Research On Chemical Sensors Based On Semiconductor Oxides And Their Composites

Sensors are devices or systems to obtain information，they are in the initial partsof information chain. As an important branch of chemical sensors, gas and humiditysensors are widely used in environmental, safety, weather, industrial control, medicalwelfare and other fields, arousing more and more attention. In order to meet the needsof each of these fields, gas and humidity sensors are pursuiting high sensitivity, goodselectivity, fast response-recovery speed, low detection limit, high reliability, low powerconsumption and other indicators. As the core of sensors, sensitive materials candirectly affect their characteristics. Therefore, development of high performancesensitive materials is essential for enhancing the performances of sensors. Herein, forthe development of high-performance gas and humidity sensors, we systematicallyinvestigated the preparation and gas/humidity sensing properties of semiconductoroxides and their composites, specifically as follows:1. Well dispersed WO3nanoparticle were synthesized via a microwave-irradiationmethod and a subsequent heat treatment, a gas sensor based on the as-prepared materialswas prepared and tested. Gas sensing tests showed that the WO3-based gas sensorscould work at a relatively low temperature and exhibit high response to NO2with lowconcentration. In addition, the detection limit of the sensor was as low as5ppb.2. Monodisperse flower-like WO3structures consisting of nanorods were obtainedby calcining W18O49nanowires which were prepared by a microwave-assistedsolvothermal method. Sensors based on the as-prepared materials exhibited highresponses and selectivities to ppb level NO2, in addition, its operating temperature wasas low as90°C. When working at300°C, the sensor showed a fast response andrecovery speed to100ppm acetone. 3. Monodisperse WO3hierarchical spheres were successfully prepared by amicrowave-assisted hydrothermal method, the impact of the hydrothermal reaction timeon the material was also investigated and discussed. It was found that the hydrothermalreaction time had a great influence on the materials in terms of size and dispersion. Agas sensor was prepared with the obatined WO3, and tests showed that the sensorshowed good selectivity and reproducibility to acetone. Further more, when theconcentration of acetone was in the range of10-1000ppm, the relationship betweenthe response and the acetone concentration exhibited a good linearity.4. Urchin-like CuO-reduced graphene oxide (rGO) composite was synthesized bya one-pot microwave-assisted hydrothermal method. The effects of introducing rGO tothe composite material was systematically investigated. It was found that rGO hadalmost no response to humidity, however, humidity sensors based on the abovecomposite showed a lot of advantages, such as high response, fast response-recoveryspeed, good repeatability. In addition, the humidity sensing mechanism of thecomposites were discussed in depth, a theory related to Schottky junction was used toexplain the humidity sensing properties.