Electrocatalytic synthesis of poly(2,6-diaminopyridine) on reduced graphene oxide and its application in glucose sensing

Article abstract of DOI:10.1039/c5ra07345f

Reduced graphene oxide (RGO) was prepared via electrochemical reduction of graphene oxide (GO), and it can effectively catalyze the polymerization of 2,6-diaminopyridine. Poly(2,6-diaminopyridine) (PDAP) deposited on RGO (PDAP-RGO) has good electroactivity in a wide pH range until pH 11.0. Due to the electrocatalytic reduction of H₂O₂ at the PDAP-RGO, a platform for glucose sensing was constructed by immobilizing glucose oxidase (GOD) into the PDAP-RGO. The proposed glucose sensor exhibited a wide linear range from 0.05 to 6.65 mM, a low detection limit of 0.142 μM, a good reproducibility and stability. The apparent Michaelis-Menten constant of GOD was also calculated based on the relationship between steady-state current and glucose concentration.

Full text of DOI:10.1039/c5ra07345f

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Electrocatalytic synthesis of poly(2,6-diaminopyridine) on reduced
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DOI: 10.1039/C5RA07345F
graphene oxide and its application in glucose sensing
Yong Qin,a Jie Yuan,a Jianfeng Ma,a Yong Kong,a,* Huaiguo Xue,b,* and Yonggang Pengc
5
Received (in XXX, XXX) Xth XXXXXXXXX 200X, Accepted Xth XXXXXXXXX 200X
First published on the web Xth XXXXXXXXX 200X
DOI: 10.1039/b000000x
Reduced graphene oxide (RGO) was prepared via electrochemical reduction of graphene oxide (GO),
and it can effectively catalyze the polymerization of 2,6-diaminopyridine. Poly(2,6-diaminopyridine)
10 (PDAP) deposited on RGO (PDAP-RGO) has good electroactivity in a wide pH range till pH 11.0.
Due to the electrocatalytic reduction of H2O2 at the PDAP-RGO, a platform for glucose sensing was
constructed by immobilizing glucose oxidase (GOD) into the PDAP-RGO. The proposed glucose
sensor exhibited a wide linear range from 0.05 to 6.65 mM, a low detection limit of 0.142 μM, a
good reproducibility and stability. The apparent Michaelis-Menten constant of GOD was also
15 calculated based on the relationship between steady-state current and glucose concentration.
2,6-Diaminopyridine and natural graphite powder (99.95%, 8000
Introduction
mesh) were purchased from Sinopharm Chemical Reagent Co.,
Ltd. (Shanghai, China). All other chemicals were of analytical
grade and used as received. The solutions were prepared with
55 ultrapure water (18.2 MΩ). The human blood serum samples
were obtained from Changzhou No.2 People’s Hospital, and the
experiments involving them were carried out in line with the
institutional guidelines of Changzhou/Yangzhou University and
consent was obtained for their use from Changzhou No.2
60 People’s Hospital. All electrochemical experiments including CV
and chronoamperometry were carried out on a CHI 660D
electrochemical workstation (Beijing, China). SEM images of
different samples were recorded with a model JSM-6360LA
scanning electron microscope (Japan). The FT-IR and Raman
65 spectra of GO and PDAP-RGO were recorded on a FTIR-8400S
spectrometer (Shimadzu, Japan) and a HR EVOLUTION Raman
microscope (Jobin Yvon, France), respectively.
Since the discovery of polyacetylene at the end of 1970s,1
conducting polymers (CPs) have attracted increasingly great
attention due to their unique optical, electrical and magnetic
20 properties. Among various monomers suitable for the synthesis of
CPs, 2,6-diaminopyridine, which chemical structure is similar to
m-phenylenediamine, is an ideal candidate to be polymerized.2
In fact, several previous work on the electrosynthesis of
poly(2,6-diaminopyridine) (PDAP) have been reported.3-5
25 Graphene (G), a single layer of sp2 bonded carbon atoms, has
attracted a great deal of attention because of its high electrical
conductivity, large specific surface area and excellent mechanical
strength.6-8 Recently, the electrocatalytic polymerization and
copolymerization of aniline and its derivatives on reduced
30 graphene oxide (RGO) modified electrode have been reported by
Mu et al.9,10 and our group.11,12 Due to the synergistic effect of
CPs and G, numerous work on CPs-G (RGO) based glucose
sensors, such as polyaniline-G,13 polypyrrole-G,14 and poly(3,4-
ethylenedioxythiophene)-G15 have been reported.
35 Herein, we investigated the electrocatalytic effect of RGO for
the electrosynthesis of PDAP, and the obtained PDAP film
deposited on RGO (PDAP-RGO) was characterized by scanning
electron microscopy (SEM) and cyclic voltammetry (CV). The
as-prepared PDAP-RGO exhibited an improved pH dependence
40 compared with PDAP electrodeposited directly on glassy carbon
electrode (PDAP-GCE), i.e., PDAP-RGO has good
electroactivity in a wider pH range than PDAP-GCE. More
interestingly, the PDAP-RGO showed obvious electrocatalysis
towards the reduction of H2O2 due to the synergistic effect of
45 RGO and PDAP. And therefore, a sensitive glucose sensing
platform was constructed by immobilizing glucose oxidase (GOD)
into the PDAP film, and the analytical performances of the novel
glucose sensor were also investigated in detail.
Preparation of RGO modified GCE
Graphene oxide (GO) was prepared from natural graphite powder
70 according to an improved Hummers’ method,16 and the dialysis
of GO was carried out for one week to remove the residual acids
and salts. GO dispersion was obtained by sonicating 10 mg GO in
10 mL ultrapure water for 90 min, and then 5 μL GO dispersion
(1 mg mL-1) was dropped onto the surface of a GCE (3 mm in
75 diameter) and left to dry in ambient air. Finally, the GO modified
GCE was electrochemically reduced at –1.0 V for 1 h in 0.1 M N2
saturated PBS (pH 7.0),17,18 and RGO modified GCE was
obtained.
Electrocatalytic synthesis of PDAP on RGO modified GCE
80 Electrosynthesis of PDAP-RGO was carried out in a solution of
0.1 M NaOH containing 0.1 M NaH2PO4 and 20 mM 2,6-
diaminopyridine by CV in a conventional three-electrode cell,
which consists of the RGO modified GCE as the working
electrode, a platinum foil as the auxiliary electrode and a
85 saturated calomel electrode (SCE) as the reference electrode. The
cycling potential was controlled in the range between 0 and 1.4 V
Experimental
50 Reagents and apparatus
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Page 2 of 6
at the scan rate of 100 mV s-1, and the electrolysis was finished
Characterization of PDAP-RGO
View Article Online
after 20 cycles. After that, the deposited PDAP film was washed
with water to remove unreacted monomers, and then dried in
ambient air. For a control experiment, PDAP-GCE was prepared
by the same procedure using GCE as the working electrode.
DOI: 10.1039/C5RA07345F
SEM images of PDAP-GCE and PDAP-RGO are shown in Fig.
2A and Fig. 2B, respectively. It is found that compared with
PDAP-GCE, PDAP-RGO exhibits a more compact morphology
60 without obvious embedded cavities, indicating that the existence
of RGO is beneficial to the formation of compact and uniform
PDAP film.
5
Construction of glucose sensing platform
A volume of 5 μL 1 mg mL-1 glucose oxidase (GOD) solution
was dropped onto the surface of the as-prepared PDAP film
and dried at room temperature. Next, 5 μL of 0.5% Nafion
10 solution was dropped onto the surface of the GOD
immobilized PDAP film to maintain the stability of the
glucose sensor. The prepared glucose sensor was stored at 4
°C in a refrigerator when not in use. The chronoamperometric
responses of glucose at the PDAP-RGO based sensor were
15 recorded at –0.45 V in 0.1 M PBS (pH 7.0) under stirring at
room temperature.
Fig. 2 SEM images of PDAP-GCE (A) and PDAP-RGO (B).
Fig. 3A shows the FT-IR of GO and PDAP-RGO. For GO, the
65 peaks at 3435, 1737, 1220 and 1058 cm-1 are associated with the
oxygen-containing groups including –OH, C=O and C–O.21
These characteristic peaks disappear completely at the PDAP-
RGO due to the electrochemical reduction of GO to RGO, and
several new peaks at 3330, 3195 and 1421 cm-1 corresponding to
70 the stretching vibrations of –NH2 and C–N are observed, which
are originated from PDAP. Fig. 3B shows the Raman spectra of
GO and PDAP-RGO. It can be seen that the Raman spectra of
GO and PDAP-RGO exhibit two prominent peaks of D and G
bands at 1349 and 1587 cm-1, respectively. Generally, the
75 intensity ratio of D band to G band (ID/IG) is used to estimate the
disorder of G.22 The intensity ratio of PDAP-RGO (1.16) is
higher than that of GO (1.02), suggesting that GO is reduced to
RGO after the electrochemical treatment.
Results and discussion
Catalytic polymerization of 2,6-diaminopyridine on RGO
The cyclic voltammograms of the electrochemical polymerization
20 of 2,6-diaminopyridine at bare GCE and RGO modified GCE are
shown in Fig. 1. At the bare GCE, an irreversible and broad
oxidation peak appears at 0.60 V on the first cycle (Fig. 1A),
which is due to the monomer polymerization.5 It is amazing that
two irreversible oxidation peaks with remarkably increased
25 current appear at the RGO modified GCE on the first cycle (Fig.
1B). The peak at 0.45 V is indicative of the formation of radical
cations; and the peak at 0.78 V is attributed to the oxidation of
monomers. It is clear that RGO plays a significant role in the
electrocatalytic synthesis of PDAP. The catalytic effect of RGO
30 may be ascribed to the delocalized π-electrons of G,19 which lead
to the formation of strong π-stacking interactions between RGO
and aromatic compounds and their derivatives.20 The peak
currents decrease significantly from the second cycle, suggesting
that PDAP film is formed on the RGO modified GCE. Since
35 PDAP belongs to organic semiconductor, and its electrical
conductivity is much lower than that of RGO. And therefore, the
deposited PDAP on RGO will hinder the further electrodeposition
of PDAP film.
A
B
G
D
GO
GO
PDAP-RGO
PDAP-RGO
4000 3500 3000 2500 2000 1500 1000 500
Wavenumber / cm-1
500
1000
1500
2000
2500
3000
Raman shift / cm-1
140
120
100
80
1400
1200
1000
800
600
400
200
0
90 Fig. 3 FT-IR spectra (A) and Raman spectra (B) of GO and PDAP-RGO.
Fig. 4A shows the cyclic voltammograms of RGO and PDAP-
RGO in 0.1 M PBS (pH 7.0). A pair of broad redox peaks (–0.03
and –0.26 V) appears at the RGO, which may be attributed to the
subtle incomplete electrochemical reduction of oxygen groups. It
95 is interesting to find that at the PDAP-RGO, the redox peaks
appear at nearly identical potentials to those at the RGO,
meanwhile the peak currents increase a little. To clarify the
contributions of PDAP, an additional cyclic voltammogram of
PDAP-GCE is recorded in the same electrolyte (Fig. 4B). A pair
100 of weak redox peaks is observed at –0.02 and –0.15 V, which is
caused by the oxidation and reduction of the PDAP film. Because
the peak potentials of PDAP are very close to those of RGO,
there is only one pair of broad redox peaks appearing at the
PDAP-RGO. It is noted that the oxidation peak current of PDAP-
105 RGO (80 μA) is greatly increased compared with that of PDAP-
GCE (4 μA), implying the strong electrocatalytic effect of RGO
A
B
a
b
c
60
a
40
b
c
20
0
-200
-20
-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
-0.2 0.0 0.2 0.4 0.6 0.8 1.0 1.2 1.4 1.6
E vs. SCE / V
E vs. SCE / V
50 Fig. 1 Cyclic voltammograms of electrochemical polymerization of 2,6-
diaminopyridine on bare GCE (A) and RGO modified GCE (B) in 0.1 M
NaOH containing 0.1 M NaH2PO4 and 20 mM 2,6-diaminopyridine. (a)
first cycle; (b) second cycle; and (c) third cycle.
55
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RSC Advances
for the growth of PDAP film.
acidity in the vicinity of the PDAP-RGO electrode and improve
View Article Online
the pH dependence of the PDAP film deposited on RGO.25-27
150
100
50
9
6
DOI: 10.1039/C5RA07345F
A
B
100
90
80
70
60
50
40
30
20
150
100
50
PDAP-GCE
PDAP-RGO
RGO
0.3
B
A
a
b
3
0.2
c
0
0.1
d
e
-3
-6
-9
-12
0.0
0
0
-0.1
-0.2
-0.3
-0.4
-0.5
-50
-100
-50
-100
-150
-0.9
-0.6
-0.3
0.0
0.3
0.6
0.9
-0.9
-0.6
-0.3
0.0
0.3
0.6
0.9
E vs. SCE / V
2
3
4
5
6
7
9
10 11 12
pH 8
-0.9
-0.6
-0.3
0.0
0.3
0.6
0.9
E vs. SCE / V
E vs. SCE / V
75
Fig. 4 (A) Cyclic voltammograms of RGO and PDAP-RGO. (B) Cyclic
voltammogram of PDAP-GCE. Electrolyte: 0.1 M PBS of pH 7.0. Scan
rate: 50 mV s-1.
Fig. 6 (A) Cyclic voltammograms of PDAP-RGO in 0.1 M PBS of
various pH values at a scan rate of 50 mV s-1: (a) 3.0; (b) 5.0; (c) 7.0; (d)
9.0 and (e) 11.0. (B) Dependencies of anodic peak current and anodic
peak potential on pH.
15 Electrode process and pH dependence of PDAP-RGO
Fig. 5A shows the effect of scan rate (υ) on the cyclic
80 Electrocatalytic reduction of H2O2 at PDAP-RGO
voltammograms of PDAP-RGO. It is evident that both the anodic
and the cathodic peak current of PDAP-RGO increase with
increasing scan rate from 25 to 250 mV s-1. The linear
20 relationship between the anodic peak current and the scan rate is
shown in Fig. 5B, suggesting that the electrode process of PDAP-
RGO is surface-controlled. It is found that the straight line
deviates slightly from the origin, showing that the electrode
process of PDAP-RGO is not an ideal behaviour, which may be
25 attributed to the undesired double-layer charging phenomena.23,24
Fig. 7A shows the cyclic voltammograms of H2O2 of three
different concentrations (0, 12.5 and 25 mM) at the PDAP-RGO
electrode. It is obvious that the peak at –0.64 V is attributed to the
reduction of H2O2, since it increases significantly with increasing
85 H2O2 concentration. However, it is interesting to find that at
individual PDAP (Fig. 7B) and RGO electrode (Fig. 7C), no
reduction peak for H2O2 is observed.
90
A
400
200
0
350
f
A
300
200
100
0
B
e
d
c
300
250
200
150
100
50
a
b
a
-200
-400
-600
-800
b
-100
-200
-300
100
c
-0.9
-0.6
-0.3
0.0
0.3
0.6
0.9
0
50
100
150
200
250
-0.9
-0.6
-0.3
0.0
0.3
0.6
0.9
Scan rate / mv s-1
E vs. SCE / V
E vs. SCE / V
a
b
100
C
B
15
10
5
b
Fig. 5 (A) Cyclic voltammograms of PDAP-RGO in 0.1 M PBS of pH 7.0
at different scan rates: (a) 25; (b) 50; (c)100; (d) 150; (e) 200 and (f) 250
40 mV s-1. (B) Linear relationship between anodic peak current and scan rate.
The cyclic voltammograms of PDAP-RGO in 0.1 M PBS of
various pH values are shown in Fig. 6A. As can be seen, the
anodic peak current decreases significantly with increasing pH
value from pH 3.0 to pH 11.0, accompanied by an obvious shift
45 of the anodic peak potential towards the negative direction (Fig.
6B). This phenomenon implies that protons participate in the
redox of PDAP. In other words, protons are de-doped from PDAP
film to the electrolyte during the oxidation process, and vice
versa during the reduction process. It should be emphasized that
50 although the redox activity of PDAP-RGO decreases with
increasing pH values, there is still a pair of broad redox peaks at
pH 11.0, suggesting that PDAP-RGO still remains good
electroactivity till such high pH value. Usually, PDAP loses its
electroactivity completely at pH higher than 6.0.2 In this work,
55 the significantly improved pH dependence of the PDAP-RGO
must be attributed to the introduction of RGO. On one hand, the
delocalized π-structure of RGO can facilitate the electron transfer
at the electrode-solution interface; on the other hand, the subtle
residual oxygen-containing functionalities on RGO during the
60 electrochemical reduction of GO, such as –OH and –COOH, can
be oxidized and reduced reversibly, and thus they can adjust the
50
0
a
0
-5
-50
-10
-15
-0.9
-0.6
-0.3
0.0
0.3
0.6
0.9
-0.9
-0.6
-0.3
0.0
0.3
0.6
0.9
E vs. SCE / V
E vs. SCE / V
105
Fig. 7 Cyclic voltammograms of 0 (a), 12.5 (b) and 25 (c) mM H2O2 at
PDAP-RGO (A), individual PDAP (B) and RGO (C) electrode in 0.1 M
N2-saturated PBS of pH 7.0.
Obviously, the electrocatalytic reduction of H2O2 at the PDAP-
110 RGO electrode is caused by the synergistic effect of RGO and
PDAP. On one hand, the unique structure of RGO (large
delocalized π-electron system) is beneficial to the electron
transfer at the electrode-solution interface; on the other hand,
there is a large amount of amino and imino groups in PDAP, and
115 these redox-active amino and imino groups in PDAP can function
as redox mediators during the electrochemical reduction of H2O2,
which is similar to the previous reports using Azure A28 or
Prussian blue29 as the redox mediators. As a result, the synergistic
effect of RGO and PDAP leads to the obvious electrocatalytic
120 reduction of H2O2 at the PDAP-RGO electrode, as shown in the
following equations:
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Page 4 of 6
6
5
4
3
2
1
0
PDAPoxd-RGO + 2ne- + 2nH+ → PDAPred-RGO
nH2O2 + PDAPred-RGO → 2nH2O + PDAPoxd-RGO (2)
Total reaction: H2O2 + 2e- + 2H+ → 2H2O
(3)
(1)
View Article Online
DOI: 10.1039/C5RA07345F
70
The calibration curve with only H2O2 at the PDAP-RGO
5
electrode is shown in Fig. 8.
100
75
80
60
40
20
0
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
1/[Glucose] / mM-1
15
Fig. 10 Double-reciprocal plot of current versus glucose concentration.
Apparent Michaelis-Menten constant is an important parameter
80 reflecting the enzyme reaction kinetics, which can be estimated
by using Lineweaver-Burk equation.35 According to the double-
reciprocal plot of current versus glucose concentration (Fig. 10),
the apparent Michaelis-Menten constant is calculated to be 24.73
mM, suggesting a high substrate affinity of the immobilized GOD.
0
5
10
15
20
25
[H2O2] / mM
25 Fig.
8 Linear relationship between current response and H2O2
concentration.
85
The performance of the proposed biosensor is compared with
some of the reported glucose biosensors, as shown in Table 1.
The results indicate that the analytical performance of the
developed sensor is comparable to those enzymatic and non-
enzymatic glucose sensors, even superior to most of them.
Glucose sensing based on PDAP-RGO
Glucose sensing based on the PDAP-RGO electrode is achieved
via amperometric detection of H2O2 at a reduction potential,
30 which is resulted from the oxidation of glucose in the presence of
GOD and dissolved oxygen, as shown in the following equations:
90 Table 1 Comparison of the PDAP-RGO based sensor with some
-glucose + GOD + O2 → -gluconic acid + H2O2
(4)
(5)
enzymatic and non-enzymatic glucose sensors
H2O2 + 2e- + 2H+ → 2H2O
Materials
Detection
Linear
Reference
Since the current signals are closely related to H2O2 concentration,
35 glucose can be accurately quantified by measuring the produced
current responses.30 Fig. 9A shows typical chronoamperometric
responses of the GOD immobilized PDAP-RGO electrode to
successive additions of glucose to the stirred air-saturated 0.1 M
PBS of pH 7.0 at a negative potential of –0.45 V. The glucose
40 sensor responds quickly to the additions of glucose and reaches to
the steady-state current within a short time. As shown in Fig. 9B,
the enzyme electrode exhibits a wide linear range for glucose
from 0.05 to 6.65 mM with a correlation coefficient of 0.996. The
linear regression equation can be expressed as: I (μA) = 0.096 +
45 0.477C (mM) (n = 13). The detection limit is calculated to
be 0.142 μM at a signal-to-noise of 3, which is even lower than
the non-enzymatic glucose sensors reported previously by our
group11 and other researchers.31-34
limit (μM) range (mM)
PDAP/RGO
0.142
0.5
0.05-6.55
0.001-0.765
0.965-13.665
0.025-4.9
0.002-10.3
10.3-20.3
0.5-8
This work
11
NiHCF/PANI/G
PdNPs/RGO
PtNFs/GO
0.56
2.0
17
36
GOx/Pt/FCNA
PtNPs/SPE
0.3
9.3
37
38
0.5-3
NiHCF/PANI/G,
cubic
nickel
hexacyanoferrate/polyaniline/G;
PdNPs/RGO, Pd nanoparticles/RGO; PtNFs/GO, Pt nanoflowers/GO;
GOx/Pt/FCNA, glucose oxidase/Pt/flower-like carbon nanosheet
95 aggregation; PtNPs/SPE, Pt nanoparticles/screen printed electrode.
3.5
3.0
2.5
2.0
1.5
1.0
0.5
0.0
0
-1
-2
-3
-4
-5
B
A
0.25 mM
Specificity of the detection system
0.05 mM
0.5 mM
Ascorbic acid (AA) and uric acid (UA) are two common
interferents in the detection of glucose. Fig. 11 shows the
amperometric responses to successive additions of 5 mM glucose,
100 0.1 mM AA and 0.3 mM UA recorded at the PDAP-RGO based
sensor at –0.45 V in 0.1 M PBS of pH 7.0. It is shown that
proposed sensor exhibits excellent selectivity to glucose in the
presence of AA and UA.
1 mM
0
250
500
750
t / s 1000
1250
1500
0
1
2
3
4
5
6
7
[Glucose] / mM
Fig. 9 (A) Chronoamperometric responses of the GOD immobilized
60 PDAP-RGO electrode towards various concentrations of glucose in
stirred air-saturated 0.1 M PBS (pH 7.0) at a negative potential of –0.45 V.
(B) Linear relationship between current response and glucose
concentration.
105
65
110
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RSC Advances
electrochemical reduction of H2O2 due to the synergistic effect of
1
0
RGO and PDAP, and thus a sensitive glucose sensinVgiepwlaAtrtfioclremOnilsine
Glucose
DOI: 10.1039/C5RA07345F
constructed via immobilizing GOD to the PDAP-RGO electrode.
The prepared glucose sensor displays excellent performances for
65 glucose sensing, opening a new avenue for the construction of
biocatalysis and biosensing platform via combining the
advantages of conducting polymers and RGO based carbon
nanomaterials.
-1
-2
-3
-4
10
AA
UA
0
100 200 300 400 500 600 700
t / s
Acknowledgments
20
70 The authors are grateful to the National Natural Science
Foundation of China (21275023, 21173183), Natural Science
Foundation of Jiangsu Province (BK2012593), Jiangsu Key
Laboratory of Advanced Catalytic Materials and Technology
(BM2012110), Jiangsu Key Laboratory of Fine Petrochemical
Fig. 11 Amperometric responses of the PDAP-RGO based sensor to
successive additions of 5 mM glucose, 0.1 mM AA and 0.3 mM
UA at an applied potential of –0.45 V in 0.1 M PBS (pH 7.0).
25 Reproducibility and stability
The intra- and interassay reproducibility of the PDAP-RGO based 75 Engineering (KF1305) and Priority Academic Program
glucose sensor were tested. The intraassay reproducibility was
examined by continuous determination of 1 mM glucose with the
same GOD immobilized electrode for five times, and the relative
30 standard deviation (RSD) is calculated to be as small as 2.87%.
Meanwhile, the interassay reproducibility was also estimated by
measuring 1 mM glucose with five independent PDAP-RGO
electrodes prepared via the same procedure, and a RSD of 3.28%
is obtained. The small RSDs in intra- and interassay suggest that
35 the GOD immobilized PDAP-RGO electrode has good
Development of Jiangsu Higher Education Institutions (PAPD).
References
aJiangsu Key Laboratory of Advanced Catalytic Materials and
Technology, School of Petrochemical Engineering, Changzhou University,
80 Changzhou 213164, P. R. China
bSchool of Chemistry and Chemical Engineering, Yangzhou University,
Yangzhou 225002, P. R. China
cJiangsu Key Laboratory of Fine Petrochemical Engineering, Changzhou
University, Changzhou 213164, P. R. China
85
preparation and determination reproducibility. In addition, the
stability of the proposed PADP-RGO based glucose sensor was
also assessed. The sensor was stored at 4 °C in 0.1 M PBS of pH
7.0, and the current responses of 1 mM glucose were recorded
40 periodically. It is found that the current signal changes little
during the first week, and it still remains at about 94% of the
initial response after two weeks of storage. The results indicate
that the as-prepared glucose sensor has satisfactory stability.
E-mail: yzkongyong@126.com; chhgxue@yzu.edu.cn
1
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Analysis of real samples
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50 from the proposed sensor are similar to those measured by the
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120
4, 4806.
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