Studies On The Preparations Of ZnO And SnO₂ Nanomaterials Based On Deep Eutectic Solvents Of Urea-Choline Chloride And Their Gas Sensitive Properties

In this thesis,the deep eutectic solvents method is a simple method for preparing nanomaterials,the urea-choline chloride deep eutectic solvents has the characteristics of simple preparation,low cost,and environmental friendliness.Due to different experimental conditions,the deep eutectic solvents method can be classified into an anti-solvent precipitation method,a hydrothermal synthesis method,a solvothermal method,and an ionothermal method.Therefore,the preparations of ZnO and SnO₂nanomaterials were carried out by using urea-choline chloride as deep eutectic solvents.In order to study their gas sensing performance,eight kinds of gases inclued ammonia,acetone,xylene,methanol,formaldehyde,ethanol,ethylene glycol and isopropyl alcohol were tested.Firstly,both the rod-like and rice-like ZnO nanomaterials were prepared by anti-solvent precipitation method.The rod-like ZnO nanomaterials’s length and diameter was about 3 and 0.5 um,and the long axis and short axis of rice-like ZnO nanomaterials was about 1 um and 0.5 um.The results showed that the sensitivity of the rod-like ZnO nanomaterials to the 200 ppm concentration of methanol and ethanol gases was 15.55 and 21.63 respectively.The ZnO nanosheets with a thickness of about17 nm were prepared by the hydrothermal synthesis method.The sensitivity of ZnO nanosheets to the 200 ppm concentration of ethanol and isopropyl alcohol gases was26.24 and 34.70 respectively.Secondly,SnO₂ nanoparticles with the particle size of about 15 nm were prepared by solvothermal method.The results showed that the sensitivity of SnO₂ nanoparticles to the 200 ppm concentration of ethanol and isopropanol gases was 60.28 and 40.80respectively.In this work,the mixed phase of spherical structure which consised of nanosheets with the thickness of 30 nm was prepared by ionothermal method.The sensitivity of the mixed phase SnO₂ mesoscopic crystal materials compositing with orthorhombic and tetragonal phases to the 200 ppm concentration of methanol and ethylene glycol gases was 19.79 and 119.18 respectively.At last,the SnO₂ nanosheets with a thickness of about 13 nm were synthesized by the hydrothermal synthesis method.The results showed that the sensitivity of the SnO₂nanosheets to the 200 ppm concentration of ethanol and isopropyl gases was 80.58 and67.20 respectively.Studies have shown that the anti-solvent precipitation method,hydrothermal synthesis method,solvothermal method,and ionothermal method using urea-choline chloride as deep eutectic solvents are simple methods for the preparation of ZnO and SnO₂ nanomaterials.Gas sensitive test results show that SnO₂ nanomaterials have better gas sensitivity than ZnO nanomaterials to ethanol,ethylene glycol and isopropyl alcohol gas.