High surface area mesoporous CuO: A high-performance electrocatalyst for non-enzymatic glucose biosensing

Article abstract of DOI:10.1039/c4ra04700a

A highly sensitive and selective non-enzymatic glucose biosensor has been successfully constructed using high surface area mesoporous CuO (108 m ² g^-1) templated by mesoporous carbon. The glucose biosensor exhibits a low detection limit of 0.23 μM at a signal-to-noise ratio of 3. the Partner Organisations 2014.

Full text of DOI:10.1039/c4ra04700a

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High surface area mesoporous CuO: a high-
performance electrocatalyst for non-enzymatic
Cite this: RSC Adv., 2014, 4, 33327
glucose biosensing†
Received 19th May 2014
Accepted 18th July 2014
Sen Liu, Ziying Wang, Fengjiao Wang, Bo Yu and Tong Zhang*
DOI: 10.1039/c4ra04700a
www.rsc.org/advances
A highly sensitive and selective non-enzymatic glucose biosensor has with narrow band gap (1.2–1.9 eV), has been studied intensely
been successfully constructed using high surface area mesoporous for non-enzymatic glucose biosensing because of its good
2
ꢀ1
CuO (108 m
g ) templated by mesoporous carbon. The glucose electrochemical activity, suitable surface charge and easily
biosensor exhibits a low detection limit of 0.23 mM at a signal-to-noise tunable surface structure. Due to the good stability of CuO
ratio of 3.
x
materials than that of GO , CuO-based non-enzymatic glucose
sensors are good candidates for in vitro monitoring of glucose,
which is also another reason for development of CuO-based
electrochemical glucose biosensors. Up to now, numerous non-
enzymatic glucose biosensors based on CuO-based materials
Introduction
The determination of glucose has received considerable atten- have been successfully fabricated. For example, the CuO-based
tion due to its wide applications in the elds of medicine, materials with various morphologies or structures, such as
1
,2
18
19
20
biotechnology, and food industry.
techniques, including electrochemical detection, colorimetric bers, owers and nanorods, and nanotube arrays have
Among the detection nanoparticles, sandwich-structured, nanoowers, nano-
3
21
22
23
4
5
detection, uorescent detection, as well as the Surface- been used for fabrication of non-enzymatic glucose biosensors.
Enhanced Raman Scattering (SERS) method, the electro- Additionally, recent research has shown that sensing perfor-
6
chemical technique is a promising tool for the construction of mances can be improved by using CuO-based hybrids as
2
4,25
simple and low-cost glucose biosensors owing to its unique sensing materials. Indeed, CuO–carbon nanotubes (CNTs),
26
advantages of high sensitivity, good selectivity, and ease of CuO–reduced graphene oxide (rGO), CuO–TiO
hierarchical
2
7,8
27
28
operation. It is well known that the conventional glucose nanocomposites, Pt-doped CuO nanobers, and CuO–mes-
biosensors based on glucose oxidase (GO ) exhibit high sensi- oporous carbon have been successfully used for fabrication of
29
x
tivity and selectivity for glucose detection. However, these non-enzymatic glucose biosensors. However, most of these
methods exhibit some serious disadvantages, such as compli- modied electrodes exhibit more or less drawbacks, such as
cated and multi-step immobilization procedures, thermal and high cost, the use of complicated instruments for preparation of
chemical instability and high cost, limiting their wide applica- nanobers and the rigorous experiment conditions for prepa-
9–11
tions.
biosensors based on noble metals (such as, Pt, Pd, Au) have
To overcome these problems, non-enzymatic glucose ration of CNTs or rGO.
It is well known that surface area of electrocatalysts plays an
been successfully developed. Unfortunately, the high cost of the important role in sensing performances for electrochemical
electrode materials still limits their commercial applications on detection and increasing the surface area of electrocatalysts has
1
2,13
a large scale.
Recently, much effort has been devoted for developing non- chemical sensing properties.
enzymatic glucose biosensors based on low-cost transition ordered mesoporous materials have received much attention
been proven as an effective strategy for enhancing electro-
30,31
Since the rst reported in 1992,
14–17
metal oxides, such as, CuO, NiO, Co
them, CuO, an important p-type metal oxide semiconductor volume as well as uniform mesopores.
3
O
4
, Mn
3
O
4
etc.
Among due to their excellent properties of high surface area, large pore
32,33
However, there are
few reports on development of non-enzymatic glucose biosen-
sors using mesoporous CuO with high surface area as sensing
State Key Laboratory on Integrated Optoelectronics, College of Electronic Science and
Engineering, Jilin University, Changchun 130012, P. R. China. E-mail: zhangtong@jlu. materials.
edu.cn; Fax: +86 431 85168270; Tel: +86 431 85168385
34
In this work, a novel non-enzymatic glucose biosensor has
been successfully developed using high surface area
†
Electronic supplementary information (ESI) available. See DOI:
0.1039/c4ra04700a
1
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2
ꢀ1
mesoporous CuO (108 m
g
) as sensing materials. Most and desorption isothermal of mesoporous CuO. It is seen that
importantly, mesoporous CuO exhibits good sensing perfor- mesoporous CuO exhibits a typical IV-type isotherm with a
mances including high sensitivity and high selectivity, which sharp capillary condensation step at medium relative pressures
are attributed to its high surface area and open mesopores.
and a H1 hysteresis loop, suggesting the existence of meso-
pores, which is in good agreement with ordered mesoporous
CuO. Fig. 1d shows pore size distribution curve of mesoporous
CuO, indicating that the mesoporous CuO has a uniform pore
38
Results and discussion
It is well known that CuO can be dissolved in NaOH solution or structure and narrow pore size distribution around 5.1 nm,
HF solution, and thus no mesoporous CuO was obtained by which also provides another piece of evidence to support the
conventional nanocasting method using SBA-15 as hard formation of the mesoporous structure. The BET surface area
2
ꢀ1
template. In the present work, mesoporous CuO was prepared and pore volume of mesoporous CuO are 108 m g and 0.16
3
ꢀ1
using ordered mesoporous carbon CMK-3 as hard template, cm g , respectively, further conrming the formation of the
where three synthesis steps were carried out. Firstly, SBA-15 was mesoporous structure. All these observations indicate that
prepared using Pluronic P123 (EO20PO70EO20, M ¼ 5800) as so mesoporous CuO has been successfully prepared by nano-
35
template and tetraethyl orthosilicate (TEOS) as silica source.
Fig. S1† shows the small-angle X-ray diffraction (XRD) pattern of
casting method using CMK-3 as hard template.
It should be noted that the surface area of mesoporous CuO
SBA-15 aer calcination. It is seen that the sample exhibits three in this work is higher than that of previously reported CuO
well resolved diffraction peaks, which are indexed as (1 0 0), (1 1 materials, such as, hierarchical hollow mesoporous CuO
2
ꢀ1 40
0
) and (2 0 0) diffractions associated with p6mm hexagonal microspheres (51 m g ), CuO mesoporous nanosheet cluster
36
2
ꢀ1 41
symmetry, indicating the successful preparation of SBA-15.
array (35.82 m g ), and mesoporous CuO microspheres
2
ꢀ1 42
Secondly, CMK-3 was prepared by using SBA-15 as hard (65.28 m g ). The presence of mesoporous structure with
template and sucrose as carbon source. Fig. S2† shows small- high surface area could enhance the interaction between the
37
ꢁ
angle XRD pattern of CMK-3 aer calcination in N
2
at 900 C for CuO and glucose molecules, possible improving the sensing
4
h, which exhibits a strong diffraction peak, indicating the performances for glucose detection.
successful preparation of mesoporous carbon materials.
The morphology of the mesoporous CuO was characterized
Thirdly, mesoporous CuO was prepared by the nanocasting by scanning electron microscopy (SEM). Fig. S3† shows the SEM
38
method using CMK-3 as hard template. Fig. 1a show the small- images of mesoporous CuO, revealing the samples are aggre-
angle XRD pattern of samples thus obtained, revealing a well gates with the size about several micrometers, which are con-
ꢁ
resolved diffraction peak at 2q of 1.23 , which indicates the sisting of nanorods with the size of 300–500 nm. The
formation of mesoporous structure. Fig. 1b shows the wide- corresponding high magnication SEM (Fig. S3b†) exhibits
angle XRD pattern of the mesoporous materials. It is seen that these nanorods are also consisting of the nanoparticles below
the samples exhibit several diffraction peaks attributed to 100 nm.
39
monoclinic symmetry of CuO (JCPDS Card no. 48-1548). Note
To demonstrate the electrochemical application of meso-
that no other peaks attributed to metal Cu, Cu(OH) or Cu O are porous CuO, non-enzymatic glucose biosensors were con-
2
2
observed, indicating the formation of pure phase of CuO.
The formation of mesoporous CuO materials was further CuO on the surface of GCE. The sensing performances of both
conrmed by N isothermal. Fig. 1c shows the N adsorption
structed by dropping the aqueous dispersion of mesoporous
2
2
Fig. 1 (a) Small-angle XRD pattern, (b) wide-angle XRD pattern, (c) N
2
Fig. 2 Cyclic voltammograms (CVs) of bare GCE and CuO/GCE in the
adsorption–desorption isothermal and (d) pore size distribution curve absence and in the presence of 2 mM glucose in 0.1 M NaOH (scan
ꢀ
1
of mesoporous CuO thus obtained.
rate: 0.05 V s ).
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bare GCE and mesoporous CuO modied GCE (designated as
Fig. 4 shows the typical amperometric response curve of
CuO/GCE) toward the oxidation of glucose were examined by CuO/GCE in 0.1 M NaOH solution on successive step-wise
cyclic voltammetry (CV). Fig. 2 shows the CVs of bare GCE and change of glucose concentrations at the applied potential of
CuO/GCE in the absence and presence of 2 mM glucose in 0.1 M +0.6 V. The inset of Fig. 4 shows the response curve of CuO/GCE
NaOH. It is seen that bare GCE exhibits no obvious response toward low concentrations of glucose ranging from 0.5 mM to
both in the absence and presence of glucose, indicating that 100 mM. Additionally, the amperometric response curves of
bare GCE exhibits no electrocatalytic activity toward electro- CuO/GCE to various concentrations of glucose were also
chemical oxidation of glucose. In contrast, CuO/GCE exhibits a examined with applied potential of +0.5 V and +0.7 V, respec-
broad reduction peak at +0.56 V in the alkaline solution, which tively, as shown in Fig. S4a and b.† It should be noted that an
43
is attributed to a Cu(II)/Cu(III) redox couple. However, the obvious response was observed at CuO/GCE by addition of
corresponding oxidation peak of Cu(II)/Cu(III) redox couple is 0.5 mM glucose, indicating the high sensitivity of this glucose
not clearly observed, which may be overlaid by the oxidation biosensor. When an aliquot of glucose was added into the
24
peak of water-splitting. Upon addition of 2 mM glucose, CuO/ NaOH solution with stirring, CuO/GCE responded rapidly to the
GCE exhibits an obvious oxidation peak attributed to irrevers- substrate and the current rose steeply to reach a stable value.
ible oxidation of glucose at +0.60 V, indicating that mesoporous
CuO can catalyze oxidation of glucose. Fig. 3 shows the sche-
matic of modied electrode structure and the reaction pathway
during the non-enzymatic electrochemical oxidation of glucose
on the surface of the CuO/GCE in an alkaline medium. All these
observations indicate that mesoporous CuO exhibits electro-
catalytic ability toward oxidation of glucose and can be used for
fabrication of non-enzymatic glucose biosensor.
Fig. 3 Schematic of modified electrode structure and the reaction Fig. 5 The calibration curve for the amperometric response of the
pathway during the non-enzymatic electrochemical oxidation of CuO/GCE. The insets were the calibration curve with the glucose
glucose on the surface of the CuO/GCE in 0.1 M NaOH.
concentration increasing from 0.5 mM to 5 mM and 10 mM to 100 mM,
respectively (applied potential: +0.6 V).
Fig. 4 Typical steady-state response of the CuO/GCE to successive
injection of glucose into the 0.1 M NaOH solution under stirring. The Fig. 6 Interference test of CuO/GCE at +0.6 V in 0.1 M NaOH with 1
inset was the response of the CuO/GCE toward the concentration of mM glucose in the presence of 0.1 mM AA, 0.1 mM UA, and 10 mM
glucose ranging from 0.5 mM to 100 mM (applied potential: +0.6 V).
ethanol.
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Table 1 Comparison of analytical performance of our proposed glucose sensor with other published non-enzymatic glucose sensors based on
CuO materials
Performances
Materials
LOD
Linear range
Ref.
CuO nanoparticles
Sandwich-structured CuO
CuO nanobers
CuO owers and nanorods
CuO-loaded SBA-15
Mesoporous CuO
0.5 mM
1.0 mM
0.8 mM
4 mM
10 mM
0.23 mM
5 mM to 2.3 mM
20 mM to 3.2 mM
6 mM to 2.5 mM
4 mM to 8 mM
50 mM to 20 mM
0.5 mM to 5 mM; 10 mM to 100 mM
18
19
21
22
44
This work
The anode current of the sensor increased dramatically and response current at the CuO/GCE decreases to about 94% of its
th
achieved 95% of the steady state current within 2 s, revealing a initial response current on the 5 day, indicating the good
fast amperometric response behavior. In contrast, the sensors stability of the glucose sensors thus obtained.
exhibit no obvious response to low concentration of glucose
with the applied potential of +0.5 V and +0.7 V. Thus, the
optimized applied potential for amperometric response curve is
Conclusion
+0.6 V.
A novel non-enzymatic glucose biosensor has been successfully
Fig. 5 shows the calibration curve of the sensor for increasing fabricated using mesoporous CuO as sensing materials, which
the concentrations of glucose from 0.5 mM to 3.6 mM. The were prepared by the nanocasting method using CMK-3 as
intensity of response toward the oxidation of glucose increased template. Our present study is important because it provides a
with increasing the concentrations of glucose, indicating that novel method for non-enzymatic detection of glucose by using
the glucose biosensor thus constructed can be used for detec- mesoporous metal oxides as sensing materials, which also
tion of glucose at a wide concentration range. The insets in suggests the potential applications of the mesoporous CuO for
Fig. 5 show the calibration curves for the low concentrations of constructing efficient biosensing.
glucose, revealing that the biosensor exhibits good linear
detection ranging from 0.5 mM to 5 mM (r ¼ 0.998) and 10 mM to
Acknowledgements
100 mM (r ¼ 0.999), respectively. The detection limit is estimated
to be 0.23 mM at a signal-to-noise ratio of 3. It should be noted This research work was nancially supported by the National
that our present sensing system gives a lower detection limit Natural Science Foundation of China (Grant no. 51202085).
than those of the biosensors for detection of glucose, such as
18
CuO nanoparticles (0.5 mM), sandwich-structured CuO (1.0
Notes and references
1
9
21
mM), CuO nanobers (0.8 mM), CuO owers and nanorods (4
22
44
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our glucose sensor is also compared with those previously
published non-enzymatic glucose sensors based on CuO mate-
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