Electronic Supplementary Material
Titanium dioxide nanotube arrays modified with a nanocomposite of silver nanoparticles
and reduced graphene oxide for electrochemical sensing
Wei Wanga, b, Yibing Xiea, b *, Chi Xiaa,b, Hongxiu Dua,b, Fang Tiana
a
School of Chemistry and Chemical Engineering, Southeast University, Nanjing 211189, China
b
Suzhou Research Institute of Southeast University, Suzhou 215123, China
*Corresponding author: E-mail address: ybxie@seu.edu.cn (Y. Xie)
Fig. S1. XRD patterns of (A) TiO2NTs/r-GO/AgNPs nanocomposite, (B) the standard data of JCPDS
card No. 04-0783 and (C) the standard data of JCPDS card No. 21-1272.
1
Fig. S2. Raman spectrum of TiO2NTs/r-GO.
2
Fig. S3. EDS spectrums of (A) TiO2NTs/AgNPs and (B) TiO2NTs/r-GO/AgNPs.
3
Optimization of pH
The nanocomposite and enzyme electrodes were used to determinate H2O2 and glucose, and pH
values of buffer solution were optimized. The cyclic voltammetry of the nanocomposite and enzyme
electrodes were investigated over the pH values from 5.8 to 7.8 in the N2-saturated 0.2 M phosphate
buffer solution containing 1.0 mM H2O2 and 0.5 mM glucose, respectively. Fig. S4 shows the effect
of pH on the reduction peak currents response. When the pH of the phosphate buffer solution was
very low or very high, the electrodes all exhibited low response current to H2O2 and glucose,
respectively. The optimum response currents could be found at pH 6.8. Therefore, the optimal pH of
6.8 was chosen in the further study.
4
Fig. S4. Effect of pH on the currents response of (A) 1.0 mM H2O2 at the nanocomposite electrode
and (B) 0.5 mM glucose at the enzyme electrode in N2-saturated 0.2 M phosphate buffer solution at
the scan rate of 50 mV s-1.
5
The effect of scan rate on the electrochemical response of the electrodes
The effect of scan rate on the electrochemical response of nanocomposite electrode was displayed in
Fig. S5. Cyclic voltammetry was run in N2-saturated phosphate buffer solution (pH 6.8) containing
1.0 mM H2O2, at different scan rates of 20, 40, 60, 80, 100, 150 and 200 mV s-1, respectively (Fig.
S5A). It is obvious that both redox peak currents were dependent on scan rate. Fig. S5B displayed
the redox peak currents are linear to the square root of scan rate value when the scan rate increased
from 20 to 200 mV s-1. The correlation coefficient (R2) was 0.9991 and 0.9995, respectively. The
result indicated that the redox reaction on the nanocomposite electrode was diffusion-controlled
electrochemical process [1].
Fig. S5. (A) Cyclic voltammograms of nanocomposite electrode at different scan rates (20, 40, 60,
80, 100, 150 and 200 mV s-1) in N2-saturated 0.2 M phosphate buffer solution (pH 6.8) containing
1.0 mM H2O2; (B) The plot of peak current in terms of square root of the scan rate value.
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Fig. S6. Current-time responses of (a) TiO2NTs electrode, (b) TiO2NTs/r-GO electrode, (c)
TiO2NTs/AgNPs electrode and (d) nanocomposite electrode to successive addition of 0.2 mM H2O2
in N2-saturated 0.2 M phosphate buffer solution (pH 6.8) at an applied potential of -0.6 V (vs. SCE).
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Fig. S7. (A) Current-time responses of the nanocomposite electrode to successive addition of H2O2
in N2-saturated 0.2 M phosphate buffer solution (pH 6.8) at an applied potential of -0.6 V (vs. SCE);
(B) The calibration curve of the nanocomposite electrode as a function of H2O2 concentration (The
inset figure shows the magnified plot of the low H2O2 concentration from 0.00 to 0.25 mM).
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Fig. S8. Stability analyses of the nanocomposite electrode. (A) Influence of electroactive
interferences of ascorbic acid, sucrose, L-histidine, glucose, dopamine and uric acid on the
nanocomposite electrode response, under an applied potential of -0.6 V (vs. SCE). (B) Long-term
stability of the nanocomposite electrode stored in dry condition at 4 °C.
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Fig. S9. Cyclic voltammogram of enzyme electrode in N2-saturated 0.2 M phosphate buffer solution
(pH 6.8) (a) without glucose, (b) with 500 μM glucose, (c) with 1000 μM glucose, at an applied scan
rate of 50 mV s-1.
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Table S1. Performance comparison of the nanocomposite electrode for H2O2 detection with other
sensors (GR = Graphene, r-GO = reduced graphene oxide, SWCNT = single wall carbon nanotubes,
GCE = glassy carbon electrode, NTs = nanotubes, NPs = nanoparticles).
Low
Linear range
Type of the electrode
Stability
Sensitivity
(current %)
(µA mM-1 cm-2)
detection
(mM)
limit (μM)
Reference
Pt-TiO2/r-GO
0-20
--
--
40
[2]
Ag@TiO2/GCE
0.00083-0.0433
0.83
98.5 (3 weeks)
65.23
[3]
Au-TiO2/GR
0.01-0.2
0.7
95 (15 days)
151.5
[4]
TiO2NTs/AgNPs
0.00075-11.16
0.0856
97.5 (60 days)
184.24
[5]
TiO2/Pd
0.01-0.86
3.81
--
226.72
[6]
Pt/TiO2/SWCNT
--
0.73
93 (15 days)
571.7
[7]
Our sensor
0.05-15.5
2.2
96.2 (60 days)
1151.98
This work
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Table S2. Experimental results for the detection of H2O2 in real serum samples.
Sample
H2O2 added (mM)
Found (mM)
Recovery (%)
1
1.0
1.03
103
2
2.0
1.97
98.5
3
3.0
2.91
97
4
4.0
4.05
101.3
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Table S3. Performance comparison of our enzyme electrode for glucose detection with other sensors
(GR = Graphene, GCE = glassy carbon electrode, HS = hollow spheres, NPs = nanoparticles).
Applied potential
Linear range
Sensitivity
(V)
(mM)
(µA mM-1 cm-2)
GR/CdS/GOx
--
2-16
1.76
[8]
GCE/TiO2-GR/GOx
-0.6 (vs. Ag/AgCl)
0-8
6.2
[9]
PET/Ti/Au/ZnO:Co/GOx
0.55 (vs. Ag/AgCl)
0-4
13.3
[10]
GOx/PEDOT-NiO HS
-0.45 (vs. SCE)
0-1.5
16.9
[11]
Pt/Rh/AuNPs-GOx-Nafion
0.35 (vs. Ag/AgCl)
0.05-15
68.1
[12]
GOx-GR/GC
-0.47 (vs. SCE)
0.1-10
110
[13]
Our sensor
-0.6 (vs. SCE)
0.05-0.3
257.79
This work
Type of the electrode
13
Reference
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