Electrochemical Properties of an Osmium(II) Copolymer Film and Its Electrocatalytic Ability Towards...

Full Paper

Electrochemical Properties of an Osmium(II) Copolymer Film andIts Electrocatalytic Ability Towards the Oxidation of Ascorbic Acidin Acidic and Neutral pHKevin Foster, Timothy McCormac*

Centre for Research in Electroanalytical Technology “CREATE”, Department of Applied Science, Institute of Technology Tallaght(ITT) Dublin, Dublin 24, Ireland*e-mail: [email protected]

Received: February 06, 2006Accepted: March 31, 2006

AbstractCopolymerization of an osmium(II) functionalized pyrrole moiety, osmium-bis-N,N.-(2,2’-bipyridyl)-N-(pyridine-4-ylmethyl-(8-pyrrole-1yl – octyl)-amine)chloride (I) with 3-methylthiophene was carried out. The resulting conductingpolymer film exhibited a clear redox couple associated with the Os3þ/2þ response and the familiar conducting polymerbackbone signature. The effect of film thickness upon the redox properties of the copolymer was investigated inorganic electrolyte solutions. Scanning electron micrographs (SEM) along with energy dispersive X-ray (EDX)spectra of the copolymerized films were undertaken, both after formation and redox cycling in neutral buffer solution.These clearly show that electrolyte is incorporated into the polymer film upon redox cycling through the Os3þ/2þ redoxsystem. The Os3þ/2þ response associated with the copolymer was seen to be significantly altered in the presence ofascorbic acid both in acidic and neutral pH buffer solutions. This pointed to an electrocatalytic reaction between theascorbic acid and the Os3þ form of the copolymer. Under acidic conditions the copolymer film exhibited a sensitivityof 1.76 (�0.05) mA/mM with a limit of detection (LOD) of 1.45 mM for ascorbic acid. Under neutral pH conditions thecopolymer exhibited a sensitivity of 19.26 (�1.05) mA/mM with a limit of detection (LOD) of 1.28 mM for ascorbicacid.

Keywords: Osmium, Pyrrole, Copolymerization, 3-Methylthiophene, Ascorbic acid

DOI: 10.1002/elan.200603508

1. Introduction

The selective amperometric determination of ascorbic acid(H2A) is a major field of research primarily due to thevarious roles that it plays [1].H2A is electroactive and can beoxidized at positive potentials, the magnitudes of whichdependupon the pHof the solution.However the kinetics ofthe oxidation are “sluggish” and the oxidation products tendto lead to electrode fouling [2]. Therefore modified elec-trode systems have been investigated for the selectiveamperometric determination of ascorbic acid both in acidicandneutral pH. Someof these systems include cyclodextrins[3], macrocyclic compounds [4, 5], conducting and redoxpolymeric films [2, 6 – 9], metalloporphyrins [10], polyox-ometallates [11], transitionmetal hexacyanoferrates [12, 13]and ferrocene carboxylic acids [14, 15]. Previously [16] ourgroup reported on the synthesis, characterization, surfaceimmobilization and electrocatalytic properties of an Os(II)functionalized pyrrolemonomer, namely, osmium-bis-N,N’-(2,2’-bipyridyl)-N-(pyridine-4-yl-methyl- (8-pyrrole-1-yl-octyl)-amine) chloride (I). Attempts to polymerize thispyrrole monomer proved unsuccessful probably due to thecloseness of the bulkyOs(II) bipyridylmoiety to the pyrrolering. Our interest lies in the surface immobilization of I

through the employment of the well known copolymeriza-tion technique. In terms of copolymerization, the conduct-ing polymer of choice has been polypyrrole [17, 18], thisbeing primarily due to its “low oxidation potential” and“high conductivity” [19]. However recently thiophenes andits derivatives have been explored as possible matrixes forcopolymerization [20 – 22]. In this paper we report on thesuccessful copolymerization of I with 3-methylthiophene,electrochemical characterization of the resulting films alongwith their electrocatalytic properties towards the oxidationof ascorbic acid. Our interest in an osmium polymer basedsystem for the detection of ascorbic acid stems fromprevious work done on osmium based polymers for thedetermination of ascorbic acid [23], H2O2 [24], and glucose[25 – 27].

2. Experimental

2.1. Materials

I was synthesized and characterized according to theliterature [16]. All other chemicals were of reagent gradeand used as received. Acetonitrile (HPLC grade water

1097

Electroanalysis 18, 2006, No. 11, 1097 – 1104 E 2006 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim

content 0.005%), was dried by storing over anhydrouscalcium chloride for 24 hours and then over 4 M molecularsieves. The sieves having been activated in an oven at 523 Kovernight.

2.2. Apparatus and Procedures

Electrochemical experiments were performed in a singlecompartment three-electrode cell. The reference electrodeemployed, for the organic phase electrochemistry, was asilver wire in contact with an acetonitrile solution ofAgNO3

(0.01 M) and 0.1 M of the same supporting electrolyte as inthe cell. For aqueous investigations a Ag/AgCl referenceelectrode, with 3 M KCl, was employed. The workingmacroelectrode, namely a carbon (d¼ 2mm), was polishedwith 0.05 mm alumina, sonicated in deionized water for5 min, after which it was washed thoroughly with deionizedwater and acetone. The auxiliary electrode material was aplatinum wire. A CH 660A potentiostat was employed forall electrochemical experiments. All organic solutions wereprepared with dry HPLC grade acetonitrile with theaqueous buffers being prepared as detailed previously[16]. All electrolyte solutions were degassed with argonfor 15 minutes prior to the electrochemical investigations atroom temperature. Copolymer films of I and 3-methylthio-phene were electrochemically deposited from acetonitrilesolutions of 5 mM I and 52 mM 3-methylthiophene (3-MTHP) in 0.1 M TEAP by cyclic voltammetry with apotential window of �0.1 V to þ1.4 V, at a scan rate of100 mVs�1. This ratio between I and the 3-MTHPwas foundto be ideal. Previous experiments were attempted with arange of 1 :3 MTHP ratios being employed (i.e.:5 mM:5 mM; 2.5 mM:10 mM; 3 mM:20 mM; 3 mM;30 mM;5 mM:40 mM; 5 mM:10 mM). However it was found thatthese films all exhibited either poor stability or low redoxloadings of the Os2þ centre. After formation, each film wasrinsed with the solvent – electrolyte system that its electro-chemical behavior was going to be investigated in. Scanningelectron microscopy (SEM) was performed using a HitachiS-2400N system. For SEM investigations, films were formedon 3 mm radius carbon disks.

3. Results and Discussion

3.1. Electrochemical Characterization of CopolymerFilms

Previously our group has reported on the electrochemicalcharacterization of I [16]. As reported, I consists of areversible redox couple associatedwithOs3þ/2þ systemalongwith an irreversible pyrrole oxidation wave. Our previousattempts to polymerize I prooved unsuccessful. As a result,in this article, the technique of copolymerization of Iwith 3-methylthiophene has been undertaken. The formation ofthese copolymer films is described in the experimentalsection of the paper. Figure 1a illustrates the cyclic voltam-

mogram obtained during the deposition of the copolymer.What is clearly seen is that upon continuous cycling there is acontinual growth in peak currents associated with the Os3þ/

2þ redox couple. Also what is apparent is the appearance ofthe redox signature associated with the polythiophenebackbone at around þ0.4 V. Figure 1b illustrates the cyclicvoltammogram obtained for the resulting copolymer film inblank 0.1 M tetraethyl ammonium perchlorate (TEAP)acetonitrile solution. What is clearly seen is the redoxactivity associated with the Os3þ/2þ couple with an E1/2 ofþ0.09 V (vs. Ag/AgCl) along with the characteristic con-ducting polymer backbone electrochemical signature.Investigations into the electrochemical behavior of the

copolymerized films of I were undertaken with the effect offilm thickness being investigated. Table 1 summaries thevariation in peak splitting and anodic and cathodic peak fullwidths at half maximum FWHMwith sweep rate for a rangeof copolymers of varying surface coverages. Although theexpected zero peak to peak separation and a fwhm of90.6 mV for a one electron process are not seen the typicaltrend of peak splitting and FWHM increasing with increas-ing scan rate are seen throughout for each film. The stability

Fig. 1. a) Repetitive cyclic voltammogram of 0.1 mmol TEAPMeCN solution of 52: 5 mM of 3-methylthiophene:1 at a barecarbon electrode (A¼0.0314 cm2). Scan rate¼ 100 mV s�1; b)Cyclic voltammogram of the copolymerized film from Figure 1a in0.1 M TEAP MeCN on the carbon electrode (A¼ 0.0314 cm2).Scan rate¼ 30 mV s�1

1098 K. Foster, T. McCormac

Electroanalysis 18, 2006, No. 11, 1097 – 1104 www.electroanalysis.wiley-vch.de E 2006 WILEY-VCH Verlag GmbH&Co. KGaA, Weinheim

www.electroanalysis.wiley-vch.de

of the copolymer films of varying thicknesses towards redoxcycling in 0.1 MTEAPMeCNwas investigated. Itwas foundthat all films were extremely stable to redox cycling throughthe Os3þ/2þ redox process as there was no reduction in thefilms electroactivities after 50 cycles. Plots of current vs. scanrate indicated thin film behavior for films (G¼ 1.3�10�9 mol cm�2) up to scan rates of approximately 250 mVs�1. Such behavior is expected for a surface-immobilizedelectroactive film which is thin enough to ensure that allredox active sites within the film undergo complete oxida-tion and reduction during the potential cycle. For thicker

films however (G¼ 1.5� 10�8 mol cm�2) linear relationshipswere only obtained up to scan rates of 80 mV s�1, with anincrease in peak splitting and a loss of peak symmetry at aspecified scan rate.Preliminary scanning electron micrographs (SEM) along

with energy dispersive X-ray (EDX) images were taken ofthe copolymerized films both after formation and redoxcycling through the Os3þ/2þ system in pH 7 buffer solution.Figures 2a and 2b illustrate the SEM images obtained of acopolymerized film after formation, at different magnifica-tions. What is clearly seen is that the polymer surface

Fig. 2. a, b) SEM images of an immobilized copolymerized film deposited onto a carbon electrode (A¼0.0707 cm2) immediatelyafter formation and drying. c – e) SEM images of the copolymerised film from (a) after it has been electrochemically cycled through theOs3þ/2þ redox system in pH 7 buffer solution.

1099Properties of an Osmium(II) Copolymer Film



appears to be not smooth in nature but more granular innature with particles of roughly a few microns in diameter.The corresponding EDX images show the presence of theelements K, Cl, S, C, O and Os, as expected. Figures 2c – erepresent the resulting SEM images of the film once it hasbeen cycled through theOs3þ/2þ redox system in pH 7buffer.What is clear is that the film has undergone structuralmodification. The film now appears to possess a dendritictype structure as well as the granular nature, also inFigure 2d and more specifically in 2e crystals of KCl, fromthe buffer, are readily observedwithin the polymericmatrix.This is backed up by the EDX images of the film aftercycling. This shows an increased response for K as well as aresponse for Na, thereby clearly indicating that the electro-lyte is incorporated into the film upon redox cycling.

3.2. Electrocatalytic Activity of Films towards AscorbicAcid

3.2.1. Acidic Conditions

Figure 3a illustrates the irreversible oxidation of a 5 mMascorbic acid at a bare carbon electrode in pH 1.2, Ep, a isþ0.667 V (vs. Ag/AgCl). In addition to the positive positionof the anodic wave, it is well known that the products ofascorbic acid oxidation at a bare electrode cause fouling ofthe electrode.s surface. Figure 3b illustrates the cyclicvoltammogram obtained for an Os2þ copolymerized film,surface coverage 1.5� 10�8 mol cm�2, in pH 1.2 buffersolution. What is again apparent is the reversible oneelectron couple associated with the Os3þ/2þ redox process.The film.s stability towards redox cycling in this buffermedium was investigated and the film was found to beextremely stable, as seen in organic electrolyte media. Thefilm was then interacted with 5 mM ascorbic acid and theresulting cyclic voltammogram is shown in Figure 3c. Whatis clearly seen is the significant change in the redox behavior

of the film with the ascorbic acid being oxidized by the Os3þ

form of the coordinated metal centre in the copolymer. Thecatalytic wave associatedwith this interaction is situated at aless positive potential, namely Ep, a¼þ0.45 V, as comparedto that of the bare electrode in Figure 3a. It was found thatupon increasing the ascorbic acid concentration there wasan increase in the catalytic wave associated with themediation process in conjunction with a decrease in theOs3þ reduction wave. Figure 3d shows how the catalyticcurrent increases with increasing ascorbic acid concentra-tion. It can be seen that the relationship is linear up to anapproximate concentration of 8 mM after which the re-sponse levels off. This is probably due to the low availabilityof Os3þ sites which can effectively catalyze the oxidation ofthe higher concentrations of ascorbic acid.The effect of surface coverage upon the magnitude of the

catalytic current was investigated. It was found that for theinteraction of 2 mM ascorbic acid in pH 1.2 buffer, themagnitude of the ICAT was 5.9, 1.1 and 0.6 mA for films ofsurface coverage, G, 9.1, 1.2 and 0.5� 10�9 mol cm�2,respectively. The effect of scan rate upon the interactionbetween ascorbic acid and the Os2þ copolymer was inves-tigated. From comparing the two curves of Ip, a v

1/2 vs. v1/2 inthe absence and presence of ascorbic acid, it was found thatthe catalytic affect is apparent up to a scan rate ofapproximately 40 mV s�1. The operation of the Os2þ

copolymer modified electrode as an amperometric sensorwas investigated. An Eapp of þ0.45 V was applied to thecopolymer modified electrode under hydrodynamic con-ditions for approximately 20 minutes prior to the injectionof the first addition of the ascorbic acid. The standardcalibration curve obtained from performing the threeseparate I – t transients responses for the copolymerizedfilms of similar surface coverage (4.5� 5.5� 10�9 mol cm�2)(n¼3) is shown inFigure 2e. It shows good linearity from0.1to 1.5� 10�3 Mof ascorbic acidwith a correlation coefficientof 0.997, and a sensitivity of 1.76 (�0.05) mA/mM. The limitof detection (LOD) for our system in acidic pH, based on

Table 1. Electrochemical parameters of copolymerized films of I with 3-methylthiophene formed by CV.

Surface coverage G(mol cm�2)

Scan rate(mV s�1)

Peak splitting(mV)

Anodic peak FWHM(mV)

Cathodic peak FWHM(mV)

1.49� 10�9 10 31 148 12240 48 136 116100 54 136 118400 58 124 124

6.25� 10�9 10 34 152 10640 58 150 126100 85 160 132400 148 206 160

8.01� 10�9 10 28 158 9840 46 154 115100 76 156 156400 133 178 168

4.07� 10�8 10 36 212 11840 67 174 120100 118 182 120400 235 238 127




three times the S/N ratio, was found to be 1.45 mM. Inaddition a response time of approximately 18 – 20 secondswas found in the initial stages of the calibration curve. I – ttransients for the interaction of ascorbic acid with the

polymer were performed for films of varying thicknesses,1� 10�8, 5.4� 10�9 and 1.3� 10�9 mol cm�2. Standard cali-bration curves from the resulting I – t curves produced linearplots from approximately 0.1 to 1.5 mMwith sensitivities of

Fig. 3. a) Cyclic voltammogram of 5 mM ascorbic acid in pH 1.2 buffer at a bare carbon electrode (A¼ 0.0314 cm2). Scan rate¼ 5 mV s�1. b) Cyclic voltammogram of a copolymerized film of surface coverage 1.5� 10�8 mol cm�2, on a carbon electrode(A¼ 0.0314 cm2) in the aqueous pH 1.2 buffer solution. Scan rate¼ 5 mV s�1. c) Cyclic voltammogram of the copolymerized film fromFigure 2b in pH 1.2 buffer in the presence of 5 mM ascorbic acid. Scan rate¼ 5 mV s�1. d) Plot of ICAT versus [ascorbic acid] for the filmin Figure 2c in pH 1.2 buffer. e) Standard calibration plot representing amperometric data (n¼ 3) for the copolymerized film of I overthe range of 0.1 – 1.5 mM ascorbic acid in pH 1.2 buffer. f) Cyclic voltammogram of poly(3-methylthiophene) film in pH 1.2 buffer in theabsence (—) and presence (—) of 1 mM ascorbic acid. Scan rate¼ 5 mV s�1




3.4(�0.04), 2.3(�0.05) and 0.77(�0.009) mA/mM for thefilms respectively. Thus clearly showing that the thicker filmpossessed the highest sensitivity, probably due to the highernumber of electrocatalytic Os3þ sites within the film.Investigations into the possible electrocatalytic ability of

the poly (3-methylthiophene) backbone towards ascorbicacid was also investigated. A poly (3-methylthiophene) filmwas electrochemically deposited, from blank electrolyte(0.1 M TEAP), by potential cycling between �0.2 andþ1.4 V. The film was then stabilized in pH 1.2 buffer andvarious additions of ascorbic acid were then added to thebuffer medium. It was found that for 1 mM ascorbic acid airreversible peak atþ0.65 Vwas obtained, this is illustratedin Figure 3f. As the concentration of ascorbic acid isincreased the position of this peak moves to more positivepotentials. The positive nature of this peak clearly showsthat the response obtained in Figure 3c is due to theinteraction between the Os3þ sites and the ascorbic acid.

3.2.2. Neutral Conditions

As detailed in the previous section there is an electro-catalytic reaction between the Os3þ form of the copolymerand ascorbic acid in acidic conditions. This section detailsthe preliminary work carried out into the electrocatalyticbehavior of the films towards ascorbic acid in neutral pHconditions. Figure 4a illustrates the irreversible oxidation ofa 1 mM ascorbic acid at a bare carbon electrode in pH 7.2,Ep, a, isþ0.221 V. Figures 4b and 4c show the redox behaviorof the Os2þ copolymer, G¼ 3� 10�9 mol cm�2,in pH 7.2buffer and the interaction between the film and 1 mMascorbic acid in pH 7.2, respectively. What is clear is thatthere is a similar reaction between the ascorbic acid and theOs3þ centre within the copolymer as detailed in the previoussection. However the potential for this process is slightlymore positive than the bare electrode reaction for ascorbicacid in neutral pH. However the advantages of our copoly-mer is that the observed catalytic current is significantlyhigher than at the bare electrode and that electrode fouling

Fig. 4. a) Cyclic voltammogram of 5 mM ascorbic acid in pH 7.2 buffer at a bare carbon electrode (A¼ 0.0314 cm2). Scan rate¼ 5 mVs�1. b) Cyclic voltammogram of a copolymerized film of surface coverage 3� 10�9 mol cm�2, on a carbon electrode (A¼ 0.0314 cm2) inthe aqueous pH 7.2 buffer solution. Scan rate¼ 5 mV s�1. c) Cyclic voltammogram of the copolymerized film from (b) in pH 7.2 buffer inthe presence of 5 mM ascorbic acid. Scan rate¼ 5 mV s�1. d) Standard calibration plot representing amperometric data (n¼ 3) for thecopolymerized film of I over the range of 0.1 – 1.5 mM ascorbic acid in pH neutral conditions.




is avoided. The effect of ascorbic acid concentration uponthe measured catalytic current was investigated. A linearplot of ICAT vs. [AA] was recorded up to an ascorbic acidconcentration of approximately 25 mM.As discussed for the acidic medium, the response of the

modified electrode to injections of ascorbic under hydro-dynamic conditions was also performed. The standardcalibration curve obtained from performing the threeseparate I – t transients responses for three separate poly-mer films (n¼ 3) of similar surface converges (4.5 – 6.6�10�9 mol cm�2) is shown in Figure 4d. It shows good linearityfrom 0.1 to 1.5� 10�3 M of ascorbic acid with a correlationcoefficient of 0.999, and a sensitivity of 19.56 (�1.05) mA/mM.The limit of detection (LOD) was found to be 1.28 mM,with response times of typically 18 – 20 seconds in the initialstages of the calibration curve.

3.2.3. Role of Possible Interferents

Previously, Lupu et al. [28], investigated the effect ofpossible intereferents, on the behavior of their “polythio-phene derivative conducting polymer modified electrode”towards the electrocatalytic oxidation of ascorbic acid.Employing Lupu et al..s work as a basis for an investiga-tion, we have conducted preliminary investigations into theeffect of the presence of uric acid, acetaminophenol andglucose on the redox behavior of our copolymerizedconducting polymer films. Figure 5a illustrates the cyclicvoltammogram obtained when a Os2þ copolymerized filmis interacted with 1 mM glucose, in pH 7 buffer solution.What is clearly observed is that there is no change in theredox behavior of the Os3þ/2þ redox system in the presenceof the glucose. Increasing the glucose concentration to5 mM again showed no marked change in the polymers.redox activity. The effect of paracetamol addition on theredox behavior of our copolymerized film was also inves-tigated in buffer pH 7 solution. At the bare carbonelectrode an oxidation wave (Ep, a, þ0.44 V) for theoxidation of 1 mM paracetamol is observed with anassociated current of 6.4 mA. Upon the addition of 1 mMparacetamol to a carbon electrode modified with acopolymerized film of I with G of 4.8� 10�9 mol cm�2, inpH 7 solution, there is amarked effect on the redox activityof the polymer film. The peak associated with the Os2þ

centre moves from þ0.37 V to þ0.48 V with a largeincrease in current from 3.2 to 10.0 mA, but there is only asmall increase in the peak current associated with the Os3þ

reduction wave with no change in peak potential. Onepossible explanation for this is that the paracetamol is ableto diffuse freely through the polymer matrix and react atthe underlying electrode. As a result the employment ofthis modified electrode towards the determination ofparacetamol is not possible. Lupu et al. also found thattheir polythiophene modified electrode was incapable ofthe determination of paracetamol. The response of thecopolymerized film towards the oxidation of uric acid hasalso been investigated. It was found that the addition of1mm uric acid caused an increase in the Os2þ oxidation

wave in a very similar fashion to the observed with theascorbic acid addition. Currently our group are trying todetermine a strategy to separate out the two responsesfrom both ascorbic and uric acid in pH 7 buffer for ourpolymer modified electrode system. These results ob-served are in good agreement with the work of Lupu et al.[28].

4. Conclusions

There are several conclusions from our worka) Extremely stable conducting polymer films have been

obtained through copolymerization of 3-methylthiopheneand I, which exhibit a clear redox couple associated with anOs3þ/2þ systemb) The resulting copolymerized films exhibited a clear

electrocatalytic effect upon the oxidation of ascorbic acidunder acidic and neutral conditions.c) Under acidic conditions the copolymer film exhibited a

sensitivity of 1.76 (�0.05) mA/mmolwith a limit of detection(LOD) of 1.45 mM for ascorbic acid.d) Under neutral conditions the copolymer film exhibited

a sensitivity of 19.26 (�1.05) mA/mmol with a limit ofdetection (LOD) of 1.28 mM for ascorbic acid.

5. Acknowledgements

Financial support obtained through the Irish PostgraduateResearch and Development of Skills Programme throughthe grant TA 08 2002 and the ITT Dublin.s 2005 PhDcontinuance fund is acknowledged. The authors would alsolike to thankDrAineAllen fromITTDublin for the runningof the SEM and EDX spectra of the polymer films.

Fig. 5. Cyclic voltammogram of a copolymerized film of I on acarbon electrode (A¼ 0.0314 cm2) in the aqueous pH 7.2 buffersolution, in the absence (—) and presence (—) of 1 mM glucose.Scan rate¼ 5 mV s�1




6. References

[1] G. A. Gilman, W. T. Rall, A. S. Nies, P. Taylor, The Pharma-cological Basis of Therapeutics (Eds: Goodman, Gilman),McGraw-Hill, Singapore 1991, 1547.

[2] M. E. G. Lyons, W. Breen, J. Cassidy, J. Chem. Soc. FaradayTrans. 1991, 87, 115.

[3] M. I. Manzanares, V. Solis, R. H. de Rossi, J. Electroanal.Chem. 1997, 430, 163.

[4] V. S. Ijeri, P. V. Jaiswal, A. K. Srivastava, Anal. Chim. Acta2001, 439, 291.

[5] J. Ren, H. Zhang, Q. Ren, C. Ren, C. Xia. J. Wan, Z. Qin, J.Electroanal. Chem. 2001, 504, 59.

[6] L. Zhang, S. Dong, J. Electroanal. Chem. 2004, 568, 189.[7] J-B. Raoof, R. Ojani, S. Rashid-Nadimi, Electrochim. Acta2004, 49, 271.

[8] A. P. Doherty, M. A. Stanley, J. G. Vos, Analyst 1995, 120,2371.

[9] G. Che, S. Dong, Electrochim. Acta 1996, 41, 381.[10] S-M. Chen, Y-L. Chen, J. Electroanal. Chem. 2004, 573, 277.[11] C. Sun, J. Zhang, Electrochim. Acta 1998, 43, 943.[12] C-X. Cai, K-H. Xue, S-H. Xu, J. Electroanal. Chem. 2000,

486, 111.[13] M. H. Pournaghi-Azar, H. Razmi-Nerbin, J. Electroanal.

Chem. 2000, 488, 17.[14] L. Fernandez, H. Carrero, Electrochim. Acta 2005, 50, 1233.

[15] J-B. Raoof, R. Ojani, A. Kiani, J. Electroanal. Chem. 2001,515, 45.

[16] K. Foster, A. Allen, T. McCormac, J. Electroanal. Chem.2004, 573, 203.

[17] B. Sari, M. Talu, Synth. Met. 1998, 94, 221[18] K. Habermuller, A. Ramanavicius, V. Laurinavicius, W.

Schuhmann, Electroanalysis 2000, 12, 1383.[19] T. A. Scotheim, Handbook of Conducting Polymers, 1st ed.,

Marcel Dekker, New York 1983.[20] H. P. Welzel, G. Kossmehl, G. Engelmann, W. D. Hunnius, W.

Plieth, Electrochim. Acta 1999, 44, 1827.[21] J. Ochmanska, P. G. Pickup, J. Electroanal. Chem. 1991, 297,

197.[22] J. Roncali, Chem. Rev. 1992, 92, 711.[23] A. P. Doherty, M. A. Stanley, J. G. Vos, Analyst 1995, 120,

2371.[24] M. Dequaire, A. Heller, Anal. Chem. 2002, 74, 4370.[25] L. Yang, E. Janle, T. H. Huang, J. Gitzen, P. T. Kissenger, M.

Vreeke, A. Heller, Anal. Chem. 1995, 67, 1326.[26] E. Csoregi, D. W. Schmidtke, A. Heller, Anal. Chem. 1995,

67, 1240.[27] T. J. O Hara, R. Rajagopalan, A. Heller, Anal. Chem. 1993,

65, 3512.[28] S. Lupu, A. Mucci, L. Pigani, R. Seeber, C. Zanardi,

Electroanalysis. 2002, 14, 519.




Electrochemical Properties of an Osmium(II) Copolymer Film and Its Electrocatalytic Ability Towards...

Documents

Transcript of Electrochemical Properties of an Osmium(II) Copolymer Film and Its Electrocatalytic Ability Towards...