Supplementary Material for
Highly sensitive and selective electrochemical sensor for detection of vitamin B12 using an Au/PPy/FMNPs@TD-modified electrode Mohammad Hadi Parvina, Elmira Azizia, Jalal Arjomandi*a, b, Jin Yong Lee*b a
Department of Physical Chemistry, Faculty of Chemistry, Bu-Ali Sina University, 65178 Hamedan, Iran b
*
Department of Chemistry, Sungkyunkwan University, Suwon 16419, Korea
To whom correspondence should be addressed, E-mail:
[email protected],
[email protected], Tel: +82-031-299-4560, Fax: +82-031-290-7075
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-
-
Scheme S1 Acid/base and electrochemical pattern and change in axial ligandation in VB12 at various pH range in solution. 2
3
A
2 1
5
6
N
21
24
19 18
4
NH
22 23
D 17
16
15
N
N
14
7 8
B 9
10 11
C
12
13
Scheme. S2 C-5-C-15 axis in corrin ring
Fig. S1 spectroelectrochemical micro volume cell.
3
120 100
80
b
A
60 40
60
I/µA
I/µA
80
B
a
40
20 0
20
-20
0
-40
-20 -0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
-0.9
1
-0.5
-0.1
0.3
0.7
E vs V (SCE)
E vs V (SCE)
Fig. S2 (A) First CVs of a gold electrode for (a) PPy, (b) PPy/FMNPs@TD respectively, (B) multi sweep CVs during the growth of PPy/FMNPs@TD (26th cycle red line and 27th yellow line). Condition: in ACN/LiClO4 electrolyte at scan rate = 50 mV s-1
4
1.1
Fig. S3 Effect of pH solution on the Epc VB12 (Co (III)-Co (II)-Co (I) system at the Au/PPy/FMNPs@TD electrode in 0.5 M Britton-Robinson buffers solution containing: 5.0 mM VB12. CVs recorded in (A) pH=0-3, (B) pH=4-7, (C) pH=8-11, (D) pH=0-11 and (E) pH vs applied potential.
5
-7 -8
-10
Log KD
-9
-11 -12 -13 0
2
4
6
8
10
12
pH
Fig. S4 Variation of the disproportionation equilibrium constant; Co (III)-Co (II)-Co (I) system as a function of pH.
3.5 3.0
Absorbance
2.5 2.0 1.5 1.0 0.5 0.0 200
300
400
500
600
700
800
λ (nm)
Fig. S5 Spectroelectrochemistry of the VB12 (ΙΙΙ) and (ΙΙ) couple: variation of the spectrum with the electrode potential (pH 10).
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Fig S6. Cyclic voltammograms of VB12 on surface of an Au/PPy/FMNPs@TD at various scan rates (A), plot of current vs. scan rates (10–10000 mVs−1) at peak I (AI) and II (AII), variations of current for slow scan (10–180 mVs−1) at peak I (BI) and II (BII), and variations of current for fast scan (180–10000 mVs−1) at peak I (CI) and II (CII). Solution contains 5.0 mM of VB12 in 0.5 M Britton-Robinson Buffers solution with pH=7.0.
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Table S1 Electrochemical impedance spectroscopy details. Au Au/PPy Au/PPy/FMNPs@TD
R1 (Ω)
R2(Ω)
CPET(µF)
WR(Ωs-0.5)
80.69 81.25 81.05
1202 897.3 645.7
1.049 1.472 2.639
15.53 14.77 11.55
Table S2 Cyclic voltammetry details of VB12 Eca2 (V)
Ica2 (µA)
Ean2 (V)
Ian2 (µA)
ΔE (V)
Au/PPy/FMNPs@TD
-0.175
-3.40
-0.025
20.37
0.15
Au/PPy
-0.25
-2.16
0.025
16.81
0.27
-
-
0.150
6.37
-
Au
Eca1(V)
Ica1(µA)
Ean1(V)
Ian1(µA)
ΔE (V)
Au/PPy/FMNPs@TD
-0.901
-37.51
-0.720
7.06
0.18
Au/PPy
-0.925
-20.32
-0.725
7.97
0.20
Au
-0.925
-21.54
-0.725
3.26
0.20
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Table S3 Interference study for determination of VB12 under optimum conditions (n=3). Interference
Tolerance limit [interference] /[VB12]
Interference
Tolerance limit [interference] /[VB12]
Cd2+
610±30.3
Vitamin E
1250±60.0
Cu2+
810±39.6
Vitamin C
790±38.8
Fe2+
570±27.9
Thiourea
1320±63.3
Vitamin B6
790±38.6
Urea
1350±69.0
Vitamin A
1120±53.7
Sucrose
960±46.3
Glucose
890±43.2
Fructose
960±46.3
Table S4 Determination of VB12 in the supplement, milk and liver samples by the proposed sensor (n=5). Sample
milk
liver
Initial value
Found value by the
VB12 (µg)
proposed sensor (µg)
10
11.2±0.6
4.05
20
21.3±0.5
3.91
30
31.3±0.3
3.76
10
12.1±0.8
4.40
20
22.0±0.5
4.16
30
33.2±0.4
3.90
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RSD%
=
=
(
+
)
=
.
Eq. S1
=
Eq. S2
+
.
Eq. S3
=( −
)/(
−
)
( −
)=
=
=( −
) /(
−
)
( −
)=
=
( (
− −
) )
Eq. S4 Eq. S5
Equations S1-S5 Supporting for Fig. 5c and 5d, where, Eapplied is the applied potential using Nernst equation (Eq. 1S), [R]/[O] is concentration ratio of oxidized to reduced species, and
is the concentration of oxidized and reduced forms, A is absorbance of mixture, and
is the absorbance of the totally reduced and oxidized forms [1, 2].
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References [1] W. R. Heineman, Spectroelectrochemistry: The combination of optical and electrochemical techniques. Hybrid Analytical Techniques, 60 (1983) 305. [2] T. P. DeAngelis, W. R. Heineman, An electrochemical experiment using an optically transparent thin layer electrode. Journal of Chemical Education, 53 (1976) 594.
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