| With the growing concern about environmental safety and protection, sensor gradually comes into sight of people as a simple and convenient detection mean. Among the gas sensor is closely related to people’s life. For example the industrial emissions of nitrogen oxides、sulfides and the poisonous and harmful gas such as formaldehyde、toluene from the indoor decoration, not only pollute the environment, but also maypose a threat to people’s health. In order to detect the poisonous and harmful gas better and avoid harming the health, the scientific researchers do their best to prepare the sensor with high response、fast response-recovery time and good stability.The metal oxide semiconductor is the main gas sensing material in gas sensor because of the simple preparation technology, low cost and good performance. So far researchers have prepared various sensing materials with different morphology. However, the pure metal oxide semiconductor gas sensor has low response and bad selectivity. So researchers begin to adopt doping, surface-decorating and semiconductor composition to improve the gas sensing performance.This article mainly includes four aspects. Firstly, we synthesized the tin oxide nanospheres by one-step hydrothermal method and doped indium oxide and noble metal palladium to improve the gas sensitive performance. Secondly, we synthesized tin oxide nanofibers via an electrospinning method. Then we decorated the noble metal palladium on the surface of the nanofibers to enhance the gas sensitive performance. Thirdly, we synthesized flower-like zinc oxide by two-step hydrothermal method. And then we decorated noble metal gold on the surface of zinc oxide nanorods. Finally, we synthesized nickel oxide/tin oxide composites by two-step hydrothermal method and tested the gas sensitive performance.In this article we study the gas sensing properties of metal oxide semiconductor material from one dimensionality to three dimensionalities. The sensing materials were characterized by XRD, SEM, EDX, TEM, XPS and BET. The gas sensing properties of the sensing materials were also investigated systematically. It shows that the gas sensing properties of pure metal oxide semiconductor gas sensor are not good. For improving the gas sensing properties, we adopted doping, surface-decorating and semiconductor composition. As was expected, the gas sensing properties of tin oxide nanospheres by indium and palladium co-doping were enhanced a lot. The response was eight times as high as that of pure tin oxide nanospheres gas sensor in 100 ppm formaldehyde. The response of palladium decorated tin oxide nanofibers gas sensor was more than twice as high as the response of pure tin oxide nanofibers gas sensor. In addition, the operating temperature was lower and the response-recovery time was faster which were beneficial to the application. Au decorated flower-like zinc oxide gas sensor had an excellent gas sensitive performance to acetone. To 100 ppm acetone the response was 18.8. The hollow nickel oxide/tin oxide composites gas sensor was sensitive to acetylene. The response was 13.8 which were twice as high as that of the pure tin oxide gas sensor. In addition, this sensor owned better response-recovery time, selectivity and stability. The improvement of gas sensing properties was due to the presence of heterostructure and the hollow structure. On the one hand, at the interface between Ni O and Sn O2 nanoparticles many p–n junctions were generated. As a result, the conducting channel was widened and the conductivity could decrease significantly. On the other hand, the hollow structure had more surface area(inner and outer) which made the molecules adsorb on the surfaces easily. As a consequence, a high response was obtained. |
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