2013-Anti-fouling PEDOT-PSS Modification on Glassy Carbon Electrodes for Continuous_2

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660 X. Yang et al. / Sensorsand ActuatorsB 177 (2013) 659667

have been applied since the 1970s by the US Air Force [9]. Over

several decades, 3 wt% TCP has been added into commercial jet

engine oils, such as Mobil Jet Oil [10]. TCP could be mixed with the

breathable air entering the airliner cabin during engine oil leakage

[11]. Although the most toxic ortho-isomer of TCP is intentionally

excluded from these fluids [12], alternatively used meta- and

para-isomers can have a potentially severe effect on human health

mainly through inhalation of aerosols and dermal adsorption.

The most commonly used methods for detecting TCP include:

gas chromatography and mass spectrometry GCMS [13], highperformance liquid chromatography (HPLC) [14] or thin layer

chromatography (TLC) [15]. Gas chromatography measure-

ment can be based on flame photometric detector (GC/FPD),

nitrogenphosphorus sensitive detector (GC/NPD) [16]. Although

they are able to detect TCP below ppm level and with high selectiv-

ity, these devices have several drawbacks, such as large size, high

cost, complexity, and a need for highly trained operators, which

make their use on aircraft impractical. Alternatively, electrochemi-

cal sensors have the advantages oflow price, highsensitivity, small

size, ease of operation, and rapid response. A portable real-time

electrochemical sensor with linear response for ppb level ofTCP

in gas has been recently reported by our group [17,18]. Since TCP

itself is electrochemically inactive, it was converted to electro-

active cresol for detection. However, the sensor system suffered

from electrode fouling which limited its repetitive usage in long

term applications. A long lasting electrode is needed for on-site

continuous monitoring, so electrode surfaces must be modified to

minimize or eliminate fouling.

Electrode fouling is a common problem during electrochem-

ical analysis of phenolic compounds, such as cresol, and causes

decay in signal response during repetitive measurements [1927].

The fouling is caused by the formation ofa passive polymeric film

on the electrode surface [23,25,28,29]. Upon anodic oxidation of

cresol, phenoxy radicals form, which then couple to form dimers

or oligomers, and finally, a polymeric film deposits on electrode

surface [30]. This polymeric film is tough, thermally stable, and

so chemically inert that little oxidation or hydrolysis will occur in

either acidic or basic media [26]. The films are characterized by

low permeability [31] and strong adhesion to the electrode, whichblocks the surface, and yields electrode fouling [1922,24]. Various

surface treatments and modifications have been used to reduce or

even avoid electrode fouling by preventing polymeric substrates

from absorbing onto the surface of electrode [32,33]. For instance,

a special compound called sodium 3,5-dibromo-4-nitroso benzene

sulfonate (DBNBS) wasused as an anti-foulingagent against the for-

mationofthecresolpolymericfilm[33]. TheDBNBSmoleculereacts

with the oxidized radical ofcresol to form a compound which does

not adhere to the surface ofthe electrode and consequently pre-

ventsthe fouling effect. However, thisapproachis difficult to realize

in practical applications. Overall, the DBNBS should be present in

the buffer solution in stoichiometric concentration with the ana-

lyte of interest, which makes its application for real world samples

problematic.

Having advantages ofhigh electronic conductivity and porosity[34], conducting polymers have attracted considerable interests in

recent years. Modification ofconductive polymer for preventing

electrode fouling has been reported by many researchers [3538].

Poly(3,4-ethylenedioxythiophene) (PEDOT) is one of the widely

used conductive polymers. Patra and Munichandraiah [34], Heras

et al. [39], and Lupu et al. [40] applied PEDOT on electrodes

through electropolymerization for detection of phenolic com-

pounds. The surfactant poly(sodium-4-styrenesulfonate) (NaPSS)

was additionally used during PEDOT electropolymerization to

avoid the problems of[41]: (1) the low solubility of thiophene

structures in water, (2) the oxidation potentials higher than that of

water, and (3) and the water-catalyzed formation of thienyl cation

radicals which can activate concomitant reactions and prevent the

formation of the main polymer [42]. Moreover, the hydrophobic

hydrocarbon residues ofPSS exhibit strongaffinityfor PEDOT, while

the hydrophilic sulphonic groups are oriented toward or even pro-

trude into the solution and may hence induce poor adhesion of

the fouling polymeric film [39,43]. NaPSS also induces the forma-

tionof a permeable and less compact polymer network, and yields

high (ionic) conductivity andpermeability to thefouling polymeric

film. This makes the permeation ofphenolic compounds through

the film and oxidation inside possible, ensuring electroneutrality[39,43]. In the present work, PEDOT:PSS has been used to mod-

ify the commonly used glassy carbon electrode [44,45] to develop

a sensor for continuous monitoring of TCP in gas and has been

investigated.

2. Materials and methods

2.1. Reagents, solutions, and instruments

All aqueous solutions were prepared using de-ionized

Milli-Q water (18m cm). 3,4-Ethylenedioxythiophene (EDOT)

(SigmaAldrich, MO), poly(sodium-4-styrenesulfonate) (NaPSS)

(SigmaAldrich, MO, MW70,000), and lithium perchlorate

(LiClO4) (SigmaAldrich, MO) were used for electro-synthesis of

PEDOT:PSS [39]. The stock 20mM tri-p-cresyl phosphate (p-TCP)

(SigmaAldrich, MO) solution was prepared in methanol (BDH-

VWR) and diluted to obtain TCP samples with concentrations of

interest. All TCP samples were converted to cresol with the aid of

alkaline catalyst. Alkaline catalyst was made from NaOH (Fisher,

NJ) and neutral aluminum oxide (Al2O3) (SigmaAldrich, MO) and

packed in Pipet filter tips (USA Scientific, Inc., 20L leveled filter

tips). p-Cresol (Acros Organics, NJ, 99+%) was dissolved in 0.2M

Na2HPO4/0.2 M KH2PO4/10m M NaCl buffer (0.4 M phosphate

buffer,pH = 6.67). Na2HPO4, KH2PO4, and NaCl were obtained from

SigmaAldrich, MO.

2.2. Electrodes and electrochemical sensor

All amperometric experiments were performed with CH 93Instruments (CH1910B) Bi-Potentiostat. A desktop computer was

used to collect the data. Flow injection analysis (FIA) was carried

out using a unicell electrode set (BASi, IN) and a switch injec-

tion unit (Valco Instruments Co. Inc.) with a 50Lsample loading

loop. The flow rate was maintained at 20mL/min by using a single

syringe pump (KD Scientific, MA). The unicell electrode set con-

sists of one glassy carbon working electrode cell (2mm ), one

electrode set including the stainless steel counter electrode and

Ag/AgCl reference electrode, and one circular gasket (BASi, IN). A

coating solution was applied on the Ag/AgCl reference electrode

surface before detection as per instruction from the company. The

working electrode was polished with alumina powder (BUEHLER,

IL, 1, 0.3, and 0.05m in order). 10mM NaCl was contained in all

solutions to maintain the potential ofreference electrode. 0.64 V

vs. Ag/AgCl/10mM NaCl was applied in amperometry. In batchmode, a glassy carbon electrode (3mm ), Pt counter electrode,

and Ag/AgCl/3M KCl reference electrode (BASi, IN) were used.

2.3. Electropolymerization of PEDOT:PSS onglassy carbon

electrode

The electropolymerization ofmonomer of EDOT was performed

under amperometric conditions in aqueous solution. The solution

contained 5 mM EDOT (0.7108g/L), 0.1M NaPSS (20.62g/L), and

0.1M LiClO4 (10.64 g/L). The unicell glassy carbon electrode was

polished with alumina as mentionedin Section 2.2, rinsedand soni-

cated with de-ionized water in an ultrasonic bath for 5 min, flushed


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X. Yang et al. / Sensors and Actuators B 177 (2013) 659667 661

Fig. 1. Schematicrepresentativeof TCPsamplingsystem. TCPwas heated to 230 C inoil bathand gasified along withN 2 bubbling, and entered thealkalinecatalyst column

set insidean automatic TCP conversion box. In theelectronicallycontrolled TCPconversion box, as shown in thedottedsquarein above figure, TCPwas hydrolyzed for later

detection. The control of the automatic TCPconversion box is described in Ref. [17].

with ethanol and water, and dried with N2 gas. 0.5mC of charge

was applied on the glassy carbon electrode with 2mm diameter

in order to obtain the thickness ofinterest ofelectropolymeriza-

tion layer, unlessotherwisestated. The potential was maintainedat

0.95Vvs.Ag/AgCl/3MKCl. Thecolorofelectrodesurfaceturnedyel-lowafter modification. For comparison, different amount ofcharges

have been applied including 0.3, 1, 1.3, 2, 4, and 20mC on the same

electrode.

2.4. Automatic sampling system forhydrolysis of TCP samples

and TCP in engine oils

Since p-TCP has a very low saturated vapor pressure at room

temperature (1104 mmHg0.01Paat20 C,100Paat220 C,

1000Pa at 260 C, [4446]), the TCP samples in gas phase are not

readily available. A system was built in our lab for TCP sampling

and is shown schematically in Fig. 1. 0.5mL of TCP methanol solu-

tions with concentrations of10, 20, 30, 50, 100, 200, and 300M

were prepared from the20 mM TCPstock solution.N2was bubbledat a flow rate of 1.1L/min through the container with TCP for

5min at room temperature and then 5 min at 230 C (temperature

controlled with an oil bath) to make sure all TCP was evaporated.

The total N2 volume in 10min was 11 L 0.5mol (considered at

room temperature), therefore, TCP samples with 10, 20, 30, 50,

100, 200, and 300 ppb in gas phase were realized. Each sample was

flown along with N2 through the alkaline catalyst column where

it was hydrolyzed, following the dotted (red) arrow path in Fig. 1.

The alkaline catalyst column was prepared by packing a 100mg of

mixture of NaOHand Al2O3(1:10wt) inside.The preparation ofthe

catalyst is described in more detail in Ref. [17]. In the electronically

controlled TCP conversion box (dotted square in Fig. 1), valvesturned after 10min ofgas flow and the pumpworked topush 3mL

0.4M phosphate buffer solution to wash out TCP hydrolyzate for

detection at the sensor, following the solid (blue) arrow path in

Fig. 1 (its method of control was mentioned in Ref. [17]).

Engineoil samples were preparedby dissolving thesamples into

methanol in 2L/0.5 mL ratio and with the same procedure as TCP

samples. Oil BP274 does not include TCP, Mobil Jet Oil II includes

13%, and BP2380 includes 15%TCP [47]. BP274oil samples spiked

with TCP in different concentrations were also prepared, sampled,

and measured.

3. Results and discussion

3.1. Diffusion controlled cresol oxidation

The oxidation process of cresol on a bare glassy carbon working

electrode was studied with cyclic voltammetry (CV). In the CV

curve (Fig. 2), current increased quickly at the beginning in each

potential scan due to the charging current, followed by a flat line.

Starting from around0.4 V, current increasedagainwhichindicates

the onset of oxidation of cresol. The oxidation was restricted to

Fig. 2. Cyclicvoltammetry results ofcresoloxidationon bare glassycarbon electrode. (a)Firstcycleof cyclic voltammetryof 100M cresolin 0.4M phosphatebuffer solution

at scan rates varying from 10 to 200mV/s. scan rates increase along the arrow direction. Range of potential: 0800mV vs. Ag/AgCl/3M KCl. (b) Calibration of the relation

between thepeakcurrent density andsquare root ofthe scan rate. Thecoefficientof determination R2 indicates the variabilityfrom linear fit. Glassy carbonworkingelectrode

(3 mm) was usedfor all of detections and polished between uses.


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Fig. 3. Observationsof fouling on glassy carbon electrode from SEMand EDS. (a) SEMimage of Au sputtering coated bare electrode, (b) SEM image of fouled electrode, and

(c) EDS results of thebare and fouledelectrodes.

the vicinity of electrode surface and reduced the concentration

of oxidizable cresol in this area. Once the concentration gradient

existed between the vicinity of electrode surface and the bulk

solution, diffusion occurred which yielded a mass flow ofcresol

from bulk to electrode surface. In this batch mode, migration was

reduced to negligible levels by addition ofa high concentration of

phosphate ions and convection was avoided by preventing stirring

and vibrations, which made diffusion the only path for mass

transfer. We define a diffusion layer where linear concentration

gradient exists. The thickness of the diffusion layer increased with

time which would flatten the concentration profile. In contrast,

the potential continued to scan positively and decreased the

concentration of oxidizable cresol in the vicinity of electrode

surface, which steepen the concentration profile. The slope of con-

centration difference was intensified; when the effect ofpotential

scan dominated first, so did the diffusion, and thus the current

increased which yields the left shoulder of CV peak. Potential scan

kept going positively and the concentration of oxidizable cresol

in the vicinity decreased approaching zero. By the point when

vincinity concentration dropped relatively slower, since it already

approached zero, the diffusion layer thicken effect dominated

and thus the slope of concentration difference reduced. The

current started to decrease, meanwhile, an IV peak was created

[48].

Fig. 4. PEDOT:PSSmodification of glassy carbonelectrodes. (a) Amperometric results of 4 electrodesapplied with0.5 mC of charge in EDOT:PSS solution, (be)optical images

ofthese 4 electrodes after modification with 0.5mC of charge, (fi) opticalimages of 4 electrodes after modification with 1, 1.3, 2, and 4mC of charge, (jl) SEM images of

electrode surfaceapplied with 0.3, 0.5, and 2 mC of chargein EDOT/PSS solution.


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Fig. 5. Amperometric results of 10M cresol on bare and modified electrodes. (a) Initial amperometric peaks obtained from successive injections of 10M cresolin 0.4M

phosphate buffer. Two experiments have been carriedout on bare electrodeand fiveon modified electrodes, two examples of which are shown here. (b) Calibration of peak

current vs. peaks. Note that the first peak ineachcase has been normalized to 100%. Unicell glassycarbonelectrodes with 2 mm diameter were used.

The results of CV experiments demonstrating the change of the

IV at different scan rates are shown in Fig. 2. 100M p-cresol

in 0.4M phosphate buffer was used as the analyte solution, and

the potential was scanned in the range of 00.8V vs. Ag/AgCl/3M

KCl with scan rates of10, 20, 50, 80, 100, 120, 150, and 200 mV/s.

Following the higher scan rate, the whole IV cycle expanded due

to the increased charging current. The peak current also increased

(Fig. 2a). Fig. 2b shows the calibration ofcurrent density vs square

root of scan rate. The linear relation indicates the oxidation pro-

cess of cresol is limited by the diffusion to electrode surface, while

the electron transfer at electrode/solution interface is relatively

quick [41,49]. The diffusion controlled property ofcresol oxidation

ensures thatcurrent signalis proportional to the bulkconcentration

inCV as well as amperometry mode.

Lookingat thereversal scan curve in Fig. 2a,we note theabsence

of reduction peak which indicates the process was not reversible.

Cresol was oxidized to radicals, followed by the radical coupling

and the formation of inert dimers or oligomers. A stable polymericlayerformed,finally, andbroughtthe electrode fouling [30]. Indeed,

while this fouling layer could be removed by physical polishing, it

is inert to chemicals and cannot be oxidized until a potential ofup

to 3V is applied [50].

3.2. Microscopy images of electrode fouling

The formation offouling layer was studied by SEM, EDS, and

AFM. For SEM imaging, the electrodes were sputter coated prior to

analysis. One electrode was left polished, while the other one was

fouled by 10 injections of 10M cresol in 0.4MPB buffer in amper-

ometry mode. The polished electrode and fouled electrode were

comparedin SEMimages (Fig.3aand b).Onlysputter coatedAu was

seenon polished electrode,but additionalstructures wereobserved

from the surface of fouled electrode. EDS shows the existence ofoxygen on thefouledelectrode, which could come from the fouling

products of cresol (Fig. 3c). AFM images also confirm the existence

of fouling layer on electrode surface (Results not shown). The sur-

face profile of fouled electrodes varied in the range of 030 nm

while the variation in the bare electrode was less than 15nm.

3.3. Controlled PEDOT:PSS modification onglassy carbon

electrode

To reduce the fouling from oxidation of cresol, PEDOT:PSS

modification was applied on glassy carbon electrode via elec-

tropolymerization. One important parameter for modification is

the reproducibility. To show the ability to control modifica-

tion, 4 unicell glassy carbon electrodes (2mm ) were immersed

in EDOT/NaPSS solution and applied 0.5 mC of charge (poten-

tial= 0.95V in single-potential amperometry mode). Fig. 4ae

shows the results ofthese modifications. The amperometry pro-

files were almostthe same forthese 4 electrodesas shownin Fig.4a,

and all of these 4 electrodes had the same color after modification

Fig. 6. Amperometric results of injections of 0.210M cresol in 0.4M phosphate

buffer. (a) Two representative sets of continuously amperometric results. Different

concentrations of cresol samples were injected in random order to avoid poten-

tial system error and by this way electrode fouling could be seen more clearly.

(b) Calibration curve of detection of cresol with different concentrations on modi-

fied electrode. The coefficient of determination R2 indicates the variation of linear

fit. Error bars are marked as bars above and below current symbols. Unicell glassy

carbon electrodes with 2 mm diameter were used.


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which indicates the uniform and controllable configuration. Addi-

tionally, 4 more electrodes were coated with 1, 1.3, 2, and 4mC

of charge. The color of modified electrode surface changed with

different amounts ofcharge (Fig. 4fi).

SEM was also carried out to compare the electrode surfaces

modified with 0.3, 0.5, and 2 m C of charge. Images from left to

rightcorrespondto increasinglymore charge(Fig.4jl). During SEM

imaging, the configuration was seen to be uniform over the whole

electrode surface and so representative SEM images in small areas

can be produced. Fig. 4jl illustrate the change in morphology andparticle size of the PEDOT layer. Cracks formed on the PEDOT:PSS

layer prepared by applying 2 mC of charge

3.4. Detection of cresol with modified electrodes

The controlled PEDOT:PSS modification described above was

used to reduce fouling effect in the amperometric detection of

cresol. 10M cresol in 0.4M phosphate buffer was injected suc-

cessively on both modified (left side ofFig. 5a) and un-modified

electrodes (right side of Fig. 5a). The peak currents decayed in

both cases after repeated exposure to cresol, but magnitude of

the decrease was much lower in the modified electrode. For com-

parison, the peak height was normalized to the first peak in each

case being normalized to 100%. The successive peaks were seri-ously decayed on bare electrode but much less fouling occurred

on modified electrode (Fig. 5b). The comparison indicates that for

continuous on-site monitoring ofTCP, the bare electrode is not a

good candidate. Although thoroughly polishing the electrode could

remove the fouling layer, this would require trained personnel and

adds complexity to sensor operation. Modified electrodes, how-

ever, overcome this limitation.

With modified electrodes, a series of cresol samples with con-

centrations of 0.2, 0.5, 1, 2, 5, 7.5, and 10M were detected in

amperometry mode 3 times at each concentration). Two represen-

tativeexamplesofinitialamperometric results are shownin Fig.6a.All samples were injected in random order to avoid system error

andto show foulingclearer since signal from a samplewoulddecay

more if a higher concentration was previously injected. The cali-

bration curve is shown in Fig.6b. A linear relationship between the

peak current and the concentration ofcresol was obtained, con-

firmed by the R2 being very close to unity. The error bars which

were contributed mainly from electrode fouling were too small to

be distinguished from the data symbols. Therefore, thedetection of

0.210M cresol was reliable with the modified electrode.

3.5. Detection of TCP with modified electrodes

To show the ability of detecting TCP samples, several TCP

samples with 10, 20, 30, 50, 100, 200, and 300p pb were gasi-fied, hydrolyzed, and detected with PEDOT:PSS modified electrode.

Fig. 7. Detectionof TCPon bare/modified electrode. (a,left)Calibrationof detectionof TCPsamples with concentrationsof 10,20, 30, 50,100, 200, and300 ppbon PEDOT:PSS

modified electrode, (a, right) Calibration of detection of 30, 50, 100, and 300ppb TCP on bare electrode. 10 and 20ppb were not detected and compared with modified

electrode, (b) responsesfrom modified electrode were normalized to 100%and the error bars andsignals from bare electrodewere relatively calibrated. RSD wascalculated

from the ratio of Stdev (standard deviation) to Avg (average). Unicell glassy carbon electrodes with 2mm diameter were used. Note that the bare electrode was polished

after measurement of each setof 4 samples, while modified electrode was not polished through three sets of measurements.


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Experiments have been carried out three times. The calibration of

allthree experiments is shown in theleft frame ofFig. 7a. Errorbars

indicate the variation between all three experiments. A linear rela-

tionship was observed between current signal and concentration

of sample in the range of 50300ppb. For comparison, the corre-

sponding results from bare electrodes are shown in the right side

ofFig. 7a, excluding 10 and 20ppb TCP. Although a linear relation

wasalsoobserved, theerror bars were much biggerdue toelectrode

fouling. Note that the bare electrode was polished after measure-

ment of each set of 4 samples. The fouling effect would be muchmore serious if the electrode were left unpolished through the

whole measurement, which was done for modified electrode. To

observe the comparison clearly, the responses from modified elec-

trodeswerenormalized to100% andthe signalsfrombare electrode

and error bars were relatively calibrated (Fig. 7b). Comparing the

error bars andRSD values from modifiedelectrode with those from

bare electrode,modified electrode wasseen to have much less foul-

ing. Indicated by these results, the sensing system with PEDOT:PSS

modifiedelectrode is able to continuouslymonitor TCPin gasphase

in the concentration range of50300ppb. It should be mentioned

that the lower point of the linear range for the PEDOT:PSS modi-

fied electrode (50 ppb) is comparable with others work. De Nola

reported the LOD of1.4 pg/20 nL(70ppb, TCP in isohexane) using

gas chromatography [13].

Previously, our group reported the detection ofTCP with bare

glassy carbon electrodes with a linear range of5300 ppb [51].

However, the bare electrodes required thorough polishing before

each measurement, which would make impossible its usage for

continuously monitoring TCP on the aircraft.

3.6. Detection of hydrolysates from engine oils

Finally, to test the ability ofthis system to determine TCP in

air from real samples, such as samples from jet engine oils, 2L

of commercially available BP Turbo Oil 274, BP Turbo Oil 2380, and

MobileJet Oil II weremixed in 0.5 mLof methanol and were usedto

prepare the hydrolysate samples with the same procedure as TCP

hydrolysates described above. The results ofoil hydrolysates with

Fig. 8. Detectionof commercial engineoil andoil spikedhydrolysatesamples.All samples were measured randomly 3 times.(a) Results of hydrolysate samples from engine

oils BP 274, Mobil, and BP 2380with modified electrode; (b) with unmodified electrode. (c) Calibration of the concentrations of TCP in the oilsamples, and the results from

modified electrode and unmodified electrode were compared with the claimed values by manufactures. (d) Results of hydrolysate samples from oil BP 274 spiked with

0200 ppbTCP with modified electrode;(e) with unmodifiedelectrode. (f)Comparisonof theresults between themodifiedand unmodifiedelectrode. RSD(relative standard

deviation) was calculated the same as Fig. 7.


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Biographies

Xiaoyun Yang received the B.S. degree in Chemistry from Tongji University,Shanghai, Chinain 2006, followedby 2-years studying for Masters degree in Physicsdepartment. Currently, he is pursuing his PhD degree in Materials Engineering atAuburn University.

Jeffrey Kirsch received his B.S. in Materials Engineering at Auburn University,Auburn, Alabama in2011. Currently, heis pursuing hisMasters Degree in MaterialsEngineering at Auburn University.

Dr.EricV.Olsenisthe Directorof theClinicalResearch at KeeslerAFB Mississippi. Hereceived hisPh.D.in Biological Sciences andM.S. in Microbiologyfrom Auburn Uni-versity. His research interests include PCR assay development, piezoelectric-basedbiosensor systems andbio-preservation techniques. Heis a Lt.Colonelin the UnitedStates AirForce with over 20 years of service.

Dr.JeffreyW. Fergus received his B.S. degree in Metallurgical Engineering fromtheUniversity of Illinoisin 1985andhis Ph.D. degreein MaterialsScienceand Engineer-ing from the University of Pennsylvania in 1990. He was a post-doctoral researchassociate in theCenter for Sensor Materialsat theUniversity of Notre Dame and, in1992,joined the Materials Engineering program at Auburn University, where he iscurrently a professor. His research interests are generally in high-temperature andsolid-state chemistry of materials, including electrochemical devices (e.g. chemicalsensors andfuel cells)and thechemicalstability of materials(e.g.hightemperatureoxidation).

Dr.AlexL. Simonianisa Professorof MaterialsEngineeringat AuburnUniversityanda Biosensing Program Directorat NSF. Hereceivedhis M.S. inPhysics from theYere-van State University (Armenia, USSR), a Ph.D. in Biophysics and a Doctor of Sciencedegree in Bioengineering from the USSR Academy of Science. His current researchinterests are primarily in the areas of bioanalytical sensors, nano-biomaterials andfunctional interfaces.

2013-Anti-fouling PEDOT-PSS Modification on Glassy Carbon Electrodes for Continuous_2

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