Elsevier

Solid State Communications

Volume 129, Issue 8, February 2004, Pages 485-490
Solid State Communications

Synthesis of magnetite nanorods and porous hematite nanorods

https://doi.org/10.1016/j.ssc.2003.11.043Get rights and content

Abstract

Fe3O4 nanorods with average diameters of 40–50 nm and lengths of up to 1 μm were synthesized through hydrolysis of FeCl3 and FeSO4 solutions containing urea in the temperature range from 90 to 95 °C in reflux condition for 12 h, following an aging time of 12 h. The porous hematite nanorods were prepared by calcination of the precursor which was obtained from hydrolysis of FeCl3 and FeSO4 solutions containing urea at a temperature of 90 °C for 10 h in hydrothermal condition. The formation of the porosity of hematite was due to the decomposition of FeCO3 and FeOOH. Urea played a key role in the formation of the iron oxide nanorods. Transmission electron microscopy (TEM) images showed that the morphology of magnetite particles is homogeneous in the shape of rods and hematite rods are full of porosity. The values of saturation magnetization (M) and coercivity (H) of magnetite nanorods are 67.55 emu/g and 114 Oe, respectively. The samples were also characterized by X-ray powder diffraction (XRD) and electron diffraction (ED). At last, the forming mechanism of both the magnetite and porous hematite nanorods was discussed.

Introduction

One-dimensional (1D) materials (nanowires, nanotubes, nanobelts, and nanoribbons) have been the focus of considerable interest because of their fundamental importance and potential applications in areas such as nanodevices. As for magnetic materials, the focus is still on the fabrication of monodispersed magnetic particles, which can be controlled in size, distribution, shape, crystalline and alignment [1]. Up to date, magnetic nanoparticles have established their wide applications. These magnetic particles can be made so small that each particle becomes a single domain [2], exhibiting abnormal magnetic properties, known as superparamagnetism [3]. Superparamagnetic particles have been widely studied and used in biomedicine and biotechnology as contrast agent in magnetic resonance imaging (MRI) and as drug carriers for magnetically guided drug delivery [4]. Many such superparamagnetic particles are metal ones which are not stable at room temperature and easily oxidized. Then their potential applications are greatly limited. On the contrary the corresponding metal oxides can overcome the limit and develop the applications further. In addition, the metal oxides are relatively inert and their magnetic properties can be controlled by controlling the size and shape through chemical synthesis [5]. Of all the metal oxides, Fe3O4 and Fe2O3 have aroused great interest in the magnetic material field. Magnetite is of great interest for potential applications, such as pigment [6], recording materials [7], photocatalysis [8], ferrofluid technology and magnetocaloric refrigeration [9], etc. Hematite is widely used as catalysts [10], pigments [11], sensor [12] and the raw material for the synthesis of γ-Fe2O3 (maghemite), which is of great importance as a ferrofluid and magnetic recording materials. While former researches were not mainly concentrated on the synthesis of 1D iron oxides [13], [14], [15], [16], [17], [18], [19], [20], [21], [22]. There are several methods reported of the synthesis of Fe3O4 nanoparticles, e.g. reduction of hematite by CO/CO2 [13] or H2 [14], co-precipitation from the solution of ferrous/ferric mixed salt solution in alkaline medium followed by aging and digestion in the temperature range of 90–150 °C [15], chemical synthesis [16] microwave hydrothermal synthesis [17] and discharge [18]. On the other hand, monodispersed hematite particles with different size and shape have been prepared by Matijevic and co-workers [19]. Kallay and Fischer [20], Hamada and co-workers [21], and Sugimoto et al. [22] have prepared hematite particles of different shape and size by sol–gel method. Naono et al. have reported porous α-Fe2O3 nanocrystals, which were obtained through topotactic dehydroxylation of lath-like goethite crystals [23], [24]. L.A. Pérez-Maqueda et al. used constant rate thermal analysis (CRTA) to synthesize acicular particles of α-Fe2O3 with controlled porosity oriented along the c-lattice axis [25]. Little work has been pursued for 1D magnetite [26], [27], then there will be great significance in synthesizing 1D magnetite. A. Gedanken and co-workers had prepared magnetite nanorods by sonication of aqueous iron (II) acetate in the presence of β-cyclodextrin [26]. But their final product contained ∼1.4% of element C. This was due to the β-cyclodextrin. Our group reported the synthesis of Fe3O4 nanorods using polyethylene glycol-1000 as template [27]. Traditionally the formation of porous hematite nanorods was based on the dehydroxylation of goethite [23], [24], while in this communication, the formation of the porosity is based on decomposition of FeCO3. Here we successfully synthesized Fe3O4 nanorods and porous Fe2O3 nanorods with urea as precipitator in the absence of any surfactant. This procedure has an advantage that it will lead to a homogeneous precipitation and no surfactant need to be removed.

Section snippets

Experimental

All chemicals used in this work were analytical reagent grade from commercial market without further purification. The X-ray powder diffraction analysis was conducted on a Rigaku D/max-IIB X-ray Diffractometer at a scanning rate of 4 degree per minute with 2θ ranging from 5 to 100°, using Cu Kα radiation (λ=1.5418Å). JEM-2010 transmission electron microscope at 200 kV was employed to examine the morphology of the nanorods. Samples were prepared by placing drops of diluted ethanol dispersed of

Results and discussion

The magnetite nanorods have been synthesized by hydrolysis of Fe2+and Fe3+solution in the presence of urea at 90 °C for 12 h. Fig. 1 is the XRD pattern of the sample, which is quite identical to pure magnetite and matched well that of it (JCPDS No. 82-1533), indicating that the sample has a cubic crystal system. No characteristic peaks of impurities are observed. The actual particle size was measured by TEM image. Fig. 2(a) and (b) are the typical images of magnetite nanorods, from which we can

Conclusion

In summary, magnetic Fe3O4 nanorods were successfully synthesized through hydrolysis of FeCl3 and FeSO4 solutions containing urea at 90–95 °C for 12 h, following an aging time under reflux conditions. In hydrothermal condition, with the same reactants, rod-like Fe3O4/Fe2O3/FeCO3/FeOOH nanocomposite and then porous Fe2O3 nanorods were obtained. In this communication, we mainly control the decomposing speed of urea through controlling the temperature, leading to homogeneous precipitation to get

Acknowledgements

This work was financially supported by the National Natural Science Foundation of China (20171010).

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