서강대학교

초록/요약

In chapter 1, Single crystalline hematite nanorods with void pores were synthesized by a facile hydrothermal process and subsequent heat-treatment in air condition. The pores are formed by removal of released H2O in ？？-FeOOH nanorods and ionic liquids which were adsorbed on the surface of O-terminated ？？-FeOOH nanorods by electrostatic force and hydrogen bonds formed between the hydrogen atom at C2 position of the imidazole ring and the oxygen atom of O-Fe. The proposed formation mechanism has been investigated on the basis of a TEM image and SAED pattern. Hematite with different porosity and crystallinity has different photocatalytic property for the photodegradation of methyl orange. The temperature-dependent magnetization and magnetic hysteresis of samples indicate the interesting magnetic property evolution, which is attributed to the finite-size and surface effect of pore-solid architecture by created void pores in the rods. In chapter 2, We reported simple approach for preparing the undoped and Pt-doped ？？-Fe2O3 thin films with excellent photo-activity via facile hydrothermal growth. The photocurrent density of undoped and Pt-doped ？？-Fe2O3 thin films were recorded up to 1.2 and 1.38 mAcm-2 at 0.23 V Ag/AgCl under 1 sun illumination, respectively. In chapter 3, By the secondary growth of ？\-Fe2O3 nanocrystal assembly, highly (012) plane oriented continuous ？\-Fe2O3 thin film could be obtained on the desired substrate. The film was used as a photoanode and showed maximum photocurrent of 0.8 mA/cm2 at 0.23 V vs Ag/AgCl under the 1 sun. A strong magnetic anisotropy was observed for the film because of the magnetocrystallinity, compared with randomly oriented ？\-Fe2O3 film. In chapter 4, Alpha iron oxide (？？-Fe2O3) films were grown on catalyst-free silicon substrate using a vertical type metal-organic chemical vapor deposition process. X-ray powder diffraction and field-emission transmission electron microscopy measurements showed that these ？？-Fe2O3 films consisted of bundles of one dimensional (1D) nanorods and the nanorods in these ？？-Fe2O3 films were single crystalline with a well-ordered rhombohedral structure. The nanorods showed a preferred growth orientation in the [104] direction. The one dimensional growth of ？？-Fe2O3 nanorods was controlled by the pressure in the growth chamber. Magnetic force microscopy image suggests that spin domains were formed in the ？？-Fe2O3 nanorods. Photo-catalytic property of these nanorod films was confirmed through the photo-degradation of Rhodamine B by UV irradiation. These ？？-Fe2O3 film/nanorods materials could be used as building blocks for nanodevice applications. Finally, in chapter 5, The epitaxial growth of ZnAl2O4/ZnO core/shell nanotube from Al2O3 coated ZnO nanorods is verified by the chemical vapor deposition (CVD) of ZnO nanorod and subsequent Al2O3 deposition on the ZnO nanorod by atomic-layer deposition (ALD). Hexagonally well-faceted ZnO nanorod arrays were aligned to Si(100) wafers without metal-catalyst at 500 oC for 1 h. Thereafter it was transformed to spinel-type ZnAl2O4 nanotubes, which still have ZnO nanotube as a core, by interfacial solid-state reaction in Al2O3 coated ZnO nanorod. XRD and Raman analysis demonstrated the single crystallites of both nanotubes co-exist. The photoluminescence spectra show that ZnO nanorod, Al2O3 coated ZnO nanorod, ZnAl2O4/ZnO (core/shell) nanotube have different luminescence bands with different intensity at He-Cd laser excitation (325 nm line).