Development of an autonomous detector for sensing of nerve agents based on functionalized silicon nanowire field-effect transistors

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Development of an autonomous detector for sensing of nerve agents based on functionalized silicon nanowire

field-effect transistors

Simon Clavaguera, Nicolas Raoul, Alexandre Carella, Michael Delalande, Caroline Celle, Jean-Pierre Simonato

To cite this version:

Simon Clavaguera, Nicolas Raoul, Alexandre Carella, Michael Delalande, Caroline Celle, et al.. Devel- opment of an autonomous detector for sensing of nerve agents based on functionalized silicon nanowire field-effect transistors. Talanta, Elsevier, 2011, 85, pp.2542-2545. �10.1016/j.talanta.2011.08.012�.

�cea-01344114�

Development of an autonomous detector for sensing of nerve agents based on functionalized silicon nanowire field-effect transistors

SimonClavaguera, NicolasRaoul,AlexandreCarella^∗,MichaelDelalande,CarolineCelle, Jean-PierreSimonato^∗

CEAGrenoble/LITEN/DTNM/LCRE,17ruedesMartyrs,38054GrenobleCedex9,France

a r t i c l e i n f o

Articlehistory:

Received27May2011

Receivedinrevisedform2August2011 Accepted6August2011

Available online 12 August 2011

Keywords:

Field-effecttransistor Nerveagent Organophosphorus Sensor

Siliconnanowire Prototype

a b s t r a c t

Theabilitytodetectminutetracesofchemicalwarfareagentsismandatorybothformilitaryforcesand homelandsecurity.Variousdetectorsbasedondifferenttechnologiesareavailablebutstillsufferfrom seriousdrawbackssuchasfalsepositives.Thereisstillaneedforthedevelopmentofinnovativereliable sensors,inparticularfororganophosphorusnerveagentslikeSarin.

Wereporthereinonthefabricationofaportable,battery-operated,microprocessor-basedprototype sensorsystemrelyingonsiliconnanowirefield-effecttransistorsforthedetectionofnerveagents.Afast, supersensitiveandhighlyselectivedetectionoforganophosphorusmoleculesisreported.Theresults showalsohighselectivityincomplexmixturesandoncontaminatedmaterials.

© 2011 Elsevier B.V. All rights reserved.

1. Introduction

The highlethality and the ease of manufacturing Sarin-like moleculesfrominexpensivestartingmaterialsrendernerveagents aweaponofchoiceforterroristattacks[1,2].Consequently,coun- terterrorismactivitieshavebeenstrengthenedoverthepastdecade topreventsuchpotentialthreat.Onegoalistodevelopreliable,sen- sitiveandspecificsystemsforthedetectionoforganophosphorus moleculesinurbanareasandbattlefields.Severaltechnologiesare alreadyusedandsomeothersarebeingdevelopedforthesensing ofnerveagents:IMS[3],GC/MS[4],enzymaticassays[5],carbon- nanotubebaseddevices[6,7],etc.Howeverthecost,thelimited portability,theoperationalcomplexity,thefalsepositivesandthe slowresponsetimemakemostofthesemethodsinadequateforon- sitemonitoringdevices.Asaresult,thereisstillaneedforsensitive, compact,low-cost,andlowconsumptionportabledevicesfornerve agentdetectioninthefieldofdefenceandhomelandsecurity.

Siliconnanowire-basedfield-effecttransistors(NW-FETs)are wellstudiedstructures[8–12]thatgiverisetopowerfulsensors forthedetectionofchemicalspeciesinair[13–16].ForNWsensors operatedasFETs,thesensingmechanismisthefield-gatingeffectof chargedmoleculesonthecarrierconductioninsidetheNW[17,18].

∗Correspondingauthors.

E-mailaddresses:alexandre.carella@cea.fr(A.Carella), jean-pierre.simonato@cea.fr(J.-P.Simonato).

Wereporthereinthedevelopmentandtheappraisalofasuper- sensitiveandfastreactingportablehybriddetectorofnerveagents basedonelectricaltransductionofachemicalreactionoccurringon thesurfaceofafunctionalizedsiliconnanowirefield-effecttransis- tor(SiNW-FET).Thisdevicebearingtheadequatefunctionalityon theSiNW-FET,apowersourceandamicrocontrollerfordatapro- cessingwasfabricatedtoinvestigateitsrelevanceforthedetection ofnerveagentsincomplexenvironments.Theexceptionalperfor- mancesoftheSiNWdevicesenablethedetectionofnerveagent simulantwithhighsensitivityandexcellentselectivity.

2. Materialsandmethods 2.1. Sensitivematerialfabrication

Aseriesofmolecularsensorswasdescribedelsewhereinwhich thereactionofaprimaryalcoholwithanorganophosphoruscom- pound(OP)initiatesanintramolecularcyclizationtogeneratea quaternaryammoniumspecieswhichcanbeidentified(Scheme1) [14,19].Inordertoinvestigatetheinfluenceofthechargegenera- tionontheelectricalpropertiesofaSiNW-FET,ananchoringunit maybeusedtolocalizethemolecularreceptorontothenanowire.

For instance, anethynyl anchoringgroupwas usedto perform covalentgraftingofthemolecularreceptorontheSi–Hsurfaceby hydrosilylation.

Compound1wassynthesizedinfourstepsstartingfromthe Kemp’s triacid with an overall yield of 40% accordingly to the 0039-9140/$–seefrontmatter© 2011 Elsevier B.V. All rights reserved.

doi:10.1016/j.talanta.2011.08.012

Fig.1. (a)Imageofachipbearing36SiNW-FETsand(b)MEBimageofasingleSiNW-FET(70nmthick,200nmwideand2␮mlong).

syntheticprocedurepublishedelsewhere.FTIR,¹Hand¹³CNMR, andmassspectrometryspectrawereinagreementwithliterature data[14].

2.2. Field-effecttransistorfabrication/portablehybriddetector fabrication/sensorarchitecture

The SiNW-FETs were fabricated from p-doped (10¹⁵Batom/cm³) silicon on insulator (SOI) wafers (Fig. 1).

SiNW-FETsof70nmthicknesswithdifferentlengthsandwidths (4␮m×4␮m; 4␮m×1␮m; 2␮m×1␮m and 2␮m×0.2␮m) wereobtainedbye-beamlithographyanddryreactiveionetch- ingsteps.Thethicknessof theSiO₂ gatedielectric was140nm.

Ti/Au(10/100nm)source and draincontacts wereachieved by usinge-beamlithographyandlift-offprocess.TheSidegenerated substratewasusedasbackgateelectrode.

Thesemiconductingpartofthesensorwasfunctionalizedvia formationofacovalentgraftingthroughthermalhydrosilylationof 1ontoHF-pretreatedsubstrateinrefluxingmesitylenefor2h.We chosetodissociatetheelectronicpartofthedevicefromthesens- ingelement.Thusthetransistorchipisconnectedontoapluggable plasticcardbygoldwirebondingforsourceanddrainelectrodes andwithsilverpastedepositedontothebackgateelectrode(see Fig.2).Thenthesensingcardbearingthetransistorcanbecon- nectedtotheelectronicpartofthedevicethroughthreeelectrically activepins.

Thedrain-sourceandgate-sourcevoltages,respectivelyVDSand V_GS,areappliedwhilethedrain-sourcecurrentismeasuredasa functionoftime(Fig.3).

Theprototypecanbedividedintothreemainparts:amicro- controller,a functionalizedSiNW-FETactingasthetransductor, and digital-analog converters with current-to-voltage circuits

N OH R

N R

N O R

P O

R₂ R₁ OPagent

X P O

R₂ R₁ 1

R=

Scheme1.Reactivityofthemolecularreceptor1towardsOPs.Risananchoring groupusedtograftthemoleculeonaspecificsurface.

Fig.2. Pictureofthedevice.Insertshowsthefieldeffecttransistorwirebondedon acardwiththethreeconnectors.

interfacingtheFETwiththemicroprocessor.Theultralow-power mixedsignalmicrocontrollerfromTexasInstrumentswasinstalled ontheprintedcircuitboardequippedwithadigital-to-analogcon- verterandalogarithmicamplifierabletomeasureverylowcurrent overarangeofsixdecades.Thedrain-sourcecurrentIDSisthesignal processedbythemicrocontroller,and thesensor outputispro- portionaltoI_DS.TheboardwasequippedwithaDC/DCconverter (±15V)thatoperatedfroma9Vbattery,andthreesecurityalert elements:aLCDtextdisplay,abuzzerandatwo-colorLED.

2.3. Sensoroperation/testdescription

Asamplingcyclebeginsbyacalibrationstepwhichconsistsin swippingdrain-sourcecurrentversusgatevoltageoftheambipo- lartransistor,inair,ataconstantbiasvoltageVDS=−1V.Oncethe transfercurveisacquired,theminimumvalueoftheoff-current isidentifiedwiththecorrespondinggatevoltage.Thisparticular valueofthegatevoltagecalledV0isthenappliedtomonitorthe drain-sourcecurrentasafunctionoftime.Ithasbeenshownin previousworkthat upon reactionwithOPs the V₀ potentialof

Fig.3.Schemeofthefield-effecttransistorbasedsensor.(1)Highlydopedsilicon backgateelectrode,(2)SiO2dielectric,(3)Sisemiconductingchannel,(4)drain electrode,(5)sourceelectrode,(6)monolayerofgraftedreceptors.

20 15 10 5 0 -5 -10 -15 -20

VGS (V) IDS (A

Before exposure

After DPCP exposure V0 10^-11 10^-10 Detection

Threshold

Fig.4.FunctionalizedSiNW-FET,IDS–VGScurvesatVDS=−1Vbefore(redsolidline) andafterDPCPexposure(blackdottedline).(Forinterpretationofthereferencesto colorinthisfigurelegend,thereaderisreferredtothewebversionofthearticle.)

functionalizedFETisclearlyshiftedtomorepositivegatevoltages withanaveragevariationV₀ of(7.3±3.5)V[14]. Asaconse- quence,thedetectionthresholdistheIDSvaluemeasuredduring thecalibrationprocessforV_GS=[V₀−3V](i.e.−2.0VinFig.4).The alarmistriggeredwhenthedrain-sourcecurrentreachesthepre- determineddetectionthreshold(i.e.∼7×10⁻¹¹at−2.0VinFig.4).

ThesensitiveareaoftheFETisthenfedbyairthatmaycontain analytes.Whentheairholdsorganophosphoruscompoundslike diphenyldichlorophosphate(DPCP),agoodsimulantofSarin,then I_DSmonitoredbythedeviceraises.Ifanincreaseindrain-source currentisdetectedandifI_DSexceedsthepreviouslydetermined thresholdvalue,thentheoperatoriswarnedagainstthepossible presence of organophosphorus agents. The alarm status is dis- playedontheLCDreadoutalongwithablinkingLED,andthebuzzer setoff.Acomputationalalgorithmallowstheuseofalow-power andlow-costmicrocontrollerfordataacquisitionandanalysis.The generaltestingprocedureinthepresentstudywasfirsttoacquire anI_DS–V_GSsweepataconstantbiasvoltage(V_DS=−1V).Then,after stabilizationfor30sinairwhilemonitoringcontinuouslyIDSat constantbiasvoltages(V_DS=−1V;V_GS=V₀),thesensorisexposed toanalytesfor10s.Thesensoroutput,whichisproportionaltoI_DS wasprocessedandanalyzedusingEq.(1),togivetheso-calledsen- sorresponse.I_DS⁰ isthedrainsourcecurrentbeforeexposurewhile I¹⁰_DS^s is thedrain-sourcecurrentaftera 10sexposuretoanalyte vapors.

Sensor response=_IDS⁰ _−I¹⁰_DS^s

I_DS⁰ (1)

3. Resultsanddiscussion 3.1. ExperimentswithOPsimulants

The transfer characteristics of the functionalized SiNW-FET measuredwithanAgilent4155CSemiconductorAnalyzerbefore andafterexposuretovaporsofDPCPisdepictedinFig.4.Thiscurve showsaclearshifttomorepositivegatevoltagesofthetransfer curvewhenthetransistorisexposedtoDPCPvapors.Whensuchan experimentisrealizedwiththeportablehybriddetectortypically inambientairat20^◦Cand45%relativehumidity,asteepincrease

8 N-methylpyrrolidone 430(25^◦C)

9 Tetrahydrofuran 190,000

10 Ethanol 58,000

11 Iso-propanol 43,000

12 Pyridine 24,000

13 Propionicacid 4300(27.6^◦C)

14 Water(100%relativehumidity) N/A 15 Hydrogenperoxide30%inwater N/A 16 Bleach/sodiumhypochlorite5%inwater N/A 17 Dimethylmethylphosphonate(DMMP) 1100(25^◦C)

18 Dieselexhaustgases N/A

19 Bis-dichlorophenylchlorophosphate N/A 20 Diphenylchlorophosphate(DPCP) 0.5–0.8

oftheoutputsignal(i.e.proportionaltodrain-sourcecurrent)is recorded.Itshouldbenotedthatthesensorworksinacumulative way.Indeed,thereactionbetweenthegraftedreceptorsandthe reactivemoleculesisirreversible,thusV₀shiftcanbeaffectedboth bytheconcentrationofanalyteandtimeexposure.Theincreasefor a10sexposuretovaporsofDPCP(500ppb)givesasensorresponse of78accordingtoEq.(1).Ithastobenotedthatwhenexposedto dryairorairwithvariousrelativehumiditycontents(intherange 0–90%),thesignalwasfoundtobeverystable.Wedidnotobserve neitherincreasenordecreaseoftheoutputsignal(Table1).

We also used a solid simulant named bis- dichlorophenylchlorophosphatewhichexhibitsthesamechemical reactivitythanOPsandDPCP.Toourknowledge,thevaporpres- sureof thiscompound hasnever beenreported.Howeverwith regardtoitsknownphysicalproperties(meltingpoint51–56^◦C), itseemsreasonabletoassumethatverylowcontentofmolecules are presentin thegasphase (probablyfew ppbor evenlower, andcertainlymuchlessthanforDPCP).Neverthelessthesensor givesverysatisfactoryresultsandactuallydetectstracesofsuch material(seeFig.5).

3.2. ExperimentswithDMMP

Diphenylchlorophosphate(DPCP)whichisthemainsimulant usedin thisstudy,appearsasa goodmimic forwarfare agents likeSarinorSomansinceithasbothgoodstructuralandchemical reactivity analogies with organophosphorus agents. Dimethyl- methylphosphonate(DMMP)is oftenusedas OPsimulant.This moleculeisclearlyagoodstructuralanalogtoOPsbutitschemical

Fig.5.SensorresponsecalculatedfromEq.(1)fora10sexposureat20^◦Ctoseveral analytes.TheanalytenamesandtheirvaporpressuresarereportedinTable1.

reactivitydoesnotmimicwelltheelectrophilicbehaviourofreal nerveagents(methoxygroupisapoornucleofuge).Moreover,due tothefactthatthismoleculeiswidelyusedasaflameretardant, plasticizer,antistaticagentoradditiveforgasoline,itcancompete withthedetectionofnerveagentsincomplexenvironments.In thepresentstudy,itis remarkablethattheprototypeisableto detectveryquicklyandwithanextremesensitivityDPCP,anddoes notrespondtoastructuralanalogthatdoesnotpresentasimilar reactivitytonerveagentslikeDMMP(Fig.5).

3.3. Testswithinterferents

Fig. 5 shows the sensor response for several analytes that couldinterferewiththesensoroperation.Nosignificanteffectwas observedwhenthedetectorwasexposedtohighconcentrations oforganicsolventsandotherdomesticvolatilecompounds.The selectivityofthesensor wasthus excellenteven withcomplex atmospheressuchasvaporsofperfumes(e.g.HugoMan^®perfume, Faconnable^®perfume,Soupline^®softener)ordieselexhaustgases (entry18).

3.4. Demonstrationinarelevantenvironment

Wepointoutthatthesensorisabletodetectthepresenceof DPCPinvariousenvironments,representativeofrealconditions.No positiveresponsewasobservedwhenthedetectorwasexposedto cottoncloth,paperorsoilparticlespollutedwithsolvents,butthe sensorsetoffalarmwhenexposedtoDPCP-taintedcloths,DPCP- taintedpaperorDPCP-pollutedsoil(1%,w/wDPCPinsand).The sensorwasalsoexposed for10stovariousmixturescomposed ofvaporsoforganicsolventsandattimesDPCP.Thealarmwas triggeredonlywhentheSarinsimulantwaspresent.

4. Conclusion

Inconclusion,thepresentstudydescribesthefabricationofa portable,battery-operated,microprocessor-basedprototypesen- sorsystem based on SiNW-FET for detection of a nerve agent simulants. An extremely rapid, sensitive and highly selective detection of a Sarin-like molecule is reported. Moreover, our resultsshowsthatDPCPcanbedistinguishamongotherrelated

compounds,incomplexmixturesoroncontaminated materials.

Wehavenowdevelopedmoresensitivedevices[18]thatwillbe integratedinthesameprototype,whichshouldleadtoafurther increaseinperformances.Toourknowledge,thisapproachrepre- sentsthefirstfullyintegratedportabledeviceforthedetectionof Sarin-likemoleculesbasedonnanotechnologies.

Acknowledgement

WethankDr.StéphaneLenfantandDr.DominiqueVuillaumefor thefabricationofSiNW-FETandforhelpfuldiscussions.Thiswork wassupportedinpartbytheprojectCAMIGAZANR-10-CSOSG-003.

References

[1] J.A.Romano,B.J.Lukey,H.Salem,ChemicalWarfareAgents:Chemistry,Phar- macology,Toxicology,andTherapeutics,2nded.,CRCPressInc.,BocaRaton, FL,2007.

[2]A.T.Tu,ToxinRev.26(2007)231–274.

[3]M.A.Makinen,O.A. Anttalainen,M.E.T.Sillanpaaa, Anal.Chem.82(2010) 9594–9600.

[4]W.E.Steiner,S.J.Klopsch,W.A.English,B.H.Clowers,H.H.Hill,Anal.Chem.77 (2005)4792–4799.

[5]M.Pohanka,J.Z.Karasova,K.Kuca,J.Pikula,O.Holas,J.Korabecny,J.Cabal, Talanta81(2010)621–624.

[6]K.Cattanach,R.D.Kulkarni,M.Kozlov,S.K.Manohar,Nanotechnology17(2006) 4123–4128.

[7]M.Delalande,S.Clavaguera,M.Toure,A.Carella,S.Lenfant,D.Deresmes,D.

Vuillaume,J.-P.Simonato,Chem.Commun.47(2011)6048–6050.

[8]Y. Cui, Z.Zhong,D. Wang, W.U.Wang, C.M.Lieber,Nano Lett.3(2003) 149–152.

[9]N.S.Ramgir,Y.Yang,M.Zacharias,Small6(2010)1705–1722.

[10] C. Celle,A. Carella,D. Mariolle,N.Chevalier, E.Rouviere, J.P. Simonato, Nanoscale2(2010)677–680.

[11]M.W.Shao,D.D.D.Ma,S.T.Lee,Eur.J.Inorg.Chem.27(2010)4264–4278.

[12]C.M.Lieber,Z.L.Wang,MRSBull.32(2007)99–104.

[13] Y.Engel,R.Elnathan,A.Pevzner,G.Davidi,E.Flaxer,F.Patolsky,Angew.Chem.

Int.Ed.49(2010)6830–6835.

[14]S.Clavaguera,A.Carella,L.Caillier,C.Celle,J.Pecaut,S.Lenfant,D.Vuillaume, J.P.Simonato,Angew.Chem.Int.Ed.49(2010)4063–4066.

[15] M.C. McAlpine, H. Ahmad, D. Wang, J.R. Heath, Nat. Mater. 6 (2007)379.

[16]K.Skucha,Z.Fan,K.Jeon,A.Javey,B.Boser,Sens.ActuatorsB145(2011) 232–238.

[17] Y.Cui,Q.Q.Wei,H.K.Park,C.M.Lieber,Science293(2001)1289–1292.

[18] V.Passi,F.Ravaux,E.Dubois,S.Clavaguera,A.Carella,C.Celle,J.-P.Simonato, L.Silvestri,S.Reggiani,J.-P.Raskin,D.Vuillaume,IEEEElectronDeviceLett.32 (2011)976–978.

[19] T.J.Dale,J.Rebek,J.Am.Chem.Soc.128(2006)4500–4501.