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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 spgoswamical@yahoo.com
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
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+
.
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
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
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
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.
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
5
ESI MS spectra of compound B:
Figure S3: ESI TOF mass spectra of the compound B.
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
6
1 H NMR spectra of the compound B:
Figure S4: 1H NMR (300 MHz) spectra of compound B in CDCl3.
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
7
1 H NMR spectra of the receptor:
Figure S5: 1H NMR (300 MHz) spectra of the receptor in CDCl3.
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
8
ESI MS spectra of the receptor:
Figure S6: ESI TOF mass spectra of the receptor.
RQ + H+
RQ + Na+
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
9
13C NMR spectra of the receptor:
Figure S7: 13
C NMR (100 MHz) spectra of the receptor in CDCl3.
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
10
Figure S8: Expansion mode of the 13
C NMR spectra of the receptor in CDCl3.
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
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+
.
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
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- ]+
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
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
Wavelength (nm)300 400 500 600
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)
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
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
Wavelength (nm)300 400 500 600
0.0
0.2
0.4Zn
2+
Ab
so
rban
ce
Wavelength (nm)
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
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
.)
Wavelength (nm)550 600 650
0
1x105
2x105
3x105
Mn2+
Inte
nsit
y (
a. u
.)
Wavelength (nm)
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013
16
550 600 6500
1x105
2x105
3x105
Ni2+
Inte
ns
ity
(a
. u
.)
Wavelength (nm)550 600 650
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)
Electronic Supplementary Material (ESI) for AnalystThis journal is © The Royal Society of Chemistry 2013