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December 24, 2001
Volume 79, Number 52
CENEAR 79 52 p. 9
ISSN 0009-2347
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A Better Recipe For -Fe2O3 Nanocrystallites


A promising new method for the synthesis of highly crystalline, uniformly sized maghemite (-Fe2O3) nanoparticles has been devised by researchers in South Korea [J. Am. Chem. Soc., 123, 12798 (2001)].

Such magnetic nanoparticles are of interest for a host of applications, including medical imaging and drug delivery.

Although relatively uniform maghemite and magnetite nanoparticles have been synthesized recently by other groups, time-consuming size-selection procedures were necessary. Not so with the new method, according to Taeghwan Hyeon, an assistant professor of chemical engineering at Seoul National University.

Hyeon and his coworkers first prepare uniformly sized iron nanoparticles by decomposing Fe(CO)5 in octyl ether in the presence of oleic acid (a stabilizing agent) at 100 ºC and then aging the iron oleate complex at 300 ºC. Next, the iron particles are oxidized to -Fe2O3 nanocrystallites (shown) using trimethylamine oxide [(CH3)3NO], a mild oxidant. By adjusting reaction parameters, the researchers can "tune" the size of the -Fe2O3 particles from 4 to 16 nm. Particles 13 nm in size can also be made in a single step using a variation of the procedure.

Hyeon foresees using the process to prepare multikilogram quantities of nanoparticles.

Chemist Christopher B. Murray's team at IBM Watson Research Center in Yorktown Heights, N.Y., has tried the new synthesis, and Murray says "it works beautifully." The high quality, crystallinity, and uniformity of the particles are "pretty compelling," he tells C&EN. Murray thinks the method "will be rapidly adopted as a new standard" for the preparation of -Fe2O3 nanoparticles.

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