Study On Fabrication And Gas Sensitive Properties Of TiO₂-based Nanomaterials With Different Morphology

Gas sensors have currently become increasingly important in industrial production and daily life.Metal oxide semiconductor has become one of the most widely used and fastest growing gas sensors because of its advantages in simple structure,low cost,fast response and so on.As a gas sensing materials,the properties are mainly determined by the grain size,doping ions,phase composition,microstructure morphology and the inherent properties of the material itself.Characterization of nanomaterials such as ultra small size,large surface area to volume ratio,can significantly improve the sensitivity of the sensor compared with conventional materials.Surface modified with other groups,the performance of the gas sensing can be greatly improved.In this paper,we report TiO₂-based materials,by doping noble metal Au,two kinds of Au-TiO₂ composite with different morphology were synthesized.The gas sensing properties were investigated.Au-doped TiO₂ exhibited the best gas sensing performance than pure TiO₂.The characterization?performance of the gas sensing materials contents are as follows:?1?.By changing the volume ratio of HAuCl₄ and TiF₄ solution,the Au@TiO₂nanocomposites with different Au/Ti ratios are synthesized by hydrothermal method.The composition,structure and morphology of the materials were characterized.It turned out that when the Au/Ti molar ratio was 0.1875 formed a lotus shaped nuclear shell structure.The formation mechanism of the structure is discussed in detail.The as-prepared samples was made into gas components and tested for sensing of CO.Lotus-like 18.75 mol%Au@TiO₂ gas sensing elements showed the highest sensitivity,the shortest response recovery time,and the lowest operating temperature.The gas sensing mechanism was discussed in detail,and the reasons for the better gas sensing properties of lotus-like structure were explained.?2?.Using Cu₂O as template,the hollow cube Au-TiO₂ nanocomposites was synthesized.The characterizations of the materials were investigated.TiO₂ as the cube structure of the frame with the size of 1?m,Au particles dispersed on the surface of the hollow cube.The formation process of the cubic structure is discussed in detail.The materials have agood response to VOCs,which is different from that of the lotus-like Au@TiO₂.?3?.Investigating and comparing the gas sensing properties of Au-TiO₂ nanocomposites with different morphology,surface defects and surface-adsorbed species have been known to significantly influence on gas sensing performance.On the other hand,the formation of P-N heterojunction in hollow cube Au-TiO₂ nanocomposites,resulting in the different gas sensing response to the N-type Lotus-like Au@TiO₂.This paper mainly studies the TiO₂-based gas sensor with noble metal-doping and control of morphology.It is proved that the doping noble metal is beneficial to the improvement of gas sensing properties and the different morphologies also have an influence on the gas sensing properties,which provides a new idea for improving the gas sensing properties of TiO₂-based gas sensors.