New optical device can detect drugs, explosives

Scientists have developed a new light-based sensor that can help detect drugs in blood, traces of explosives in the environment as well as track diseases.
Scientists used an approach known as spectroscopy which involves studying how light interacts with trace amounts of matter.
"This new optical device has the potential to improve our abilities to detect all sorts of biological and chemical samples," said Qiaoqiang Gan, associate professor at University of Buffalo in the US.
The new sensor works with light in the mid-infrared band of the electromagnetic spectrum.
This part of the spectrum is used for most remote controls, night-vision and other applications.

The sensor consists of two layers of metal with an insulator sandwiched in between. Using a fabrication technique called atomic layer deposition, researchers created a device with gaps less than five nanometres (a human hair is roughly 75,000 nanometres in diameter) between two metal layers.

These gaps enable the sensor to absorb up to 81 per cent of infrared light, a significant improvement from the three per cent that similar devices absorb, researchers said.
The 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, researchers said.

The increase makes SEIRA spectroscopy comparable to another type of spectroscopic analysis, surface-enhanced Rama spectroscopy (SERS), which measures light scattering as opposed to absorption.
"The SEIRA advancement could be useful in any scenario that calls for finding traces of molecules," said Dengxin Ji, a PhD candidate in Gan's lab.
"This includes but is not limited to drug detection in blood, bomb-making materials, fraudulent art and tracking diseases," Ji added.
The study was published in the journal Advanced Optical Materials.