Ionothermal Svnthesis Of Nanostructured Tin Oxides And Their Gas-sensoring Performance

SnO is a p-type semiconductor which has attracted vast attention because of its wide applications, especially as the precusor of the SnO2. In this dissertation, we successfully prepared nanostructured SnO crystals by using one facile and environmental-friendly method called ionothermal strategy. The micro-structure, formation mechanism and SnO2 formation after annealing of the SnO nanoparticles were characterized clearly. At the same time, the influences of the micro-structure and chemical compostion of the nano-structured tin oxides to the gas-sensoring performances were also analysized.The ChCl/urea (CU) based Deep Eutectic Solvent (DES) was used as the reaction medium and reagent, the SnO2 was dissloved in the DES. Through tuning the reaction time and water content of the CU solvent, the SnO with different size and morphology can be synthesized.4-6 nm SnO nanoparticle under 1 min reaction time and hydrangea-like SnO balls with size about 1-1.5 μm under 60 min reaction time can be synthesized in the CU solvents with 1% water content. While when the water content of the CU solvents were 5% and 15%, multilayer pancake-like SnO can be synthesized. The pancake-like SnO from CU solvent with 15% water content has less number of layers and larger specific surface area. Through the transmission electron microscope (TEM) analysis, we find that the water in the CU solvent can contribute to the formation of SnO mesocrystals.We can get SnO2 mesocrystals with orthorhombic and tetragonal phases when the SnO mesocrystals were under the annealing process. At the same time, the proportion of orthorhombic and tetragonal phases depends on the annealing temperature and the water content in the CU solvents. The gas sensor performance of the SnO2 with mixed phases was studied. We found that the SnO2 with larger amount of orthorhombic SnO2 has better ethanol gas sensor properties and seletivity towards ethanol.When the Co2+ was added to the reaction system, we can get nano-structure Co3O4/SnO2 composite. When the concentration of the Co2+ was about 0.01 molL-1, we can get hollow polyhedral SnO2 with octahedron and cube structure. While when the concentration of the Co2" was about 0.03 molL-1 and 0.05 molL-1, there was only a little amount of polyhedral SnO2. We found that the SnO2 samples with hollow polyhedral-structure have better ethanol gas sensor properties.