Nitrogen oxide (NO_x), as a highly toxic gas, is the main source of acid rain and photochemical smog, which has posed a serious threat to human health and safety. Therefore, the detection of nitrogen oxides has become a research hotspot in recent years.

Hydrogen sulfide is a colorless gas with the odor of rotten eggs. Its toxicity is very strong. Its permissible concentration in the air is 10 ppm. The upper and lower limits of explosion range from 4.3% to 46.0%. The harm of hydrogen sulfide gas to human body belongs to chemical nerve toxicity, stimulation and asphyxiation gas, which can destroy red blood cells and cause olfactory stimulation at 0.1 ppm. Therefore, how to quantitatively detect trace hydrogen sulfide gas in the air has become an urgent problem to be solved in relevant workplaces.

In industrial production, hydrogen, as a non-polluting green energy, has attracted wide attention. However, hydrogen is volatile, low ignition point, colorless and tasteless. It is a very dangerous flammable gas when it encounters open fire when its concentration in air is 4-75%. Therefore, the monitoring technology and research of gas sensitive materials for hydrogen play an important role in ensuring personal and property safety.

Tungsten oxide resistance memory is a semiconductor device which can achieve storage by reversible change of resistance value of tungsten oxide material under electric field.