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Electrochimica Acta 60 (2012) 314– 320

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Electrochimica Acta

j ourna l ho me pag e: www.elsev ier .com/ locate /e lec tac ta

Architecture of poly(o-phenylenediamine)–Ag nanoparticle composites for ahydrogen peroxide sensor

Li Wang, Haozhi Zhu, Yonghai Song ∗, Li Liu, Zhifang He, Lingli Wan, Shouhui Chen, Ying Xiang,Shusheng Chen, Jie ChenCollege of Chemistry and Chemical Engineering, Jiangxi Normal University, Nanchang 330022, People’s Republic of China

a r t i c l e i n f o

Article history:Received 22 April 2011Received in revised form 2 November 2011Accepted 13 November 2011Available online 22 November 2011

Keywords:ElectropolymerizationElectrodepositiono-PhenylenediamineAg nanoparticlesHydrogen peroxide

a b s t r a c t

A novel strategy to fabricate a hydrogen peroxide (H2O2) sensor was developed by electrodepositingAg nanoparticles (AgNPs) on a poly(o-phenylenediamine) (PoPD) film modified glassy carbon electrode(GCE). Firstly, the o-phenylenediamine was polymerized on a GCE by potential cycling to produce PoPDfilm. Then the AgNPs were electrodeposited on the PoPD film to form AgNPs/PoPD/GCE. The morphologyof the electropolymerized PoPD film and the electrodeposited AgNPs were characterized by atomic forcemicroscopy. The results showed the PoPD film was porous and the AgNPs dispersed uniformly on thePoPD film. Cylic voltammetry and amperometry were used to evaluate electrocatalytic properties of theAgNPs/PoPD/GCE. The electrode displayed good electrocatalytic activity in the reduction of H2O2 andcould be used as a sensor for H2O2 detection. The sensor exhibited fast amperometric response to H2O2

with high selectivity, good reproducibility and stability. The linear range was 6.0 �M to 67.3 mM with adetection limit of 1.5 �M. Thus, it is considered to be an ideal candidate for practical application.

© 2011 Elsevier Ltd. All rights reserved.

1. Introduction

The accurate determination of hydrogen peroxide (H2O2) hasbecome extremely important in recent years because H2O2 iswidely used in food, pharmaceutical, chemical and biochemicalindustries. Many methods such as titrimetry [1], spectrofluorom-etry [2,3], spectrophotometry [4,5], chemiluminescence [6] andelectrochemistry [7,8] have been used to measure concentrationof H2O2.

Recently, electrochemical methods have attracted much atten-tion due to low cost and high sensitivity. Mediating metal or metaloxide nanoparticles (NPs) on an electrode as a catalyst, which canbe used to determine the amount of trace H2O2 exactly, is a hottopic owing to their large specific surface areas, excellent conduc-tivities and catalytic activities. Many NPs, including AuNPs [9,10],AgNPs [11,12], PdNPs [13], PtNPs [14–16], and SiO2NPs [17], etc.,have been widely used to construct electrochemical sensors forH2O2 detection. Among these sensors, the sensors based on AgNPsexhibited an extremely fast amperometric response, a low detec-tion limit and a wide linear range to detect H2O2. A large numberof studies showed that the sensor’s catalytic properties dependedstrongly on the size, distribution and shape of AgNPs on electrodes[18,19].

∗ Corresponding author. Tel.: +86 791 88120862; fax: +86 791 88120861.E-mail addresses: yhsong20048@hotmail.com, yhsong@jxnu.edu.cn (Y. Song).

To obtain a good catalytic activity, electrodeposition of Ag+ in asolution containing DNA molecules or chitosan molecules to pro-duce small AgNPs by decreasing the reduction rate of Ag+ hasbeen proposed [20,21]. However, the size of AgNPs was about50 nm and the packing density of AgNPs was very high, whichwas unfavorable for catalytic activity due to the decrease of totalsurface area. In our previous studies, DNA [18] or collagen [19]was firstly assembled on the electrode surface and formed spon-taneously porous networks which resulted in the formation ofsmall AgNPs with uniform dispersion. However, these biomacro-molecules inhibited largely electron transfer. Carbon nanotubes(CNTs) have also been used to modify electrodes for AgNPs depo-sition and enhance electron transfer. Since the discovery of CNTsin 1991 by Iijima [22], they have attracted a considerable interestbecause of their excellent electrical properties and a large sur-face for metal NPs deposition or enzyme adsorption on electrodes.The remarkable conductivity, electrocatalytic and electrochemi-cal properties of CNTs have led to an explosion of research in thefield of electrochemical sensors in recent years [23,24]. However,it is difficult to produce uniform dispersion of the electrodepositedAgNPs owing to lack of functional group. Recently, supramolecularmicrofibrils of o-phenylenediamine (o-PD) decorated with AgNPshave been developed for H2O2 detection [25]. The conductive poly-mer can obviously enhance electron transfer and provide manysites to produce small AgNPs and to disperse uniformly these AgNPson the microfibrils, but it is difficult to immobilize the microfibrilson an electrode surface. The poor immobilization always results ina short life of the sensor.

0013-4686/$ – see front matter © 2011 Elsevier Ltd. All rights reserved.doi:10.1016/j.electacta.2011.11.045

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Fig. 1. (A) CVs of bare GCE in 1.0 M H2SO4 solution containing 50 mM o-PD. Scan rate: 100 mV s−1. (B) CVs of PoPD/GCE in 0.2 M PBS (pH 7.0) at various scan rates: 10 mV s−1

(a), 20 mV s−1 (b), 50 mV s−1 (c), 100 mV s−1 (d), 150 mV s−1 (e), 200 mV s−1 (f), 250 mV s−1 (h), 300 mV s−1 (i), 350 mV s−1 (j), 400 mV s−1 (k) and 450 mV s−1 (l). (C) AFM and(D) phase image of the PoPD/GCE. The horizontal arrow in (A) and (B) indicates the initial scan direction and its end indicates starting potential.

In this work, we have exploited AgNPs electrodeposited on apoly(o-phenylenediamine) (PoPD) film that was firstly electropoly-merized on the surface of a glassy carbon electrode (GCE) tofabricate a H2O2 sensor. The conductive PoPD formed a three-dimensional (3D) porous film that immobilized firmly on theelectrode surface. The 3D porous film resulted in the formation anduniform dispersion of small AgNPs in subsequent Ag+ electrodepo-sition. The AgNPs/PoPD/GCE exhibited remarkable catalytic activityfor H2O2 reduction with fast amperometric response, low detectionlimit and wide linear range.

2. Experimental

2.1. Chemicals

o-Phenylenediamine (o-PD) was purchased fromAldrich–Sigma. Other reagents were purchased from BeijingChemical Reagent Factory (Beijing, China). All chemicals wereof analytical grade and used without further purification. Allsolutions were prepared with ultra-pure water which was purifiedby a Millipore-Q System (18.2 M� cm). The solutions were deoxy-genated with nitrogen before experiments. Buffer solutions wereprepared with H2SO4, Na2SO4, Na2HPO4 and Na2HPO4 to obtainpH values in the range of 1.0–8.0.

2.2. Preparation of AgNPs/PoPD/GCE

A clean GCE was cycled between −0.6 and 1.3 V at 100 mV s−1

for 30 cycles in 1.0 M H2SO4 solution containing 50 mM o-PD toobtain the PoPD/GCE. The AgNPs were prepared by potentiostatic

electrodeposition in a mixed solution of 0.1 M KNO3 and 3.0 mMAgNO3 on the PoPD/GCE to form AgNPs/PoPD/GCE.

2.3. Apparatus

All electrochemical measurements were carried out on a CHI660C electrochemical workstation (Shanghai Chenhua InstrumentCo., China) at room temperature in a conventional three-electrodesystem composed of a bare or modified GCE as working electrode,a platinum wire as auxiliary electrode and a saturated calomelelectrode (SCE) as reference electrode. The cyclic voltammetricexperiments were performed in a stagnant solution. The amper-ometric experiments were carried out under continuous stirringusing a magnetic stirrer.

Atomic force microscopy (AFM) measurements were carried outwith an AJ-III (Shanghai Aijian Nanotechnology, China) in tappingmode. Standard silicon cantilevers (spring constant 0.6–6 N m−1)were used at their resonance frequency (60–150 kHz).

3. Results and discussion

3.1. Fabrication of PoPD/GCE

The PoPD/GCE was fabricated by electropolymerizing o-PD on aGCE surface. Fig. 1A shows the cyclic voltammograms (CVs) of GCEin 1.0 M H2SO4 solution containing 50 mM o-PD. In the first anodicscan, there were two irreversible anodic peaks at 0.63 V (O1) and0.90 V (O2), respectively, which were ascribed to the oxidation ofo-PD that resulted in the polymerization of o-PD [26–30]. Evidencefor the formation of the PoPD was the reduction peak at −0.02 V (R3)

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in the reverse scan and its corresponding oxidation peak at −0.02 V(O3) in the second anodic scan. As can be seen in the second anodicscan, the currents of the two oxidation peaks (O1 and O2) decreasedpronouncedly, indicating that the conductivity of the PoPD film wasrelatively low. With the increasing of cycle numbers, the oxidationpeak O1 decreased gradually and O2 disappeared after two scans.The peaks O3 and R3 increased gradually during potential cycling,indicating that the PoPD film grew gradually on the GCE surface.The experimental results shown in Fig. 1A were very similar to pre-vious results [26–30]. Owing to the pronounced decreasing in thepeak current with an increasing number of cycles, the growth rateof PoPD film was considerably slow, and only a thin film of PoPDwas formed [29,30]. As the electropolymerization proceeded, thecolorless solution gradually became deep yellow, indicating that anoligomer formed at the electrode dissolved in the solution. Accord-ing to previous conclusion [26–28], the polymerization of o-PD andredox of PoPD could be expressed as follows:

NH2

NH2

n

NH

N

N

HN

+2H++2e

NH

HN

NH

HN

Fig. 1B shows the CVs of the as-prepared PoPD/GCE in 0.2 M

phosphate buffer solution (PBS, pH 7.0) in the scan rate range from10 to 450 mV s−1. In the potential range of −1.0–0.1 V, a pair ofreversible redox peaks with formal potential (E0 = (Epa + Epc)/2) of−0.55 V appeared for the PoPD/GCE. The peak located at −0.48 Vresulted from the oxidation of PoPD and its corresponding reduc-tion peak was observed at −0.63 V [29,30]. The peak currents grewas the scan rate increased. In the range of 10–100 mV s−1, the peakcurrents were proportional to the scan rate as shown by the inset1 in Fig. 1B, indicating that the electron transfer reaction involveda surface-confined process [19]. For scan rate range from 150 to450 mV s−1, the peak currents were dependent on the square rootof scan rate as shown by the inset 2 in Fig. 1B, indicating a diffusion-controlled process. As mentioned above, the redox process of PoPDwas companied with the transfer of H+. Thus, at high scan rate, theslow diffusion of H+ might control the electrochemical process andresult in the linear dependence of the peak current on the squareroot of scan rate.

The typical surface morphology of as-prepared PoPD/GCE ascharacterized by AFM is shown in Fig. 1C. The PoPD formed the3D network-like structure, which could be further proven by thecorresponding phase image (Fig. 1D). The porous structure couldincrease the effective electrode surface and improve the diffusionof analytes into the film.

3.2. Electrodeposition of AgNPs on PoPD network

CV was used to investigate the electrodepositing process of Ag+

both on bare and on PoPD film modified GCE. As shown in curvea in Fig. 2A, the bare GCE showed a cathodic peak at 0.30 V and asharp anodic peak at 0.49 V when scanned in a solution containing3.0 mM AgNO3 and 0.1 M KNO3. The cathodic peak was due to thereduction of Ag+ and the anodic peak was ascribed to the strippingof the electrodeposited AgNPs [18,19]. When the PoPD/GCE wasscanned in the same solution, the redox peak currents extremelydepressed and the peak potentials shifted in negative direction(curve b in Fig. 2A). The decrease of peak current indicated thatthe PoPD film partially blocked the reduction of Ag+, which wouldreduce the reduction rate of Ag+ thus only small AgNPs formed[18,19]. To obtain AgNPs modified electrode, the PoPD/GCE waselectrodeposited in this solution at −0.1 V.

Fig. 2B shows the CVs of AgNPs/PoPD/GCE in 0.2 M PBS (pH 7.0)at different scan rates. A pair of reversible redox peaks occurred,

which was similar to that of PoPD/GCE. The oxidation peak locatedat −0.36 V resulted from the oxidation of PoPD. The cathodic peaklocated at −0.55 V was ascribed to the reduction of the PoPD. Obvi-ously, the peak currents increased with the increased scan rate.Similarly, the electron transfer reaction involved a surface-confinedprocess during slower scan rate range from 10 to 100 mV s−1 (theinset 1 in Fig. 2B) and a diffusion-controlled process during fasterscan rate range from 150 to 450 mV s−1 (the inset 2 in Fig. 2B). Theelectrochemical behavior of the AgNPs/PoPD/GCE was similar tothat of the PoPD/GCE.

The electrochemical behavior of AgNPs/PoPD/GCE shows astrong dependence on the pH of electrolyte solution (Fig. 2C). Bothreduction and oxidation peak potentials shifted negatively and thepeak currents gradually decreased as the pH increased from 1.0to 8.0, suggesting H+ participated in the electrochemical process.However, the peak potentials and currents changed slowly after

the pH increased to 4.0. Therefore, this modified electrode could beused for electro-analytical or other applications in a wide range ofpH.

The typical surface morphology of as-preparedAgNPs/PoPD/GCE was characterized by AFM and the result isshown in Fig. 2D. In the AFM image, there were many AgNPsuniformly dispersed on the 3D porous PoPD film. The size of theseAgNPs was measured to be about 20 nm by section-analysis (theinset in Fig. 2D).

3.3. Electrocatalytic behaviors of AgNPs/PoPD/GCE

Fig. 3 shows the CVs of PoPD/GCE (curve a) and AgNPs/PoPD/GCE(curve b) in 0.2 M PBS (pH 7.0). The CV curve of AgNPs/PoPD/GCEwas almost the same as that of PoPD/GCE, but the peak currentsincreased and the peak potentials shifted positively.

Fig. 4 shows the CVs of AgNPs/PoPD/GCE in 0.2 M PBS (pH 7.0)in the absence (curve a) and presence (curve b) of 3.0 mM H2O2.It could be seen that the reduction peak increased greatly and theoxidation peak almost disappeared in the presence of 3.0 mM H2O2(curve b) as compared with that in the absence of H2O2 (curve a).The potential of reduction peak shifted positively from −0.55 V to−0.5 V. Obviously, the AgNPs electrodeposited on the porous PoPDfilm catalyzed the reduction of H2O2 and produced a remarkablecatalytic current. The high catalytic current was mainly ascribed tothe large number of small AgNPs on the electrode and the quan-tum scale dimension of these AgNPs [18,19,31]. The 3D porousPoPD film on the electrode provided a medium to greatly increasethe quantity of the AgNPs and to reduce the dimension of theelectrodeposited AgNPs. The large surface-to-volume ratio of thesmall AgNPs produced a large total surface area that provided morechance to contact H2O2. Thus, these AgNPs produced more activesites on the same electrode surface in the NPs-assisted catalysis[31].

To optimize the electrocatalytic performance ofAgNPs/PoPD/GCE in 0.2 M PBS (pH 7.0) for reduction of H2O2,some parameters related to the formation of PoPD film and AgNPsdeposition, such as the concentration of o-PD, numbers of poten-tial cycles, electrodeposition time of AgNPs and pH of electrolytesolution, were investigated.

Firstly, the effect of o-PD concentration used for the formationof the PoPD film on the electrocatalytic reduction of H2O2 was

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Fig. 2. (A) CVs of GCE (a) and PoPD/GCE (b) in a solution of 0.1 M KNO3 and 3.0 mM AgNO3. Scan rate: 50 mV s−1. Inset: magnification of curve (b). (B) CVs of AgNPs/PoPD/GCEin 0.2 M PBS (pH 7.0) at various scan rates: 10 mV s−1 (a), 20 mV s−1 (b), 50 mV s−1 (c), 100 mV s−1 (d), 150 mV s−1 (e), 200 mV s−1 (f), 250 mV s−1 (h), 300 mV s−1 (i), 350 mV s−1

(j), 400 mV s−1 (k) and 450 mV s−1 (l). (C) Plot of the peak potential (Epeak) and current (Ipeak) versus pH for the AgNPs/PoPD/GCE. (D) AFM image of AgNPs/PoPD/GCE. Thehorizontal arrow in (A) and (B) indicates the initial scan direction and its end indicates starting potential.

investigated. Fig. 5A shows the plot of peak current forAgNPs/PoPD/GCE in a 0.2 M PBS (pH 7.0) containing 1 mM H2O2versus o-PD concentration. The AgNPs/PoPD/GCE was constructedby electropolymerizing PoPD in a solution with different o-PD con-centration and subsequent electrodepositing AgNPs on the PoPD

-1.0 -0.8 -0. 6 -0. 4 -0 .2 0. 0 0.2

-30

-20

-10

0

10

20

30

ba

I/μ

A

E vs SCE/V

Fig. 3. CVs of PoPD/GCE (a) and AgNPs/PoPD/GCE (b) in 0.2 M PBS (pH 7.0). Scanrate: 50 mV s−1. The horizontal arrow indicates the initial scan direction and its endindicates starting potential.

film. There was a noticeable increase in the current response withthe increasing of o-PD concentration. The peak current reachedthe maximal value at 50 mM. After that, the current decreasedgradually as the o-PD concentration further increased. This phe-nomenon might be ascribed to the following two aspects. The low

-1.0 -0. 8 -0.6 -0.4 -0 .2 0.0 0.2

-70-60-50-40-30-20-10

0102030

b

a

I/µA

E vs SCE/V

Fig. 4. CVs of AgNPs/PoPD/GCE in 0.2 M PBS (pH 7.0) in the absence (a) and presence(b) of 3.0 mM H2O2. Scan rate: 50 mV s−1. The horizontal arrow indicates the initialscan direction and its end indicates starting potential.

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0 20 40 60 80 100

10

15

20

25

30

35

40

45

50

55A

I peak

/μA

co-PD/mmol L-110 20 30 40 50 60

28303234363840424446485052

B

I peak

/μA

Cycles/n

100 150 200 250 300 350 400 450 500 550-25

-30

-35

-40

-45

-50

-55C

I peak

/ μA

t/s4.5 5.0 5. 5 6.0 6. 5 7.0 7. 5 8.0

-25

-30

-35

-40

-45

-50

-55D

I peak

/μA

pH

Fig. 5. The effects of concentration of o-PD, numbers of potential cycle, electrodeposition time of AgNPs and pH of PBS on reduction of H2O2. Electrolyte solution: 0.2 MPBS + 1.0 mM H2O2.

o-PD concentration resulted in few PoPD electropolymerized onthe electrode surface and accordingly few AgNPs was deposited onthe PoPD film [32], which gave poor catalytic activity. On the otherhand, the high o-PD concentration might produce compact PoPDfilm on the electrode surface [33]. The compact PoPD film wouldproduce some Ag blocks, which decreased the effective area of Agcatalyst on the electrode surface and accordingly resulted in poorcatalytic activity.

The effect of number of potential cycles in the formation of PoPDfilm on the reduction of H2O2 was also studied. Fig. 5B shows theplot of peak current for AgNPs/PoPD/GCE in a 0.2 M PBS (pH 7.0)containing 1.0 mM H2O2 versus the number of potential cycles.The number of potential cycles determined the uniformity, poros-ity, and thickness of the PoPD film on GCE. Under few potentialcycles, only a small amount of sparse PoPD film was formed on theGCE surface, which would induce the deposition of few AgNPs. Theresulted electrode showed a poor catalytic activity to H2O2. Withthe increasing of the number of potential cycles, the thickness ofPoPD film increased and the porosity decreased gradually, whichwould also be unfavorable for the formation of AgNPs with highcatalytic activity. As shown in Fig. 5B, the maximal current valueappeared at 30 cycles, which was chosen as the optimal number ofpotential cycles.

Fig. 5C shows the plot of peak current of AgNPs/PoPD/GCE versuselectrodeposition time of AgNPs in a 0.2 M PBS (pH 7.0) contain-ing 1.0 mM H2O2. The current response increased gradually withincreasing electrodeposition time and reached maximal value at350 s. After that, the current response decreased. This turning pointmight be ascribed to the fact that the AgNPs would become ratherbig with excessive electrodeposition time, which could decrease its

electrocatalytic ability. Thus, 350 s was chosen for the formation ofAgNPs on PoPD film.

The effect of pH of the PBS on the catalytic reduction of H2O2 wasalso investigated. Fig. 5D shows the plot of amperometric responseof the sensor versus different pH values in 0.2 M PBS (4.9–8.0) with1.0 mM H2O2. The AgNPs/PoPD/GCE showed higher electrocatalyticactivity in 0.2 M PBS of pH 7.0. Thus, the optimum pH (7.0) valuewas selected for the determination of H2O2 in this work.

10008006004002000

-500

-400

-300

-200

-100

0

50403020100

0.0

0.3

0.6

0.9

1.2

1.5

1

2

I/m

A

cH2O2/mmol L-1 2

1

I/µA

t/s

Fig. 6. Chronoamperometric responses of PoPD/GCE (a) and AgNPs/PoPD/GCE (b) tothe successive addition of H2O2 to 0.2 M PBS (pH 7.0). The inset is the correspondingcalibration curves. Applied potential: −0.5 V.

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Table 1Comparison of the performance of various H2O2 sensors constructed from AgNPs.

Detection limit (�mol L−1) Linear range (mmol L−1) Sensitivity (�A �M−1) References

PoPD/GCE 3.9 0.010–42.3 3.56 × 10−4 This workAgNPs/PoPD/GCE 1.5 0.006–67.3 3.57 × 10−2 This workAgNPs/DNA/GCE 1.7 0.004.0–16.0 – [18]AgNPs/Collagen/GCE 0.7 0.005–40.6 – [19]AgNPs-NFs/GCE 62 0.10–80.0 – [25]AgNPs-GN-R/GCE 28 0.1–40.0 – [34]AgNPs-MWCNT/Au electrode 0.5 0.05–17 1.42 × 10−3 [35]

Table 2Possible interferences tested with the hydrogen peroxide sensor (record in 0.2 M PBS, scan rate 50 mV s−1).

Objective substrates (1.0 mmol L−1) Interferents (mmol L−1)

AA UA Na2SO4 Fe3+ SO32− Ethanol Glucose

1 5 10 1 5 10 1 5 10 1 5 1 5 1 5 10 1 5 10

H2O2 ©a © © © © © © © © © •b © • © © © © © ©a No interference (variance of catalytic current ≤6%).b Interference (variance of catalytic current >6%).

Fig. 6 shows the typical steady-state current response of thePoPD/GCE (curve 1) and the AgNPs/PoPD/GCE (curve 2) to suc-cessive additions of H2O2 into stirred 0.2 M PBS (pH 7.0) underoptimized conditions. When the H2O2 was added, the reductioncurrent of AgNPs/PoPD/GCE rose sharply to reach a maximumsteady-state value within 2 s. The fast response was mainly ascribedto the fact that the 3D PoPD porous structure greatly enlargedthe total surface area of the AgNPs and enhanced the transfer ofelectrolyte and H2O2. The inset in Fig. 6 shows the correspondingcalibration curves for H2O2. The response of AgNPs/PoPD/GCE waslinear with H2O2 concentration from 6.0 �M to 67.3 mM (r = 0.998;n = 30). The detection limit was estimated to be 1.5 �M at a signal-to-noise ratio of 3. A comparison of the performance of our newlydesigned sensor with those already reported in literature workregarding the performance of the H2O2 assay is shown in Table 1.Up to now, many sensors have been developed based on AgNPsfor the detection of H2O2, and each of them have some advan-tages and limitations [18,19,33,34]. Taking AgNPs/collagen/GCE[19] as an example, the detection limit was pretty low, whilethe linear range was rather narrow. Recently, AgNPs decoratedgraphene modified GCE were constructed for the detection of H2O2with a detection limit of 28 �M and a linear range of 100 �M to40 mM [34]. Compared with these sensors, the linear responserange, the sensitivity and the detection limit for H2O2 detectionof the sensor prepared in this work were much better than otherresults.

3.4. Selectivity and stability

The selectivity of the H2O2 sensor was evaluated by comparingthe amperometric response to 1.0 mM H2O2 before and after addingpossible interferents into 0.2 M PBS (pH 7.0). No interference wasobservable after 10-fold concentration of ascorbic acid (AA), uricacid (UA), Na2SO4, ethanol and glucose were added. Fe3+ and SO3

2−

in 5-fold concentration showed interference to H2O2 detection. Theresults are shown in Table 2. Thus, the electrode was selective forH2O2 and could be applied to the determination of H2O2 in realsamples.

The reproducibility of the current signal for the same electrodeto 1.0 mM H2O2 was examined in 0.2 M PBS (pH 7.0). The relativestandard deviation (RSD) was 3.5% for six successive measure-ments. The electrode-to-electrode reproducibility was determinedin the presence of 1.0 mM H2O2 in 0.2 M PBS (pH 7.0) with sevendifferent electrodes. They yielded a RSD of 4.6%.

The stability of the AgNPs/PoPD/GCE was explored through theresponse to 1.0 mM H2O2. When the modified electrode was storedat 4 ◦C for 15 days, the amperometric response to 1.0 mM H2O2decreased only by 1.8%, indicating a good stability.

4. Conclusions

In this work, a novel method has been introduced to fabricateH2O2 sensor. o-PD was first electropolymerized on GCE to pro-duce a 3D porous PoPD film by potential cycling. Then AgNPs wereelectrodeposited on the PoPD-modified GCE. Our experiments con-firmed that when the o-PD concentration was 50 mM, the numberof potential cycles for PoPD formation was 30, the electrodepositiontime for AgNPs formation was 350 s, and pH of PBS was 7.0, the sen-sor showed the maximal electrocatalytic ability for the reduction ofH2O2. The obtained sensor exhibited fast amperometric response,low detection limit and wide linear range for H2O2 detection. More-over, it also has high sensitivity, good reproducibility and stability.

Acknowledgments

This work was financially supported by National Natural Sci-ence Foundation of China (20905032, 21065005 and 21174058),Natural Science Foundation of Jiangxi Province (2008GZH0028),Foundation of Jiangxi Educational Committee (GJJ10389), the StateKey Laboratory of Electroanalytical Chemistry (2008003), YoungScientist of Jiangxi Province (20112BCB23006) and the ScientificResearch Foundation for the Returned Overseas Chinese Scholars,State Education Ministry.

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