Korean researchers have developed a sensor that can detect tiny amounts of hydrogen sulfide gas (1 ppm or less), the compound responsible for bad breath, in human breath.

A Korea Advanced Institute of Science and Technology (KAIST) team led by Prof. Kim Il-Doo and Prof. Cha Joon-hee said on Tuesday they successfully developed a sensitive and portable detector for halitosis that doctors could use to diagnose the condition in a fast and inexpensive manner.

To develop their sensor, the team used lead (II) acetate (Pb(Ac)₂) - a chemical that turns brown when exposed to hydrogen sulfide (H₂S) gas. Lead acetate was anchored to a 3D nanofiber web to provide numerous sites for lead acetate and hydrogen sulfide gas to react.

The team said they could detect trace amounts of bad breath with the naked eye in only 1 minute by monitoring a color change from white to brown on the sensor surface.

The research result was published in the American Chemical Society (ACS)’s international journal Analytical Chemistry on May 23.

The researchers plan to further their research for applications of the sensor to detect disease, drug or gas.

The color-changing sensor technology was filed for patent applications in Korea and the U.S. for commercial development.

The color-changing gas sensor is based on a nanofiber with a large surface, offering superior sensitivity to conventional paper-based sensors and it can be used like a litmus test, said Prof. Kim.

By Won Ho-sup and Minu Kim

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