Bidding - the International Association of the Catalysis Societies

C&EN Volume 79, Number 44, p. 22 (October 29, 2001)
Organic sheath protects silver nanowires
Metal nanowires less than a nanometer thick promise to be interesting and useful tools, particularly for
nanoelectronics. But such wires are so fragile and so sensi-tive to oxidation that they tend to crumble
seconds after being prepared. Now, chemistry professor Kwang S. Kim, director of the Center for
Superfunctional Materials at Pohang University of Science & Technology in South Korea, and his
colleagues have designed a sturdy organic framework to house and protect the nanowires. Kim's group
has created self-assembled nanotube clusters from calix[4]hydroquinone units [J. Am. Chem. Soc., 123,
10748 (2001)]. In mixtures of acetone and water, the calix[4]hydroquinones form "chessboardlike" arrays
of rectangular pores, the authors write. They insert silver ions into the tubes, creating wires no more than
0.4 nm in diameter yet with micrometer-scale lengths [Science, 294, 348 (2001)]. Unlike previous
attempts, which required high vacuum or extreme temperatures and pressures, the nanowire arrays can be
synthesized under mild conditions.
C&EN Volume 79, Number 52 (December 24, 2001)
A Better Recipe For -Fe 2 O 3 Nanocrystallites
A promising new method for the synthesis of highly crystalline, uniformly sized maghemite ( -Fe 2 O 3 )
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 -Fe 2 O 3 nanocrystallites (shown) using
trimethylamine oxide [(CH 3 ) 3 NO], a mild oxidant. By adjusting reaction parameters, the researchers can
"tune" the size of the -Fe 2 O 3 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 -Fe 2 O 3 nanoparticles.
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