synthesis and characterization of novel ferromagnetic ppy-based nanocomposite

Synthesis and characterization of novel ferromagnetic PPy-based nanocomposite Jing Jiang a, ⁎ , Chaochao Chen c , Lun-Hong Ai a , Liang-Chao Li b, ⁎ , Hui Liu b a Laboratory of Applied Chemistry and Pollution Control Technology, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002, China b Department of Chemistry, Zhejiang Normal University, Jinhua 321004, China c Department of Property Management, China West Normal University, Nanchong 637002, China abstractarticle info Article history: Received 4 October 2008 Accepted 18 November 2008 Available online 24 November 2008 Keywords: Nanomaterials Magnetic materials Polypyrrole(PPy) Magnetic property Polypyrrole(PPy)/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite was prepared by a simple, general and inexpensive in situ polymerization of pyrrole in the presence of Zn 0.5 Cu 0.5 Fe 2 O 4 nanoparticles in w/o microemulsion. The effects of PPy coating on the magnetic properties of Zn 0.5 Cu 0.5 Fe 2 O 4 were investigated. By means of X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, scanning electron microscopy (SEM) and vibrating sample magnetometer (VSM) technique, the microstructure and magnetic property of samples were characterized. The SEM analysis indicated that PPy was deposited on the porous surface of Zn 0.5 Cu 0.5 Fe 2 O 4 . The results were shown that the magnetic parameters such as saturation magnetization and coercivity of Zn 0.5 Cu 0.5 Fe 2 O 4 decreased upon PPy coating. © 2008 Elsevier B.V. All rights reserved. 1. Introduction Inherently conducting polymers are attractive materials, as they cover a wide range of functions from insulators to metals and retain the mechani cal prope rti e s of conventio na l polymer s [1,2].The considerable electrochemical and physicochemical properties result in conducting polymers having various practical applications, such as corrosion protection coatings, electro-catalysts, chemical sensors, rechargeable batteries, and light-emitting diodes (LEDs) [3–7]. Among the conducting polymer, polypyrrole (PPy) has received a great deal of attention in recent years due to its easy synthesis, good environmental stability, and high electrical conductivity [8]. Organic–inorganic nanocomposites with an organized structure provide a new functional hybrid between organic and inorganic materials. In recent years, conducting polymer-based composites containing magnetic nanoparticles are of special interesting due to their unique electromagnetic properties and potential applications in several important technological fields such as electrochromic device, electromagnetic interference shielding, and non-linear optical sys- tems [9]. Up to the present, several groups have done much work on synthesizing magnetic PPy-based nanocomposites. Deng et al. have studied the synthesis of magnetic and conducting Fe 3 O 4 -polypyrrole nanoparticles with core–shell structure by using sodium dodecylben- zenesulfonate (NaDS) as a surfactant and dopant [10]. Wang et al. have reported an ultrasonic irradiation approach to prepare polypyrrole (PPY)/Fe 3 O 4 magnetic nanocomposite which can solve the problem in the dispersion and stabilization of inorganic nanoparticles in polymer [11]. Spinel magnetic ferrite has been intensively investigated due to their remarkable magnetic and electrical properties and wide practical applications in ferrofluids, magnetic drug delivery, magnetic high- density information storage [12,13]. Therefore, it is very inter- esting in preparing PPy composites containing magnetic ferrite nanoparticles. To our best knowledge, spinel Zn 0.5 Cu 0.5 Fe 2 O 4 ferrite- PPy nanocomposite system has not been reported yet. Herein, we developed the water-in-oil (w/o) microemulsion process and first prepared the PPy–Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite with ferromagnetic behavior. This approach provides a simple, general and inexpensive method for the preparation of PPy–ferrite nanocomposite. 2. Experimental Zn 0.5 Cu 0.5 Fe 2 O 4 nanoparticles were prepared by a citrate sol–gel combustion process. The typical procedure was described in our previous study [14]. The synthesis of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocom- posite was simply achieved via a microemulsion route. A quaternary microemuls ion, Triton X-100/water/cyclohexane/ n-butanol was selected for this study. In a typical procedure, 10 mL Triton X-100 was added to 5 mL 0.1 mol L − 1 HCl solution, then 1 mL n-butanol and 50 mL cyclohexane were introduced. The mixture was stirred and the system became transparent immediately; thus, a clear and transpar- ent microemulsion system was obtained. A certain amount o f Zn 0.5 Cu 0.5 Fe 2 O 4 particles were added into the homogeneous solution and sonicated for 1 h. 1 mL pyrrole monomer was added to the suspension and stirred for 30 min. 5 m L deionized water containing 3.51 g ammonium persulfate was then slowly added dropwise to the Materials Letters 63 (2009) 560–562 ⁎ Corresponding author. Tel.: +86 817 2568081; fax: +86 817 2582029. E-mail address: 0826zjjh@163.com (J. Jiang). 0167-577X/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2008.11.031 Contents lists available at ScienceDirect Materials Letters journal homepage: www.elsevier.com/locate/matlet well-stirred reaction mixture. The reaction was carried out at 0 °C under nitrogen while stirring for 8 h. The nanocomposite was obtained by filtering and washing the suspension with methanol, and dried under vacuum at 60 °C for 24 h. The X-ray diffraction (XRD) patterns of the samples were collected on a X-ray diffractometer with Cu Kα radiation. Infrared spectra were recorded on a Brucker Equinox 55 FT-IR spectrometer in the range of 400–40 00 cm − 1 using K Br pellets. The SEM micrographs were obtained on a Hitachi S4800 scanning electron microscope. SEM measurements were mounted on aluminum studs using adhesive graphite tape and sputter coated with gold before analysis. Magnetic measurements were carried out at room temperature using a vibrating sample magnetometer (VSM) with a maximum magnetic field of 10 kOe. 3. Results and discussions The structures of the PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite were investigated by FTIR spectroscopy and X-ray diffraction. FTIR spectra of the PPy and PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite are shown in Fig. 1. All characteristic peaks of PPy, the C=C backbone stretching at 1545 cm − 1 , C–C stretching modes at 1 463 cm − 1 [15 ],C–Hin-planedeformation vibrat ion at 1302 and 10 53 cm − 1 ,C–N stretching vibration at 1190 cm − 1 , the in-plane deformation vibration of NH + which is formed on the PPy chains by protonation at 11 0 1 cm − 1 [16],C–H out-of-plane ring de- formation vibration at 795 cm − 1 and the C–C out-of-plane ring defor- mation vibration at 617 cm − 1 canbeobserved.AsshowninFig. 1b, FTIR spectra of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite are almost identical to that of PPy. Due to the higher mass of the participating atoms, vibrations of transitional metal–oxy gen bonds appear in the far-infrar ed region, characteristic peaks of the ferritecannotbeexpectedinthepresent spectral pattern [17]. Fig. 2 shows the XRD patterns of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocompo- site. It can be observed that the broad amorphous diffraction peak centred at around 2θ = 23° in the XRD curves of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 Fig. 1. FTIR spectra of PPy (a) and PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite (b). Fig. 2. XRD patterns of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite (a) and the reference standard data for Zn 0.5 Cu 0.5 Fe 2 O 4 of the JCPDS file No. 77-0012 (b). Fig. 3. SEM micrographsof Zn 0.5 Cu 0.5 Fe 2 O 4 (a) and PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite (b). Fig. 4. Magnetization curves of Zn 0.5 Cu 0.5 Fe 2 O 4 (a) and PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite (b); the inset of the figure shows magnetization curves at low field. 561J. Jiang et al. / Materials Letters 63 (2009) 560–562 nanocomposite, corresponding to the scattering from bare polymer chains at the interplanar spacing of protonated PPy [18], in addition, another six diffraction peaks at 2θ = 30.1°, 35.4°, 43.1°, 53.5°, 57.0° and 62.6° assigned to scattering from (220), (311), (400), (422), (511) and (440) planes of the spinel Zn 0.5 Cu 0.5 Fe 2 O 4 are consistent with the reported data (JCPDS card No. 77-0012), which confirms the presence of Zn 0.5 Cu 0.5 Fe 2 O 4 in the PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite. Fig. 3a shows the SEM micrograph of the as-burnt Zn 0.5 Cu 0.5 Fe 2 O 4 powders synthesized by a self-propagating combustion method, indicating a characteristic of porous surface, formed by the escaping gases during the combustion process [19]. Fig. 3b shows the SEM micrograph of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite, suggesting that PPy is deposited on the porous surface of Zn 0.5 Cu 0.5 Fe 2 O 4 . Fig. 4 shows the magnetic hysteresis loops of Zn 0.5 Cu 0.5 Fe 2 O 4 and PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite at room temperature. It can be observed that the saturation magnetization of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocompos ite is lower t han th at of Zn 0.5 Cu 0.5 Fe 2 O 4 , due to the diamagnetic PPy contribution to the total magnetization [20]. Magnetic properties observed for materials are a combination of many anisotropy mechanisms, such a s magnetocrysta lline anisotropy, surface anisotropy and interparticles interactions. For the PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite system, PPy coating may decrease the surface anisotropy of Zn 0.5 Cu 0.5 Fe 2 O 4 and increase the interpar- ticle distances which will lead to weakening interparticle interaction [21,22], hence, the decrease in coercivity of Zn 0.5 Cu 0.5 Fe 2 O 4 after PPy coating is expected. In order to investigate the effects of preparation route on the magnetic properties of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocompo- site, a contrast experiment was carried out in aqueous solution. The resulted sample also shows the magnetic hysteretic behavior and a similar value of saturation magnetization, however, the coercivity, which is related to the microstructure, is larger than that of the sample obtained by w/o microemulsion route (Table 1), indicating that Zn 0.5 Cu 0.5 Fe 2 O 4 nanoparticles are more homogeneously embedded in PPy matrix by w/o microemulsion route. 4. Conclusions In summary, the ferromagnetic PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocompo- site was successfully synthesized via in-situ polymerization of pyrrole in the presence of Zn 0.5 Cu 0.5 Fe 2 O 4 nanoparticles inw/omicroemulsion. Zn 0.5 Cu 0.5 Fe 2 O 4 nanoparticles were obtained by a citrate sol–gel combustion method. It was shown that the saturation magnetization and coercivity of Zn 0.5 Cu 0.5 Fe 2 O 4 nanoparticles decreased upon PPy coating, which can be attributed to the diamagnetic PPy contribution to the magnetic properties. Acknowledgement This work was supported by Scientific Research Start-up Founda- tion of China West Normal University (07B008). References [1] Kang ET, Neoh KG, Tan KL. Prog Polym Sci 1998;23:277–324. [2] Heeger AJ. Synth Met 2002;125:23–42. [3] Ahmad N, MacDiarmid AG. Synth Met 1996;78:103–10. [4] Ficicoglu F, Kadirgan F. J Electroanal Chem 1998;451:95–9. [5] Kan JQ, Pan XH, Chen C. Biosens Bioelectron 2004;19:1635–40. [6] Kuwabata S, Masui S, Yoneyama H. Electrochim Acta 1999;44:4593–600. [7] Wang HL, MacDiarmid AG, Wang YZ, Gebler DD, Epstein AJ. Synth Met 1996;78:33–7. [8] Skotheim TA, Elsenbaumer R, Reynolds JR. Handbook of Conducting Polymers. New York: Marcel Dekker; 1998. [9] Alam J, Riaz U, Ahmad S. J Magn Magn Mater 2007;314:93–9. 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Table 1 Magnetic parameters of PPy/Zn 0.5 Cu 0.5 Fe 2 O 4 nanocomposite synthesized by different r oute Preparation route Saturation magnetization (emu/g) Coercivity (Oe) W/o microemulsion route 1.56 20.9 Aqueous solution process 1.49 28.2 562 J. Jiang et al. / Materials Letters 63 (2009) 560–562 . Synthesis and characterization of novel ferromagnetic PPy-based nanocomposite Jing Jiang a, ⁎ , Chaochao Chen c ,. done much work on synthesizing magnetic PPy-based nanocomposites. Deng et al. have studied the synthesis of magnetic and conducting Fe 3 O 4 -polypyrrole nanoparticles