Thin Solid Films 519 (2011) 8277–8279

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Thin Solid Films

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A facile route to sonochemical synthesis of magnetic iron oxide (Fe3O4) nanoparticles

Md. Nazrul Islam, Le Van Phong, Jong-Ryul Jeong, CheolGi Kim ⁎

Department of Materials Science and Engineering, Chungnam National University, Daejeon 305-764, Korea

⁎ Corresponding author. Tel.: +82 42 821 6632; fax:E-mail address: cgkim@cnu.ac.kr (C.G. Kim).

0040-6090/$ – see front matter © 2011 Elsevier B.V. Aldoi:10.1016/j.tsf.2011.03.108

a b s t r a c t

a r t i c l e i n f o

Available online 6 April 2011

Keywords:SonochemistryMonodispersitySuperparamagnetism

A facile sonochemical approach was applied for the large scale synthesis of iron oxide magnetic nanoparticles(NPs) using inexpensive and non-toxic metal salts as reactants. The as-prepared magnetic iron oxide NPs hasbeen characterized by XRD, TEM, EDS, and VSM. X-ray diffraction (XRD) and EDS analysis revealed that Fe3O4

NPs have been successfully synthesized in a single reaction by this simple method. Transmission electronmicroscopy (TEM) data demonstrated that the particles were narrow range in size distribution with 11 nmaverage particle size. Moreover, TEM measurements also show that the synthesized nanoparticles are almostspherical in shape. The magnetization curve from vibrating sample magnetometer (VSM) measurementshows that as-synthesized NPs were nearly superparamagnetic in magnetic properties with very lowcoercivity, and magnetization values were 80 emu/g, which is very near to the bulk value of iron oxide. Theestimated value of mass susceptibility of as-synthesized nanoparticles is Xg=5.71×10−4 m3/kg.

+82 42 822 6272.

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© 2011 Elsevier B.V. All rights reserved.

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1. Introduction

During the past decade, growing development in the synthesis ofnanoparticles obtainmuch interest due to its tremendous prospects invarious sides. This growing interest is not only for its elementaryscientific values but also environmental remediation [1–5] andbiomedical applications, such as magnetic resonance imaging (MRI)[6–10], cell and protein separation [11–14], and drug delivery [15], aswell as ever-increasing technological applications such as theirtunable magnetic properties [16–18] and their wide use in catalysis[19], magnetic recording [20], high performance electromagnetic [21]and spintronic devices [22]. It is essential to have large amounts ofmagnetic nanoparticles stably dispersed in water for these diverseecological and biomedical applications. Iron oxide nanoparticlescan be synthesized by thermal decomposition of iron acetylacetonatein 2-pyrrolidone, dispersible in water; these materials could be poorlycrystalline and/or polydisperse [16,19]. Recently, high temperatureorganic solution phase methods developed for the synthesis of mono-disperse semiconductor quantum dots have been used to improvematerial quality for iron oxide systems with encouraging results.

In this study, we report a new facile synthetic route for thepreparation of superparamagnetic monodisperse Fe3O4 NPs bysonochemical method using inexpensive and non-toxic metal saltsas reactants. By optimizing the preparation conditions such asconcentration of ammonia and reaction time, we have successfullysynthesized monodisperse Fe3O4 NPs with the average size of 11 nm,

which implies that the modified sonochemical method could be agood candidate to prevent toxicity problems in typical sonochemicalsynthesis process. Superparamagnetic nature of the nanoparticles wasobserved by measuring magnetic hysteresis loop using vibratingsample magnetometer (VSM). It is revealed from X-ray diffraction(XRD) and transmission electron microscopy (TEM) results that theas-synthesized nanoparticles have small size distribution and mod-erate monodispersity in both polar and nonpolar solvents. Further-more, the single crystalline behavior of the as-prepared nanoparticleswas confirmed from TEM observation.

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Fig. 3. The magnetization curves of the Fe3O4 NPs measured at room temperature.

8278 M. Nazrul Islam et al. / Thin Solid Films 519 (2011) 8277–8279

2. Experimental procedure

The NPs synthesis was carried out under an ambient temperature.Analytical reagent grade chemicals were used without further puri-fication. Prepared mixture of 2.81 g FeCl3∙6H2O (99%, Aldrich) and

Fig. 4. TEM images of NPs (a) and Fe3O4 NPs (

1.72 g FeCl2∙4H2O (90%, Aldrich) in 100 ml distilled H2Owas sonicatedfor 30 min.

The ultrasonic processor (Vibra Cell-VCF 1500, Sonics andMaterials) with a maximum power of 1500 W generating capacitywas used in this experiment. The sonoreactor was equipped with atitanium horn having 5 cm2 of irradiating surface area and piezoelec-tric transducer supplied by a 20 kHz generator. Then mixture wassonicated in ultrasonic processor for 75 min. Ammonia (15 ml) wasinjected in the reaction vessel after 15 min of starting of ultrasonica-tion. Finally, the obtained mixture was washed with distilled waterand ethanol for several times and dried in a vacuum evaporator.

The crystal structure of the synthesized NPs was analyzed using anXRD system (Rigaku, D/MAX-RC, Cu Kα radiation and a Ni filter). Themagnetic properties were characterized by means of a LakeShore7400 series vibrating sample magnetometer (VSM) at room temper-ature. The size of the synthesized NPs was characterized using atypical transmission electron microscopy (TEM, Technai F-20, oper-ated at 200 kV). The size distributions of the particles were measuredfrom enlarged TEM images.

3. Results and discussion

The XRD patterns of the sample (Fig. 1) shows that the peaks canbe indexed to (220), (311), (400), (422), (511), (440) and (533)planes of a cubic unit cell of Fe3O4 based on the comparison with thestandard pattern of Fe3O4 (JCPDS card no. 79-0418). The results of EDSanalysis are shown in Fig. 2. When the EDS intensity factors are takeninto accounts, the NPs contained 78.5% by atomic ratio of iron (Fe) and21.5% by atomic ratio of oxygen (O), which can be assumed that theobtained nanoparticles were Fe3O4 NPs.

To investigate themagnetic properties of theNPs, room temperaturemagnetization measurements have been carried out by using a VSM inan externalmagnetic field range between−13 kOe and+13 kOe. Fig. 3shows the M–H hysteresis loops for the sample. The hysteresis loopsreveal that the as-synthesized NPs have very low Hc, 10 Oe, which isnear to superparamagnetic behavior. The magnetization value at themaximum applied field was 80 emu/g. Magnetic susceptibility of as-synthesized NPs has also been calculated. From the calculation, it isrevealed that the as-synthesized NPs have high susceptibility. Theestimated mass susceptibility is Xg=5.71×10−4 m3/kg.

Fig. 4(a–b) shows the TEM images of Fe3O4 NPs. The averageparticles size of the sample was estimated to be about 11 nm. It is alsorevealed that as-synthesized iron oxide NPs were round in shape. Thesize and morphology of the particles were analyzed from TEM images

b). Single Fe3O4 NP is spherical in shape.

Fig. 5. The particle size distributions diagram for the sample.

8279M. Nazrul Islam et al. / Thin Solid Films 519 (2011) 8277–8279

and summarized in Fig. 5 as the size distribution diagram. Based onthe size distribution information, it is clear that the size of as-preparedFe3O4 NPs has the relatively narrow range in particles size distribution.

4. Conclusion

In conclusion, we have developed a simplistic sonochemicalmethod to synthesize the Fe3O4 NPs which have been successfullysynthesized using inexpensive and non-toxic metal salts as reactants.X-ray diffraction (XRD) and EDS patterns shows that there is anevident characteristic of magnetite phase (Fe3O4). It is also notewor-thy that Transmission electron microscopy (TEM) measurementsrevealed that the as NPs prepared have size distribution in relativelynarrow range and moderate monodispersity. We believe that thismethod can provide an easy and fast synthetic route to synthesizeFe3O4 nanoparticles for bio and as well as many further applications.

Acknowledgements

This researchwas supported by a grant from the Fundamental R&DProgram for Core Technology of Materials funded by the Ministry ofKnowledge Economy, and by the converging research center programthrough the ministry of Education, Science and Technology(2010K001070), Republic of Korea.

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