a highly selective and sensitive probe for - semantic scholar · 1 supporting information a highly...

1

Supporting Information

A highly selective and sensitive probe for

colorimetric and fluorogenic detection of Cd2+

in

aqueous media

Shyamaprosad Goswami,*a

Krishnendu Aicha, Sangita Das

a, Avijit Kumar Das

a, Abhishek

Mannaa and Sandipan Halder

b

aDepartment of Chemistry, Bengal Engineering and Science University, Shibpur, Howrah,

INDIA, 711 103, Tel. +91-33-2668 4561-3 ext. 498; Fax. +91-33-2668 2916.

e-mail [email protected]

bDepartment of Chemistry, Indian Institute of Technology, Kanpur, India

CONTENTS

1. General method of UV-vis and fluorescence titration ………………………2-3

2. Determination of detection limit………………………………………………..4

3. ESI MS spectrum of compound B…………………………………………………5

4. 1H NMR spectrum of compound B………………………………………………..6

5. 1H NMR spectrum of the receptor …………………………………………………7

6. Mass spectrum (ESI-MS) of the receptor ………………………………………….8

7. 13 C NMR spectrum of the receptor………………………………………………..9-10

8. IR spectra of the receptor and its Cd2+

complexes ……………… ……………… 11

9. ESI-MS spectrum of Cd2+

complex of the receptor…………………………………. 12

10. UV-vis titration spectra of the receptor with different guest cations………….... 13-14

10. Fluorescence titration spectra of the receptor with different guest cations ……...15-16

Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013

mailto:[email protected]

2

General method of UV-vis and fluorescence titration:

By UV-vis method

UV-vis spectra were recorded on a JASCO V-530 spectrophotometer using a dissolution cell of

10 mm path and the fluorescence spectra were recorded on a PTI spectrophotometer using a

fluorescence cell (10 mm). For UV-vis titrations, stock solution of receptor was prepared (c = 6 x

10-6

ML-1

) in CH3OH-H2O (1:4 v/v) in the presence of HEPES buffer solution (pH 7.1). For

fluorescence titrations, stock solution of receptor was prepared (c = 3 x 10-6

ML-1

) in CH3OH-

H2O (1:4 v/v) in the presence of HEPES buffer solution (pH 7.1). The solution of the guest

cations using their perchlorate salts in the order of 2 x 10-5

M were prepared in deionised water.

Solutions of various concentrations containing host and increasing concentrations of cations

were prepared separately. The spectra of these solutions were recorded by means of UV-vis

methods. Binding constant was calculated according to the Benesi-Hildebrand equation. Ka was

calculated following the equation stated below.

1/(A-Ao) = 1/{K(Amax–Ao) [Mx+

]n} + 1/[Amax-Ao]

Here Ao is the absorbance of receptor in the absence of guest, A is the absorbance recorded in

the presence of added guest, Amax is absorbance in presence of added [Mn+

]max and K is the

association constant. The association constant (K) could be determined from the slope of the

straight line of the plot of 1/(A-Ao) against 1/[Mx+

] and is found to be 1.656 x 10-5

M.

0 1x106

2x106

3x106

0

10

20

30

40

50

1 / (A

-A0

)

1 / [c]

Equation y = a + b*x

Adj. R-Square 0.99156

Value Standard Error

B Intercept 2.1806 0.31073

B Slope 1.31613E-5 2.71499E-7

Figure S1: Benesi-Hildebrand plot from absorption titration data of receptor (6 µM) with Cd2+

.


3

General procedure for drawing Job plot by UV–vis method

Stock solution of same concentration of the receptors and the guest were prepared in the order of

ca. 1.0 x 10-5

ML-1

CH3OH-H2O (1:4, v/v). The absorbance in each case with different host–

guest ratio but equal in volume was recorded. Job plots were drawn by plotting I.Xhost vs Xhost

(I = change of intensity of the absorbance spectrum during titration and Xhost is the mole

fraction of the host in each case, respectively).

By fluorescence method:

The binding constant value of Cd2+

with receptor has been determined from the emission

intensity data following the modified Benesi–Hildebrand equation,2 1//I = 1//I max

+(1/K[C])(1//I max). Here I = I-Imin and I max = Imax-Imin, where Imin, I, and Imax are

the emission intensities of receptor considered in the absence of Cd2+

, at an intermediate Cd2+

concentration, and at a concentration of complete saturation where K is the binding constant and

[C] is the Cd2+

concentration respectively. From the plot of [1 / (Imin –I)] against [C]-1

for

receptor, the value of K has been determined from the slope. The association constant (Ka) as

determined by fluorescence titration method for the receptor with Cd

2+ is found to be 6.808 x

105 M

-1 (error < 10%).

Figure S2: Benesi–Hildebrand plot from fluorescence titration data of receptor (3 µM) with

Cd2+

.

0 1x106

2x106

3x106

4x106

5x106

6x106

7x106

5.0x10-7

1.0x10-6

1.5x10-6

2.0x10-6

2.5x10-6

3.0x10-6

3.5x10-6

1 /

(I m

in-

I)

1 / [C]

Equation y = a + b*x

Adj. R-Square 0.99676

Value Standard Error

B Intercept 2.83651E-7 2.10658E-8

B Slope 4.1659E-13 7.91387E-15


4

Determination of detection limit:

The detection limit (DL) of RQ for Cd2+

was determined from the following equation:

DL = K* Sb1/S

Where K = 2 or 3 (we take 3 in this case); Sb1 is the standard deviation of the blank solution; S

is the slope of the calibration curve.

For UV-vis:

From the graph, we get slope = 43180.32, and Sb1 value is 0.010213

Thus using the formula we get the Detection Limit = 7.09 x 10-7

M i.e. RQ can detect Cd2+

in

this minimum concentration through UV-vis method.

For Fluorescence:

From the graph we get slope = 1.44 x 1012

, and Sb1 value is 94366.66

Thus using the formula we get the Detection Limit = 1.97 x 10-7

M i.e. RQ can detect Cd2+

in

this minimum concentration through fluorescence method.


5

ESI MS spectra of compound B:

Figure S3: ESI TOF mass spectra of the compound B.


6

1 H NMR spectra of the compound B:

Figure S4: 1H NMR (300 MHz) spectra of compound B in CDCl3.


7

1 H NMR spectra of the receptor:

Figure S5: 1H NMR (300 MHz) spectra of the receptor in CDCl3.


8

ESI MS spectra of the receptor:

Figure S6: ESI TOF mass spectra of the receptor.

RQ + H+

RQ + Na+


9

13C NMR spectra of the receptor:

Figure S7: 13

C NMR (100 MHz) spectra of the receptor in CDCl3.


10

Figure S8: Expansion mode of the 13

C NMR spectra of the receptor in CDCl3.


11

IR spectra of the receptor and its Cd2+

complex:

3500 3000 2500 2000 1500 1000 5000

20

40

60

80

100

120

140

% T

Wavenumber (Cm-1)

RQ

RQ + Cd2+

Figure S9: FT IR spectra of the receptor and its complex with Cd2+

.


12

ESI-MS of Cd2+

complex of the receptor:

Figure S10: ESI TOF mass spectra of the Cd2+

complex of the receptor.

[RQ + Cd2+ + Cl- ]+


13

UV-vis titration spectra of the receptor with different guest cations in CH3OH-HEPES

buffer solution (1:4, v/v, pH= 7.1):

300 400 500 6000.0

0.2

0.4Co

2+

Ab

so

rban

ce

Wavelength (nm)300 400 500 600

0.0

0.1

0.2

0.3Cr

3+

Ab

so

rban

ce

Wavelength (nm)

300 400 500 6000.0

0.1

0.2

Hg2+

Ab

so

rban

ce


0.0

0.2

0.4Cu

2+

Ab

so

rban

ce

Wavelength (nm)

300 400 500 6000.0

0.1

0.2

Fe2+

Ab

so

rban

ce

Wavelength (nm) 300 400 500 6000.0

0.2

0.4Fe

3+

Ab

so

rba

nc

e

Wavelength (nm)


14

300 400 500 6000.0

0.1

0.2

Hg2+

Ab

so

rba

nc

e

Wavelength (nm) 300 400 500 6000.0

0.1

0.2

Mg2+

Ab

so

rba

nc

e

Wavelength (nm)

300 400 500 6000.0

0.1

0.2

Mn2+

Ab

so

rba

nc

e

Wavelength (nm) 300 400 500 6000.0

0.1

0.2

0.3Ni

2+

Ab

so

rba

nc

e

Wavelength (nm)

300 400 500 6000.0

0.1

0.2

0.3Pb

2+

Ab

so

rban

ce


0.0

0.2

0.4Zn

2+

Ab

so

rban

ce

Wavelength (nm)


15

Fluorescence emission spectra of the receptor with different guest cations in CH3OH-

HEPES buffer solution (1:4, v/v, pH = 7.1):

550 600 6500

1x105

2x105

3x105

Co2+

Inte

ns

ity

(a

. u

.)

Wavelength (nm) 550 600 6500

1x105

2x105

3x105

4x105

Cr3+

Inte

ns

ity

(a

. u

.)Wavelength (nm)

550 600 6500

1x105

2x105

3x105

4x105

Cu2+

Inte

ns

ity

(a

. u

.)

Wavelength (nm)550 600 650

0

1x105

2x105

3x105

4x105

Fe2+

Inte

ns

ity

(a

. u

.)

Wavelength (nm)

550 600 6500

1x105

2x105

3x105

4x105

Hg2+

Inte

ns

ity

(a

. u

.)


0

1x105

2x105

3x105

Mn2+

Inte

nsit

y (

a. u

.)

Wavelength (nm)


16

550 600 6500

1x105

2x105

3x105

Ni2+

Inte

ns

ity

(a

. u

.)


0

1x105

2x105

3x105

Pb2+

Inte

ns

ity

(a

. u

.)

Wavelength (nm)

550 600 6500

1x105

2x105

3x105

4x105

5x105

6x105

Zn2+

Inte

nsit

y (

a. u

.)

Wavelength (nm)


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