Preparation Of SnO₂ Nanomaterials By Nano-cellulose Template Method And Study On Their Gas-sensitive Properties

In recent years,metal oxide semiconductors have received extensive attention in the field of gas sensors due to their low cost,simple structure and high sensitivity.Nanomaterials have become a research hotspot in modern materials science due to their special surface properties.In the field of gas sensors,more and more oxide semiconductor nanomaterials are used as sensitive materials for gas sensors to obtain better gas sensitivity.The template method is one of the common methods for preparing oxide semiconductor nanomaterials with special morphology.At present,materials with high specific surface area such as hollow nanospheres and nanotubes have been prepared by the template method.Nanocellulose has a special network structure,it is easy to removal and green non-toxic,it is a special biological template.This thesis focuses on the preparation of SnO2 nanomaterials,using bacterial cellulose and nanocrystalline cellulose as templates.After heat treatment,a porous SnO2 material composed of ultrafine nanocrystalline grains is obtained,which exhibits excellent gas sensitivity.Later,the gas sensitivity of the sensor was improved by doping rare earth elements.The specific research content is as follows:Using bacterial cellulose as a template,SnO2 nanomaterials were prepared by a simple sol-gel method.SnO2 can maintain the three-dimensional porous network structure of bacterial cellulose.The gas sensitivity test results show that the material exhibits excellent acetone gas sensing performance.By adjusting the calcination temperature,it is found that with the increase of the calcination temperature,the sample grain size increases,the specific surface area and pore volume decrease,and the sample response to acetone gas gradually decreases.The specific surface area of the SnO2 nanomaterial calcined at 500°C is 64.7m~2/g,the gas sensitivity is the best,and the response to 10 ppm acetone gas can reach 15.80at 180°C.Using nanocrystalline cellulose as a template,a porous structure of SnO2 nanomaterials were prepared by a simple sol-gel method.The material exhibited excellent acetone gas sensing performance,and the response to 10 ppm acetone gas could reach 18.10.In order to improve the gas sensitivity of the material,SnO2 nanomaterials with Ce doping concentrations of 1 wt%,3 wt%,and 5 wt%were synthesized.The gas sensitivity test results show that the SnO2:Ce gas sensor with a doping concentration of 3 wt%has a significant improvement in the sensing performance of acetone gas.At a working temperature of 170°C,the response to 10 ppm acetone gas is 27.91,and the lowest detection concentration is up to2 ppm.Finally,the gas-sensing mechanism is explained based on the electron depletion layer theory and the change of oxygen vacancy.