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Tuesday, March 22, 2011


Ultra-sensitive sensor can detect chemicals, bioagents, explosives

March 22, 2011 

Pillars support metal components that gather light and amplify Raman signals (Photo: Stephen Y. Chou)

Engineers at Princeton University have invented an extremely sensitive sensor using Raman scattering to boost faint signals generated by the scattering of laser light from a material placed on it, says Stephen Y. Chou, professor of electrical engineering.

The sensor opens up new ways to detect a wide range of substances, from tell-tale signs of cancer to hidden explosives.

The surface-enhanced Raman scattering (SERS) technique uses a chip studded with uniform rows of tiny pillars made of metals and insulators. The design uses pillar arrays with a cavity formed by metal on the top and at the base of each pillar, and metal particles of about 20 nanometers in diameter, known as plasmonic nanodots, on the pillar wall. There are small gaps of about 2 nanometers between the metal components.

The small particles and gaps significantly boost the Raman signal. The cavities serve as antennas, trapping light from the laser so it passes the plasmonic nanodots multiple times to generate the Raman signal rather than only once. The cavities also enhance the outgoing Raman signal.

The chip is a billion times more sensitive with SERS boosting of Raman signals, and the sensor is uniformly sensitive, making it more reliable for use in detecting chemicals, biological agents, and explosives, suggests Chou.


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