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NSF Press Release


NSF PR 01-105 - December 20, 2001

Animation - Engineers Develop New Chemical Sensor Based on Experimental Physics Breakthrough

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The following is a text description of the animation:

"The animation begins by showing a dumbbell shaped oxygen molecule (chemical formula O2) landing on a rectangular array of silver atoms. When the oxygen molecule lands, the silver atoms vibrate in response and radiate heat energy.

Text: Previously, scientists thought nearly all energy from atoms adhering to a metallic surface caused vibrations that gave off heat.

However, scientists have recently discovered that nearly all interactions between molecules and metal surfaces produce energized electrons . . .

The animation now shows oxygen molecules landing on the array of silver atoms, but instead of vibrations, tiny electrons shoot away from the sites of chemical interaction.

Text: A chemical reaction occurs when the gas molecule makes contact with the surface atoms of the metal. Electrons from the metal atoms are then released.

The animation now shows a device, called a Schottky diode sensor, that is made of three unique layers. The top layer is a silicon chip that has been coated with a thin layer of silver film. The middle layer is slightly larger and thicker and it is labeled as a heater. The bottom layer is the largest and thickest, and it is labeled as a Peltier cooler. The Schottky diode sensor is hooked up to an ammeter, a device that measures current.

Text: Scientists can detect and study the current produced by the electrons with a sensor known as a Schottky diode sensor. The current has been dubbed "chemicurrent.' The basic parts of a Schottky diode sensor are shown here as part of a simple circuit. The device on the right is an ammeter, which measures current.

The animation now shows oxygen molecules flying around and landing on the surface of the Schottky diode sensor.

Text: Oxygen gas molecules (comprised of two oxygen atoms bonded together) make contact with the thin silver film and produce chemicurrent.

The animation now shows propane molecules flying around and landing on the surface of the Schottky diode sensor.

Text: Different gases for a given type of metal produce different amounts of current. Here, propane gas interacts with the sensor, producing a stronger current.

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