A microscopic image of NO2 sensitive flakes of tin disulphide

Smartphone-based NOx sensors could save lives

A low-cost sensor capable of detecting harmful nitrogen dioxide in the atmosphere that could be integrated into smartphones has been developed by Australian researchers.

The sensor, brainchild of Professor Kourosh Kalantar-zadeh from the RMIT University in Melbourne, is much cheaper than technology currently used for standard pollution measurements and at the same time much more precise than existing low-cost devices.

Inside the sensor are tiny flakes of tin disulphide, which absorb nitrogen dioxide molecules from the air.

Tin disulphide is a yellowish-brown pigment generally used in varnish for gilding. To create the sensors, researchers transformed this material into flakes just a few atoms thick. The large surface area of these flakes has a high affinity to nitrogen dioxide molecules that allows its highly selective absorption.

“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,” said Kalantar-zadeh.

“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.”

Nitrogen dioxide produced by coal-fired power plants and combustion engines in cars can cause serious conditions of the human respiratory tract. It has been associated with the development of asthma in children and can cause airway inflammation in susceptible individuals.

“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,” Kalantar-zadeh said.

“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.”

The technology was described in an article published in the latest issue of the journal ACS Nano.

Kalantar-zadeh developed the method together with fellow RMIT researchers and colleagues from the Chinese Academy of Sciences.

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