Different Morphology Of Alpha-fe <sub> 2 </ Sub> O <sub> </ Sub> Nano-structure Controlled Synthesis Of Magnetic, Photocatalytic And Sensing Properties,

α-Fe₂O₃ nanocubes, microspheres constructed withα-FeOOH nanorods,α-Fe₂O₃ hexagonal nanorings, tetradedra and truncated hexagonal pyramid were fabricated via the hydrothermal reaction of Fe³⁺ solution in the presence of Cl^-, SO₄^2- or F^-, respectively, the as-obtained microspheres constructed with a-FeOOH nanorods can be transformed into porousα-Fe₂O₃ nanorod based microspheres by calcining. The role of these inorganic anions in the information process of theα-Fe₂O₃ nanostructures with different morphologie have been investigated and the possible growth mechanisms have been proposed. In addition, the magnetic, photocatalysis and gas-sensing properties of theα-Fe₂O₃ nanostructures with different morphologie have also been studied.(1)α-Fe₂O₃ nanocubes and microspheres constructed withα-FeOOH nanorods were fabricated via the hydrothermal reaction of Fe³⁺ solution at 140℃for 12 h in the presence of 0.15 mol/L Cl^-and 0.05 mol/L SO₄^2-, respectively. The as-prepared microspheres constructed withα-FeOOH nanorods can be transformed into hollowα-Fe₂O₃ nanorod based microspheres by calcining in air at 600℃for 2 h. Theα-Fe₂O₃ nanocubes have an edge length of about 500 nm, and the hollowα-Fe₂O₃ microspheres with the diameters of 2-4.5 urn are constructed from 1-dimensional nanorods with a hexagonal structure, diameter of about 150 nm. The role of Cl^- and SO₄^2-in the formation ofα-Fe₂O₃ nanocubes andα-FeOOH nanorod based microspheres was investigated, and a possible mechanism was proposed.(2) The magnetic properties ofα-Fe₂O₃ nanocubes and hollow microspheres have been measured, and a morphology dependent magnetic property was observed, the coercivity and remanent magnetization is 2858.3 Oe, 0.195 emu/g; 218.87 Oe, 0.071 emu/g at room temperature forα-Fe₂O₃ nanocubes and hollow microspheres, respectively. A gas sensor were prepared by using theα-Fe₂O₃ nanorod based microspheres, the gas sensor has good sensitivity to alcohol, acetone and the sensitivity is 2.6 and 1.9 when the concentration of alcohol and acetone is 19 ppm. In addition, it is found thatα-Fe₂O₃ hollow microspheres show high photocatalytic activity for degradation of methyl orange.(3)α-Fe₂O₃ hexagonal nanorings, tetradedra and truncated hexagonal pyramid have successfully been synthesized via a hydrothermal reaction of FeCl₃ with NaF. The control over theseα-Fe₂O₃ nanosized building bulks with different morphologie was achieved by changing the molar ratio of FeCl₃ and NaF.