Field Portable Electrochemical Field Portable Electrochemical Sensors for Uranium and Other Sensors for Uranium and Other

Species in Aqueous SamplesSpecies in Aqueous Samples

Dale Russell, Ph.D.Dale Russell, Ph.D.Department of ChemistryDepartment of Chemistry

Boise State UniversityBoise State University

Handheld Portable Sensors Handheld Portable Sensors Developed in our LabDeveloped in our Lab•• Uranium, plutonium, thorium Uranium, plutonium, thorium

(actinides)(actinides)•• Other heavy metals, e.g. Other heavy metals, e.g.

mercury, cesiummercury, cesium•• VOCsVOCs: benzene, toluene: benzene, toluene•• BiologicalsBiologicals: catechols and : catechols and

catechol aminescatechol amines•• Two operating modes:Two operating modes:

–– FET typeFET type–– Potential sweep type (cyclic Potential sweep type (cyclic

voltammetryvoltammetry))

SourceGateDrain

Uranium Sensor Project GoalsUranium Sensor Project GoalsA Paradigm Case A Paradigm Case

•• Detection of Actinide species in waterDetection of Actinide species in water•• Detection in the fieldDetection in the field

–– Hand heldHand held–– Autonomous operation w/ data loggingAutonomous operation w/ data logging

•• NonNon--Proliferation treaty compliance: clandestine Proliferation treaty compliance: clandestine deploymentdeployment

•• Highly selective to minimize false signalsHighly selective to minimize false signals•• Analytical parameters: real time signal, robust, Analytical parameters: real time signal, robust,

dynamic range, low detection limit, selective, dynamic range, low detection limit, selective, sensitivesensitive

Remediation Applications for Remediation Applications for Uranium Detection in WaterUranium Detection in Water

•• Detection in waste Detection in waste holding tanks, containersholding tanks, containers

•• Process streamsProcess streams•• At a distance from the At a distance from the

source: runsource: run--offoff•• Detection in saturated soilDetection in saturated soil•• Monitoring fate and Monitoring fate and

transport in surface and transport in surface and ground waters.ground waters.

Existing Methods of Uranium Existing Methods of Uranium AnalysisAnalysis

•• ICPICP--AAS, xAAS, x--ray, and fluorescence ray, and fluorescence spectroscopiesspectroscopies

•• Portable laser ablation method (PNNL)Portable laser ablation method (PNNL)–– Field portable by heavy vehicleField portable by heavy vehicle–– Requires solid sampleRequires solid sample

•• Stripping analysis incl. MEMS device Stripping analysis incl. MEMS device (Wang, ASU)(Wang, ASU)

•• Radiochemical methodsRadiochemical methods

Capability Shortfall in Actinide Capability Shortfall in Actinide Detection in Aqueous MediaDetection in Aqueous Media

•• These isotopes are alphaThese isotopes are alpha--emitters: emitters: 209209Ac through Ac through 225225Ac; Ac; 226226Th Th →→ 230230Th; Th; 222222U U →→ 238238U (except U (except 237237U); U); most most PuPu..

•• Alpha radiation is low energy; low penetrationAlpha radiation is low energy; low penetration•• Water quenches alpha signal; alpha emitters are not Water quenches alpha signal; alpha emitters are not

detected in water by their radiochemical signatures.detected in water by their radiochemical signatures.•• Other current methods rely on labOther current methods rely on lab--based or large, based or large,

truck “portable” methodstruck “portable” methods•• True handTrue hand--held or clandestine methods do not existheld or clandestine methods do not exist•• Only ICPOnly ICP--AA and stripping methods detect U directly AA and stripping methods detect U directly

in the aqueous medium.in the aqueous medium.•• Other methods require sample deOther methods require sample de--solvationsolvation..

Sensor ConceptSensor Concept

•• Metal substrate coated with Metal substrate coated with sensing polymersensing polymer

•• Polymer is derivatizedPolymer is derivatized–– Chelating ring for metalsChelating ring for metals–– MIPsMIPs for polyatomic speciesfor polyatomic species

•• Target analyte binds to Target analyte binds to polymer polymer

•• Electronic or electrochemical Electronic or electrochemical property of polymer or target property of polymer or target analyte changes.analyte changes.

•• Changes are concentration Changes are concentration dependentdependent

S S** n

-

-

-

-

-

OH

OH OH

OH

OH

SO3

SO3SO3

SO3

SO3

SO3

O

-

SS

Advantages of this SensorAdvantages of this Sensor

•• Treat uranium and other actinides like any other Treat uranium and other actinides like any other redoxredox active metalactive metal

•• Detection based on Detection based on redoxredox and and complexationcomplexationchemistries, not radiochemical signature. chemistries, not radiochemical signature.

•• Direct chemicalDirect chemical--toto--electronic signal transduction.electronic signal transduction.•• No moving parts.No moving parts.•• Small sensor, simple, robust, inexpensive; handSmall sensor, simple, robust, inexpensive; hand--

held or autonomous operation is possible.held or autonomous operation is possible.•• Both our Both our chemchem--FET and CV sensors are much FET and CV sensors are much

less complex than less complex than MEMsMEMs stripping method.stripping method.

A Thiophene-Based Chelating Polymer•• Selective receptor sites for target analyteSelective receptor sites for target analyte•• Electrochemically polymerizedElectrochemically polymerized

–– Film thickness can be varied over wide rangeFilm thickness can be varied over wide range•• NonNon--hygroscopic: Thiophene does not hydrogenhygroscopic: Thiophene does not hydrogen--bondbond

–– Polymer does not swell or change morphology in Polymer does not swell or change morphology in aqueous or humid environmentsaqueous or humid environments

–– Polymer does not dePolymer does not de--laminate in waterlaminate in water•• SemiconductingSemiconducting polymerpolymer

–– Direct chemicalDirect chemical--toto--electronic transduction of signalelectronic transduction of signal–– Does not require photon or particle detectionDoes not require photon or particle detection

•• Mechanically and chemically robustMechanically and chemically robust–– Inert to strong mineral acids, bases and most organic Inert to strong mineral acids, bases and most organic

solventssolvents–– Has to be burned off of platinum substrate!Has to be burned off of platinum substrate!

Thiophene PolymerizationThiophene Polymerization

Bithiophene

Advantages of Chelating PolymerAdvantages of Chelating Polymer

•• Polymer is conductive: direct chemicalPolymer is conductive: direct chemical--toto--electronic signal transductionelectronic signal transduction

•• Binding site is covalently attachedBinding site is covalently attached–– Does not readily diffuse awayDoes not readily diffuse away–– Signal is stable with timeSignal is stable with time

•• Binding site selectivity minimizes chemical Binding site selectivity minimizes chemical interferences.interferences.

•• Analyte is Analyte is preconcentratedpreconcentrated on surfaceon surface–– Lower detection limitsLower detection limits–– Greater sensitivityGreater sensitivity

“CPDT-ol”

The Polymer Coated Electrode The Polymer Coated Electrode SurfaceSurface

Chelating ring shown free, and with a uranyl ion bound

Kf with UO22+ = 1026

Electrode Surface

Bulk polymer, poly(2,2’-bithiophene)

S S** n

-

-

-

-

-

OH

OH OH

OH

OH

SO3

SO3SO3

SO3

SO3

SO3

O

-

SS

Pressed Wire Electrode Blank for Pressed Wire Electrode Blank for CV Mode SensorsCV Mode Sensors

Polymer Coated Electrodes for CV Polymer Coated Electrodes for CV Mode SensorsMode Sensors

Cyclic Cyclic VoltammogramVoltammogram of UOof UO222+2+

Response of Chelating Uranium SensorResponse of Chelating Uranium Sensor

-2.00E-04

-1.00E-04

0.00E+00

1.00E-04

2.00E-04

3.00E-04

4.00E-04

-9.50E-01-7.50E-01-5.50E-01-3.50E-01-1.50E-015.00E-022.50E-01

Potential, volts vs. SRE

Cur

rent

, Am

ps

red = Uranium solution, Blue = Blank solution

Response of Uranium Sensor with Response of Uranium Sensor with varying concentration of UOvarying concentration of UO22

2+2+

y = 0.0001Ln(x) - 0.0014R2 = 0.8775

-2.500E-03

-2.000E-03

-1.500E-03

-1.000E-03

-5.000E-04

0.000E+000 200 400 600 800 1000

Uranyl Concentration (ppb)

Cur

rent

@ -0

.5 V

(am

ps/c

m2)

Current Response as Function of ConcentrationCurrent Response as Function of Concentration

y = 0.0002x - 0.0014R2 = 0.8775

-2.500E-03

-2.000E-03

-1.500E-03

-1.000E-03

-5.000E-04

0.000E+00-1.5 -1 -0.5 0 0.5 1 1.5 2 2.5 3 3.5

log([UO22+]) (ppb)

Cur

rent

@ -0

.5 V

(am

ps/c

m2)

Thorium Reduction Current vs. Thorium Reduction Current vs. ConcentrationConcentration

y = 0.0684x - 6.7186R2 = 0.9757

-6.8

-6.75

-6.7

-6.65

-6.6

-6.55-1.5 -1 -0.5 0 0.5 1 1.5 2

log Concentration (log ppb)

curr

ent,

mA

50 ppb ThO2+with 50 ppb UO2

2+ and H20 Baseline

-0.08

-0.06

-0.04

-0.02

0

0.02

0.04

0.06

0.08

0.1

-0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6

E (Volts)

I (A

mps

/cm

^2)

Uranium(VI)reduction

Thorium(IV)oxidation

Actinide Sensor Detection LimitsActinide Sensor Detection Limits

By direct measurement of standardsBy direct measurement of standards

Uranium detection limit = 0.1 ppbUranium detection limit = 0.1 ppbThorium detection limit = 0.1 ppbThorium detection limit = 0.1 ppb

By 3By 3σσ calculation of noise analysiscalculation of noise analysis

Detection limit on the order of 0.01 ppbDetection limit on the order of 0.01 ppb

Plutonium DetectionPlutonium DetectionField test at DOEField test at DOE--NV test siteNV test site

Overlay Electrode 5

-200.000

-100.000

0.000

100.000

200.000

300.000

400.000

500.000

-1.500 -1.000 -0.500 0.000 0.500 1.000 1.500

mV

uA

MIX_5MIX_5BBLANK_5

Uranium(VI)reduction

Plutonium(IV)oxidation

A Demonstrated Field Portable SystemA Demonstrated Field Portable SystemPotentiostaticPotentiostatic Mode of OperationMode of Operation

33--Electrode Uranium Sensor TipElectrode Uranium Sensor TipWith Sliding Protective WindowWith Sliding Protective Window

A Field Effect TransistorA Field Effect Transistor

• An optical micrograph showing the gate, source, and drain on a pMOSFETdevice.

• The Scale is L/W 20µm/220µm

• An optical micrograph showing the gate, source, and drain on a pMOSFET device which we attempted to electro-deposit our polymer.

• The Scale is L/W 20mm/220mm

Source

Gate

Drain

Courtesy of W.B. Knowlton, Ph.D. Dept of Electrical and Computer Engr. BSU

A Field Effect TransistorA Field Effect Transistor

Courtesy of W.B. Knowlton, Ph.D. Dept of Electrical and Computer Engr. BSU

NanoliterNanoliter Deposition TechniqueDeposition Technique(Patent Pending)(Patent Pending)

•• 400 400 nLnL droplet on gatedroplet on gate•• Polymer coats only surfaces in electrical Polymer coats only surfaces in electrical

contact with microprobe.contact with microprobe.•• No masking or photolithography required.No masking or photolithography required.•• Different sensing polymers could be Different sensing polymers could be

applied to different devices on same waferapplied to different devices on same wafer•• Quick, easily automated.Quick, easily automated.•• Low cost, minimal waste, ecoLow cost, minimal waste, eco--friendly friendly

ElectrodepositionElectrodeposition of Uranium of Uranium Sensing PolymerSensing Polymer

Tungsten tips in contact with test pad on FET device

This gate is 20µ by 80µ

Use of nL cell concept

Courtesy of W.B. Knowlton, Ph.D. Dept of Electrical and Computer Engr. BSU

Micrograph of Coated FET SensorMicrograph of Coated FET Sensor

20 µM by 80µM gate metal

Image Taken on IR-microscope

Courtesy of W.B. Knowlton, Ph.D. Dept of Electrical and Computer Engr. BSU

FTIR of Calix[6]arene on FET gateFTIR of Calix[6]arene on FET gate

FET Response: IFET Response: IDD vs. Vvs. VDD CurvesCurves

0.0 0.5 1.0 1.5 2.0 2.5 3.00.0

1.0x10-5

2.0x10-5

3.0x10-5

4.0x10-5

5.0x10-5

6.0x10-5

7.0x10-5

8.0x10-5

9.0x10-5

1.0x10-4

1.1x10-4

|Imax| @ 3V = 93.82 uA

|Imax| @ 3V = 84.52 uA

PreEchem PostEchem PostAcetate

RIT wafer sliced a, tox=70nm PMOS

|I Dra

in| (

A)

|VDrain| (V)

Pre & Post Electrochemical Deposition #7 and Post Uranyl Acetate Solution 1 hr. Soaking

|Imax| @ 3V = 99.19 uA

Boise State UniversityElectrical and Computer Engineering Dpt.Dr. Bill Knowlton [Dorian Kiri]Echem7-IV-Comparison-Die12

Courtesy of W.B. Knowlton,Ph.DDept of Electrical and Computer Engr. BSU

Cone Penetrometer

Push probe for shallow geologic subsurface

Power supplyData handling andData transmission units

Both FET and potentiostaticmode sensors in housing

Courtesy of Molly Gribb, Ph.D. Dept. Civil Engr. Boise State Univ

Possible Sensing Array ScenarioPossible Sensing Array Scenario

Courtesy of Dr. Joe Hartman, Dept. Electrical and Computer Engr., BSU

Breadboard Breadboard PotentiostatPotentiostat

Designed byA.V. GopinathMS thesis

Features of the Features of the Breadboard Breadboard PotentiostatPotentiostat

•• Remote activation pulse initiates data cycleRemote activation pulse initiates data cycle•• Rugged, solid state experimental controlRugged, solid state experimental control•• Data smoothing and other signal processingData smoothing and other signal processing•• Peak detection and baseline correctionPeak detection and baseline correction•• Analytical current computationAnalytical current computation•• Data compression to minimize transmission Data compression to minimize transmission

power requirementpower requirement•• Interface to data transmission system.Interface to data transmission system.

Effect of 3-Thiophenemethanol on Soil Micro-organisms

0

50

100

150

200

250

300

350

0 0.1 0.2 0.3 0.4 0.5 0.6

% 3-th io p h en em eth an o l (vo l/vo l)

Ave

rage

Num

ber o

f Col

onie

s

Sensors for Polyatomic Species:Sensors for Polyatomic Species:Molecularly Imprinted Polymers: Molecularly Imprinted Polymers: MIPsMIPs

•• Target analyte attached to monomer by Target analyte attached to monomer by reversible reaction: “reversible reaction: “templatedtemplated monomer”monomer”

•• TemplatedTemplated monomer copolymerized with simple monomer copolymerized with simple monomer, e.g. CPDTmonomer, e.g. CPDT

•• Template molecules removed from bulk polymer Template molecules removed from bulk polymer by reversing the binding reactionby reversing the binding reaction

•• Vacancies left behind are complementary in Vacancies left behind are complementary in geometry and electrostatics to the analytegeometry and electrostatics to the analyte

•• Surface will reSurface will re--bind the bind the templatingtemplating molecule molecule •• Selectivity of the vacancies can be “tuned”Selectivity of the vacancies can be “tuned”

Figure 3.

OH HO

Bulk Polymer

O

O

OO

S

S

O

O

O

OElectrochemicalPolymerization

Bulk Polymer

Saponification

OH HO

Bulk Polymer

IntroduceBenzene

1

Representation of MIP PreparationFor Benzene/Toluene/Catechol Sensor

With CPDT

CV response of Benzene SensorCV response of Benzene Sensor

Benzene Sensor Calibration DataBenzene Sensor Calibration Data

1

10

100

1000

y = 7E-06Ln(x) + 4E-05R2 = 0.9964

0.00E+00

1.00E-05

2.00E-05

3.00E-05

4.00E-05

5.00E-05

6.00E-05

7.00E-05

8.00E-05

9.00E-05

1.00E-04

0 200 400 600 800 1000 1200

S S

O H

A sC lC l

C lA s O

S S

O H

A s

N M e2

N M e 2M e 2 NA s O

S S

C l

A s OOHO

O N a+

N a+

A s OOHO

OC P D T

C P D T

A rse n ic M IP re a c tio n s :

1 .

+ C P D T 3

C P D T (a lco h o l) A rse n ic ( III) ch lo r id e

+

C P D T (a lco h o l) T r is (d im e th y la m in o )a rs in e

C P D T3

2 .

3 .

+ 7 H 2O

C P D T (ch lo r id e ) S o d iu m a rse n a te d ib a s ic h e p ta h yd ra te

Synthesis of MIPs for Arsenic Species

Current Response of Arsenate Current Response of Arsenate Sensor with Varying ConcentrationSensor with Varying Concentration

0.0001

0.75 1.00 1.25 1.500

0.0002

0.0003

0.0004

E (Volts)

I (A

mps

/cm

2 )

1.0 mM

0.5 mM

0.1 mM

10 µM

5 µM

Response of Arsenic MIP SensorResponse of Arsenic MIP Sensor

Calibration Curve for Arsenate Binding

y = 5.2216E-05x + 1.7724E-04R2 = 9.7441E-01

0

0.00002

0.00004

0.00006

0.00008

0.0001

0.00012

0.00014

0.00016

0.00018

0.0002

-2.500E+00 -2.000E+00 -1.500E+00 -1.000E+00 -5.000E-01 0.000E+00

log [Arsenate] (mM)

Cur

rent

max

(Am

ps/c

m2 )

Summary and ConclusionsSummary and Conclusions

•• Selective, field portable sensors have been Selective, field portable sensors have been demonstrated with rapid sub ppbdemonstrated with rapid sub ppb--detection detection

•• Detection in water is shownDetection in water is shown•• Wide dynamic ranges and good selectivity for target Wide dynamic ranges and good selectivity for target

analytesanalytes•• Field portable system demonstratedField portable system demonstrated•• FET and CV modes of operationFET and CV modes of operation

–– FET gives total change in gate potential, e.g. all FET gives total change in gate potential, e.g. all actinidesactinides

–– CV differentiates species based on CV differentiates species based on redoxredox potentialpotential•• More optimization and characterization is neededMore optimization and characterization is needed

Acknowledgements: PeopleAcknowledgements: People

•• UndergraduatesUndergraduates–– Brian Brian CawrseCawrse–– Noah Noah MinskoffMinskoff–– Taylor DixonTaylor Dixon–– Dorian Dorian KiriKiri–– Brian StokesBrian Stokes

•• GraduatesGraduates–– Jonathan Jonathan ScaggsScaggs–– Ryan MeyerRyan Meyer–– AshwiniAshwini VittalVittal GopinathGopinath–– Lisa WarnerLisa Warner

•• Post DocsPost Docs–– Dr. Michael HillDr. Michael Hill

•• ColleaguesColleaguesFrom BSUFrom BSU–– Dr. William Knowlton, EEDr. William Knowlton, EE–– Dr. Susan Burkett, EEDr. Susan Burkett, EE–– Dr. Molly Dr. Molly GribbGribb, CE, CE–– Dr. Joe Hartman, EEDr. Joe Hartman, EEOtherOther–– Dr. Harold Dr. Harold AcklerAckler, EE, , EE,

SUNYSUNY--BinghamtonBinghamton–– Dr. Richard Dr. Richard VenedamVenedam, ,

DOEDOE--NV Test SiteNV Test Site

Acknowledgements: OrganizationsAcknowledgements: Organizations

•• United States Department of Energy United States Department of Energy (DOE NN(DOE NN--URI)URI)

–– This presentation was prepared with the support of the US This presentation was prepared with the support of the US Department of Energy (DOE) award number # DEDepartment of Energy (DOE) award number # DE--FG07FG07--01ID14223. However any opinions, findings, conclusions or 01ID14223. However any opinions, findings, conclusions or recommendations expressed herein are those of the authors and recommendations expressed herein are those of the authors and do not necessarily reflect the views of DOE. do not necessarily reflect the views of DOE.

•• Inland Northwest Research Alliance (INRA)Inland Northwest Research Alliance (INRA)•• DOEDOE--NNSA (with SUNYNNSA (with SUNY--Binghamton)Binghamton)•• US EPAUS EPA