Platinum nanoparticle-decorated carbon nanotube clusters on screen-printed gold nanofilm electrode for enhanced electrocatalytic reduction of hydrogen peroxide

Article abstract of DOI:10.1016/j.electacta.2012.01.030

In the present study the electrocatalytic behavior of platinum nanoparticle-decorated multi-walled carbon nanotube clusters vertically aligned on a screen-printed gold nanofilm electrode substrate (SPGFE/MWCNTC/PtNP) toward hydrogen peroxide was intensively investigated. Oriented multi-walled carbon nanotube clusters (MWCNTC) were firstly well-organized onto the screen-printed gold film electrode (SPGFE) surface by covalent immobilization, and then platinum nanoparticles (PtNPs) dispersed on the MWCNTC structure were in situ synthesized by electrochemically reducing chloroplatinic acid. It was demonstrated that the MWCNTC/PtNP hybrid structure on the SPGFE substrate could significantly enhance the electrochemical reduction of hydrogen peroxide in neutral solutions. Compared with platinum nanoparticles loading on disordered multi-walled carbon nanotubes (SPGFE/MWCNT/PtNP), the proposed SPGFE/MWCNTC/PtNP exhibited more sensitive responses for hydrogen peroxide reduction. The fabricated electrode provided linear current responses for hydrogen peroxide in the concentration range from 5 to 2000 μM with a detection limit of 1.23 μM. The non-enzymatic sensor also offered good reproducibility and high selectivity for hydrogen peroxide detection. The carbon nanotube cluster/platinum nanoparticle hybrid system holds great promise as a scaffold to fabricate enzyme biosensors.

Full text of DOI:10.1016/j.electacta.2012.01.030

Electrochimica Acta 65 (2012) 97–103
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Electrochimica Acta
journal homepage: www.elsevier.com/locate/electacta
Platinum nanoparticle-decorated carbon nanotube clusters on screen-printed
gold nanofilm electrode for enhanced electrocatalytic reduction of hydrogen
peroxide
Xiangheng Niua, Hongli Zhaoa, Chen Chena, Minbo Lana,b,∗
a Shanghai Key Laboratory of Functional Materials Chemistry, and Research Centre of Analysis and Test, East China University of Science and Technology, Shanghai 200237, PR China
b State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai 200237, PR China
a r t i c l e i n f o
a b s t r a c t
Article history:
In the present study the electrocatalytic behavior of platinum nanoparticle-decorated multi-walled
carbon nanotube clusters vertically aligned on a screen-printed gold nanofilm electrode substrate
(SPGFE/MWCNTC/PtNP) toward hydrogen peroxide was intensively investigated. Oriented multi-walled
carbon nanotube clusters (MWCNTC) were firstly well-organized onto the screen-printed gold film elec-
trode (SPGFE) surface by covalent immobilization, and then platinum nanoparticles (PtNPs) dispersed
on the MWCNTC structure were in situ synthesized by electrochemically reducing chloroplatinic acid. It
was demonstrated that the MWCNTC/PtNP hybrid structure on the SPGFE substrate could significantly
enhance the electrochemical reduction of hydrogen peroxide in neutral solutions. Compared with plat-
inum nanoparticles loading on disordered multi-walled carbon nanotubes (SPGFE/MWCNT/PtNP), the
proposed SPGFE/MWCNTC/PtNP exhibited more sensitive responses for hydrogen peroxide reduction.
The fabricated electrode provided linear current responses for hydrogen peroxide in the concentration
range from 5 to 2000 ␮M with a detection limit of 1.23 ␮M. The non-enzymatic sensor also offered
good reproducibility and high selectivity for hydrogen peroxide detection. The carbon nanotube clus-
ter/platinum nanoparticle hybrid system holds great promise as a scaffold to fabricate enzyme biosensors.
Received 4 November 2011
Received in revised form 4 January 2012
Accepted 6 January 2012
Available online 15 January 2012
Keywords:
Platinum nanoparticle
Multi-walled carbon nanotube cluster
Screen-printed gold nanofilm electrode
Electrocatalytic reduction
Hydrogen peroxide
© 2012 Elsevier Ltd. All rights reserved.
1. Introduction
reducing the active sites exposed. Hence, an interesting question
is how to fabricate tailored architectures with CNTs and further
Since the early 1990s, carbon nanotubes (CNTs) have always
been attracting growing attention because of their unique proper-
ties such as one-dimensional nature, high conductivity, structural
robustness and large specific surface area. These properties con-
tribute to CNTs gaining extensive applications in the development
of novel sensors [1,2]. Especially due to the remarkable electro-
catalytic property and excellent electrical conductivity, CNTs are
commonly applied to directly electrocatalyze interesting analytes
including hydrogen [3], methanol [4,5], hydrogen peroxide [6–8],
nitrite [9], phenols and vitamin B [10,11]. Most of these studies,
however, modify the electrode substrates by simply drop-casting
and immobilizing CNTs with physical adsorption, resulting in a
random and chaotic arrangement of nanotubes and dramatically
improve their properties such as catalytic ability, electron trans-
fer quality and mechanical stability. Since Smalley and coworkers
[12] linked the acid-treated CNTs to alkanethiol by the amide link-
age and then tethered the free thiol end to gold particles by the
Au S bond, this novel self-assembly method has been regarded
as an efficient route to immobilize CNTs. Self-assembly can make
CNTs well-organized on the electrode surface and provide more
electron communication tunnels [13], and make electron transfer
easier due to the high conductance of the edge plane of CNTs [1].
Furthermore, aligned CNTs are proven capable of facilitating the
direct electron transfer between the redox-active enzymes and the
electrode surface [14–16].
Meanwhile, tailored metal nanostructures have also been
widely applied to fabricate novel sensors and devices due to
their unique electronic, optical and catalytic properties [17]. As an
excellent electrode material, nanostructured platinum is of partic-
ular interest for the development of electrochemical sensors and
biosensors owing to its electrochemical stability and prominent
catalytic activity [18]. There are many reports involved in utilizing
platinum nanostructure-decorated carbon nanotubes randomly
∗
Corresponding author at: Shanghai Key Laboratory of Functional Materials
Chemistry, and Research Centre of Analysis and Test, East China University of Sci-
ence and Technology, Shanghai 200237, PR China. Tel.: +86 21 64253574;
fax: +86 21 64252947.
E-mail address: minbolan@ecust.edu.cn (M. Lan).
0013-4686/$ – see front matter © 2012 Elsevier Ltd. All rights reserved.
doi:10.1016/j.electacta.2012.01.030

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X. Niu et al. / Electrochimica Acta 65 (2012) 97–103
Scheme 1. Illustration of the fabrication of SPGFE/MWCNTC/PtNP.
adsorbed on the electrode surface to electrocatalyze interesting
materials for sensing and fuel cell [19–23], while these chaotic
structures reveal a number of disadvantages. The electron commu-
nication, for example, is partially restricted because of the limited
transfer tunnels. More seriously, the adsorbed CNTs are easily exfo-
liated from the substrate, dramatically weakening their reliability,
long-term stability and wider applications in practical sensing.
Therefore, increasing attention has being focused on the highly
ordered carbon nanotube/nanostructured material hybrid archi-
tectures and their applications in electrochemical sensing and fuel
cell [24–27].
Here we introduce a multi-walled carbon nanotube clus-
ter/platinum nanoparticle hybrid structure on a screen-printed
gold nanofilm electrode (SPGFE/MWCNTC/PtNP) substrate for
the electrocatalysis and determination of hydrogen peroxide.
Covalent-linked multi-walled carbon nanotubes were vertically
aligned on the screen-printed gold nanofilm electrode (SPGFE) sur-
face and further formed carbon nanotube clusters (MWCNTC). Then
platinum nanoparticles (PtNPs) were in situ synthesized by electro-
chemically reducing chloroplatinic acid with a cyclic voltammetric
deposition on the MWCNTC structure. The electrocatalytic behavior
of SPGFE/MWCNTC/PtNP toward hydrogen peroxide was inten-
sively discussed. Several parameters affecting the electroanalytical
performances of the proposed electrode were further optimized,
and the sensitivity, reproducibility and selectivity of the fabricated
non-enzymatic sensor for hydrogen peroxide detection were also
evaluated.
2. Experimental
2.1. Materials and chemicals
Multi-walled carbon nanotubes (MWCNTs) with a mean diam-
eter of 15 nm and a mean tube length of 1.5 ␮m were provided
by Shenzhen Nanotech Port Co. ␤-Mercaptoethylamine (MEA)
and dicyclohexyl carbodiimide (DCC) were commercially available
from Aladdin Chemistry Co. Hexachloroplatinic(IV) acid hexahy-
drate (H2PtCl6·6H2O, Sigma–Aldrich Co.) was diluted to 2 wt% as the
platinic precursor. Hydrogen peroxide (H2O2, Sinopharm Chemical
Reagent Co.) was stored under 4 ◦C and diluted before use. 0.1 M
phosphate buffer solution (PBS, pH 6.9) prepared with K2HPO4 and
KH2PO4 was used as the supporting electrolyte. All other reagents
were of analytical grade and used without further purification.
Ultra-pure water (18.2 Mꢀ cm) prepared by a laboratory water
purification system (Shanghai Hitech Instruments Co.) was utilized
in all preparations.
2.2. Preparation of SPGFE
The procedure employed in the preparation of the SPGFE sub-
strate has been described in our previous reports [28,29]. A gold
thin film with a thickness of 75 5 nm determined by atomic
force microscope was obtained using the vacuum sputtering tech-
nique, with an evaporation time of 300 s and an excitation current
of 40 mA, on a JEC-1600 fine vacuum evaporation instrument.

X. Niu et al. / Electrochimica Acta 65 (2012) 97–103
99
The diameter of the gold working area was determined to be
2.5. Apparatus and measurements
4 mm.
All electrochemical experiments were carried out on a CHI 440A
electrochemical station (CHI Instruments Inc.) with a conventional
three-electrode configuration including a fabricated working elec-
trode, a platinum wire counter electrode and a saturated Ag/AgCl
reference electrode. All potentials in the present research were
referred to the saturated Ag/AgCl electrode unless otherwise stated.
The prepared SPGFE/MWCNTC/PtNP was well characterized
by several physical and chemical techniques. The atomic force
microscopy (AFM) image was obtained with atomic force micro-
scope (Nanoscope III Multimode, Veeco, USA). The surface
morphology of electrodes was observed by field emission scan-
ning electron microscope (S-4800 FESEM, Hitachi, Japan). The
immobilization process of MWCNTC on the SPGFE substrate was
also supported by cyclic voltammetric scanning from −0.5 to
+0.5 V in 0.1 M PBS solutions. The electrocatalytic behavior of
SPGFE/MWCNTC/PtNP toward H2O2 was intensively evaluated
with the cyclic voltammetric and chronoamperometric tech-
niques. All measurements were performed at room temperature
(25 2 ◦C).
2.3. Immobilization of MWCNTC
Prior to immobilizing nanotubes onto the SPGFE mirror-like
surface, MWCNTs were shortened and carboxyl functionalized
using a similar procedure as described in [12,14,30]. Briefly, puri-
fied MWCNTs in a mixture (3:1, v/v) of H2SO4 (98%) and HNO3
(70%) were treated with ultrasonic stimulation for 4 h, and then
rinsed with adequate ultrapure water and dried overnight in the
oven at 50 ◦C. Afterwards, 1 mg of treated MWCNTs was well dis-
persed in 5 mL of ultrapure water with 2.5 mg of DCC to convert
the carboxyl group at the ends of nanotubes into active carbodi-
imide esters [30]. Meanwhile, the SPGFE substrate was modified
with an oriented MEA monolayer by incubating the clean SPGFE
into a solution containing 1 mM MEA for 6 h. Finally, the MEA
monolayer-modified electrode was incubated in the carbon nan-
otube solution for 8 h at room temperature, while the free amine
at the terminal of MEA formed the amide bond with one end of the
acid-treated MWCNTs. Scheme 1 illustrates the self-assembly steps
of MWCNTs on the SPGFE substrate to prepare carbon nanotube
clusters.
3. Results and discussion
3.1. Characterization of SPGFE/MWCNTC/PtNP
2.4. Decoration of MWCNTC with PtNPs
In the present research, we introduced a new carbon nanotube
cluster/noble metal hybrid nanostructure on the SPGFE substrate to
electrocatalyze hydrogen peroxide. Several techniques were used
to characterize the morphology and elemental component of the
proposed structure. The AFM image of gold nanofilm electrodes
(not shown) reveals that the as-prepared SPGFE has a flat and
clean surface. Fig. 1(A) depicts the AFM image of MWCNTC on the
The modification of PtNPs onto the MWCNTC structure was
in situ obtained by electrochemically reducing H2PtCl6. Briefly, the
cyclic voltammetric (CV) technique with a potential window from
+0.3 to +1.3 V was employed to prepare PtNPs in a chloroplatinic
acid bath, followed by a cyclic scan procedure from −0.3 to +1.0 V
in 0.5 M H2SO4 to a steady state [31,32].
Fig. 1. AFM image of MWCNTC on the SPGFE surface (A), and SEM images of PtNPs on the SPGFE (B) and SPGFE/MWCNTC (C) surfaces.

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X. Niu et al. / Electrochimica Acta 65 (2012) 97–103
Fig. 2. Cyclic voltammograms of the bare SPGFE, SPGFE/MWCNTC and
SPGFE/MWCNTC/PtNP in 0.1 M PBS solutions (pH 6.9) at a scan rate of 100 mV/s
with the potential window from −0.5 to +0.5 V.
SPGFE substrate. It is found that carbon nanotubes are vertically
aligned on the electrode surface as expected, which is also demon-
strated by Fig. S1 (Supporting Information). The height of carbon
nanotubes is determined to be tens of nanometers, having a good
agreement with previous reports [15,33]. The width of MWCNTC
turns to be much larger than the diameter of a single MWCNT
due to the aggregation of carbon nanotubes in the immobilization
step [15]. Fig. 1(B) and (C) present the SEM patterns of PtNPs on
the bare SPGFE and SPGFE/MWCNTC, respectively. As can be seen,
PtNPs with a diameter of several nanometers are well dispersed
on the SPGFE surface. When MWCNTC are formed on the SPGFE
substrate, PtNPs are partially dispersed across the carbon nano-
tubes (Fig. 1(C)). This phenomenon may be explained as that the
top ends and defects exposed can act as nucleus for the formation
of platinum nanoparticles. It should be stated that there are also
a few carbon nanotubes recumbently on the SPGFE surface. This
phenomenon mainly results from that some carbon nanotubes are
inevitably fixed by physical adsorption during the self-assembly
process and cannot be completely rinsed off.
Fig. 3. (A) Cyclic voltammograms of the bare SPGFE and SPGFE/MWCNTC/PtNP in
0.1 M PBS solutions (pH 6.9) with the absence and presence of 10 mM H2O2 at a
scan rate of 100 mV/s, and (B) typical amperometric responses of the bare SPGFE,
SPGFE/MWCNTC, SPGFE/PtNP, SPGFE/MWCNT/PtNP and SPGFE/MWCNTC/PtNP for
different concentrations of H2O2 in 0.1 M PBS solutions (pH 6.9) with an applied
potential of −0.4 V under a constant stir.
The self-assembly of CNTs on the SPGFE substrate and the
electrodeposition preparation of platinum nanoparticles were also
characterized by electrochemical techniques. Fig. 2 shows the typ-
ical cyclic voltammograms of the bare SPGFE, SPGFE/MWCNTC
and SPGFE/MWCNTC/PtNP in 0.1 M PBS solutions at a scan rate
of 100 mV/s. As we can see, the bare SPGFE exhibits no notable
response in the potential window from −0.5 to +0.5 V. When MWC-
NTs are immobilized on the SPGFE substrate by self-assembly and
form nanotube cluster structures, a pair of weak but recogniz-
able redox peaks are observed at around +0.15 V, which should
be assigned to the carboxylate in non-oriented carbon nanotubes
[15,34]. After the electrochemical deposition procedure, PtNPs are
in situ synthesized on the MWCNTC structure, which has been
demonstrated by Fig. 1(B) and (C). As a result, a remarkable peak
is obtained at +0.05 V. This reduction current peak is attributed to
the specific response of platinum oxide in PBS solutions, and cor-
respondingly, a flat double layer region at potential more positive
than +0.2 V should be ascribed to the platinum oxide formation. The
specific redox peaks of functionalized carbon nanotubes are not
observed for SPGFE/MWCNTC/PtNP because they are totally cov-
ered by the amplified background signal. In addition, the hydrogen
adsorption/desorption responses are observed at potentials more
negative than −0.45 V in 0.1 M PBS solutions. These proofs also
confirm the successful fabrication of SPGFE/MWCNTC/PtNP.
3.2. Electrocatalytic behavior of SPGFE/MWCNTC/PtNP toward
H2O2
The electrocatalytic behavior of SPGFE/MWCNTC/PtNP toward
H2O2 was initially investigated with cyclic voltammetry. Fig. 3(A)
depicts the typical cyclic voltammograms of the bare SPGFE and
SPGFE/MWCNTC/PtNP in the absence and presence of 10 mM H2O2.
Low background noises are observed on both electrodes in 0.1 M
PBS solutions without H2O2. The current peak at around 0 V for
SPGFE/MWCNTC/PtNP is assigned to the specific response of plat-
inum nanoparticles in PBS solutions, which has been demonstrated
by Fig. 2. When 10 mM H2O2 is added, the bare SPGFE still exhibits
no identifiable current response, while the SPGFE/MWCNTC/PtNP
provides a remarkable reduction signal of H2O2 at −0.2 V. It reveals
that the proposed SPGFE/MWCNTC/PtNP can significantly enhance
the electrocatalytic reduction of H2O2 in neutral solutions.
To further confirm the prominent electrocatalytic perfor-
mances of the proposed SPGFE/MWCNTC/PtNP, the fabricated
electrode as well as electrodes modified with only MWCNTC
(SPGFE/MWCNTC) or PtNPs (SPGFE/PtNP) was used to moni-
tor hydrogen peroxide with the chronoamperometric technique.
For comparison, the electrocatalytic performances of platinum

X. Niu et al. / Electrochimica Acta 65 (2012) 97–103
101
Fig. 4. (A) Effects of the CV deposition cycle on the reduction current of 0.1 mM H2O2
at −0.4 V, and (B) effects of the applied potential on the amperometric response of
Fig. 5. (A) Typical amperometric responses for successive additions of H2O2 in 0.1 M
PBS solutions (pH 6.9) at SPGFE/MWCNTC/PtNP with an applied potential of −0.4 V
under a constant stir, and (B) plots of the reduction currents vs the concentrations
of H2O2.
0.1 mM H2O2 under a constant stir.
nanoparticle-loaded MWCNTs randomly adsorbed on the SPGFE
substrate (SPGFE/MWCNT/PtNP) by use of the common drop-
casting method for H2O2 were also recorded. Fig. 3(B) shows
the typical amperometric responses of different modified elec-
trodes measured at a potential of −0.4 V in 0.1 M PBS solutions
with successive additions of H2O2. At this potential, these elec-
trodes will not provide the specific signal of platinum, and the
attributions from hydrogen adsorption/desorption responses are
also very limited. In comparison with the bare SPGFE, both
SPGFE/MWCNTC and SPGFE/PtNP can greatly enhance the elec-
trocatalytic reduction of H2O2. As shown in Fig. 3(B), when the
carbon nanotube/platinum hybrid structures (MWCNT/PtNP and
MWCNTC/PtNP) are introduced on the SPGFE substrate, both elec-
trodes (SPGFE/MWCNT/PtNP and SPGFE/MWCNTC/PtNP) turn to be
more sensitive toward additions of H2O2. Encouragingly, among
these modified electrodes, the proposed SPGFE/MWCNTC/PtNP
presents the most sensitive responses, especially for high concen-
tration H2O2. It is initially considered that this phenomenon mainly
attributes to the property that carbon nanotubes vertically aligned
on the electrode surface can offer more active sites and surface
areas for the loading of PtNPs [24]. Besides, chemically immobilized
carbon nanotubes can play a role of the electron bridge connect-
ing the electrode body with the analytes, providing more electron
communication tunnels and making electron transfer faster due
to the high conductance of the edge plane [1,13,17]. The efficient
contact between platinum nanoparticles and the top ends of car-
bon nanotubes, as shown in Fig. 1(C), greatly facilitates the electron
transfer.
3.3. Parameter optimization
Prior to quantitative measurements of H2O2, several experi-
mental parameters affecting the detecting system were further
optimized. Fig. 4(A) depicts the effect of the CV deposition cycle
which determines the quantity and size of PtNPs on the reduction
current of 0.1 mM H2O2. The current response increases corre-
spondingly with the deposition cycle number expanding to one
hundred cycles. When a deposition cycle of two hundred is selected,
the current response of H2O2 exhibits a sharp decrease. It is roughly
considered that too long deposition time may result in the agglom-
eration of PtNPs and reduce the electrocatalytic ability of PtNPs
[31]. Therefore, a CV deposition of one hundred cycles is employed
to prepare PtNPs in the following research.
Fig. 4(B) shows the influence of the applied potential on the
amperometric response of 0.1 mM H2O2. When +0.4 V is used, an
oxidation response is observed. At potentials more negative than
+0.15 V, H2O2 is electrochemically reduced in neutral solutions, and
the current signal increases accordingly with the applied potential

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X. Niu et al. / Electrochimica Acta 65 (2012) 97–103
solutions. The fabricated non-enzymatic sensor exhibited high sen-
sitivity, good reproducibility and excellent selectivity for H2O2
determination. The results also revealed that the proposed PtNP-
modified carbon nanotube clusters vertically aligned on the SPGFE
surface could provide preferable electrocatalysis performances
for H2O2 reduction than the common PtNP-modified CNTs. The
proposed carbon nanotube cluster/metal hybrid nanostructure is
expected to be a promising candidate as a scaffold for the fabrica-
tion of biosensors.
Supporting information
Supporting information contains the AFM pattern of MWCNTC
immobilized on the SPGFE substrate by self-assembly.
Acknowledgments
This work was financially supported by Science and Technol-
ogy Commission of Shanghai Municipality (STCSM, Contract No.
10dz2220500 and No. 10391901600) and Ministry of Education of
the People’s Republic of China (Contract No. WK1014051).
Fig. 6. Typical amperometric responses of 1 mM H2O2, ascorbic acid (AA),
dopamine (DA), uric acid (UA) and glucose in 0.1 M PBS solutions (pH 6.9) at
SPGFE/MWCNTC/PtNP with an applied potential of −0.4 V under a constant stir.
Appendix A. Supplementary data
negatively shifting to −0.6 V. With consideration of the interfer-
ences from other physiological materials, the applied potential of
−0.4 V is regarded as an appropriate compromise between sensi-
tivity and selectivity.
Supplementary data associated with this article can be found, in
the online version, at doi:10.1016/j.electacta.2012.01.030.
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Quantitative amperometric measurements of H2O2 were car-
ried out under the above optimum conditions. Fig. 5(A) presents the
typical amperometric responses for successive additions of H2O2
at the proposed SPGFE/MWCNTC/PtNP. The reduction currents, as
shown in Fig. 5(B), linearly increase with H2O2 concentrations
in the scope from 5 to 2000 ␮M with a correlation coefficient of
0.9912. As for higher concentration H2O2, the proposed electrode
slightly suffers from the common saturation effect. The limit of
detection is calculated to be as low as 1.23 ␮M, which is compa-
rable or even lower to that of modified silver paste electrodes [35]
and nanoporous gold electrodes [36]. Such excellent performances
can be attributed to the outstanding electrocatalytic activity of
nanostructured platinum and aligned CNTs and their beneficial
synergistic effect. It should be mentioned that aligned carbon nano-
tubes without uniform lengths may amplify the background noise
and restrict the detection limit. Hence, future work is worthy to
reduce the background noise.
Good reproducibility is another attractive feature of the pro-
posed SPGFE/MWCNTC/PtNP. Measurements of 1 mM H2O2 at eight
prepared electrodes lead to repeatable results with a relative stan-
dard deviation (RSD) of 6.9%. In order to investigate the selectivity
of the non-enzymatic sensor, the possible interferences from sev-
eral physiological materials including ascorbic acid (AA), dopamine
(DA), uric acid (UA) and glucose were assessed. As shown in Fig. 6,
it is found that there is no distinct influence from additions of 1 mM
AA, DA, UA and glucose upon the detection of H2O2 (1 mM), indicat-
ing that the fabricated non-enzymatic electrode can be applied for
the selective detection of H2O2 in the presence of these common
physiological materials.
4. Conclusions
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