A man uses a smartphone
A man uses a smartphone to perform various tasks in New York. Reuters/Natalie Behring

Smartphones may soon be used to detect a deadly form of air pollution and potentially save lives, according to a group of Australian researchers.

In the study published in the journal ACS Nano, the team from RMIT University detailed how they developed the first low-cost and reliable method of monitoring the presence of nitrogen dioxide (NO2). The gas contributes to more than seven million deaths worldwide each year, according to the World Health Organisation.

Project leader Professor Kourosh Kalantar-zadeh from RMIT’s Centre for Advanced Electronics and Sensors said that the negative impact of NO2 could be prevented by accessing personalised, highly selective, sensitive and reliable monitoring systems that could detect harmful levels of the gas early.

The sensors work by physically absorbing NO2 gas molecules onto flakes of a material called tin disulphide. Tin disulphide is a yellowish-brown pigment generally used in varnish for gilding.

To create the sensors, the researchers transformed tin disulphide into flakes just a few atoms thick. The large surface area of these flakes has a high affinity to NO2 molecules that allows its highly selective absorption. This method, according to the researchers, not only increases the level of sensitivity to accepted EPA standards but outperforms any other NO2-sensing solutions on the market.

“The revolutionary method we’ve developed is a great start to creating a handheld, low-cost and personalised NO2 sensor that can even be incorporated into smartphones. Not only would it improve the quality of millions of people’s lives, but it would also help avoid illness caused by nitrogen dioxide poisoning and potentially even death,” Kalantar-zadeh said.

He pointed out that the lack of public access to effective monitoring tools is a major roadblock to mitigating the harmful effects of this gas. Current sensing systems, he noted, are either very expensive or do not have the capability to effectively distinguish NO2 from other gases.

Meanwhile, in addition to being more cost-effective, the new method that the RMIT team has developed works better than the sensors currently used to detect the dangerous gas, Kalantar-zadeh said. For the study, the researchers collaborated with their colleagues from the Chinese Academy of Sciences.

NO2 is mainly caused by the burning of fossil fuels such as coal, oil and gas. About 80 percent of NO2 in cities comes from motor vehicle exhaust. Other sources of nitrogen dioxide are petrol and metal refining, electricity generation from coal-fired power stations, other manufacturing industries and food processing. At homes, major sources of NO2 are unflued gas heaters and cookers.

NO2 is considered a critical air pollutant because it contributes to the formation of photochemical smog, which can have significant impact on human health. It increases the likelihood of respiratory problems, such as wheezing, coughing, colds, flu and bronchitis. Children with asthma and older people with heart disease are the ones at most risk.

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