An international team of researchers from Korea and the United States has designed a tiny portable device that can directly use hydrogen sulfide (H.2S) in the human breath.
Nobody wants bad breath – not when visiting friends and family, during an interview, and certainly not on a first date.
Smelly breath can be uncomfortable, but it’s also a natural warning sign that serious dental problems are emerging.
Some devices measure small amounts of smelly hydrogen sulfide, but to do this, the exhaled air must be collected and tested with expensive instruments in the laboratory, which is not feasible for consumers.
Previous studies have shown that when some metal oxides react with sulphurous gases, their electrical conductivity changes.
And when metal oxides are paired with noble metal catalysts, they can become more sensitive and selective.
In order to develop a small real-time analyzer, Dr. Il-Doo Kim from the Korea Advanced Institute of Science and Technology, Dr. Kak Namkoong from the Samsung Advanced Institute of Technology and her colleagues find the right combination of substances that trigger the fastest and strongest response to hydrogen sulfide in air blown directly onto it.
They mixed sodium chloride and platinum nanoparticles with tungsten and spun the solution into nanofibers, which they heated, converting the tungsten into its metal oxide form.
In preliminary tests, the composite of equal parts of each metal had the greatest reactivity to hydrogen sulfide, which the researchers measured as a sharp decrease in electrical resistance in less than 30 seconds.
Although this nanofiber reacted with some sulphurous gases, it was most sensitive to hydrogen sulphide and produced a reaction 9.5 and 2.7 times stronger than with dimethyl sulphide or methyl mercaptan.
Finally, the scientists coated interlocking gold electrodes with the nanofibers and combined the gas sensor with humidity, temperature and pressure sensors to create a small prototype about the size of a human thumb.
The device correctly identified bad breath 86% of the time when real breaths were exhaled directly on it by people.
“Our sensor could be integrated into very small devices in order to diagnose bad breath quickly and easily”, according to the authors.
Her work was published in the journal in June 2021 ACS Nano.
Hamin Shin et al. Metal oxide chemiresistor matched to surface activity: On the way to a direct and quantitative diagnosis of halitosis. ACS Nano, published online June 25, 2021; doi: 10.1021 / acsnano.1c01350