Researchers have constructed a portable, thumb-sized device that diagnoses bad breath by quickly “sniffing” exhalations for the hydrogen sulfide — gas that makes it stinky. The electrical conductivity of some metal oxides changes when they react with sulfur-containing gases. When metal oxides are paired with noble metal catalysts, they can become more sensitive and selective. The team wanted the combination of substances that would elicit the fastest, strongest response to hydrogen sulfide blown directly onto it.
The researchers mixed sodium chloride (an alkali metal salt) and platinum (a noble metal catalyst) nanoparticles with tungsten, and electrospun the solution into nanofibers that they heated, converting the tungsten into its metal oxide form. In preliminary tests, the composite made from equal parts of each metal had the largest reactivity to hydrogen sulfide, which the team measured as a large decrease in electrical resistance in less than 30 seconds. It was most sensitive to hydrogen sulfide.
The team coated interdigitated gold electrodes with the nanofibers and combined the gas sensor with humidity, temperature, and pressure sensors into a thumb-sized prototype device. The device correctly identified bad breath 86 percent of the time when people’s breaths were exhaled directly onto it. The sensor could be incorporated into very small devices for quick and easy self-diagnosis of bad breath.
For more information, visit here .