基于单片机的氧气检测仪英文原版参考文献word版文档格式.docx
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基于单片机的氧气检测仪英文原版参考文献word版文档格式.docx
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stabilisedopticaloxygensensor
AlbertoJ.Palmaa,JavierL´
opez-Gonz´
alezb,LuisJ.Asensioa,MariaDoloresFern´
andez-Ramosb,LuisFerminCapit´
an-Vallveyb,~
aDepartmentofElectronicsandComputerTechnology,CampusFuentenueva,FacultyofSciences,
UniversityofGranada,E-18071Granada,Spain
bSolidPhaseSpectrometryResearchGroup,DepartmentofAnalyticalChemistry,CampusFuentenueva,
FacultyofSciences,UniversityofGranada,E-18071Granada,Spain
Received26January2006;
receivedinrevisedform13March2006;
accepted14March2006
Availableonline5June2006
Abstract
Anovelmeasurementsystemcomprisedofaportableelectronicinstrumentwithanopto-chemicalsensorforatmosphericoxygensensingispresented.Opticalsensorsbasedonluminescencequenchinghavebeenthoroughlyinvestigatedinthesearchforsufficientsensitivityandhighstability.ThedyeplatinumoctaethylporphyrincompleximmobilisedinapolystyrenemembranewasselectedasanoxygenprobethatwasstabilisedwiththeheterocyclicamineDABCO,achievinginthiswayameandriftof0.01%oxygenconcentrationperday.Theportableinstrumentisbasedonamicrocontroller.Itsmainfeaturesare:
asingleopticalsensorchannel,lackofopticalfilters,fullydigitalsignalprocessing,autonomousoperationwithcomputercommunicationcapabilityforreprogramminganddatasavingandlowpowerconsumption.Theuseofadigitaloutputphotodetectormakesitpossibletoavoidanalogueprocessingwiththeconsequentcircuitrysavingandbetternoiseimmunity.Themeasuredparameterinthetransductionprocessisquitesimilartotheluminescencelifetime.Thetypicalmeasurementrangeisfrom0to30%oxygenandtheresponsetimeisbelow30sforfullrangeswing.Typicalinstrumentcharacteristicsaretemperatureeffectcorrection,lowdriftandanaccuracyof0.5%inoxygenconcentrationforthecollectivecalibrationcurve.Betteraccuracycanbeobtainedwithindividualsensorcalibration.Dimensionsandweightare110mm×
66mm×
28mmand95g(withoutbattery),respectively.Poweringitwithastandard9VPP3batteryformorethan10daysofoperationispossible.
©
2006ElsevierB.V.Allrightsreserved.
Keywords:
Opticalchemicalsensor;
Oxygendetermination;
Phosphorescence;
Luminescencequenching;
Portableinstrument;
Microcontroller
1.Introduction
Thedevelopmentofportableanalyticalinstrumentationisaninterestinginterdisciplinaryareaofresearchwhichbringsanalyticalchemistsandelectronicengineerstogether.Tomanufacturelow-costeasy-to-useinstrumentsforuseindifferentfieldssuchastheenvironment,worksafety,defenceandhealth,muchmoretechnologicaldevelopmentmustbedone.Thiswilltakeanalyticalinstrumentationoutoftherealmofdedicatedacademicorresearchlaboratoriesandofferittonontrainedusersandconsumers.Greatresultshavebeenobtained
~Correspondingauthor.
E-mailaddress:
lcapitan@ugr.es(L.F.Capit´
an-Vallvey).
inthisregardinsomeareassuchashealthcareandprocesscontrol.
Inenvironmentalsensing,inparticular,thedevelopmentofhand-heldbattery-operatedmeasurementsystemsforthedeterminationofoxygenisafieldofresearchwithwideapplications.Inthisarea,opticalchemicalsensorsareanattractivealternativetothemoreestablishedelectrochemicalsensors[1].Mostopticalchemicaloxygensensorsarebasedonthequenchingoftheluminescenceofanoxygen-sensitivedyebymolecularoxygen.Extensiveworkhasbeendoneinthisarea,whereavarietyofluminescentdyeshavebeenincorporatedintoagaspermeablemembraneanddifferentmeasurementprocedureshavebeenreported[2–6].Inthepast,instrumentationforsignalprocessingsuchasluminescencewasgenerallyfairlyelaborated,bulkyandcostlyandthereforeunsuitableforportable
630A.J.Palmaetal./SensorsandActuatorsB121(2007)629–638
2.1.Reagents
Platinumoctaethylporphyrin(PtOEP)wasobtainedfromPorphyrinProductsInc.(Logan,UT,USA),1,4-diazabicyclo[2.2.2]octane98%(DABCO),tetrahydrofuran(THF),polystyrene(PS,averageMW280,000,Tg:
100~C,GPCgrade)andhighmolecularweightpoly(vinylchloride)(PVC)werepurchasedfromSigma–AldrichQu´
ımicaS.A.(Madrid,Spain).SiliconeElastosilN-10wasobtainedfromGeneseePolymerCorp.(MI,USA).Thefluopolymerpoly(isobutylmethacrylateco-tetrafluoropropylmethacrylate)wassynthesisedandcharacterisedbyusaccordingtoAmaoetal.[12].SheetsofMylar-typepolyester(Goodfellow,Cambridge,UK)wereusedasasupportformembranes.ThegasesO2andN2usedwereofahighpurity(>
99%)andweresuppliedingascylindersbyAirLiquidS.A.(Madrid,Spain).
2.2.Membranepreparation
Themembraneswereproducedonapolyestersubstrateusingaspin-coatingtechnique.(i)Polystyrenemembranes:
mixturesforthepreparationofoxygen-sensitivemembranesweretypicallymadebydissolving0.5mgofPtOEPin1mLofasolutionof5%(w/w)ofPSinfreshlydistilledTHFinaglassvial.Themembraneswerecastbyplacing30~Lofthecocktailonathicktransparentpolyestersheetoftheappropriatesizeusingahomemadespin-coater[22]rotatingat180rpm.Afterspinningfor2min,themembranewasremovedfromthespincoateranddriedinadryerwithsaturatedTHFatmospherefor24hatroomtemperature.Thesensing6mmdiametercircularfilmthatwasobtainedishomogeneous,transparentandpinkincolourwithacalculatedthicknessofabout4.5~mandanapproximatePtOEPconcentrationof14.4mM.(ii)Polystyrene–DABCOmembranes:
inthiscase,thecocktailcontains12mgofDABCO(25%DABCO)inadditiontoothercomponentsindicatedabove.Thefilmobtainedusingthesametechniqueis10mmindiameterand14~minthickness.(iii)PVCmembranes:
themembraneswerecastusing50~Lofacocktailpreparedbydissolving0.5mgofPtOEPand100mgofPVCin1mLofTHFinaglassvial.Thefilmobtainedis6mmindiameterand5~mthick.(iv)Siliconemembranes:
thesemembraneswerepreparedwith30~Lofacocktailcontaining1gofsiliconeElastosilN-10in1mLoftoluene.ToimpregnatethemembranewithPtOEP,thetechniquedescribedbyBaconandDemas[23]wasused.Themembranewasimmersedina1000mgL-1solutionofPtOEPinCH2Cl2for10min.Itwasthenremoved,rinsedwithCH2Cl2andair-dried.Thefilmobtainedwas11mmindiameterand7~mthick.Allthepreparedmembraneswerestoredinthedarkuntilusetoavoidphotodegradation.
2.3.Measurementsystem
2.3.1.Portableelectronicinstrument
Ourmeasurementsystemconsistsofasensingmembranedirectlyattachedtoaportableelectronicinstrumentwitha
systems.However,thelasttwodecadeshavewitnessedsignifi-2.Experimental
cantdevelopmentofreliable,smallandlow-costsemiconductordevicesforexcitingandcollectingopticalsignals,suchashighintensitylightemittingdiodes(LED),laserdiodesandsemiconductorphotodetectors.Thistechnologyhasbeencontinuouslyincludedinnewportableinstrumentdesigns,particularlyforgassensing.
Inthequenchingprocess,emittedluminescenceintensityandluminescencedecaytimeareaffectedbyoxygenconcentration.Fromthepointofviewofphotostabilityandimmunitytostrayopticalsignalinterference,decaytimemeasurementseemstobemoreadvantageousthanintensity[4,7].However,someresultshavebeenreportedincludingaportableinstrumentfordissolvedoxygendetectionbasedonintensitymeasurement[2,8].Thedecaytimeoftheluminescencecanbedeterminedwithdifferentmethods:
(i)directmeasurementwithhighspeed,largeandexpensiveinstrumentation[9]and(ii)phasemodulationtechniques[2,10].Inthelatterapproach,dedicatedsignalprocessingelectronicshasmadeaninstrumentthatincludesdualopticalchannels,circuitryfortheacsignalandseveralcontrolcircuitsforphaseshiftcorrectionandavoidingamplifiersaturation[7].
Oneofthetypicalproblemsofquenching-basedsensorsforoxygen,especiallyforintensity-basedsensors,istheusuallowphotochemicalstabilityofluminophoreswhichreducesthelifeofthesensorandrequiresfrequentrecalibration.Differentsolutionshavebeendevisedtosolvetheproblem:
(1)modifyingexistingluminophores[11];
(2)modifyingthepolymermatrices[12];
(3)usingrelativesignalsobtainedindifferentways:
(a)fromscatteredexcitationradiation[13],(b)fromtheluminophoreitselfthroughaluminescencebandinsensitivetoO2[14,15]orbyusingaluminophorethatsimultaneouslyshowsphosphorescencequenchablebyO2andfluorescenceinsensitivetoO2[16],(c)fromasecondO2-insensitivefluorophorewithsimilardecayratessuchasindicatordyes[17,18];
(4)introducingstabiliseradditives,mainlytertiaryamines,tomembranestoremovethereactivesingletoxygengivenofffromthequenchingprocessofluminophoreluminescence[19,20].
Inthisreport,aportableinstrumentforatmosphericoxygenconcentrationmeasurementhasbeendeveloped[21].Ourgoalswereareliable,simple,low-costprototypeincludingahighstabilisedsensingmembraneandthelatestsemiconductoroptoelectronicdevices.Wereportonaneasy-to-usemeasurementsystemwithhighopticalandelectricalinterferenceimmunity,extremelysimplesignalprocessingcircuitry,lowpowerconsumptionandenoughaccuracyforinsituatmosphericoxygendetermination.Wehavedesignedaninstrumenttoovercomesomeofthedrawbacksofpreviousportabledesigns,basedonsimpleelectronicsandaonesignalchannelwithoutanyreferencechannel.Oneofthemainadvantagesofourdes
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