Facile synthesis of water-soluble and superparamagnetic Fe 3 O 4 dots through a polyol-hydrolysis route
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Facile synthesis of water-soluble and superparamagnetic Fe3O4 dots through a polyol-hydrolysis route Pin Jiang • Xi Yang • Ying Xin • Yongxin Qi Xicheng Ma • Qian Li • Zhaoliang Zhang
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Received: 3 August 2012 / Accepted: 5 November 2012 / Published online: 27 November 2012 Ó Springer Science+Business Media New York 2012
Abstract Monodisperse Fe3O4 dots with a mean size of about 2.3 nm were successfully synthesized via a polyolhydrolysis route without adding any dispersant. Inorganic iron nitrate was used as the metal source and triethylene glycol (TEG) was used as the polyol solvent. The Fe3O4 dots were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), selective area electron diffraction (SAED), Fourier transform infrared (FTIR) spectroscopy, N2 adsorption–desorption, and magnetization measurements. The as-synthesized Fe3O4 dots can not only be coagulated from the polyol by ethanol and acetone, but also easily redispersed in water by ultrasonication, resulting in a clear Tyndall effect. The obtained Fe3O4 dots exhibited superparamagnetism at room temperature and the saturation magnetization is much lower than those reported in previous works. The formation mechanism of the Fe3O4 dots was proposed to be the hydrolysis of iron nitrates and subsequent dehydration and partial reduction of Fe3? to Fe2? at elevated temperatures in TEG.
Electronic supplementary material The online version of this article (doi:10.1007/s10853-012-7018-6) contains supplementary material, which is available to authorized users. P. Jiang X. Yang Y. Xin Q. Li Z. Zhang (&) School of Chemistry and Chemical Engineering, University of Jinan, 106 Jiwei Road, Jinan 250022, China e-mail: [email protected] Y. Qi School of Material Science and Technology, Shandong University, Jinan 250100, China X. Ma School of Chemistry and Chemical Engineering, Shandong University, Jinan 250100, China
Introduction Superparamagnetic Fe3O4 nanoparticles offer potential applications in magnetic nanofluids [1], catalysts [2], bioseparation [3], drug delivery [4], and magnetic resonance imaging contrast agents [5]. Consequently, major efforts have been devoted to the synthesis of Fe3O4 nanoparticles, including the coprecipitation of ferrous (Fe2?) and ferric (Fe3?) ions [6], the hydrothermal route [7], micro-emulsions [8], the solvothermal process [9, 10], high-temperature organic phase decomposition [11], thermal decomposition of alkaline solution of Fe3? chelate in the presence of hydrazine [12], and sonochemical decomposition of hydrolyzed ferrous salt [13]. However, many of these methods need expensive starting materials, complicated procedures, and toxic solvents. Therefore, developing a facile method for synthesizing superparamagnetic Fe3O4 is of importance and still a challenge for researchers. The polyol process is a versatile chemical approach, which has successfully been used to prepare a great variety of inorganic non-aggregated particles [14, 15]. The polyols in this method often serve as high-boiling solvents an
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