Sniffing biological, chemical weapons from distance gets closer to reality

Washington, September 27 : American scientists have determined the structure of a light-transmitting compound that can one day be used in high-efficiency fibre optics, and in sensors to detect biological and chemical weapons from long distances.

The achievement stems from the efforts of researchers associated with the U.S. Department of Energy's Argonne National Laboratory and Northwestern University, who used 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. 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," Argonne scientist Mercouri Kanatzidis said.

The second-harmonic beam is 15 times more intense than that produced by the best current material.

The researchers say that the two-for-one wavelength boost is paired with greater transparency so that the material can actually transmit the whole higher-wavelength beam, which can have eventual real-world applications in identifying biological and chemical weapons at long distances and in optical communications.

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, creating long, thin crystals - perfect for fibre optics, but a headache to study by conventional means.

"They are not very easy to design or make. It doesn't like to grow in other directions," Kanatzidis said.

The structure of the compound was finally determined, and its remarkable properties analysed, when the researchers used the ChemMatCARS at the APS

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.

ANI