According to the World Health Organization, nitrogen dioxide (NO2)-based air pollution contributes to over 7 million deaths per year – children and the elderly are particularly at risk. Thanks to research being carried out at Australia's RMIT University, however, it may soon be possible to receive early warnings of dangerous NO2 levels in the air around you … via a sensor in your smartphone.

Developed by a team led by Prof. Kourosh Kalantar-zadeh, the current version of the sensor absorbs airborne NO2 molecules onto ultra-thin tin disulphide flakes. By analyzing the amount of molecules on the flakes, the sensor can determine the concentration of the gas currently present in the surrounding atmosphere.

Tin disulphide is also used as a pigment in varnish, and has a natural affinity for nitrogen dioxide molecules specifically – this means that it holds onto them while ignoring other types of gas molecules, making the sensor highly accurate.

"A lack of public access to effective monitoring tools is a major roadblock to mitigating the harmful effects of this gas but current sensing systems are either very expensive or have serious difficulty distinguishing it from other gases," says Kalantar-zadeh. "The method we have developed is not only more cost-effective, it also works better than the sensors currently used to detect this dangerous gas."

RMIT is collaborating with the Chinese Academy of Sciences on the study. Scientists at the University of California, San Diego are also developing a compact sensor capable of detecting NO2, which is typically released in the burning of fossil fuels.

Source: RMIT University