Electronic Design

Nanoprobe Detects Single Molecules

Using a light-scattering technique, the Department of Energy's Oak Ridge National Laboratory has developed a sensor that can theoretically identify single molecules of substances. This probe uses an optical fiber tapered to a 100-nm tip. It's coated with a thin layer of silver nanoparticles, which induces the surface-enhanced Raman scattering (SERS) effect.

When laser beams normally illuminate a substance, there is a small reflection of light known as Raman scattering. Each compound has unique vibration energies that show up in the light, enabling scientists to identify the substance. The laser light in ORNL's SERS nanoprobe creates rapid oscillations of the electrons in the silver nanoparticles. This produces an enormous electromagnetic field that helps increase the Raman scattering signal.

Normally, scientists performing surface-enhanced Raman scattering analysis need to modify the sample prior to examination. ORNL's nanoprobe doesn't require this preparation. Its diverse applications could include environmental monitoring, intracellular sensing, medical diagnostics, and even security and law enforcement with accuracy that outstrips conventional sensor technologies.

For details, go to www.ornl.gov

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