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Nano World: Hybrid structures fuse traits

By CHARLES Q. CHOI   |   Jan. 6, 2006 at 3:47 PM   |   Comments

NEW YORK, Jan. 6 (UPI) -- A menagerie of complex new structures that assemble themselves from combinations of semiconducting, metallic or magnetic particles only nanometers or billionths of a meter wide promise to have either the combined valuable traits of their ingredients or possess entirely new useful properties, experts told UPI's Nano World.

For example, structures that pair two different semiconductors "can be employed for new generation of solar cells and thermoelectric devices," explained researcher Dmitri Talapin, a materials scientist formerly with IBM and now at Lawrence Berkeley National Laboratory in Berkeley, Calif., while combinations of magnetic and semiconducting nanoparticles "are promising for magneto-optic data storage and spintronic devices."

Devising complex devices from construction blocks that can assemble themselves into structures is crucial given the infinitesimal size of the items that nanotechnology deals in, which otherwise can often prove extraordinarily difficult to manipulate precisely on a mass scale with conventional manufacturing techniques. Investigators have gradually improved from self-assembling lattices all made of the same blocks to more complicated structures made of pairings of two different kinds of nanoparticles, with the creation of the first such binary nanoparticle superlattice in 2003, Talapin said.

Initially, scientists believed nanoparticles in these superlattices did not interact with one another. This meant that most of these structures would therefore prove unstable, and that any superlattices that lasted would typically possess relatively simple structures. However, research last year from chemical physicist Alfons van Blaaderen at Utrecht University in the Netherlands and his colleagues revealed micrometer-diameter spheres could organize themselves into crystals via electrical interactions between the particles. This hinted nanoparticles could interact via electrical charges as well, to form stable, complex structures.

In experiments that paired semiconducting, metallic or magnetic nano-sphere or nano-triangle building blocks, Elena Shevchenko and her colleagues at IBM Research Division in Yorktown Heights, N.Y., and Columbia University in New York with Talapin developed more than 15 very complex self-assembling structures, at least 10 of which are novel. Analysis with the aid of lasers revealed these structures assemble together via electric charges on the nanoparticles, as well as due to other weaker forces.

"We are currently working on employing our binary nanoparticle superlattices in electronic devices," Talapin said. He and his colleagues presented their findings, which received support in part from the National Science Foundation's Materials Research Science and Engineering Centers, in the January 5 issue of the British scientific journal Nature.

Future studies will investigate the electronic, magnetic, catalytic, optical and other physical and chemical properties the novel structures have, Talapin said. The researchers are now also on the way to developing more complex assemblies of three or more different nanoparticles, he added.

"This suggests a whole lot of new possibilities for arranging matter in three dimensions, and the number of applications they could be useful for is large," van Blaaderen said. For instance, he suggested that combining semiconductor and magnetic nanoparticles could lead to semiconductor devices that could be controlled via magnetic fields.

--

Charles Choi covers research and technology for UPI. E-mail: sciencemail@upi.com

© 2006 United Press International, Inc. All Rights Reserved. Any reproduction, republication, redistribution and/or modification of any UPI content is expressly prohibited without UPI's prior written consent.
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