synthesis and characterization of novel ferromagnetic ppy-based nanocomposite

* Laboratory of Applied Chemistry and Pollution Control Technology, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002, China > Department of C

CAS ye te `

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Contents lists available at ScienceDirect

Materials Letters

materials letters

Synthesis and characterization of novel ferromagnetic PPy-based nanocomposite

Jing Jiang **, Chaochao Chen ‘, Lun-Hong Ai ?, Liang-Chao Li>*, Hui Liu?

* Laboratory of Applied Chemistry and Pollution Control Technology, College of Chemistry and Chemical Engineering, China West Normal University, Nanchong 637002, China

> Department of Chemistry, Zhejiang Normal University, Jinhua 321004, China

© Department of Property Management, China West Normal University, Nanchong 637002, China

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)/Zngs5Culp;Fe,04, nanocomposite was prepared by a simple, general and inexpensive in situ polymerization of pyrrole in the presence of Zng s;Cug5Fe,0, nanoparticles in w/o microemulsion The effects

of PPy coating on the magnetic properties of Znp.5;Cup5Fe20,4 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 Zng,5CUp 5Fe204 The results were shown that the magnetic parameters such as saturation magnetization and coercivity of Zng5Cug5Fe,04 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 mechanical properties of conventional polymers [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 Fe30,4-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)/Fe30, magnetic nanocomposite which can solve the problem in

* 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

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 Zng.5Cup.5Fe20, 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—Zng 5Cug ;5Fe204 nanocomposite with ferromagnetic behavior This approach provides a simple, general and inexpensive method for the preparation of PPy-ferrite nanocomposite

2 Experimental ZNo.5Cup.s5Fe204 nanoparticles were prepared by a citrate sol-gel combustion process The typical procedure was described in our previous study [14] The synthesis of PPy/Zng 5Cug 5Fe20, nanocom- posite was simply achieved via a microemulsion route A quaternary microemulsion, 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”! HCI 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 of ZNg5Cup5Fe20, 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 mL deionized water containing 3.51 g ammonium persulfate was then slowly added dropwise to the

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Fig 1 FTIR spectra of PPy (a) and PPy/Znp.5;Cug.5Fe204, nanocomposite (b)

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 Ka radiation Infrared spectra were

recorded on a Brucker Equinox 55 FT-IR spectrometer in the range of

400-4000 cm”! using KBr pellets The SEM micrographs were

obtained on a Hitachi $4800 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/Zno5Cugs5Fe20, nanocomposite were

investigated by FTIR spectroscopy and X-ray diffraction FTIR spectra of

the PPy and PPy/Znp5Cug5Fe20, nanocomposite are shown in Fig 1

All characteristic peaks of PPy, the C=C backbone stretching at 1545 cm Ì,

C-C stretching modes at 1463 cm! [15], C-H in-plane deformation

vibration at 1302 and 1053 cm !, C-N stretching vibration at 1190 cm},

(311) 300¬

200

100-

2Theta (degree)

Fig 2 XRD patterns of PPy/Zno,5Cug.5Fe20, nanocomposite (a) and the reference

standard data for Zno,5Cuo.5Fe20,4 of the JCPDS file No 77-0012 (b)

Fig 3 SEM micrographs of Zng.5Cug,5Fe20, (a) and PPy/Zng.5Cug5Fe20,4 nanocomposite (b)

the in-plane deformation vibration of NH” which is formed on the PPy chains by protonation at 1101 cm‘! [16], C-H out-of-plane ring de- formation vibration at 795 cm! and the C-C out-of-plane ring defor- mation vibration at 617 cm”! can be observed As shown in Fig 1b, FTIR spectra of PPy/Zng5Cug5Fe,0, nanocomposite are almost identical to that

of PPy Due to the higher mass of the participating atoms, vibrations of transitional metal-oxygen bonds appear in the far-infrared region, characteristic peaks of the ferrite cannot be expected in the present spectral pattern [17]

Fig 2 shows the XRD patterns of PPy/Zng 5Cup.5Fe204 nanocompo- site It can be observed that the broad amorphous diffraction peak centred at around 26=23° in the XRD curves of PPy/Zng5Cug5Fe204

2

J

=

Ñ œœœxx A 0.4 | po

-1 0 - -200 -100 0 100 200)

H (Oe)

Fig 4 Magnetization curves of Zng s;Cug5Fe20,4(a) and PPy/Zng5Cug5Fe20, nanocomposite (b); the inset of the figure shows magnetization curves at low field.

Table 1

Magnetic parameters of PPy/Zng5Cug5Fe.0, nanocomposite synthesized by different route

Preparation route Saturation magnetization (emu/g) Coercivity (Oe)

Aqueous solution process 1.49 28.2

nanocomposite, corresponding to the scattering from bare polymer

chains at the interplanar spacing of protonated PPy [18], in addition,

another six diffraction peaks at 20=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 Zngs5Cup5Fe20,4 are consistent with the

reported data (JCPDS card No 77-0012), which confirms the presence

of Znp.5Cug 5Fe204 in the PPy/Zng 5Cup 5Fe204 nanocomposite

Fig 3a shows the SEM micrograph of the as-burnt Zng5Cup 5Fe204

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/Zng5Cugs5Fe.0, nanocomposite, suggesting that

PPy is deposited on the porous surface of Zno 5Cug5Fe204

Fig 4 shows the magnetic hysteresis loops of Zng 5Cug 5Fe20,4 and

PPy/Zng5Cugs5Fe204, nanocomposite at room temperature It can be

observed that the saturation magnetization of PPy/Zng5Cug5Fe204

nanocomposite is lower than that of Zng5Cug5Fe204, due to

the diamagnetic PPy contribution to the total magnetization [20]

Magnetic properties observed for materials are a combination

of many anisotropy mechanisms, such as magnetocrystalline

anisotropy, surface anisotropy and interparticles interactions For the

PPy/Zng5Cug5Fe204 nanocomposite system, PPy coating may decrease

the surface anisotropy of Zno.5Cugs5Fe20O,4 and increase the interpar-

ticle distances which will lead to weakening interparticle interaction

[21,22], hence, the decrease in coercivity of Znp.5Cup5Fe20,4 after PPy

coating is expected In order to investigate the effects of preparation

route on the magnetic properties of PPy/Znp 5Cug 5Fe204 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

ZNg5Cup5Fe20,4 nanoparticles are more homogeneously embedded in PPy matrix by w/o microemulsion route

4 Conclusions

In summary, the ferromagnetic PPy/Znp 5Cug 5Fe204, nanocompo- site was successfully synthesized via in-situ polymerization of pyrrole

in the presence of Zno sCuo sFeazÒa nanoparticles in w/o microemulsion ZnosCuo sFezOx nanoparticles were obtained by a citrate sol-gel combustion method It was shown that the saturation magnetization and coercivity of Zno 5Cug5Fe,0, 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)

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