Three Hydrothermal Synthesis Of Iron Oxide Nanostructures And Sensing Properties,

α-Fe₂O₃ nanorod-based sea urchin-like hollow microspheres, nanooctahedra andα-Fe₂O₃ nanosheet-based cobblestone-like particles have been synthesized via through a simple hydrothermal method. The reaction temperature, time and concentration of the reagent impact on the product morphology, crystal structures and gas-sensing properties of the preparedα-Fe₂O₃ nanostructures were also investigated. The possible growth mechanisms were proposed to account for the formation of the preparedα-Fe₂O₃ nanostructures and the morphologies. The structure-property relations were discussed. These investigative results would provide a base for the research of physical amd chemical properties and application ofα-Fe₂O₃ nanostructures. The gas-sensing properties of the sensor based on theα-Fe₂O₃ nanostructures with different morphologie have also been studied.(1)α-Fe₂O₃ nanorod-based sea urchin-like hollow microspheres: the hydrothermal process, growth mechanism and gas-sensing properties: In the presence of 0.05 mol/L SO₄^2-, microspheres constructed withα-FeOOH nanorods were fabricated via a hydrothermal reaction of Fe³⁺ solution at 140℃for 12 h. The as-prepared microspheres can be transformed intoα-Fe₂O₃ nanorod-based sea urchin-like hollow microspheres by calcining in air at 600℃for 2 h. Theα-Fe₂O₃ nanorod-based sea urchin-like hollow microspheres are constructed from 1-dimensional nanorods with a hexagonal structure, diameter of about 150 nm. The inner and outer diameters of the hollow microspheres are about 2 and 5μm, respectively. The role of SO₄^2- in the formation ofα-FeOOH nanorod-based microspheres was investigated, and a possible mechanism was proposed. The gas-sensing properties of theα-Fe₂O₃ superstructures have also been studied.(2) The controllable synthesis and growth mechanism ofα-Fe₂O₃ nanooctahedra and nanopolyhedra:α-Fe₂O₃ nanooctahedra and nanopolyhedra have been synthesized via a simple hydrothermal reaction of Fe(NO₃)₃ with NaOH and ethylene glycol (V_C2H6O2:V_NaOH=8:5) in the presence of KBH₄ at 180-235℃for 12 h. The control overα-Fe₂O₃ nanooctahedra and nanopolyhedra was achieved by adjusting the reaction temperature. The average dimensions ofα-Fe₂O₃ nanooctahedra and nanopolyhedra are 235 and 220 nm, respectively.(3) The controllabe preparatiton and growth mechanisms ofα-Fe₂O₃ nanosheet-based cobblestone-like particles and hollow spheral particles:α-Fe₂O₃ nanosheet-based cobblestone-like particles have been synthesized through a simple hydrothermal reaction of FeCl₃ with H₂C₂O₄ and NaOH at 120℃for 12 h. The lengths of the cobblestone-like particles are about 570 nm.α-Fe₂O₃ hollow spheral particles can be obtained by increasing the reaction temperature. The controlabe preparatiton of nanosheet-based cobblestone-like particles and hollow spheral particles were achieved by adjusting the reaction temperature. The possible mechanisms were also proposed to account for the formation ofα-Fe₂O₃ cobblestone-like and hollow spheral particles.