Various types of so-called "electronic noses" have popped up over the years, promising to sniff out everything from minor infections to different types of cancers. But rather than diagnosing health problems after the fact, some researchers are looking more at the preventative side of things. Among these is a team of Belgian scientists that has developed what is billed as the most sensitive of such sensors yet, with a design that could see it integrated into electronics like your smartphone.

Tuning electronic noses to the threat of dangerous airborne agents like pesticides and nerve gas is something we have seen before. In 2012, researchers at the University of California, Riverside revealed a prototype device that used carbon nanotubes 100,000 times finer than a human hair with the sensitivity to detect harmful toxins down to the parts per billion level.

But the researchers from Belgium's KU Leuven have built a device they claim can pick up extremely low concentrations of such toxins, even down to a parts per trillion level. The basis for this hyper-sensitivity is the type of material the team used, called metal-organic frameworks (MOFs).

MOFs are highly ordered, porous structures with a huge surface area that can be customized to serve a variety of needs. These include purifying water, acting as battery components and the storage of gases, with the field of carbon capture an area where they have shown particular promise.

"MOFs are like microscopic sponges," explains Ivo Stassen, postdoctoral researcher at KU Leuven. "They can absorb quite a lot of gas into their minuscule pores."

Stassen and his team created an MOF using organic molecules and metal ions that soaks up the phosphates found in pesticides and nerve gases. Kind of like the way a roadside breathlyzer measures the concentration of alcohol on the breath before translating it into an electronic signal or reading, the team's chemical sensor detects traces of certain molecules, but of much more complex mixes and at much lower concentrations.

"This means you can use it to find traces of chemical weapons such as sarin or to identify the residue of pesticides on food," says Stassen. "This MOF is the most sensitive gas sensor to date for these dangerous substances. Our measurements were conducted in cooperation with imec, the Leuven-based nanotechnology research center. The concentrations we're dealing with are extremely low: parts per billion – a drop of water in an Olympic swimming pool – and parts per trillion."

The team says that the chemical sensor can be applied as a thin film over a surface, such as an electric circuit, and could therefore quite easily be fitted to a smartphone to act as a gas sensor for pesticides and nerve gas. While this was the foremost application for the device, with further development the team says that it could be used to screen human breath for diseases like early-stage cancer and multiple sclerosis.

"Or we could use the signature scent of a product to find out whether food has gone bad or to distinguish imitation wine from the original," says Stassen. "This technology, in other words, offers a wide range of perspectives."

The research was published in the journal Chemical Science.

Source: KU Leuven

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