Research Article Influence of Monomer Concentration on the ...Research Article Influence of Monomer...

Research ArticleInfluence of Monomer Concentration on the Morphologies andElectrochemical Properties of PEDOT PANI and PPy Preparedfrom Aqueous Solution

Shalini Kulandaivalu1 Zulkarnain Zainal12 and Yusran Sulaiman13

1Department of Chemistry Faculty of Science Universiti Putra Malaysia 434000 Serdang Selangor Malaysia2Materials Synthesis and Characterization Laboratory Universiti Putra Malaysia (UPM) 43400 Serdang Selangor Malaysia3Functional Device Laboratory Institute of Advanced Technology Universiti Putra Malaysia (UPM)43400 Serdang Selangor Malaysia

Correspondence should be addressed to Yusran Sulaiman yusranupmedumy

Received 19 July 2016 Revised 20 September 2016 Accepted 28 September 2016

Academic Editor Toribio F Otero

Copyright copy 2016 Shalini Kulandaivalu et al This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

Poly(34-ethylenedioxyhiophene) (PEDOT) polyaniline (PANI) and polypyrrole (PPy) were prepared on indium tin oxide (ITO)substrate via potentiostatic from aqueous solutions containing monomer and lithium perchlorateThe concentration of monomerswas varied between 1 and 10mM The effects of monomer concentration on the polymers formation were investigated andcompared by using Fourier transform infrared spectroscopy (FTIR) Raman spectroscopy scanning electron microscopy (SEM)cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements FTIR and Raman spectra showed nochanges in the peaks upon the increment of the concentration Based on the SEM images the increment inmonomer concentrationgives significant effect onmorphologies and eventually affects the electrochemical properties PEDOTelectrodeposited from 10mMsolution showed excellent electrochemical properties with the highest specific capacitance value of 128mFcm2

1 Introduction

Polymers have been well known for a long time for theirexcellent insulating properties Indeed the flow of currentin the polymers was considered as unacceptable occurrenceuntil the concept of the conducting polymers (CPs) has beenreported by Shirakawa and his coworkers [1 2] by the discov-ery of a conducting polymer polyacetylene (PA)Thereby theoverall perspective of polymers has changed and gave a hiketo the development of the conducting polymer As a resultvarious CPs with extended 120587-conjugation have been devel-oped and studied extensively In the series of CP poly(3 4-ethylenedioxyhiophene) (PEDOT) polyaniline (PANI) andpolypyrrole (PPy) have been the forefront of the polymerresearch and were chosen for this work because of theiradvantageous properties

Highlighting the interesting features PEDOT stands outas a CP with high conductivity (ca 300 Scm) and exhibiting

high transparency and satisfactory stability in the doped state[3 4] Apart from that PEDOT shows low redox potentiallow band gap (16ndash17 eV) and excellent chemical stability[5ndash7] Despite this substitution of ethylenedioxythiophenegroup at the 120573 1205731015840 position of the thiophene ring favours thepolymerization that occurs at the 120572 1205721015840 position of the thio-phene ring (Figure 1) resulting in the stable linear chains withfewer defects compared to the thiophene analogous [4] Inaddition the presence of the substituent containing electron-donating oxygen stabilizes the positive charge on the polymerbackbone and lowers the oxidation potential of the monomer[8 9]

In the case of PANI it exists in different oxidation formsbuilt from the repeating unit of benzenoid and quinoid [10]The oxidation level varies from the fully oxidized form toreduced form classified based on the degree of polymeriza-tion [11] Depending on the degree of polymerization PANIappears in leuoemeraldine base (LEB) perningraniline base

Hindawi Publishing CorporationInternational Journal of Polymer ScienceVolume 2016 Article ID 8518293 12 pageshttpdxdoiorg10115520168518293

2 International Journal of Polymer Science

S

O

5

O

S

O O

S

OO

S

O O

120573 or 3 120573 or 3

120572 or 2120572

120572

120572

n

120573998400 or 4

120573998400 120573998400

120573998400 or 4120572998400

120572998400 120572998400 120572998400

or

120573 120573

(a) Poly(34-ethylenedioxythiophene) (PEDOT)

HN

NH

NH

HN

NH

HN

HN

NH

NH

(i)

(ii)

HN

NH

HN120572

120572120572

120572120572

120572120572998400

120572998400120572998400

120572998400120572998400 120572998400

n

n

(b) Structures of polypyrrole (PPy) (i) benzenoid form of PPy (ii) quinoid form of PPy

N N NHn

(c) Emeraldine base form of polyaniline (PANI)

Figure 1 Chemical structures of conducting polymers (a) poly(34-ethylenedioxythiophene) PEDOT (b) PPy and (c) polyaniline PANI

(PAB) and emeraldine base (EB) forms [12] As shown inFigure 1 EB the conducting form of the PANI obtained fromthe doping of the emeraldine salt is composed of benzenoidand quinoid ring alternatively [12 13] Apart from its abilityto change the conductivity by adjusting the oxidation statePANI owns several advantages namely good environmentalstability good electrical conductivity and thermal stability(250∘C) [14 15]

Whereas PPy is made up from repeating unit of pyrrolering structures creating extended 120587-conjugated backbonelong chain [16] the long 120587-conjugated chain could appear inthe form of aromatic or quinoid structure [17] as shown inFigure 1 PPy has excellent features including high conductiv-ity excellent environmental stability good redox reversibilityand ease of synthesis [18 19]

Reviewing the literature most of the research interestson these homopolymers were focused on the electrochemicalpolymerization [20ndash22] due to its ease of synthesis andreproducible properties [23 24] In this present study poten-tiostatic electrochemical polymerization method was usedto investigate and compare the physical and electrochemicalproperties of PEDOT PANI and PPy film which wereprepared in aqueous solution at different concentrationsIndeed there are studies reported on electrochemical poly-merization of these monomers in aqueous or nonaqueous

media However most of the electrochemical polymerizationof EDOT is attempted in organic media due to the lowsolubility of EDOTmonomer (21 gl at 20∘C) in the aqueoussolution [25] Normally polymerization of ANI is performedin acidic media [26 27] and to the best of our knowledgepolymerization of ANI in neutral or basic media is verylimited However water is still an appropriate choice forthe polymerization media considering the environmentalconcern and economical issue Thus this is the key factor tostudy in detail the electropolymerization of these monomersin aqueous solution

2 Experimental

21 ChemicalMaterials 34-Ethylenedioxythiophene (EDOT970) pyrrole (Py) lithium perchlorate (LiClO4 950)potassium ferricyanide K3Fe(CN)6 and potassium ferro-cyanide K4Fe(CN)6 were purchased from Sigma-Aldrichwhile aniline (ANI) and potassium chloride (KCl) wereobtained from the Fisher Scientific ANI and Py were freshlydistilled prior to use while EDOT was used without anyfurther purification All these chemicals were stored in afridge at 4∘Cprior to use All the other chemicals were used asreceived Indium tin oxide (ITO) coated glass was purchasedfrom Xin Yan Technology Limited

International Journal of Polymer Science 3

22 Instrumentation All the electrochemical measurementswere performed using a computer-controlled potentiostatgalvanostat (Autolab 101 NOVA 1916) at room temperaturePerkinElmer Fourier transform infrared (FTIR) spectrom-eter equipped with universal attenuated total reflectance(UATR) accessory was used to study the composition ofthe films The Raman spectra of the films were recordedon Alpha300 R microscopic confocal Raman spectrometer(WITec GmbH) equipped with a 633 nm laser line Surfacemorphology of the films was determined via scanning elec-tron microscope JEOL JSM 6400 and Leo 1455 VP-SEMmodel

23 Potentiostatic Electropolymerization The thin films wereprepared potentiostatically onto ITO glass from aqueoussolution containing monomer ( EDOT ANI or Py) in thepresence of 01MLiClO4 supporting electrolyte at the deposi-tion potential of 10 V versus AgAgCl3MHere three differ-ent concentrations of monomers (1 5 and 10mM) were stud-ied All the electropolymerization processes were performedin one compartment containing three electrodes placed in aFaraday cage to avoid electromagnetic field effect The cellarrangement consists of a working electrode which was ITOcoated glass with a fixed deposition area (1 cm2) a platinumwire as a counter electrode and AgAgCl as a referenceelectrode The working electrodes (ITO glass) were cleanedultrasonically in acetone followed by ethanol and finally indistilled water for 15min each The deionized water (resis-tivity sim182MΩ cm) was used as a solvent to prepare all thesolutions

3 Results and Discussion

31 Potentiostatic Electropolymerization of EDOT ANI andPy Electropolymerization of EDOT ANI and Py werecarried out potentiostatically at fixed applied potential (119864p) of10 V for 300 seconds in a solution containing monomer and01M LiClO4 as supporting electrolyte The concentration ofmonomer in the solutionwas varied (1 5 and 10mM) for eachexperiment The PEDOT films on the surface of the indiumtin oxide (ITO) glass were transparent ldquosky bluerdquo which isin agreement with the reported literature [28] whereas thintransparent greenish PANI film layer and black PPy film layerwere electrodeposited onto the ITO substrate respectively

The chronoamperograms of the PEDOT electropolymer-ized at different concentrations (Figure 2(a)) revealed thatincreasing the concentration of themonomer gives rise to thecurrent This could be due to the increment of the rate of theelectropolymerization of the monomer to become polymerSimilar behaviour was also observed for PANI (Figure 2(b))and PPy (Figure 2(c)) A comparable result has been reportedby the Sadki and Chevrot [29] in their studies for the electro-polymerization of EDOT in the presence of sodium dode-cyl sulphate (SDS) and acid perchloric in methanol-watermedium Furthermore during the experiments it has beennoted that at higher monomer concentration (eg 10mM)the polymer filmswere electrodepositedwith good adherenceon the working electrode surface This result indicates that

the monomer is more easily electropolymerized at a concen-trated solution

It was noticed from the chronoamperogram (Figure 2(a))that there is an increase in the current creating a shoul-der peak for 10mM PEDOT (region (ii)) indicating thenucleation point where the formation of the nuclei on theelectrode surface occurs [30] A similar phenomenon wasalso observed in 5mM and 10 PANI and PPy (Figures 2(b)and 2(c)) However the 1mM PEDOT and 5mM PEDOTchronoamperograms display increment in current with theabsence of nucleation peak followed by a plateau This is thepoint where the first polymer nuclei form (formation of firstactive sites) due to the radical coupling and formation ofoligomers chain [31 32]

In contrast to PEDOT and PPy chronoamperograms ofPANI exhibit a drop in current at the initial stage indicatingthe adsorption and diffusion of ions onto the substrateIt should be noticed that chronoamperograms for 10mMANI were well defined with pronounced peak current whichcorresponds to the nucleation of the ANI This observa-tion indicates that the PANI with better adherence will beformed from the solution containing high concentrations ofmonomer Whereas the absence of increment of current for1mM PANI indicates that no further nucleation process hasoccurred or the polymer growth is stopped at the oligomerstage [30 33] a similar observationwas noticed for 1mMPPy(Figure 2(c)) These results imply that the use of low concen-tration of monomer would not be a good choice for electro-polymerization of the monomer on ITO substrate Howeverhere it is worth mentioning that at a high monomer con-centration (gt10mM) the monomers do not dissolve fully inaqueous solution limiting the concentration factor

As illustrated in Figure 2 the electropolymerizationof these polymers favours the progressive nucleation (PN)instead of instantaneous nucleation (IN) when the monomerconcentration increases from 1mM to 10mM IN describesthe formation of nuclei at the initial stage whereas PNexplains the continuous process of formation of nuclei duringthe polymerization process As explained earlier the incre-ment of concentration induced the formation of nucleiThusbased on the current study it shows that as the concentrationincreases from 1mM to 10mM the rate of formation of nucleiincreases which increases the growth rate [34]

32 Structural Studies

321 Fourier Transform Infrared (FTIR) Spectroscopy Fig-ure 3 illustrates FTIR spectra of PEDOT PANI and PPyprepared from various monomer concentrations and theassignments are tabulated in Table 1 The bands at 1627 cmminus1and 1510 cmminus1 for PEDOT are assigned to asymmetrical andsymmetrical C=C stretching vibration of the thiophene ringunit respectively [35 36] The vibration at 1300 cmminus1 is dueto C-C in ring stretching of the thiophene rings [36] Thevibration modes at 1140 cmminus1 and 1048 cmminus1 are the indica-tion for ethylenedioxy group stretching andC-O-C stretchingof thiophene ring respectively [36 37] The peaks for C-S-Cdeformation were noticed at 928 cmminus1 and 761 cmminus1 [37 38]


(i)

(ii)

00000

00002

00004

00006

00008

00010

Curr

ent (

A)

50 100 150 200 250 3000Time (s)

1mM PEDOT5mM PEDOT10mM PEDOT

(a)

(iii)

1mM PANI5mM PANI10mM PANI

00000

00001

00002

00003

Curr

ent (

A)

50 100 150 200 250 3000Time (s)

(b)

00000

00001

00002

00003

00004

00005

00006

00007

00008

Curr

ent (

A)

50 100 150 200 250 3000Time (s)

00000025

00000030

00000035

00000040

Curr

ent (

A)

50 100 150 200 250 3000

Time (s)

1mM PPy5mM PPy10mM PPy

(c)

Figure 2 Chronoamperograms of (a) PEDOT (b) PANI and (c) PPy films electropolymerized on ITO substrate prepared from 1mM 5mMand 10mMmonomer in 01M LiClO4 at 10 V Inset (c) magnification of chronoamperogram of PPy prepared from 1mMmonomer

However the bands at 1532 cmminus1 and 1628 cmminus1 in PANIspectrum are associated with C=C stretching of the quinoidring and benzenoid rings in PANI structure respectivelyHowever the spectra for 1mM and 5mM PANI (not shown)did not exhibit any bands signifying stretching of C=Cbenzenoid rings indicating ANI did not polymerize to PANIA band at 1450 cmminus1 is assigned to benzene structure of PANI[39] Despite that C-N stretching of secondary aromaticamine is observed at 1310 cmminus1 The peak at wave number1090 cmminus1 represents the vibration for C-H in-plane bendingof the aromatic ring which confirms the benzene rings arebonded at the position 14 in the polymer chain [40] Thebands at the region 700 cmminus1 to 900 cmminus1 are attributed tobending vibration of C-H out of the plane

The FTIR spectra of PPy show bands at 735 cmminus1 and900 cmminus1 attributed to stretching vibration of =C-Hout of theplane Bands at about 1643 cmminus1 and 1532 cmminus1 are due toC-Cstretching vibration of asymmetrical and symmetrical moderespectively [41] However according to spectra for 1mMPPy (Figure S1 in Supplementary Material available onlineat httpdxdoiorg10115520168518293) no C-C stretchingvibrationwas observedThe absence of this band in the regionbetween 1400 cmminus1 and 1700 cmminus1 is evidence for a deficiencyof electropolymerization process of pyrrole at the 1mMmonomer solution Additionally C-H in-plane stretchingvibrations are seen at the position 1300 cmminus1 The bands at1364 cmminus1 and 1100 cmminus1 are the characteristics bands forC-N stretching and N-H in-plane deformation respectively


Table 1 FTIR assignments for the main vibrations of the PEDOT PANI and PPy films

Vibrational wavenumbers (cmminus1) AssignmentsPEDOT PANI PPy761 928 C-S-C deformation1140 Ethylenedioxy group deformation1048 C-O-C stretching1627 C=C (asymmetrical)1510 C=C (symmetrical)1300 C-C

1542 1628 C=C stretching1310 C-N stretching of secondary aromatic amine12001090 C-H in-plane bending of aromatic

700ndash900 C-H out-of-plane deformation1643 C-C stretching (asymmetrical)1532 C-C stretching (symmetrical)1300 C-H in-plane stretching1364 C-N stretching1100 N-H in-plane deformation

600ndash900 =C-H out of plane

(b) PANI

(a) PEDOT

16271510 1300

1140

1048

928761

16281090

710

1643

(c) PPy13001542 1364

1100

Tran

smitt

ance

() 1532 1450

1310

900735

613

1600 1400 1200 1000 800 6001800Wavenumber (cmminus1)

Figure 3 The FTIR-ATR spectra of (a) PEDOT (b) PANI and (c)PPy obtained from solution containing 10mMmonomer and 01MLiClO4

[42] FTIR studies show that the homopolymers were alreadyformed after 300 seconds of electropolymerization at 10 V inan aqueous solution containing 10mMmonomers

322 Raman Spectroscopy Raman spectroscopy is used asthe complementary to FTIR PEDOT spectrum (Figure 4(a))reveals a strong and intense band at 1422 cmminus1 and 1440 cmminus1which is attributable to the symmetrical C120572=C120573 stretchingmode The asymmetric C120572=C120573 stretching mode was noticedat 1515 and 1573 cmminus1 Additionally bands at 1115 1265 and1360 cmminus1 are assigned to C-O-C ring deformation C120572-C1205721015840 interring stretching and C120573-C1205731015840 stretching respectivelywhereas few weak bands were also observed at 520 587 848

Ram

an in

tens

ity (a

u)

520587 848 990698 1115

1265

1360

1422

15151573

1440

608624

815 855

11401255

1359

1513

14581420 1610

1628

984926

1066

11051257

1295

1319 1608

800 1000 1200 1400 1600 1800 2000 2200600Raman shift (cmminus1)

(c) 10mM PPy (10V)

(b) 10mM PANI (10V)

(a) 10mM PEDOT (10V)

Figure 4 Raman spectra for (a) PEDOT (b) PANI and (c) PPyfilmselectropolymerized at 10 V in 10mM monomer containing 01MLiClO4

and 990 cmminus1 which denoted the oxyethylene ring deforma-tion (Table 2) In addition a single peak observed at theposition of 698 cmminus1 represents the symmetrical C120572-S-C1205721015840ring deformation [43] Additionally an important notewor-thy feature in the Raman spectrum is the absence of peaksin the region 650 cm to 680 cm which indicates the resultantPEDOT polymer is in a planar structure [30]

The Raman spectrum of PANI (Figure 4(b)) illustratesthreemain frequency regions which determine the character-istics of the polymer as reported by Mazeikiene et al [44] Aband at 1628 cmminus1 is originated from the stretching vibrations


Table 2 Assignments of the Raman bands for the PEDOT PANI and PPy

Vibrational wavenumbers (cmminus1) AssignmentsPEDOT PANI PPy520 587 848 990 Oxyethylene ring deformation698 C120572-S-C1205721015840 ring deformation1115 C-O-C ring deformation1265 C120572-C1205721015840 interring stretching1360 C120573-C1205731015840 stretching1422 1440 Symmetric C120572=C120573 (stretch)1515 1573 Asymmetric C120572=C120573 stretching

1628 C-C in benzene ring (stretch)1610 C=C in quinone ring (stretch)1513 N-H bending

1458 1440 C=N and CH=CH (stretch)1359 C-N+ polarons (stretch)1255 C-N in benzenoid ring (stretch)1140 C-H in semiquinone ring (bend)855 Benzenoid ring deformation in emeraldine salt815 Quinoid ring deformation

608 624 Benzenoid ring in-plane deformation984 928 Ring deformation1105 1066 Symmetrical C-H in plane bending

1257 Asymmetrical C-H in plane bending1319 1295 Asymmetrical C-N stretching1608 C=C stretching

of C-C in the aromatic ring (benzenoid-type) of PANI poly-mer [44 45] The PANI spectrum shows bands at 1610 cmminus1and 1513 cmminus1 which correspond to the C=C stretching in thequinoid ring and N-H bending respectively [45ndash47] Twosmall bands at the positions 1458 cmminus1 and 1420 cmminus1 areascribed to the C=N and C=C stretching in quinoid rings[48] A band near 1359 cmminus1 associated with the stretching ofC-N+ of radical cations in semiquinone form was observed[46 48] Furthermore a band around 1255 cmminus1 is attributedto C-N in-plane stretching in benzenoid rings [45 48]whereas the vibration of C-H bending in semiquinone ringsis seen at 1140 cmminus1This vibration is due to the oxidized state(emeraldine) of the formed polymer [44] Within the region608 cmminus1 to 855 cmminus1 the ring deformation and ring in-planedeformation bands for the benzenoid ring and quinoid ringwere observed [48]

In the case of PPy films (Figure 4(c)) a band located at1608 cmminus1 is assigned as C=C backbone stretching whereasboth peaks at 1319 and 1295 cmminus1 are originated from asym-metrical C-N stretching mode of the pyrrole ring Further-more a peak positioned at the 1257 cmminus1 is assigned to theasymmetrical C-H in-plane bending As can be seen fromthe spectrum the peak located at 1066 cmminus1 is attributedto symmetrical C-H in-plane bending while the bands forpyrrole ring deformation are seen at the positions 984 cmminus1and 926 cmminus1 The presence of the C-H in-plane deformationpeak proved that oxidized PPy was successfully produced

in this study [49] A sharp peak at 926 and 1105 cmminus1 isassociated with in-plane deformation of the pyrrole bipo-laron structure In addition the bands at the 984 cmminus1 and1066 cmminus1 are related to the polaron pyrrole ring [50 51]

The surface morphologies of the prepared polymer filmswere examined by scanning electronmicroscope (SEM) Dif-ferent morphologies were observed (Figure 5) through elec-tropolymerization of themonomers by varying themonomerconcentration The PEDOT polymer film obtained from theelectrodeposition of 1mM EDOT displays few bulges on thesurface of ITO substrate (Figure 4(a)) In contrast PEDOTfilmprepared from5mMexhibits few globular clusters aggre-gate together forming a thin layer of film Both polymer filmsshow a mixture of small and large nodules in which the ITOsurface is not fully covered Furthermore the comparisonbetween 5mM(Figure 5(b)) and 10mM(Figure 5(c)) PEDOTmicrographs revealed that the nodules are merged togetherfor 10mM PEDOT film forming a compact layer thicklayer and the globular clusters are distributed evenly on thesubstrateThere is an apparent observation on the structure ofPEDOT film at lower magnification (inset Figure 5(c)) whereit shows densely packed and smooth homogeneous film fullycovering the electrode

PANI films prepared from 1mMANI exhibit cylindrical-like shape (Figure 5(d)) However as the concentration isincreased to 5mM the morphology of the films showsloose discrete spherical particle with granular morphology(Figure 5(e)) while PANI prepared from 10mM (Figure 5(f))


(a) (b) (c)

(d) (e) (f)

(g) (h) (i)

Figure 5 SEM micrographs of (a) 1mM PEDOT (b) 5mM PEDOT (c) 10mM PEDOT (d) 1mM PANI (e) 5mM PANI (f) 10mM PANI(g) 1mM PPy (h) 5mM PPy and (i) 10mM PPy

shows granular particles that are evenly distributed on thesurface forming a uniformorderedmorphology Comparisonamong the PPy films prepared at different concentrationsshowed significant different morphology with each othersignifying the importance of the concentration on the elec-tropolymerization process The differences in morphologyof PPy films are visible where 1mM PPy exhibited fewsmall bulges (Figure 5(g)) scattered all over the surface ofthe electrode It is worth noticing that at 1mM PPy filmis not fully covered on the surface of the electrode Incontrast 5mM PPy and 10mM PPy films revealed that bothfilms have homogeneous surface morphology covering thewhole electrode However 5mM PPy shows grain structure(sand type morphology) (Figure 5(h)) while 10mM PPy(Figure 5(i)) illustrates wrinkled surface morphology

Therefore the comparison of the SEM images betweenthe polymers can be made for example 10mM PEDOT

10mMPANI and 10mMPPy showed differentmorphologieseven polymerized at the same concentration Hence themorphologies of the polymers could be controlled by varyingthe concentration of monomer to get the desired structures

33 Electrochemical Properties

331 Cyclic Voltammetry The capacitance properties of theprepared homopolymers were studied using cyclic voltam-metry (CV)The specific capacitances values for the polymerswere calculated according to

119862 =119878

Δ119880 times 120592 times 119860 (1)

where119862 is capacitance 119878 is the enclosed area in the CV curveΔ119880 is the potential window 120592 is the scan rate and119860 is the areaof the electrode


(a) PEDOT(b) PANI(c) PPy

(a)

(b)

(c)

minus04 minus02minus06 02 04 0600Potential (V)

minus00015

minus00010

minus00005

00000

00005

00010

00015

Curr

ent (

A)

Figure 6 CVs of (a) PEDOT (b) PANI and (c) PPy films elec-tropolymerized at from 10mMmonomer concentration recorded in01M KCl solution at the scan rate of 100mVs

Figure 6 shows the typical CV curves of the homopoly-mers and the shapes are different from each other Howeverthe shape of CV for each homopolymer (PANI and PPy) isnot varied significantly (Figure S2) as the concentration isincreased except for the integrated area of the CV curvesThus the changes in the integrated area of the CV curvesindicate the conducting polymers exhibit some differences inthe electrochemical properties

Generally the ideal behaviour of electrical double layer(EDL) capacitor would display a rectangular shaped current-voltage curve (no reduction or oxidation peak) [52 53]However the CV profiles in the present study did not exhibitany rectangular shaped curve Thus this implied that thesynthesized polymers deviate from the pure ideal capacitorproperties The absence of redox peaks in the CVs indicatesonly the nonfaradaic reaction has occurred where deducingthat the capacitive behaviour of the polymer films is basedon the ion adsorption-desorption process at the interface ofelectrode and electrolyte without any chemical reaction [54]

As can be seen from the CV (Figure 6) PPy and PANIshow oblique and narrow CV loop with a small integratedarea of CVs indicating large interfacial contact resistance ofthe film with bulk electrolyte and poor ionic propagationbehaviour of the prepared polymer film [53 55] Howeverit is noticed that the CV of PEDOT (Figure 6(a)) displaysa quasirectangular shape with the large integrated area andno apparent oxidation or reduction peaks suggesting thatthe PEDOT-coated electrodes have excellent electrochemicaldouble layer capacitances [56 57] This observation couldbe related to the structure of the PEDOT films layer withglobular cluster surface morphologies that make the surfacearea higher and eventually increase the adsorption anddesorption process Additionally it was observed that the spe-cific capacitance values (Table 3) for all electropolymerizedhomopolymers are increasing with the increase monomer

concentration Notably the lowest capacitance value wasobtained for homopolymers prepared from 1mM whichcould be due to the inhomogeneous and nonuniform filmdeposited on the substrate

332 Electrochemical Impedance Spectroscopy (EIS) Measure-ments The electrochemical impedance spectroscopy (EIS)is a useful and powerful method that is widely used toprovide data on the electrochemical characteristics such asdouble layer capacitance charge transfer resistance diffusionimpedance and solution resistance [58 59] Impedancespectroscopy consists of a real component and imaginarycomponent and they are measured as a function of the fre-quencyGenerally a small amplitudeACpotential (sinusoidalform) is introduced to the system The response is measuredin the sinusoidal form at the same frequency but shifted in thephase The Nyquist plot is one of the most used impedancespectra to understand the electrochemical responses

The charge transfer characteristics of the homopolymersat different concentrations of the monomers were studiedand the obtained impedance spectra are shown in Figure 7Nyquist plots of PEDOT (Figure 7(a)) films include a semi-circle at high-frequency region followed by a straight lineindicating Warburg diffusion at the low-frequency regionwhereas PANI (Figure 7(b)) exhibits two semicircles followedby aWarburg diffusion at low frequency Nyquist plots of PPyexhibit similar pattern as PANI however the disappearanceof Warburg element at the concentration of 5mM is worthnoticing and indicating poor ion diffusion from the bulksolution to the polymer surface which could lead to highresistance of charge transferThis electrochemical system canbe modelled according to the equivalent circuits (Figure 8)which are used to fit the experimental data The informationobtained from the equivalent circuits is in agreement withthe data interpreted from the Nyquist plots The accuracyof the fitted data with the plot is determined based on thechi-square (1205942) that represents the sum of the square of thedifferences between theoretical and experimental points andalso limiting the percentage error in the value of each elementin the equivalent circuits to a minimum [60] The values ofthe 1205942 in the current work are in the range of 10minus2 to 10minus3indicating good fitting

Three different equivalent circuits for the resultanthomopolymers are proposed to investigate the electrochem-ical properties of the homopolymers (Figure 8) The equiv-alent circuits consist of the bulk solution resistance (119877s)charge transfer resistance between polymer coated electrodeand electrolyte (119877ct) the resistance of the polymer film (119877p)constant phase element (CPE) and the ldquoclassicalrdquo infinite-lengthWarburg diffusion element (119885W)The119877ct values can becalculated from the diameter of the semicircle obtained fromthe Nyquist plots [61] In these models CPE is used [62] inthe circuits replacing the double layer capacitor 119862dl due tothe nonhomogenous and irregular geometry morphologiesof the homopolymers (as shown in the SEM images) CPErefers to the double layer capacitance and faradaic pseudoca-pacitance which express the nonideal behaviour of 119862dl [63]Additionally it is worth noting that the Warburg element is


Fitted linePEDOT 1mMPEDOT 5mM

PEDOT 10mM

70 80 90 100 110 120 130 140 15060Z998400 (Ohm)

0

5

10

15

20

25

30

35

40

minusZ998400998400

(Ohm

)

(a)

Fitted line

0

5000

10000

15000

20000

minusZ998400998400

(Ohm

)

10000 20000 30000 40000 500000Z998400 (Ohm)

1mM PANI5mM PANI

10 mM PANI

150 200100Z998400 (Ohm)

20

40

60

80

minusZ998400998400

(Ohm

)

(b)

Fitted line

200 400 600 800 1000 12000Z998400 (Ohm)

0

100

200

300

400

500

minusZ998400998400

(Ohm

)

150100Z998400 (Ohm)

0

20

40

60

minusZ998400998400

(Ohm

)

1mM PPy5mM PPy

10 mM PPy

(c)

Figure 7 Nyquist plot of (a) PEDOT (b) PANI and (c) PPy deposited from the solution containing different monomer concentration onthe ITO glass at 10 V The solid lines represent the best fitting according to the equivalent circuits (Inset magnification of Nyquist plot athigh-frequency region)

Table 3 Electrochemical properties obtained from fitting data of Nyquist plots

Concentration (mM) PEDOT PANI PPy119862sp (mFcm2) 119877ct (Ω) 120594

2 (10minus3) 119862sp (mFcm2) 119877ct (Ω) 1205942 (10minus3) 119862sp (mFcm2) 119877ct (Ω) 120594

2 (10minus3)1mM 054 926 022 006 688 k 2061 001 13450 11145mM 857 1282 110 046 3111 k 1102 010 89021 280510mM 128 2172 567 062 1185 k 850 011 10311 291


W

CPE

Rs

Rct

(a)

W

CPE CPE

Rs

RctRp

(b)

CPE CPE

Rs

RctRp

(c)

Figure 8 Equivalent circuits used in the fitting of the impedance results (a) PEDOT (b) PANI 1mM PPy and 10mM PPy and (c) 5mMPPy

not included in the circuits for PPy films except for 1mM and10mM PPy film

Based on Table 3 the 119877ct values for PEDOT filmsincrease with the increasing of monomer concentrationThisphenomenon could be related to the morphology differencesof the PEDOT As can be seen from the SEM images ofPEDOT (Figure 5) at 1mM few bulges on the substrate werenoticed and compact thick globular structures were obtainedat 10mM The globular structure has a high surface area forion adsorption-desorption process however the thicker layerslows down the process which eventually increases the resis-tance for charge carriers

The 119877ct values for PANI and PPy increase with con-centration (from 688 kΩ and 13450Ω at 1mM to 3111 kΩand 89021Ω at 5mM for PANI and PPy films resp) beforedecreasing at 10mM It is expected that the changes in themorphology have affected the charge transfer at the interfaceAt the concentration of 1mM PANI film exhibit cylindricalshaped structures and formed a loose discrete spherical par-ticle with granular morphology at 5mM (Figure 5(d)) How-ever when the concentration of ANI is increased to 10mMa film with compact granular particles was observed whichimproves the accessibility of the electrolyte and subsequentlyreduce the charge transfer Similarly in the case of PPy at1mM the film shows small bulgesmorphology on the surfaceWhen the concentration is increased to 5mM Py and 10mMPy the films reveal grain structure (sand type structure)and compact layer with wrinkled surface morphology It isexpected that wrinkled surface provides more active sites forrapid ion diffusion which reduces the resistance of chargetransfer

The work carried out on polybenzidine by Muslim et al[64] also showed that different monomer concentrationaffects the morphology structure and electrochemical activ-ities which is consistent with results of the current study

whereas in another study conducted by Ates [65] revealedthat the initial monomer concentration influenced the capac-itive properties of poly(3-methylthiophene)

4 Conclusion

Comparison of PEDOT PANI and PPy polymer films on theeffect of concentration was presented in this work FTIR andRaman spectra confirm the presence of polymers on ITO sub-strate SEM analysis revealed significant differences in mor-phologies of the polymers as the concentration is increasedThe polymers electropolymerized from 10mM monomersolution display a homogenous formation of the film Thedifferences in the polymer morphologies prepared fromdifferent concentrations eventually affect the electrochemicalproperties

Competing Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by a Universiti Putra Malaysiaresearch grant (no GP-IPS20139399838)

References

[1] H Shirakawa E J Louis A G MacDiarmid C K Chiangand A J Heeger ldquoSynthesis of electrically conducting organicpolymers halogen derivatives of polyacetylene (CH)119909rdquo Journalof the Chemical Society Chemical Communications no 16 pp578ndash580 1977


[2] H Shirakawa ldquoThe discovery of polyacetylene film the dawn-ing of an era of conducting polymers (Nobel Lecture)rdquo Ange-wandte ChemiemdashInternational Edition vol 40 no 14 pp 2575ndash2580 2001

[3] K Cysewska J Karczewski and P Jasinski ldquoInfluence ofelectropolymerization conditions on the morphological andelectrical properties of PEDOT filmrdquo Electrochimica Acta vol176 Article ID 25282 pp 156ndash161 2015

[4] L Groenendaal F Jonas D Freitag H Pielartzik and J RReynolds ldquoPoly(34-ethylenedioxythiophene) and its deriva-tives past present and futurerdquo Advanced Materials vol 12 no7 pp 481ndash494 2000

[5] S Kulandaivalu Z Zainal and Y Sulaiman ldquoA New Approachfor Electrodeposition of poly (3 4-ethylenedioxythiophene)polyaniline (PEDOTPANI)Copolymerrdquo International Journalof Electrochemical Science vol 10 no 11 pp 8926ndash8940 2015

[6] D S Patil S A Pawar J H Kim P S Patil and J C Shin ldquoFacilepreparation and enhanced capacitance of the Ag-PEDOTPSSpolyaniline nanofiber network for supercapacitorsrdquo Electrochi-mica Acta vol 213 pp 680ndash690 2016

[7] D S Patil S A Pawar J Hwang J H Kim P S Patil and JC Shin ldquoSilver incorporated PEDOT PSS for enhanced elec-trochemical performancerdquo Journal of Industrial and EngineeringChemistry vol 42 pp 113ndash120 2016

[8] M S Ahmed H Jeong J-M You and S Jeon ldquoSynthesisand characterization of an electrochromic copolymer basedon 22101584051015840210158401015840-terthiophene and 34-ethylenedioxythiophenerdquoApplied Nanoscience vol 2 no 2 pp 133ndash141 2012

[9] H J Ahonen J Lukkari and J Kankare ldquon- and p-dopedpoly(34-ethylenedioxythiophene) two electronically conduct-ing states of the polymerrdquo Macromolecules vol 33 no 18 pp6787ndash6793 2000

[10] S K Dhawan D Kumar M K Ram S Chandra and DC Trivedi ldquoApplication of conducting polyaniline as sensormaterial for ammoniardquo Sensors and Actuators B Chemical vol40 no 2-3 pp 99ndash103 1997

[11] D Geethalakshmi N Muthukumarasamy and R Balasun-daraprabhu ldquoMeasurement on the structural morphologicalelectrical and optical properties of PANI-CSA nanofilmsrdquoMeasurement vol 92 pp 446ndash452 2016

[12] M Jaymand ldquoRecent progress in chemical modification ofpolyaniline Dedicated to Professor Dr Ali Akbar EntezamirdquoProgress in Polymer Science vol 38 no 9 pp 1287ndash1306 2013

[13] S Bhadra D Khastgir N K Singha and J H Lee ldquoProgress inpreparation processing and applications of polyanilinerdquo Prog-ress in Polymer Science vol 34 no 8 pp 783ndash810 2009

[14] H Kawashima and H Goto ldquoPreparation and properties ofpolyaniline in the presence of trehaloserdquo Soft NanoscienceLetters vol 1 no 3 pp 71ndash75 2011

[15] L Ma L Su J Zhang et al ldquoA controllable morphology GOPANImetal hydroxide composite for supercapacitorrdquo Journalof Electroanalytical Chemistry vol 777 pp 75ndash84 2016

[16] Y Wei J Tian and D Yang ldquoA newmethod for polymerizationof pyrrole and derivativesrdquoDieMakromolekulare Chemie RapidCommunications vol 12 no 11 pp 617ndash623 1991

[17] P SavillePolypyrrole Formation andUse DefenceResearch andDevelopment Atlantic Dartmouth Dartmouth Canada 2005

[18] N LiD Shan andHXue ldquoElectrochemical synthesis and char-acterization of poly(pyrrole-co-tetrahydrofuran) conductingcopolymerrdquo European Polymer Journal vol 43 no 6 pp 2532ndash2539 2007

[19] R A Jeong G J Lee H S Kim K Ahn K Lee and K HKim ldquoPhysicochemical properties of electrochemically pre-pared polypyrrole perchloraterdquo Synthetic Metals vol 98 no 1pp 9ndash15 1998

[20] T Patois B Lakard S Monney X Roizard and P FievetldquoCharacterization of the surface properties of polypyrrole filmsInfluence of electrodeposition parametersrdquo Synthetic Metalsvol 161 no 21-22 pp 2498ndash2505 2011

[21] K M Ziadan and W T Saadon ldquoStudy of the electrical char-acteristics of polyaniline prepeared by electrochemical poly-merizationrdquo Energy Procedia vol 19 pp 71ndash79 2012

[22] X Meng Z Wang L Wang M Pei W Guo and X TangldquoElectrosynthesis of pure poly(34-ethylenedioxythiophene)(PEDOT) in chitosan-based liquid crystal phaserdquo ElectronicMaterials Letters vol 9 no 5 pp 605ndash608 2013

[23] T Darmanin and F Guittard ldquoSuperhydrophobic surface prop-erties with various nanofibrous structures by electrodepositionof PEDOT polymers with short fluorinated chains and rigidspacersrdquo Synthetic Metals vol 205 pp 58ndash63 2015

[24] M Gerard A Chaubey and B D Malhotra ldquoApplication ofconducting polymers to biosensorsrdquoBiosensors and Bioelectron-ics vol 17 no 5 pp 345ndash359 2002

[25] Z Qi and P G Pickup ldquoHigh performance conducting polymersupported oxygen reduction catalystsrdquo Chemical Communica-tions no 21 pp 2299ndash2300 1998

[26] J Zang Y Wang X Zhao et al ldquoElectrochemical synthesis ofpolyaniline on nanodiamond powderrdquo International Journal ofElectrochemical Science vol 7 no 2 pp 1677ndash1687 2012

[27] A Kellenberger D Ambros andN Plesu ldquoScan rate dependentmorphology of polyaniline films electrochemically depositedon nickelrdquo International Journal of Electrochemical Science vol9 no 12 pp 6821ndash6833 2014

[28] Y Xiao X Cui J M Hancock M Bouguettaya J RReynolds and D C Martin ldquoElectrochemical polymeriza-tion of poly(hydroxymethylated-34-ethylenedioxythiophene)(PEDOT-MeOH) on multichannel neural probesrdquo Sensors andActuators B Chemical vol 99 no 2-3 pp 437ndash443 2004

[29] S Sadki and C Chevrot ldquoElectropolymerization of 34-ethylen-edioxythiophene N-ethylcarbazole and their mixtures in aque-ous micellar solutionrdquo Electrochimica Acta vol 48 no 6 pp733ndash739 2003

[30] N Sakmeche S Aeiyach J-J Aaron M Jouini J C Lacroixand P-C Lacaze ldquoImprovement of the electrosynthesis andphysicochemical properties of poly(34-ethylenedioxythioph-ene) using a sodium dodecyl sulfate micellar aqueousmediumrdquoLangmuir vol 15 no 7 pp 2566ndash2574 1999

[31] L Pigani A Heras A Colina R Seeber and J Lopez-PalaciosldquoElectropolymerisation of 34-ethylenedioxythiophene in aque-ous solutionsrdquo Electrochemistry Communications vol 6 no 11pp 1192ndash1198 2004

[32] H Randriamahazaka V Noel and C Chevrot ldquoNucleation andgrowth of poly(34-ethylenedioxythiophene) in acetonitrile onplatinum under potentiostatic conditionsrdquo Journal of Electroan-alytical Chemistry vol 472 no 2 pp 103ndash111 1999

[33] S Patra K Barai and N Munichandraiah ldquoScanning electronmicroscopy studies of PEDOT prepared by various electro-chemical routesrdquo Synthetic Metals vol 158 no 10 pp 430ndash4352008

[34] S Bijani R Schrebler E A Dalchiele M Gabas L Martınezand J R Ramos-Barrado ldquoStudy of the nucleation and growth


mechanisms in the electrodeposition of micro- and nanostruc-tured Cu2O thin filmsrdquoThe Journal of Physical Chemistry C vol115 no 43 pp 21373ndash21382 2011

[35] G Shumakovich G Otrokhov I Vasilrsquoeva D Pankratov OMorozova and A Yaropolov ldquoLaccase-mediated polymeriza-tion of 34-ethylenedioxythiophene (EDOT)rdquo Journal of Molec-ular Catalysis B Enzymatic vol 81 pp 66ndash68 2012

[36] Y-J TaoH-F ChengW-WZheng Z-Y Zhang andD-Q LiuldquoElectrosynthesises and characterizations of copolymers basedon pyrrole and 34-ethylenedioxythiophene in aqueousmicellarsolutionrdquo Synthetic Metals vol 162 no 7-8 pp 728ndash734 2012

[37] C Li and T Imae ldquoElectrochemical and Optical Properties ofthe Poly(34- ethylenedioxythiophene) film electropolymerizedin an aqueous sodium dodecyl sulfate and lithium tetrafluo-roborate mediumrdquoMacromolecules vol 37 no 7 pp 2411ndash24162004

[38] K Zhang J Xu X Zhu et al ldquoPoly(34-ethylenedioxythio-phene) nanorods grown on graphene oxide sheets as electro-chemical sensing platform for rutinrdquo Journal of ElectroanalyticalChemistry vol 739 pp 66ndash72 2015

[39] N-A Rangel-Vazquez C Sanchez-Lopez and F R FelixldquoSpectroscopy analyses of polyurethanepolyaniline IPN usingcomputational simulation (Amber MM+ and PM3 method)rdquoPolımeros vol 24 no 4 pp 453ndash463 2014

[40] A Kellenberger EDmitrieva and LDunsch ldquoThe stabilizationof charged states at phenazine-like units in polyaniline underp-doping an in situ ATR-FTIR spectroelectrochemical studyrdquoPhysical Chemistry Chemical Physics vol 13 no 8 pp 3411ndash3420 2011

[41] F F Bruno S A Fossey S Nagarajan R Nagarajan J Kumarand L A Samuelson ldquoBiomimetic synthesis of water-solubleconducting copolymershomopolymers of pyrrole and 34-ethylenedioxythiophenerdquo Biomacromolecules vol 7 no 2 pp586ndash589 2006

[42] S Cetiner H Karakas R Ciobanu et al ldquoPolymerizationof pyrrole derivatives on polyacrylonitrile matrix FTIR-ATRand dielectric spectroscopic characterization of composite thinfilmsrdquo Synthetic Metals vol 160 no 11-12 pp 1189ndash1196 2010

[43] S Garreau J L Duvail and G Louarn ldquoSpectroelectrochem-ical studies of poly(34-ethylenedioxythiophene) in aqueousmediumrdquo Synthetic Metals vol 125 no 3 pp 325ndash329 2001

[44] R Mazeikiene G Niaura and A Malinauskas ldquoChemicaloxidation of aniline and N-methylaniline a kinetic study byRaman spectroscopyrdquo Spectrochimica Acta Part A Molecularand Biomolecular Spectroscopy vol 106 pp 34ndash40 2013

[45] U Bogdanovic V V Vodnik S P Ahrenkiel M Stoiljkovic GCiric-Marjanovic and J M Nedeljkovic ldquoInterfacial synthesisand characterization of goldpolyaniline nanocompositesrdquo Syn-thetic Metals vol 195 pp 122ndash131 2014

[46] M Jain and S Annapoorni ldquoRaman study of polyaniline nano-fibers prepared by interfacial polymerizationrdquo Synthetic Metalsvol 160 no 15-16 pp 1727ndash1732 2010

[47] K A Ibrahim ldquoSynthesis and characterization of polyanilineand poly(aniline-co-o-nitroaniline) using vibrational spectro-scopyrdquo Arabian Journal of Chemistry 2013

[48] T Lindfors and A Ivaska ldquoRaman based pH measurementswith polyanilinerdquo Journal of Electroanalytical Chemistry vol580 no 2 pp 320ndash329 2005

[49] Y Furukawa S Tazawa Y Fujii and I Harada ldquoRaman spectraof polypyrrole and its 25-13C-substituted and C-deuteratedanalogues in doped and undoped statesrdquo Synthetic Metals vol24 no 4 pp 329ndash341 1988

[50] M Li J Yuan andG Shi ldquoElectrochemical fabrication of nano-porous polypyrrole thin filmsrdquoThin Solid Films vol 516 no 12pp 3836ndash3840 2008

[51] J Duchet R Legras and S Demoustier-Champagne ldquoChemi-cal synthesis of polypyrrole structure-properties relationshiprdquoSynthetic Metals vol 98 no 2 pp 113ndash122 1998

[52] B E Conway ldquoCapacitance behavior of films of conductingelectrochemically reactive polymersrdquo in Electrochemical Super-capacitors Scientific Fundamentals and Technological Applica-tions pp 299ndash334 Springer Berlin Germany 1999

[53] P Si S Ding X-W Lou and D-H Kim ldquoAn electrochemi-cally formed three-dimensional structure of polypyrrolegra-phene nanoplatelets for high-performance supercapacitorsrdquoRSC Advances vol 1 no 7 pp 1271ndash1278 2011

[54] C-W Liew S Ramesh and A K Arof ldquoCharacterization ofionic liquid added poly(vinyl alcohol)-based proton conductingpolymer electrolytes and electrochemical studies on the super-capacitorsrdquo International Journal of Hydrogen Energy vol 40no 1 pp 852ndash862 2015

[55] B E Conway ldquoElectrochemical supercapacitorsrdquo in ScientificFundamentals and Technological Applications Springer BerlinGermany 1999

[56] WChen R B Rakhi andHN Alshareef ldquoHigh energy densitysupercapacitors usingmacroporous kitchen spongesrdquo Journal ofMaterials Chemistry vol 22 no 29 pp 14394ndash14402 2012

[57] X Feng N Chen Y Zhang et al ldquoThe self-assembly ofshape controlled functionalized graphene-MnO2 compositesfor application as supercapacitorsrdquo Journal of Materials Chem-istry A vol 2 no 24 pp 9178ndash9184 2014

[58] B E Conway J O M Bockris R White et al ldquoElectrochem-ical impedance spectroscopy and its applicationsrdquo in ModernAspects of Electrochemistry Modern Aspects of Electrochem-istry pp 143ndash248 Springer Berlin Germany 2002

[59] M Ates ldquoReview study of electrochemical impedance spectro-scopy and equivalent electrical circuits of conducting polymerson carbon surfacesrdquo Progress in Organic Coatings vol 71 no 1pp 1ndash10 2011

[60] S Chaudhari and P P Patil ldquoInhibition of nickel coatedmild steel corrosion by electrosynthesized polyaniline coatingsrdquoElectrochimica Acta vol 56 no 8 pp 3049ndash3059 2011

[61] N FAtta AGalal andRAAhmed ldquoPoly(34-ethylene-dioxy-thiophene) electrode for the selective determination of dopa-mine in presence of sodium dodecyl sulfaterdquo Bioelectrochem-istry vol 80 no 2 pp 132ndash141 2011

[62] C-C Hu and C-H Chu ldquoElectrochemical impedance char-acterization of polyaniline-coated graphite electrodes for elec-trochemical capacitorsmdasheffects of film coveragethickness andanionsrdquo Journal of Electroanalytical Chemistry vol 503 no 1-2pp 105ndash116 2001

[63] W-C Chen T-C Wen and A Gopalan ldquoNegative capacitancefor polyaniline an analysis via electrochemical impedancespectroscopyrdquo SyntheticMetals vol 128 no 2 pp 179ndash189 2002

[64] A Muslim D Malik and A A Rexit ldquoEffects of monomerconcentration on the structure and properties of polybenzidinemicro rodsrdquo Polymer Science Series B vol 54 no 11 pp 518ndash5242012

[65] M Ates ldquoMonomer concentration effects of poly (3-methyl-thiopene) on electrochemical impedance spectroscopyrdquo Inter-national Journal of Electrochemical Science vol 4 no 7 pp1004ndash1014 2009

Submit your manuscripts athttpwwwhindawicom

ScientificaHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

CorrosionInternational Journal of

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Polymer ScienceInternational Journal of



CeramicsJournal of


CompositesJournal of

NanoparticlesJournal of



International Journal of

Biomaterials


NanoscienceJournal of

TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


S

O

5

O

S

O O

S

OO

S

O O

120573 or 3 120573 or 3

120572 or 2120572

120572

120572

n

120573998400 or 4

120573998400 120573998400

120573998400 or 4120572998400

120572998400 120572998400 120572998400

or

120573 120573

(a) Poly(34-ethylenedioxythiophene) (PEDOT)

HN

NH

NH

HN

NH

HN

HN

NH

NH

(i)

(ii)

HN

NH

HN120572

120572120572

120572120572

120572120572998400

120572998400120572998400

120572998400120572998400 120572998400

n

n

(b) Structures of polypyrrole (PPy) (i) benzenoid form of PPy (ii) quinoid form of PPy

N N NHn

(c) Emeraldine base form of polyaniline (PANI)

Figure 1 Chemical structures of conducting polymers (a) poly(34-ethylenedioxythiophene) PEDOT (b) PPy and (c) polyaniline PANI

(PAB) and emeraldine base (EB) forms [12] As shown inFigure 1 EB the conducting form of the PANI obtained fromthe doping of the emeraldine salt is composed of benzenoidand quinoid ring alternatively [12 13] Apart from its abilityto change the conductivity by adjusting the oxidation statePANI owns several advantages namely good environmentalstability good electrical conductivity and thermal stability(250∘C) [14 15]

Whereas PPy is made up from repeating unit of pyrrolering structures creating extended 120587-conjugated backbonelong chain [16] the long 120587-conjugated chain could appear inthe form of aromatic or quinoid structure [17] as shown inFigure 1 PPy has excellent features including high conductiv-ity excellent environmental stability good redox reversibilityand ease of synthesis [18 19]

Reviewing the literature most of the research interestson these homopolymers were focused on the electrochemicalpolymerization [20ndash22] due to its ease of synthesis andreproducible properties [23 24] In this present study poten-tiostatic electrochemical polymerization method was usedto investigate and compare the physical and electrochemicalproperties of PEDOT PANI and PPy film which wereprepared in aqueous solution at different concentrationsIndeed there are studies reported on electrochemical poly-merization of these monomers in aqueous or nonaqueous

media However most of the electrochemical polymerizationof EDOT is attempted in organic media due to the lowsolubility of EDOTmonomer (21 gl at 20∘C) in the aqueoussolution [25] Normally polymerization of ANI is performedin acidic media [26 27] and to the best of our knowledgepolymerization of ANI in neutral or basic media is verylimited However water is still an appropriate choice forthe polymerization media considering the environmentalconcern and economical issue Thus this is the key factor tostudy in detail the electropolymerization of these monomersin aqueous solution

2 Experimental

21 ChemicalMaterials 34-Ethylenedioxythiophene (EDOT970) pyrrole (Py) lithium perchlorate (LiClO4 950)potassium ferricyanide K3Fe(CN)6 and potassium ferro-cyanide K4Fe(CN)6 were purchased from Sigma-Aldrichwhile aniline (ANI) and potassium chloride (KCl) wereobtained from the Fisher Scientific ANI and Py were freshlydistilled prior to use while EDOT was used without anyfurther purification All these chemicals were stored in afridge at 4∘Cprior to use All the other chemicals were used asreceived Indium tin oxide (ITO) coated glass was purchasedfrom Xin Yan Technology Limited














(i)

(ii)

00000

00002

00004

00006

00008

00010

Curr

ent (

A)

50 100 150 200 250 3000Time (s)


(a)

(iii)


00000

00001

00002

00003

Curr

ent (

A)

50 100 150 200 250 3000Time (s)

(b)

00000

00001

00002

00003

00004

00005

00006

00007

00008

Curr

ent (

A)

50 100 150 200 250 3000Time (s)

00000025

00000030

00000035

00000040

Curr

ent (

A)

50 100 150 200 250 3000

Time (s)


(c)










(b) PANI

(a) PEDOT

16271510 1300

1140

1048

928761

16281090

710

1643

(c) PPy13001542 1364

1100

Tran

smitt

ance

() 1532 1450

1310

900735

613





Ram

an in

tens

ity (a

u)

520587 848 990698 1115

1265

1360

1422

15151573

1440

608624

815 855

11401255

1359

1513

14581420 1610

1628

984926

1066

11051257

1295

1319 1608


(c) 10mM PPy (10V)

(b) 10mM PANI (10V)


















(a) (b) (c)

(d) (e) (f)

(g) (h) (i)







119862 =119878

Δ119880 times 120592 times 119860 (1)




(a)

(b)

(c)


minus00015

minus00010

minus00005

00000

00005

00010

00015

Curr

ent (

A)











PEDOT 10mM

70 80 90 100 110 120 130 140 15060Z998400 (Ohm)

0

5

10

15

20

25

30

35

40

minusZ998400998400

(Ohm

)

(a)

Fitted line

0

5000

10000

15000

20000

minusZ998400998400

(Ohm

)

10000 20000 30000 40000 500000Z998400 (Ohm)

1mM PANI5mM PANI

10 mM PANI

150 200100Z998400 (Ohm)

20

40

60

80

minusZ998400998400

(Ohm

)

(b)

Fitted line

200 400 600 800 1000 12000Z998400 (Ohm)

0

100

200

300

400

500

minusZ998400998400

(Ohm

)

150100Z998400 (Ohm)

0

20

40

60

minusZ998400998400

(Ohm

)

1mM PPy5mM PPy

10 mM PPy

(c)





2 (10minus3)1mM 054 926 022 006 688 k 2061 001 13450 11145mM 857 1282 110 046 3111 k 1102 010 89021 280510mM 128 2172 567 062 1185 k 850 011 10311 291


W

CPE

Rs

Rct

(a)

W

CPE CPE

Rs

RctRp

(b)

CPE CPE

Rs

RctRp

(c)







4 Conclusion


Competing Interests


Acknowledgments


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials
















(i)

(ii)

00000

00002

00004

00006

00008

00010

Curr

ent (

A)

50 100 150 200 250 3000Time (s)


(a)

(iii)


00000

00001

00002

00003

Curr

ent (

A)

50 100 150 200 250 3000Time (s)

(b)

00000

00001

00002

00003

00004

00005

00006

00007

00008

Curr

ent (

A)

50 100 150 200 250 3000Time (s)

00000025

00000030

00000035

00000040

Curr

ent (

A)

50 100 150 200 250 3000

Time (s)


(c)










(b) PANI

(a) PEDOT

16271510 1300

1140

1048

928761

16281090

710

1643

(c) PPy13001542 1364

1100

Tran

smitt

ance

() 1532 1450

1310

900735

613





Ram

an in

tens

ity (a

u)

520587 848 990698 1115

1265

1360

1422

15151573

1440

608624

815 855

11401255

1359

1513

14581420 1610

1628

984926

1066

11051257

1295

1319 1608


(c) 10mM PPy (10V)

(b) 10mM PANI (10V)


















(a) (b) (c)

(d) (e) (f)

(g) (h) (i)







119862 =119878

Δ119880 times 120592 times 119860 (1)




(a)

(b)

(c)


minus00015

minus00010

minus00005

00000

00005

00010

00015

Curr

ent (

A)











PEDOT 10mM

70 80 90 100 110 120 130 140 15060Z998400 (Ohm)

0

5

10

15

20

25

30

35

40

minusZ998400998400

(Ohm

)

(a)

Fitted line

0

5000

10000

15000

20000

minusZ998400998400

(Ohm

)

10000 20000 30000 40000 500000Z998400 (Ohm)

1mM PANI5mM PANI

10 mM PANI

150 200100Z998400 (Ohm)

20

40

60

80

minusZ998400998400

(Ohm

)

(b)

Fitted line

200 400 600 800 1000 12000Z998400 (Ohm)

0

100

200

300

400

500

minusZ998400998400

(Ohm

)

150100Z998400 (Ohm)

0

20

40

60

minusZ998400998400

(Ohm

)

1mM PPy5mM PPy

10 mM PPy

(c)





2 (10minus3)1mM 054 926 022 006 688 k 2061 001 13450 11145mM 857 1282 110 046 3111 k 1102 010 89021 280510mM 128 2172 567 062 1185 k 850 011 10311 291


W

CPE

Rs

Rct

(a)

W

CPE CPE

Rs

RctRp

(b)

CPE CPE

Rs

RctRp

(c)







4 Conclusion


Competing Interests


Acknowledgments


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials









(b) PANI

(a) PEDOT

16271510 1300

1140

1048

928761

16281090

710

1643

(c) PPy13001542 1364

1100

Tran

smitt

ance

() 1532 1450

1310

900735

613





Ram

an in

tens

ity (a

u)

520587 848 990698 1115

1265

1360

1422

15151573

1440

608624

815 855

11401255

1359

1513

14581420 1610

1628

984926

1066

11051257

1295

1319 1608


(c) 10mM PPy (10V)

(b) 10mM PANI (10V)


















(a) (b) (c)

(d) (e) (f)

(g) (h) (i)







119862 =119878

Δ119880 times 120592 times 119860 (1)




(a)

(b)

(c)


minus00015

minus00010

minus00005

00000

00005

00010

00015

Curr

ent (

A)











PEDOT 10mM

70 80 90 100 110 120 130 140 15060Z998400 (Ohm)

0

5

10

15

20

25

30

35

40

minusZ998400998400

(Ohm

)

(a)

Fitted line

0

5000

10000

15000

20000

minusZ998400998400

(Ohm

)

10000 20000 30000 40000 500000Z998400 (Ohm)

1mM PANI5mM PANI

10 mM PANI

150 200100Z998400 (Ohm)

20

40

60

80

minusZ998400998400

(Ohm

)

(b)

Fitted line

200 400 600 800 1000 12000Z998400 (Ohm)

0

100

200

300

400

500

minusZ998400998400

(Ohm

)

150100Z998400 (Ohm)

0

20

40

60

minusZ998400998400

(Ohm

)

1mM PPy5mM PPy

10 mM PPy

(c)





2 (10minus3)1mM 054 926 022 006 688 k 2061 001 13450 11145mM 857 1282 110 046 3111 k 1102 010 89021 280510mM 128 2172 567 062 1185 k 850 011 10311 291


W

CPE

Rs

Rct

(a)

W

CPE CPE

Rs

RctRp

(b)

CPE CPE

Rs

RctRp

(c)







4 Conclusion


Competing Interests


Acknowledgments


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials
















(a) (b) (c)

(d) (e) (f)

(g) (h) (i)







119862 =119878

Δ119880 times 120592 times 119860 (1)




(a)

(b)

(c)


minus00015

minus00010

minus00005

00000

00005

00010

00015

Curr

ent (

A)











PEDOT 10mM

70 80 90 100 110 120 130 140 15060Z998400 (Ohm)

0

5

10

15

20

25

30

35

40

minusZ998400998400

(Ohm

)

(a)

Fitted line

0

5000

10000

15000

20000

minusZ998400998400

(Ohm

)

10000 20000 30000 40000 500000Z998400 (Ohm)

1mM PANI5mM PANI

10 mM PANI

150 200100Z998400 (Ohm)

20

40

60

80

minusZ998400998400

(Ohm

)

(b)

Fitted line

200 400 600 800 1000 12000Z998400 (Ohm)

0

100

200

300

400

500

minusZ998400998400

(Ohm

)

150100Z998400 (Ohm)

0

20

40

60

minusZ998400998400

(Ohm

)

1mM PPy5mM PPy

10 mM PPy

(c)





2 (10minus3)1mM 054 926 022 006 688 k 2061 001 13450 11145mM 857 1282 110 046 3111 k 1102 010 89021 280510mM 128 2172 567 062 1185 k 850 011 10311 291


W

CPE

Rs

Rct

(a)

W

CPE CPE

Rs

RctRp

(b)

CPE CPE

Rs

RctRp

(c)







4 Conclusion


Competing Interests


Acknowledgments


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





(a)

(b)

(c)


minus00015

minus00010

minus00005

00000

00005

00010

00015

Curr

ent (

A)











PEDOT 10mM

70 80 90 100 110 120 130 140 15060Z998400 (Ohm)

0

5

10

15

20

25

30

35

40

minusZ998400998400

(Ohm

)

(a)

Fitted line

0

5000

10000

15000

20000

minusZ998400998400

(Ohm

)

10000 20000 30000 40000 500000Z998400 (Ohm)

1mM PANI5mM PANI

10 mM PANI

150 200100Z998400 (Ohm)

20

40

60

80

minusZ998400998400

(Ohm

)

(b)

Fitted line

200 400 600 800 1000 12000Z998400 (Ohm)

0

100

200

300

400

500

minusZ998400998400

(Ohm

)

150100Z998400 (Ohm)

0

20

40

60

minusZ998400998400

(Ohm

)

1mM PPy5mM PPy

10 mM PPy

(c)





2 (10minus3)1mM 054 926 022 006 688 k 2061 001 13450 11145mM 857 1282 110 046 3111 k 1102 010 89021 280510mM 128 2172 567 062 1185 k 850 011 10311 291


W

CPE

Rs

Rct

(a)

W

CPE CPE

Rs

RctRp

(b)

CPE CPE

Rs

RctRp

(c)







4 Conclusion


Competing Interests


Acknowledgments


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





PEDOT 10mM

70 80 90 100 110 120 130 140 15060Z998400 (Ohm)

0

5

10

15

20

25

30

35

40

minusZ998400998400

(Ohm

)

(a)

Fitted line

0

5000

10000

15000

20000

minusZ998400998400

(Ohm

)

10000 20000 30000 40000 500000Z998400 (Ohm)

1mM PANI5mM PANI

10 mM PANI

150 200100Z998400 (Ohm)

20

40

60

80

minusZ998400998400

(Ohm

)

(b)

Fitted line

200 400 600 800 1000 12000Z998400 (Ohm)

0

100

200

300

400

500

minusZ998400998400

(Ohm

)

150100Z998400 (Ohm)

0

20

40

60

minusZ998400998400

(Ohm

)

1mM PPy5mM PPy

10 mM PPy

(c)





2 (10minus3)1mM 054 926 022 006 688 k 2061 001 13450 11145mM 857 1282 110 046 3111 k 1102 010 89021 280510mM 128 2172 567 062 1185 k 850 011 10311 291


W

CPE

Rs

Rct

(a)

W

CPE CPE

Rs

RctRp

(b)

CPE CPE

Rs

RctRp

(c)







4 Conclusion


Competing Interests


Acknowledgments


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




W

CPE

Rs

Rct

(a)

W

CPE CPE

Rs

RctRp

(b)

CPE CPE

Rs

RctRp

(c)







4 Conclusion


Competing Interests


Acknowledgments


References












































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials













































































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



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