GOLD'S GLITTER NOT THE SAME AT THE NANOSCALE

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GOLD'S GLITTER NOT THE SAME AT THE NANOSCALE
09 March 2007 - DOE/Argonne National Laboratory

Researchers at the U.S. Department of Energy's Argonne National Laboratory have found that gold "shines" in a different way at the nanoscale, and the insights may lead to new optical chips for computers or for switches and routers in fiber networks.

The nanoscale refers to a size one-billionth of a meter, or about 70,000 times smaller than the width of a human hair. Materials that small exhibit entirely different properties from conventional materials. Specifically, temperature, electricity and magnetism are completely different from that of conventional materials, and could form the basis of new technologies.

The Argonne researchers examined the characteristics of photoluminescence, the emission of light when electrons are stimulated, in gold nanorods, and found that they could control the wavelength of the light emitted by the material, making it possible to use as a light source inside an optical chip, allowing transmission of information through light. "The light emitted is dependent on the shape of the gold nanorods," said Gary Wiederrecht, Argonne scientist and leader of the research team.

The gold nanorods are about 20 nanometers wide and range from 70 to 300 nanometers long. The rod-like shape of the material is important, Wiederrecht explained, because the rod shape determines the energy of the collective electronic excitations that radiate light. Thus, photoluminescence at different wavelengths is achieved in nanorods of differing lengths. The rod shape also produces enhanced absorption of the illumination, increasing the light intensity and also concentrating that intensity to levels high enough to create luminescence. "The rods have strong absorption characteristics in the near-infrared range," Wiederrecht said. The experimenters used an ultrafast titanium-sapphire laser beam at 800 nanometers to create the photoluminescence.

While the research has future implications for technological advances, Wiederrecht is quick to explain that his group has done basic research, an examination of the material for a fundamental understanding of its characteristics. The longer-term implications of the work include the ability to produce nanoscale light sources for faster and smaller optical devices and novel photoluminescent sensors.

"Because materials at the nanoscale behave so differently from conventional materials, we're starting all over again, in a way, to understand how and why these nanomaterials function," Wiederrecht said.

Other members of the research team are lead author Alexandre Bouhelier of Argonne's Chemistry Division and the Center for Nanoscale Materials and Renaud Bachelot, Gilles Lerondel , Sergei Kostcheev and Pascal Royer, all of the Laboratoire de Nanotechnologie et d'Instrumentation Optique in Troyes, France.

The nation's first national laboratory, Argonne National Laboratory conducts basic and applied scientific research across a wide spectrum of disciplines, ranging from high-energy physics to climatology and biotechnology. Since 1990, Argonne has worked with more than 600 companies and numerous federal agencies and other organizations to help advance America's scientific leadership and prepare the nation for the future. Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.

http://www.anl.gov

About: DOE/Argonne National Laboratory
Argonne National Laboratory is one of the US Department of Energy's largest research centres. It is also the nation's first national laboratory, chartered in 1946.

Argonne is a direct descendant of the University of Chicago's Metallurgical Laboratory, part of the World War Two Manhattan Project. After the war, Argonne was given the mission of developing nuclear reactors for peaceful purposes. Over the years, Argonne's research expanded to include many other areas of science, engineering and technology.

Today, the laboratory has about 4000 employees, including about 1200 scientists and engineers, of whom about 700 hold doctorate degrees.

Argonne occupies two sites. The Illinois site is surrounded by forest preserve about 25 miles southwest of Chicago's Loop. About 3200 of Argonne's 4000 employees work on the site's 1500 wooded acres. The site also houses the US Department of Energy's Chicago Operations Office.

Argonne-West occupies about 900 acres about 50 miles west of Idaho Falls in the Snake River Valley. It is the home of most of Argonne's major nuclear reactor research facilities. About 800 of Argonne's employees work there.

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