連用，但必須是用于介詞“in/except”之后。一般可采用順序譯法、逆序譯法、綜合譯法、分譯譯法、轉(zhuǎn)換譯法。

(6)Thequestionthenarisesofhowthisinertialmasscompareswiththegravitationalmass.譯文：然后就出現(xiàn)了如何比較慣性質(zhì)量和引力質(zhì)量是的問題。（綜合譯法）(7)Plasticsaredifferentfromothermaterialsinthattheypossessacombinationofproperties.譯文：塑料與其他材料不同，因為塑料具有綜合性能。（轉(zhuǎn)譯為原因狀語從句）Translation

名詞性從句三、表語從句

表語從句較之其他從句更好判斷和識別，它總是位于系動詞之后，對其主語起到解釋的作用，語序和漢語基本一致。表語從句一般用順序譯法和逆序譯法。

(1)Oneoftheimportantpropertiesofcopperisthatitconductselectricitybetterthanothermaterials.譯文：銅的重要特性之一是其導(dǎo)電性能好。（順序譯法）(2)Oneoftheimportantpropertiesofplasticisthatitdoesnotrustatall.譯文：不會生銹是塑料的重要特性之一。（逆序譯法）Translation

名詞性從句四、同位語從句

名詞性從句在句子中可以作同位語，簡稱為同位語從句，用于進一步說明前面某一名詞的內(nèi)容。同位語從句與定語從句容易混淆。首先，定語從句中的“that”是關(guān)系代詞，在從句中充當(dāng)主語或賓語等成分，而同位語從句中的“that”則不然，它是連詞，在句子中只是起到連接作用而不具有任何實質(zhì)性的意義。其次，定語從句對其先行詞只起修飾和限定作用，而同位語從句則在內(nèi)容上起到更進一步解釋和說明先行詞的作用。由于同位語從句和定語從句具有一定的共同點，所以在翻譯處理的方法上也大同小異，可采用順序譯法、逆序譯法、綜合譯法等。

(3)Eventhemostpreciselyconductedexperimentsoffernohopethattheresultscanbeobtainedwithoutanyerror.譯文：即便是最精確的實驗也沒有希望獲得毫無誤差的實驗結(jié)果。（綜合譯法）(4)ThetheorythatdiseasesarecausedbybacteriawasadvancedbyPasteur,aFrenchchemist.譯文：細(xì)菌致病的理論是法國化學(xué)家巴斯德提出來的。（同位語轉(zhuǎn)譯為定語）Translation

Exercise

1.Strippingelectrodesthusrepresentauniquetypeofchemicalwheretherecognition(accumulation)andtransduction(stripping)processesaretemporallyresolved.2.Theremarkablesensitivityofstrippinganalysisisattributedtoitspreconcentrationstep,inwhichtracemetalsareaccumulatedontotheworkingelectrode.Translation

學(xué)術(shù)論文的撰寫（八）學(xué)術(shù)論文正文的寫作（