Electronic Supporting Information Detailed study of ... · Renu Sharma, Ajar Kamal and Rakesh Kumar Mahajan* *Department of Chemistry, UGC-Centre for Advanced Studies-I, Guru Nanak

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Electronic Supporting Information

Detailed study of interactions between eosin yellow and gemini pyridinium surfactants

Renu Sharma, Ajar Kamal and Rakesh Kumar Mahajan*

*Department of Chemistry, UGC-Centre for Advanced Studies-I, Guru Nanak Dev University,

Amritsar-143005, India

*To whom correspondence should be addressed:

e-mail: [email protected]; Fax: +91 183 2258820

Electronic Supplementary Material (ESI) for RSC Advances.This journal is © The Royal Society of Chemistry 2016

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Annexure SI

1. Methods

1.1 Conductivity measurements. The Conductivity measurements were carried out using a

digital Systronics conductivity meter model 306 with a dip-type conductivity cell at 298.15 K

having a cell constant of 1.01 cm-1

. All the solutions were prepared in deionised double distilled

water having specific conductivity of 2.0-3.0 µS cm-1

.

1.2 UV-visible measurements. The absorption spectra of eosin yellow (EY) and EY-gemini

pyridinium surfactants mixed systems were recorded on a UV-1800 Shimadzu

spectrophotometer with a quartz cuvette having a path length of 1 cm. The titrations were

performed at 298.15 K by successive additions of stock solutions of surfactants directly into the

quartz cuvette containing 2.0 mL of 0.001 mmol dm-3

EY solution. The spectra were recorded in

the range of 400-650 nm.

1.3 Fluorescence measurements. Fluorescence measurements were carried out using F-

1600 Hitachi spectrophotometer using a quartz cuvette having an optical length of 10 mm at

298.15 K. The emission spectrum of EY was recorded in the range of 530-650 nm at an

excitation wavelength of 518 nm. The titrations were performed same as done in UV-visible

measurements.

1.4 Voltammetric measurements. The voltammetric measurements were carried out on a

PC controlled CHI660D (Austin, USA) electrochemical workstation equipped with a

conventional three electrode system comprising of a working glassy electrode (3.0 mm in

diameter), a counter Pt wire and a reference Ag/AgCl electrode. All the solutions were

deoxygenated with N2 and working electrodes were polished with slurry of alumina powder.

These voltammetric measurements were carried out in the presence of 0.1 M KCl working as a

supporting electrolyte.

1.5 Potentiometric measurements. The potentiometric measurements were done by employing

an Equiptronics digital potentiometer, Model EQ-602 employing the following

electrochemical cell assembly:

Ag/AgCl 3M KCl Test Solution PVC

membrane

Internal Reference

Solution

3M KCl Ag/AgCl

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The neutral ion-pair complexes of gemini pyridinium surfactants and sodium

dodecylsulfate as [Cn-3(OH)-Cn] +DS ̄ , where n = 14, 16 were prepared by same procedure as

reported [1, 2]. Equimolar aqueous solutions of [Cn-3(OH)-Cn], n = 14, 16 and sodium

dodecylsulfate (SDS) were mixed and after continuous stirring for a considerable time, the white

precipitates of [Cn-3(OH)-Cn]+DS ̄ were obtained . The precipitates so obtained were washed

repeatedly with water to remove NaCl and recrystallized thrice from acetone. The PVC (176

mg), ion-pair (5 mg) and plasticizer (550 mg) were mixed and dissolved in minimum quantity of

THF. The resulting mixture was poured in 50-mm petri dish after removing the air-bubbles. The

solvent THF was allowed to evaporate at room temperature. The resulting membrane was cut to

required size and attached to PVC tubes with PVC glue and equilibrated in 1mM of respective

surfactant solution. The internal reference solution was 1mM of these surfactants in 1mM NaCl.

The given composition of the components used for membrane formation represents the best

system in terms of slope values, correlation coefficient, linear range and detection limit. The

EMF measurements were performed by titration method at 298.15 K in the presence of 1mM

NaCl solution.

1.6 Dynamic light scattering measurements. Dynamic light scattering measurements were

done using a Malvern Nano-ZS Zetasizer instrument employing a He-Ne laser (λ = 632 nm) at a

scattering angle of 173˚. The solutions of EY and EY-surfactants mixed systems were prepared

in doubly distilled water and filtered through a membrane filter with pore size of 0.45 μm prior

to each measurement. The temperature of the measurements was controlled to an accuracy of

±0.1°C using a built-in temperature controller.

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Annexure SII

The corrected absorbance (ΔA) represents the difference between the measured

absorbance (Aexp) and theoretical absorbance (Atheo) as per the equation (1) [3]

∆𝐴 = 𝐴𝑒𝑥𝑝 − 𝐴𝑡ℎ𝑒𝑜 (1)

Where Atheo is calculated taking into account the Beer-Lambert’s law i.e. the two

components do not interact with each other and hence the total absorbance of the mixture is

equal to the sum of their individual absorbances according to the equation (2)

𝐴𝑇ℎ𝑒𝑜 = 𝜀𝑆𝐶𝑆0𝑋𝑆 − 𝜀𝐷𝐶𝐷

0(1 − 𝑋𝑆) (2) (3)

Here εs and εD are the molar extinction coefficients and Cs0 and CD

0 are the concentrations

of the stock solutions of the gemini pyridinium surfactants and the dye, EY respectively,

whereas, Xs represents the volume fraction of gemini pyridinium surfactants. The formation of

dye-surfactant complexes makes the absorbance of the solution to satisfy the following equation

(3):

𝐴𝑒𝑥𝑝 = 𝜀𝑆𝐶𝑆 + 𝜀𝐷𝐶𝐷 + 𝜀𝑆−𝐷𝐶𝑆−𝐷 (3)

Where εS-D is the molar extinction coefficient of the complex (Dye-surf) and CS, CD and

CS-D are the concentrations of the respective species in the mixture.

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System C1(mmol dm-3

) C2 = cmc(mmol dm-3

)

[14-3(OH)-14] - 0.022

EY+[14-3(OH)-14] 0.001 0.017

[16-3(OH)-16] - 0.003

EY+[16-3(OH)-16] 0.001 0.002

EY + [14-3(OH)-14]

C / mmol dm-3

0.025a 0.002

b 0.010

b 0.025

b

Dh / nm 82.5 58.8 91.3 220.2

EY + [16-3(OH)-16]

C / mmol dm-3

0.003a 0.0005

b 0.0010

b 0.0030

b

Dh / nm 91.3 78.8 122.4 342.0

a In the absence of EY,

b in the presence of 0.001 mmol dm

-3 EY

Table S1. The concentration corresponding to ion-pair formation (C1), critical micelle

concentration C2 (cmc) of gemini pyridinium surfactants, [14-3(OH)-14] and [16-3(OH)-16]

surfactants in the absence and presence of EY determined from potentiometric measurements.

Table S2. Hydrodynamic diameters (Dh) for EY-gemini pyridinium surfactants mixed

systems at different concentration of gemini pyridinium surfactants, [14-3(OH)-14] and

[16-3(OH)-16] in the absence and presence of EY.

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0.0 1.0x10-6

2.0x10-6

3.0x10-6

4.0x10-6

5.0x10-6

0

10

20

30

40

50

C1

C2(cmc)

0.00 1.50x10-6

3.00x10-6

4.50x10-6

1.0

1.5

2.0

2.5

3.0

/

S

cm

-1

C / mol dm-3

/

S

cm

-1

0.0002 mmol dm-3

0.0005 mmol dm-3

0.0010 mmol dm-3

C / mol dm-3

[16-3(OH)-16]

Fig.S1 Variation of specific conductivity (κ) with molar concentration of gemini pyridinium

surfactant, [16-3(OH)-16] in the presence of varying amounts of EY and the inset shows the

variation of specific conductivity (κ) with molar concentration of pure [16-3(OH)-16] in

aqueous solution.

450 500 550 600

0.0

0.4

0.8

1.2

1.6

2.0

Ab

sorb

an

ce

Wavelength / nm

0.001 mmol dm-3

0.005 mmol dm-3

0.010 mmol dm-3

0.020 mmol dm-3

Fig.S2 UV-visible spectra of EY at different concentrations

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450 500 550 600

0.00

0.05

0.10

0.15

0.20

0.25

Ab

sorb

an

ce

Wavelength / nm

0.0000mmol dm-3

0.0002mmol dm-3

0.0004mmol dm-3

0.0006mmol dm-3

0.0007mmol dm-3

0.0009mmol dm-3

0.0010mmol dm-3

0.0015mmol dm-3

0.0020mmol dm-3

0.0030mmol dm-3

(A) [16-3(OH)-16]

Fig.S3 (A) UV-visible spectra of 0.001 mmol dm

-3 EY in the presence of increasing concentrations

of gemini pyridinium surfactant, [16-3(OH)-16] (B) Job’s plot depicting 1:1 stoichiometry of EY-

[16-3(OH)-16] mixed system.

0.0 0.2 0.4 0.6 0.8 1.0

-0.5

-0.4

-0.3

-0.2

-0.1

0.0

0.1

Xsurf

A

(B) [16-3(OH)-16]

540 560 580 600 620 640

0

50

100

150

200

250

300

350

540 560 580 600 620 6400

1

2

3

4

5

6

7

8

Wavelength / nm

Flu

ore

scen

ce I

nte

nsi

ty

Wavelength / nm

Flu

oresc

en

ce I

nte

nsi

ty

Fig.S4 Fluorescence emission spectra of 0.001 mmol dm

-3 EY in the presence of increasing

concentrations of gemini pyridinium surfactant, [16-3(OH)-16].

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-1.4 -1.2 -1.0 -0.8

-1.0x10-5

-8.0x10-6

-6.0x10-6

-4.0x10-6

-2.0x10-6

0.0

2.0x10-6

(A) [16-3(OH)-16]

Potential / V

I p /

A

-1.4 -1.2 -1.0 -0.8

-1.0x10-5

-8.0x10-6

-6.0x10-6

-4.0x10-6

-2.0x10-6

(B) [16-3(OH)-16]

I p /

A

Potential / V

Fig.S5 (A) Cyclic voltammograms of EY in the presence of increasing concentrations of

gemini pyridinium surfactant, [16-3(OH)-16] (B) Differential pulse voltammograms of EY in

the presence of increasing concentrations of [16-3(OH)-16]

-1.4 -1.2 -1.0 -0.8

-1.0x10-5

-8.0x10-6

-6.0x10-6

-4.0x10-6

-2.0x10-6

0.0

2.0x10-6

(A) 0.005 mmol dm-3

[14-3(OH)-14] in EY

I p /

A

Potential / V

0.01 V

0.02 V

0.03 V

0.04 V

0.05 V

-1.4 -1.2 -1.0 -0.8

-6.0x10-6

-4.0x10-6

-2.0x10-6

0.0 (B) 0.010 mmol dm

-3

[14-3(OH)-14] in EO

Potential / V

0.01 V

0.02 V

0.03 V

0.04 V

0.05 V

I p /

A

-1.4 -1.2 -1.0 -0.8

-8.0x10-6

-6.0x10-6

-4.0x10-6

-2.0x10-6

0.0

2.0x10-6

(C) 0.030 mmol dm-3

[14-3(OH)-14] in EYI p

/ A

0.01 V

0.02 V

0.03 V

0.04 V

0.05 V

Potential / V

Fig.S6 Cyclic voltammogram (CV) of gemini pyridinium surfactants in EY at various scan rates (A)

0.005 mmol dm-3

[14-3(OH)-14] (B) 0.010 mmol dm-3

[14-3(OH)-14] (C) 0.030 mmol dm-3

[14-3(OH)-14].

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-1.4 -1.2 -1.0 -0.8

-1.0x10-5

-8.0x10-6

-6.0x10-6

-4.0x10-6

-2.0x10-6

0.0

2.0x10-6

(A) 0.0005 mmol dm-3

[16-3(OH)-16] in EY

I p /

A

Potential / V

0.01 V

0.02 V

0.03 V

0.04 V

0.05 V

-1.4 -1.2 -1.0 -0.8

-1.0x10-5

-8.0x10-6

-6.0x10-6

-4.0x10-6

-2.0x10-6

0.0

2.0x10-6

(B) 0.010 mmol dm-3

[16-3(OH)-16] in EY

0.01 V

0.02 V

0.03 V

0.04 V

0.05 VI p

/ A

Potential / V

-1.4 -1.2 -1.0 -0.8

-8.0x10-6

-6.0x10-6

-4.0x10-6

-2.0x10-6

0.0

2.0x10-6 (C) 0.0004 mmol dm

-3

[16-3(OH)-16] in EY

I p /

A

Potential / V

0.01 V

0.02 V

0.03 V

0.04 V

0.0 5.0x105

1.0x106

1.5x106

2.0x106

0.0

-5.0x105

-1.0x106

-1.5x106

1/C

1/

p

[14-3(OH)-14]

[16-3(OH)-16](B)

0.0 5.0x105

1.0x106

1.5x106

2.0x106

2.5x106

0

50

100

150

(A) [14-3(OH)-14]

[16-3(OH)-16]

1/C

1/

Fig.S8 Binding constant determination for the EY-gemini pyridinium surfactants mixed

systems using (A) changes in UV-visible spectra of EY (B) changes in the peak current of EY.

Fig.S7 Cyclic voltammogram (CV) of gemini pyridinium surfactants in EY at various scan rates (A)

0.0005 mmol dm-3

[16-3(OH)-16] (B) 0.0020 mmol dm-3

[16-3(OH)-16] (C) 0.0040 mmol dm-3

[16-3(OH)-16]

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-7.5 -7.0 -6.5 -6.0 -5.5

-0.20

-0.15

-0.10

-0.05

0.00

0.05[16-3(OH)-16]

0.000 mmol dm-3

0.001 mmol dm-3

EM

F /

V

log C / mol dm-3

(A)

-7.5 -7.0 -6.5 -6.0 -5.5

5.0x1011

5.5x1011

6.0x1011

6.5x1011

7.0x1011

7.5x1011

8.0x1011

8.5x1011

9.0x1011

9.5x1011

(B) [HEC16OPyBr]

v

log C / mol dm-3

Fig.S9 (A) EMF as a function of logarithm of molar concentration of gemini pyridinium

surfactant, [16-3(OH)-16] in the absence and presence of 0.001 mmol dm-3

EY (B) Binding

isotherms of binding parameter (v) versus logarithm of molar concentration of [16-3(OH)-16] in

the presence of 0.001 mmol dm-3

EY.

450 500 550 600

0.00

0.03

0.06

0.09

0.12

0.15

Ab

sorb

an

ce

Wavelength / nm

Fig.S10 Representative spectral decomposition stratergy for deconvolution of EY

absorbance spectra into Gaussian shapes.

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References

[1] A. Shaheen, I. Kaur, R.K Mahajan, Potentiometric studies of micellization behavior of

cationic surfactants in the presence of glycol additives and triblock polymer (Pluronic

F68), using surfactant-selective sensors based on neutral ion-pair complexes. Ind. Eng.

Chem. Res. 2007, 46, 4706-4709.

[2] R.K. Mahajan, A. Shaheen, Effects of various additives on the performance of a newly

developed PVC based potentiometric sensor for anionic surfactants. J. Colloid Interface

Sci. 2008, 326, 191-195.

[3] S. Gokturk, M. Tuncay, Dye-surfactant interaction in the pre-micellar region. J. Surf.

Deterg. 2003, 6, 325-330