Nanoscale Surface Characterizations of Modified Carbon Fibre Microelectrodes & Electrochemical Detection of Dopamine.

Prof.Dr.A.Sezai SARAÇ

Istanbul Technical UniversityPhysical Chemistry &Polymer Science & Technology

Istanbul Technical University ELECTROPOL RESEARCH GROUP

o http://www.kimya.itu.edu.tr/saraca/o http://atlas.cc.itu.edu.tr/~sarac/

Conductive Nanosize-polymeric Thin films ,Nanomodification (The efficiency:

i.e., scan rate, scan number ,solvent ,feed ratio and morphology ) Electrocoating of Heterocyclic conjugated monomers

on Carbon Fiber by cyclic voltammetry. Surface Characterizations Electrochemical Impedance Spectroscopy: Film & double layer capacitance& charge transfer

resistance

• Microsensor ve Biosensor Applications• Electrochromic Applications• Carbon Fiber-Polymer Composites

Prep. & charac. of neurotransmitter sensitive carbon fiber microelectrodes by coating with conjugated polymers

5-7μ

A.S. Sarac, A. Bismarck, E. Kumru, J. Springer, Synth. Met. 123 (2001) 411

E.Kumru,J.Springer,A.S.Sarac,A.Bismarck.,  Synth. Met.  123(2001)391

Sarac et.al..,J.Nanosci.and Nanotech. 10, (2005) 1677–1682

CF -carbon fibersCF -carbon fibers

Biocompatible & electrochemically reversible microbiosensor

Electrochemical surface modificationElectrochemical surface modification

Electrocoating & surface charac.

Surface Analysispolymeric Thin Film ~10-100nm Functionalities

FTIR-ATR Raman ,FIBSIMS ,E

DX,XPS Morphologic

SEM AFM

Cyclovoltammetric Electrochem.Impedanc

e Spectroscopy

POLYMERIC NANOSTRUCTURES. (Book Ch)“Nanoscale Characterization of Conductive Polymer Electrocoated Carbon Fiber Surface “A.Sezai SARAC Editor,H. S. Nalwa, Amer. Sci.Pub. California, USA (2006)

“Electropolymerization” , A.Sezai SARAC,Encyclopedia of Polymer Science and Technology ,3rd Ed. Ed.H. F. Mark John Wiley & Sons, New York (2005)

elektroniyon

foton

S *S

* n

N

*

m

H

NS OO

CH3

PProDOT-Me2/CFME

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

5000

6000

7000

Cu

rren

t d

ensi

ty / A

/cm

2

Potential / V

0,01 M DMPOT0,1 M Bu4NPF6 in ACN100 mV/s, 40cycleQ=278,1 mC

-0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2

-10000

-5000

0

5000

300 mV/s

20 mV/s

Cu

rre

nt d

en

sity

/ A

/ cm

2

Potantial / V

a)Cyclic voltammogram(CV) Electrogrowth of 10 mM PProDOT-Me2

in 0,1 M Bu4NPF6/ACN scan rate:100 mV/s scan number: 40 th cycle on CFME Q=278.1 mC

b) Polymer cycled at different scan rates (in Monomer -free

electrolyte) in 0,1 M Bu4NPF6/ACN scan rate: 20-400 mV/s.

PProDOT-Me2 /CFME

Nyquist & Bode Phase Plots (PProDOT-Me2) Electrochemical Impedance Spectroscopy

0 50 100 150 200 250

0

50

100

150

200

250

Zim

/kO

hm

Zre / kOhm

1.157 mC 2.157 mC13.86 mC 4.076 mC 278.1 mC

HIGH CAPACITANCEHIGH CAPACITANCE

0,01 0,1 1 10 100 1000 10000 100000

0

20

40

60

80

100

Pha

se o

f Z /

degr

ee

frequency /Hz

1.157 mC 2.157 mC13.86 mC 4.076 mC 278.1 mC

Electroactive polycarbazole(PCz) film.

-0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4 1,6-0,0005

-0,0004

-0,0003

-0,0002

-0,0001

0,0000

0,0001

0,0002

0,0003

0,0004

0,0005

0,0006

0,0007

0,0008

Polymer Growth on 6 coated CFME

10-3M Cz in 0,05M TEAP/CH2Cl

2

40mV/s5 cycles

Cu

rre

nt (

A)

Potential (V) vs. Ag

N

*

m

H

SARAC,A.S ,Microelectronic Eng. 83( 4-9) (2006) 1534-1537SARAC,A.S.,ATES,M.,PARLAK,E.A.,J.Appl.Electrochem.(2006) in press

0.1M NaClO4/PC

ip = (2.69 x 108) n3/2 A C D1/2 ν1/2

Randles Selvic

Polycarbazole (PCz)/CFME

N

*

m

H

Multisweep cyclovoltammogram of electrochemical PCz growth in 1 mM Cz in 0.05M TEAP/ CH2Cl2 on a CFME, at scan rate of 40 mV/s. (inset: polymer growth single CF and 10single CFs)

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4

-500

0

500

1000

1500

2000

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4

-150

-100

-50

0

50

100

150

200

250

300

350

400 1 s ing le C F 100 s ingle C Fs

Cu

rre

nt

De

ns

ity

(A

/cm2 )

Potential (V)

Cu

rren

t D

en

sit

y (A

/cm

2 )

Potential (V)

N

*

m

H

CV of PCz in monomer -free electrolyte (Doping-dedoping)

at scan rate of 20 to 100mV/s.

0,0 0,2 0,4 0,6 0,8 1,0 1,2 1,4

-200

-100

0

100

200

300

400100 mV/s

20 mV/s

4 5 6 7 8 9 10

-400

-300

-200

-100

0

100

200

300

400

500

600

anodic (R: 0.996) cathodic (R: 0.995)

Cu

rren

t d

ensi

ty (

A/c

m2 )

[Scan Rate (mV/s) ]1/2

Cu

rren

t D

ensit

y (A

/cm

2 )

Potential (V)

(inset: Current density (inset: Current density vs.vs. square root of scan rate square root of scan rate for PCz )for PCz )

Cv of PCz on CFME in monomer- free solution for different thickness of thin film: 5, 7 and 10 cycles. (at 60 mV/s)

0,6 0,8 1,0 1,2 1,4

-100

-50

0

50

100

150

200

10 cycles 7 cycles 5 cycles

(60 mV/s)

Cu

rren

t d

en

sit

y (A

/cm

2 )

Potential (V)N

*

m

H

Ex-situ FTIR-ATR spectra of PCz electrografted CFME by 3 to 10

cycles.

4000,0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 650,0cm-1

%T

3 cycles5 cycles7 cycles10 cycles

1598,03

1537,35

1443,82

1395,78

1299,71

1330,05

1231,46

1180,89

1034,26

875,00

796,62

725,84

672,75

2329,11

2987,34

2901,26

N

*

m

H

Ex-situ spectroelectrochemistry (FTIR-ATR)

3 4 5 6 7 8 9 10

0

1

2

3

4

5

6

7

8

9

10

11

12

1600cm-1

1536cm-1

1050cm-1

Co

rrec

ted

Hei

gh

t,%

T

scan number

from FTIR-ATR of PCz with different cyclesfrom FTIR-ATR of PCz with different cycles (C-C,C=C ,C-N) (C-C,C=C ,C-N)

N

*

m

H

Core-level XPS spectra in the region of C 1s (a);N 1s (b) for polycarbazole on CF

A.S.Sarac AS, T Syed, M Serantoni, J Henry, VJ Cunnane, JB McMonagle, Appl.Surface Sci. 222(2004)148

XPS high- resolution scan

N

*

m

H

PTSP/Cz= 10:1

NaClO4 /PC

Morphology-Composition For copolymer

P[Cz-co-PTSP] [PTSP]/ [Cz ]= 100:1 in 0.1M NaClO4 /PC

-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6

-0.5

0.0

0.5

1.0

1.5

2.0

Cur

rent

den

sity

(m

Acm

-2)

Potantial (V vs.Ag/AgCl)

Poly(Cz-co-pTsp) ; [pTsp]0/[Cz]0=100

PTSP/Cz= 100:1

NaClO4 /PC

PTSP/Cz= 200:1 in NaClO4 /PC

SO O

CH3

N

H

N

n

m

FTIR-ATR (copolymer)

4000,0 3600 3200 2800 2400 2000 1800 1600 1400 1200 1000 800 650,0

44,4

46

48

50

52

54

56

58

60

62

64

66

68

70

72

74

76

78

80

82

84

86

87,6

cm-1

%T

PCz

Cz/PTSP 1:100

Cz/PTSP 1:5

Cz/PTSP 1:1

Cz/PTSP 1:2

Cz/pTSP=1:1

Cz/pTSP=1:100

Cz

P(Cz) 0.1 M TEATFB / ACN -CFME. )Polycarbazole( 1 mM Cz-TEAP/DCM)

0.2 0.4 0.6 0.8 1.0 1.2 1.4-0.02

-0.01

0.00

0.01

0.02

0.03

0.04

0.05

0.06

20 mV/s 40 mV/s 80 mV/s 100 mV/s

Curr

ent densi

ty , m

A/cm

2

Potential / V (vs.Ag)

AFM images : (a) uncoated carbon fiber, (b) Polycarbazole coated CF

Multisweep voltamogram Multisweep voltamogram

ELECTROCHEMICAL IMPEDANCE SPECTROSCOPY Nyquist & Bode plots

PCz s/CF TEAP/CH2Cl2, [0,01Hz-100kHz]

-0,5 0,0 0,5 1,0 1,5 2,0 2,5 3,0 3,5 4,0

0,0

0,5

1,0

1,5

2,0

2,5

3,0 PCz PEtCz PNVCz

-z// ,M

ohm

s

z/,Mohms

1E-3 0,01 0,1 1 10 100 1000 10000 100000 1000000-10

0

10

20

30

40

50

60

70

80

90

PEtCz PNVCz PCz

-bod

e ph

ase

angl

e

frequency,Hz

SENSOR p-aminophenol ,

1 μM-100nM

p-Aminophenol

NH

OH

NH

O

3 3

+ H+

+ e-

CF

JAMAL,M., MAGNER,E., SARAC,A.S., Sensors and Actuators (2004) 97,59

p[NVCzVBSA1] ( □); p[NVCzVBSA2] (∆ ); p[CzMeTh] (o ); p[Cz] (×); untreated (◊ ).

                                   

p-aminophenol

Redox Behavior of Dopamine

Molecular structure ofthe protonated dopamine1

1. Venton, B.J. and Wightman, R. M., 2003. Psychoanalytical Electrochemistry: Dopamine and Behavior, Analytical Chemistry, 414 – 421 A.2. Chen, J. and Cha, C., 1999. Detection of dopamine in the presence of a large excess of ascorbic acid by using the powder microelectrode technique, Journal of Electroanalytical Chemistry, 463, 93–99.

Redox reaction betweendopamine and modified CFME2

Oxidation of Dopamine to Dopaminequinone

Dopamine is an easily oxidizable biological compound so it is electroactive.Dopamine oxidizes in solution at working electrode. The oxidized material gives up electrons which are collected by the working electrode (CFME) and generate a current flow through it. The detection of this current is the basis of the measurement method.

needle-type disk shaped PCz and P(Cz-co-pTsp) microelectrodes & Sensor behavior against Dopamine

Electroactive area of the carbon fibre

( ca. 5-7 µm)

Amperometric change (chronopotentiometry) time responseAmperometric change (chronopotentiometry) time response

0 400 800

4,00E-010

6,00E-010

8,00E-010

1,00E-009

1,20E-009

1,40E-009

1,60E-009cf3

P(Cz-co-pTsp)pTsp/ Cz:100 in NaClO

4/ACN

1008080

4040

20

20

1010

Cur

rent

/ A

Time / s

Amperometric study for Calibration Curves;

addition of Dopamine700 mV vs Ag/AgCl

0 200 400 600 800 1000

0,0

5,0x10-10

1,0x10-9

1,5x10-9

2,0x10-9

2,5x10-9

Cu

rren

t (A

)

Dopamine (µM)

Uncoated carbon fiber

0 200 400 600 800 1000

0,0

1,0x10-8

2,0x10-8

3,0x10-8

4,0x10-8

5,0x10-8

6,0x10-8

Cu

rren

t (A

)

Dopamine (µM)

PCz in LIClO4/ACN

0 200 400 600 800 1000

0,0

2,0x10-9

4,0x10-9

6,0x10-9

8,0x10-9

1,0x10-8

Cu

rren

t (A

)

Dopamine (µM)

PTsp/Cz (100:1) in LiClO4/ACN

Uncoated

PCz in LiClO4/ACNPTsp/Cz (100:1) LiClO4/ACN

Dopamine calibration curves700 mV vs Ag/AgCl

-0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2

0,0

1,0x10-8

2,0x10-8

3,0x10-8

4,0x10-8

5,0x10-8

Cu

rren

t (A

)

Potential (V)

CF6 DPV in 44 µM dopamine

-0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2

0,0

1,0x10-9

2,0x10-9

3,0x10-9

4,0x10-9

5,0x10-9 CF3 DPV in 44 µM Dopamine

Cu

rren

t (A

)

Potential (V)

-0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2

0,0

1,0x10-8

2,0x10-8

3,0x10-8

4,0x10-8

5,0x10-8

6,0x10-8

7,0x10-8

Cu

rren

t (A

)

Potential (V)

CF9 DPV in 44 µM Dopamine

Uncoated

PCz in LiClO4/ACN PTsp/Cz (100:1) LiCLO4/ACN

DPVs (Diferential Pulse Voltammetric Determination of Dopamine )

40 repetitive measurements for 44 µM dopamine

-0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,20,0

1,0x10-9

2,0x10-9

3,0x10-9

4,0x10-9

5,0x10-9

6,0x10-9

7,0x10-9

8,0x10-9 AA (100 µM) AA (200 µM) AA (300 µM) AA (400 µM) AA (500 µM) Dopamine (44 µM)

Cu

rren

t (A

)

Potential (V)

CF3 uncoated

-0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,2

2,0x10-8

3,0x10-8

4,0x10-8

5,0x10-8

6,0x10-8

7,0x10-8

8,0x10-8

9,0x10-8

AA (100 µM) AA (200 µM) AA (300 µM) AA (400 µM) AA (500 µM) Dopamine (44 µM)

Cu

rre

nt

(A)

Potential (V)

CF6

-0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,20,0

2,0x10-8

4,0x10-8

6,0x10-8

8,0x10-8

1,0x10-7

1,2x10-7

AA (100 µM) AA (200 µM) AA (300 µM) AA (400 µM) AA (500 µM) Dopamine (44 µM)

Cu

rre

nt

(A)

Dopamine (µM)

CF9

Uncoated

PCz in LiClO4/ACN PTsp/Cz (100:1) LiClO4/ACN

DPV response for five successiveadditions of 100 µM ascorbic acid (blue line)and an addition of 44 µM dopamine (red line)

-0,6 -0,4 -0,2 0,0 0,2 0,4 0,6 0,8 1,0 1,20,00E+000

2,00E-009

4,00E-009

6,00E-009

8,00E-009

1,00E-008

1,20E-008

1,40E-008

1,60E-008

1,80E-008

2,00E-008

DPV Measurements 50 L addition of dopamineC

urre

nt /

A

Potantial / V

PB 1 2 3 4 5 6 7 8

PPy & PCz/CFME Biosensor Electrodes

Monomers :

N

N

NH

N

CIO

1-(2- Cynoethyl)pyrrole[CEP]

Carbazole [Cz] Carbazole-N-carbonyl chloride

[CzCClO]

PCz thin filmPCz thin film coated coated //CFMECFME Cyclovoltammetric determination of Cyclovoltammetric determination of NeurotransmittersNeurotransmitters

((dopamine,dopamine,ephinephrine)ephinephrine)

with to response 100 μM dopamine/buffer at scan rate of 10mV/s. with to response 100 μM dopamine/buffer at scan rate of 10mV/s. (inset : 0.1 μM dopamine/buffer solution at scan rate of 1000 mV/s)(inset : 0.1 μM dopamine/buffer solution at scan rate of 1000 mV/s)

HO

HO NH2

O

O NH2

+ 2H+

+ 2 e-

-0,4 -0,2 0,0 0,2 0,4 0,6

-800

-600

-400

-200

0

200

400

600

800

1000

-0,2 0,0 0,2 0,4 0,6

-4000

-2000

0

2000

4000

6000

80000.1 M Dopamine Solution

Curr

ent D

ensi

ty (A

/cm

2 )

Potential (V)

100 M Dopamine solution

Cu

rren

t D

en

sit

y (A

/cm

2 )

Potential (V)

NH2 NH2

+ 2H+

+ 2 e-

HO

HO

O

O

current density vs. square root of scan rate : current density vs. square root of scan rate :

100100 to to 2000 mV/s2000 mV/s

10 20 30 40-4000

-3000

-2000

-1000

0

1000

2000

3000

4000

C

urr

en

t D

en

sit

y (A

/cm

2 )

[Scan Rate (mV/s)]1/2

Anodic (R: 0.9797) Cathodic (R: 0.9882)

[100-2000] mV/s

The scan rate dependence of the anodic and cathodic peak currents show a linear dependence for PCEP, indicating electrochemical process is not diffusion limited and is reversible even at high scan rates.

current density vs concentration ofcurrent density vs concentration of dopamine :dopamine : 100 100 to to 500 nM.500 nM.

100 200 300 400 500

-2100

-2000

-1900

-1800

1900

2000

2100

2200

2300

C

urr

en

t D

en

sit

y (A

/cm

2 )

Concentration of Dopamine (nM)

Anodic (R: 0.97524) Cathodic (R: 0.98432)

current density from CV of response to current density from CV of response to dopamine vs. current density from CVdopamine vs. current density from CV of doping of doping

(before cycled at (before cycled at at scan rate of 60 mV/s at scan rate of 60 mV/s in in monomer monomer-- free free solution ) solution )

-400 -300 -200 -100 0 100 200 300 400 500 600

-600

-400

-200

0

200

400

600

800

1000

Cu

rren

t D

en

sit

y (A

/cm

2 )

dopamine, 1000mV/s

Current Density (A/cm2)

by potential scanning from a 10-3 M solution of monomer in 0.1 M TBAPF6 / Acetonitrile at 100 mV s-1 on carbon fiber micro-electrodes. (electrode area = 1.0x10-3 cm2)

Response of poly(1-(2-Cynoethyl)pyrrole) coated carbon fiber microelectrodes in 1mM Dopamine in phosphate buffer solution at 300 mV s-1.N

N

1-(2- Cynoethyl)pyrrole

[CEP]

PCPCEPEP thin film thin film coated coated //CFMECFME

Electrodeposition of CEP

PF6ˉ

Electropolymerization

• 5 mM CEP in 0.1M Et0.1M Et44NBFNBF44//ACNACN• on a CFME (area ~0.001 cm2)• at scan rate of 100 mV/s

• PCEP in monomer free electrolytemonomer free electrolyte at scan rate of

•20 mV/s•40 mV/s•60 mV/s•80 mV/s•100 mV/s

•120 mV/s•140 mV/s•160 mV/s•180 mV/s•200 mV/s

805 mV

700 mV

453 mV

606 mV

884 mV

781 mV

BFBF44ˉ̄

Investigation of Optimum Conditions

Dopamine Biosensor

• Electrolyte effect

• Overoxidation and overoxidation time

• Concentration of dopamine – Calibration curves

Electrolyte Effect

805 mV

700 mV

453 mV

-0.2 0.0 0.2 0.4 0.6

-6

-4

-2

0

2

4

6

8

Cu

rren

t D

en

sit

y / m

A c

m-2

Potential / V

221 mV

72 mV

0.1 M Potassium Perchlorate0.1 M Potassium Perchlorate

[KClO[KClO44]]

• 5 mM CEP• on a CFME (area ~0.001 cm2)• at scan rate of 100 mV/s

0.1M 0.1M TTetraethetraethylyl ammonium ammonium tetrafloraboratetetrafloraborate [ [EtEt44NBFNBF44] ] //ACNACN

Response to 10 M Dopamine

E = 149 mV

536 mV835 mV

676 mV-0.2 0.0 0.2 0.4 0.6

-0.10

-0.05

0.00

0.05

0.10

0.15

0.20

Cu

rren

t D

ensi

ty /

mA

cm

-2

Potential / V

135 mV

200 mV

Response to 10 M Dopamine

E = 65 mV

Overoxidation(doping) Effect

E= 148mV

E= 151 mV

Response to 10 M Dopamine

20 times higher 20 times higher

The best time for overoxidation by

chronoamperometry

300 s300 s E= 122 mV

Effect of Dopamine Concentration

R : 0.99906R : 0.99906

10 10 -7-7 – 10 – 10 -3-3 MM Dopamine in pH=7.4

Buffer Solution

Calibration Curve

• PCEP modified CFME prepared by• 5mM CEP in 0.1 M Et4NBF4/ACN overoxidized at 300s

0.54 mA

Effect of Dopamine Concentration

N

CIO

Polycarbazole modified CFME

Poly (Carbazole-N-Carbonyl Chloride)modified CFME

Electropolymerization conditions of Polycarbazole and Poly (Carbazole-N-Carbonyl Chloride) are the same to PCEP.

10 10 -7-7 – 10 – 10 -3-3 MM Dopamine in pH=7.4 Buffer Solution

E = 98 mV

E = 151 mV

NH

Conclusion

The suitable conditions were investigated for more sensitive and selective dopamine biosensor CFME:

Potassium Perchlorate / ACN electrolyte solution Overoxidation for 300s The polymer modified CFMEs prepared by all

monomers used in this study response to dopamine in range of 10-7 to 10-3 M (after they were overoxidized).

Electropolymerization of 1-(2-Cyanoethyl)pyrrole monomer on CFME present well defined and reversible redox processes.

The electroactivity and well defined electrochemistry of PCEP on CFME (better than Pt ) make possible using these electrodes to determine up to physiological concentration level.

conclusions• CV,DPV• XPS • FTIR-ATR, Raman Spectroscopy

• Electrochemical: Cyclovoltammetric Methods can be applied for the Nanoscale Charac. Conjugated Nanoscale Polymeric Films

on Micron Sized Carbon Fibers(& thin films).• Electrochemical Impedance Spectroscopy can be applied to such films to obtain Charge Capacity

of microelectrodes (films and interface) • Substituent ,solvent & electrolyte plays an important

role on final properties

acknowlegements Dr.M.Serantoni ,Dr.A.M.S.Tofail -University of

Limerick, Dr.Schulz IDM-Teltow Germany

My Students: in Polymer Sci.& Tech.Grad.Prog

M.Ates ,Ph.D F.C.Cebeci , Ph.D. E.Alturk Parlak,Ph.D. E.Ayaz , Msc. A.Gencturk,MSc.

Istanbul -Bosphorous(16 th Century)

Thank You                           

sarac@itu.edu.trhttp://atlas.cc.itu.edu.tr/~sarac/http://www.kimya.itu.edu.tr/saraca/