Solution Methods For Metal Oxide Nanostructures PDF Download

This dissertation, "Fabrication and Characterization of Metal Oxide Nanostructures" by Dan, Li, 李丹, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled FABRICATION AND CHARACTERIZATION OF METAL OXIDE NANOSTRUCTURES Submitted by Li Dan for the degree of Doctor of Philosophy at The University of Hong Kong in July 2007 Among various nanostructured materials, metal oxides are very promising for a variety of practical applications. Among different possible synthesis methods for metal oxide nanostructures, hydrothermal synthesis is of great interest because it is safe and environmentally friendly, and is typically performed at temperatures of less than 200 C. In this dissertation, several metal oxide nanostructures, including zinc oxide (ZnO), copper oxide (CuO) and nickel oxide (NiO) nanostructures, were fabricated by hydrothermal synthesis from aqueous solutions of zinc/copper/nickel nitrate hydrate and hexamethylenetetramine. The morphological, structural, optical and electrochemical properties of resultant nanostructures were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffractometry (XRD), energy dispersive X-ray spectroscopy (EDX), photoluminescence (PL), and electron paramagnetic resonance spectroscopy (EPR). The obtained ZnO nanorods are straight and perpendicular to the substrate. The substrate conditions have considerable effects on the size and the orientation of the nanorods. The pH value of solutions also has significant influence on the morphology of resultant ZnO nanostructures. The PL spectra of the ZnO nanorods exhibit one UV peak and one yellow peak ( 578 nm). The ZnO nanorods also show very strong EPR signal at g 1.96. For different synthesis conditions, spherical assemblies of CuO platelets and CuO nanostructured films were obtained respectively. The solution concentration, pH value, synthesis temperature, and presence of seeds significantly affect obtained morphology as well as adhesion to the substrate. For different synthesis conditions, NiO nanowalls and NiO nanostructured films were obtained respectively. The influence of pH value is different on different NiO nanostructures. Finally, transition metal (Mn, Cr, and Co) doped ZnO nanostructures were synthesized by a hydrothermal method from aqueous solutions of zinc nitrate hydrate, TM (TM = Mn, Cr, Co) nitrate hydrate, and hexamethylenetetramine. The addition of TM nitrate hydrate resulted in the change of the shape and preferential orientation of ZnO nanorods. Also, the addition of the dopant affects the optical properties, including the ratio of UV to defect emission and the position of the UV emission peak. DOI: 10.5353/th_b3877735 Subjects: Nanostructures Metallic oxides