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Posted: September 25, 2008

Scientists peer into heart of compound that may detect chemical, biological weapons

(Nanowerk News) A light-transmitting compound that could one day be used in high-efficiency fiber optics and in sensors to detect biological and chemical weapons at long distance almost went undiscovered by scientists because its structure was too difficult to examine.
Luckily, scientists from U.S. Department of Energy's Argonne National Laboratory and Northwestern University were able to determine the structure of the compound using the uniquely suited Chemistry and Materials beamline of the Center for Advanced Radiation Sources (ChemMatCARS) at the Advanced Photon Source.
"Like other such materials, this material has an electrically polarized structure. The incident light interacts with the electron cloud and in the process is disturbed," Argonne scientist Mercouri Kanatzidis said. "The disturbance changes the wavelength of the emitted light and creates two beams: the original and the second harmonic — a beam with half the wavelength and double the frequency."
This second-harmonic beam is 15 times more intense than that produced by the best current material. This two-for-one wavelength boost is paired with greater transparency, so the material can actually transmit the whole higher-wavelength beam.
This could have eventual real-world applications in identifying biological and chemical weapons at long distances and in optical communications.
However, these properties almost went undiscovered. The material, (A)ZrPSe6, where A can be potassium, rubidium or cesium, has a unique and difficult chemical structure that does not crystallize very well. It grows lengthwise, but not in other directions. This creates long, thin crystals--perfect for fiber optics but a headache to study by conventional means.
"They are not very easy to design or make," Kanatzidis said. "It doesn't like to grow in other directions."
Finally, using the ChemMatCARS at the APS, Kanatzidis and Santanu Banerjee, Christos Malliakas, Joon I Jang, and John B. Ketterson were able to determine the structure and analyze its remarkable properties.
ChemMatCARS specializes in x-ray diffraction from ultra-small crystals and is operated by the Center for Advanced Radiation Sources of The University of Chicago. A paper on their work can be seen in a recent edition of the Journal of the American Chemical Society (J. Am. Chem. Soc. 2008, 37, 12270-12272.) ChemMatCARS is jointly funded by the National Science Foundation and the U.S. Department of Energy's (DOE) Office of Science, Office of Basic Energy Sciences.
About Basic Energy Sciences (BES) program
The mission of DOE's Basic Energy Sciences (BES) program - a multipurpose, scientific research effort - is to foster and support fundamental research to expand the scientific foundations for new and improved energy technologies and for understanding and mitigating the environmental impacts of energy use. Funding for the research was provided by the National Science Foundation.
About Argonne
DOE’s Argonne National Laboratory brings the world's brightest scientists and engineers together to find exciting and creative new solutions to pressing national problems in science and technology. The nation's first national laboratory, Argonne conducts leading-edge basic and applied scientific research in virtually every scientific discipline. Argonne researchers work closely with researchers from hundreds of companies, universities, and federal, state and municipal agencies to help them solve their specific problems, advance America 's scientific leadership and prepare the nation for a better future. With employees from more than 60 nations, Argonne is managed by UChicago Argonne, LLC for the U.S. Department of Energy's Office of Science.
Source: Argonne National Laboratory