Controlloable Synthesis Of Cuprous Oxide Micro/Nano Structure And Their Enhanced NO₂ Sensing Performance

With the rapid development of industrialization today,various chemical pollutants released from factories and auto-mobiles have been global environmental issues.As an important family of metal oxides,the cuprous oxide?Cu₂O?is well-known p-type semiconductors with excenllent photoelectric and sensing properties.The physical properties and potential applications are directly depended on their morphology and structure.In this thesis work,various Cu₂O porous nanostructures were synthesized by simple solvothermal method with polyvinyl pyrrolidone?PVP?as surfactant.The structure and morphology were characterized by SEM,XRD,N₂-absorption,and so on.The growth mechasnim of different morphology of Cu₂O nanostructure were investigated.The NO₂ gas sensing performance of these Cu₂O nanostrucrtures were studied.In order to achieve sensing materials with lower operating temperature,fast response time,and low detection limit,graphene oxide was choosen as a substrate to combine with flower-like Cu₂O porous nanostructures by simple sonication.The flower-like Cu₂O/rGO composite possessed an improved gas sensing towards NO₂ due to the synergistic effect of reduced graphene and Cu₂O porous structure.The main achievements and innovations are as follows:1.Three different Cu₂O porous nanostructures were synthesized through simple solvothermal method with polyvinyl pyrrolidone?PVP?as surfactant.The structure and morphology were characterized by XRD and SEM.According to N₂-absorption analysis,these samples were mesoporous materials with surface area of sample Cu₂O-1 has a value of 44.232?m²/g?.The morphologies and sizes of these Cu₂O porous nanostructures can be precisely controlled by changing the reactant concentration,surfactant concentration,reaction temperature,and the reaction time.The growth mechanism of flower like Cu₂O nanostructure were investigated,and PVP played important role in the synthesis process.Owning to high specific surface area and unique pore structure,the flower-like Cu₂O achieved a higher sensitivity toward NO₂,which showed potential application in NOx gas sensing.The working temperature of metal oxide gas sensor has great influence on the gas sensing performance.In this thesis work,the best operating temperature for the cuprous oxide gas sensitive materials was 250?,and the detection limit of the flower-like Cu₂O sensor was estimated to be 8.5ppm.The enhanced sensing performance of the Cu₂O-3could be attributed to the high surface area,open cavities on the surface,and the network structure formed by the connection of the surface branches.2.Introducing a second species such as graphene is another effective way to improve the sensing performance of the sensors.We desmonstrated a facile synthesis of flower-like Cu₂O NPs decorated reduced graphene oxide.The morphology and structure were characterized by Raman spectroscopy,XRD,and SEM.The as-synthesized nanocomposites have layered structures and the Cu₂O NPs were evenly loaded on the rGO surface.The composite based gas sensor exhibited good sensitive and fast response to NO₂ gas,which could be ascribed to the improved conductivity in the composites and the effective gas diffusion between the parallel layers of rGO.