Electrocatalytic oxidation of hydrazine at glassy carbon electrode modified with ethylenediamine cellulose immobilized palladium nanoparticles

Journal of Electroanalytical Chemistry 690 (2013) 96–103

Contents lists available at SciVerse ScienceDirect

Journal of Electroanalytical Chemistry journal homepage: www.elsevier.com/locate/jelechem

Electrocatalytic oxidation of hydrazine at glassy carbon electrode modified with ethylenediamine cellulose immobilized palladium nanoparticles Hamid Ahmar, Sajjad Keshipour, Hadi Hosseini, Ali Reza Fakhari ⇑, Ahmad Shaabani ⇑, Akbar Bagheri Department of Chemistry, Faculty of Sciences, Shahid Beheshti University, GC, P.O. Box 19839-4716, Tehran, Islamic Republic of Iran

a r t i c l e

i n f o

Article history: Received 13 July 2012 Received in revised form 10 November 2012 Accepted 24 November 2012 Available online 21 December 2012 Keywords: Pd nanoparticles Cellulose Supported catalysis Electrocatalysis Electrochemical sensor

a b s t r a c t We report herein the fabrication of a novel electrochemical sensor based on palladium nanoparticles immobilized on ethylenediamine cellulose which is consisted of uniformly distributed palladium nanoparticles with the main average size of 4.7–6.9 nm. The structure of the prepared nanocomposite was investigated by X-ray powder diffraction, transmission electron microscopy and thermogravimetric analysis techniques. The prepared catalyst was immobilized on the surface of glassy carbon electrode using drop casting method to fabricate an electrochemical sensor toward hydrazine. The modified electrode showed good catalytic activity for the electrooxidation of hydrazine (pH = 7.0), with a substantial decrease in anodic overpotentials (850 mV) and an increase in anodic peak current (about 4 times) in comparison with the unmodified electrode. A linear relationship was observed between the differential pulse voltammetry currents and the concentration of hydrazine within the range of 5–150 lM with the detection limit (S/N = 3) of 1.5 lM. The diffusion coefficient (D = 2.3  105 cm2 s1) was calculated for hydrazine, using chronoamperometry. Ó 2012 Elsevier B.V. All rights reserved.

1. Introduction Fabrication of chemically modified electrodes is an important branch of electrochemical sciences [1,2]. The main purpose of modifying the electrodes is improving the facility of electron transfer between the electroactive species and the electrodes (electrocatalysis). Due to unique properties such as, high electrocatalytic activity, high surface area, strong stability, good electrical and mechanical properties, and chemical inertness, metal nanoparticles, especially noble metal nanoparticles have attracted considerable attention in the preparation of modified electrodes [3–5]. Using effective supports for the preparation of metal nanoparticles based electrocatalytic systems has some advantages such as high loading level, long-term stability, good dispersion, controlled particle size and morphology of the attached nanoparticles [6]. Generally, the electrocatalytic activity of metal nanoparticles evidently depends on the nature, generation, size and kind of the functional groups available on the support. Platinum-group metals are common catalysts in many chemical and electrochemical reactions. Palladium (Pd) is one of them, which possesses their special properties for catalytic applications and electrode modification processes [7]. Pd nanoparticles (PdNPs) show strong catalytic activity towards electrooxidation of some

⇑ Corresponding authors. Tel.: +98 21 22431661; fax: +98 21 22431683. E-mail addresses: [email protected] (A.R. Fakhari), [email protected] (A. Shaabani). 1572-6657/$ - see front matter Ó 2012 Elsevier B.V. All rights reserved. http://dx.doi.org/10.1016/j.jelechem.2012.11.031

important organic species such as hydrazine [8], oxalic acid [9], glucose [10], and methanol [11]. Recently, a great deal of effort has been made for the synthesis and stabilization of PdNPs on various supports in order to use them in electroanalysis. For example conducting polymers [12], dendrimers [13] sol–gel materials [14], multi walled carbon nanotubes [15], single walled carbon nanotubes [10,16] and graphene [17] have been reported as a support for preparing PdNPs based electrocatalysts. Among these systems, the application of polymer-supported PdNPs for electrocatalysis purposes has attracted much more attention due to the porous structure and high surface area of polymers and the possibility of high dispersion of metallic nanoparticles into the polymers [12,18,19]. Cellulose is a biopolymer with so many unique properties such as high chemical purity, porous structure, large surface area, good hydrophilicity and biocompatibility and also its low cost. Therefore, cellulose and its derivatives could be used as an ideal support for metal nanoparticles with the aim of catalysis and electrocatalysis [20–24]. In this context, some reports about the application of cellulose as a support for PdNPs in catalytic organic reactions have been published [21–23]. Recently, the use of cellulose derivatives and their composites as supports for the preparation of electrochemical sensors has increased. The majority of these works are using these materials as a support for the immobilization of biomolecules such as enzyme, protein and DNA [24–32]. Although, some other works have reported the use of cellulose derivatives as a support for organic or inorganic molecules with the aim of

H. Ahmar et al. / Journal of Electroanalytical Chemistry 690 (2013) 96–103

electrochemical sensing [33–35], to the best of our knowledge, there are no reports on the electrocatalytic applications of PdNPs immobilized on cellulose derivatives. Hydrazine is widely used in different industries as a reducing agent, emulsifier, catalyst, corrosion inhibitor, photographic chemical, explosive, and rocket propellants. But it is known to be harmful for human life. Hydrazine is volatile, toxic, and is readily absorbed by oral, dermal, or inhalation routes of exposure. Acute exposure can also damage liver, kidney, and central nervous system [36]. We believed that, functionalization of cellulose with a complexation agent such as ethylenediamine could improve the dispersing and stability of PdNPs and therefore could improving the electrocatalytic efficiency. In this work, cellulose was functionalized with ethylenediamine and then used as a support for the preparation of PdNPs immobilized on ethylenediamine cellulose (PdNPs–EDAC). Finally, electrocatalytic activity of a PdNPs–EDAC has been investigated for the oxidation of hydrazine as an important model compound. 2. Experimental 2.1. Chemicals All solvents and reagents were purchased from Aldrich or Merck and were used without further purification. All solutions were prepared with double distilled water. 2.2. Apparatus All electrochemical measurements were carried out on a lAutolab potentiostat/galvanostat type III (Eco Chemie, Netherlands) coupled with a conventional three-electrode cell. The three-electrode cell consisted of an Ag|AgCl|KCl (saturated) as the reference electrode, a Pt wire as the counter electrode and a bare glassy carbon electrode with a diameter of 2 mm (modified and unmodified) as working electrode. All of the employed electrodes were purchased from Azar Electrode (I.R. Iran). Transmission electron microscopy (TEM) analyzes were performed by Philips CM30 electron microscope. Thermogravimetric analysis (TGA) was carried out using STA 1500 instrument under air and a heating rate of 10 °C min1. X-ray diffraction patterns were obtained on a XD-3A diffractometer with Cu Ka radiation. Pd determinations were carried out on an FAAS (Shimadzu model AA-680 atomic absorption spectrometer) with a Pd hollow cathode lamp at 242.8 nm, using an air–acetylene flame. 2.3. Synthesis of PdNPs–EDAC In a typical procedure, 2.0 g cellulose was added to a 21 mL solution of N,N-dimethylformamide (DMF) and LiCl (0.05 g) and was stirred for 5 h. Then, the solution was treated with 8 mmol tosylchloride and 0.1 mL triethylamine and stirring continued for 24 h at 8 °C to obtain cellulose tosylate [37]. 9 mL water was added slowly, followed by 9 mmol of ethylenediamine. The temperature was raised to 100 °C and the reaction mixture was stirred for 16 h. After cooling down to room temperature the mixture was poured into 60 mL acetone. The polymer was filtrated off and washed three times with acetone. It was dried under vacuum at 60 °C to afford ethylenediamine cellulose (EDAC) [38]. Then, 2.0 g EDAC was added to a 3 mL solution of PdCl2 (1.1 mmol) in water. The mixture was stirred at room temperature, after 24 h, 5 mL of NaBH4 solution (1.5 mmol) was added to the mixture during 5 h. Finally the mixture was filtered off, and the residue was washed successively with water (3  25 mL) and CH3CN (3  25 mL) and

97

was dried under vacuum at 80 °C to give the PdNPs–EDAC with 7.3 wt% Pd loading. Thus, a heterogeneous catalytic system was obtained containing PdNPs with the main average size of 4.7–6.9 nm on the surface of EDAC. 2.4. Preparation of glassy carbon electrode modified with palladium nanoparticles immobilized on ethylenediamine cellulose (PdNPs– EDAC/GCE) Suspension of the catalyst was prepared by dispersing 10 mg of PdNPs–EDAC hybrid material in 10 mL DMF using ultrasonic agitation to obtain a relatively stable suspension. Prior to use, the glassy carbon electrode (GCE) was carefully polished with 0.05 lM alumina slurry on a polishing cloth, then it was washed in an ultrasonic bath of methanol and water, respectively. The cleaned GCE was coated by 10 lL of the black suspension of PdNPs–EDAC and was dried at room temperature. Also the suspension of EDAC was prepared and used for the fabrication of EDAC/GCE with the same procedure for comparison. The effective surface area of the PdNPs–EDAC/GCE was estimated from the cyclic voltammograms of a 0.5 mM K3[Fe(CN)6] solution at various scan rates. For a reversible process, the Randles–Sevcik formula was used [39].

Ip ¼ 2:69  105 n3=2 ACD1=2 m1=2 where Ip refers to the anodic peak current, n the number of electrons transferred, A the surface area of the electrode, D the diffusion coefficient, C the concentration of K3[Fe(CN)6], and m is the scan rate. For 0.5 mM K3[Fe(CN)6] in the 0.1 M KNO3 electrolyte: n = 1 and D = 7.6  106 cm2 s1 [40–42], then from the slope of Ip versus m1/ 2 , the effective area was calculated to be 0.054 cm2. 2.5. Analytical procedure The PdNPs–EDAC/GCE was first activated in the blank solution (phosphate buffer solution, pH 7.0) by cyclic voltammetric sweeps between 0.5 and +1.0 V versus Ag|AgCl|KCl (saturated), until stable cyclic voltammograms were obtained. Then the electrode was used for the oxidation of hydrazine in phosphate buffer solution, pH 7.0. For comparison, GCE and EDAC/GCE were used applying the same procedure. All measurements were carried out at room temperature. 3. Results and discussion 3.1. Characterization of PdNPs–EDAC X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA) methods have been used for the characterization of PdNPs–EDAC. Fig. 1 shows the TEM images of the EDAC (Fig. 1A) and PdNPs– EDAC (Fig. 1B). It can be seen that small PdNPs with the particle size within the range of 4.7–6.9 nm were highly dispersed on the PdNPs–EDAC. In addition, XRPD patterns illustrated (data not shown) characteristic diffraction peak at 2h = 38.94 for PdNPs– EDAC particles, which indicates good loading level of PdNPs. Thermogravimetric analysis (data not shown) evidenced that EDAC is of good thermal stability (dec. > 304) under inert atmosphere that is comparable and even better than cellulose (dec. > 290). So, introducing ethylenediamine into the cellulose structure improved its thermal behavior. Thermogravimetric analysis of PdNPs–EDAC shows that this compound was decomposed at less temperature (240 °C) than the EDAC and cellulose which it is probably due to the catalytic activity of Pd on degradation of organic compounds [43].

98

H. Ahmar et al. / Journal of Electroanalytical Chemistry 690 (2013) 96–103

Fig. 1. TEM pictures of (A) EDAC and (B) PdNPs–EDAC.

3.2. Electrochemical behavior of the PdNPs–EDAC/GCE 3.2.1. Cyclic voltammetry of PdNPs–EDAC/GCE Fig. 2 shows the cyclic voltammograms of PdNPs–EDAC/GCE and EDAC/GCE in phosphate buffer solution (pH 7.0). As shown in curve A, EDAC/GCE does not exhibit any electrochemical response in the applied potential window while in the case of PdNPs–EDAC/GCE (Fig. 2, curves B and C) significant oxidative and reductive currents were observed. The well-defined redox couple at 0.25 V and 0.75 V is related to desorption and adsorption of proton on the surface of the modified electrode. Also, broad oxidation peak above +0.40 V corresponds with the metal oxide formation and the cathodic peak at +0.01 V is related to the reduction of palladium oxide and regeneration of the catalyst. In this Figure, curve C is related to the electrochemical behavior of PdNPs–EDAC/GCE in the closed potential range that has been used for further studies. In this potential range (0.5 to 1.00 V) adsorption and desorption of proton did not occur and some details were observed more clearly.

3.2.2. Influence of sweeping potential window In addition the effect of potential range on the electrochemical behavior of PdNPs–EDAC/GCE has been studied (data not shown). In the same condition, with increasing the switching potential (0.50–1.40 V), reduction peak grows and shifts to negative values. This is probably due to the thickness of palladium oxide and/or

the formation of different crystallographic forms of the oxide with different peak potential values [7,44]. 3.2.3. Influence of scan rate Additionally, the influence of scan rate on the anodic and cathodic peaks of modified electrode has been studied in the range of 10–350 mV s1 (Fig. 3). It was observed that the anodic and cathodic peaks show different behavior. The anodic peak currents are linear with m in lower scan rates but in higher scan rates are linear with m1/2 (Fig 3, curves A and B). On the other hand in lower scan rates, the electrochemical process is controlled by adsorption rather than diffusion while in higher scan rates the diffusion is dominant. Also, cathodic peak currents increased linearly with the square root of scan rate (m1/2) as the scan rate grew from 10 to 350 mV s1 (Fig. 3 curves C and D), indicating a diffusion controlled process. 3.2.4. Influence of pH Finally, the effect of pH has been investigated on the electrochemical behavior of PdNPs–EDAC/GCE. The influence of the electrolyte pH on the electrochemical response of PdNPs–EDAC/GCE was studied using 0.1 mol L1 phosphate buffer at pH range of 3.0–9.0 (Fig. 4). The results showed that anodic and cathodic peak potentials shift to more negative values with increasing pH. In general, according to the previously proposed mechanisms for electrooxi-

Fig. 2. Cyclic voltammograms of (A) EDAC/GCE, (B and C) PdNPs–EDAC/GCE in phosphate buffer (pH = 7.0, C = 0.1 M) solution; scan rate 50 mV s1.

H. Ahmar et al. / Journal of Electroanalytical Chemistry 690 (2013) 96–103

99

Fig. 3. (A) Cyclic voltammograms of PdNPs–EDAC/GCE in phosphate buffer solution (pH = 7.0, C = 0.1 M) at different scan rates (inner to outer): 10, 20, 30, 40, 50, 60, 70, 80, 90, 100, 120, 140, 160, 180, 200, 250, 300 and 350 mV s1, (B) variation of the anodic peak currents versus scan rate, (C) variation of the anodic peak currents versus the square root of scan rate, (D) variation of the cathodic peak currents versus scan rate, (E) variation of the anodic peak currents versus the square root of scan rate.

Fig. 4. Cyclic voltammograms of PdNPs–EDAC/GCE in various pHs (3.0, 4.0, 5.0, 6.0, 7.0, 8.0, and 9.0) of supporting electrolyte solution.

dation of Pd in aqueous solutions [7], H+ is produced and the process becomes dependent on the electrolyte’s pH according to the Pourbaix diagrams [7,45]. 3.3. Electrocatalytic oxidation of hydrazine at PdNPs–EDAC/GCE In order to evaluate the capacity of the PdNPs–EDAC/GCE for electrooxidation of hydrazine, cyclic voltammograms of bare GCE, EDAC/GCE, PdNPs–EDAC/GCE, and PdNPs–cellulose were obtained

in the presence of 50 lM hydrazine (Fig. 5). As shown in this Figure, hydrazine showed a weak and broad oxidation peak on the surface of GCE at 0.80 while its oxidation on EDAC/GCE appeared at 0.65 V along with an increase in current. In the case of PdNPs– EDAC/GCE, oxidation potential decreased to 0.05 V and also the peak current have significantly increased compared to the other mentioned electrodes. Finally, to reveal the role of ethylenediamine on the electrocatalytic properties of PdNPs–EDAC the voltammogram of hydrazine at the surface of PdNPs–cellulose (prepared

100

H. Ahmar et al. / Journal of Electroanalytical Chemistry 690 (2013) 96–103

Fig. 5. Cyclic voltammograms of (A) GCE, (B) EDAC/GCE, (C) PdNPs–EDAC/GCE, (D) PdNPs–cellulose/GCE in the presence of 50 lM hydrazine in phosphate buffer solution (pH = 7.0, C = 0.1 M); scan rate 50 mV s1.

by the same procedure) was recorded (Fig. 5D). As seen, the PdNPs–cellulose shows less catalytic activity toward hydrazine in comparison with PdNPs–EDAC, and it is probably due to the larger size distribution and less effective surface area of PdNPs–cellulose. These results indicate that PdNPs–EDAC exhibits good catalytic performance toward hydrazine oxidation and could efficiently improve the electrochemical performance of the electrode. In general,

the low detection potential and high current response obtained at PdNPs–EDAC was related to the excellent catalytic activity of Pd nanoparticles and the porous structure of PdNPs–EDAC which could facilitate the penetration of hydrazine into the electrode surface [46]. Therefore, ethylenediamine cellulose acted as an efficient supporting material for the effective dispersion of the catalyst (PdNPs).

Fig. 6. (A) Cyclic voltammograms of 50 lM hydrazine on PdNPs–EDAC/GCE in various pHs (3.0, 4.0, 5.0, 6.0, 7.0, 8.0, 9.0 and 10.0) of supporting electrolyte solution, (B) variation of the oxidation peak potential (Ep) and (C) variation of the oxidation peak current (ip) with pH solution; scan rate: 50 mV s1.

H. Ahmar et al. / Journal of Electroanalytical Chemistry 690 (2013) 96–103

3.3.1. Influence of pH The pH value of the electrolyte showed a significant effect on the electrochemical behavior of hydrazine. In general, since hydrazine contains NH2 groups, it was anticipated that the electrochemical behavior of the compound would be pH dependent. The effect of pH on the electrochemical behavior of hydrazine on the surface of the PdNPs–EDAC/GCE electrode is shown in Fig. 6.

101

The slope of the Ep variation as a function of the solution pH (0.062 V/pH units) is close to the Nernstian slope of 0.059 V/pH units at 25 °C and indicates that the number of electrons and protons involved in the electrode process is equal. These results are in a good agreement with an accepted mechanism for hydrazine oxidation [47,48]. Thus, the overall reaction mechanism could be proposed as:

Fig. 7. (A) Cyclic voltammograms of PdNPs–EDAC/GCE in the presence of 50 lM of hydrazine in phosphate buffer solution (pH = 7.0, C = 0.1 M) at different scan rates: 25, 50, 75, 100, 150, 200, 250, 300 and 350 mV s1, (B) variation of the oxidation peak currents versus the square root of scan rate, (C) variation of the Log ip versus Log m.

Fig. 8. Chronoamperometric responses of PdNPs–EDAC/GCE in phosphate buffer solution (pH = 7.0, C = 0.1 M) at a potential step of 250 mV for different concentrations of hydrazine: 10, 60, 110, and 160 lM. Insets: (A) Plots of I versus t1/2 obtained from chronoamperograms, (B) plot of the slope of straight lines against the hydrazine concentration.

102

H. Ahmar et al. / Journal of Electroanalytical Chemistry 690 (2013) 96–103

N2 H4 ! N2 þ 4Hþ þ 4e Also, the results showed that the maximum anodic peak current for hydrazine was obtained in pH 7.0 (Fig 6B). Thus, the optimum pH for further studies was set at 7.0.

3.3.2. Influence of scan rate Cyclic voltammograms of PdNPs–EDAC/GCE in phosphate buffer (pH = 7.0, C = 0.1 M) containing 50 lM of hydrazine at various scan rates (v) were shown in Fig. 7. As seen, the peak currents were proportional to the square root of scan rate from 25 to 350 mV s1 (Fig. 7B), which demonstrated a diffusion controlled redox process. In addition, a linear variation was also obtained for the log of the peak current versus the log of the scan rate corresponding to the following equation: (log ip = 0.447 log v  0.001; R2 = 0.9949). The slope of 0.447 was near to the theoretically expected value of 0.5 for diffusion-controlled process [49].

3.3.3. Chronoamperometry The catalytic oxidation of hydrazine on the surface of PdNPs– EDAC/GCE, was studied by chronoamperometry. Chronoamperometric responses obtained at a potential step of 200 mV were depicted in Fig. 8. For an electroactive material, the current response under diffusion control is described by Cottrell equation [39]:

I ¼ nFACD1=2 p1=2 t 1=2 where D (cm2 s1) and Cb (mol cm3) are the diffusion coefficient and the bulk concentration, respectively. Under diffusion control, a plot of I versus t1/2 will be linear, and the value of D can be determined from the slope. Inset A of Fig. 8 shows the fitted experimental plots of I verses t1/2 for different concentrations of hydrazine. The slopes of the resulting straight line were then plotted versus the hydrazine concentration (inset B of Fig. 8), from its slope diffusion has been obtained 2.3  105 cm2 s1 for hydrazine. The calculated value of diffusion coefficient is in a good agreement with

Fig. 9. (A) DPVs of PdNPs–EDAC/GCE at various concentrations of hydrazine (5, 10, 15, 20, 30, 40, 50, 60, 70, 80, 95, 110, 125, 135 and 150 lM) in phosphate buffer solution (pH = 7.0, C = 0.1 M), (B) peak current as a function of different concentrations.

Table 1 A comparison of the analytical performance of different palladium electrodes for the determination of hydrazine. Electrode a

PdHCF–Al Pd–Tio2b Pd/PANI–PAMPSA/GCEc Pd/CNF–GCEd Pd/BDDe Palladium plated/BDD Pd/BMWCNTsf PdNPsGlCMPs–BPPGg PdNPs–EDAC/GCEh a b c d e f g h

Method

LOD (lM)

Linear range (lM)

Refs.

Amperometry Chronoamperometry Chronoamperometry DPV LSV LSV LSV CV DPV

4.6 23 0.42 2.9 2.6 1.8 10 4 1.5

390–10,000 and 20,000–75,000 1000–20,000 40–1000 10–4000 27.2–85 10–100 56–157 10–300 5–150

[54] [55] [56] [46] [57] [57] [58] [48] This work

Palladium hexacyanoferrate modified aluminum electrode. Nanoporous Pd-modified TiO2 electrode. Palladium-modified polysulfonic acid-doped polyaniline glassy carbon electrode. Palladium nanoparticle/carbon nanofibers modified glassy carbon electrode. Palladium nanoparticles supported on boron-doped diamond electrode. Palladium nanoparticle decorated bamboo multi-walled carbon nanotubes. Pd nanoparticles supported on glassy carbon microspheres basal plane pyrolytic graphite electrode. Glassy carbon electrode modified with ethylenediamine cellulose immobilized palladium nanoparticles.

H. Ahmar et al. / Journal of Electroanalytical Chemistry 690 (2013) 96–103

4.00  105 cm2 s1 [50,51] and 1.4  105 cm2 s1 [52] which were previously reported for hydrazine in literature. 3.4. Analytical performances In order to study the quantitative determination of hydrazine, the DPV responses for the modified electrode were recorded on the addition of varying concentrations of hydrazine (Fig. 9A). Also, Fig. 9B demonstrates that the plot of peak current versus hydrazine concentration (corrected for any residual current of the modified electrode in supporting electrolyte) is linear in the range of 5– 150 lM with the following equation:

Ipa ðlAÞ ¼ 0:0218Cðl mol L1 Þ þ 0:0195 lAðR2 ¼ 0:999Þ The LOD of hydrazine was obtained 1.5 lM based on signal-tonoise method with considering S/N = 3 [53]. In addition, the reproducibility and repeatability of the PdNPs–EDAC/GCE were investigated using cyclic voltammetry. In a series of five modified electrodes all prepared the same way, a relative standard deviation of 8.6% was obtained towards the oxidation current of 50 lM hydrazine, indicating good reproducibility of the method. Also, five different cyclic voltammetry measurements for 50 lM hydrazine using a single electrode (with interval time of 30 min) yield an R.S.D. of 5.1%, indicating good repeatability of the proposed method. Stability of the modified electrode was tested by storing the electrode at room temperature for 2 weeks, thereafter CVs were recorded and compared with the initial CVs. The results indicated that the electrode response retained 92% of its initial value. It revealed that the modified electrode exhibited good stability and reproducibility. A comparison between the analytical performance of proposed electrode and different palladium electrodes for the determination of hydrazine are summarized in Table 1. As seen, the low limit of dynamic linear range of proposed method is lower than mentioned works. Also, LOD and linear dynamic range of proposed electrode are comparable with previous reports. 4. Conclusions In summary, a new electrochemical sensor based on PdNPs– EDAC with unique properties such as well distributed PdNPs, good conductivity, high surface area and low cost was synthesized and characterized successfully. PdNPs–EDAC was applied for the modification of glassy carbon electrode. Voltammetric results showed that the modified electrode had a good catalytic effect towards the electrooxidation of hydrazine, which exhibited an oxidation overpotential that was significantly shifted toward more negative values. The redox process was pH dependent and a higher catalytic current was observed at pH 7.0 in PBS. The results showed that the catalytic peak current of hydrazine was proportional to the concentration over the range of 5–150 lM and the modified electrode exhibited an excellent reproducibility and stability. Acknowledgment Financial support from the Research Affairs of Shahid Beheshti University is gratefully appreciated. References [1] J.-M. Zen, A.S. Kumar, D.M. Tsai, Electroanalysis 15 (2003) 1073–1087. [2] R.C. Alkire, D.M. Kolb, J. Lipkowski, P. Ros, Advances in electrochemical science and engineering, vol. 11, Chemically Modified Electrodes, WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim Germany; 2009. [3] C.M. Welch, R.G. Compton, Anal. Bioanal. Chem. 384 (2006) 601–619. [4] L.G. Shaidarova, G.K. Budnikov, J. Anal. Chem. 63 (2008) 922–942. [5] M. Oyama, Anal. Sci. 26 (2010) 1–12.

103

[6] R.M. Crooks, M. Zhao, L. Sun, V. Chechik, L.K. Yeung, Acc. Chem. Res. 34 (2001) 181–190. [7] M. Grden, M. Lukaszewski, G. Jerkiewicz, A. Czerwinski, Electrochim. Acta 53 (2008) 7583–7598. [8] N. Maleki, A. Safavi, E. Farjami, F. Tajabadi, Anal. Chim. Acta 611 (2008) 151– 155. [9] Y. Liu, J. Huang, D. Wang, H.H.T. You, Anal. Methods 2 (2010) 855–859. [10] L. Meng, J. Jin, G. Yang, T. Lu, H. Zhang, C. Cai, Anal. Chem. 81 (2009) 7271– 7280. [11] J. Zhang, M. Huang, H. Ma, F. Tian, W. Pan, S. Chen, Electrochem. Commun. 9 (2007) 1298–1304. [12] S.K. Kim, Y.N. Jeong, M.S. Ahmed, J.-M. You, H.C. Choi, S. Jeon, Sens. Actuators B – Chem. 153 (2011) 246–251. [13] Y. Shen, Q. Xu, H. Gao, Ni. Zhu, Electrochem. Commun. 11 (2009) 1329–1332. [14] A. Safavi, A.R. Banazadeh, Electroanalysis 23 (2011) 1536–1542. [15] X.M. Chen, Z.J. Lin, D.J. Chen, T.T. Jia, Z.M. Cai, X.R. Wang, X. Chen, G.N. Chen, M. Oyama, Biosens. Bioelectron. 25 (2010) 1803–1808. [16] M.S. Ahmed, H. Jeong, J.M. You, S. Jeon, Electrochim. Acta 56 (2011) 4924– 4929. [17] L.M. Lu, H.B. Li, F. Qu, X.B. Zhang, G.L. Shen, R.Q. Yu, Biosens. Bioelectron. 26 (2011) 3500–3504. [18] L.G. Shaidarova, A.V. Gedmina, I.A. Chelnokova, G.K. Budnikov, J. Anal. Chem. 61 (2006) 601–608. [19] O. Naranchimeg, S.K. Kim, S. Jeon, Bull. Korean Chem. Soc. 32 (2011) 2771– 2775. [20] C.M. Cirtiu, A.F. Dunlop-Briere, A. Moores, Green Chem. 13 (2011) 288–291. [21] K.R. Reddy, N.S. Kumar, P.S. Reddy, B. Sreedhar, M.L. Kantam, J. Mol. Catal. A: Chem. 252 (2006) 12–16. [22] K.R. Reddy, N.S. Kumar, B. Sreedhar, M.L. Kantam, J. Mol. Catal. A: Chem. 252 (2006) 136–141. [23] Y. Xu, L. Zhang, Y.C. Cui, J. Appl. Polym. Sci. 110 (2008) 2996–3000. [24] W. Wang, T.-J. Zhang, D.-W. Zhang, H.-Y. Li, Y.-R. Ma, L.-M. Qi, Y.-L. Zhou, X.-X. Zhang, Talanta 84 (2011) 71–77. [25] W. Wang, H.-Yi. Li, D.-W. Zhang, J. Jiang, Y. Cui, S. Qiu, Y.-L. Zhou, X.-X. Zhang, Electroanalysis 22 (2010) 2543–2550. [26] X. Ren, D. Chen, X. Meng, F. Tang, A. Du, L. Zhang, Colloid Surf. B – Biointerfaces 72 (2009) 188–192. [27] M.A.T. Gilmartin, J.P. Hart, Analyst 119 (1994) 833–840. [28] Y.-M. Li, H.-H. Liu, D.-W. Pang, J. Electroanal. Chem. 574 (2004) 23–31. [29] W. Zheng, Q. Li, L. Su, Y. Yan, J. Zhang, L. Mao, Electroanalysis 18 (2006) 587– 594. [30] H. Huang, P. He, N. Hu, Y. Zeng, Bioelectrochemistry 61 (2003) 29–38. [31] R. Villalonga, A. Fujii, H. Shinohara, S. Tachibana, Y. Asano, Sensor Actuator B – Chem. 129 (2008) 195–199. [32] S. Jia, J. Fei, J. Zhou, X. Chen, J. Meng, Biosens. Bioelectron. 24 (2009) 3049– 3054. [33] S. Wu, J. Liu, X. Bai, W. Tan, Electroanalysis 22 (2010) 1906–1910. [34] A.M. Lazarin, C.A. Borgo, Y. Gushikem, J. Membr. Sci. 221 (2003) 175–184. [35] A.A. Hoffmann, S.L.P. Dias, E.V. Benvenutti, E.C. Lima, F.A. Pavan, J.R. Rodrigues, R. Scotti, E.S. Ribeiro, Y. Gushikem, J. Braz. Chem. Soc. 18 (2007) 1462–1472. [36] N. Nasirizadeh, H.R. Zare, A.R. Fakhari, H. Ahmar, M.R. Ahmadzadeh, A. Naeimi, J. Solid State Electrochem. 15 (2011) 2683–2693. [37] K. Rahn, M. Diamantoglou, H. Berghmans, T. Heinze, Angew. Makromol. Chem. 238 (1996) 143–163. [38] T. Heinze, A. Koschella, L. Magdaleno-Maiza, A.S. Ulrich, Polym. Bull. 46 (2001) 7–13. [39] A.J. Bard, L.R. Faulkner, Electrochemical Methods Fundamentals and Applications, Wiley, New York, 2001. [40] D.L. Compton, J.A. Laszlo, J. Electroanal. Chem. 520 (2002) 71–78. [41] A. Bagheri, H. Hosseini, Bioelectrochemistry 88 (2012) 164–170. [42] R.N. Hegde, B.E.K. Swamy, N.P. Shetti, S.T. Nandibewoor, J. Electroanal. Chem. 635 (2009) 51–57. [43] J.J. Verendel, T.L. Church, P.G. Andersson, Synthesis (2011) 1649–1677. [44] H. Ahmar, A.R. Fakhari, M.R. Nabid, S.J. Tabatabaei Rezaei, Y. Bide, Sensor Actuator B – Chem. 171–172 (2012) 611–618. [45] M. Pourbaix, Atlas of Electrochemical Equilibria in Aqueous Solutions, Pergamon Press, Oxford, 1966. [46] H. Zhang, J. Huang, H. Hou, T. You, Electroanalysis 21 (2009) 1869–1874. [47] A.J. Bard, Anal. Chem. 35 (1963) 1602–1607. [48] R. Baron, B. Sljukic, C. Salter, A. Crossley, R.G. Compton, Electroanalysis 19 (2007) 1062–1068. [49] D.K. Gosser, Cyclic Voltammetry: Simulation and Analysis of Reaction Mechanisms, VCH, New York, 1993. p. 43. [50] B. Wang, X. Cao, J. Electroanal. Chem. 309 (1991) 147–158. [51] L. Niu, T. You, J.Y. Gui, E. Wang, S. Dong, J. Electroanal. Chem. 448 (1998) 79– 86. [52] S. Karp, L. Meites, J. Am. Chem. Soc. 84 (1962) 906–912. [53] ICH harmonized tripartite guidelines, validation of analytical procedures: text and, methodology, Q2 (R1); 2005. [54] H. Razmi, A. Azadbakht, M. Hossaini Sadr, Anal. Sci. 21 (2005) 1317–1323. [55] Q. Yi, F. Niu, W. Yu, Thin Solid Films 519 (2011) 3155–3161. [56] V. Lyutov, V. Tsakova, J. Electroanal. Chem. 661 (2011) 186–191. [57] C. Batchelor-McAuley, C.E. Banks, A.O. Simm, T.G.J. Jones, R.G. Compton, Analyst 131 (2006) 106–110. [58] X. Ji, C.E. Banks, A.F. Holloway, K. Jurkschat, C.A. Thorogood, G.G. Wildgoose, R.G. Compton, Electroanalysis 18 (2006) 2481–2485.