Synthesis And Characterization Of Transition Metal Oxide Nanomaterials

Due to their special properties, nanomaterials have attracted grate research interest and been widely applied in extensive fields such as microelectronics, catalysis, sensitization, solar cell, environment protection, bioengineering, and medicine in recent years. In the research and development of nanomaterials, transition metal oxides play a very. important role. The new nanomaterials composed of transition metal oxides have shown various functions in industrial applications. For examples, nano scale Cerium oxides, Iron oxides, and Tungsten oxides have been used as promising luminophor, magnet, and catalyst respectively.Hydrothermal and microwave-assited irradiation were two effective methods in preparing new nanomaterials. In this work, we have used these two techniques to synthesize nano scale Cerium oxides, Iron oxides and Tungsten oxides. Meanwhile the reaction conditions, the formation mechanism, and the corresponding optical properties of the three nano metal oxides were investigated in detail.At first, small-sized cerium dioxide nanorods have been prepared through a self-assembly process with CeO₂ nanoparticles in the assistance of rapid and uniform microwave irradiation. In this process, cerium nitrate and sodium hydroxide acted as the precursors dissolved in a mixture of isopropanol and water. The as-synthesized CeO₂ nanorods were characterized by transmission electron microscopy (TEM), X-ray diffraction (XRD). The results show the average diameter of CeO₂ nanorods is about 6 nm and the rods are constructed by crystallite nanoparticles. The optical behavior of the prepared CeO₂ nanorods were measured by UV-Vis spectrum and Raman spectrum.With FeCl₃ as the source materials and the mixture of isopropanol and water as the solvent,α-Fe₂O₃ nanoparticles of different shapes, e. g. spherical,shuttle-like and cubic, were synthesized by hydrothermal methods in the presence of different kinds of sodium salts. The as-synthesizedα-Fe₂O₃ nanoparticles were characterized by transmission electron microscopy (TEM), scan electron microscopy (SEM), X-ray diffraction (XRD), selected area electron diffraction (SAED) and UV-vis. The results showed that the shape ofα-Fe₂O₃ could be controlled by using different sodium salts. Spherical, shuttle-like, and cubicα-Fe₂O₃ were formed by using sodium carbonate, sodium bicarbonate, and sodium acetate, respectively. The shuttle-like and cubicα-Fe₂O₃ particles, which consisted of many small nanoparticles of about 25 nm in diameter, were found to have a single-crystal-like structure, probably due to the oriented attachment of these small nanoparticles. The UV-vis spectra indicated that theα-Fe₂O₃ had a broad absorbance band in UV-vis. The synthesis mechanism ofα-Fe₂O₃ was discussed in this paper.With ammonium tungsten oxide as the precursor, CTAB as the surfactant, monoclinic and hexagonal tungsten oxide nanorods were synthesized by hydrothermal methods at various PH values. The as-synthesized WO₃ were characterized by transmission electron microscopy (TEM), scan electron microscopy (SEM), X-ray diffraction (XRD), and UV-vis. The results showed that when PH value was 1 or lower, monoclinic tungsten oxide nanorods were synthesized; When PH were between 2.5 and 7.0, ammonium tungsten oxide (Ng₄)_0.33WO₃ were produced, and WO₃ could be obtained after calcining at high tempreture.