A dissertation submitted to the Faculty of Engineering and the Built Environment, University of the Witwatersrand, Johannesburg, in fulfillment of the requirements for the degree of Master of Science in Engineering. 9 February, 2017 / Global climate change and other environmental disasters have been attributed to continuous anthropogenic carbon dioxide (CO2) emission into the atmosphere. Today, researchers are constantly seeking measures to reduce anthropogenic CO2 emission. Traditionally, absorption technology with use of monoethanolamine (MEA) is used for separating / capturing of anthropogenic CO2. However, the use of MEA is associated with numerous shortcomings, including inefficient energy usage, high operating and capital cost, amine degradation, solvent loss and excessive equipment corrosion. Alternatively, zeolite based membrane systems are promising technique that prove handy and useful than the traditional processes (absorption with monoethanolamine). However, zeolitic membranes with zeolite coating on the supports (i.e. thin-film supported zeolite membranes) are susceptible to abrasion and thermal shock at elevated temperatures due to temperature mismatch between the supports and the membranes, making them to lose selectivity at early stages. On the contrary, nanocomposite architecture membranes, synthesized via pore-plugging hydrothermal route, are more thermally stable and membrane defects are controlled. Nanocomposite zeolite (sodalite) membranes have been proposed for gas separations, most importantly in the separation of H2/CO2, a major component in pre-combustion carbon capture. In addition, sodalite, a porous crystalline zeolite made up of cubic array of β-cages as primary building block having cage aperture in the range of 0.26 and 0.29 nm, is a potential candidate for the separation/purification of light molecules such as hydrogen which has a cage aperture of 0.27 nm under certain process conditions. In this work, nanocomposite architecture hydroxy sodalite membrane with sodalite crystals embedded within α-alumina tubes were successfully synthesized using the pore-plugging hydrothermal synthesis technique and characterized using techniques such as scanning electron microscopy (SEM) and X-ray diffraction (XRD). The morphology of the synthesized membranes shows that sodalite crystals were indeed grown within the porous structures of the support. Furthermore, Basic Desorption Quality Test (BDQT) and gas separation measurement were conducted to evaluate the quality of the as-synthesized membrane in industrial gas separation applications. The effects of operating variables such as pressure at 1.1 bar, 2.0 bar and 3.0 bar. Also, the effects of temperature were conducted on the nanocomposite membrane at 373 K, 423 K and 473 K. Finally, the gases permeation results were fitted with the well-known Maxwell-Stefan model. Results indicated that, the nanocomposite sodalite / ceramic membrane is a potential candidate for removal of H2 from H2/CO2 mixture. The gas permeation measurement from the one-stage nanocomposite membrane shows that the membrane displayed H2 and CO2 permeance of 3.9 x 10-7 mols-1m-2Pa-1 and 8.4 x 10-8 mols-1m-2Pa-1, respectively. However, the morphology of two-stage nanocomposite membrane shows that the support was more plugged with sodalite crystals and the permeance of H2 and CO2 were 7.4 x 10-8 mol.s-1.m-2.Pa-1 and 1.1 x 10-8 mol.s-1.m-2.Pa-1, respectively. Consequently, the H2/CO2 ideal selectivity for the one-stage nanocomposite membrane improved from 4.6 to 6.5 in the two-stage nanocomposite membrane. In conclusion, the two-stage synthesized membrane shows better improvement. The porous support was well plugged and separation performance was evaluated. However, occluded organic matters present in the cages of hydroxy sodalite could have adverse effect on the gas permeation performance of the membrane. It is expected that an organic-free sodalite supported membrane (such as silica sodalite supported membrane) could out-perform the hydroxy sodalite supported membrane reported in this work in term of membrane flux because there will be enough pore space for gas permeation. / MT2017

A dual inclusion strategy for textile polymers has been investigated to increase elastic energy storage capacity of fibers used in high velocity impact applications. Commercial fibers such as Spectra and Dyneema are made from ultra high molecular weight polyethylene (UHMWPE). Dynamic elastic energy of these fibers is still low therefore limiting their wholesale application without a secondary metallic or ceramic component. The idea in this investigation is to develop methodologies so that the elastic energy of polyethylene based fibers can be increased by several folds. This would allow manufacturing of an all-fabric system for high impact applications. The dual inclusion consists of a polymer phase and a nanoscale inorganic phase to polyethylene. The polymer phase was nylon-6 and the inorganic phase was carbon nanotubes (CNTs). Nylon-6 was blended as a minor phase into UHMWPE and was chosen because of its large fracture strain - almost one order higher than that of UHMWPE. On the other hand, CNTs with their very high strength, modulus, and aspect ratio, contributed to sharing of load and sliding of polymer interfaces as they aligned during extrusion and strain hardening processes. A solution spinning process was developed to produce UHMWPE filaments reinforced with CNTs and nylon-6. The procedure involved dispersing of CNTs into paraffin oil through sonication followed by dissolving polymers into paraffin-CNT solution using a homogenizer. The admixture was fed into a single screw extruder for melt mixing and extrusion through an orifice. The extrudate was rinsed via a hexane bath, stabilized through a heater, and then drawn into a filament winder with controlled stretching. In the next step, the as produced filaments were strain-hardened through repeated loading unloading cycles under tension. / Neat and reinforced filaments were characterized through DSC (Differential Scanning Calorimetry), XRD (X-ray Diffraction), Raman Spectroscopy, SEM (Scanning Electron Microscope), and mechanical tests. Phenomenal improvement in properties was found; modulus, strength, fracture strain, and elastic energy increased by 219%, 100%, 107% and 88%, respectively before strain hardening. Once strain hardened the strength, modulus and elastic energy increased by almost one order of magnitude. Source of these improvements were traced to increase in crystallinity and rate of crystallization, formation of microdroplets as a minor phase, sliding between minor and major phases, coating of nanotubes with polymer and alignment of nanotubes. / by Mujibur Rahman Khan. / Thesis (Ph.D.)--Florida Atlantic University, 2010. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2010. Mode of access: World Wide Web.

by Andreas Kyriacou. / Thesis (Ph.D.)--Florida Atlantic University, 2012. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2012. Mode of access: World Wide Web. / The effect of Fe substitution on the crystal structure of hydroxyapatite (HAp) is studied by applying simultaneous Rietveld refinements of powder x-ray and neutron diffraction patterns. Fe is one of the trace elements replacing Ca in HAp, which is the major mineral phase in bones and teeth. The morphology and magnetic properties of the Fe-HAp system are also studied by transmission electron microscopy and magnetization measurements. Samples of Ca(5-x)Fex(PO4)3OH with 0< x < 0.3 were prepared. Single phase HAp was identified in x-ray diffraction patterns (XRD) of samples with x < 0.1 inferring that the solubility limits are less than 0.1. Hematite ((Sa(B-Fe2O3) is identified as a secondary phase for higher Fe content. The refined parameters show that Fe is incorporated in the HAp structure by replacing Ca in the two crystallographic sites with a preference at the Ca2 site. This preference explains the small effect of the Fe substitution on the lattice constants of HAp. The overall decrease of the lattice constants is explained by the ionic vi size difference of Ca and Fe. The increasing trend of the a-lattice constant with x in the Fe substituted samples is attributed to a lattice relaxation caused by the substitution of the 4- and 6-fold Fe at the 7- and 9-fold Ca1 and Ca2 sites. This Ca local geometry reduction is indicated by a slight increase of the Ca1-O3 and Ca2-O1 bond lengths. Above the solubility limit x = 0.05, the Fe is partitioned in and out of the HAp structure with increasing nominal Fe content x. The excess Fe is oxidized to hematite. The TEM analysis and magnetic measurements support the results of the simultaneous Rietveld refinements. The TEM images show no significant effect on the morphology and size of the HAp particles upon Fe incorporation. The particles are either spheres or short rods of dimensions 20-60 nm. Hematite particles are imaged in the samples with x exceeding the solubility limit. These particles

In this investigation, polymer precursor of syntactic foam has been reinforced with SiC nanoparticles to enhance mechanical and fracture properties. Derakane 8084 vinyl ester resin was first dispersed with 1.0 wt% of SiC particles using a sonic cavitation technique. In the next step, 30.0 wt% of microspheres (3M hollow glass borosilicate, S-series) were mechanically mixed with the nanophased vinyl ester resin, and cast into rectangular molds. A small amount of styrene was used as dilutant to facilitate mixing of microspheres. The size of microspheres and SiC nanoparticles were 20-30 um and 30-50 nm, respectively. Tension, compression, and flexure tests were conducted following ASTM standards and a consistent improvement in strength and modulus within 20-35% range was observed. Fracture toughness parameters such as KIC and GIC were also determined using ASTM E-399. An improvement of about 11-15% was observed. Samples were also subjected to various environmental conditions and degradation in material properties is reported. / by Debdutta Das. / Thesis (M.S.C.S.)--Florida Atlantic University, 2009. / Includes bibliography. / Electronic reproduction. Boca Raton, Fla., 2009. Mode of access: World Wide Web.

by Kong Lim Pun. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2000. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / by Kong Lim Pun. / ABSTRACT --- p.i / 摘要 --- p.iii / ACNOWLEDGEMENT --- p.iv / TALE OF CONTENTS --- p.v / LIST OF FIGURES --- p.ix / LIST OF TABLES --- p.xi / Chapter CHAPTER 1 --- Introduction / Chapter 1.1 --- Nanoparticles and nanostructural materials --- p.1 / Chapter 1.2 --- Materials of copper-implanted and nickel-implanted fused silica --- p.4 / Chapter 1.2.1 --- Overview --- p.4 / Chapter 1.2.2 --- Formation of nanoparticles --- p.5 / Chapter 1.2.3 --- Optical properties of the material --- p.9 / Chapter 1.3 --- Goals of the project --- p.12 / Reference --- p.13 / Chapter CHAPTER 2 --- Background of Study / Chapter 2.1 --- Introduction --- p.15 / Chapter 2.2 --- Optical absorption of metal nanocluster composite glasses --- p.16 / Chapter 2.2.1 --- Dielectric constant --- p.16 / Chapter 2.2.2 --- The features of surface plasmon resonance peak --- p.16 / Chapter 2.3 --- Third-order optical nonlinearity of metal nanocluster composite glasses --- p.17 / Chapter 2.3.1 --- Classical field confinement --- p.19 / Chapter 2.3.2 --- Quantum confinement --- p.21 / Chapter 2.3.2.1 --- Intraband transitions --- p.21 / Chapter 2.3.2.2 --- Interband transitions --- p.22 / Chapter 2.3.2.3 --- Hot-electron transitions --- p.22 / Chapter 2.4 --- Preparation Methods of MNCG(s) --- p.23 / Chapter 2.4.1 --- Ion implantation --- p.23 / Chapter 2.4.2 --- Ion exchange --- p.23 / Chapter 2.4.3 --- Sputtering deposition --- p.24 / Chapter 2.4.4 --- Melt -quenching and heat-treatment processes --- p.25 / Chapter 2.4.5 --- Ion-beam assisted deposition --- p.25 / Chapter 2.5 --- Applications --- p.25 / Reference --- p.27 / Chapter CHAPTER 3 --- Instrumentation / Chapter 3.1 --- Introduction --- p.29 / Chapter 3.2 --- Metal Vapour Vacuum Arc (MEVVA) ion source implantation --- p.29 / Chapter 3.2.1 --- Background of MEVVA ion source --- p.29 / Chapter 3.2.2 --- Characteristics of MEVVA ion source --- p.32 / Chapter 3.2.3 --- Implantation conditions --- p.33 / Chapter 3.3 --- X-ray photoelectron spectroscopy --- p.34 / Chapter 3.3.1 --- Theory --- p.34 / Chapter 3.3.2 --- Qualitative analysis --- p.38 / Chapter 3.3.2.1 --- Chemical shift peaks --- p.40 / Chapter 3.3.2.2 --- Auger peaks --- p.40 / Chapter 3.3.2.3 --- Energy loss peaks --- p.40 / Chapter 3.3.3 --- Quantitative analysis --- p.41 / Chapter 3.3.3.1 --- Homogeneous system --- p.41 / Chapter 3.3.3.2 --- Determination of layer thickness --- p.45 / Chapter 3.3.4 --- Instrumental components of XPS --- p.47 / Chapter 3.3.4.1 --- Sample introduction system --- p.47 / Chapter 3.3.4.2 --- X-ray source --- p.49 / Chapter 3.3.5 --- Application to metal nanoclusters composite glasses --- p.49 / Chapter 3.3.5.1 --- Compositional analysis --- p.50 / Chapter 3.3.5.2 --- Depth profiling --- p.50 / Chapter 3.3.5.3 --- Auger parameter --- p.50 / Chapter 3.4 --- Transmission electron microscopy --- p.53 / Chapter 3.4.1 --- Basic instrumentation of TEM --- p.53 / Chapter 3.4.2 --- Preparation of TEM cross section specimen --- p.54 / Chapter 3.4.2.1 --- Cutting --- p.54 / Chapter 3.4.2.2 --- "Disc-cutting, grinding, dimpling " --- p.54 / Chapter 3.4.2.3 --- Ion beam thinning --- p.56 / Chapter 3.4.3 --- Image contrast of TEM --- p.56 / Chapter 3.4.4 --- Basic operations of TEM --- p.57 / Chapter 3.4.4.1 --- Bright field and dark field images --- p.57 / Chapter 3.4.4.2 --- Selected area diffraction (SAD) --- p.58 / Chapter 3.4.4.3 --- Convergent Beam Electron Diffraction --- p.59 / Reference --- p.60 / Chapter CHAPTER 4 --- Composition and Nano structure of Copper-implanted Fused Silica / Chapter 4.1 --- Introduction --- p.62 / Chapter 4.2 --- The Atomic Distribution and Chemical State of Copper Nanocluster --- p.64 / Chapter 4.3 --- TEM Studies of Copper Nanoclusters --- p.70 / Chapter 4.4 --- Theoretical Calculation on Ratio of Surface to Bulk Atoms of Copper Nanocluster --- p.73 / Chapter 4.5 --- Conclusions --- p.74 / Reference --- p.77 / Chapter CHAPTER 5 --- Composition and Nanostructure of Nickel-implanted Fused Silica / Chapter 5.1 --- Introduction --- p.79 / Chapter 5.2 --- The distribution of nickel nanoclusters --- p.80 / Chapter 5.3 --- TEM studies of nickel nanoclusters --- p.81 / Chapter 5.4 --- Chemical state of nickel clusters --- p.87 / Chapter 5.5 --- Discussion --- p.90 / Chapter 5.6 --- Conclusion --- p.90 / Reference --- p.92 / Chapter CHAPTER 6 --- Conclusions --- p.94

Shao, Lei = 基於金納米棒組裝的寡聚體及陣列的表面等離子體共振特性研究 / 邵磊. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2013. / Includes bibliographical references. / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Shao, Lei = Ji yu jin na mi bang zu zhuang de gua ju ti ji zhen lie de biao mian deng li zi ti gong zhen te xing yan jiu / Shao Lei.

Cheung Lok Ying Teresa = 竹炭模板上形成的二氧化硅與碳化硅納米線及其表徵 / 張樂影. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2006. / Includes bibliographical references. / Text in English; abstracts in English and Chinese. / Cheung Lok Ying Teresa = Zhu tan mo ban shang xing cheng de er yang hua gui yu tan hua gui na mi xian ji qi biao zheng / Zhang Leying. / ABSTRACT --- p.i / 摘要 --- p.iii / ACKNOWLEDGEMENTS --- p.v / TABLE OF CONTENTS --- p.vii / LIST OF FIGURE CAPTIONS --- p.xi / LIST OF TABLE CAPTIONS --- p.xv / Chapter Chapter 1 --- Introduction / Chapter 1.1. --- Biomineralization process --- p.1 / Chapter 1.2. --- Structures in biological matters --- p.2 / Chapter 1.2.1. --- Bone --- p.2 / Chapter 1.2.2. --- Wood --- p.3 / Chapter 1.3. --- Biomorphic products and their potential applications --- p.4 / Chapter 1.3.1 --- Environment conscious products --- p.4 / Chapter 1.3.2 --- Properties --- p.5 / Chapter 1.3.3 --- Carbide and oxide composites --- p.5 / Chapter 1.4 --- Common fabrication approaches --- p.6 / Chapter 1.4.1 --- Gaseous infiltration --- p.7 / Chapter 1.4.2 --- Liquid infiltration --- p.7 / Chapter 1.4.3 --- Sol-gel method --- p.8 / Chapter 1.5 --- Growth of nanowires --- p.8 / Chapter 1.5.1 --- Vapor-liquid-solid (VLS) mechanism --- p.9 / Chapter 1.5.2 --- Solution-liquid-solid (SLS) mechanism --- p.9 / Chapter 1.5.3 --- Vapor-solid (VS) mechanism --- p.10 / Chapter 1.6 --- Goals of the project --- p.10 / Chapter 1.6.1 --- Feedbacks on previous works --- p.10 / Chapter 1.6.2 --- Our breakthrough approach --- p.11 / Chapter 1.7 --- Thesis layout --- p.12 / References --- p.13 / Figures --- p.17 / Chapter Chapter 2 --- Samples preparation and characterization methods / Chapter 2.1 --- Materials selections --- p.22 / Chapter 2.1.1 --- Selection of materials for biomorphic substrate --- p.22 / Chapter 2.1.2 --- Selection of solution for infiltration --- p.23 / Chapter 2.2 --- Samples preparation --- p.24 / Chapter 2.2.1 --- Pyrolysis of raw bamboo --- p.24 / Chapter 2.2.2 --- Infiltration of reactants --- p.25 / Chapter 2.2.3 --- Sintering conditions --- p.26 / Chapter 2.3 --- Characterization methods --- p.26 / Chapter 2.3.1 --- Scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS) --- p.27 / Chapter 2.3.2 --- Transmission electron microscopy (TEM) and EDS --- p.27 / Chapter 2.3.3 --- High-resolution transmission electron microscopy (HRTEM) --- p.27 / Chapter 2.3.4 --- X-ray diffraction (XRD) --- p.28 / Chapter 2.3.5 --- X-ray photoelectron spectroscopy (XPS) --- p.28 / Chapter 2.3.6 --- Fourier transform infrared spectroscopy (FTIR) --- p.29 / Chapter 2.4 --- Conclusions --- p.29 / References --- p.30 / Figures --- p.31 / Tables --- p.33 / Chapter Chapter 3 --- Bamboo biomorphic substrates / Chapter 3.1 --- Overview --- p.34 / Chapter 3.2 --- Volumetric shrinkage and weight loss --- p.34 / Chapter 3.3 --- General morphology --- p.35 / Chapter 3.4 --- Intrinsic impurities --- p.35 / Chapter 3.5 --- Structures --- p.36 / References --- p.38 / Figures --- p.39 / Chapter Chapter 4 --- Silica / Chapter 4.1 --- Overview --- p.43 / Chapter 4.2 --- Thermal analyses --- p.44 / Chapter 4.2.1 --- Raw biomorphic substrates --- p.44 / Chapter 4.2.2 --- Infiltrated biomorphic substrates --- p.45 / Chapter 4.3 --- Experiments --- p.46 / Chapter 4.4 --- Characterization in general --- p.47 / Chapter 4.4.1 --- General morphologies --- p.47 / Chapter 4.4.2 --- Tips of the SiO2 nanowires --- p.48 / Chapter 4.5 --- Effects of sintering duration --- p.48 / Chapter 4.6 --- Effects of sintering temperature --- p.49 / Chapter 4.6.1 --- "Different temperatures, held for one hour" --- p.50 / Chapter 4.6.2 --- "Different temperatures, held for ten hours" --- p.50 / Chapter 4.7 --- Growth mechanisms --- p.52 / Chapter 4.8 --- Summary --- p.54 / References --- p.56 / Figures --- p.58 / Tables --- p.75 / Chapter Chapter 5 --- Silicon carbide / Chapter 5.1 --- Overview --- p.76 / Chapter 5.2 --- Experiments --- p.77 / Chapter 5.3 --- Characterization in general --- p.78 / Chapter 5.3.1 --- General morphologies --- p.78 / Chapter 5.3.2 --- Stacking faults and twinning --- p.79 / Chapter 5.3.3 --- Tips of the SiC nanowires --- p.81 / Chapter 5.4 --- Growth mechanisms --- p.82 / Chapter 5.5 --- Summary --- p.83 / References --- p.84 / Figures --- p.87 / Chapter Chatper 6 --- Conclusions and future works / Chapter 6.1 --- Main results of this projects --- p.101 / Chapter 6.2 --- Future works --- p.103 / References --- p.104

包含少於1000 個原子的金屬納米顆粒會與此金屬的常規尺寸材料有很大差別。它們擁有一些特殊的物理和化學的性質，因而在過去的二十年中吸引了大量的研究工作。但是由於尺寸太小，對於這些納米結構的深入和全面的研究十分困難。掃描隧道顯微鏡方法是一種強大的研究此類問題的技術。它擁有的極強的空間分辨力和原子操縱的能力使得我們可以獲得一些納米顆粒的細緻信息。在這篇論文中，我將報道我的關於在半導體Si(111)-(7x7)的重構表面的貴金屬（銀/金）顆粒的研究。 / 我首先研究了在Si(111)-(7x7)上的金屬顆粒的製備方法。使用熱蒸發方法，我製備了在Si(111)-(7x7)上的金屬顆粒。在研究了這些金屬顆粒在半元胞中的的整體生長過程之後，我的研究集中在本論文的主要目標--獨立的銀納米顆粒上。通過仔細觀察記錄單個銀原子的擴散過程，我們確認了Ag3‐Ag13 顆粒中的原子數目。這些掃描隧道顯微鏡的圖像同時也指出了這些顆粒的動態性質，包括自發跳動、分解和與鄰近的單個Ag 原子的合成。為了獲得對這些Ag 顆粒的控制，我們找到了一種垂直操縱單個Ag 原子的方法。在樣品的表面，掃描隧道顯微鏡的針尖通過特定的程序被用來抓起和放下單個Ag 原子。它被用來組裝和拆裝Ag的顆粒。各種Ag 顆粒在半元胞中被組裝，同時我們發現單個半元胞中的最大的顆粒是Ag25。同時這項技術被用來組裝複雜的Ag 顆粒的圖形。 / 使用上面這些操縱的技術（熱蒸發方法和原子操縱方法），我們細緻的研究了顆粒的兩方面性質：第一，我們發現對於單個元胞中的Ag 顆粒都存在着顯著的電學的整流效應，同時我們比較了它們各自的特點。通過實驗測量和第一性原理計算，我們發現這種電學整流效應源自電子態密度的耦合效應。當這些顆粒在平面內連接起來從而增加橫向的尺寸時，這種顆粒的整流效應將會繼續存在；但當顆粒形成多層Ag 的結構即垂直方向尺寸增加時，這個整流效應將會消失。另外一個所研究的性質是所有的Ag顆粒都存在一種對周圍單個Ag原子的吸引作用，從而讓自身長大的過程。這一過程對於Ag 顆粒的生長起到了至關重要的作用。我們選擇了幾個有代表性的顆粒，通過原子操縱的方法測量了它們與一個鄰近的Ag 原子的融合過程。測量的結果說明一個顆粒的存在通常會降低一個鄰近Ag 原子向此顆粒擴散的勢壘高度，同時也會影響此單個原子在靠近此顆粒的吸附位上的吸附能。 / Metal nanoclusters with less than 1000 atoms differ very much from their bulk counterparts. They possess many unique chemical and physical properties and have attracted extensive studies during the past two decades. However, in-depth and comprehensive researches of these structures are difficult for their small size. Scanning tunneling microscopy (STM) is a versatile technique to study the nanostructures. Its extreme powerful spatial resolution as well as its atomic manipulation capability enabled us to obtain the detailed information of some nano-clusters. In this thesis, I report on my studies on the noble metal (mainly Ag) clusters on the reconstructed Si(111)-(7x7) surface. / I firstly studied the fflbrication methods of the metal clusters on the Si(111)-(7x7) surface. By thermal deposition, I fabricated Ag clusters on Si(111)-( 7x7). After studying the overall growth process of the Ag clusters in half unit cells, I focused on the main target of this thesis: individual Ag clusters. By carefully observing the diffusion process of the Ag atoms on the surface, we identified of the number of atoms inside Ag3-Ag13 clusters. The STM images also showed the dynamic behaviors of each cluster, including self-hopping, dissociation and association with nearby Ag atoms. For a better controllability, a vertical manipulation technique was developed to transfer single Ag atoms across difference locations on the Si(111)-(7x7) surface. The STM tip was used to pick up or drop off metal atoms from or to the sud"ace following specific procedures. The assembly and disassembly of Ag clusters were achieved by this method. Various Ag clusters were built and the largest occupation of a FRUC was found to be 25 Ag atoms. This technique was demonstrated to be able to manipulate Au atoms and to assemble Au clusters. / With the developed fabrication methods, by thermal deposition as well as by atomic manipulation, two properties of the clusters were studied carefully: first, a prominent electrical rectifying behavior was observed for all the Ag clusters. Their individual behaviors were compared with each other. A combination of experimental measurements and first principle calculations unveiled the mechanism of the electronic rectifying behaviors to be a wave function coupling effect. The rectifying behavior for the clusters was found to persist when clusters connected laterally, whereas to disappear when the vertical size of the cluster increased to form multiple Ag layers. The second property studied is that all the clusters are found to attract nearby single Ag atoms to grow larger. This behavior plays a critical role in the growth process of the Ag clusters. we chose several typical Ag clusters and measured the merging process with single neighboring Ag atoms by atomic manipulation. The results indicate that the presence of a Ag cluster will mostly reduce the diffusion barrier of a single Ag atom in the neighboring half unit cells to diffuse to the cluster and even affect / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Ming, Fangfei = 在Si(111)-(7x7)表面的金屬納米顆粒的製備和性質 / 明方飛. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 116-122). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Ming, Fangfei = Zai Si(111)-(7x7) biao mian de jin shu na mi ke li de zhi bei he xing zhi / Ming Fangfei. / Chapter 1 --- Introduction: metal nano-clusters on semiconductor surfaces --- p.2 / Chapter 1.1 --- Background and Motivation --- p.2 / Chapter 1.1.1 --- Nano-science and nano-technology --- p.2 / Chapter 1.1.2 --- Metal nano-clusters --- p.3 / Chapter 1.2 --- Scanning tunneling microscopy (STM) --- p.6 / Chapter 1.2.1 --- Introduction to STM --- p.6 / Chapter 1.2.2 --- Basic components of STM --- p.7 / Chapter 1.2.3 --- STM working modes --- p.9 / Chapter 1.2.4 --- STM experiments in this thesis --- p.11 / Chapter 1.3 --- Substrate: the Si(111)-(7 x 7) reconstruction surface --- p.12 / Chapter 1.3.1 --- Atomic Structure --- p.12 / Chapter 1.3.2 --- Preparation in ultra high vacuum --- p.14 / Chapter 1.4 --- Growth of Ag on Si(111)-(7 x 7) at room temperature --- p.14 / Chapter 1.4.1 --- Growth method --- p.15 / Chapter 1.4.2 --- Adsorption and diffusion of single Ag atoms --- p.17 / Chapter 1.4.3 --- Forming Ag clusters --- p.20 / Chapter 1.4.4 --- Forming Ag islands --- p.23 / Chapter 1.5 --- Conclusion --- p.25 / Chapter 2 --- Individual Ag clusters: size, dynamics and stability --- p.27 / Chapter 2.1 --- Introduction --- p.27 / Chapter 2.2 --- Experiment --- p.29 / Chapter 2.3 --- Results and discussion --- p.31 / Chapter 2.3.1 --- Growth kinetics --- p.31 / Chapter 2.3.2 --- STrvr images of typical Ag structures Intra-HUC diffusion --- p.33 / Chapter 2.3.3 --- Inter-HUC diffusion --- p.37 / Chapter 2.3.4 --- Inter-HUC diffusion & identification of the number of atoms inside each cluster --- p.38 / Chapter 2.3.5 --- Stability of Ag structures. --- p.45 / Chapter 2.4 --- Conclusion --- p.49 / Chapter 3 --- Assembling and disassembling Ag/ Au clusters by atomic manipulation --- p.51 / Chapter 3.1 --- Introduction --- p.51 / Chapter 3.2 --- Experiment --- p.54 / Chapter 3.3 --- Results and disscussion --- p.55 / Chapter 3.3.1 --- Basic procedures for manipulating a single Ag atom --- p.55 / Chapter 3.3.2 --- Assembly of Ag clusters --- p.58 / Chapter 3.3.3 --- Disassembly of Ag clusters --- p.66 / Chapter 3.3.4 --- Assembly of Ag cluster patterns --- p.70 / Chapter 3.3.5 --- Comparison with the manipulation of Au atoms --- p.71 / Chapter 3.3.6 --- STrvr tip for atomic manipulation --- p.74 / Chapter 3.4 --- Conclusion --- p.75 / Chapter 4 --- Study on the electronic properties of the Ag clusters --- p.76 / Chapter 4.1 --- Introduction --- p.76 / Chapter 4.2 --- Experiment --- p.78 / Chapter 4.2.1 --- Experimental parameters. --- p.78 / Chapter 4.2.2 --- Precise tip positioning --- p.79 / Chapter 4.2.3 --- First principle calculation parameters --- p.80 / Chapter 4.3 --- Results and Discussion --- p.81 / Chapter 4.3.1 --- Grow Ag clusters --- p.81 / Chapter 4.3.2 --- I-V of the clusters. --- p.82 / Chapter 4.3.3 --- Theoretical calculation --- p.88 / Chapter 4.3.4 --- Transition from cluster to bulk in I-V. --- p.91 / Chapter 4.4 --- Conclusion --- p.94 / Chapter 5 --- Dynamics of Ag atoms near an interacting Ag cluster --- p.95 / Chapter 5.1 --- Introduction --- p.95 / Chapter 5.2 --- Results and Discussion --- p.97 / Chapter 5.2.1 --- Different Ag clusters and their orientations --- p.97 / Chapter 5.2.2 --- Association time measurement --- p.99 / Chapter 5.2.3 --- Energy barrier and diffusion prefactor --- p.101 / Chapter 5.2.4 --- Influenced intra-HUC diffusion --- p.105 / Chapter 5.2.5 --- Energy diagram --- p.107 / Chapter 5.3 --- Conclusion --- p.109 / Chapter 6 --- Conclusion and Future Work --- p.111 / Chapter 6.1 --- Conclusion --- p.111 / Chapter 6.2 --- Future work --- p.113 / Bibliography --- p.116

在本篇論文中，我們成功地在透明導電襯底上製備了一系列準一維納米材料陣列。我們首先製備了氧化鋅納米線陣列，然後把它們用作氧化鋅/硒化鎘核殼納米線纜陣列中的核以及合成硒化鎘和碲化鎘納米管陣列所需的犧牲模板。最後，金納米管陣列則是利用之前製備的硒化鎘納米管陣列為模板合成的。氧化鋅納米線陣列是通過高溫的熱蒸法和低溫的水熱法製備的。水熱法製備的氧化鋅納米線陣列的電導高於熱蒸法製備的氧化鋅納米線陣列，這使得水熱法製備的氧化鋅納米線更適合採用與電相關的後續處理方法。當氧化鋅納米線陣列被用作犧牲模板來製備納米管時，水熱法製備的氧化鋅納米線能被輕易地完全去除。基於這些認識，我們主要採用電化學沉積法在水熱法製備的氧化鋅納米線陣列表面沉積硒化鎘，得到了氧化鋅/硒化鎘核殼納米線纜陣列。接下來，我們將納米線纜陣列光電極和沉積了鉑催化劑的對電極組裝成三文治結構的太陽能電池。研究發現，採用多硫電解液的電池性能比碘基電解液的電池好，其中成分為1摩爾每升硫化鈉，1摩爾每升硫和1摩爾每升氫氧化鈉的多硫電解液的電池效率最高。當去除電化學沉積法生長的氧化鋅/硒化鎘和氧化鋅/碲化鎘核殼納米線纜陣列中的氧化鋅核以後，便在導電襯底上得到了硒化鎘和碲化鎘的納米管陣列。儘管兩種納米管陣列都對可見光有很強的吸收，但是，硒化鎘納米管陣列相比碲化鎘納米管陣列，表現出較高的光響應和較好的光催化降解亞甲基藍的活性。這是因為該樣品中的光生載流子能有效分離，同時能參與化學反應的表面積也較大。最後，我們選用硒化鎘納米管陣列作為模板，利用化學方法製備了金納米管陣列。金納米管的尺寸可以通過控制硒化鎘納米管模板來加以調節。當我們將具有拉曼活性的4-巰基苯甲酸分子吸附到金納米管的表面時，其拉曼散射相比未吸附時，顯著地增強了約四個數量級，如此大的提高來源於金納米管表面附近的局域電場增強效應。 / In this thesis, we demonstrated the synthesis of a series of pseudo-one-dimensional nanostructure arrays on transparent conducting substrates. We started with ZnO nanowire arrays, which were then served as the core for the ZnO/CdSe core/shell nanocable arrays formation. Further taking the ZnO as sacrificial templates led to the formation of CdSe (and CdTe) nanotube arrays. Finally, Au nanotube arrays were fabricated using the CdSe nanotube arrays as the template. ZnO nanowire arrays were synthesized via high-temperature thermal evaporation method (TE) and low temperature hydrothermal method (HT). The electrical conductivity of HT samples on the substrates was higher than that of the TE counterparts, making it attractive for further electrical-based processing. When serving as the sacrificial templates for nanotube fabrication, HT nanowires can be completely removed with ease. Based on these understanding, ZnO/CdSe core/shell nanocable arrays were obtained mainly via electrochemical deposition of CdSe on HT ZnO nanowire arrays. Nanocable-array-photoelectrode was assembled with a Pt-coated counter electrode into a sandwiched solar cell. Polysulfide electrolytes with various compositions were found to work better than iodine-based ones for such cells, and the cell with the polysulfide electrolyte containing 1 M Na₂S, 1 M S and 1 M NaOH showed highest efficiency. Removal of the ZnO cores in the electrodeposited ZnO/CdSe and ZnO/CdTe nanocable arrays left CdSe and CdTe nanotube arrays on the conducting substrate. Although strong visible-light absorption was observed from both two nanotube arrays, higher photocurrent and better photocatalytic degradation activity of methlyene blue were recorded from CdSe-nanotube-array samples (as compared to the CdTe ones), owing to effective charge separation and large surface area for chemical reactions. Lastly, Au nanotube arrays were synthesized via chemical method using CdSe nanotube arrays as the template. The dimensions of the Au nanotubes, as replicated from CdSe nanotubes, were tunable. When absorbed on the Au nanotube arrays surface, the Raman scattering of 4-mercaptobenzoic acid (a Raman-active molecule) was greatly enhanced for~4 orders of magnitude compared to the signals from the dry powder of the same molecule. Such large increase was due to the strong local electrical field enhancement near the Au nanotubes surface. / Detailed summary in vernacular field only. / Zhu, Haojun = 準一維納米結構在光伏、光催化及等離子體激元方面的應用 / 朱浩君. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2012. / Includes bibliographical references (leaves 141-168). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstract also in Chinese. / Abstracts in English and Chinese. / Zhu, Haojun = Zhun yi wei na mi jie gou zai guang fu, guang cui hua ji deng li zi ti ji yuan fang mian de ying yong / Zhu Haojun. / Abstract --- p.i / 摘要 --- p.iii / Acknowledgements --- p.iv / Contents --- p.v / List of Figures --- p.viii / List of Tables --- p.xviii / Chapter Chapter 1 --- Introductions --- p.1 / Chapter Chapter 2 --- Background --- p.4 / Chapter 2.1. --- Nanostructured Photovoltaic (PV) Solar Cells --- p.4 / Chapter 2.1.1. --- Fundamental physics of nanostructures for solar cell applications --- p.5 / Chapter 2.1.2. --- Inorganic nano-architectures for PV cells --- p.9 / Chapter 2.2. --- Nanostructures for Photocatalytic Degradation of Organic Pollutants --- p.18 / Chapter 2.2.1 --- Overview of photocatalytic degradation of organic pollutants --- p.19 / Chapter 2.2.2 --- Photocatalysis under visible light illumination --- p.24 / Chapter 2.3. --- Plamonic Noble Metal Nanostructures --- p.29 / Chapter 2.3.1 --- Surface plasmons of noble metal nanostructures --- p.29 / Chapter 2.3.2 --- Applications of plasmonic noble metal nanostructures in solar energy conversion and sensing --- p.35 / Chapter Chapter 3 --- Methodologies and Instrumentations --- p.45 / Chapter 3.1. --- Materials Growth Methodologies --- p.45 / Chapter 3.1.1. --- Thermal evaporation (TE) methods --- p.45 / Chapter 3.1.2. --- Hydrothermal (HT) methods --- p.47 / Chapter 3.1.3. --- Electrodeposition (ED) methods --- p.49 / Chapter 3.1.4. --- Prototype solar cells assemble --- p.52 / Chapter 3.2. --- Characterization Techniques --- p.53 / Chapter 3.2.1. --- Morphological, structural, and compositional analysis using electron microscopy based techniques --- p.53 / Chapter 3.2.2. --- Photoelectrochemical (PEC) performance test --- p.63 / Chapter 3.2.3. --- Photocatalytic degradation of organic pollutants --- p.65 / Chapter 3.2.4. --- Single-particle scattering imaging and spectroscopy --- p.67 / Chapter Chapter 4 --- ZnO Nanowire Arrays on Conducting Substrates -- A Comparison on the Growth Methodology --- p.71 / Chapter 4.1. --- Introduction --- p.71 / Chapter 4.2. --- Experimental --- p.72 / Chapter 4.3. --- Results and Discussions --- p.75 / Chapter 4.3.1 --- Morphologies, crystal structures and chemical compositions --- p.75 / Chapter 4.3.2 --- ZnO nanowire arrays used as electrodes --- p.80 / Chapter 4.3.3 --- ZnO nanowire arrays used as sacrificial templates in electroplating . --- p.85 / Chapter 4.4. --- Conclusions --- p.88 / Chapter Chapter 5 --- ZnO-core/CdSe-shell Nanocable Arrays for Photovoltaic Solar Cells --- p.89 / Chapter 5.1. --- Introduction --- p.89 / Chapter 5.2. --- Experimental --- p.90 / Chapter 5.3. --- Results and Discussions --- p.93 / Chapter 5.3.1 --- Synthesis of the ZnO-core/CdSe-shell nanocable arrays on ITO/glass --- p.93 / Chapter 5.3.2 --- The photovoltaic (PV) performance --- p.100 / Chapter 5.4. --- Conclusions --- p.107 / Chapter Chapter 6 --- CdSe and CdTe Nanotube Arrays as Visible-light-driven Photocatalyst for Organic Pollutant Degradation --- p.108 / Chapter 6.1. --- Introduction --- p.108 / Chapter 6.2. --- Experimental --- p.109 / Chapter 6.3. --- Results and Discussions --- p.112 / Chapter 6.3.1. --- Morphology, crystal structure, and chemical composition of the nanotube arrays --- p.112 / Chapter 6.3.2. --- Optical properties --- p.116 / Chapter 6.3.3. --- Photoelectrochemical (PEC) performance --- p.117 / Chapter 6.3.4. --- Photocatalytic activities --- p.120 / Chapter 6.4. --- Conclusions --- p.123 / Chapter Chapter 7 --- Fabrication of Au Nanotube Arrays and Their Plasmonic Properties --- p.124 / Chapter 7.1. --- Introduction --- p.124 / Chapter 7.2. --- Experimental --- p.125 / Chapter 7.3. --- Results and Discussions --- p.127 / Chapter 7.3.1. --- Morphology, crystalline structure, and chemical composition of Au nanotube arrays --- p.127 / Chapter 7.3.2. --- Au nanotube formation mechanism --- p.129 / Chapter 7.3.3. --- Plasmonic properties of Au nanotube arrays on ITO/glass substrates --- p.131 / Chapter 7.3.4. --- Plasmonic properties of single Au nanotubes --- p.133 / Chapter 7.3.5. --- Au nanotube arrays on ITO/glass as SERS substrates --- p.134 / Chapter 7.4. --- Conclusions --- p.138 / Chapter Chapter 8 --- Conclusions --- p.139 / Bibliography --- p.141

"The phase content and grain size of titanium dioxide often have a strong influence on properties for a variety of applications. In many cases it would be desirable to produce the stable rutile phase with an ultra-fine particle size (<10nm), but most low temperature synthesis methods produce predominantly the metastable anatase phase. The anatase-rutile transformation in TiO2 is known to be affected by dopant type and concentration, as well as the titanium precursor used in solution chemical synthesis. Recently, use of cavitation in the synthesis process has been shown to yield smaller grain size for a variety of oxides. However, the relative importance of these synthesis variables on the grain size and phase content of TiO2 is not well understood. In this study, Taguchi analysis was used to determine the relative effects of dopants (Sn), titanium precursor (butoxide, sulfate, chloride), and cavitation power on grain size and phase content. Precursor residuals were also measured by analytical chemistry. Grain size and phase content results were analyzed statistically to determine whether there is a size dependence of the anatase-rutile transformation. Results show that grain size is strongly dependent on the concentration of chlorine. Absent chlorine, a definite grain size-phase content correlation exists; rutile content increases as grain size decreases. An L-4 orthogonal Taguchi analysis shows chlorine content and tin content as the major influences on the final product. With minimum grain size and maximum rutile content being considered optimal, our best result was 100% rutile and an average grain size of 5nm, which was achieved by acoustic synthesis with 3% tin dopant and low residual chlorine. "