Synthesis and characterization of maghemite nanopowders by chemical precipitation method
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In this study, nanoparticles of maghemite (γ-Fe2O3) with a mean particle size of 9 nm have been prepared by chemical precipitation method through one step. According to the high-resolution X-ray diffraction result, the as-synthesized iron oxide nanoparticles were γ-Fe2O3. The particle size of the maghemite nanoparticles was below 20 nm confirmed by transmission electron microscopy image. The particle shape was almost a sphere confirmed by transmission electron microscope.
KeywordsIron oxide nanoparticles Maghemite Chemical precipitation
Iron oxides exist in different forms in nature, magnetite, maghemite, and hematite  Maghemite is ferrimagnetic at room temperature but maghemite nanoparticles smaller than 10 nm are superparamagnetic at room temperature, maghemite is unstable at high temperatures, and loses its susceptibility with time [2, 3].
Among the researchers working in the field of nanotechnology, magnetic nanoparticles have attracted intense experimental activities because of their potential applications in a numerous different industries such as storage of information , ferrofluid , audio and video recording , bioprocess  gas sensor [8, 9, 10, 11, 12, 13], refrigeration systems , information storage , medical applications , magnetic resonance imaging , catalyst [18, 19], magnetooptic , and removal of heavy metals [38, 39].
We have various chemistry methods for iron oxide nanoparticles preparation, including gas phase methods (reduction, hydrolysis, disproportionation, oxidation, or other reactions to precipitate solid products from the gas phase), that depend on thermal decomposition , liquid phase methods, two-phase methods, sol–gel methods, high-pressure hydrothermal methods , various methods have been reported for the synthesis of maghemite nanoparticles, such as co-precipitation [23, 24, 25], sol–gel synthesis [26, 27, 28], micro emulsion , flow injection synthesis , hydrothermal synthesis [31, 32], flame spray pyrolysis , decomposition of organic precursors at high temperatures, and the oxidation of magnetite nanoparticles [31, 34].
Among various chemical methods for synthesis of different types of metal oxides, co-precipitation process has several advantages over other methods including, good homogeneity, low cost, high purity of product and not requiring organic solvents and heat treatment. Recently, co-precipitation method has been developed for preparation of magnetite nanoparticles using metallorganic precursors. In this paper, we report the synthesis and characterization of the γ-Fe2O3 nanoparticles by a chemical co-precipitation technique of ferric and ferrous ions. In this method, unlike previous methods of producing maghemite nanoparticles, we do not need expensive equipments, organic solvents and Hydrochloric acid which is a corrosive substance in the industry and create corrosion in equipment. Also, production time, compared with the previous method is faster and has the ability to produce on an industrial scale.
To prepare Iron oxide nanoparticles, especially maghemite (γ-Fe2O3), ferric chloride (FeCl3, 99 %), ferrous chloride tetra hydrate (FeCl2·4H2O, 98 %), hydrochloric acid (HCl, 37 %), ammonium hydroxide (NH4OH, 25–30 % of ammonia), de-ionized water, and ethanol (CH3CH2OH, 99.93 %) were used in the experiments. All the reagents used were of analytical grade. The synthesis was as follows:
FeCl3 and FeCl2·4H2O were dissolved in a 2 M hydrochloric acid to form a solution with the concentration of 1 M for FeCl3 and 2 M for FeCl2·4H2O. The NH3·H2O solution (0.8 M) was dropped to this solution with vigorous stirring at room temperature for 80 min. The final pH was 8.7.
FeCl3 and FeCl2·4H2O were dissolved in a de-ionized water to form a solution with the concentration of 1 M for FeCl3 and 2 M for FeCl2·4H2O. The NH3·H2O solution (0.8 M) was dropped to this solution with vigorous stirring at room temperature for 40 min. The final pH was 8.3.
The brown precipitate was then collected by filtration and rinsed three times with deionized water and ethanol. Finally, the washed precipitate was dried at room temperature.
The crystallographic structure of the as-synthesized iron oxide nanoparticles was characterized by high-resolution XRD analysis (Philips, X, pert-MPD) using Cu Kα (λ = 1.54 Å) radiation and the crystallite size was estimated using Scherrer’s formula.
IR spectra were recorded on a Bruker tensor 27 FTIR spectrometer with RTDLATGS detector, in the range of 400–4,000 cm−1 with a spectral resolution of 4 cm−1 in transmittance mode. The surface morphology of the powders was observed by the TEM (CM-120 PW6031/10). The magnetic properties of the as-synthesized nanopowders were analyzed by a vibrating sample magnetometer (VSM), in the Development Center of Kashan University (Kashan, Iran).
Results and discussion
In summary, γ-Fe2O3 nanoparticles have been prepared by chemical precipitation method at room temperature. The procedure in the present study offers very important advantageous features for preparation of maghemite nanoparticles. The synthetic process is economical, able to control the size of nanoparticles and production scale up and do not need heating stage and complex equipment. The XRD patterns indicated that as-synthesized iron oxide nanoparticles were maghemite. According to the TEM image, the particle size was around 9 nm, and particle shape was almost a sphere. The saturation magnetization of the iron oxide nanopowders was 50 emu g−1.
Conflict of interest
The authors declare that they have no competing interests.
MS proposed the study, carried out the experiments, performed the statistical analysis, revised, drafted manuscript, and financially supported the project. NG helped to revised, draft the manuscript. HM carried out the experiments and to draft the manuscript and MMM carried out the experiments and to draft the manuscript. All authors read and approved the final manuscript.
- 6.Kiemle, P., Wiese, J., Buxbaum, G.: Process for the production of iron oxides epitaxially coated with cobalt, the coated oxides and their cue. US Patent No. 652214Google Scholar
- 15.Sinha, A., Chakraborty, J., Rao, V.: Process for preparing nanosized acicular magnetic maghemite phase iron oxide particles. European Patent EP1559118Google Scholar
- 18.Rostovshchikova, T.N., Kiseleva, O.I., Smirnov, V.V., Maksimov, Y.V., Suzdalev, I.P., Prusakov, V.E., Tsodikov, M.V., Ikorskiid, V.N.: Catalytic conversions of chloroolefines over iron oxide nanoparticles 3. Electronic and magnetic properties of γ-Fe2O3 nanoparticles immobilized on different silicas. Russ. Chem. Bull. Int. 55, 1768–1774 (2006)Google Scholar
- 21.Pierson, H.O.: Handbook of Chemical Vapor Deposition: Principles, Technology, and Applications. William Andrew Inc (1999)Google Scholar
- 25.Layek, S., Pandey, A., Pandey, A., Verma, H.C.: Synthesis of γ-Fe2O3 nanoparticles with crystallographic and magnetic texture. Int. J. Eng. Sci. Technol. 2(8), 33–39 (2010)Google Scholar
- 29.Chin, A.B., Yaacob, I.I.: Synthesis and characterization of magnetic iron oxide nanoparticles via w/o microemulsion and Massart's procedure. J. Mater. Process. Technol. 191, 235–237 (2007)Google Scholar
- 32.Islam, M.S., Kurawaki, J., Kusumoto, Y., Abdulla-Al-Mamuna, M., Bin Mukhlish, M.Z.: Hydrothermal novel synthesis of neck-structured hyperthermia-suitable magnetic (Fe3O4, γ-Fe2O3 and α-Fe2O3) nanoparticles. J. Sci. Res. 4(1), 99–107 (2012)Google Scholar
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