Tunable LEDs shrink infrared spectroscopy down to phone-friendly size
Infrared spectrometers are expensive and powerful instruments scientists use to analyze the chemical makeup of a sample, and a new research project has demonstrated what this technology might look like if packed into a smartphone. The breakthrough hinges on a newly developed LED that can be tuned to detect different gases, and could potentially be worked into a compact device to detect everything from spoiled food to faux leather.
The study was carried out by scientists in the US and Australia, who set out to develop more mobile forms of the typically bulky infrared spectrometers used in research laboratories. These work by blasting samples with infrared radiation and then analyzing the resulting interactions, which vary depending on the molecules within the subject matter and the way they absorb, emit and reflect the light.
Chemists use this technology to study new compounds, or to help them synthesize new materials. But adapting infrared spectroscopy to work in a more mobile format could open up some interesting possibilities, such as detecting gas leaks in a mine shaft, or preventing food spoilage. As they multiply, bacteria in meat produce certain gases, the levels of which could be used to indicate spoiling. The authors of the new study have taken a promising step toward this future.
“Our new technology bonds a thin layer of black phosphorus crystals to a flexible, plastic-like substrate, allowing it to be bent in ways that cause the black phosphorus to emit light of different wavelengths, essentially creating a tunable infrared LED that allows for the detection of multiple materials,” University of Melbourne Professor Kenneth Crozier says. “This technology could fit inside smartphones and become part of everyday use.”
The breakthrough could mark a significant advance for these types of instruments, which rely on the careful construction of multiple layers of perfectly arranged crystals to filter the infrared light in a desired manner. Conversely, the team's new design is relatively simple, using just a single layer of black phosphorous to maintain flexibility, which allows for its properties to be altered and for it to generate different wavelengths that can be applied to different subject matter.
“The shift in black phosphorus' emission wavelength with bending is really quite dramatic, enabling the LED to be tuned across the mid-infrared,” says Professor Ali Javey, from the University of California at Berkeley, whose group led the work.
The scientists imagine the tunable device being deployed inside refrigerators and sending a notification to the owner when food is spoiling, or it could be worked into a smartphone to help shoppers distinguish fake leather from the real thing. It could also be integrated into drones used by firefighters and miners to detect harmful gases from a safe distance.
“Our IR photo detectors could be integrated into a camera so that we could look at our phone screen and ‘see’ gas leaks or emissions and be able to determine what kind of gas it is,” Crozier says.
The research was published in the journal Nature.
Source: University of Melbourne
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