Preparation Of Metal Oxide/graphene Composite Material And Its Room Temperature Gas Sensitivity

In this thesis,by using the graphene oxide?GO?,Fe?NO₃?₃ or FeCl₃ and urea or NaOH as the raw materials and glyceryl alcohol or water as the main solvent,the small flake-like,nanopatty-like and nanosphere-like?-Fe₂O₃/rGO nanocomposites were prepared by solvothermal or hydrothermal method.By using the graphene oxide?GO?,FeCl₃,Cu?Ac?₂ and urea as the raw materials,the CuO/?-Fe₂O₃/rGO nanocomposites were prepared by hydrothermal method.The nanocomposites were characterized by using X-ray diffraction?XRD?,Raman spectra?RS?,Fourier transform infrared?FT-IR?spectra,X-ray photoelectron spectroscopy?XPS?,scanning electron microscopy?SEM?,transmission electron microscopy?TEM?techniques,N₂ adsorption-desorption?BET?and energy dispersive X-ray fluorescence spectrometer?EDXRF?.In the nanoflake-like?-Fe₂O₃/rGO nanocomposites,?-Fe₂O₃ nanoflakes,with the diameter of about 40?50nm and thickness of about 10 nm,grow on the surface of the single graphene nanosheets uniformly.In the nanopatty-like?-Fe₂O₃/rGO nanocomposites,?-Fe₂O₃nanopattys with the diameter of about 100 nm and thickness of about 20?30 nm are wraped by the single graphene nanosheets.In the nanosphere-like?-Fe₂O₃/rGO nanocomposites,the?-Fe₂O₃ nanospheres are hierarchical structure,assembled by a few nanometer sized smaller particles,with the diameter of about 40?50 nm and grow on the surface of the single graphene nanosheets uniformly.In the CuO/?-Fe₂O₃/rGO nanocomposites,CuO and?-Fe₂O₃ nanoparticles with the diameter of about 50?60 nm grow on the surface of the single graphene nanosheets uniformly.The existence of the nanoparticles prevents the aggregation of the rGO nanosheets.Thin film-type gas sensors based on these four nanocomposites were fabricated and their gas responses to CO,HCHO,H₂S,NH₃,C₂H₅OH and NO₂ were measured at room temperature.The results show that these four nanocomposites exhibited high sensitivity and selectivity to NO₂.The morphology of nanometer materials affects gas sensitivity.In three morphologies?-Fe₂O₃/rGO nanocomposites,nanosphere-like nanocomposites exhibited the best sensitivity to NO₂ at room temperature,the sensitivity of nanosphere-like nanocomposites is 150.63%to 90 ppm NO₂,the detection limit of NO₂ can be decreased down to 0.18 ppm.Under the same gas sensing measurement conditions,the sensitivity of CuO/?-Fe₂O₃/rGO nanocomposites is119.1%to 90 ppm NO₂,the response time is 42 s,the recovery time is 252 s,the detection limit of NO₂ can be decreased down to 0.9 ppm.Sensing mechanism of the nanocomposites to NO₂ was proposed.The high response of the nanocomposites to NO₂at room temperature is the synergistic effect of these two sensing materials and large specific surface area of the nanocomposites.