Gas Sensors For Organic Vapor Based On SnO₂ Composite Material

Organic vapor detection has shown good application prospects in the fields of atmospheric / micro environmental monitoring, medical diagnosis and food safety detection. In order to meet the requirements of real-time, on-line and fast detection, the semiconductor oxide gas sensor with the advantages of all solid state, small size, high sensitivity and fast response has been paid more and more attention.SnO₂ gas sensing material has been widely used in the semiconductor oxide gas sensor. However, the sensitivity and selectivity of single SnO₂ materials are not high, and the gas sensing properties can be significantly improved by doping noble metals and oxides. In this work, SnO₂ was used as the main material. Oxide doped SnO₂ gas sensitive material was prepared by hydrothermal method and ultrasonic spray technology. The influence of synthesis conditions on the morphology, structure, specific surface area and other properties were tested, the sensing properties of the as-prepared materials were tested towards ethanol and acetone. The main research contents are shown as follows:（1） The In₂O₃ microflowers and SnO₂ nanoparticles were prepared by hydrothermal method. SnO₂ is composed of nanoparticles, the size of which is about 20-30 nm, the diameter of In₂O₃ microflower is about 1-1.5 μm, which is composed of aggregated nanosheets. Then two materials were mixed together. The tested results on gas sensing properties of composites show that when the quality of In₂O₃ and SnO₂ ratio is 2:1, the material has the best sensing performance and the response of the sensor to ethanol is very high, the optimal response to 100 ppm ethanol occurs in the device the optimum temperature of 250℃ and the response value as 53.2. Under UV light, the effect of humidity on the sensitivity of the sensor can be reduced.（2）Fe-SnO₂ microspheres were prepared by ultrasonic spray method. In order to explore the optimum thermal decomposition temperature, SnO₂ microspheres were prepared. The spray solution was Sn Cl4 solution. The temperature of the furnace is 500℃, 600℃, 700℃ and 800℃, respectively, and corresponding 4 kinds of gas sensing materials are prepared. The gas sensing properties of the 4 materials were tested. The results show that when the temperature of the reaction zone is 600℃, the gas sensing properties of the material are optimal. The response of S600 to 20 ppm is 8.2 when the optimum operating temperature is 275℃. On this basis, the reaction temperature is set at 600℃, then a certain amount of Fe Cl3 was added to the ultrasonic spray precursor. The experimental results show that when Fe and Sn molar ratio is 8:100, Fe-SnO₂ material for acetone showed the best gas sensitivity at 250℃. For 10 ppm acetone, the best response acetone was 6.5.