Thesis (Ph. D.)--University of California, San Diego, 2003. / Vita. Includes bibliographical references.

Tin-doped indium oxide (ITO) has been widely used for various optoelectronic devices such as display panels, light-emitting diodes and solar cells due to its unique optical and electrical properties. Thin ITO films can be fabricated by a number of methods such as molecular beam epitaxy (MBE), laser ablation, dc sputtering, e-beam deposition, vapor phase deposition, electrochemical deposition and hydrothermal method. Apart from the conventional thin film form, one dimensional ITO nanorods or nanowires are attracting much research interest due to their high aspect ratio and large surface to volume ratio. For instance, a network made of ITO nanowires can exhibit high transparency (over 95 %) and high flexibility without losing its conducting property as reported recently. This network can be potentially used for flexible photovoltaic devices. In this study, ITO nanorods or nanowires were fabricated using the vapor deposition, dc sputtering and e-beam deposition. The use of short ITO nanorods (100 nm) on glass and commercial ITO substrates as bottom electrodes improving the charge collection of bulk heterojunction organic solar cells had been demonstrated. The morphology of the ITO nanostructures was studied by scanning electron microscope (SEM) and transmission electron microscope (TEM). The crystal structure and growth direction were studied by x-ray diffraction (XRD) and selected area electron diffraction (SAED), respectively. Optical properties were examined using transmission and photoluminescence measurements. The performance of the organic solar cells was examined using the I-V characteristics and external quantum efficiency (EQE) measurements. The growth mechanism of the ITO nanowires using different fabrication methods was discussed. The effects of the substrate temperature, oxygen content, choice of substrate and evaporation rate on the morphology, transmittance and sheet resistivity were investigated. When short ITO nanorods were incorporated into the bulk heterojunction organic solar cells, a significant improvement of the power conversion efficiency (PCE) was observed. The higher efficiency of the studied solar cells was attributed to the improved charge collection. / published_or_final_version / Physics / Doctoral / Doctor of Philosophy

Powder neutron diffraction and magnetic susceptibility measurements of the antiferromagnetic phases of Mn_xNi_1-xO,Mn_xCo_1-xO, (Mn_xFe_1-x)_zO and (Co_xFe_1-x)_zO reveal that the magnetic moments of unlike ions are always effectively collinear, despite the presence of competing anisotropies. The magnetic moments of Mn_xNi_1-xO (x = 0.24,0.48 and 0.77) at 5K are confined to (111) planes by dipole-dipole forces, and the small trigonal exchangestrictions are the products of opposed antiferromagnetic Mn²⁺-Mn²⁺ and ferromagnetic Ni²⁺-Mn²⁺ nearest neighbour interactions. In Mn_xCo_1-xO (x = 0.05, 0.10, 0.25,0.36) at 5K, the orbital degener- acy of Co²⁺ is removed by both Jahn-Teller (J.T) and spin-orbit coupling (S.O) mechanisms, leading to orthorhombic or triclinic symmetries and partially quenched Co²⁺ moments. Monoclinic symmetry is observed for 0.51<x<0.67, and Jahn-Teller stabilisations and spin-only Co²⁺ moments are evident. The cobalt concentration is too small to support a cooperative J.T stabilisation in Mn_0.83Co_0.17O, where a magnetostriction (c/a < 1) is observed (in agreement with previous AFMR results). Previous results for Co_xNi_1-xO, and those for Mn_xCo_1-xO, (Mn_xFe_1-x)_zO (x = 0.05, 0.1, 0.12, 0.23, 0.36,0.56,0.66,0.89) and (Co_xFe_1-x)_zO (x = 0.04,0.12,0.50,0.63,0.81) at 5K indicate that the anisotropy order for the iron group monoxides is CoO>MnO»Fe_zO≈NiO. The weak trigonal anisotropy of Fe²⁺ correlates with the near-cubic symmetries of (Co_xFe_1-x)_z( (x = 0.04,0.12) and (Mn_xFe_1-x)_zO (0.1<x<0.66), and a tetragonal (c/a>1) magnetostriction of Fe²⁺ is observed in (Co_xFe_1-x)_zO with x > 0.5. Measurements of vacancy-ferric interstitial ratios for (Mn_xFe_1-x)_zO and (Co_xFe_1-x)_zO suggest that non-stoichiometry is accommodated by 6:2 or 8:3 defect clusters in the former, and by larger units in the latter. The observed magnetic moments of defective samples are normally larger than those calculated according to a previous model for Fe_zO, and require the postulation of partial antiferromagnetic order around the clusters. The room temperature Mossbauer effect parameters of (Mn_xFe_1-x)_zO (0<x<0.975,0.910<z<1.0) indicate that while Fe²⁺ and Mn²⁺ ions are randomly distributed over octahedral sites, ferric ions are localised around defect clusters.

Single-walled metal oxide nanotubes have emerged as an important class of 'building block' materials for molecular recognition-based applications in catalysis, separations, sensing, and molecular encapsulation due to their vast range of potentially accessible compositions and structures, and their unique properties such as well-defined wall structure and porosity, tunable dimensions, and chemically modifiable interior and exterior surfaces. However, their widespread application will depend on the development of synthesis processes that can yield structurally and compositionally well-controlled nanotubes. Moreover, such processes should be amenable to scale-up and preferably operate via benign chemistries under mild conditions. There is currently very little knowledge on the molecular-level 'design rules' underlying the engineering of such materials. The capability to engineer single-walled tubular materials would lead to a range of structures, with novel properties relevant to diverse applications. In this thesis, main objectives are to discover the first molecular-level mechanistic framework governing the formation and growth of single-walled metal-oxide nanotubes, apply this framework to demonstrate the engineering of nanotubular materials of controlled dimensions, and to progress towards a quantitative multiscale understanding of nanotube formation. The class of aluminosilicate (AlSiOH)/germanate (AlGeOH) nanotubes are of particular interest to us, and serve as the exemplar materials for single-walled metal oxide nanotubes. They can be synthesized in pure form from inexpensive and easily accessible reactants at low temperatures (95 ˚C) from aqueous solutions. The synthesis of nanotubes occurs on a time-scale of hours to days, making them an ideal model system to study the nanotube formation mechanism. In Chapter 2, the identification and elucidation of the mechanistic role of molecular precursors and nanoscale (1-3 nm) intermediates with intrinsic curvature, in the formation of single-walled aluminosilicate nanotubes is reported. The structural and compositional evolution of molecular and nanoscale species over a length scale of 0.1-100 nm, are characterized by electrospray ionization (ESI) mass spectrometry, and nuclear magnetic resonance (NMR) spectroscopy. DFT calculations revealed the intrinsic curvature of nanoscale intermediates with bonding environments similar to the structure of the final nanotube product. It is shown that curved nano-intermediates form in aqueous synthesis solutions immediately after initial hydrolysis of reactants at 25 ˚C, disappear from the solution upon heating to 95 ˚C due to condensation, and finally rearrange to form ordered single-walled aluminosilicate nanotubes. Integration of all results leads to the construction of the first molecular-level mechanism of single-walled metal oxide nanotube formation, incorporating the role of monomeric and polymeric aluminosilicate species as well as larger nanoparticles. Then, in Chapter 3, new molecular-level concepts for constructing nanoscopic metal oxide objects are demonstrated. The diameters of metal oxide nanotubes are shaped with Ångstrom-level precision by controlling the shape of nanometer-scale precursors. The subtle relationships between precursor shape and structure and final nanotube curvature are measured (at the molecular level). Anionic ligands (both organic and inorganic) are used to exert fine control over precursor shapes, allowing assembly into nanotubes whose diameters relate directly to the curvatures of shaped precursors. Having obtained considerable insight into aluminosilicate nanotube formation, in Chapter 4 the complex aqueous chemistry of nanotube-forming aluminogermanate solutions are examined. The aluminogermanate system is particularly interesting since it forms ultra-short nanotubes of lengths as small as ~20 nm. Insights into the underlying important mechanistic differences between aluminogermanate and aluminosilicate nanotube growth as well as structural differences in the final nanotube dimensions are provided. Furthermore, an experimental example of control over nanotube length is shown, using the understanding of the mechanistic differences, along with further suggestions for possible ways of controlling nanotube lengths. Ultimately, it is desired to produce the single-walled aluminosilicate nanotubes on a larger scale (e.g., kilogram or ton scales) for technological application. However, a quantitative multiscale understanding of nanotube growth via a detailed growth model, is critical to be able to predict and control key properties such as the length distribution and concentration of the nanotubes. Such a model can then be used to design liquid-phase reactors for scale-up of nanotube synthesis. In Chapter 5, a generalized kinetic model is formulated to describe the reactions leading to formation and growth of single-walled metal oxide nanotubes. This model is capable of explaining and predicting the evolution of nanotube populations as a function of kinetic parameters. It also allows considerable insight into meso/microscale nanotube growth processes. For example, it shows that two different mechanisms operate during nanotube growth: (1) growth by precursor addition, and (2) by oriented attachment of nanotubes to each other. In Chapter 6, a study of the structure of the nanotube walls is presented. It has usually been assumed in the literature that the nanotube wall is free of defects. A combination of 1H-29Si and 1H-27Al FSLG-HETCOR, 1H CRAMPS, and 1H-29Si CP/MAS NMR experiments were employed to evaluate the proton environments around Al and Si atoms during nanotube synthesis and in the final structure. The HETCOR experiments allowed to track the evolving Si and Al environments during the formation of the nanotubes from precursor species, and relate them to the Si and Al coordination environments found in the final nanotube structure. The 1H CRAMPS spectra of dehydrated aluminosilicate nanotubes revealed the proton environments in great detail. Integration of all the NMR results allows the structural assignment of all the chemical shifts and the identification of various types of defect structures in the aluminosilicate nanotube wall. In particular, five main types of defect structures are identified arising from specific atomic vacancies in the nanotube structure. It is estimated that ~16% of Si atoms in the nanotube inner wall are involved in a defect structure. The characterization of the detailed structure of the nanotube wall is expected to have significant implications for its chemical properties and applications. Chapter 7 contains concluding remarks, as well as suggestions for future directions in the engineering of single-walled nanotube materials.

Thesis (Ph. D.)--University of Hong Kong, 2010. / Includes bibliographical references. Also available in print.

Thesis (Ph. D.)--West Virginia University, 2004. / Title from document title page. Document formatted into pages; contains xiv, 138 p. : ill. (some col.). Vita. Includes abstract. Includes bibliographical references.

Thesis (doctoral)--Helsinki University of Technology, 2002. / Includes bibliographical references. Also available on the World Wide Web.

Thesis (Ph.D.)--University of Melbourne, The School of Chemistry, 2010. / Typescript. Includes bibliographical references.

Orientador: Paulo Noronha Lisboa Filho / Banca: Paulo Tambasco de Oliveira / Banca: Angela Maria Moraes / Banca: Ana Paula Ramos / Banca: Valdecir Farias Ximenes / Resumo: O titânio e suas ligas são utilizados em diversas aplicações, dentre elas em implantes ortopédicos e dentários devido à sua reconhecida biocompatibilidade. No entanto, falhas e subsequentes efeitos colaterais clínicos ainda são recorrentes em implantes. Neste contexto, melhorias podem ser alcançadas projetando biomateriais nos quais o bulk e a superfície do titânio são independentemente modificadas. Deste modo, filmes finos nanoestruturados de óxidos metálicos, tais como TiO2 e ZnO, podem melhorar as propriedades físico-químicas, a biocompatibilidade e a resistência à corrosão dos implantes de titânio. Além disso, a conjugação de biomoléculas, como peptídeos derivados da proteína da matriz dentinária 1 (DMP1), na superfície dos óxidos metálicos pode melhorar sua bioatividade, acelerando o processo de osteointegração. Dessa forma, o objetivo deste trabalho foi funcionalizar óxidos metálicos com diferentes moléculas bifuncionais e investigar as propriedades físico-químicas de grupos silano, amino, ácido carboxílico, tiol e hidroxila que atuaram como espaçadores entre os óxidos metálicos e os peptídeos da DMP1. Além disso foram realizadas análises de biocompatibilidade, mineralização, resistência à corrosão e à tribocorrosão das superfícies bio-funcionalizadas com os peptídeos da DMP1. Neste trabalho, filmes de TiO2 e ZnO nanométricos foram sintetizados pelo método sol-gel e depositados pela técnica spin coating em substratos de titânio. Posteriormente, os filmes finos de óxidos... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Titanium and its alloys are used in a variety of applications, including orthopedic and dental implants because of their recognized biocompatibility. However, failures and subsequent clinical side effects are still recurrent in implants. In this context, improvements can be achieved by designing biom aterials in which the bulk and surface of the titanium are independently tailored . Thus, nanostructured metal oxides thin films, such as TiO 2 and ZnO, can improve the physicochemical properties, biocompatibility and corrosion resistance of titanium implant s. In addition, the conjugation of biomolecules, such as peptides derived from the dentin matrix 1 protein (DMP1), on the surface of the metal oxides can improve their bioactivity, accelerating the os t eointegration process. Therefore, the objective of thi s work was to functionalize metal oxides with different bifunctional molecules and to investigate the physicochemical properties of silane, amino, carboxylic acid, thiol and hydroxyl groups that act as spacers between metal oxides and DMP1 peptides. In add ition, biocompatibility, mineralization, corrosion and tribocorrosion resistance of the bio - functionalized surfaces were performed. In this work, nanosized TiO 2 and ZnO thin films were synthesized by sol - gel method and deposited by spin coating technique o n titanium substrates. Subsequently, the thin films of metal oxides were functionalized with (3 - aminopropyl) trimethoxysilane (APTMS), 3 - (4 - aminophenyl) pr... (Complete abstract click electronic access below) / Doutor

The adsorption of SO2 by metal oxides suspended in decane were studied by calorimetric titration. The adsorption per surface area decreases in order CuO > Cu2O > Fe2O3 > V2O5. An Andersen High Volume sampler was used to obtain particulate samples from five sites in Utah County. Particulate sulfur (IV) and sulfur (VI) was analyzed by thermometric titration with K2Cr2O7 and by a direct injection enthalpimetric determination using BaCl2. Results show that little oxidation of the S(IV) occurs after it is released from the Kennecott smelter stack.