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RMIT researchers develop low-cost, reliable method to detect NO2; personal monitoring systems

RMIT University researchers in Australia, with their colleagues in China, have developed a low-cost and reliable method of detecting nitrogen dioxide (NO2), a significant air pollutant than contributes to more than seven million deaths worldwide each year, according to the World Health Organisation (WHO). A paper on their work is published in the journal ACS Nano.

The gas increases the risk of respiratory disorders in children and can severely affect the elderly in particular.

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

The sensors, which operate by physically absorbing nitrogen dioxide gas molecules onto flakes of tin disulphide, not only increase the level of sensitivity to accepted EPA standards, but outperform any other nitrogen dioxide sensing solutions on the market, the researchers said.

In this work, we present an important progress for selective and reversible NO2 sensing by demonstrating an economical sensing platform based on the charge transfer between physisorbed NO2 gas molecules and two-dimensional (2D) tin disulfide (SnS2) flakes at low operating temperatures. The device shows high sensitivity and superior selectivity to NO2 at operating temperatures of less than 160 °C, which are well below those of chemisorptive and ion conductive NO2 sensors with much poorer selectivity. At the same time, excellent reversibility of the sensor is demonstrated, which has rarely been observed in other 2D material counterparts.

Such impressive features originate from the planar morphology of 2D SnS2 as well as unique physical affinity and favorable electronic band positions of this material that facilitate the NO2 physisorption and charge transfer at parts per billion levels. The 2D SnS2-based sensor provides a real solution for low-cost and selective NO2 gas sensing.

—Ou et al.

Tin disulphide is 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.

Resources

  • Jian Zhen Ou, Wanyin Ge, Benjamin Carey, Torben Daeneke, Asaf Rotbart, Wei Shan, Yichao Wang, Zhengqian Fu, Adam F. Chrimes, Wojtek Wlodarski, Salvy P. Russo, Yong Xiang Li, and Kourosh Kalantar-zadeh (2015) “Physisorption-Based Charge Transfer in Two-Dimensional SnS2 for Selective and Reversible NO2 Gas Sensing” ACS Nano 9 (10), 10313-10323 doi: 10.1021/acsnano.5b04343

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