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July 20, 2018

Optical device could detect drugs, bomb-making chemicals

The image above depicts a new device for surface enhanced infrared absorption spectroscopy. Infrared light (the white beams) is trapped by tiny gaps in the metal surface, where it can be used to detect trace amounts of matter.

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When searching for traces of drugs, bomb-making components and other chemicals, researchers use a method called spectroscopy in which they shine light on the materials they're analyzing. Spectroscopy involves studying how light interacts with trace amounts of matter.

Infrared absorption is one of the most effective types of spectroscopy; scientists use it when they check for performance-enhancing drugs in blood samples and for tiny particles of explosives in the air. Researchers are working to make the technology more sensitive, inexpensive and versatile and now, a new light-trapping sensor, developed by a University at Buffalo (UB)-led team of engineers, is making progress in all three areas.

"This new optical device has the potential to improve our abilities to detect all sorts of biological and chemical samples," says Qiaoqiang Gan, an associate professor of electrical engineering in the School of Engineering and Applied Sciences at UB, and lead author of the published study.

The new sensor, which works with light in the mid-infrared band of the electromagnetic spectrum -- the part of the spectrum used for most remote controls, night-vision and other applications, consists of two layers of metal with an insulator sandwiched in between. The researchers used a fabrication technique called atomic layer deposition to create a device with gaps less than 5 nanometers (a human hair is roughly 75,000 nanometers in diameter) between two metal layers. These gaps allow the sensor to absorb up to 81 percent of infrared light, a significant improvement from the 3 percent that similar devices absorb.

This process is known as surface-enhanced infrared absorption (SEIRA) spectroscopy. The sensor, which acts as a substrate for the materials being examined, boosts the sensitivity of SEIRA devices to detect molecules at 100 to 1,000 times greater resolution than previously reported results. SEIRA could be used to find traces of molecules, including but not limited to drug detection in blood, bomb-making materials, fraudulent art and tracking diseases.

This research was supported in part by a grant from the National Science Foundation's Nanomanufacturing Program (grant CMMI 15-62057).

Read more about this research in the UB news story Beware doping athletes! This sensor may be your downfall. (Date image taken: July 2017; date originally posted to NSF Multimedia Gallery: July 20, 2018)

Credit: Qiaoqiang Gan, University at Buffalo

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