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Materials Chemistry and Physics 127 (2011) 120–127

Contents lists available at ScienceDirect

Materials Chemistry and Physics

journa l homepage: www.e lsev ier .com/ locate /matchemphys

lectrochemical impedance of poly(9-tosyl-9H-carbazole-co-pyrrole)lectrocoated carbon fiber

urat Atesa, Nesimi Uludaga, A. Sezai Saracb,∗

Department of Chemistry, Faculty of Arts and Sciences, Namik Kemal University, Degirmenalti Campus, 59030, Tekirdag, TurkeyDepartment of Chemistry, Polymer Science & Technology, Istanbul Technical University, Maslak, 34469, Istanbul, Turkey

r t i c l e i n f o

rticle history:eceived 21 March 2010eceived in revised form 3 December 2010ccepted 19 January 2011

eywords:

a b s t r a c t

In this paper, copolymer of 9-tosyl-9H-carbazole (TCz) and pyrrole (Py) comonomers were electro-chemically deposited onto carbon fiber micro electrode (CFME) as an active electrode material. Anelectrochemical impedance study on the prepared electrodes is reported. Poly(TCz-co-Py)/CFME is char-acterized by cyclic voltammetry (CV), Fourier transform infrared reflectance-attenuated total reflectionspectroscopy (FTIR-ATR), scanning electron microscopy–energy dispersive X-ray analysis (SEM–EDX),

lectrochemical propertiesoatingshin filmslectrical properties

and electrochemical impedance spectroscopy (EIS). Capacitive behaviors of modified CFMEs were definedvia Nyquist, Bode-magnitude and Bode-phase plots. An examination is made of which equivalent circuitsof R(C(R(Q(RW)))) and R(C(R(Q(RW))))(CR) used for modeling the system. The effect of monomer ratio(mole fraction, XTCz = nTCz/nTCz + nPy) on the formation of copolymer is reported in 0.1 M sodium per-chlorate (NaClO4)/acetonitrile (ACN) solution. The inclusion of TCz in the copolymer structure was alsoconfirmed by FTIR-ATR, SEM, and CV measurements. The highest low frequency capacitance (CLF = 22.7

F = 22

for R(C(R(Q(RW)))) and CL

. Introduction

The electronic properties of conducting polymers have focusedn the research for various applications [1–3] including anti-staticnd anti-corrosion coatings [4,5], sensors [6–8], batteries [9], super-apacitors [10], light emitting diodes (LEDs) [11], electrochromicevices [12], drug delivery systems [13] and transparent electrodeaterials [14].Polypyrrole (PPy) is one of the most extensively studied

onducting polymers due to the ease of synthesis, good redox prop-rties, stability in the oxidized form, ability to give high electricalonductivities and useful electrical and optical properties [15–18].-Carbazole (N-Cz) has shown potential for technological appli-ations. Polymers based on this molecule display good electro-nd photoactive properties because of their high hole transport-ng mobility and strong absorption in the UV spectral region. Theormation of this polymer is of interest in understanding chargeransport, because it has a high �-conjugation compared to other

nown polymers [19,20]. As a rule poly(N-alkyl carbazole) haslready been used as hole transporting layer leading to dramaticmprovements in the performance of the light electroluminescentevices [21]. In literature, 2,7-linked carbazole main chain poly-

∗ Corresponding author. Tel.: +90 212 2853153; fax: +90 212 2856386.E-mail address: sarac@itu.edu.tr (A.S. Sarac).URL: http://web.itu.edu.tr/ sarac/ (A.S. Sarac).

254-0584/$ – see front matter © 2011 Elsevier B.V. All rights reserved.oi:10.1016/j.matchemphys.2011.01.050

.6 mF cm−2 for R(C(R(Q(RW))))(CR)) were obtained for XTCz = 0.91.© 2011 Elsevier B.V. All rights reserved.

mers [22–24] offer many advantageous properties. These polymersare highly fluorescent and emit in the blue part of the electromag-netic spectrum, however, CV studies on this class of polymers haverevealed that they do oxidize irreversibly under electrolytic condi-tions. Iraqi et al. have shown that upon methyl-substitution of the3,6-positions of the carbazole repeat units the polymers obtainedare much more stable to oxidation under electrolytic conditions[25].

Preparation of copolymers from mixtures of differentmonomers by electrochemical polymerization is a method tomodify the structure and properties of conducting polymers.This procedure allows one to obtain materials with controlledproperties without suffering the experimental disadvantagesassociated to the preparation of new homopolymers. As a result,copolymerization is an easy alternative to develop new materialswith properties usually intermediate between those of individualpolymers [26].

The resulting physical properties of electrocoated polymer filmsusing conjugated monomers (i.e. conductivity, morphology, ther-mal stability, etc.) are dependent on the properties and differentreactivity of the monomers [27]. Carbon fiber microelectrode(CFME) was used as working electrode in this study. Among the

carbon substrates found in the literature, CFME is well knownfor presenting a high surface area and, therefore, have been usedfor conducting polymer deposition [28,29]. The electrochemicaldeposition of conducting polymers on carbon surfaces has beenstudied with the goal of improving the mechanical and electri-

stry and Physics 127 (2011) 120–127 121

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CFME shows better reversibility with the value of ia/ic = 1.05 (ratioof anodic and cathodic current density) when XTCz = 0.5 is taken.The separation between the anodic and cathodic peaks is asso-ciated with the ion transport resistance involved in these redoxreactions [35–37]. Therefore, the difference between anodic and

Table 1Redox parameters of electrodeposited [TCz-co-Py] were obtained from CV. Anodicand cathodic current density ratios (ia/ic), anodic and cathodic peak potential dif-ference (Epa − Epc/V) and deposition charges (Q/mC) were determined.

Polymers ia/ic Epa − Epc Q/mC

Poly(Py) 1.88 0.07 90.59Poly(TCz) 0.35 0.29 222.0

Polymers XTsCz ia/ic Epa − Epc Q/mC

M. Ates et al. / Materials Chemi

al properties of these polymers so as to use them as electrodesn different applications such as batteries, sensors and capacitors30,31]. Impedance spectroscopy is a powerful technique for inves-igating electrochemical systems, processes and new materials. Its

ain strength lies in its ability to interrogate relaxation phenom-na whose time constants range over several orders of magnitude.owever, the results obtained using classical a.c. impedance spec-

roscopy is always averaged across the entire sample area [32].In this study, the random copolymer comprising 3,6-linked of

-tosyl-9H-carbazole and pyrrole were achieved electrochemicallynto carbon fiber micro electrodes. The effects of mole ratio fromTCz = 0.50 to 0.96 were investigated on thin polymer film prop-rties. The characterization of poly(TCz-co-Py)/CFME thin filmsas performed by SEM, FTIR-ATR, and EIS. EIS measurements

nd equivalent electrical circuit models of (R(C(R(Q(RW))))) and(C(R(Q(RW))))(CR) are discussed in detail.

. Experimental

.1. Materials

Carbazole (>95%) and pyrrole (>99%) were obtained from Sigma–Aldrich.etramethyl ammonium hydrogen sulfate, 4-toluene sulfonyl chloride, sodiumydroxide, silica gel (60 F254) and dichloromethane were purchased from Merck.odium perchlorate (>98%) was obtained from Fluka. The synthesis procedure of-tosyl-9H-carbazole was given in the literature [33]. All chemicals were analyticalrade reagents and were used as received.

.2. Instrumentation

Cyclic voltammetry was performed using PARSTAT 2263-1 (software, poweruit and Faraday cage, BAS Cell Stand C3) in a three-electrode electrochemical cellmploying CFME as the working electrode, platinum wire as the counter electrode,nd Ag wire as the reference electrode (calibrated against ferrocene).

Electrocoated CFMEs were characterized by FTIR reflectance spectroscopyPerkin Elmer, Spectrum One B, with a universal ATR attachment with a diamond andnSe crystal C70951). Perkin Elmer spectrum software was used to carry out FTIR-TR measurements between 650 and 4000 cm−1. Modified CFMEs were washed insolvent of acetonitrile.

The films of homo and copolymers, electrocoated onto carbon fibers werenalyzed by scanning electron microscopy using a NanoEye Desktop Mini-SEMnstrument (SNE-3000 M model, SEC GmbH, South Korea). The excitation energy

as 5 keV. Average values of the increase in thickness were obtained via SEM imagesaking into account the diameter of the uncoated fiber. The diameters for the fibersepresent an average of 5–6 measurements on carbon fiber.

.3. Preparation of the carbon fiber microelectrodes

High strength (HS) carbon fibers C 320.000 (CA) (Sigri Carbon, Meitingen,ermany) containing 320.000 single filaments in roving and high modulus (HM) car-on fibers were used as working electrodes. All of the electrodes were prepared using3 cm long bundle of the CFME (with average diameter of around 7 �m) attached

o a copper wire with a Teflon tape. A number of carbon fibers in the bundle werebout ∼50. One centimeter of the CFME was dipped into the solution to keep thelectrode area constant (∼0.11 cm2) and the rest of the electrode was covered withTeflon tape. The CFMEs were firstly cleaned with acetone and then dried with anir-dryer before the experiments [34].

.4. EIS and modeling

The electrochemical impedance spectroscopy (EIS) measurements were takent room temperature (25 ◦C ±1) using a conventional three electrode cell configura-

ion. The electrochemical parameters of the poly(TCz-co-Py)/CFME was evaluatedy the ZSimpWin (Version 3.10) software from Princeton Applied Research. EISeasurements were conducted in monomer-free electrolyte solution with a pertur-

ation amplitude 10 mV over a frequency range of 10 mHz to 100 kHz with PARSTAT263-1 (software; powersuit). Two different equivalent circuit models were used to

nterpret the results.

Fig. 1. CV for the electrogrowth of (a) Py, [Py]0 = 10 mM (b) TCz, [TCz]0 = 10 mMand (c) poly(TCz-co-Py), XTCz = 0.91. Electrodeposition was done on CFME in 0.1 MNaClO4/ACN at a scan rate of 50 mV s−1. Using multiple (8 cycles) and potentialrange: 0–1.1 V.

3. Results and discussion

3.1. Electro-co-polymerization of 9-tosyl-9H-carbazole withpyrrole

Electrocoating of monomer mixtures, namely of TCz and Pywas carried out to form poly(TCz-co-Py). Previously, 9-tosyl-9H-carbazole (TCz) has been electrodeposited on CFME by CV method[33]. Multisweep cyclic voltammogram of pyrrole (Py) (Fig. 1a), 9-tosyl-9H-carbazole (TCz) (Fig. 1b) and copolymer of TCz and Py(Fig. 1c) in 0.1 M NaClO4/ACN on CFME show an increasing cur-rent density with each cycle (corresponing potentials, Epa = 0.7 V,0.83 V and 0.81 V; Epc = 0.63 V, 0.54 V and 0.45 V), respectively.

Py, TCz and copolymer intensified during repetitive scans, indi-cating the doping–dedoping of the electro-active film. CV of themonomer mixture shows different redox behavior, and oxidationpotentials than monomers (Table 1). The charges were obtained90.59 and 222 mC in the initial monomer concentration of 10 mMduring electrogrowth process of Py and TCz, respectively. The high-est charge was obtained during electrogrowth process as 74.29 mCfor copolymer formation of XTCz = 0.91. Therefore, XTCz = 0.91 waspreferred in the copolymer mixture. Electrocopolymerization on

Poly(TCz-co-Py) 0.5 1.05 0.10 21.750.75 1.21 0.16 40.060.83 1.26 0.21 72.440.91 1.42 0.36 74.290.96 1.12 0.48 13.64

1 stry and Physics 127 (2011) 120–127

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22 M. Ates et al. / Materials Chemi

athodic peaks (�E) can serve as an indication for resistance of ionigration in the electrode [38]. The value of �E generally increasesith the thickness of the polymer film coated on the electrode. The

ncreasing thickness value was observed from SEM images.

.2. Effect of scan rate in monomer-free solution

A poly(TCz-co-Py)/CFME thin film was inserted into a monomer-ree electrolyte solution and its redox behavior was investigated.

The scan rate dependence of the electro-active film peak currentas studied only on the broad peaks at ∼0.72 V as given in Fig. 2.

he peak current density (i) for a reversible voltammogram at roomemperature (25 ◦C ± 1) is given by the following equation:

= (2.69 × 105) · A · D1/2 · C0 · �1/2

here � (V s−1) is the scan rate, A (cm2) is the electrode area,(cm2 s−1) is the diffusion coefficient of electro-active species,

nd C0 (mol L−1) is the concentration of electro-active species inolution. If the redox reaction is diffusionally controlled, the peakurrent should be linearly proportional to �1/2 [39]. The polymer-

Fig. 2. Plot of anodic and cathodic peak current density vs. the square root of thescan rate. Inset: plot of anodic and cathodic peak current density vs. scan rate anddependence of poly(TCz-co-Py) thin film for XTCz = 0.91 in monomer-free solution of0.1 M NaClO4/ACN.

Fig. 3. Mechanism of electrochemical copolymer formation of TCz and Py on CFME.

M. Ates et al. / Materials Chemistry and Physics 127 (2011) 120–127 123

Table 2Carbon (C), oxygen (O), sulfur (S), nitrogen (N), sodium (Na), chlorine (Cl), S/C and S/O, calculated from EDX point analysis for uncoated CFME, poly(Py), poly(TCz) andpoly(TCz-co-Py) (XTCz = 0.91).

Elements/weight %

K series point analysis C O S N Na Cl S/C S/O– – – – –20.72 0.70 2.89 – –18.03 – 0.15 0.0041 0.03119.03 0.80 2.89 0.022 0.026

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Uncoated CFME 85.19 14.81 –Poly(Py) 50.06 25.63 –Poly(TCz) 71.71 9.76 0.30Poly(TCz-co-Py) 41.28 35.10 0.90

zation process was applied at 50 mV s−1 at which the anodic andathodic peaks were well-defined, but at higher scan rates (suchs 500 mV s−1), the peaks were broader and less well-defined. Thishows that the electrochemical process is not completely diffusionontrolled even at high scan rates [40].

Anodic and cathodic redox reaction for poly(TCz-co-Py) formedn 0.1 M NaClO4/ACN appears to be diffusion controlled, as evi-enced by the linearity of the plot (R2a: 0.94147 at ∼0.72 V for thenodic reaction and R2c: 0.94939 at ∼0.72 V for the cathodic reac-ion) (see inset of Fig. 2). Moreover, it is also controlled surfacerocess (thin layer behavior, R1a: 0.98317 at ∼0.72 V for the anodiceaction, and R1c: 0.98923 at ∼0.72 V for the cathodic reaction) ashown in Fig. 2.

The synthesis route and possible copolymer formation mech-nism of TCz and Py electrocoated on CFME is shown in Fig. 3.irst, electro-oxidation of the pyrrole and 9-tosyl-9H-carbazoleonomers on CFME results in radical cation formation by electron

ransfer from monomers to electrodes. Dimer formation of pyrroleA) and 9-tosyl-9H-carbazole (B) through radical cation coupling,eprotonation, and neutral dimer and oligomer formations occur.he dimer and oligomers are added by the same coupling mech-nism to form poly(TCz-co-Py) (Fig. 3). The possibility to includeosyl group inside carbazole into the electrocoated copolymer, ashown in this study, opens the opportunity to use such modifiedarbon fibers to design and produce advanced reinforced polymericomposite materials [27].

.3. FTIR-ATR measurements

The FTIR-ATR spectra of uncoated CFME, poly(Py), poly(TCz) andoly(TCz-co-Py) were obtained from surface of the electrocoatedFMEs by reflectance FTIR measurements. Absorption bands of eachpectrum are given in Fig. 4. Comparison of the FTIR-ATR spectra

ig. 5. SEM images of (a) poly(Py) and (b) poly(TCz). Experimental conditions are 8th cycle

Fig. 4. FTIR-ATR spectrum results of uncoated CFME, pyrrole, 9-tosyl-9H-carbazole and copolymer for XTCz = 0.91 electrocoated on CFME. [Py]0 = 10 mM and[TCz]0 = 10 mM.

of poly(Py), poly(TCz) and poly(TCz-co-Py) thin films show that theincorporation of both Py and TCz monomers to the resulting desiredcopolymer were obtained for XTCz = 0.91. There are a few indica-tions of copolymer formation. For instance, the peak at 1448 cm−1,corresponding to –CH3 (sp3 CH stretching), and at 1301 cm−1, –CNstretching of aromatic C–N bonds or vibration of disubstituted ben-zene ring, provide evidence of copolymer formation. At the peak of716 cm−1 for poly(Py), (–C–H bending of trisubstituted aromatic

rings) shifts to 878 cm−1 for poly(TCz) and 836 cm−1 for copoly-mer. The absorption is due to the asymmetric stress vibration ofthe S O bond appeared around 1174 cm−1 but the absence of thebond around this range for poly(Py). The peak at 1153 cm−1 also

s, at a scan rate of 50 mV s−1, [Py]0 = 10 mM and [TCz]0 = 10 mM in 0.1 M NaClO4/ACN.

1 stry and Physics 127 (2011) 120–127

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24 M. Ates et al. / Materials Chemi

trongly proves the copolymer formation. The monomers of TCzre effectively bonded during copolymerization process. The bondxisted at 1287 cm−1 is confirmed by the valance vibration of C–Nond of carbazole cycle in the structure of copolymer [41]. Theeaks around 1096 cm−1 for poly(Py), 1054 cm−1 for poly(TCz) and012 cm−1 for XTCz = 0.91, are attributed to doping ClO4

− anion dueo the electrolytes from NaClO4 [42,43].

.4. SEM analysis

SEM images of poly(Py), poly(TCz) and poly(TCz-co-Py) indi-ates that electrodeposition of poly(Py) (Fig. 5a) is lower thanoly(TCz) (Fig. 5b). When the mole fraction of XTCz = 0.5, 0.75 and.91 were taken, the copolymer formation disperses the bigger arean CFME as shown in Fig. 6a–c. The main reason of this change maye due to the incorporation of TCz monomer into the copolymertructure. Electrochemically oxidized carbon fibers show nucle-tion growth on certain sites but not across the whole fiber surface.hen comparing the uncoated fibers, it can be seen that longi-

udinal striations on the coated samples have been filled withmall grain or micro spherical structure. A more continuous andven thicker copolymer coating can be observed after a few min-tes. Coating thickness for carbon fiber depends on the chargeassed through the fibers; an increase of charge increased thick-ess. SEM–EDX images (Figs. 7 and 8 and Table 2) were added toroof the copolymer formation. EDX data from experiments pointnalysis (Fig. 8 and Table 2) for uncoated CFME, poly(Py), poly(TCz)nd copolymer of XTCz = 0.91 in 0.1 M NaClO4/ACN on CFME indicatehat tosyl group included in the copolymer structure by existencef sulfur (S) element in the copolymer structure. The presence of O,a and Cl element’s peaks indicate the inclusion of dopant anion

ClO4−) of the supporting electrolyte into copolymer structure dur-

ng electro-growth process [38].

.5. Equivalent circuit modeling

Hypothetical electrical circuits, consisting of elements withell-defined electrical properties, have been used to describe the

lectrical response of the electrolyte/poly(TCz-co-Py)/CFME sys-em to a frequency range of 10 mHz to 100 kHz, evaluated bymploying ZSimpWin software from Princeton Applied Research.rom the correlation results; if the chi-square (�2) is observed asinimized below 10−4 (�2) is the function defined as the sum

f the squares of the residuals. The equivalent circuit models,(C(R(Q(RW)))) and R(C(R(Q(RW))))(CR), inside almost 90 electricalircuit models were applied for our experimental system. There-ore; the circuit model results were compared with uncoated CFMEnd in three different mole fraction of XTCz = 0.5, 0.75 and 0.91.quivalent circuits were tested in simulation of the impedanceehavior of the thin film from experimentally obtained impedanceata. The model of R(C(R(Q(RW)))) (Fig. 9a) was built using seriesomponents; the first one is the bulk solution resistance of theolymer and electrolyte, Rs, second one the parallel connectionf the double layer capacitance, C1, and R1 is the resistance ofhe electrolyte. A series connection to R1 made up using (Q) as

constant phase element in parallel with R2 and W. R2 is theharge transfer resistance and W is the Warburg impedance ofhe copolymer. Simulation results are given in Tables 3 and 4. Inrevious studies, these electrical equivalent circuits were success-ully applied to the experimental data to explain interface betweenhe CFME, poly(2,2-dimethyl-3,4-propylenedioxythiophene) [44]

nd poly(carbazole-co-p-tolylsulfonyl pyrrole) [45] thin films andlectrolyte in the frequency region of 10 mHz to 100 kHz. Inhe equivalent circuit of R(C(R(Q(RW))))(CR) [46–48], the secondomponent (C2) is in parallel to resistance of the CFME (R3).1 is constant phase element that takes into account the inter-

Fig. 6. SEM images of copolymer in different mole ratio of (a) XTCz = 0.75, (b)XTCz = 0.83 and (c) XTCz = 0.91. Experimental conditions are 8th cycles, at a scan rateof 50 mV s−1, [Py]0 = 10 mM and [TCz]0 = 10 mM in 0.1 M NaClO4/ACN.

facial irregularities such as porosity, roughness, and geometry

[49].

The resistance of the electrolyte (Rs) were approximatelyconstant for XTCz = 0.75 and 0.83 for the equivalent circuit ofR(C(R(Q(RW)))). However, Rs is the constant for XTCz = 0.83and 0.91 for the equivalent circuit of R(C(R(Q(RW))))(CR)

M. Ates et al. / Materials Chemistry and Physics 127 (2011) 120–127 125

Fig. 7. EDX-point analysis of poly(TCz-co-Py) was taken from SEM measurements,XTCz = 0.91 in 0.1 M NaClO4/ACN.

Fig. 9. Equivalent electrical circuit models of (a) R(C(R(Q(RW)))) and (b)R(C(R(Q(RW))))(CR).

Fig. 8. EDX point analysis results of (a) uncoated CFME, (b) poly(Py), (c) poly(TCz), and (d) poly(TCz-co-Py), XTCz = 0.91.

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spectroscopic measurements of poly(TCz-co-Py) for XTCz = 0.91were given in Fig. 10.

A value of double layer capacitance, C1 and C2, can be calcu-

26 M. Ates et al. / Materials Chemi

Fig. 9b). In contrast, the charge transfer resistance for(C(R(Q(RW))))(CR) was decreased by increasing of mole frac-ion of XTsCz = 0.5, 0.75 and 0.91, respectively (see in Table 3).hese changes may be explained by the thickness and sur-ace morphology of the polymer during electropolymerizationrocess.

The low frequency capacitance values from impedance spec-roscopy were obtained from the slope of a plot of the imaginaryomponent (Zim) of the impedance at low frequencies vs. inversef the reciprocal frequency (where f = 10 mHz) using the followingquation [50]:

LF = (2�fZim)−1

able 3ircuit modeling, R(C(R(Q(RW)))), results of electrochemically modified CFMEs with ZSimpf 50 mV s−1, using multiple (8 cycle) in 0.1 M NaClO4/ACN.

Circuit component R(C(R(Q(RW)))) Uncoated CFME

Rs/k� 0.06C1/�F cm−2 2.05R1/k� 0.28Q (CPE)/mS sn <5.0n 0.81R2/k� 0.034W/�S sn <0.1�2 1.52 × 10−4

Csp/mF cm−2 0.011

able 4ircuit modeling, R(C(R(Q(RW))))(CR), results of electrochemically modified CFMEs with Zate of 50 mV s−1, using multiple (8 cycle) in 0.1 M NaClO4/ACN.

Circuit component R(C(R(Q(RW)))) Uncoated CFME

Rs/k� 0.06C1/�F cm−2 2.05R1/k� 0.28Q (CPE)/mS sn <5.0n1 0.81R2/k� 0.034W/�S sn <5C2/�F cm−2 0.82R3/k� 0.44�2 1.52 × 10−4

Csp/mF cm−2 0.011

ig. 10. Bode-magnitute and phase plot for poly(TCz-co-Py) electrocoated on CFMEs. Plo(C(R(Q(RW))))(CR).

d Physics 127 (2011) 120–127

A low frequency, the imaginary part of the impedancesharply increases (as a vertical line) give the characteristicof capacitive behavior. The highest low frequency capacitance(CLF) was obtained from the Nyquist plot with XTCz = 0.91 as22.7 mF cm−2 and 22.6 mF cm−2 for the equivalent circuit modelsof R(C(R(Q(RW)))) and R(C(R(Q(RW))))(CR), respectively. This maybe related to the highest electro-deposition charge (74.2 mC) dur-ing electro-copolymerization process. Electrochemical impedance

Win simulating programme. Monomers deposited electrochemically at a scan rate

XTsCz

XTsCz = 0.75 XTsCz = 0.83 XTsCz = 0.91

0.69 0.67 0.422.58 4.12 4.120.82 0.69 0.48

<5.0 <5.0 <5.00.82 0.89 0.960.35 0.31 0.36

<0.1 <0.1 <0.19.36 × 10−4 9.35 × 10−4 8.42 × 10−4

12.7 9.4 22.7

SimpWin simulating programme. Monomers deposited electrochemically at a scan

XTsCz

XTsCz = 0.75 XTsCz = 0.83 XTsCz = 0.91

0.64 0.40 0.405.59 7.78 12.70.79 0.65 0.39

<5.0 <5.0 <5.00.91 0.95 0.969.19 5.83 1.73

<5 <5 <50.88 1.65 2.170.57 0.41 0.141.74 × 10−4 2.68 × 10−4 2.87 × 10−4

12.4 8.6 22.6

ts were taken for XTCz = 0.91, equivalent circuit model of (a) R(C(R(Q(RW)))) and (b)

lated from a Bode-magnitude plot for R(C(R(Q(RW)))) (Fig. 10a) andR(C(R(Q(RW))))(CR) (Fig. 10b) by using the formula of IZI = 1/C1 or 2.

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hese results show that the copolymer film obtained from thelectrolyte solution for XTCz = 0.83 and 0.91 give the highest C14.12 �F cm−2) for the equivalent circuit of R(C(R(Q(RW)))). How-ver, for R(C(R(Q(RW))))(CR), the highest double layer capacitancesC1 and C2) were obtained as 12.7 �F cm−2 and 2.17 �F cm−2, foroth R(C(R(Q(RW)))) and R(C(R(Q(RW))))(CR) circuit models respec-ively. The highest phase angle was obtained ∼80◦ at the frequencyf 10 mHz.

. Conclusion

In this study, electro-copolymerization and characterizationf poly(TCz-co-Py)/CFME were performed via CV, FTIR-ATR,EM–EDX and EIS. Equivalent circuit models of R(C(R(Q(RW))))nd R(C(R(Q(RW))))(CR) were applied to understand the EIS behav-or of thin polymer film and electrolyte solution. The highestpecific capacitances (Csp = 22.7 mF cm−2 for R(C(R(Q(RW)))) andLF = 22.6 mF cm−2 for R(C(R(Q(RW))))(CR)) and double layer capaci-ances (C1 = 4.12 �F cm−2 for R(C(R(Q(RW)))) and C1 = 12.7 �F cm−2;2 = 2.17 �F cm−2 for R(C(R(Q(RW))))(CR)) were obtained forTCz = 0.91. The FTIR-ATR characteristic peaks of TCz in the copoly-er, SEM images for increasing of mole fraction from XTCz = 0.75 to

.91 and CV measurements via different redox parameters, clearlyndicate the inclusion of TCz into copolymer at XTCz = 0.91. The vari-tion of the capacitance of copolymer is resulted by the changef the mole fractions which is reflected to the equivalent circuitodels (two different circuit models). The electro-activity andell-defined electrochemistry of copolymer on the carbon fibericroelectrode opens the possibility of using these modified elec-

rodes for micro-capacitor and biosensor applications.

cknowledgement

The authors thank Ozlem Oskan (Afyon Kocatepe Univer-ity, Technology and Research Center (TUAM), Afyon, Turkey) forecording the EDX point analysis.

eferences

[1] H.S. Nalwa, Handbook of Organic Conductive Molecules and Polymers, JohnWiley & Sons, New York, 1997.

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