Preparation And Gas Sensing Performance Of Zn₂SnO₄,ZnO Composite SnO₂ Nanomaterials

With the development of social science and technology and industrialization,toxic and harmful gases may exist or be generated in people's lives and industrial production.These gases not only cause pollution to the environment,but also endanger people's lives and health.Because many of these gases are easily diffused or difficult to detect,gas detection plays a great significance role in environments,and gas-sensing sensors have been widely studied by people.As one of the important components of sensors,gas-sensitive materials need to have the characteristics of easy synthesis,quick response and good stability.In addition,zinc/tin oxides such as SnO₂,ZnO,and Zn₂SnO₄ are typical gas-sensing materials.It is found that zinc and tin oxide gas-sensing materials show good prospect for gas-sensing applications for formaldehyde,ethanol,and ethylene glycol.In this paper,Zn₂SnO₄/SnO₂ porous nanospheres were prepared by hydrothermal method and ZnO/SnO₂ hollow nanotubes were prepared by electrospinning method.Then their gas-sensing performance was improved by element doping.In our paper,the work includes the following three parts:1.Bi doped Zn₂SnO₄/SnO₂ nanospheres were prepared by hydrothermal method and subsequent annealing process.The results of XPS?X-ray photoelectron spectroscopy?and XRD?Diffraction of X-rays?indicate that Bi ions have been successfully doped into the crystal lattice of the sample.the performance of the two sensors was tested and it was found that the selectivity of the sensor based on Bi doped Zn₂SnO₄/SnO₂ material is better than that of pure Zn₂SnO₄/SnO₂.and it shows a higher response to formaldehyde,which shows that Bi doping effectively enhances the sensor performance of Zn₂SnO₄/SnO₂ based sensors for formaldehyde.2.Based on the hydrothermal method,Zn₂SnO₄/SnO₂ and Ag doped Zn₂SnO₄/SnO₂ porous nanospheres were synthesized at 160?for 10 h.The structure,morphology and chemical valence states were characterized by XRD,SEM?Scanning electron microscope?,TEM?Transmission electron microscope?,XPS and the gas-sensing properties of the materials were studied.The results show that compared with pure samples,Ag-doped gas sensing materials have significantly reduced size and increase specific surface area.At the same time,in terms of gas sensing performance,Ag doped Zn₂SnO₄/SnO₂ porous nanospheres show a higher response value?62.2?to 50ppm formaldehyde at a lower operating temperature?140°C?.The results show that Ag doping is an effective method for improving the gas sensitivity of materials,and Ag doped Zn₂SnO₄/SnO₂ porous nanospheres prepared by the method can be well applied to formaldehyde gas detection.3.ZnO/SnO₂ hollow nanotubes were prepared by electrospinning method.In order to improve the gas sensing performance of the prepared samples,La-doped ZnO/SnO₂hollow nanotubes were also prepared by the same method.The morphology can be seen that all samples are hollow and porous,which is helpful to improve the gas sensing performance.From a series of characterization methods,it can be found that La element has been doped into ZnO/SnO₂.By studying the performance of two gas-sensitive materials,it was found that both samples show the best selectivity for ethylene glycol.It was also found that the working temperature and response time did not change significantly after doping.But the response value after doping had been greatly improved.The response of the doped samples to 100 ppm ethylene glycol were about three times than that of the pure sample.It shows that the synthesized La-doped ZnO/SnO₂ material can be well used in the detection of ethylene glycol gas.