No matter how hard we may try, we can't really tell if we've got bad breath – and asking someone else to sniff our breath for us can be awkward. It's now possible that before too long, however, a portable "thumb-size" device could let us know.
While bad breath can have various causes, its main smelly ingredient is typically hydrogen sulfide gas. Currently, expensive lab-based equipment is required in order to detect the gas in exhaled breath.
Seeking a less costly and more compact alternative, a team of Korean scientists looked to previous studies which indicated that the electrical conductivity of certain metal oxides changes when they're exposed to gases containing sulfur. What's more, by combining those metal oxides with noble metal catalysts, they can be made more sensitive to specific gases.
With that in mind, the researchers started by mixing equal parts sodium chloride, tungsten and nanoparticles of platinum, the latter of which is a noble metal catalyst. The resulting solution was then electrospun into composite nanofibers. When those fibers were heated, the tungsten was converted into its metal oxide form.
Although the conductivity of the nanofibers did decrease when they were subsequently exposed to several different sulfur-containing gases, the response was most pronounced for hydrogen sulfide – and it occurred within less than 30 seconds.
For the prototype bad breath detector, gold electrodes were coated with the fibers, plus they were combined with pressure, temperature and humidity sensors. When volunteers exhaled into the device, it proved to be 86 percent accurate at identifying unpleasant-smelling breath. That figure should rise as the technology is developed further.
A paper on the research – which involves scientists from the Samsung Advanced Institute of Technology, the Korea Advanced Institute of Science and Technology, and elsewhere – was recently published in the journal ACS Nano.
Source: American Chemical Society