electrochemical behavior of malachite green in aqueous solutions

Hindawi Publishing CorporationISRN ElectrochemistryVolume 2013 Article ID 839498 10 pageshttpdxdoiorg1011552013839498

Research ArticleElectrochemical Behavior of Malachite Green inAqueous Solutions of Ionic Surfactants

Mohammad Mijanur Rahman1 M Yousuf A Mollah1

M Muhibur Rahman2 and Md Abu Bin Hasan Susan1

1 Department of Chemistry University of Dhaka Dhaka 1000 Bangladesh2University Grants Commission of Bangladesh Agargaon Dhaka 1207 Bangladesh

Correspondence should be addressed to Md Abu Bin Hasan Susan susanduacbd

Received 22 July 2013 Accepted 24 August 2013

Academic Editors H Karimi-Maleh and R Kizek

Copyright copy 2013 Mohammad Mijanur Rahman et al This is an open access article distributed under the Creative CommonsAttribution License which permits unrestricted use distribution and reproduction in any medium provided the original work isproperly cited

Electrochemical behavior of malachite green (MG) oxalate in aqueous solution was studied in the presence of a cationic surfactantcetyltrimethylammonium bromide (CTAB) and an anionic surfactant sodium dodecyl sulfate (SDS) at a glassy carbon electrodeusing cyclic voltammetry The electrochemical oxidation of MG has been characterized as an electrochemically irreversiblediffusion-controlled process Oxidative peak current sharply decreased with increasing SDS concentration while a slight increasewith increasing [CTAB] was apparent The apparent diffusion coefficient the surface reaction rate constant and the electrontransfer coefficient of MG clearly show correlation of the electrochemical behavior with the dissolved states of the surfactantsElectrochemical observations together with spectrophotometric results at varying surfactant concentrations provide evidence ofinteraction of MG with the surfactants to varying extent depending on the type of the surfactant and the concentration

1 Introduction

Triphenylmethane (TPM) dyes an important class of syn-thetic organic compounds have been a promising mate-rial for diverse applications which inter alia include thefollowing as fungicides in aquaculture as parasiticides inpharmaceuticals as dye materials in industry and as redoxmediators bioprobes and pH indicators in both fundamentaland applied sciences [1ndash6] A proper understanding anddevelopment of fundamental knowledge base of physico-chemical properties of TPM dyes have therefore attractedsignificant attention Techniques so far employed for this arepolarography [7] conductometry [8 9] potentiometry [10]spectrophotometry [11 12] electrochemical methods [13]membrane selective electrode [14] and so on Dyes of TPMbackbones such as malachite green (MG) crystal violet [15]ethyl violet [16] and victoria blue B [17] are electrochemicallyactive and recent surge of interest has been the explorationof the redox behavior of such dyes Among the TPM dyesthe prospect of MG (chemical structure shown in Scheme 1)

for versatile applications [1] prompted many researchers tostudy the electrochemical behavior of MG for developmentof electrochemically switchable devices The electrochemicaloxidation of MG occurs at 119873-containing lone-pair electronand the reduction process is due to reduction of oxidized ter-tiary amino group of MG [2 10] In acidic aqueous solutionsthe anodic oxidation of MG leads to the formation of theoxidized form of 1198731198731198731015840 1198731015840-tetramethylbenzidine (TMB)([1 11015840-biphenyl]-4 41015840-diamine) that is TMBOx whereas theoxidation of the dye in liquid sulphur dioxide is quitedifferent from the observation in acidic aqueous medium[18 19] The electrochemical behavior of MG also exhibitsstrong pH dependence and the oxidation of protonated andhydrated forms of MG is an electrochemically irreversiblediffusion-controlled two-electron transfer process [18 20]The MG dye in surfactant-based organized media may beeven more interesting and help to develop electrochemicallyswitchablemolecular devices however solution behavior andelectrochemistry at the interfaces for the dye in such systemsare yet to be systematically studied

2 ISRN Electrochemistry

N+ (CH3)2

(CH3)2

Scheme 1 Chemical structure of MG+

There are numerous reports on the study of the electro-chemical behavior of electroactive species in surfactant-basedorganized media in literature The electrochemical behaviorof redox-active surfactants containing different electroactivegroups has been found to be controllable by changing theconcentration of surfactants [21 22] Susan and coworkers[23ndash25] reported the solution behaviors of redox-activeamphiphiles linked with an anthraquinone group and cor-related the electrochemical behavior of anthraquinone withthe dissolved states of the nonionic surfactant Haque et al[26 27] studied the electrochemical responses of sodium saltof anthraquinone-2-sulphonic acid (AQS) on the dissolvedstates of the surfactant cetyltrimethylammonium bromide(CTAB) and found that the current-potential behavior isprofoundly influenced by the concentration of the surfactantand redox state of anthraquinone Similar observation wasreported for electrochemical behavior of AQS in a nonionicsurfactant Triton X-100 [28] Pedraza et al [29] showedthat opposite charges of dye and surfactant can form dye-surfactant complex in solution The behaviors of TPM dyesin different aqueous anionic surfactant solutionswere studiedby spectral measurements and it was reported that dye-surfactant ion pairs form at the surfactant concentrationswell below their critical micelle concentration (CMC) [30]Huang et al [31] also showed that the negatively-chargedsodium dodecyl benzene sulphonate interacts with positivelychargedMG and can accumulate onto carbon paste electrodesurface by electrostatic interaction On the other hand thecationic surfactant cetylpyridinium bromide (CPB) makesthe oxidation of MGmore difficult due to adsorption of CPBon the electrode surface [32] In similarly charged dye-micellesystems the electrostatic repulsion can be overcomeby stronghydrophobic interactions [33ndash35]

MG has two amino groups in its structure and is highlysoluble in waterThree phenyl rings in the structure offerMGstrong hydrophobic characteristics while the positive chargeof the dye provides the scope of interaction to varying extentwith cationic and anionic surfactants to different extent bothin the monomeric and micellized states These make MG anintriguing probe for electrochemical studies With a view tounderstanding the aqueous electrochemistry of MG and itsinteractions with ionic surfactants we therefore investigatedthe cyclic voltammetric behavior of MG at a glassy carbonelectrode (GCE) surface in aqueous solution and in presenceof ionic surfactants of CTAB and sodium dodecyl sulfate

(SDS) and compared electrochemical responses in differentmedia to correlate with the dissolved states of the surfactants

2 Experimental

21 Materials Malachite green oxalate ([(C23H25N2)

sdot(C2HO4)]2sdotC2H2O41198731198731198731015840 1198731015840-tetramethyl-4 41015840-diamin-

otriphenylcarbenium oxalate) from TCI Tokyo Japancetyltrimethylammonium bromide (CTAB) and sodiumdodecyl sulfate (SDS) from Merck and sulfuric acid(H2SO4) lead dioxide (PbO

2) perchloric acid (HClO

4) pot-

assium chloride (KCl) hydrochloric acid (HCl) and sodiumhydroxide (NaOH) from BDH were used as receivedwithout further purifications Solutions were prepared withdeionized water (conductivity 0055120583S cmminus1 at 25∘C) fromHPLC grade water purification systems (BOECO Germany)A sonicator (LU-2 Ultrasonic cleaner USA) was used toclean electrodes and to prepare stock solutions

22 Measurements Spectrophotometric measurements weremade with a double-beam Shimadzu UV-visible spectropho-tometer (model UV-1650 PC) by using quartz cells with1 cm path length Cyclic voltammetric measurements wereperformed with a computer-controlled electrochemical ana-lyzer (CHI 600D CH Instruments USA) A single compart-ment three-electrode cell containing a GCE with geometricarea of 0071 cm2 as the working electrode a silver-silverchloride (AgAgCl) electrode (100M KCl) as the referenceelectrode and a platinum coil as the counter electrode wereused for electrochemical measurements The surface of theworking electrode wasmirror polished with 005120583malumina(Buehler) before each run The electrochemical measure-ments were carried out using 010M KCl aqueous solution asthe supporting electrolyte A pHmeter (HM-26 S TOA elec-tronics Ltd Japan) was used for measurements of pH valuesof solutionsThe electrochemical and spectral measurementswere conducted at constant room temperature (25 plusmn 05∘C)

3 Results and Discussion

31 Dye-Surfactant Interaction of MG with CTAB and SDS inAqueous Solution The visible spectrum of MG in aqueoussolution shows a broad band at the absorption maximum of6175 nm (120576 = 100 times 105Mminus1 cmminus1) The absorption spectraof MG in aqueous solutions with change in concentrationof CTAB and SDS were measured and spectral analyseswere made to correlate dye-surfactant interaction with thedissolved states of the surfactants

Figure 1(a) represents the visible spectra of 10 times 10minus6MMG in 10 times 10minus4M aqueous solution of KCl at 25 plusmn 01∘C forCTABThe absorbance at the 120582max that is 6175 nm as a func-tion of [CTAB] profile is also presented in Figure 1(b) The120582max did not show any appreciable change with increasingconcentration of CTAB The absorbance at the 120582max on theother hand increases with increasing [CTAB] up to a con-centration of 025times10minus3Mafter which absorbance apparentlydecreases with further increase in [CTAB] (Figure 1(b))

Both MG and CTAB are positively charged and there-fore at low concentrations of CTAB electrostatic repulsion

ISRN Electrochemistry 3

Wavelength (nm)500 550 600 650 700

Abso

rban

ce

00

02

04

06

08

10

12

(1)

(2)

(3)

(4)

(1) 0(2) 025

(3) 100(4) 450

[CTAB] times 103 M =

(a)

0 1 2 3 4 5 6

Abso

rban

ce at

617

5 nm

00

02

04

06

08

10

12

[CTAB] times 103 (M)

(b)

Figure 1 (a) Absorption spectra of 10 times 10minus6MMG in 010M aqueous solution of KCl in the presence of CTAB at various concentrations(b) absorbance at 6175 nm versus [CTAB]

between MG and CTAB becomes dominant and free MGspecies contributemore to the absorption to show an increasein absorbance with increasing [CTAB] However at highconcentrations of CTAB self association results in the for-mation of thermodynamically stable aggregates of colloidaldimension that is micelles and the hydrophobicity of MGfavors solubilization in the core of micelles to result in aconsequent decrease in the absorbance

Figure 2(a) shows the absorption spectra of 10 times 10minus6MMG in 010M aqueous solution of KCl in the presence ofSDS of varying concentrations while Figure 2(b) shows theabsorbance at 6175 nm as a function of [SDS] The additionof SDS to aqueous solution of MG causes a shift in theposition of 120582max towards longer wavelength The absorbanceat 6175 nm was also found to decrease with increasing SDSconcentration up to 06times10minus3MThese are indicative of bind-ing of monomeric SDS with the carbocationic dye MG Atconcentrations of SDS above 070times10minus3M a sharp increase inabsorbance is apparent which levels off above [SDS] = 75 times10minus3M In the submicellar range the monomeric surfactant

tends to aggregate but compete with the strong interactionof positively charged MG and negatively charged SDS andfinally MG species are solubilized by SDS micelles

Interestingly for 20 times 10minus3M SDS a new weak band duepossibly to the formation of dimer of MG appears at 120582max =5840 nm (Figure 2(a)) for MG solution and the shoulderdiminishes at 60times10minus3MThe 120582max exhibits a bathochromicshift from 6175 nm to ca 6260 nm for addition of SDS inthe MG to attain a constant value from 75 times 10minus3M (insetof Figure 2(a)) This further emphasizes that dye-surfactantinteraction plays a key role for change in spectrophotometricbehavior and when micellization occurs the solubilizationbehavior outweighs the dye-surfactant interactions

The 120582max versus [surfactant] and absorbance-[surfactant]profiles greatly differed to reflect the differences in inter-action of MG with CTAB and SDS Varying electrostaticand hydrophobic interactions of the positively charged MGwith the positively charged CTAB and negatively chargedSDS in monomeric and micellized states are interesting Inthe subsequent sections the difference will be correlatedwith change in electrochemical behavior of MG in aqueoussolutions of CTAB and SDS

32 Electrochemical Behavior ofMG inAqueousMedium in theAbsence of Surfactants Cyclic voltammetric behavior of MGin KCl aqueous solution at GCE was investigated at potentialsweeps from 010 to 080V The electrochemical responseshave been found to fairly depend on the concentrations ofMG (Figure 3) At 50 times 10minus4MMG in KCl aqueous solutionand the cyclic voltammogram at the scan rate of 001 V sminus1shows one anodic peak at 063V in the positive scan andone reduction peak at 037V on the reverse scan (Part (A)of Figure 3) The shapes of the cyclic voltammograms agreewith those reported by literatures [13 17 18] When anodicpotential is applied the electrochemical oxidation of TPMdyes has been reported to lead to the formation of TMBOxresulting from the ejection of an integral unit of the centralcarbon attached to a phenyl group followed by intramolec-ular coupling of two phenyl fragments [18] In the reversescan TMBOx is reduced to its final product TMB [18]With decreasing concentration of MG anodic peak currentdecreases with a shift in peak potential towards less positivevalues (Parts (B) and (C) of Figure 3)The observed oxidationpeak currents were found to increase linearly with increasingconcentration of MG at the concentration range of 10 times 10minus6to 50 times 10minus4M in aqueous solution of KCl Moreover at a


Wavelength (nm)

Abso

rban

ce

00

04

08

12

16

(1) 0(2) 20

(3) 80(4) 300

(1)

(2)

(3)

(4)

616

620

624

628

(1)

(2)

(3)

(4)

616

620

624

628

0 5 10 15 20 25 30

500 550 600 650 700 750

120582m

ax(n

m)

[SDS] times 103 M =

[SDS] times 103 (M)

(a)Ab

sorb

ance

at 6

175

nm

04

06

08

10

12

14

0 5 10 15 20 25 30[SDS] times 103 (M)

(b)

Figure 2 (a) Absorption spectra of 10 times 10minus6M MG in 010M aqueous solution of KCl in the presence of SDS at various concentrationsInset shows plot of [SDS] versus 120582max (b) Absorbance at 6175 nm versus [SDS]

0102030405060708

Oxidation waveOxidation wave

Potential E (V versus AgAgCl)

(A) 50 times 10minus4 M MG

(B) 10 times 10minus5 M MG

(C) 10 times 10minus6 M MG

Curr

enti

(120583A

)

050 120583A

020 120583A

100 120583A

Figure 3 Dependence of cyclic voltammograms on concentrationof MG in aqueous solution of KCl at the scan rate of 001 V sminus1

very low concentration of MG (10 times 10minus6M) the cathodicpeak cannot be distinguished (Part (C) of Figure 3)

Cyclic voltammetric measurements of 50 times 10minus4M MGin 010M KCl aqueous solution were also carried out at GCEat a scan rate ranging from 001 to 05 V sminus1 (Figure 4) Inthe first scan MG leads to the formation of TMBOx and isreduced to TMB In the subsequent scan (by polishing the

GCE surface before each run) the anodic and cathodic peakcurrents increase with increasing scan rate (Figure 4(a))

If voltammetric experiments are carried out under iden-tical scan rate without polishing the GCE for subsequentscan a new oxidation peak (O2) appears at a potential lesspositive than the first anodic peak O1 (Figure 4(b)) TheO2 is the oxidation wave of the reductive peak (R1) andcorresponds to the redox couple TMBOxTMB [18] whereTMBOx refers to the oxidized form of TMB (Scheme 2)The cathodic peak current increases from the subsequentscans due to the diffusion of reducible species TMBOx tothe electrode interface [18 36] For successive scans the O1decreases cycle by cycle with increase of peak current ofTMBOxTMB redox couple (figure not shown) Chen et al[10] inferred that the growth of MG film on bare GCE due toelectropolymerization may be responsible for this change

33 Electrochemical Behavior of MG in Presence of CTABand SDS in Aqueous Solution Electrochemical behavior ofMG at a GCE with KCl aqueous solution as the supportingelectrolyte was studied in the presence of ionic surfactantsCTAB and SDS of varying concentrations (Figure 5) Theanodic oxidation peak potential and peak current of MGvary in aqueous solutions of CTAB and SDS (Figures 5(a)and 5(b)) Below the concentrations of 100 times 10minus3M theanodic peak current corresponding to O1 (1198941pa) increases withincreasing [CTAB] and the anodic peak potential (1198641pa) shiftstomore positive values At concentrations above 100times10minus3Mof CTAB the 1198641pa is almost constant while a slight increase of1198941

pa is apparent (Figure 5(a))MG is a cationic dye andCTAB isa cationic surfactant therefore due to electrostatic repulsionhydrophobic interaction prevails As the concentration of


0002040608minus40

minus30

minus20

minus10

0

10


Reduction wave

Anodic peak (O1)

Cathodic peak (R1)

I

VICurr

enti

(120583A

)

PotentialE (V versus AgAgCl)

(a)

00010203040506070809

minus25

minus20

minus15

minus10

minus5

0

5

10Cathodic peak (R1) Cathodic peak (R1)

Reduction wave

Oxidation wave

Anodic peak 1 (O1)

Anodic peak 2 (O2)I

VICurr

enti

(120583A

)


(b)

Figure 4 Cyclic voltammograms of 50 times 10minus4MMG in aqueous solution at different scan rates (I 001 and VI 050 Vsminus1) (a) the GCE waspolished prior to each measurements (b) the subsequent measurements without further polishing of GCE

N N+

H3C H3C

H3CH3CN+ N+

CH3

CH3

CH3

CH3

2eminus

TMBOx TMB

Scheme 2 Redox reaction of TMBOx

CTAB is further increased electrostatic repulsion betweenthemicellar head groups andpositively chargedMG increasesdiscouraging further solubilization of MG in the core ofmicelle

SDS affects both 1198641pa and 1198941

pa of the MG in aqueous solu-tions At concentrations below 100times10minus3M the 1198941pa decreaseswith increasing SDS and the 1198641pa shifts to less positive valuesAt 100 times 10minus3M the 1198641pa shifts slightly to higher potentialWith further addition of SDS the 1198641pa shifts to less positivevaluesThe 1198941pa reaches almost a constant value as the concen-tration of SDS reaches 40 times 10minus3M (inset of Figure 5(b))This may be ascribed to the fact that at very low concen-trations of SDS MG interacts with monomeric SDS Withincrease in SDS concentration 1198941pa decreases This may bedue to slower diffusion of MG incorporated in micelle to theelectrode interface The dye-monomer surfactant interactionis supported by the changes in absorbance and wavelengthcorresponding to the absorption maximum (120582max) in thevisible spectra with change in SDS concentration for a fixed[MG] (Section 31)

The anodic peak current 1198941pa versus [surfactant] profilesmay also be used for the electrochemical estimation of theCMC values of CTAB and SDS with 5times10minus4MMG in 010Maqueous solution of KCl The CMC values as apparent frominset of Figures 5(a) and 5(b) are 100times10minus3 and 400times10minus3Mrespectively for CTAB and SDS under the experimentalconditions usedThe values are different from those reported

in the literature especially using specific conductance andtensiometricmeasurementsThis is not surprisingThediffer-ence in the technique ofmeasurements gives rise to differencein CMC Takeoka et al [22] reported the CMC value of aferrocenyl surfactant from the surface tension measurementsto be 0012mM which is estimated as 0089mM fromelectrochemical measurements Similar observations are alsoreported for an anthraquinonyl surfactant [25]

The cyclic voltammograms of MG indicate that theanodic and cathodic peak currents increase as the scan rateis increased The plot of logarithm of peak current versuslogarithm of scan rate allows us to diagnose the electro-chemical process in aqueousmedia (not shown in the figure)The theoretical slope for a diffusion-controlled voltammo-gram is 05 and for ideal adsorption it is 1 [37]The value of theslope of the plot was in range 043 to 051 for the peaks O1 andR1 while the value ranged from 060 to 074 for peak O2Thisindicates that the peaks O1 and R1 are diffusion-controlledbut the anodic peak of O2 whether in absence or in presenceof surfactants has influences from adsorbed species on theoverall electrochemical process

Figure 6 depicts the effect of CTAB and SDS on the halfwave potentials (119864

12 taken as the average of the potential

of the second anodic peak O2 (1198642pa) and the cathodic peakR1 (119864pc) for the subsequent cycles) of TMBOxTMB redoxcouple No significant changes in potentials were observed upto concentration of 25 times 10minus3M SDS after which the peakpotential showed a sharp fall This may be due to strong dye-surfactant interactions On the other hand 119864

12shows only a


0002040608minus10

minus8

minus6

minus4

minus2

0

2

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

Curr

enti

(120583A

)


I

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

I

[CTAB]times 103 (M)

(a)

0002040608minus4

minus3

minus2

minus1

0

1

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

Curr

enti

(120583A

)


[SDS] times 103 (M)

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

[SDS] times 103 (M)

(b)

Figure 5 Cyclic voltammograms of 5 times 10minus4M MG in 010M aqueous solution of KCl at various concentrations of surfactants (a) Cyclicvoltammograms of MG in the presence of CTAB Concentrations of CTAB (from I to VI) 0 025 times 10minus3 05 times 10minus3 10 times 10minus3 5 times 10minus375times10

minus3M (b) Cyclic voltammograms ofMG in the presence of SDS Concentrations of SDS (from I to VI) 0 10times10minus3 20times10minus3 30times10minus340 times 10

minus3 50 times 10minus3MThe scan rate was 001 V sminus1 Insets show plot of 1198941pa versus [surfactant]

0 2 4 6 8 10 12030

032

034

036

038

040

042

044

CTABSDS

Hal

f wav

e pot

entia

lE12

(V v

ersu

s Ag

AgC

l)

[Surfactant] times 103 (M)

Figure 6 Half wave potential (versus AgAgCl) of the secondcycle plotted against the concentration of CTAB and SDS forTMBOxTMB redox couple in 010M aqueous solution of KCl Thescan rate was 001 V sminus1

slight decrease at low concentrations of CTAB below its CMCvalue which is indicative of the ease of the redox process inCTAB monomeric solutions

The separation of peak potentials of TMBOxTMB redoxcouple is higher than 0030V irrespective of the presence orabsence of surfactants As the separation of peak potentialsis less than 0059119899V (here 119899 = 2) cyclic voltammogramsdo not correspond to a reversible process The ratio of thesecond anodic peak current of O2 and the cathodic peakcurrent of R1 (1198942pa119894pc) is smaller than 1 which indicates thatthe electrochemical reaction is complicated by some other

processes like a following chemical reaction [38] The ratiohas been found to increase with increasing scan rates tosupport this conclusion

34 Chemical Oxidation of MG and Evidence for the For-mation of TMBOxTMB Redox Couple 50 times 10minus4M MGwas oxidized in 10M H

2SO4with lead dioxide which

yielded a brown colored precipitate in the mixture The pre-cipitate underwent dissolution with added perchloric acidThe shapes of the cyclic voltammograms agree with thosereported by Galus and Adams [18]The chemical oxidation ofMG leads to the formation ofTMBOxwhich is soluble in per-chloric acidThe cyclic voltammetric behaviors of chemicallyoxidizedMG solution that is TMBOx in aqueous solution ofKCl at different pH (pH was adjusted by addition of aqueoussolution of H

2SO4or NaOH) are shown in Figure 7 The

oxidized MG gives a pair of well-defined redox peaks in thepotential range of 080 to 030V in acidic aqueous solution ofpH 114 with a reduction peak at 053V and an oxidation peakat 056V respectivelyThe peak potential shifts to less positivevalue of 046V and 049V respectively at pH 214 In highlyalkaline media of pH 1070 the cyclic voltammogram showsone anodic peak which is electrochemically irreversible

Aqueous solution of MG has three absorption peaksin the range of 200ndash800 nm with absorption maximumat wavelength 6175 4245 and 3165 nm respectively Theabsorbance at 6175 nm is found to decrease abruptly withdecreasing pH of the aqueous solution ofMGTheUV-visiblespectrum of chemically oxidized MG solution is differentfrom that of MG aqueous solution (Figure 8) The TMBOxin acidic medium is yellowish in color and at pH 170the spectrum showed two absorption peaks at 2560 and4610 nm A new peak at 2040 nm appeared in a highly acidicmedium of pH lt 120 Jiao et al [39] reported that at pH200 3 31015840 5 51015840-tetramethylbenzidine (another form of TMB)gives absorption peaks in the UV-visible region respectively


030405060708minus6

minus4

minus2

0

2

4

6

8

10

(a) 114 (b) 240 (c) 1071

pH =

Reduction wave

(a) (b)

(c)

Curr

enti

(120583A

)


Figure 7 Cyclic voltammograms of chemically oxidized MG (50 times10minus4M MG + 29 times 10minus3M PbO

2+ H2SO4+ HClO

4) in aqueous

solution of KCl at different pH The pH was adjusted by aqueoussolution of H

2SO4or NaOHThe scan rate was 001 V sminus1

at 204 nm and 2530 nm Moreover a new absorption peakat 4520 nm appears due to the absorbance of the oxida-tive product of 3 31015840 5 51015840-tetramethylbenzidine 3 31015840 5 51015840-tetramethylbenzidine belongs to biphenyl group with thesimilar structure of TMB Therefore it can be inferred thatboth TMB and TMBOx are produced from the chemicaloxidation ofMGThe differences in the absorption band arisedue to the different position of alkyl substituent in benzidinering and the effect of solvent polarity

35 Diffusion Electron Transfer Kinetics and Surface ReactionRate of MG in the Absence and Presence of Surfactants Foran electrochemically irreversible diffusion-controlled systemthe diffusion coefficient can be evaluated by using [40]

1198941

pa = (299 times 105) 11989932(120572)1211986011988811986312

appV12 (1)

where 1198941pa is the anodic peak current in amperes at 25∘C 119899 isthe number of electrons taking part in the electrochemicalreaction 120572 is the electron transfer coefficient 119860 is thegeometric area of the electrode surface in m2 119863app is thediffusion coefficient of electroactive species in m2 sminus1 V is thepotential sweep rate in V sminus1 and 119888 is the concentration of thereactive species in the bulk of the solution in molmminus3 Theelectron transfer coefficient 120572 for an irreversible process canbe calculated from [40]

100381610038161003816100381610038161198641

pa minus 1198641

pa210038161003816100381610038161003816=477

119899 propmV (2)

where 1198641pa and 1198641

pa2 are the anodic peak potential and thepotential at which the current equals one half of the peakcurrent respectively A linear relationship between 1198941pa and

Wavelength (nm)200 300 400 500 600 700 800

Abs

orba

nce

00

01

02

03

04

(a)

(b)

(c)

(a)

(b)

(c)

Figure 8 UV-visible spectra of (a) 20 times 10minus6M MG in aqueoussolution of KCl without pH adjustment (b) 20 times 10minus6M MG inaqueous solution of KCl at pH 170 and (c) 50 times 10minus4M MGchemically oxidized by 10M H

2SO4+ 29 times 10minus3M PbO

2+ HClO

4

in aqueous solution of KCl at pH 170

V12 is apparent (Figure 4(a)) and the apparent diffusioncoefficient (119863app) of MG is calculated from (1) as 48 times 10minus11

m2 sminus1The study of kinetics of a reaction at an electrode

surface is important for fundamental understanding of theheterogeneous electron transfer process Since the oxidationprocess of MG is diffusion controlled the surface reactionrate constant (119896

119904) can be calculated from [13 37]

1198641

pa = 11986401015840+ 0780 + 05 ln(

119899120572119863app119865V

119877119879) minus ln 119896

119904119877119879

119899120572119865

(3)

where 1198641pa 11986401015840 and 119899 are anodic peak potential the formal

potential and number of electrons taking part in the ratedetermining step (=2 in the present case) respectively and119877 119879 120572 119863app 119865 and V stand for their usual meanings Alinear relationship holds for 1198641pa versus ln V The value of 119896

119904

can be obtained from the intercept of the straight line if thevalues of 119899 119863app and 119864

01015840are known The slope of 1198641pa versusln V evaluated from data of Figure 4(a) was 777 times 10minus3 Theoxidation of MG is an electrochemically irreversible processto make the direct measurement of the accurate value of11986401015840 difficult However the value of 11986401015840 could be obtained

from the intercept of the 1198641pa versus V plot on the ordinateby extrapolating the line to V = 0 following the methoddescribed in the literature [13 17] The parameters estimatedare 11986401015840 = 063V 120572 = 048 and 119896

119904= 276 times 10

minus3 sminus1The 119863app 120572 and 119896119904 are also evaluated for the peak O1

in the presence of surfactants CTAB and SDS Table 1 liststhe values of 119863app 120572 and 119896119904 for 50 times 10

minus4M MG in 010Maqueous solution of KCl in the presence of CTAB and SDS atvarious concentrations

The results demonstrated that the electrochemical param-eters of MG varied significantly with the addition of CTAB


Table 1119863app 120572 and 119896119904 of MG in the presence of surfactants CTABand SDS

Surfactants [Surfactant] times 103 M 119863apptimes1011

m2sminus1120572119896119904times 103

sminus1

CTAB

0005 64 048 105015 72 047 163025 94 047 179075 101 047 182100 98 047 188125 126 047 219500 151 047 229750 121 047 230

SDS

050 26 040 122100 20 049 099200 08 047 088300 06 047 060400 04 047 041500 03 047 020

and SDSThe addition of CTAB in aqueous solution increasesthe 119863app of MG up to 100 times 10minus3M of CTAB Above 100 times10minus3M of CTAB the 119863app increases slightly however the

value remains constant over the wide range of [CTAB] The119863app and 119896119904 of MG decrease appreciably with increasing SDSconcentration and in this case 120572 slightly varied at lowerconcentrations of SDS The possibility of MG incorporationin CTAB micelle can only be attributed to hydrophobicinteractions As the concentration of CTAB increases abovethe CMC the fixed amount ofMG is incorporated inmicellarcore and the micelle is then less diffusive towards electrodesurface On the other hand the presence of positive charge onthe amino group ofMG and its hydrophobic nature enhancesthe aggregation of MG with SDS The strength of interactionand binding between MG and SDS can partially affect thediffusion of MG in solution Moreover the formation ofan electrochemically inactive complex of MG with SDS canlower the concentration of free MG in the system to resultin the decrease of the peak current and hence the 119863app The119896119904value has been found to decrease with increasing SDS

while an opposite trend is observed for CTAB Zhu and Lialso [41] correlated such change in electrochemical para-meters with formation of electroactive or electrochemicallyinactive complexes The oxidation of hydrated MG is a diffu-sion-controlled electrochemically irreversible process anddepends on the various electrochemical parameters deter-mined by specific interactions and solubilization behavior ofthe media not merely on adsorption at the electrode inter-face

4 Conclusions

The micellization properties of surfactants in aqueous solu-tion have profound influence on the electrochemical behaviorof MG and the shapes of the cyclic voltammograms that

depend fairly on the concentration of the ionic surfactantsCTAB and SDS The electrochemical responses of MG atconcentrations below and above the CMC of surfactants aredistinctly different A sharp decrease in peak current for MGin aqueous SDS solution indicates a strong interaction ofMG with the surfactant while a slight increase is apparentin aqueous CTAB solution The electrochemical oxidation ofhydrated MG has been characterized as an electrochemicallyirreversible diffusion-controlled process The apparent diffu-sion coefficient and the surface reaction rate constant increasewith increase in CTAB concentration but an opposite trendis observed for SDS

Conflict of Interests

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

Acknowledgment

The authors gratefully acknowledge financial support fora subproject (CP-231) from the Higher Education QualityEnhancement Project of the University Grants Commissionof Bangladesh financed by the World Bank and the Govern-ment of Bangladesh

References

[1] S J Culp and F A Beland ldquoMalachite green a toxicologicalreviewrdquo International Journal of Toxicology vol 15 no 3 pp219ndash238 1996

[2] P Ngamukot T Charoenraks O Chailapakul S Motomizuand S Chuanuwatanakul ldquoCost-effective flow cell for the deter-mination of malachite green and leucomalachite green at aboron-doped diamond thin-film electroderdquoAnalytical Sciencesvol 22 no 1 pp 111ndash116 2006

[3] K K Karukstis and A V Gulledge ldquoAnalysis of the solva-tochromic behavior of the disubstituted triphenylmethane dyebrilliant greenrdquo Analytical Chemistry vol 70 no 19 pp 4212ndash4217 1998

[4] XNiuWZhangN Zhao andW Sun ldquoVoltammetric determi-nation of heparin based on its interactionwithmalachite greenrdquoBulletin of the Chemical Society of Ethiopia vol 22 no 2 pp162ndash172 2008

[5] KQu X Zhang Z Lv et al ldquoSimultaneous detection of diethyl-stilbestrol and malachite green using conductive carbon blackpaste electroderdquo International Journal of Electrochemical Sci-ence vol 7 no 3 pp 1827ndash1839 2012

[6] R M Uda and K Kimura ldquoMicroscopic location of photo-sensitive malachite Green surfactant in mixed micelle and itsphotoinduced enhancement of solubilizing powerrdquo Colloid andPolymer Science vol 285 no 6 pp 699ndash704 2007

[7] R C Kaye and H I Stonehill ldquoThe polarographic reduction ofcrystal-violet brilliant-green malachite-green and auraminerdquoJournal of the Chemical Society vol 618 pp 3231ndash3239 1952

[8] J Mata D Varade and P Bahadur ldquoAggregation behaviorof quaternary salt based cationic surfactantsrdquo ThermochimicaActa vol 428 no 1-2 pp 147ndash155 2005


[9] MN Khan andA Sarwar ldquoStudy of dye-surfactant interactionaggregation and dissolution of yellowish in N-dodecyl pyrid-inum chloriderdquo Fluid Phase Equilibria vol 239 no 2 pp 166ndash171 2006

[10] S M Chen J Y Chen and R Thangamuthu ldquoElectrochemicalpreparation of poly(malachite green) film modified Nafion-coated glassy carbon electrode and its electrocatalytic behaviortowards NADH dopamine and ascorbic acidrdquo Electroanalysisvol 19 no 14 pp 1531ndash1538 2007

[11] L Antonov G Gergov V Petrov M Kubista and J NygrenldquoUV-Vis spectroscopic and chemometric study on the aggrega-tion of ionic dyes in waterrdquo Talanta vol 49 no 1 pp 99ndash1061999

[12] A M R Kabir and M A B H Susan ldquoKinetics of the alkalinehydrolysis of crystal violet n aqueous solution influenced byanionic surfactantsrdquo Journal of Saudi Chemical Society vol 12no 4 pp 543ndash554 2008

[13] X Hu K Jiao W Sun and J-Y You ldquoElectrochemical andspectroscopic studies on the interaction ofmalachite greenwithDNA and its applicationrdquo Electroanalysis vol 18 no 6 pp 613ndash620 2006

[14] N S Kobotaeva E E Sirotkina and E V Mikubaeva ldquoElec-trochemical oxidation of tritane dyesrdquo Russian Journal ofElectrochemistry vol 42 no 3 pp 268ndash271 2006

[15] V V Perekotii Z A Temerdashev T G Tsyupko and E APalenaya ldquoElectrochemical behavior of crystal violet on glassycarbon electrodesrdquo Journal of Analytical Chemistry vol 57 no5 pp 448ndash451 2002

[16] J-P Song Y-J Guo S-M Shuang and C Dong ldquoStudy onthe inclusion interaction of ethyl violet with cyclodextrins byMWNTsNafion modified glassy carbon electroderdquo Journal ofInclusion Phenomena and Macrocyclic Chemistry vol 68 no 3-4 pp 467ndash473 2010

[17] B Xu K Jiao W Sun and X Zhang ldquoRecognition and deter-mination of DNA using victoria blue b as electrochemicalproberdquo International Journal of Electrochemical Science vol 2no 5 pp 406ndash417 2007

[18] Z Galus and R N Adams ldquoThe anodic oxidation of triphenyl-methane dyesrdquo Journal of the American Chemical Society vol86 no 9 pp 1666ndash1671 1964

[19] D A Hall M Sakuma and P J Elving ldquoVoltammetric oxi-dation of triphenylmethane dyes at platinum in liquid sulphurdioxiderdquo Electrochimica Acta vol 11 no 3 pp 337ndash350 1966

[20] M M Rahman M Y A Mollah M M Rahman and M AB H Susan ldquoElectrochemical behavior of malachite green on aglassy carbon electrode a cyclic voltammetric studyrdquo Journal ofBangladesh Chemical Society vol 24 no 1 pp 25ndash36 2011

[21] T Saji K Hoshino and S Aoyagui ldquoReversible formation anddisruption of micelles by control of the redox state of the headgrouprdquo Journal of the American Chemical Society vol 107 no24 pp 6865ndash6868 1985

[22] Y Takeoka T Aoki K Sanui N Ogata andMWatanabe ldquoEle-ctrochemical studies of a redox-active surfactant Correlationbetween electrochemical responses and dissolved statesrdquo Lang-muir vol 12 no 2 pp 487ndash493 1996

[23] M A B H Susan K Tani and M Watanabe ldquoSurface activityand redox behavior of nonionic surfactants containing ananthraquinone group as the redox-active siterdquo Colloid andPolymer Science vol 277 no 12 pp 1125ndash1133 1999

[24] M A B H Susan M Begum Y Takeoka and M WatanabeldquoEffect of pH and the extent of micellization on the redox

behavior of non-ionic surfactants containing an anthraquinonegrouprdquo Journal of Electroanalytical Chemistry vol 481 no 2 pp192ndash199 2000

[25] M A B H Susan M Begum Y Takeoka and M WatanabeldquoStudy of the correlation of the cyclic voltammetric responsesof a nonionic surfactant containing an anthraquinone groupwith the dissolved statesrdquoLangmuir vol 16 no 7 pp 3509ndash35162000

[26] M A Haque M M Rahman and M A B H Susan ldquoAqueouselectrochemistry of anthraquinone and its correlation with thedissolved states of a cationic surfactantrdquo Journal of SolutionChemistry vol 40 no 5 pp 861ndash875 2011

[27] M A Haque M M Rahman and M A B H Susan ldquoElec-trochemical behavior of anthraquinone in reverse micelles andmicroemulsions of cetyltrimethylammoniumbromiderdquo Journalof Solution Chemistry vol 41 no 3 pp 447ndash457 2012

[28] I Mahmud A J F Samed M A Haque and M A B HSusan ldquoElectrochemical behavior of anthraquinone in aqueoussolution in presence of a non-ionic surfactantrdquo Journal of SaudiChemical Society vol 15 no 3 pp 203ndash208 2011

[29] A Pedraza M D Sicilia S Rubio and D Perez-BenditoldquoDetermination of aromatic hydrotropic drugs in pharmaceu-tical preparations by the surfactant-binding degree methodrdquoAnalyst vol 130 no 7 pp 1102ndash1107 2005

[30] B Gohain B Boruah PM Saikia andR KDutta ldquoPremicellarand micelle formation behavior of aqueous anionic surfactantsin the presence of triphenylmethane dyes protonation of dye inion pairmicellesrdquo Journal of Physical Organic Chemistry vol 23no 3 pp 211ndash219 2010

[31] W Huang C Yang W Qu and S Zhang ldquoVoltammetricdetermination of malachite green in fish samples based on theenhancement effect of anionic surfactantrdquo Russian Journal ofElectrochemistry vol 44 no 8 pp 946ndash951 2008

[32] L Liu F Zhao F Xiao and B Zeng ldquoImproved voltammetricresponse ofmalachite green at amulti-walled carbon nanotubescoated glassy carbon electrode in the presence of surfactantrdquoInternational Journal of Electrochemical Science vol 4 no 4 pp525ndash534 2009

[33] K Yamamoto and S Motomizu ldquoLiquid-liquid distributionof ion-associates of acidic dyes with quaternary ammoniumcounter-ionsrdquo Talanta vol 38 no 5 pp 477ndash482 1991

[34] M Mukhopadhyay C Sen Varma and B B Bhowmik ldquoPhoto-induced electron transfer in surfactant solutions containingthionine dyerdquo Colloid and Polymer Science vol 268 no 5 pp447ndash451 1990

[35] W Biedermann and A Datyner ldquoThe interaction of nonionicdyestuffs with sodium dodecyl sulfate and its correlation withlipophilic parametersrdquo Journal of Colloid and Interface Sciencevol 82 no 2 pp 276ndash285 1981

[36] Z Galus and R N Adams ldquoAnodic oxidation studies of NN-dimethylaniline II Stationary and rotated disk studies at inertelectrodesrdquo Journal of the American Chemical Society vol 84no 11 pp 2061ndash2065 1962

[37] A J Bard and L R Faulkner Electrochemical Methods Fun-damental and Applications John Wiley amp Sons Beijing China2nd edition 2004

[38] R S Nicholson and I Shain ldquoTheory of stationary electrodepolarography single scan and cyclic methods applied to rever-sible irreversible and kinetic systemsrdquo Analytical Chemistryvol 36 no 4 pp 706ndash723 1964

[39] K Jiao T Yang and S Niu ldquoThin-layer spectroelectrochemicalstudy of 331015840551015840-tetramethylbenzidine at SnO

2F film optically


transparent electroderdquo Science in China B vol 47 no 4 pp 267ndash275 2004

[40] C M A Brett and A M O Brett Electrochemistry PrinciplesMethods and Applications Oxford University Press NewYorkNY USA 1994

[41] Z Zhu and N-Q Li ldquoElectrochemical studies of 910-anthra-quinone interacting with hemoglobin and determination ofhemoglobinrdquo Mikrochimica Acta vol 130 no 4 pp 301ndash3081999

Submit your manuscripts athttpwwwhindawicom

Chromatography Research International

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2013


Carbohydrate Chemistry

International Journal of

Hindawi Publishing Corporationhttpwwwhindawicom


Analytical ChemistryVolume 2013

ISRN Chromatography


Hindawi Publishing Corporation httpwwwhindawicom Volume 2013Hindawi Publishing Corporation httpwwwhindawicom Volume 2013

The Scientific World Journal

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2013


CatalystsJournal of

ISRN Analytical Chemistry


ElectrochemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2013


Advances in

Physical Chemistry

ISRN Physical Chemistry


SpectroscopyInternational Journal of


ISRN Inorganic Chemistry



Journal of

Chemistry


Inorganic ChemistryInternational Journal of


International Journal ofPhotoenergy


Analytical Methods in Chemistry

Journal of

Volume 2013

ISRN Organic Chemistry



Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014




The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of




Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International




CatalystsJournal of


N+ (CH3)2

(CH3)2

Scheme 1 Chemical structure of MG+

There are numerous reports on the study of the electro-chemical behavior of electroactive species in surfactant-basedorganized media in literature The electrochemical behaviorof redox-active surfactants containing different electroactivegroups has been found to be controllable by changing theconcentration of surfactants [21 22] Susan and coworkers[23ndash25] reported the solution behaviors of redox-activeamphiphiles linked with an anthraquinone group and cor-related the electrochemical behavior of anthraquinone withthe dissolved states of the nonionic surfactant Haque et al[26 27] studied the electrochemical responses of sodium saltof anthraquinone-2-sulphonic acid (AQS) on the dissolvedstates of the surfactant cetyltrimethylammonium bromide(CTAB) and found that the current-potential behavior isprofoundly influenced by the concentration of the surfactantand redox state of anthraquinone Similar observation wasreported for electrochemical behavior of AQS in a nonionicsurfactant Triton X-100 [28] Pedraza et al [29] showedthat opposite charges of dye and surfactant can form dye-surfactant complex in solution The behaviors of TPM dyesin different aqueous anionic surfactant solutionswere studiedby spectral measurements and it was reported that dye-surfactant ion pairs form at the surfactant concentrationswell below their critical micelle concentration (CMC) [30]Huang et al [31] also showed that the negatively-chargedsodium dodecyl benzene sulphonate interacts with positivelychargedMG and can accumulate onto carbon paste electrodesurface by electrostatic interaction On the other hand thecationic surfactant cetylpyridinium bromide (CPB) makesthe oxidation of MGmore difficult due to adsorption of CPBon the electrode surface [32] In similarly charged dye-micellesystems the electrostatic repulsion can be overcomeby stronghydrophobic interactions [33ndash35]

MG has two amino groups in its structure and is highlysoluble in waterThree phenyl rings in the structure offerMGstrong hydrophobic characteristics while the positive chargeof the dye provides the scope of interaction to varying extentwith cationic and anionic surfactants to different extent bothin the monomeric and micellized states These make MG anintriguing probe for electrochemical studies With a view tounderstanding the aqueous electrochemistry of MG and itsinteractions with ionic surfactants we therefore investigatedthe cyclic voltammetric behavior of MG at a glassy carbonelectrode (GCE) surface in aqueous solution and in presenceof ionic surfactants of CTAB and sodium dodecyl sulfate

(SDS) and compared electrochemical responses in differentmedia to correlate with the dissolved states of the surfactants

2 Experimental

21 Materials Malachite green oxalate ([(C23H25N2)

sdot(C2HO4)]2sdotC2H2O41198731198731198731015840 1198731015840-tetramethyl-4 41015840-diamin-

otriphenylcarbenium oxalate) from TCI Tokyo Japancetyltrimethylammonium bromide (CTAB) and sodiumdodecyl sulfate (SDS) from Merck and sulfuric acid(H2SO4) lead dioxide (PbO

2) perchloric acid (HClO

4) pot-

assium chloride (KCl) hydrochloric acid (HCl) and sodiumhydroxide (NaOH) from BDH were used as receivedwithout further purifications Solutions were prepared withdeionized water (conductivity 0055120583S cmminus1 at 25∘C) fromHPLC grade water purification systems (BOECO Germany)A sonicator (LU-2 Ultrasonic cleaner USA) was used toclean electrodes and to prepare stock solutions

22 Measurements Spectrophotometric measurements weremade with a double-beam Shimadzu UV-visible spectropho-tometer (model UV-1650 PC) by using quartz cells with1 cm path length Cyclic voltammetric measurements wereperformed with a computer-controlled electrochemical ana-lyzer (CHI 600D CH Instruments USA) A single compart-ment three-electrode cell containing a GCE with geometricarea of 0071 cm2 as the working electrode a silver-silverchloride (AgAgCl) electrode (100M KCl) as the referenceelectrode and a platinum coil as the counter electrode wereused for electrochemical measurements The surface of theworking electrode wasmirror polished with 005120583malumina(Buehler) before each run The electrochemical measure-ments were carried out using 010M KCl aqueous solution asthe supporting electrolyte A pHmeter (HM-26 S TOA elec-tronics Ltd Japan) was used for measurements of pH valuesof solutionsThe electrochemical and spectral measurementswere conducted at constant room temperature (25 plusmn 05∘C)

3 Results and Discussion

31 Dye-Surfactant Interaction of MG with CTAB and SDS inAqueous Solution The visible spectrum of MG in aqueoussolution shows a broad band at the absorption maximum of6175 nm (120576 = 100 times 105Mminus1 cmminus1) The absorption spectraof MG in aqueous solutions with change in concentrationof CTAB and SDS were measured and spectral analyseswere made to correlate dye-surfactant interaction with thedissolved states of the surfactants

Figure 1(a) represents the visible spectra of 10 times 10minus6MMG in 10 times 10minus4M aqueous solution of KCl at 25 plusmn 01∘C forCTABThe absorbance at the 120582max that is 6175 nm as a func-tion of [CTAB] profile is also presented in Figure 1(b) The120582max did not show any appreciable change with increasingconcentration of CTAB The absorbance at the 120582max on theother hand increases with increasing [CTAB] up to a con-centration of 025times10minus3Mafter which absorbance apparentlydecreases with further increase in [CTAB] (Figure 1(b))

Both MG and CTAB are positively charged and there-fore at low concentrations of CTAB electrostatic repulsion


Wavelength (nm)500 550 600 650 700

Abso

rban

ce

00

02

04

06

08

10

12

(1)

(2)

(3)

(4)

(1) 0(2) 025

(3) 100(4) 450


(a)

0 1 2 3 4 5 6

Abso

rban

ce at

617

5 nm

00

02

04

06

08

10

12


(b)









Wavelength (nm)

Abso

rban

ce

00

04

08

12

16

(1) 0(2) 20

(3) 80(4) 300

(1)

(2)

(3)

(4)

616

620

624

628

(1)

(2)

(3)

(4)

616

620

624

628

0 5 10 15 20 25 30

500 550 600 650 700 750

120582m

ax(n

m)

[SDS] times 103 M =

[SDS] times 103 (M)

(a)Ab

sorb

ance

at 6

175

nm

04

06

08

10

12

14

0 5 10 15 20 25 30[SDS] times 103 (M)

(b)


0102030405060708






Curr

enti

(120583A

)

050 120583A

020 120583A

100 120583A









0002040608minus40

minus30

minus20

minus10

0

10


Reduction wave

Anodic peak (O1)

Cathodic peak (R1)

I

VICurr

enti

(120583A

)


(a)

00010203040506070809

minus25

minus20

minus15

minus10

minus5

0

5


Reduction wave

Oxidation wave

Anodic peak 1 (O1)

Anodic peak 2 (O2)I

VICurr

enti

(120583A

)


(b)


N N+

H3C H3C

H3CH3CN+ N+

CH3

CH3

CH3

CH3

2eminus

TMBOx TMB











12shows only a


0002040608minus10

minus8

minus6

minus4

minus2

0

2

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

Curr

enti

(120583A

)


I

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

I

[CTAB]times 103 (M)

(a)

0002040608minus4

minus3

minus2

minus1

0

1

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

Curr

enti

(120583A

)


[SDS] times 103 (M)

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

[SDS] times 103 (M)

(b)




0 2 4 6 8 10 12030

032

034

036

038

040

042

044

CTABSDS

Hal

f wav

e pot

entia

lE12

(V v

ersu

s Ag

AgC

l)













030405060708minus6

minus4

minus2

0

2

4

6

8

10

(a) 114 (b) 240 (c) 1071

pH =

Reduction wave

(a) (b)

(c)

Curr

enti

(120583A

)



2+ H2SO4+ HClO

4) in aqueous





1198941

pa = (299 times 105) 11989932(120572)1211986011988811986312

appV12 (1)


100381610038161003816100381610038161198641

pa minus 1198641

pa210038161003816100381610038161003816=477

119899 propmV (2)

where 1198641pa and 1198641


Wavelength (nm)200 300 400 500 600 700 800

Abs

orba

nce

00

01

02

03

04

(a)

(b)

(c)

(a)

(b)

(c)



2+ HClO

4






1198641

pa = 11986401015840+ 0780 + 05 ln(

119899120572119863app119865V

119877119879) minus ln 119896

119904119877119879

119899120572119865

(3)



119904




119904= 276 times 10








m2sminus1120572119896119904times 103

sminus1

CTAB

0005 64 048 105015 72 047 163025 94 047 179075 101 047 182100 98 047 188125 126 047 219500 151 047 229750 121 047 230

SDS

050 26 040 122100 20 049 099200 08 047 088300 06 047 060400 04 047 041500 03 047 020




4 Conclusions





Acknowledgment


References










































2F film optically














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Wavelength (nm)500 550 600 650 700

Abso

rban

ce

00

02

04

06

08

10

12

(1)

(2)

(3)

(4)

(1) 0(2) 025

(3) 100(4) 450


(a)

0 1 2 3 4 5 6

Abso

rban

ce at

617

5 nm

00

02

04

06

08

10

12


(b)









Wavelength (nm)

Abso

rban

ce

00

04

08

12

16

(1) 0(2) 20

(3) 80(4) 300

(1)

(2)

(3)

(4)

616

620

624

628

(1)

(2)

(3)

(4)

616

620

624

628

0 5 10 15 20 25 30

500 550 600 650 700 750

120582m

ax(n

m)

[SDS] times 103 M =

[SDS] times 103 (M)

(a)Ab

sorb

ance

at 6

175

nm

04

06

08

10

12

14

0 5 10 15 20 25 30[SDS] times 103 (M)

(b)


0102030405060708






Curr

enti

(120583A

)

050 120583A

020 120583A

100 120583A









0002040608minus40

minus30

minus20

minus10

0

10


Reduction wave

Anodic peak (O1)

Cathodic peak (R1)

I

VICurr

enti

(120583A

)


(a)

00010203040506070809

minus25

minus20

minus15

minus10

minus5

0

5


Reduction wave

Oxidation wave

Anodic peak 1 (O1)

Anodic peak 2 (O2)I

VICurr

enti

(120583A

)


(b)


N N+

H3C H3C

H3CH3CN+ N+

CH3

CH3

CH3

CH3

2eminus

TMBOx TMB











12shows only a


0002040608minus10

minus8

minus6

minus4

minus2

0

2

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

Curr

enti

(120583A

)


I

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

I

[CTAB]times 103 (M)

(a)

0002040608minus4

minus3

minus2

minus1

0

1

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

Curr

enti

(120583A

)


[SDS] times 103 (M)

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

[SDS] times 103 (M)

(b)




0 2 4 6 8 10 12030

032

034

036

038

040

042

044

CTABSDS

Hal

f wav

e pot

entia

lE12

(V v

ersu

s Ag

AgC

l)













030405060708minus6

minus4

minus2

0

2

4

6

8

10

(a) 114 (b) 240 (c) 1071

pH =

Reduction wave

(a) (b)

(c)

Curr

enti

(120583A

)



2+ H2SO4+ HClO

4) in aqueous





1198941

pa = (299 times 105) 11989932(120572)1211986011988811986312

appV12 (1)


100381610038161003816100381610038161198641

pa minus 1198641

pa210038161003816100381610038161003816=477

119899 propmV (2)

where 1198641pa and 1198641


Wavelength (nm)200 300 400 500 600 700 800

Abs

orba

nce

00

01

02

03

04

(a)

(b)

(c)

(a)

(b)

(c)



2+ HClO

4






1198641

pa = 11986401015840+ 0780 + 05 ln(

119899120572119863app119865V

119877119879) minus ln 119896

119904119877119879

119899120572119865

(3)



119904




119904= 276 times 10








m2sminus1120572119896119904times 103

sminus1

CTAB

0005 64 048 105015 72 047 163025 94 047 179075 101 047 182100 98 047 188125 126 047 219500 151 047 229750 121 047 230

SDS

050 26 040 122100 20 049 099200 08 047 088300 06 047 060400 04 047 041500 03 047 020




4 Conclusions





Acknowledgment


References










































2F film optically














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


Wavelength (nm)

Abso

rban

ce

00

04

08

12

16

(1) 0(2) 20

(3) 80(4) 300

(1)

(2)

(3)

(4)

616

620

624

628

(1)

(2)

(3)

(4)

616

620

624

628

0 5 10 15 20 25 30

500 550 600 650 700 750

120582m

ax(n

m)

[SDS] times 103 M =

[SDS] times 103 (M)

(a)Ab

sorb

ance

at 6

175

nm

04

06

08

10

12

14

0 5 10 15 20 25 30[SDS] times 103 (M)

(b)


0102030405060708






Curr

enti

(120583A

)

050 120583A

020 120583A

100 120583A









0002040608minus40

minus30

minus20

minus10

0

10


Reduction wave

Anodic peak (O1)

Cathodic peak (R1)

I

VICurr

enti

(120583A

)


(a)

00010203040506070809

minus25

minus20

minus15

minus10

minus5

0

5


Reduction wave

Oxidation wave

Anodic peak 1 (O1)

Anodic peak 2 (O2)I

VICurr

enti

(120583A

)


(b)


N N+

H3C H3C

H3CH3CN+ N+

CH3

CH3

CH3

CH3

2eminus

TMBOx TMB











12shows only a


0002040608minus10

minus8

minus6

minus4

minus2

0

2

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

Curr

enti

(120583A

)


I

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

I

[CTAB]times 103 (M)

(a)

0002040608minus4

minus3

minus2

minus1

0

1

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

Curr

enti

(120583A

)


[SDS] times 103 (M)

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

[SDS] times 103 (M)

(b)




0 2 4 6 8 10 12030

032

034

036

038

040

042

044

CTABSDS

Hal

f wav

e pot

entia

lE12

(V v

ersu

s Ag

AgC

l)













030405060708minus6

minus4

minus2

0

2

4

6

8

10

(a) 114 (b) 240 (c) 1071

pH =

Reduction wave

(a) (b)

(c)

Curr

enti

(120583A

)



2+ H2SO4+ HClO

4) in aqueous





1198941

pa = (299 times 105) 11989932(120572)1211986011988811986312

appV12 (1)


100381610038161003816100381610038161198641

pa minus 1198641

pa210038161003816100381610038161003816=477

119899 propmV (2)

where 1198641pa and 1198641


Wavelength (nm)200 300 400 500 600 700 800

Abs

orba

nce

00

01

02

03

04

(a)

(b)

(c)

(a)

(b)

(c)



2+ HClO

4






1198641

pa = 11986401015840+ 0780 + 05 ln(

119899120572119863app119865V

119877119879) minus ln 119896

119904119877119879

119899120572119865

(3)



119904




119904= 276 times 10








m2sminus1120572119896119904times 103

sminus1

CTAB

0005 64 048 105015 72 047 163025 94 047 179075 101 047 182100 98 047 188125 126 047 219500 151 047 229750 121 047 230

SDS

050 26 040 122100 20 049 099200 08 047 088300 06 047 060400 04 047 041500 03 047 020




4 Conclusions





Acknowledgment


References










































2F film optically














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0002040608minus40

minus30

minus20

minus10

0

10


Reduction wave

Anodic peak (O1)

Cathodic peak (R1)

I

VICurr

enti

(120583A

)


(a)

00010203040506070809

minus25

minus20

minus15

minus10

minus5

0

5


Reduction wave

Oxidation wave

Anodic peak 1 (O1)

Anodic peak 2 (O2)I

VICurr

enti

(120583A

)


(b)


N N+

H3C H3C

H3CH3CN+ N+

CH3

CH3

CH3

CH3

2eminus

TMBOx TMB











12shows only a


0002040608minus10

minus8

minus6

minus4

minus2

0

2

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

Curr

enti

(120583A

)


I

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

I

[CTAB]times 103 (M)

(a)

0002040608minus4

minus3

minus2

minus1

0

1

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

Curr

enti

(120583A

)


[SDS] times 103 (M)

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

[SDS] times 103 (M)

(b)




0 2 4 6 8 10 12030

032

034

036

038

040

042

044

CTABSDS

Hal

f wav

e pot

entia

lE12

(V v

ersu

s Ag

AgC

l)













030405060708minus6

minus4

minus2

0

2

4

6

8

10

(a) 114 (b) 240 (c) 1071

pH =

Reduction wave

(a) (b)

(c)

Curr

enti

(120583A

)



2+ H2SO4+ HClO

4) in aqueous





1198941

pa = (299 times 105) 11989932(120572)1211986011988811986312

appV12 (1)


100381610038161003816100381610038161198641

pa minus 1198641

pa210038161003816100381610038161003816=477

119899 propmV (2)

where 1198641pa and 1198641


Wavelength (nm)200 300 400 500 600 700 800

Abs

orba

nce

00

01

02

03

04

(a)

(b)

(c)

(a)

(b)

(c)



2+ HClO

4






1198641

pa = 11986401015840+ 0780 + 05 ln(

119899120572119863app119865V

119877119879) minus ln 119896

119904119877119879

119899120572119865

(3)



119904




119904= 276 times 10








m2sminus1120572119896119904times 103

sminus1

CTAB

0005 64 048 105015 72 047 163025 94 047 179075 101 047 182100 98 047 188125 126 047 219500 151 047 229750 121 047 230

SDS

050 26 040 122100 20 049 099200 08 047 088300 06 047 060400 04 047 041500 03 047 020




4 Conclusions





Acknowledgment


References










































2F film optically














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0002040608minus10

minus8

minus6

minus4

minus2

0

2

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

Curr

enti

(120583A

)


I

0 2 4 6 824

26

28

30

32

Curr

enti

(120583A

)

I

[CTAB]times 103 (M)

(a)

0002040608minus4

minus3

minus2

minus1

0

1

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

Curr

enti

(120583A

)


[SDS] times 103 (M)

I0 2 4 6 8

02

06

10

14

Curr

enti

(120583A

)

[SDS] times 103 (M)

(b)




0 2 4 6 8 10 12030

032

034

036

038

040

042

044

CTABSDS

Hal

f wav

e pot

entia

lE12

(V v

ersu

s Ag

AgC

l)













030405060708minus6

minus4

minus2

0

2

4

6

8

10

(a) 114 (b) 240 (c) 1071

pH =

Reduction wave

(a) (b)

(c)

Curr

enti

(120583A

)



2+ H2SO4+ HClO

4) in aqueous





1198941

pa = (299 times 105) 11989932(120572)1211986011988811986312

appV12 (1)


100381610038161003816100381610038161198641

pa minus 1198641

pa210038161003816100381610038161003816=477

119899 propmV (2)

where 1198641pa and 1198641


Wavelength (nm)200 300 400 500 600 700 800

Abs

orba

nce

00

01

02

03

04

(a)

(b)

(c)

(a)

(b)

(c)



2+ HClO

4






1198641

pa = 11986401015840+ 0780 + 05 ln(

119899120572119863app119865V

119877119879) minus ln 119896

119904119877119879

119899120572119865

(3)



119904




119904= 276 times 10








m2sminus1120572119896119904times 103

sminus1

CTAB

0005 64 048 105015 72 047 163025 94 047 179075 101 047 182100 98 047 188125 126 047 219500 151 047 229750 121 047 230

SDS

050 26 040 122100 20 049 099200 08 047 088300 06 047 060400 04 047 041500 03 047 020




4 Conclusions





Acknowledgment


References










































2F film optically














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


030405060708minus6

minus4

minus2

0

2

4

6

8

10

(a) 114 (b) 240 (c) 1071

pH =

Reduction wave

(a) (b)

(c)

Curr

enti

(120583A

)



2+ H2SO4+ HClO

4) in aqueous





1198941

pa = (299 times 105) 11989932(120572)1211986011988811986312

appV12 (1)


100381610038161003816100381610038161198641

pa minus 1198641

pa210038161003816100381610038161003816=477

119899 propmV (2)

where 1198641pa and 1198641


Wavelength (nm)200 300 400 500 600 700 800

Abs

orba

nce

00

01

02

03

04

(a)

(b)

(c)

(a)

(b)

(c)



2+ HClO

4






1198641

pa = 11986401015840+ 0780 + 05 ln(

119899120572119863app119865V

119877119879) minus ln 119896

119904119877119879

119899120572119865

(3)



119904




119904= 276 times 10








m2sminus1120572119896119904times 103

sminus1

CTAB

0005 64 048 105015 72 047 163025 94 047 179075 101 047 182100 98 047 188125 126 047 219500 151 047 229750 121 047 230

SDS

050 26 040 122100 20 049 099200 08 047 088300 06 047 060400 04 047 041500 03 047 020




4 Conclusions





Acknowledgment


References










































2F film optically














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of




m2sminus1120572119896119904times 103

sminus1

CTAB

0005 64 048 105015 72 047 163025 94 047 179075 101 047 182100 98 047 188125 126 047 219500 151 047 229750 121 047 230

SDS

050 26 040 122100 20 049 099200 08 047 088300 06 047 060400 04 047 041500 03 047 020




4 Conclusions





Acknowledgment


References










































2F film optically














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


































2F film optically














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of














ISRN Chromatography






CatalystsJournal of






Advances in

Physical Chemistry








Journal of

Chemistry







Journal of

Volume 2013




Journal of

Spectroscopy










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

electrochemical behavior of malachite green in aqueous solutions

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