In order to mitigate the pollution hazard of NO2 atmosphere, Dou Xinsuo, an environmental science and technology research institute of Xinjiang Institute of Physics and Chemistry, Chinese Academy of Sciences, developed a gas sensor capable of detecting ppb grade NO2 quickly and sensitively and achieved certain results.
With the rapid development of industry, air pollution is worsening day by day. NO2 as one of the most important air pollutants, its very low concentration (ppb level) will be able to produce greater harm to the human body. Therefore, it is of practical significance to develop a gas sensor that can detect ppb grade NO2 quickly and sensitively. NO2 gas sensor with metal oxide as the sensitive material has the advantages of simple production process, low cost and the like.
However, the problem of low sensitivity directly limits the practical application of metal oxides in the detection of ppb grade NO2. In recent years, a series of theoretical and experimental results show that the surface defects of metal oxide semiconductor materials can improve the adsorption capacity of NO2 molecules and effectively promote the transfer of electrons from the conduction band of the semiconductor to the NO2 molecule, thereby effectively increasing Its detection sensitivity. Therefore, it is of great research value to realize the ultra-sensitive detection of NO2 by regulating the surface defects of materials.
Currently, the type of surface defect that has been widely studied is the single electron oxygen vacancy defect (VO). However, another defect, superoxide radical (Sn 4+ - O 2-), located on the surface of SnO 2 has not been induced enough Pay attention. Compared with VO defect centers, electrons are more likely to interact with NO2 molecules on superoxide radicals in order to enhance their sensitivity. The reason for this is that the electrons are located on the adsorbed O2 molecules and are far away from the binding of SnO2 lattice. However, the relationship between this specific structure defect and material sensitivity has not been studied.
In 2015, the team of Xinxin Xu of Environmental Science and Technology Research Institute of Xinjiang Institute of Physical and Chemical Technology, Chinese Academy of Sciences designed and constructed thermodynamically unstable preparation conditions in order to introduce such defects on the surface of materials. The researchers used the extremely unstable SnCl4 as raw material, Ice bath to control the reaction temperature to prevent the intense hydrolysis reaction, and then use the high temperature and pressure hydrothermal environment instantly break the metastable state precursor solution to obtain defects.
Based on this method, superoxide complex radicals can be successfully introduced onto the surface of the material. The sensor prepared with this material has ultra-sensitive sensing properties (up to 35,350 times as much as 200 ppb of NO2) for NO2 in the ppb concentration range. Compared with the related literature reports in recent years, the material is the most sensitive NO2 sensing material in the world at present.
In addition, researchers have demonstrated for the first time that tiny changes in the amount of superoxide radicals on the surface of a material can cause dramatic changes in the material's sensitivity. The sensor based on this material has long-term stability, good repeatability, selectivity, and rapid recovery under UV light and a series of excellent sensor characteristics, which can provide strong protection for the industrialized production of the sensor.
Relevant research results published in the Small form on the Small, and "Materials Views China" as a highlight. The work was funded by the National Natural Science Foundation of China, the "Hundred Talents Program" of Chinese Academy of Sciences, the light of the west, and the outstanding young people of Xinjiang Uygur Autonomous Region.
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