環(huán)境工程專(zhuān)業(yè)英語(yǔ) 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(yǔ)從句

英語(yǔ)中的主語(yǔ)從句主要有兩種：一種是主語(yǔ)從句位于主句之前；一種是主語(yǔ)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(duì)于這兩種句型，因具體情況不同，翻譯時(shí)也需有所不同。一般來(lái)說(shuō)，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(lái)自外太空的太空船，還是僅僅是一群飛行的鳥(niǎo)，仍然是個(gè)謎。(順序譯法)。(3)Itseemedinconceivablethatthepilotcouldhavesurvivedthecrash.譯文：駕駛員在飛機(jī)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(yǔ)從句

一般來(lái)說(shuō)，賓語(yǔ)從句包括動(dòng)詞賓語(yǔ)從句和介詞賓語(yǔ)從句兩種。1.動(dòng)詞賓語(yǔ)從句動(dòng)詞賓語(yǔ)從句的翻譯方法與主語(yǔ)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(jìn)行的冶煉試驗(yàn)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(yǔ)從句

一般來(lái)說(shuō)，賓語(yǔ)從句包括動(dòng)詞賓語(yǔ)從句和介詞賓語(yǔ)從句兩種。2.介詞賓語(yǔ)從句介詞后作賓語(yǔ)的句子叫介詞賓語(yǔ)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(shí)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(wèn)題。（綜合譯法）(7)Plasticsaredifferentfromothermaterialsinthattheypossessacombinationofproperties.譯文：塑料與其他材料不同，因?yàn)樗芰暇哂芯C合性能。（轉(zhuǎn)譯為原因狀語(yǔ)從句）Translation

名詞性從句三、表語(yǔ)從句

表語(yǔ)從句較之其他從句更好判斷和識(shí)別，它總是位于系動(dòng)詞之后，對(duì)其主語(yǔ)起到解釋的作用，語(yǔ)序和漢語(yǔ)基本一致。表語(yǔ)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(huì)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(yǔ)從句

名詞性從句在句子中可以作同位語(yǔ)，簡(jiǎn)稱(chēng)為同位語(yǔ)從句，用于進(jìn)一步說(shuō)明前面某一名詞的內(nèi)容。同位語(yǔ)從句與定語(yǔ)從句容易混淆。首先，定語(yǔ)從句中的“that”是關(guān)系代詞，在從句中充當(dāng)主語(yǔ)或賓語(yǔ)等成分，而同位語(yǔ)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(shí)質(zhì)性的意義。其次，定語(yǔ)從句對(duì)其先行詞只起修飾和限定作用，而同位語(yǔ)從句則在內(nèi)容上起到更進(jìn)一步解釋和說(shuō)明先行詞的作用。由于同位語(yǔ)從句和定語(yǔ)從句具有一定的共同點(diǎn)，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(shí)驗(yàn)也沒(méi)有希望獲得毫無(wú)誤差的實(shí)驗(yàn)結(jié)果。（綜合譯法）(4)ThetheorythatdiseasesarecausedbybacteriawasadvancedbyPasteur,aFrenchchemist.譯文：細(xì)菌致病的理論是法國(guó)化學(xué)家巴斯德提出來(lái)的。（同位語(yǔ)轉(zhuǎn)譯為定語(yǔ)）Translation

Exercise

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

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