"The revolutionary method we have developed is a great start to creating a hand-held, low-cost and personalised NO2 sensor that can even be incorporated into smartphones," said project leader Kourosh Kalantar-zadeh, professor at RMIT University in Melbourne, Australia.

Nitrogen dioxide increases the risk of respiratory disorders in children and can severely affect the elderly in particular. The negative impact of nitrogen dioxide could be prevented by access to personalised, highly selective, sensitive and reliable monitoring systems that could detect harmful levels of the gas early, 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," Kalantar-zadeh said.Kalantar-zadeh developed the new method for sensing nitrogen dioxide together with fellow RMIT researchers and colleagues from the Chinese Academy of Sciences.

The sensors, which operate by physically absorbing nitrogen dioxide gas molecules onto flakes of tin disulphide, a yellowish-brown pigment generally used in varnish for gilding. To create 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 main contributors of nitrogen dioxide are the burning of fossil fuels, particularly in coal-fired power stations and diesel engines, which can impact on the health of people in urban areas.

The study was published in the journal ACS Nano.