Copper nanoparticles decorated polyaniline-zeolite nanocomposite for the
nanomolar simultaneous detection of hydrazine and phenylhydrazine
Balwinder Kaur, Rajendra Srivastava*, and Biswarup Satpati
Supporting Information
1
Electronic Supplementary Material (ESI) for Catalysis Science & Technology.This journal is © The Royal Society of Chemistry 2015
Chronoamperometry study
Chronoamperometry was used to calculate the diffusion coefficient (D) and rate constant (k) for
the electro-catalytic reaction (Fig. S6-S7). Chronoamperograms were obtained at different
concentrations of analytes at a desired potential step (450 and 650 mV for PhZ and HZ,
respectively) (Fig. S6-S7). The plots of I verses t-1/2
exhibited straight lines for different
concentrations of analytes (Fig. S6-S7, inset a). Cottrell equation (Eq. 1) was used to calculate
the diffusion coefficient for various analytes investigated in this study.1
Ip = n F A D1/2
c/1/2
t1/2
(1)
Where Ip is the catalytic current of CuNPs(5%)-PANI-Nano-ZSM-5/GCE in the presence of
analyte, F is the Faraday constant (96485 C/mole), A is the geometric surface area of the
electrode (0.07 cm2), D is the diffusion coefficient (cm
2/s), c is the analyte concentration
(mol/cm3), and t is the time elapsed (s). The diffusion coefficients were found to be 8.4 × 10
−6
and 34.8 × 10−6
cm2/s for HZ and PhZ, respectively.
Chronoamperometry was also employed to calculate the rate constant (k) for electro-
catalytic reaction through Eq. 2. 2
IC/IL = 1/2
[1/2
erf (1/2
) + exp (-)/1/2
] (2) Where IC is the catalytic current of CuNPs(5%)-PANI-Nano-ZSM-5/GCE in the presence of
analyte, IL is the limiting current in the absence of analyte and = kC0t (C0 is the
bulk concentration of analyte) is the argument of the error function. In cases, where e
xceed 2, the error function is almost equal to 1 and the above equation can be reduced to:
IC/IL = 1/2
1/2
= 1/2
(kC0t)1/2
(3)
Where k, C0 and t are the catalytic rate constant (1/M s), analyte concentration (M), and time
elapsed (s), respectively. Eq. 3 can be used to calculate the rate constant of the catalytic process.
Based on the slope of IC/IL vs. t1/2
plot; k can be obtained for a given analyte concentration (Fig.
S6-S7, inset b). From the values of the slopes, an average value for k was obtained for the
2
oxidation of analyte. The rate constant values for electro-catalytic oxidation of HZ and PhZ were
found as 9.8 × 104
and 1.1 × 104
1/s M, respectively.
FT-IR investigation of synthesized materials
Figure S1 shows the FT-IR spectrum of PANI, Nano-ZSM-5, and PANI-Nano-ZSM-5 samples.
FT-IR absorption peaks at 1578 and 1497 cm-1
in PANI sample are due to C=C stretching of
quinoid and benzenoid ring in PANI.3, 4
The bands at 1300 and 825 cm-1
can be assigned to N–H
bending mode and out of plane deformation of C–H (benzene ring) in the PANI sample. The
strong peak at 1128 cm-1
is due to the degree of electron delocalization in PANI and stretching of
N=Q=N in quinoid (Q) ring.5
The characteristic band at 1236 cm-1
can be assigned to C-N•+
stretching vibration in PANI. The peaks at 1387 cm-1
can be assigned to the stretching vibrations
of secondary aromatic C-N. Peaks at 1050 and 700 cm-1
(due to S=O and S-O) confirm the
incorporation of sulfonate groups attached to the aromatic rings in PANI structure. Nano-ZSM-5
exhibited several common IR peaks at 800 cm−1
, 970 cm−1
, 1100 cm−1
, and 1230 cm−1
(Figure
S1).6
The absorption peak at 800 cm−1
is due to Si−O−Si symmetric stretching. The absorption
peaks at 1100 cm−1
and 1230 cm−1
are assigned to asymmetric stretching of Si−O−Si whereas
peak at 970 cm-1
is due to the incorporation of Al in the MFI framework and assigned to an
asymmetric stretching mode of a [SiO4] unit bonded to a M4+
ion (O3Si–O–M). Nano-ZSM-5-Pr-
NH2 exhibited IR peaks at 2930 and 2842 cm-1
, which are characteristics of asymmetric and
symmetric –CH2 stretching vibrations in the propyl chain, respectively.7
The absorption bands at
1596 and 1410 cm-1
are assigned to the bending mode of the -NH2 group and to the scissor
vibration of -NH, respectively. The absorption band at 1470 cm−1
is due to –CH2 bending
(scissoring) vibration. The C-N stretching frequency for the aminopropyl moiety is observed at
1189 cm-1
. A strong peak at 800 cm-1
represents the Si-O-Si bond symmetrical stretching
vibration.7
These observations confirmed the incorporation of propylamine moiety on the surface
of Nano-ZSM-5. The FT-IR spectrum for PANI-Nano-ZSM-5 exhibited the IR peaks
corresponding to both Nano-ZSM-5 and PANI phases which confirms the presence of both
phases in the PANI-Nano-ZSM-5 nanocomposite material.
3
PANI-Nano-ZSM-5
2800 2100 1400 700
Nano-ZSM-5-Pr-NH2 1088
2800 2100 1400 700
Nano-ZSM-5
1100
2800 2100 1400 700
PANI 1578
1497 1128
2800 2100 1400 700 Wavenumber (cm
-1)
Figure S1. FT-IR spectrum of different PANI/Nano-ZSM-5 materials investigated in the study.
4
70
0
149
7
15
78
14
70
97
0
800
1230
61
9
70
0 825
105
0
1236
13
00
13
87
1410
2842
800 1
189 159
6
2930
% T
ran
smit
tan
ce
(a.u
.)
130
12
30
0
TGA investigation of synthesized materials
Figure S2 shows the TGA curves for PANI-Nano-ZSM-5, Nano-ZSM-5-Pr-NH2, Nano-ZSM-5,
and conventional PANI. The first weight loss below 473 K in the TGA curves for all the samples
indicates the loss of physically adsorbed water molecules. The TGA curve for Nano-ZSM-5
showed no appreciable weight loss after 473 K, confirming that chemical composition did not
change in this temperature range. In the TGA curve for conventional PANI, the second sharp
weight loss between 533-603 K may be attributed to the evaporation or decomposition of few
unstable oligoanilines/dopants and the third weight loss after 603 K is attributed to the
decomposition of PANI polymer chains. The total weight loss of PANI was 100 % and
combustion of PANI in air stream was completed at 913 K. In the TGA curve for Nano-ZSM-5-
Pr-NH2, the second weight loss between 525-875 K can be attributed to the decomposition of
organic propylamine moiety anchored on the surface of Nano-ZSM-5 and the residual weight
refers to the content of Nano-ZSM-5 in Nano-ZSM-5-Pr-NH2. TGA analysis confirmed that
Nano-ZSM-5-Pr-NH2 contains 11 wt % functionalized organic group (-Pr-NH2). In the TGA
curve for PANI-Nano-ZSM-5, the combustion of PANI in air stream was completed at 913 K
and the residual weight refers to the content of Nano-ZSM-5 in the nanocomposite. TGA
confirms that PANI-Nano-ZSM-5 nanocomposite contains 40.7 wt % Nano-ZSM-5 and 43.8 wt
% PANI. Nano-ZSM-5/PANI weight ratio was found to be 0.93, which was very close to their
initial weight ratio.
5
PANI Nano-ZSM-5 Nano-ZSM-5-Pr-NH
2
PANI-Nano-ZSM-5
100
80
60
40
20
0
-20 400 600 800 1000 1200 1400
Temperature (K)
Figure S2. TGA thermograms of PANI, Nano-ZSM-5, PANI-Nano-ZSM-5-Pr-NH2, and PANI-
Nano-ZSM-5 materials at a heating rate of 10 K/min recorded in air stream.
6
Wei
gh
t (%
)
(a) PANI (b) Nano-ZSM-5
2 µm 2 µm
(c) PANI-Nano-ZSM-5
2 µm
Figure S3. SEM images for PANI, Nano-ZSM-5, and PANI-Nano-ZSM-5 materials.
7
Nano-ZSM-5/GCE
100 PANI/GCE PANI-Nano-ZSM-5/GCE
CuNPs(5%)-PANI-Nano-ZSM-5/GCE
50
0 30 Bare G CE
15
-50 0
-15
-100 -30
0.0 0.4 0.8 1.2
Potential (V)
-0.3 0.0 0.3 0.6 0.9 1.2 1.5
Potential (V)
Figure S4. CV responses of various modified electrodes (CuNPs(5%)-PANI-Nano-ZSM-5/GCE,
PANI-Nano-ZSM-5/GCE, PANI/GCE, Nano-ZSM-5/GCE) and bare GCE (Inset) in 0.1 M KCl
solution containing 1 mM of [Fe(CN)6]3-/4-
at a scan rate of 10 mV/s.
Cu
rren
t (
A)
Cu
rr
en
t (A
)
8
50
40
40 30
20
30 10
0
0 5 10 15 20 25
20 Scan rate
1/2 (mV
1/2s
-1/2)
PhZ (a)
50
40
30
20
40
30
20
10
0
0 5 10 15 20 25 Scan rate
1/2 (mV
1/2s
-1/2)
HZ (b)
10 10
0 0
-0.4 -0.2 0.0 0.2 0.4 0.6 0.8
Potential (V)
-0.2 0.0 0.2 0.4 0.6 0.8 1.0
Potential (V)
1.8 1.6 PhZ HZ
1.6
1.4
1.4
1.2 1.2
1.0 (c)
1.0 1.5 1.8 2.1 2.4 2.7 3.0 1.8
log v
(d)
2.1
log2.4 2.7 3.0
Figure S5. CVs at CuNPs(5%)-PANI-Nano-ZSM-5/GCE containing (a) PhZ (10 µM), (b) HZ
(10 µM) in 0.1 M PBS (pH 8.5) at various scan rates (10-600 mV/s). Inset shows the plot of
oxidation peak currents vs. square root of scan rates. (c)-(d) Plot of log Ip and log scan rate (ν)
for the electrochemical oxidation of (c) PhZ, and (d) HZ at CuNPs(5%)-PANI-Nano-ZSM-
5/GCE.
9
Cu
rren
t (
A)
Cu
rren
t (
A)
Cu
rren
t (
A)
Cu
rren
t (
A)
log
Ip
log
Ip
v
50
60 (a)
40 40
6
(b) 5
4
20
30 0
1.0 1.5 2.0 2.5 3.0
Time-1/2
(s-1/2
)
20
3
2
1 0.5 0.6 0.7 Time
1/2(s
1/2)
(iv)
10 (i)
0 0 10 20 30 40 50 60
Time (s)
Figure S6. Chronoamperograms obtained at CuNPs(5%)-PANI-Nano-ZSM-5/GCE (i) in the
absence and in the presence of (ii) 100 µM, (iii) 200 µM, and (iv) 300 µM of PhZ in 10 mL 0.1
M PBS (pH 8.5). Inset: (a) Dependence of current on the time-1/2
derived from the
chronoamperogram data. (b) Dependence of IC/IL on time1/2
derived from the data of
chronoamperograms.
10
I C/I
L
Cu
rren
t (
A)
Cu
rren
t (
A)
50 20 (a)
15
40 10
5
4
(b)
3
2
30 0
1.0 1.5 2.0 2.5 3.0
Time-1/2
(s-1/2
) 20
0.1 0.2 0.3 0.4 0.5
Time1/2
(s1/2
)
(iv)
10
(i)
0
0 10 20 30 40 50 60
Time (s)
Figure S7. Chronoamperograms obtained at CuNPs(5%)-PANI-Nano-ZSM-5/GCE (i) in the
absence and in the presence of (ii) 100 µM, (iii) 200 µM, and (iv) 300 µM of HZ in 10 mL 0.1 M
PBS (pH 8.5). Inset: (a) Dependence of current on the time-1/2
derived from the
chronoamperogram data. (b) Dependence of IC/IL on time1/2
derived from the data of
chronoamperograms.
11
I C/I
L
Cu
rren
t (
A)
Cu
rren
t (
A)
1
1.2 PhZ
(a)
1.0
0.8
0.6
0.4
0.10 0.15 0.20 0.25 0.30 Potential (V)
1.4 (b) 1.2
1.0
0.8
0.6
0.35 0.40 0.45 0.50
Potential (V)
30
20
10
0
-0.4 -0.2
30
0.0 0.2 0.4 0.6 0.8
Potential (V)
20
10
0
-0.2 0.0 0.2 0.4 0.6 0.8 1.0
Potential (V)
Figure S8. CVs of CuNPs(5%)-PANI-Nano-ZSM-5/GCE in the presence of 10 µM (a) PhZ and
(b) HZ in 0.1 M PBS (pH 8.5) at a scan rate of 50 mV/s. Inset shows the tafel plot of CV of 10
µM (a) PhZ and (b) HZ at a scan rate of 50 mV/s.
12
1.4
log
I (
A)
Cu
rren
t (
A)
log I
(
A)
HZ
Cu
rren
t (
A)
PhZ
HZ
12
9
6
3
0 2 4 6 8 10 12 14
pH
Figure S9. Influence of the pH on the oxidation peak currents of PhZ and HZ at CuNPs(5%)-
PANI-Nano-ZSM-5/GCE.
13
Cu
rren
t (
A)
CuNPs(3%)-PANI-Nano-ZSM-5/GCE
CuNPs(5%)-PANI-Nano-ZSM-5/GCE
CuNPs(6%)-PANI-Nano-ZSM-5/GCE CuNPs(10%)-PANI-Nano-ZSM-5/GCE
PhZ HZ
20
16
12
8
4
0 0.2 0.4
Pote 0.6
al (V) 0.8 1.0
Figure S10. DPVs in the presence of 5 µM each of PhZ and HZ in 10 mL of 0.1 M PBS (pH 8.5)
at CuNPs(3%)-PANI-Nano-ZSM-5/GCE, CuNPs(5%)-PANI-Nano-ZSM-5/GCE, CuNPs(6%)-
PANI-Nano-ZSM-5/GCE, and CuNPs(10%)-PANI-Nano-ZSM-5/GCE. DPV parameters were
selected as: pulse amplitude: 50 mV, pulse width: 50 ms, scan rate: 20 mV/s.
14
Cu
rren
t (
A)
nti
CuNPs(5%)-PANI-Nano-ZSM-5/GCE
CuNPs(5%)-Nano-ZSM-5/GCE
CuNPs(5%)-PANI/GCE PANI/GCE Nano-ZSM-5/GCE
Bare GCE
15
10
5
0
0.2 0.4 0.6 0.8 1.0
Potential (V)
Figure S11. Comparison of DPV of binary mixture containing 5 μM each of PhZ and HZ at
various modified electrodes (Cu(5%)-PANI-Nano-ZSM-5/GCE, Cu(5%)-Nano-ZSM-5/GCE,
Cu(5%)-PANI/GCE, PANI/GCE, Nano-ZSM-5/GCE) and bare GCE in 0.1 M PBS (pH 8.5).
DPV parameters were selected as: pulse amplitude: 50 mV, pulse width: 50 ms, scan rate: 20
mV/s.
15
Cu
rren
t (
A)
PANI-Nano-ZSM-5/GCE PANI-Nano-ZSM-5/GCE in Cu(II)
Nano-ZSM-5/GCE Nano-ZSM-5/GCE in Cu(II)
PANI/GCE PANI/GCE in Cu(II)
PhZ
HZ
15
10
5
0
0.0 0.2 0.4 0.6 0.8 1.0
Potential (V)
Figure S12. Comparison of DPV of binary mixture containing 5 μM each of PhZ and HZ at
various modified electrodes {in the presence of 50 μM CuCl2 in the electrochemical cell along
with PhZ and HZ (PANI-Nano-ZSM-5/GCE in Cu(II), Nano-ZSM-5/GCE in Cu(II), PANI/GCE
in Cu(II)) and in the absence of CuCl2 (PANI-Nano-ZSM-5/GCE, Nano-ZSM-5/GCE,
PANI/GCE)} in 0.1 M PBS (pH 8.5). DPV parameters were selected as: pulse amplitude: 50
mV, pulse width: 50 ms, scan rate: 20 mV/s.
16
Cu
rren
t (
A)
12 PhZ Electrode 1
Electrode 2
Electrode 3
Electrode 4
Electrode 5
6
4
0.2 0.4 0.6 0.8 1.0
Potential (V)
HZ Electrode 1
Electrode 2
Electrode 3
Electrode 4 8 Electrode 5
6
4
0.4 0.8 1.2 1.6 Potential (V)
12
10
8
6
4
2
0 1 2 3 4 5
Electrode Number
12
10
8
6
4
2
0 1 2 3 4 5
Electrode Number
Figure S13. The current response at different freshly prepared Cu(5%)-PANI-Nano-ZSM-
5/GCEs (n=5) in the presence of 1 µM each of (a) PhZ and (b) HZ. Inset shows corresponding
DPV curves at 5 different Cu(5%)-PANI-Nano-ZSM-5/GCEs in the presence of 1 µM each of
PhZ and HZ.
17
Cu
rren
t (
A)
10
Cu
rren
t (
A)
8
(a)
Cu
rren
t (
A)
10
Cu
rren
t (
A)
(b)
12 Measurment 1
Measurment 2 Measurment 3
Measurment 4
Measurment 5
6
3 0.2 0.4 0.6 0.8 1.0
Potential (V)
12 HZ Measurment 1
Measurment 2 Measurment 3
Measurment 4
8 Measurment 5
6
4
0.4 0.8 1.2 1.6 Potential (V)
12
9
6
3
0 1 2 3 4 5 6
Number of measurments 12
9
6
3
0 1 2 3 4 5 6
Number of measurments
Figure S14. The current response at five different measurements (20 days time period at the
interval of every 5 days) using same Cu(5%)-PANI-Nano-ZSM-5/GCE in the presence of 1 µM
each of (a) PhZ and (b) HZ. Inset shows corresponding DPV curves at 5 different measurements
using same Cu(5%)-PANI-Nano-ZSM-5/GCE in the presence of in the presence of 1 µM each of
PhZ and HZ for 20 days time period at the interval of every 5 days.
18
PhZ C
urren
t (
A)
9
Cu
rre
nt
(A
)
(a)
Cu
rren
t (
A)
10
Cu
rre
nt
(A
)
(b)
Table S1. Comparison of Cu(5%)-PANI-Nano-ZSM-5/GCE with other electrodes reported in
the literature for HZ and PhZ detection.
S.No.
Electrode material
Analyte
Linear range (M)
Detection
limit (M)
Reference
1.
Co3O4 nanowires
HZ
20 µM – 700 µM
500 nM
8
2.
4-((2-hydroxy phenyl
imino)methyl)benzen
e-1,2-diol-multi wall
carbon nanotube
HZ
4 µM – 750.4 µM
1.1 µM
9
3.
Au/HDT/4α-
NiIITAPc-AuNPs
HZ
10 µM – 100 µM
50 nM
10
4.
ZnO nanonails
HZ
0.1 µM – 1.2 µM
200 nM
11
5.
ZnO
nanorod/SWCNT
HZ
0.5 µM – 50 µM
170 µM
12
6.
Ni(OH)2–MnO2
HZ
5 µM – 18 mM
120 nM
13
7.
Flower shape CuO
PhZ
5 µM – 10 mM
1.9 µM
14
8.
Ag-doped ZnO
PhZ
10
-8 M – 10
3 M
5 nM
15
9.
poly(o-anisidine)
PhZ
1.5 µM – 38 µM
900 µM
16
10.
(2,2′[1,2 butanediyl
bis(nitriloethylidyne)
]-bis-hydroquinone
and TiO2
PhZ
HZ
2 µM – 1000 µM
75 µM – 1000 µM
0.75 µM
9 µM
17
11.
Cu(5%)-PANI-Nano-
ZSM-5
PhZ
HZ
4 nM – 800 µM
4 nM – 800 µM
1 nM
1 nM
This work
19
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20
