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Preparation of Ag nanoparticle-decorated polypyrrole colloids and their application for H2O2 detection
Electrochemistry Communications 13 (2011) 785–787
Contents lists available at ScienceDirect
Electrochemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e l e c o m
Preparation of Ag nanoparticle-decorated polypyrrole colloids and their application for H2O2 detection Xiaoyun Qin, Wenbo Lu, Yonglan Luo, Guohui Chang, Xuping Sun ⁎ Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, School of Chemistry and Chemical Industry, China West Normal University, Nanchong 637002, Sichuan, China
a r t i c l e
i n f o
Article history: Received 15 April 2011 Received in revised form 3 May 2011 Accepted 4 May 2011 Available online 12 May 2011 Keywords: Polypyrrole colloid Silver nanoparticle Enzymeless hydrogen peroxide detection
a b s t r a c t The present communication reports on the preparation of Ag nanoparticle-decorated polypyrrole colloids (AgNP-PPyCs) by heating a AgNO3 aqueous solution and pre-formed PPy colloids solution in the absence of any external reducing agent. It suggests that these AgNP-PPyCs exhibit remarkable catalytic performance toward H2O2 reduction. This enzymeless H2O2 sensor shows a fast amperometric response time of less than 2 s, and the corresponding linear range and detection limit are estimated to be from 0.1 mM to 90 mM (r = 0.998) and 1.05 μM, respectively, at a signal-to-noise ratio of 3. © 2011 Elsevier B.V. All rights reserved.
1. Introduction H2O2 participates in a wide range of enzymatic reactions, playing an important role in the fields of chemistry, biology, clinical control and environmental protection, and therefore, its detection has been paid considerable research interest [1–3]. Up to now, many techniques including spectrometry, titrimetry, chemiluminescence, and electrochemistry have been employed for determination of H2O2 [4–8]. Among them, electrochemical techniques are a promising tool for the construction of simple, low-cost sensors owing to their high sensitivity, good selectivity, and ease of operation [8]. Most previous studies on this subject invovled the use of enzymes which can accelerate the electron transfer between the electrodes and H2O2 [9,10]. To construct enzyme-based sensors, a wealth of nanomaterials such as biopolymers, nanostructures, and sol-gel matrices are also employed to immobilize the enzymes and at the same time, to reduce the possibility of protein denaturing [11–14]. However, their application is limited because enzymes are expensive and easily denatured [15]. This issue was subsequently circumvented by using nanostructures such as noble metal nanoparticles, carbon nanotubes, and reduced graphene oxide as catalysts to calatyze the oxidation or reduction of H2O2 [16–19], leading to enzymeless H2O2 sensors. Furthermore, the electrochemical behavior and kinetic analysis of H2O2 reduction on Ag nanoparticles (AgNPs) have also been evaluated by Compton and co-workers [20,21].
⁎ Corresponding author. E-mail address: [email protected] (X. Sun). 1388-2481/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2011.05.002
In this communication, we report on the preparation of AgNPdecorated polypyrrole colloids (AgNP-PPyCs) by heating a AgNO3 aqueous solution and pre-formed PPy colloids solution in the absence of any external reducing agent. It is found that such AgNP-PPyCs exhibit remarkable catalytic performance toward the reduction of H2O2. This enzymeless H2O2 sensor exhibited a fast amperometric response time of less than 2 s and the corresponding linear range and detection limit was estimated to be from 0.1 mM to 90 mM (r = 0.998) and 1.05 μM, respectively, at a signal-to-noise ratio of 3. 2. Experimental 2.1. Reagents and materials All chemicals were purchased from Aladin Ltd. (Shanghai, China), and used as received without further purification. The water used throughout all experiments was purified through a Millipore system. Phosphate buffer saline (PBS) was prepared by mixing stock solutions of NaH2PO4 and Na2HPO4 and a fresh solution of H2O2 was prepared daily. 2.2. Preparation of H2O2 sensor PPy colloids were synthesized according to a reported method [22]. In a typical preparation experiment, to 12 mL of deionized water 0.02 g of ferrous chloride (FeCl2) was added with stirring, where 0.2 mL of pyrrole has been pre-dispersed. After addition of 1 mL of H2O2 to the pyrrole/FeCl2/H2O mixture, pyrrole polymerization was initiated and lasted for overnight. Finally, the dark precipitated PPy colloids were centrifuged and further washed with deionized water
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X. Qin et al. / Electrochemistry Communications 13 (2011) 785–787
and acetone for three times respectively. The powder was then redispersed in 5 mL of deionized water. To prepare AgNP-PPyCs, 20 μL of 0.1 M AgNO3 aqueous solution was added into the aforementioned PPy colloids, and then the resulting solution was heated at 90 °C for 60 min to give dark precipitate which was washed with distilled water several times and then dispersed in water for characterization and future use. 2.3. Characterization of physical properties Scanning electron microscopy (SEM) measurements were made on a XL30 ESEM FEG scanning electron microscope at an accelerating applied potential of 20 kV. The sample for SEM characterization was prepared by place a drop of the dispersion on a bare indium tin oxide coated glass substrate (ITO) and air-dried at room temperature. 2.4. Electrode preparation and electrochemical measurements Electrochemical measurements were performed with a CHI 660D electrochemical analyzer (CH Instruments, Inc., Shanghai). A conventional three-electrode cell was used, including a glassy carbon electrode (GCE, geometric area = 0.07 cm 2) as the working electrode, a Ag/AgCl (3 M KCl) electrode as the reference electrode, and platinum foil as the counter electrode. All potentials given in this work were referred to the Ag/AgCl electrode. All the experiments were carried out at ambient temperature. The suspension of AgNPPPyCs was dropped onto the pre-polished mirror like surface of GCE, chitosan was used as fixative to form a strong film to modify the electrode. 3. Results and discussion Fig. 1A shows low magnification SEM image of as-prepared PPy products, which clearly indicates that they consist exclusively of a large amount of submicrometer-scale particles. Higher magnification
Fig. 1. (A) Low and (B) high magnification SEM images and (C) the corresponding EDS of the PPy colloids.
Fig. 2. (A) Low and (B) high magnification SEM images and (C) the corresponding EDS of the PPy colloids after their incubation with a AgNO3 aqueous solution.
SEM image shown in Fig. 1B reveals that these particles are spherical in shape and well-separated from each other and have diameters ranging from 300 to 400 nm. The chemical composition of these colloids was determined by energy-dispersed spectrum (EDS) (Fig. 1C). The peaks of C and N are observed, indicating that the particles are formed from pyrrole. The observation of the peak of Cl element can be attributed to the fact that the polymerization of pyrrole by FeCl2 yields positively charged PPy structures and thus Cl as counter ions diffuse into the colloids for charge compensation. Other peaks originate from the ITO-coated glass substrate. All the above observations indicate the successful formation of PPy colloids. We further found that the preformed PPy colloids can reduce Ag + into metallic Ag in our present study. Fig. 2A shows low SEM image of the PPy colloids after their incubation with a AgNO3 aqueous solution, indicating that many white dots are observed on the surface of PPy colloid. High magnification SEM image shown in Fig. 2B reveals that
Fig. 3. Cyclic voltammetries (CVs) of bare GCE, PPyC/GCE, AgNP/GCE and AgNP-PPyC/ GCE in 0.2 M PBS at pH 6.5 in the presence of 1.0 mM H2O2 (scan rate: 20 mV/s).
X. Qin et al. / Electrochemistry Communications 13 (2011) 785–787
787
than for AgNP/GCE can result form a larger capacitance of double electric layer of the rougher surface of AgNP-PPyC/GCE [26]. Fig. 4 shows typical current–time plot of the AgNP-PPyC/GCE in N2-saturated 0.2 M PBS buffer (pH: 6.5) on consecutive step change of H2O2 concentrations. When an aliquot of H2O2 was dropped into the stirring PBS solution, the reduction current rose steeply to reach a stable value. The sensor could accomplish 95% of the steady state current within 2 s, indicating a fast amperometric response behavior. It is apparently seen that the steps showed in Fig. 4 are more horizontal in the region of lower concentration of H2O2 and the noises become higher with increased concentration of H2O2. Inset a shows the calibration curve of the sensor, and the low concentration part of this line is shown in inset b. The linear detection range is estimated to be from 0.1 mM to 90 mM (r = 0.998), and the detection limit is estimated to be 1.05 μM at a signal-to-noise ratio of 3. 4. Conclusions Fig. 4. Typical steady-state response of the AgNP-PPyC/GCE to successive injection of H2O2 into the stirred N2-saturated 0.2 M PBS at pH 6.5. Inset: the calibration curve (Applied potential: − 0.30 V).
these dots are about tens of nanometer in size. The chemical composition of the composites was determined by EDS (Fig. 2C). Compared with Fig. 1C, one additional intensive peak of Ag element is found, indicating that the nanoparticles are AgNPs. It should be noted that the PPy colloids still retain both the size and the morphology after the redox process, revealing their robust nature. The formation of such AgNP-PPyCs in our present study may be attributed to that the PPy colloids can effectively adsorb Ag(I) ions via coordination of their imino groups in the PPy chains to Ag(I) ions and then reduce in situ the as-adsorbed Ag(I) ions to form AgNPs [23]. In order to demonstrate the sensing application of such AgNPPPyCs, an enzymeless H2O2 sensor was constructed by deposition of the composites on a GCE surface (AgNP-PPyC/GCE). The PPy colloidmodified GCE (PPyC/GCE) was also similarly prepared. Fig. 3 shows the electrocatalytic responses of these electrodes toward the reduction of H2O2 in N2-saturated 0.2 M PBS at pH 6.5. In the presence of 1.0 mM H2O2, the AgNP-PPyC/GCE exhibits a remarkable catalytic reduction current peak about 49 μA centered at −0.40 V vs Ag/AgCl. However, the responses of both the bare GCE and PPyC/GCE toward the reduction of H2O2 are very weak. These observations indicate that the AgNPs supported on the PPyC exhibit excellent catalytic performance toward H2O2 reduction, and the observation of large catalytic current could be attributed to the large amount of AgNPs existing on the surface of the PPyC. Compared to the responses of citrate-protected AgNP-modified GCE (AgNP/GCE), the AgNP-PPyC/ GCE toward the reduction of H2O2 exhibits a 0.20 V positive shift of the peak potential. It can be attributed to the changed mass transport [20] and the existence of porosity in the AgNP-PPyC/GCE surface [24,25]. Although mass transport and electrode kinetics are known to vary significantly with particle size and surface coverage, both the size and surface coverage of citrate-protected AgNPs and AgNPs on PPyC are not the same and thus a fair comparison is hard to make at present time. A significantly more background current for AgNP-PPyC/GCE
In summary, heat-treatment of a AgNO3 aqueous solution and preformed PPy colloids solution has been proven to be an effective strategy to prepare AgNP-PPyCs. Most importantly, these AgNP-PPyCs are found to exhibit good catalytic activity toward H2O2 reduction. Our observations are significant for the following two reasons: (1) it is the first demonstration of using AgNP-PPyCs for enzymeless H2O2 detection; (2) it provides us a general methodology for the fabrication of noble metal nanoparticle-decorated PPy colloids for applications. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26]
N.V. Klassen, D. Marchington, H.C.E. McGovan, Anal. Chem. 66 (1994) 2921. M.C.Y. Chang, A. Pralle, E.Y. Isacoff, C.J. Chang, J. Am. Chem. Soc. 126 (2004) 15392. B. Wang, J. Zhang, Z. Pan, X. Tao, H. Wang, Biosens. Bioelectron. 24 (2009) 1141. Y. Song, L. Wang, C. Ren, G. Zhu, Z. Li, Sens. Actuators B 114 (2006) 1001. P.A. Tanner, A.Y.S. Wong, Anal. Chim. Acta 370 (1998) 279. R. Dringen, L. Kussmaul, B. Hampreeht, Brain Research Protocols 2 (1998) 223. T.C. Carmine, G. Bruchelt, T. Hahn, D. Niethammer, J. Biolumin. Chemilumin. 9 (1994) 267. M.N. Bui, X. Pham, K.N. Han, C.A. Li, Y.S. Kim, G.H. Seong, Sen. Actuators B 150 (2010) 436. L. Wang, E. Wang, Electrochem. Commun. 6 (2004) 225. Z. Cao, X. Jiang, Q. Xie, S. Yao, Biosens. Bioeletron. 24 (2008) 222. D. Shan, S. Wang, H. Xue, S. Cosnier, Electrochem. Commun. 9 (2007) 529. J. Wang, M. Musameh, Anal. Chem. 75 (2003) 2075. O. Nadzhafova, M. Etienne, A. Walcarius, Electrochem. Commun. 9 (2007) 1189. C. Shan, H. Yang, J. Song, D. Han, A. Ivaska, L. Niu, Anal. Chem. 81 (2009) 2378. X. Kang, J. Wang, H. Wu, I.A. Aksay, J. Liu, Y. Lin, Biosens. Bioelectron. 25 (2009) 901. C.M. Welch, C.E. Banks, A.O. Simm, R.G. Compton, Anal. Bioanal. Chem. 382 (2005) 12. Y. Li, J. Zhang, J. Xuan, L. Jiang, J. Zhu, Electrochem. Commun. 12 (2010) 777. J. Tian, S. Liu, X. Sun, Langmuir 26 (2010) 15112. S. Liu, J. Tian, L. Wang, H. Li, Y. Zhang, X. Sun, Macromolecules 43 (2010) 10078. F.W. Campbell, S.R. Belding, R. Raron, L. Xiao, R.G. Compton, J. Phys. Chem. C 113 (2009) 9053. S.R. Belding, F.W. Campbell, E.J.F. Dickinson, R.G. Compton, Phys. Chem. Chem. Phys. 12 (2010) 11208. Z. Liu, Y. Liu, S. Poyraz, X.Y. Zhang, Electrochem. Commun. 47 (2011) 4421. C. Zhao, Q. Zhao, Q. Zhao, J. Qiu, C. Zhu, S. Guo, J. Photochem. Photobiol. A 187 (2007) 146. I. Streeter, G.G. Wildgoose, L. Shao, R.G. Compton, Sensors and Actuators B 133 (2008) 462. X. Dai, G.G. Wildgoose, C. Salter, A. Crossley, R.G. Compton, Anal. Chem. 78 (2006) 6102. A.J. Bard, L.R. Faulkner, Electrochemical Methods, Fundamentals and Applications, E-Publishing, Inc. John Wiley & Sons, 2001, pp. 9–18.
Contents lists available at ScienceDirect
Electrochemistry Communications j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / e l e c o m
Preparation of Ag nanoparticle-decorated polypyrrole colloids and their application for H2O2 detection Xiaoyun Qin, Wenbo Lu, Yonglan Luo, Guohui Chang, Xuping Sun ⁎ Chemical Synthesis and Pollution Control Key Laboratory of Sichuan Province, School of Chemistry and Chemical Industry, China West Normal University, Nanchong 637002, Sichuan, China
a r t i c l e
i n f o
Article history: Received 15 April 2011 Received in revised form 3 May 2011 Accepted 4 May 2011 Available online 12 May 2011 Keywords: Polypyrrole colloid Silver nanoparticle Enzymeless hydrogen peroxide detection
a b s t r a c t The present communication reports on the preparation of Ag nanoparticle-decorated polypyrrole colloids (AgNP-PPyCs) by heating a AgNO3 aqueous solution and pre-formed PPy colloids solution in the absence of any external reducing agent. It suggests that these AgNP-PPyCs exhibit remarkable catalytic performance toward H2O2 reduction. This enzymeless H2O2 sensor shows a fast amperometric response time of less than 2 s, and the corresponding linear range and detection limit are estimated to be from 0.1 mM to 90 mM (r = 0.998) and 1.05 μM, respectively, at a signal-to-noise ratio of 3. © 2011 Elsevier B.V. All rights reserved.
1. Introduction H2O2 participates in a wide range of enzymatic reactions, playing an important role in the fields of chemistry, biology, clinical control and environmental protection, and therefore, its detection has been paid considerable research interest [1–3]. Up to now, many techniques including spectrometry, titrimetry, chemiluminescence, and electrochemistry have been employed for determination of H2O2 [4–8]. Among them, electrochemical techniques are a promising tool for the construction of simple, low-cost sensors owing to their high sensitivity, good selectivity, and ease of operation [8]. Most previous studies on this subject invovled the use of enzymes which can accelerate the electron transfer between the electrodes and H2O2 [9,10]. To construct enzyme-based sensors, a wealth of nanomaterials such as biopolymers, nanostructures, and sol-gel matrices are also employed to immobilize the enzymes and at the same time, to reduce the possibility of protein denaturing [11–14]. However, their application is limited because enzymes are expensive and easily denatured [15]. This issue was subsequently circumvented by using nanostructures such as noble metal nanoparticles, carbon nanotubes, and reduced graphene oxide as catalysts to calatyze the oxidation or reduction of H2O2 [16–19], leading to enzymeless H2O2 sensors. Furthermore, the electrochemical behavior and kinetic analysis of H2O2 reduction on Ag nanoparticles (AgNPs) have also been evaluated by Compton and co-workers [20,21].
⁎ Corresponding author. E-mail address: [email protected] (X. Sun). 1388-2481/$ – see front matter © 2011 Elsevier B.V. All rights reserved. doi:10.1016/j.elecom.2011.05.002
In this communication, we report on the preparation of AgNPdecorated polypyrrole colloids (AgNP-PPyCs) by heating a AgNO3 aqueous solution and pre-formed PPy colloids solution in the absence of any external reducing agent. It is found that such AgNP-PPyCs exhibit remarkable catalytic performance toward the reduction of H2O2. This enzymeless H2O2 sensor exhibited a fast amperometric response time of less than 2 s and the corresponding linear range and detection limit was estimated to be from 0.1 mM to 90 mM (r = 0.998) and 1.05 μM, respectively, at a signal-to-noise ratio of 3. 2. Experimental 2.1. Reagents and materials All chemicals were purchased from Aladin Ltd. (Shanghai, China), and used as received without further purification. The water used throughout all experiments was purified through a Millipore system. Phosphate buffer saline (PBS) was prepared by mixing stock solutions of NaH2PO4 and Na2HPO4 and a fresh solution of H2O2 was prepared daily. 2.2. Preparation of H2O2 sensor PPy colloids were synthesized according to a reported method [22]. In a typical preparation experiment, to 12 mL of deionized water 0.02 g of ferrous chloride (FeCl2) was added with stirring, where 0.2 mL of pyrrole has been pre-dispersed. After addition of 1 mL of H2O2 to the pyrrole/FeCl2/H2O mixture, pyrrole polymerization was initiated and lasted for overnight. Finally, the dark precipitated PPy colloids were centrifuged and further washed with deionized water
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X. Qin et al. / Electrochemistry Communications 13 (2011) 785–787
and acetone for three times respectively. The powder was then redispersed in 5 mL of deionized water. To prepare AgNP-PPyCs, 20 μL of 0.1 M AgNO3 aqueous solution was added into the aforementioned PPy colloids, and then the resulting solution was heated at 90 °C for 60 min to give dark precipitate which was washed with distilled water several times and then dispersed in water for characterization and future use. 2.3. Characterization of physical properties Scanning electron microscopy (SEM) measurements were made on a XL30 ESEM FEG scanning electron microscope at an accelerating applied potential of 20 kV. The sample for SEM characterization was prepared by place a drop of the dispersion on a bare indium tin oxide coated glass substrate (ITO) and air-dried at room temperature. 2.4. Electrode preparation and electrochemical measurements Electrochemical measurements were performed with a CHI 660D electrochemical analyzer (CH Instruments, Inc., Shanghai). A conventional three-electrode cell was used, including a glassy carbon electrode (GCE, geometric area = 0.07 cm 2) as the working electrode, a Ag/AgCl (3 M KCl) electrode as the reference electrode, and platinum foil as the counter electrode. All potentials given in this work were referred to the Ag/AgCl electrode. All the experiments were carried out at ambient temperature. The suspension of AgNPPPyCs was dropped onto the pre-polished mirror like surface of GCE, chitosan was used as fixative to form a strong film to modify the electrode. 3. Results and discussion Fig. 1A shows low magnification SEM image of as-prepared PPy products, which clearly indicates that they consist exclusively of a large amount of submicrometer-scale particles. Higher magnification
Fig. 1. (A) Low and (B) high magnification SEM images and (C) the corresponding EDS of the PPy colloids.
Fig. 2. (A) Low and (B) high magnification SEM images and (C) the corresponding EDS of the PPy colloids after their incubation with a AgNO3 aqueous solution.
SEM image shown in Fig. 1B reveals that these particles are spherical in shape and well-separated from each other and have diameters ranging from 300 to 400 nm. The chemical composition of these colloids was determined by energy-dispersed spectrum (EDS) (Fig. 1C). The peaks of C and N are observed, indicating that the particles are formed from pyrrole. The observation of the peak of Cl element can be attributed to the fact that the polymerization of pyrrole by FeCl2 yields positively charged PPy structures and thus Cl as counter ions diffuse into the colloids for charge compensation. Other peaks originate from the ITO-coated glass substrate. All the above observations indicate the successful formation of PPy colloids. We further found that the preformed PPy colloids can reduce Ag + into metallic Ag in our present study. Fig. 2A shows low SEM image of the PPy colloids after their incubation with a AgNO3 aqueous solution, indicating that many white dots are observed on the surface of PPy colloid. High magnification SEM image shown in Fig. 2B reveals that
Fig. 3. Cyclic voltammetries (CVs) of bare GCE, PPyC/GCE, AgNP/GCE and AgNP-PPyC/ GCE in 0.2 M PBS at pH 6.5 in the presence of 1.0 mM H2O2 (scan rate: 20 mV/s).
X. Qin et al. / Electrochemistry Communications 13 (2011) 785–787
787
than for AgNP/GCE can result form a larger capacitance of double electric layer of the rougher surface of AgNP-PPyC/GCE [26]. Fig. 4 shows typical current–time plot of the AgNP-PPyC/GCE in N2-saturated 0.2 M PBS buffer (pH: 6.5) on consecutive step change of H2O2 concentrations. When an aliquot of H2O2 was dropped into the stirring PBS solution, the reduction current rose steeply to reach a stable value. The sensor could accomplish 95% of the steady state current within 2 s, indicating a fast amperometric response behavior. It is apparently seen that the steps showed in Fig. 4 are more horizontal in the region of lower concentration of H2O2 and the noises become higher with increased concentration of H2O2. Inset a shows the calibration curve of the sensor, and the low concentration part of this line is shown in inset b. The linear detection range is estimated to be from 0.1 mM to 90 mM (r = 0.998), and the detection limit is estimated to be 1.05 μM at a signal-to-noise ratio of 3. 4. Conclusions Fig. 4. Typical steady-state response of the AgNP-PPyC/GCE to successive injection of H2O2 into the stirred N2-saturated 0.2 M PBS at pH 6.5. Inset: the calibration curve (Applied potential: − 0.30 V).
these dots are about tens of nanometer in size. The chemical composition of the composites was determined by EDS (Fig. 2C). Compared with Fig. 1C, one additional intensive peak of Ag element is found, indicating that the nanoparticles are AgNPs. It should be noted that the PPy colloids still retain both the size and the morphology after the redox process, revealing their robust nature. The formation of such AgNP-PPyCs in our present study may be attributed to that the PPy colloids can effectively adsorb Ag(I) ions via coordination of their imino groups in the PPy chains to Ag(I) ions and then reduce in situ the as-adsorbed Ag(I) ions to form AgNPs [23]. In order to demonstrate the sensing application of such AgNPPPyCs, an enzymeless H2O2 sensor was constructed by deposition of the composites on a GCE surface (AgNP-PPyC/GCE). The PPy colloidmodified GCE (PPyC/GCE) was also similarly prepared. Fig. 3 shows the electrocatalytic responses of these electrodes toward the reduction of H2O2 in N2-saturated 0.2 M PBS at pH 6.5. In the presence of 1.0 mM H2O2, the AgNP-PPyC/GCE exhibits a remarkable catalytic reduction current peak about 49 μA centered at −0.40 V vs Ag/AgCl. However, the responses of both the bare GCE and PPyC/GCE toward the reduction of H2O2 are very weak. These observations indicate that the AgNPs supported on the PPyC exhibit excellent catalytic performance toward H2O2 reduction, and the observation of large catalytic current could be attributed to the large amount of AgNPs existing on the surface of the PPyC. Compared to the responses of citrate-protected AgNP-modified GCE (AgNP/GCE), the AgNP-PPyC/ GCE toward the reduction of H2O2 exhibits a 0.20 V positive shift of the peak potential. It can be attributed to the changed mass transport [20] and the existence of porosity in the AgNP-PPyC/GCE surface [24,25]. Although mass transport and electrode kinetics are known to vary significantly with particle size and surface coverage, both the size and surface coverage of citrate-protected AgNPs and AgNPs on PPyC are not the same and thus a fair comparison is hard to make at present time. A significantly more background current for AgNP-PPyC/GCE
In summary, heat-treatment of a AgNO3 aqueous solution and preformed PPy colloids solution has been proven to be an effective strategy to prepare AgNP-PPyCs. Most importantly, these AgNP-PPyCs are found to exhibit good catalytic activity toward H2O2 reduction. Our observations are significant for the following two reasons: (1) it is the first demonstration of using AgNP-PPyCs for enzymeless H2O2 detection; (2) it provides us a general methodology for the fabrication of noble metal nanoparticle-decorated PPy colloids for applications. References [1] [2] [3] [4] [5] [6] [7] [8] [9] [10] [11] [12] [13] [14] [15] [16] [17] [18] [19] [20] [21] [22] [23] [24] [25] [26]
N.V. Klassen, D. Marchington, H.C.E. McGovan, Anal. Chem. 66 (1994) 2921. M.C.Y. Chang, A. Pralle, E.Y. Isacoff, C.J. Chang, J. Am. Chem. Soc. 126 (2004) 15392. B. Wang, J. Zhang, Z. Pan, X. Tao, H. Wang, Biosens. Bioelectron. 24 (2009) 1141. Y. Song, L. Wang, C. Ren, G. Zhu, Z. Li, Sens. Actuators B 114 (2006) 1001. P.A. Tanner, A.Y.S. Wong, Anal. Chim. Acta 370 (1998) 279. R. Dringen, L. Kussmaul, B. Hampreeht, Brain Research Protocols 2 (1998) 223. T.C. Carmine, G. Bruchelt, T. Hahn, D. Niethammer, J. Biolumin. Chemilumin. 9 (1994) 267. M.N. Bui, X. Pham, K.N. Han, C.A. Li, Y.S. Kim, G.H. Seong, Sen. Actuators B 150 (2010) 436. L. Wang, E. Wang, Electrochem. Commun. 6 (2004) 225. Z. Cao, X. Jiang, Q. Xie, S. Yao, Biosens. Bioeletron. 24 (2008) 222. D. Shan, S. Wang, H. Xue, S. Cosnier, Electrochem. Commun. 9 (2007) 529. J. Wang, M. Musameh, Anal. Chem. 75 (2003) 2075. O. Nadzhafova, M. Etienne, A. Walcarius, Electrochem. Commun. 9 (2007) 1189. C. Shan, H. Yang, J. Song, D. Han, A. Ivaska, L. Niu, Anal. Chem. 81 (2009) 2378. X. Kang, J. Wang, H. Wu, I.A. Aksay, J. Liu, Y. Lin, Biosens. Bioelectron. 25 (2009) 901. C.M. Welch, C.E. Banks, A.O. Simm, R.G. Compton, Anal. Bioanal. Chem. 382 (2005) 12. Y. Li, J. Zhang, J. Xuan, L. Jiang, J. Zhu, Electrochem. Commun. 12 (2010) 777. J. Tian, S. Liu, X. Sun, Langmuir 26 (2010) 15112. S. Liu, J. Tian, L. Wang, H. Li, Y. Zhang, X. Sun, Macromolecules 43 (2010) 10078. F.W. Campbell, S.R. Belding, R. Raron, L. Xiao, R.G. Compton, J. Phys. Chem. C 113 (2009) 9053. S.R. Belding, F.W. Campbell, E.J.F. Dickinson, R.G. Compton, Phys. Chem. Chem. Phys. 12 (2010) 11208. Z. Liu, Y. Liu, S. Poyraz, X.Y. Zhang, Electrochem. Commun. 47 (2011) 4421. C. Zhao, Q. Zhao, Q. Zhao, J. Qiu, C. Zhu, S. Guo, J. Photochem. Photobiol. A 187 (2007) 146. I. Streeter, G.G. Wildgoose, L. Shao, R.G. Compton, Sensors and Actuators B 133 (2008) 462. X. Dai, G.G. Wildgoose, C. Salter, A. Crossley, R.G. Compton, Anal. Chem. 78 (2006) 6102. A.J. Bard, L.R. Faulkner, Electrochemical Methods, Fundamentals and Applications, E-Publishing, Inc. John Wiley & Sons, 2001, pp. 9–18.