| Toxic gases in the environment are threatening the health and life safety of the human health.Therefore,the manufacture and detection of toxic gas sensors have become an extremely rapid task.CeO2 has attracted great attention in the field of gas sensor research,due to its good chemical resistance,non-toxicity,environmentally friendly,safety and reliability.In this thesis,the novel structure CeO2,silica-CeO2 and Zr-CeO2 nanomaterials are synthesized by hydrothermal method.The gas sensor based on CeO2 nanomaterials is fabricated and the gas-sensing preformance of the sensor is studied.Finally,The gas-sensing response mechanism of the sensor is analyzedThe main contents of the study of CeO2 nanomaterials are as follows:1)The silica modified CeO2 gas sensing nanocrystalline are synthesized using a sol-hydrothermal route.The 8%silica-CeO2 has larger specific surface areas of 83.75 m2/g and smaller crystalline size of 11.5 nm than pure CeO2,respectively.Compared to pure CeO2,the 8%silica-CeO2 based gas sensor exhibits significant enhancement NH3 gas-sensing performance.At room temperature,it shows much better gas response of 33.4 to 80 ppm of NH3 gas and lower detection limit(0.5 ppm)towards NH3 gas.It is also found that the gas response of the NH3 gas sensors increases linearly with the increase of NH3 gas concentration.Moreover,the NH3 gas sensor have good reversibility,stability and selectivity.The reason of enhanced NH3 gas-sensing performance is not only because of the increased specific surface areas,but also due to the electrolytic conductivity of NH4+ and OH" on the surface.2)Porous Ce0.94Zr0.06O2 nano-sheets sensing material is synthesized using a facile hydrothermal process.The average thickness of the Ce0.94Zr0.06O2 nano-sheets is about 8 nm,and the nano-sheets are found to have a mesoporous structure with an average pore size around 2.1 nm.The mesoporous structure of Ce0.94Zr0.06O2 nano-sheets resulted in larger specific surface areas of 185.4 m2/g and more pore volumes of 0.51 cm3/g than those of CeO2,which is beneficial to the absorption of target gas.Due to the special mesoporous structures in the nano-sheets and the plenty of hydroxyl groups on the surface,the NH3 sensors make of the porous Ce0.94Zr0.06O2 nano-sheets show a higher sensitivity(87 to 100 ppm NH3)and a lower detection limit(100 ppb)at room temperature than the sensors make of pure CeO2 nano-sheets prepared using the similar process.And they exhibit good selectivity,reproducibility and long-term stability to NH3 detection at room temperature.3)CeO2 nanoparticles are synthesized using a facile hydrothermal process,and their morphological and structural are studied by SEM,TEM and XRD.Moreover,the gas-sensing properties of sensors based on CeO2 were sytematically investigated.The CeO2 nanoparticles with an average diameter of 17 nm had a face-centered cubic fluorite structure.At the room temperature of 25 ?,hydrogen sulfide(H2S)gas sensor based on the CeO2 nanoparticles showed low detection limit(0.3 ppm),and fast response and recovery time.Moreover,the mechanism of H2S gas sensor based on the CeO2 nanoparticles is investigated4)Hierarchical bowknot-like CeO2 nanostructures have been successfully synthesized by a PVP-assisted hydrothermal method.The XRD pattern showed that the synthesized CeO2 have the cubic fluorite structure.Morphologies and sizes of synthesized samples were studied by SEM and TEM.The as-obtained product was uniformly hierarchical bowknot-like nanostructures,which were composed wtih nanorods as building blocks,the average diameters of nanorods was 34 nm.The UV-vis diffuse reflectance spectrum indicated that the band gap of the bowknot-like CeO2 was 3.0 eV.The room temperature photoluminescence proved that it had emission from 350 to 550... |
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