Monodisperse magnetic nanoparticles: Effects of surfactants on the reaction between iron acetylacetonate and platinum acetylacetonate
K. Chokprasombatª, C. Sirisathitkula,*, P. Hardingª, S. Chandarakb, and R. Yimnirunb
ª Molecular Research Unit, School of Science, Walailak University, Nakhon Si Thammarat 80161,Thailand.*e-mail: schitnar@wu.ac.th
b School of Physics, Institute of Science, Suranaree University of Technology and Synchrotron Light Research Institute (Public Organization), Nakhon Ratchasima 30000, Thailand, Tel: +66-75-672-945
]]> Received 16 October 2012;
Abstract
Magnetic properties of monodisperse nanoparticles for ultrahigh density recording and biomedical applications are sensitive to their shape and size distributions. These attributes are, in turns, dictated by several parameters during the synthesis and heat treatments. In this work, monodisperse FePt-based magnetic nanoparticles around 5 nm in diameter were synthesized by the reaction between iron acetylacetonate (Fe(acac)3) and platinum acetylacetonate (Pt(acac)2) in benzyl ether. X-ray absorption near-edge structure (XANES) spectra agreed with transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (EDS) that as-synthesized nanoparticles were composed of Pt-rich nuclei and iron oxides. Whereas their composition and size was not sensitive to the variation in the amount of surfactants (oleic acid and oleylamine), the nanoparticles exhibited a larger variation in shape with the increase in each surfactant from 1.5 to 4.5 mmol. After annealing in argon atmosphere at 650°C for 1 hour, the nanoparticles tended to agglomerate. Higher amounts of surfactants surrounded the nanoparticles apparently allowed more sintering because the decomposed carbon from the excess surfactants facilitated the reduction ofiron oxides. More Fe in the large annealed particles then resulted in ferromagnetic properties. By contrast, the ferromagnetic behavior and the highest coercivity were obtained without such agglomeration in the case ofannealed particles synthesized by using the minimum surfactants.
Keywords: Magnetic nanoparticles; Modified polyol process; Oleic acid; Oleylamine.
PACS: 75.75.-c; 75.50.Bb
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]]>Acknowledgements
This work is financially supported by the National Electronics and Computer Technology Center, National Science and Technology Development Agency and Industry/University Cooperative Research Center (I/UCRC) in HDD Component, the Faculty of Engineering, Khon Kaen University with approval of Seagate Technology (Thailand). The authors would like to thank Dr. P. Jantaratana of Kasetsart University for providing VSM facility.
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