Ku, Sin Yee = 添加鎳對網絡結構Fe₈₀C₂₀合金機械性能的影響 / 古倩儀. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2011. / Includes bibliographical references. / Abstracts in English and Chinese. / Ku, Sin Yee = Tian jia nie dui wang luo jie gou Fe₈₀C₂₀ he jin ji xie xing neng de ying xiang / Gu Qianyi. / Abstract --- p.i / Acknowledgements --- p.v / List of Tables --- p.viii / List of Figures --- p.ix / Chapter Chapter 1: --- Introduction --- p.1 / Chapter 1.1 --- Composite Materials --- p.1 / Chapter 1.1.1 --- Parti culate-reinforced Composites --- p.2 / Chapter 1.1.2 --- Fibre-reinforced Composites --- p.2 / Chapter 1.1.3 --- Structural Composites --- p.3 / Chapter 1.1.4 --- Metal Matrix Composites --- p.3 / Chapter 1.2 --- Phase Transformations --- p.4 / Chapter 1.2.1 --- Introduction --- p.4 / Chapter 1.2.2 --- Stability and Equilibrium --- p.4 / Chapter 1.2.3 --- Undercooling --- p.6 / Chapter 1.2.4 --- Solidification of Undercooled Melts --- p.7 / Chapter 1.2.4.1 --- Nucleation --- p.8 / Chapter 1.2.4.1.1 --- Homogeneous Nucleation --- p.8 / Chapter 1.2.4.1.2 --- Heterogeneous Nucleation --- p.9 / Chapter 1.2.4.2 --- Growth --- p.11 / Chapter 1.2.5 --- Binary Systems with a Solid Miscibility Gap --- p.12 / Chapter 1.2.6 --- Phase Separation Mechanisms in a Solid Miscibility Gap --- p.14 / Chapter 1.2.6.1 --- Nucleation and Growth --- p.14 / Chapter 1.2.6.2 --- Spinodal Decomposition --- p.15 / Chapter 1.2.6.2.1 --- Uphill Diffusion --- p.16 / Chapter 1.2.6.2.2 --- Diffusion Equation of Spinodal Decomposition --- p.17 / Chapter 1.2.6.2.3 --- Solution to the Diffusion Equation --- p.19 / Chapter 1.2.7 --- Metastable Liquid Miscibility Gap --- p.21 / Chapter 1.3 --- Mechanical Properties --- p.22 / Chapter 1.3.1 --- Hardness --- p.22 / Chapter 1.3.2 --- Strength --- p.23 / Chapter 1.3.3 --- Ductility --- p.23 / Chapter 1.3.4 --- Strengthening Mechanisms --- p.25 / Chapter 1.3.4.1 --- Grain Boundary Strengthening --- p.25 / Chapter 1.3.4.2 --- Solid Solution Strengthening --- p.26 / Chapter 1.4 --- Objectives of This Project --- p.27 / Figures --- p.29 / References --- p.42 / Chapter Chapter 2: --- Experimental --- p.43 / Chapter 2.1 --- Formation of Bulk Network Nanostructured Alloys --- p.43 / Chapter 2.1.1 --- Preparation of Fused Silica Tubes --- p.43 / Chapter 2.1.2 --- Weighing and Alloying --- p.44 / Chapter 2.1.3 --- Fluxing and Quenching --- p.45 / Chapter 2.2 --- Sample Preparation --- p.46 / Chapter 2.2.1 --- "Cutting, Grinding and Polishing" --- p.46 / Chapter 2.2.2 --- Etching --- p.47 / Chapter 2.2.3 --- Sample Preparation for Transmission Electron Microscopy Analysis --- p.48 / Chapter 2.3 --- Mechanical Tests --- p.49 / Chapter 2.3.1 --- Microhardness Test --- p.49 / Chapter 2.3.2 --- Compression Test --- p.50 / Chapter 2.4 --- Microstructural Analysis --- p.51 / Chapter 2.4.1 --- Scanning Electron Microscopy Analysis --- p.51 / Chapter 2.4.2 --- Transmission Electron Microscopy Analysis --- p.52 / Chapter 2.4.2.1 --- Indexing Diffraction Patterns --- p.52 / Chapter 2.4.2.2 --- Energy Dispersive X-Ray Analysis --- p.53 / Chapter 2.4.2.3 --- Electron Energy Loss Spectroscopy --- p.53 / Figures --- p.55 / References --- p.62 / Chapter Chapter 3: --- Dependence of the Mechanical Properties of FesoC2o Network Alloys on the Addition of Ni --- p.63 / Chapter 3.1 --- Abstract --- p.63 / Chapter 3.2 --- Introduction --- p.64 / Chapter 3.3 --- Experimental --- p.64 / Chapter 3.4 --- Results --- p.66 / Chapter 3.5 --- Discussions --- p.74 / Chapter 3.6 --- Conclusions --- p.79 / Tables --- p.80 / Figures --- p.82 / References --- p.100 / Bibliography --- p.101

Xu Yan = 納米銅(銅的氧化物)與三氧化二鋁復合物薄膜的製備和特性研究 / 許燕. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2003. / Includes bibliographical references (leaves 50-51). / Text in English; abstracts in English and Chinese. / Xu Yan = Na mi tong (tong de yang hua wu) yu san yang hua er lv fu he wu bo mo de zhi bei he te xing yan jiu / Xu Yan. / Abstract --- p.i / 摘要 --- p.ii / Acknowledgements --- p.iii / Table of Contents --- p.iv / List of Figures --- p.viii / List of Tables --- p.xi / Chapter CHAPTER 1 --- Introduction / Chapter 1.1 --- Nanostructured Materials --- p.1 / Chapter 1.2 --- Objective of this Work --- p.1 / Chapter CHAPTER 2 --- Background / Chapter 2.1 --- Correlation of AES-CuLMM spectrum and Cu nanocluster size --- p.3 / Chapter 2.1.1 --- Typical AES-CuLMM spectra --- p.3 / Chapter 2.1.2 --- A simplified model --- p.4 / Chapter 2.1.3 --- correlation of AES-CuLMM spectra and the simplified model --- p.4 / Chapter 2.2 --- Previous works --- p.5 / Chapter CHAPTER 3 --- Instrumentation / Chapter 3.1 --- Sputtering --- p.6 / Chapter 3.1.1 --- Principles of sputtering --- p.6 / Chapter 3.1.1.1 --- Concepts of sputtering --- p.6 / Chapter 3.1.1.2 --- Initiating the plasma --- p.8 / Chapter 3.1.1.3 --- Depositing a film onto the substrate --- p.8 / Chapter 3.1.2 --- Radio-frequency (RF) magnetron sputtering --- p.9 / Chapter 3.1.2.1 --- RF sputtering --- p.9 / Chapter 3.1.2.2 --- Magnetron Sputtering --- p.10 / Chapter 3.2 --- Deposition system --- p.10 / Chapter 3.2.1 --- Instrumentation --- p.11 / Chapter 3.2.1.1 --- Vacuum system --- p.11 / Chapter 3.2.1.2 --- Sputter target and power supplies --- p.12 / Chapter 3.2.1.3 --- Substrate mounting --- p.13 / Chapter 3.2.2 --- Experimental --- p.13 / Chapter 3.3 --- X-ray Photoelectron Spectroscopy (XPS) --- p.14 / Chapter 3.3.1 --- Basic Principles --- p.14 / Chapter 3.3.2 --- Instrumentation --- p.17 / Chapter 3.3.3 --- Qualitative and quantitative analysis --- p.17 / Chapter 3.3.3.1 --- Spectra interpretations --- p.17 / Chapter 3.3.3.2 --- X-ray emission line width --- p.18 / Chapter 3.3.3.3 --- Qualification --- p.18 / Chapter 3.3.3.3.1 --- Chemical composition --- p.18 / Chapter 3.3.3.3.2 --- Sputter depth profiling --- p.18 / Chapter 3.3.3.3.3 --- Auger parameter --- p.19 / Chapter 3.4 --- Transmission Electron Microscopy (TEM) --- p.19 / Chapter 3.4.1 --- An overview of TEM --- p.19 / Chapter 3.4.2 --- Imaging mode and diffraction mode --- p.21 / Chapter 3.4.3 --- Electron-Specimen interactions --- p.21 / Chapter 3.4.3.1 --- Elastic scattering --- p.22 / Chapter 3.4.3.2 --- Inelastic scattering --- p.22 / Chapter 3.4.4 --- Imaging mechanisms for TEM --- p.23 / Chapter 3.4.4.1 --- Mass-thickness contrast --- p.23 / Chapter 3.4.4.2 --- Diffraction contrast --- p.23 / Chapter 3.4.5 --- TEM sample preparation --- p.25 / Chapter CHAPTER 4 --- Chemical and Structure Characterization of Cu(CuOx)/Al2O3 Composite Thin Films / Chapter 4.1 --- Overview --- p.26 / Chapter 4.2 --- Results and discussions --- p.26 / Chapter 4.2.1 --- Set I: Achieving the stoichiometry of A1203 matrix --- p.26 / Chapter 4.2.2 --- Set II: keeping A1203 stoichiometry and studying on the correlation of CuLMM spectra and average Cu cluster size --- p.32 / Chapter 4.2.2.1 --- Chemical information obtained by XPS --- p.32 / Chapter 4.2.2.2 --- Nanostructure studied by TEM --- p.38 / Chapter 4.2.2.3 --- Mechanical properties inspected by nano-indentation --- p.43 / Chapter 4.2.2.4 --- Optical properties --- p.43 / Chapter 4.2.3 --- Set III: Duration of deposition --- p.44 / Chapter 4.2.4 --- Set VI: Pressure effect on the average size of Cu nanoclusters --- p.45 / Chapter CHAPTER 5 --- Conclusions --- p.48 / References --- p.50

Orientador: Edson Cocchieri Botelho / Coorientadora: Michelle Leali Costa / Banca: Luis Rogério de Oliveira Hein / Banca: Roberto Zenhei Nakazato / Banca: Lilia Muller Guerrini / Banca: Luiz Claudio Pardini / Resumo: Neste trabalho, compósitos de poli(sulfeto de fenileno) reforçados com nanotubos de carbono (MWCNT) puros e funcionalizados foram obtidos a partir da técnica de mistura em fusão. Os compósitos nanoestruturados foram caracterizados através de ensaios elétricos, térmicos, mecânicos reológicos e morfológicos. A condutividade elétrica do PPS apresentou um aumento de 11 e 9 ordens de magnitude quando 3,0 e 4,0% em massa de MWCNT puros e funcionalizados foram incorporados na matriz polimérica, respectivamente. Além disso, os limites de percolação elétrica encontrado para esses sistemas foram de 2,1 e 3,6 m/m%, o que sugere a formação de uma rede tridimensional condutora no interior da matriz polimérica. A temperatura máxima de cristalização do PPS apresentou aumentos de 19°C e 13°C devido a incorporação dos reforços puros (p-MWCNT) e funcionalizados (f-MWCNT), respectivamente, evidenciando o efeito nucleante das nanopartículas. A análise dinâmico mecânica mostrou um aumento no módulo de armazenamento e na temperatura de transição vítrea a partir do aumento da concentração de MWCNT, com um incremento maior para o sistema p-MWCNT/PPS. A temperatura máxima de degradação do PPS aumentou 14°C e 6°C devido a incorporação de 4,0 e 2,0% em massa de p-MWCNT e f-MWCNT, respectivamente, sugerindo a formação de sistemas termicamente mais estáveis. O módulo de armazenamento (G') do PPS apresentou um aumento de 2 ordens de magnitude quando 2,0 e 3,0% em massa de MWCNT puros e funcionalizados foram considerados, com a formação de uma estrutura interconectada de nanotubos, destacando o comportamento pseudoplástico das amostras. A formação de uma rede percolada de nanotubos foi atingida para concentrações de 1,5 e 2,3, m/m% em compósitos de p-MWCNT/PPS e f-MWCNT/PPS, respectivamente. As análises de microscopia ... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: In this work, pristine and functionalized multiwalled carbon nanotubes reinforced poly (phenylene sulfide) composites were successfully obtained by melt mixing technique. The nanostructured composites were characterized by means of electrical, thermal, mechanical, rheological, and morphological methods. The electrical conductivity of neat PPS showed an increase by 11 and 9 orders of magnitude when 3.0 and 4.0 wt% of pristine MWCNT and functionalized MWCNT were incorporated in polymeric matrix, respectively. Moreover, the electrical percolation thresholds found on these systems were 2.1 and 3.6 wt%, suggesting the formation of three-dimensional conductive network within the polymeric matrix. The maximum crystallization temperature of PPS increased by about 19°C and 13°C due the incorporation of pristine (p-MWCNT) and functionalized filler (f- MWCNT), demonstrating the nucleating effect of the nanoparticles. Dynamic mechanical analysis showed an increase in storage modulus and glass transition temperature, due the incorporation of p-MWCNT and f-MWCNT in PPS matrix. However, it is worth to mention that the increment was bigger in p-MWCNT/PPS system. The maximum degradation temperature of PPS increased by about 14°C and 6°C due to the incorporation of 4,0 and 2,0 wt% of p-MWCNT and f-MWCNT, respectively, suggesting the formation of more thermally stable systems. The storage modulus (G') of neat PPS presented an increase by 2 orders of magnitude when 2.0 and 3.0 wt% of pristine MWCNT and functionalized MWCNT were considered, with the formation of an interconnected nanotube structure, indicative of 'pseudo-solid-like' behavior. Percolation networks formed when the loading levels achieve up to 1.5 and 2.3 wt% for the composites with pristine MWCNT (p-MWCNT/PPS) and functionalized MWCNT (f-MWCNT/PPS), respectively. In addition, for ... (Complete abstract click electronic access below) / Doutor

Ho, Yee Man Martina = 硒化鎘三維納米結構之製作及其感應脫氧核糖核酸之應用潛能 / 何綺雯. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references. / Abstract also in Chinese. / Ho, Yee Man Martina = Xi hua ge san wei na mi jie gou zhi zhi zuo ji qi gan ying tuo yang he tang he suan zhi ying yong qian neng / He Qiwen. / Chapter Chapter 1 --- Introduction / Chapter 1 --- Photovoltaic properties of CdSe --- p.1 / Chapter 1.1 --- Quantum size effect --- p.1 / Chapter 1.2 --- Synthesis of CdSe nanostructures --- p.3 / Chapter 1.3 --- Electrochemical sensing of CdSe nanostructures --- p.4 / Chapter 1.3.1 --- Surface passivation and functionalization of CdSe nanostructures --- p.5 / Chapter 1.4 --- Electronic properties of nanocrystalline semiconductor electrode --- p.6 / Chapter 1.4.1 --- Band alignment --- p.6 / Chapter 1.4.2 --- Interfacial charge transfer process --- p.9 / Chapter 1.4.3 --- Surface traps and adsorbed molecules --- p.10 / Chapter 1.4.4 --- DNA molecules as a capping group --- p.11 / Chapter 1.5 --- Literatures review in DNA sensing --- p.12 / Chapter 1.6 --- Present study --- p.14 / Chapter 1.6.1 --- Objective --- p.14 / Chapter 1.6.2 --- General methodology --- p.15 / Chapter Chapter 2 --- Experimental / Chapter 2.1 --- Introduction into the instrumentation of this project --- p.21 / Chapter 2.2 --- CHI Electrochemical workstation --- p.22 / Chapter 2.2.1 --- Linear sweep voltammetry --- p.24 / Chapter 2.2.2 --- Cyclic voltammetry --- p.24 / Chapter 2.2.3 --- Multiple potential step --- p.25 / Chapter 2.3 --- CEM Microwave-assisted chemical synthesizer --- p.27 / Chapter 3.1 --- Morphological examination by scanning electron microscopy --- p.28 / Chapter 3.2 --- Elemental analysis by energy dispersive x-ray spectroscopy --- p.30 / Chapter 3.3 --- Crystal structure analysis by x-ray diffraction --- p.31 / Chapter 3.4 --- Surface compositional analysis by x-ray photoelectron spectroscopy --- p.32 / Chapter 3.5 --- Transmission electron microscopy --- p.34 / Chapter Chapter 3 --- Synthesis of 3D nanostructured CdSe multipod electrodes / Chapter 3.1 --- Introduction into the synthesis of CdSe MP electrode --- p.35 / Chapter 3.2 --- Recipe for the synthesis of CdSe NPs --- p.36 / Chapter 3.3 --- The synthesis of CdSe MPs --- p.37 / Chapter 3.3.1 --- Tuning the experimental parameters: Reaction temperature --- p.37 / Chapter 3.3.2 --- Tuning the experimental parameters: Reaction hold time --- p.46 / Chapter 3.3.3 --- Tuning in experimental parameters: Precursor molar ratio --- p.50 / Chapter 3.4 --- The fabrication of MP CdSe on a conductive substrate --- p.54 / Chapter 3.4.1 --- The electrodeposition of CdSe thin films on ITO/glass substrates --- p.55 / Chapter 3.4.2 --- The growth of CdSe MPs on CdSe/ ITO/glass --- p.57 / Chapter 3.5 --- The characterization of MP CdSe electrode --- p.57 / Chapter Chapter 4 --- Electrical and opto-electric characteristics of CdSe MP electrodes and their applications as platforms for the DNA recognition / Chapter 4.1 --- Introduction to the property characterization of CdSe MP electrodes --- p.62 / Chapter 4.2 --- DNA surface attachment --- p.64 / Chapter 4.2.1 --- Mechanism of DNA surface anchoring --- p.65 / Chapter 4.3 --- I-V characterization in PBS --- p.69 / Chapter 4.3.1 --- Experimental procedures of the I-V tests in PBS --- p.70 / Chapter 4.3.2 --- Results and discussions of I-V tests in PBS --- p.72 / Chapter 4.3.2.1 --- Exercising as-prepared CdSe MP electrode --- p.74 / Chapter 4.3.2.2 --- I-V characteristics of CdSe MP electrodes before and after ssDNA attachment --- p.75 / Chapter 4.3.2.3 --- I-V characteristics of CdSe MP electrodes before and after the dsDNA attachment --- p.76 / Chapter 4.3.2.4 --- "Photo-response of bare CdSe MP, ssDNA/CdSe MP and dsDNA/CdSe electrodes" --- p.77 / Chapter 4.4 --- "Photovoltaic I-V measurement in I3""/I"" redox electrolyte" --- p.79 / Chapter 4.4.1 --- Experimental procedures --- p.79 / Chapter 4.4.2 --- Results and discussions --- p.80 / Chapter 4.5 --- Possible application implied by the results --- p.88 / Chapter 4.5.1 --- DNA base pair mismatch identification --- p.91 / Chapter 4.5.2 --- Field-assisted DNA hybridization acceleration process --- p.92 / Chapter Chapter 5 --- Conclusions / Chapter 5.1 --- Conclusions --- p.95

Iu, Hei = 二維週期性金屬納米共振腔的理論研究 / 姚熙. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 89-91). / Abstracts in English and Chinese. / Iu, Hei = Er wei zhou qi xing jin shu na mi gong zhen qiang de li lun yan jiu / Yao Xi. / Chapter 1 --- Introduction --- p.1 / Chapter 2 --- Introduction to Surface Plasmon Polaritons --- p.3 / Chapter 2.1 --- The Maxwell´ةs Equations --- p.3 / Chapter 2.2 --- Photonic crystals --- p.5 / Chapter 2.3 --- Modeling Metal --- p.9 / Chapter 2.4 --- Surface plasmon polarition --- p.12 / Chapter 3 --- Rectangular Cavity --- p.17 / Chapter 3.1 --- Basic simulation cell setup --- p.17 / Chapter 3.2 --- Method of mode identification --- p.18 / Chapter 3.2.1 --- Dispersion relation calculation --- p.18 / Chapter 3.2.2 --- Reflection spectra --- p.19 / Chapter 3.3 --- Results and discussions --- p.20 / Chapter 4 --- Nano-bottle cavity --- p.25 / Chapter 4.1 --- Cylindrical cavity --- p.25 / Chapter 4.1.1 --- Dispersion relations calculation --- p.25 / Chapter 4.1.2 --- Field pattern calculation --- p.29 / Chapter 4.2 --- Nano-bottle cavity --- p.46 / Chapter 4.2.1 --- The effect of the bottleneck on (0，1) mode --- p.47 / Chapter 4.2.2 --- The effect of aperture size on (0，1) mode --- p.58 / Chapter 4.2.3 --- The effect of the depth of cavities on (0，1) mode --- p.62 / Chapter 4.2.4 --- "The effect of aperture size on (-1,0) mode" --- p.63 / Chapter 4.3 --- Discussions --- p.64 / Chapter 4.4 --- Verified with experimental results --- p.68 / Chapter 5 --- Aspect ratio --- p.71 / Chapter 5.1 --- Simulation structure --- p.72 / Chapter 5.2 --- Aspect ratio S = 2 --- p.73 / Chapter 5.3 --- The effect of aspect ratio --- p.74 / Chapter 5.3.1 --- Orientation dependence of the resonant mode --- p.74 / Chapter 5.3.2 --- Excitation frequency of the resonant mode --- p.75 / Chapter 5.4 --- Field location and strength --- p.76 / Chapter 5.5 --- Discussions --- p.77 / Chapter 5.6 --- Comparison with experimental results --- p.79 / Chapter 6 --- Conclusions and future works --- p.83 / Chapter 6.1 --- A possible new mode excitation --- p.84 / Chapter 6.2 --- Cavities with aspect ratio under p-polarized light --- p.86 / Bibliography --- p.89 / Chapter A --- Computational Simulation --- p.92 / Chapter A.l --- Finite-Difference Time-Domain --- p.92 / Chapter A.2 --- Computational grid --- p.93 / Chapter A.3 --- Boundary Condition --- p.93 / Chapter A.4 --- Source --- p.94 / Chapter A.5 --- Field strength --- p.94

O estudo e conhecimento do magnetismo é muito importante para a nossa sociedade, devido ao grande número de aplicações que envolvem as propriedades magnéticas. Por isso, umas das problemáticas vigentes em física do estado sólido é o estudo, conhecimento e controle deste tipo de propriedades em diferentes tipos de materiais, dentre os quais encontramse materiais de dimensões nanométrica como nanofios e nanotubos. No presente trabalho temos como objetivo a realização de estudos sobre propriedades magnéticas tais como anisotropia e magnetização em sistemas formados por nanofios de Ni eletrodepositados em alumina nanoporosa, e nanotubos de NiB crescidos em membrana porosa de policarbonato. A caracterização microestrutural das amostras de nanofios de Ni foi realizada por difração de raios X, microscopia eletrônica de varredura, microscopia de força atômica e microscopia eletrônica de transmissão de alta resolução. Os resultados mostraram que os nanofios de Ni tinham diâmetros de aproximadamente 60nm, são policristalinos com estrutura predominante fcc, embora também foram encontrados grãos minoritários de estrutura hcp. O tamanho de grão esteve na faixa entre 5 e 15 nm, aproximadamente. Por outro lado, os nanotubos de NiB estavam formados por uma liga amorfa de composição Ni80B20, com a presença de uma porção minoritária de pequenos cristalitos de NiB. Os nanotubos tinham comprimentos de 20 ?m aproximadamente, diâmetro externo de 400 nm e espessuras das paredes na faixa entre 50 e 160 nm. Todas as amostras foram caracterizadas magneticamente a partir de medidas de ciclos de histerese, curvas de remanências isotérmica e desmagnetizante (para a obtenção de curvas ?M) e curvas de inversão de primeira ordem (para o cálculo das distribuições FORC). Um novo modelo fenomenológico para estudar anisotropias, desenvolvido em nosso grupo de pesquisa, permitiu a determinação das constantes de anisotropias K1 (constante de anisotropia magnetocristalina de segunda ordem) e Ku (constante de anisotropia uniaxial) nos sistemas de nanofios de Ni. Os resultados mostraram que a constante de anisotropia K1 cresce conforme aumenta o comprimento dos nanofios, ficando próximo e até superior ao valor correspondente ao Ni massivo. O processo de nucleação e propagação de paredes de domínios transversais foi confirmado como mecanismo de inversão da magnetização nos nanofios, por meio da aplicação de um modelo analítico que determina o campo de nucleação do sistema. A importância das interações dipolares no comportamento magnético global destes sistemas foi evidenciada pela determinação das curvas ?M e das distribuições FORC. No caso dos nanotubos de NiB foi determinado que o mecanismo de inversão da magnetização corresponde à nucleação e propagação de vórtices, como acontece em outros sistemas similares. No entanto, foi observado que a espessura da parede do tubo tem um papel importante, porque foi verificado que a coercividade dos nanotubos decresce se a parede deles é suficientemente grossa em comparação com o tamanho de parede de domínio do Ni. Também para estes sistemas, as curvas ?M e das distribuições FORC mostraram a predominância de interações desmagnetizantes. / The study and knowledge of magnetism is very important for our society, due to the large number of applications involving magnetic properties. Therefore, one of the current problems in solid state physics is the study, knowledge and control of this type of properties in different types of materials, among which are materials of nanometric dimensions such as nanowires and nanotubes. In the present work, we have carried out studies on magnetic properties such as anisotropy and magnetization in systems formed by Ni nanowires electrodeposited in nanoporous alumina, and NiB nanotubes grown in polycarbonate porous membrane. The microstructural characterization of Ni nanowire samples was performed by X-ray diffraction, scanning electron microscopy, atomic force microscopy and high resolution transmission electron microscopy. The results showed that Ni nanowires had diameters of approximately 60 nm, are polycrystalline with predominant fcc structure, although a minor fraction of hcp structure was also found. The grain size was in the range between 5 and 15 nm, approximately. On the other hand, the NiB nanotube samples were formed by an amorphous alloy of Ni80B20 composition, with the presence of a minor portion of small NiB crystallites. The nanotubes had lengths of approximately 20 µm, external diameter of 400 nm and wall thicknesses in the range of 50 to 160 nm. All the samples were magnetically characterized by measurements of hysteresis cycles, isothermal and demagnetizing remanence curves (to obtain ?M curves) and first-order reversal curves (for calculating FORC distributions). A new phenomenological model to study anisotropies, developed in our research group, allowed the determination of the anisotropy constants K1 (second order magnetocrystalline anisotropy constant) and Ku (uniaxial anisotropy constant) in the Ni nanowire systems. The results showed that the anisotropy constant K1 increases as the nanowire length increases, being close to and even higher than the Ni bulk value. The process of nucleation and propagation of transverse domain walls was confirmed as the mechanism for magnetization reversal in nanowires. This result as obtained by applying an analytical model that determines the nucleation field of the system. The importance of the dipolar interactions on the global magnetic behavior for these systems was evidenced by the determination of the ?M curves and the FORC distributions. In the case of NiB nanotubes, it was determined that the magnetization reversal mechanism corresponds to the nucleation and propagation of vortices, as in other similar systems. However, it has been observed that the wall thickness of the tube plays an important role because it has been found that the coercivity of the nanotubes decreases if their walls are thick enough compared to the Ni domain wall size. Also, for these systems, the ?M curves and the FORC distributions showed the predominance of demagnetizing interactions.

Surface passivation of semiconductor quantum dots is essential to preserve their efficient and robust light emitting properties. By using a lattice matched (mismatch = 0.5%) lead halide perovskite matrix, we achieve shell-like passivation of lead sulfide QDs in crystalline films, leading to efficient infrared light emission. These structures are made from a simple one-step spin coating process of an electrostatically stabilized colloidal suspension. Photoluminescence and transient absorption spectroscopy indicate rapid energy transfer between the perovskite matrix and the QDs, suggesting an interface with few trap states. In addition to housing the efficient infrared QD emitters, lead halide perovskites themselves have good carrier mobilities and low trap densities, making these solution-processable heterostructures an attractive option for electrically pumped light emitting devices. The highest performing quantum dots for visible light applications are CdE (E=chalcogenide) core/shell heterostructures. Again, surface passivation plays a huge role in determining the brightness and robustness of visible QD emitters. Multilayer shell passivation is usually used to produce the highest quantum yield particles. Surface trap states are shown to be detrimental to luminescence output, even in thick-shelled particles. Spherical quantum wells allow for thicker shells and with good surface passivation, show promising reduction of biexciton auger recombination, as measured by a time correlated single photon counting (TCSPC) microscope. TCSPC methods were used to diagnose and identify QD architectures for LED applications and explore fundamental recombination dynamics using photon antibunching measurements, and statistical analysis of blinking traces.Introducing new surfaces onto graphitic substrates can be a useful for introducing new electronic properties, patterning device-specific geometries, or appending molecular catalysts. Metal nanoparticles were used to act as a catalyst for the gasification and etching of graphite and graphene. Several methods of controlling the initiation, propagation, and density of these trenches were explored. Patterning defects helped control where initiation occurred, while faceting existing defect sites could also enable more facile initiation and control the direction at the beginning of etching, due to the wetting mechanism of particle movement. Patterning the metal also was shown as a promising avenue to limit unwanted gasification and promote etching in specific, patterned regions. Surface functionalization using reactive gases was performed and characterized with outlook for future experiments.

This dissertation focuses on the synthesis and characterization of glyconanomaterials, as well as their applications in studying carbohydrate-protein interactions. A new and versatile method for coupling underivatized carbohydrates to nanomaterials including gold and silica nanoparticles was developed via the photochemically induced coupling reaction of perfluorophenylazide (PFPA). A wide range of carbohydrates including mono-, oligo- and poly-saccharides were conjugated to the nanoparticles with high yields and efficiency. New analytical methods were developed to determine the binding affinities of glyconanoparticles (GNPs) with lectins; these include fluorescence-based competition assay, dynamic light scattering (DLS) and isothermal titration calorimetry (ITC). Results showed that the multivalent presentation of carbohydrate ligands significantly enhanced the binding affinity of GNPs by several orders of magnitude compared to the free ligands. Systematic studies were carried out to investigate the impact of ligand presentation, i.e., the type and length of spacer linkage, the ligand density and the nanoparticle size on the binding affinity of the resulting glyconanoparticles. We used gold GNPs to study interactions with anti-HIV lectin cyanovirin-N (CV-N), and dye-doped silica nanoparticles for labeling glyans and developing high-throughput screening technique.

While silicon has long been utilized for its electronic properties, its use as an optical material has largely been limited due to the poor efficiency of interband transitions. However, discovery of visible photoluminescence (PL) from nanocrystalline silicon in 1990 triggered many ensuing research efforts to optimize PL from nanocrystalline silicon for optical applications. Currently, use of photoluminescent silicon nanoparticles (Si NPs) is commercially limited by: 1) the instability of the energy and intensity of the PL, and 2) the low quantum yield of interband PL from Si NPs. Herein, red-emitting, hydrogen-passivated silicon nanoparticles (H-Si NPs) were synthesized by thermally-induced disproportionation of a HSiCl3-derived (HSiO1.5)n polymer. The H-Si NPs produced by this method were then subjected to various chemical and physical environments to assess the long-term stability of the optical properties as a function of changing surface composition. This dissertation is intended to elucidate correlations between the reported PL instability and the observed changes in the Si NP surface chemistry over time and as a function of environment. First, the stability of the H-Si NP surface at slightly elevated temperatures towards reactivity with a simple alkane was probed. The H-Si NPs were observed by FT-IR spectroscopy to undergo partial hydrosilylation upon heating in refluxing hexane, in addition to varying degrees of surface oxidation. The unexpected reactivity of the Si surface in n-hexane supports the unstable nature of the H-Si NP surface, and furthermore implicates the presence of highly-reactive Si radicals on the surfaces of the Si NPs. We propose that reaction of alkene impurities with the Si surface radicals is largely responsible for the observed surface alkylation. However, we also present an alternate mechanism by which Si surface radicals could react with alkanes to result in alkylation of the surface. Next, the energy and intensity stability of the interband PL from H-Si NPs in the presence of a radical trap was probed. Upon addition of (2,2,6,6,-tetramethyl-piperidin-1-yl)oxyl (TEMPO), the energy and intensity of the interband transition was observed to change over time, dependent on the reaction conditions. First, when the reaction occurred at 4ºC with minimal light exposure, the interband transition exhibited a gradual hypsochromic shift to between 595 nm and 655 nm, versus the λmax of the original low energy emission peak at 700 nm, depending on the amount of TEMPO in the sample. Second, when the reaction proceeded at room temperature with frequent exposure to 360 nm irradiation, the original interband transition at 660 nm was quenched while a new peak at 575 nm developed. Based on all the data collected and analyzed, we assign the 595 -- 655 nm transition as due to interband exciton recombination from Si NPs with reduced diameters relative to the original Si NPs. We furthermore assign the 575 nm transition as due to an oxide-related defect state resulting from rapid oxidation of photo-excited Si NPs.

Quantum Dots (QD) have become a commercial reality for tunable displays and light-emitting diodes. The Department of Energy believes further improvements in efficacy and stability will allow for widespread adoption of solid-state lighting in the United States. QD geometric and compositional architecture, crystal phase and surface chemistry are arguably some of the important aspects governing QD performance in these applications. Chapter I outlines the efforts of QD design, encapsulation and performance for phosphor converted, “on-chip” LEDs. Cadmium chalcogenide QDs with a quantum well geometry and ZnS encapsulation (CdS/CdSxSe1-x/CdS/ZnS) resist photoluminescence bleaching on chip under harsh accelerated ageing tests. Trends in device performance are linked primarily to success of ZnS passivation. Chapter II presents findings regarding crystal structure control (Zinc Blende vs Wurtzite) for CdX (X = S, Se) systems by focusing on crystal phase conversion. The ZB to W transition for CdX is shown to be size, material and surfactant dependent. Chapter III focuses on expanding the precursor compound library for CdSe with aryl substituted cyclic selenones (imidazole and pyrimidine-based compounds). These molecules are shown to react sluggishly at ZB synthetic conditions and that the rate is heavily influenced by compound sterics. Chapter IV presents the findings of a metal carboxylate displacement study on PbS NCs with various L-type ligands. Upon displacement and purification with N,N,N′,N′-tetramethylethylene-1,2-diamine, tri-n-butylamine, and n-octylamine, oriented attachment occurs along the 100 plane and with bis(dimethylphosphino)ethane and tri-n-butylphosphine, attachment is suppressed. This difference allows for the study of ligand density dependent optical properties without the confounding attachment of nanocrystals in solution. A decreasing trend of time resolved photoluminescence lifetime values as a function of ligand density is observed.