Sensor detects whiff of bad breath

According to the American Dental Association, half of all adults have suffered from bad breath, or halitosis, at some point in their lives. Although in most cases bad breath is simply an annoyance, it can sometimes be a symptom of more serious medical and dental problems. However, many people aren't aware that their breath is smelly unless somebody tells them, and doctors don't have a convenient, objective test for diagnosing halitosis. Existing hydrogen sulfide sensors require a power source or precise calibration, or they show low sensitivity or a slow response. Il-Doo Kim and coworkers wanted to develop a sensitive, portable detector for halitosis that doctors could use to quickly and inexpensively diagnose the condition.

To develop their sensor, the team made use of lead(II) acetate -- a chemical that turns brown when exposed to hydrogen sulfide gas. On its own, the chemical is not sensitive enough to detect trace amounts (2 ppm or less) of hydrogen sulfide in human breath. So the researchers anchored lead acetate to a 3D nanofiber web, providing numerous sites for lead acetate and hydrogen sulfide gas to react. By monitoring a color change from white to brown on the sensor surface, the researchers could detect as little as 400 ppb hydrogen sulfide with the naked eye in only 1 minute. In addition, the color-changing sensor detected traces of hydrogen sulfide added to breath samples from 10 healthy volunteers.