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

Metal Oxide Nanoparticles A complete nanoparticle resource for chemists and industry professionals Metal oxide nanoparticles are integral to a wide range of natural and technological processes—from mineral transformation to electronics. Additionally, the fields of engineering, electronics, energy technology, and electronics all utilize metal oxide nanoparticle powders. Metal Oxide Nanoparticles: Formation, Functional Properties, and Interfaces presents readers with the most relevant synthesis and formulation approaches for using metal oxide nanoparticles as functional materials. It covers common processing routes and the assessment of physical and chemical particle properties through comprehensive and complementary characterization methods. This book will serve as an introduction to nanoparticle formulation, their interface chemistry and functional properties at the nanoscale. It will also act as an in-depth resource, sharing detailed information on advanced approaches to the physical, chemical, surface, and interface characterization of metal oxide nanoparticle powders and dispersions. Addresses the application of metal oxide nanoparticles and its economic impact Examines particle synthesis, including the principles of selected bottom-up strategies Explores nanoparticle formulation—a selection of processing and application routes Discusses the significance of particle surfaces and interfaces on structure formation, stability and functional materials properties Covers metal oxide nanoparticle characterization at different length scales With this valuable resource, academic researchers, industrial chemists, and PhD students can all gain insight into the synthesis, properties, and applications of metal oxide nanoparticles.

Metal Oxide Nanostructures: Synthesis, Properties and Applications covers the theoretical and experimental aspects related to design, synthesis, fabrication, processing, structural, morphological, optical and electronic properties on the topic. In addition, it reviews surface functionalization and hybrid materials, focusing on the advantages of these oxide nanostructures. The book concludes with the current and future prospective applications of these materials. Users will find a complete overview of all the important topics related to oxide nanostructures, from the physics of the materials, to its application. - Delves into hybrid structured metal oxides and their promising use in the next generation of electronic devices - Includes fundamental chapters on synthesis design and the properties of metal oxide nanostructures - Provides an in-depth overview of novel applications, including chromogenics, electronics and energy

The aim of this project was to establish the arc discharge in water method as a valid method of producing metal oxide nanoparticles (NPs) with dielectric properties. A vertical arc discharge system was designed and fabricated and several diagnostic tools were attached to the system in order to monitor in situ the propagation of the plasma. Electrical measurements, high speed imaging, optical emission spectroscopy and electrode mass reduction measurements were employed to three different anode materials; aluminum and tantalum rods as well as a mixture of copper-tantalum compressed powder grains. The cathode of the DC arc was in all cases was a carbon rod. The product of the discharge was collected in powder form and examined by means of electron microscopy, x-ray diffraction (XRD), x-ray photoelectron spectroscopy (XPS) and broadband dielectric spectroscopy (BDS). The experiments showed that, during discharge, the physical processes occurring between the electrodes, force the anode material to evaporate in the atomic level. While atomization takes place, the water molecules surrounding the plasma region gets vaporized due to the localized high temperature resulting in the division of oxygen and hydrogen atoms. Metal and oxygen atoms bond, becoming the seeds for nanoparticle formation. The particle growth stops when quenching occurs due to the continuous condensation and expansion of the plasma. High-Resolution Transmission Electron Microscopy (HR-TEM) examination revealed that spherical crystalline nanoparticles are formed, with an average size of 40 nm when using either aluminum or tantalum rod. XRD and XPS analyses concluded that high purity Ah03 and Ta20s NPs are produced by using the arc discharge method respectively. HR-TEM was also employed to the nano-product of the composite anode showing a peculiar core-shell NP structure (mean size 20 nm). Scanning Transmission Electron Microscopy (STEM) was used in High Angle Annular Dark Field (HAADF) imaging and Energy Dispersive X-ray Spectroscopy (EDX) modes to identify the atomic arrangement resulting in the formation of an oxidized copper core with an oxidized tantalum shell. The nano-powder was tested via BDS showing a capacitive behavior. Throughout this work it was been proven that arc discharge in water is a cost- effective and easy to implement method of preparing dielectric NPs. A methodology for studying both the process as well as the product has been described. High purity Ah03 and Ta20s have been successfully produced. CuO- Ta20s core-shell NPs were synthesized for the first time and were characterized structurally and electrically. Adjustments in order to improve the efficiency of the system were proposed and new ideas for the formation of composite metal oxides have emerged.

Nanostructured Zinc Oxide covers the various routes for the synthesis of different types of nanostructured zinc oxide including; 1D (nanorods, nanowires etc.), 2D and 3D (nanosheets, nanoparticles, nanospheres etc.). This comprehensive overview provides readers with a clear understanding of the various parameters controlling morphologies. The book also reviews key properties of ZnO including optical, electronic, thermal, piezoelectric and surface properties and techniques in order to tailor key properties. There is a large emphasis in the book on ZnO nanostructures and their role in optoelectronics. ZnO is very interesting and widely investigated material for a number of applications. This book presents up-to-date information about the ZnO nanostructures-based applications such as gas sensing, pH sensing, photocatalysis, antibacterial activity, drug delivery, and electrodes for optoelectronics. - Reviews methods to synthesize, tailor, and characterize 1D, 2D, and 3D zinc oxide nanostructured materials - Discusses key properties of zinc oxide nanostructured materials including optical, electronic, thermal, piezoelectric, and surface properties - Addresses most relevant zinc oxide applications in optoelectronics such as light-emitting diodes, solar cells, and sensors