Researchers have developed a sensor that detects tiny amounts of hydrogen sulfide gas, the compound responsible for bad breath.

Existing hydrogen sulfide sensors require a power source or precise calibration, or they show low sensitivity or a slow response.

But scientists 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 colour 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 one minute.

In addition, the colour-changing sensor detected traces of hydrogen sulfide added to breath samples from 10 healthy volunteers.