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Posted: December 19, 2006

World's strongest nanowires 'near perfect materials'

(Nanowerk News) Scientists say they have made the world's strongest nanowire, reaching the theoretical limits of what they had designed.
The nanowire, which is about 1,000 times thinner than a human hair, is so strong it could support 16 African elephants if it were scaled up to the size of a child's finger, says associate professor John Sader from Australia's University of Melbourne.
Sader is part of an international team of scientists that grew the semiconducting nanomaterial, publishing the results in the journal Nano Letters.
"The ultimate strength we report is the highest recorded for any semiconductor material system and is at the theoretically predicted limit," says Sader, who was involved in measuring the strength of the wires using an atomic force microscope.
"This indicates that these nanowires are near perfect materials."
Experts say that such nanowires could one day be used to make electrical and electromechanical devices such as environmental sensors or even ultra-precise clocks.
The nanowires were built from germanium, an element the researchers say has similar chemical properties to tin. They built the material on a surface coated with gold nanocrystals, which allowed the germanium to nucleate and grow.
Amazing strength
They then tested the strength by placing it across a small trench and manipulating it sideways. They found it could bend and stretch farther than any nanowire made previously, sustaining 15 gigapascals before snapping. If the wire were one centimetre in diameter it could hold up to 100 tonnes without breaking, Sader says.
This resilience will result in failproof nanodevices, Sader said, adding it is not theoretically possible to make a stronger nanowire. "This exhibits the theoretical limits, so this is basically it."
Paul Mulvaney from the University of Melbourne's school of chemistry, who wasn't involved in the research, says the nanowires could be used as sensors to detect gases, air pollutants or biological agents. This is because they function as super-sensitive "tuning forks" that change frequency when molecules become attached to them.
"Because the wires are so small, they can detect very small amounts of materials absorbing on to their surface," he says.
They could also be used as nanoscale metronomes that vibrate in high-frequency timing devices or in computer chips, he says.
Germanium nanowires are also ideal candidates for making optical devices such as light-emitting diodes and tuneable lasers, Mulvaney said.
Source: Australian Broadcasting Corporation
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