Preparation And Gas Sensing Properties Of SnO₂ Based Three-Dimensional Nanomaterials

Toxic and harmful gases are ubiquitous,they always restrict and affect people's lives.In home decoration,some furniture and paints would release volatile organic compounds,such as formaldehyde,benzene and xylene,which seriously endanger human health.In industrial production,the large-scale emitting of industrial waste gas will also lead to the decline of the quality of the atmospheric environment.In transportation,the leakage of flammable and explosive gases have caused many traffic accidents.In order to protect the environment,people's safety and health,it is necessary to design gas sensors with high sensitivity and selectivity to monitor the toxic,harmful,flammable and explosive gases in real time,so as to minimize the loss of personnel and property.This paper focuses on the design of sensitive materials and the improvement of gas sensing performance of SnO₂-based three-dimensional?3D?nanomaterials to develop gas sensors with excellent performance and for the detection of toxic and harmful gases.The research results obtained are as follows:1.Three-dimensional materials of SnO₂ with different morphologies were synthesized by a solvothermal method,and their gas sensing properties were studied.Six kinds of SnO₂ nanomaterials with different morphology were successfully prepared by precise control of solvent ratio and reaction time.It was found that when the volume ratio of ethanol to water is 3:5 and the reaction time is 15 h,porous SnO₂ hollow spheres with a diameter of about 400 nm and a shell thickness of 70nm can be obtained.Gas sensing results show that the semiconductor gas sensor based on porous SnO₂ hollow spheres performs best among six gas sensors,and its response to 50 ppm formaldehyde at 210°C can reach 52.5.2.Through a hydrothermal route,SnO/SnO₂ 3D nanomaterials with different morphologies and compositions were synthesized by controlling the proportion of raw materials.When the molar ratio of sodium citrate to stannous chloride is 10:4,the prepared material is a flower-like structure formed by assembly of ultra-thin nanosheets of 9-11 nm thickness.Through tuning raw material ratio,it is found that there are a partially incompletely oxidized SnO exist in the resulting product,so the composition of the material is SnO/SnO₂.Due to the special flower-like structure and the formation of p-n junction characteristics of SnO/SnO₂,the sensitive material not only reduces the operating temperature of the gas sensor,but also improves the response of the sensor to formaldehyde and the response speed.3.A ZnSn?OH?₆ precursor material was synthesized by coprecipitation method,and the Zn₂SnO₄/SnO₂ hollow cubic nanostructured composites with different CuO loadings were synthesized by impregnation and high temperature calcination.The gas sensitivity test results show that the presence of proper amount of CuO improves the gas sensitivity of the material.When the addition ratio of CuO is 1 wt%,the composite has the best formic acid sensitivity,which can quickly detect formaldehyde at 240°C and return to the initial state,the response value to 50 ppm formic acid is 31.9,and the selectivity and long-term stability are good,meaning that the composite is a potential material for the detection of formic acid.