This dissertation comprises experimental studies on the synthesis and applications of metallic nanoshells. These are a class of nanoparticles composed of a dielectric core and a thin metallic shell. Metallic nanoshells play an important role in nanotechnology, particularly in nanomedicine, due to their peculiar optical properties. The overall objectives of the dissertation were to improve the fabrication of these nanoparticles, and to demonstrate new applications of these materials in cancer research and spectroscopy. The fabrication of nanoshells is a multi-step process. Previously to our work, the procedures for the synthesis of nanoshells reported in the literature lacked systematic characterization of the various steps. The procedure was extremely time-consuming and the results demonstrated a high degree of size variation. In Chapter 3, we have developed characterization tools that provide checkpoints for each step of the synthesis. We demonstrated that it is possible to control the degree of coverage on the shell for a fixed amount of reagents, and also showed important differences on the shell growth phase for gold and silver. The synthetic optimization presented in Chapter 3 led to an overall faster protocol than those previously reported. Although the improvements presented in Chapter 3 led to a higher degree of control on the synthesis of nanoshells, the variations in the resulting particle population were still too large for applications in single particle spectroscopy and imaging. In Chapter 4, the synthesis was completely reformulated, aiming to narrow the size distribution of the nanoshell colloids. Through the use of a reverse microemulsion, we were able to fabricate ultramonodisperse silica (SiO2) cores, which translate into nanoshell colloids with narrow extinction bands that are comparable to those of a single nanoshell. We then fabricate a library of colloids with different core sizes, shell thicknesses and composition (gold or silver). The localized surface plasmon resonance (LSPR) of these colloids span across the visible range. From this library, two nanoshells (18nm silver on a 50nm SiO2 core, and 18nm gold on a 72nm SiO2 core) were selected for a proof of principle cell imaging experiment. The silver nanoshells were coated with a nuclear localization signal, allowing it to target the nuclear membrane. The gold nanoshells were coated with an antibody that binds to a receptor on the plasma membrane of MCF-7 human breast cancer cells. The nanoshells were easily distinguishable by eye in a dark field microscope and successful targeting was demonstrated by hyperspectral dark field microscopy. A comparison was made between fluorescent phalloidin and nanoshells, showing the superior photostability of the nanoparticles for long-term cell imaging. The results from Chapter 4 suggest that the nanoshells obtained by our new synthetic route present acceptable particle-to-particle variations in their optical properties that enables single particle extinction spectroscopy for cell imaging. In Chapter 5 we explored the use of these nanoshells for single-particle Surface-enhanced Raman spectroscopy (SERS). Notice that particle-to-particle variations in SERS are expected to be more significant than in extinction spectroscopy. This is because particle-to-particle SERS variabilities are driven by subtle changes in geometric parameters (particle size, shape, roughness). Two types of gold nanoshells were prepared and different excitation wavelengths (λex) were evaluated, respective to the LSPR of the nanoshells. Individual scattering spectra were acquired for each particle, for a total of 163 nanoshells, at two laser excitation wavelengths (632.8 nm and 785 nm). The particle-to-particle variations in SERS intensity were evaluated and correlated to the efficiency of the scattering at the LSPR peak. Chapter 6 finally shows the application of gold nanoshells as a platform for the direct visualization of circulating tumor cells (CTCs). 4T1 breast cancer cells were transduced with a non-native target protein (Thy1.1) and an anti-Thy1.1 antibody was conjugated to gold nanoshells. The use of a transduced target creates the ideal scenario for the assessment of nonspecific binding. On the in vitro phase of the study, non-transduced cells were used as a negative control. In this phase, parameters such as incubation times and nanoshell concentration were established. A murine model was then developed with the transduced 4T1 cells for the ex vivo portion of the work. Non-transduced cells were implanted in a control group. Blood was drawn from mice in both groups over the course of 29 days. Antibody-conjugated nanoshells were incubated with the blood samples and detection of single CTCs was achieved in a dark field microscope. Low levels of nonspecific binding were observed in the control group for non-transduced cells and across different cell types normally found in peripheral blood (e.g. lymphocytes). All positive and negative subjects were successfully identified. Chapter 7 provides an outlook of the work presented here and elaborates on possible directions to further develop the use of nanoshells in bioapplications and spectroscopy. / Graduate / 2019-05-03

Silicon monoxide maser emission has been detected in many evolved stars in circumstellar envelopes in different vibrationally-excited rotational transitions. It is considered a good tracer to study the dynamics in a region close to the photosphere of the star. We present multi-epoch, total intensity, high-resolution images of 43 GHz, v=1, J=1-0 SiO maser emission toward the Mira variable R Cas. In total we have 23 epochs of data for R Cas at approximate monthly intervals over an optical pulsation phase range of φ = 0.158 to φ = 1.782. These maps show a ring-like distribution of the maser features in a shell, which is assumed to be centred on the star at average radius of 1.6 → 2.3 times the radius of star, R⋆. It is clear from these images that the maser emission is significantly extended around the star. At some epochs a faint outer arc can be seen at about 4 R⋆. The intensity of the emission waxes and wanes during the stellar phase. Some maser features are seen infalling as well as outflowing. We have made initial comparisons of our data with models by Gray et al. (2009). We have investigated the polarization morphology by mapping the linear and circular polarization of SiO masers in the v=1, J=1-0 transition. We found that some of the polarization vectors are either tangential or radial, which indicate a bimodal structure of the linear polarization morphology. Other angles can be seen as well. This is consistent with a radial, stellar-centred magnetic field in the SiO maser shell. We found in some isolated features the fractional linear polarization exceeds 100%. In other features, the polarization angle abruptly flips by 90◦. We found that our data are in the regime that the Zeeman splitting rate g is much greater than the stimulated emission rate R which in turn is greater than the decay rate , which indicates that the solution of Goldreich et al. (1973) can be applied.

The research described here encompasses several different aspects of lithium ion battery operation including deep eutectic electrolytes, manganese trapping evaluation, silicon monoxide anodes, and in-situ NMR development under both static and spinning conditions. Individually, the results of these investigations as contained within the corresponding chapters contribute valuable insight. Collectively, they represent a snapshot into the numerous different ways in which nuclear magnetic resonance spectroscopy is applicable to lithium ion battery characterization. For instance, the deep eutectic electrolytes thus studied were amenable to diffusion coefficient characterization via the 1H, 7Li and 19F nuclei. This provided dynamical information on the anion, cation and neutral component and lent itself well towards parameterization of molecular dynamics simulations. The results thus obtained were useful in describing this relatively understudied class of electrolytes. Another example is that of the evaluation of manganese trapping. In this context 7Li NMR measurements were used to investigate the competitive inhibition of manganese trapping in crown ethers by lithium. Candidate crown ethers were thus evaluated for their ability to trap Mn2+ and Mn3+ in a lithium rich environment. Given the detrimental effects that manganese dissolution from cathode materials has on cycle life performance, the NMR enabled assessment of the appropriate chelating agents had identifiable importance. Additionally described was the progress made with silicon monoxide anodes supported on cellulosic substrates. The high active material loadings achieved, while also intriguing from a performance perspective, enabled 29Si MAS-NMR and 7Li static in-situ NMR measurements. For the in-situ measurements in particular, a novel cell design was constructed to utilize the advantages of a cellulosic substrate in this context. This has also enabled preliminary work on a spinning in-situ design. / Thesis / Doctor of Philosophy (PhD)

The Al₂SiO₅ polymorphs have been examined to provide new insights into their chemical bonding, their crystal chemistry, their equations of state, and the incorporation of water in the form of hydroxyl in their structures. The Al₂SiO₅ polymorphs provide a unique structural assemblage for a crystal chemical examination due to the variation in Al coordination in the structures where Al is in 4-fold, 5-fold, and 6-fold in sillimanite, andalusite, and kyanite, respectively. Consequently, the Al₂SiO₅ polymorphs have been examined with a combination of experimental (high pressure X-ray diffraction and Polarized FTIR spectroscopy) and theoretical (VASP and Crystal 98) methods. An experimental high pressure X-ray diffraction study on andalusite and sillimanite has constrained their equation of state and the pressure derivatives of their bulk modulus with pressure. Additionally, the effect of pressure on the crystal structures has been examined, where the main structural response is compression of the AlO₆ octahedra. Comparatively, compression of the AlO₆ octahedra in andalusite is more anisotropic, while the major direction of axial compressibility in both structures is dependent on the orientation of the AlO6 octahedra. In order to better understand the crystal chemistry of the Al-O and Si-O bonds in the polymorphs, ELF isosurfaces were examined. ELF isosurfaces represent a graphical representation of the localized electron probability density. Six distinct types of ELF isosurfaces were observed in the Al₂SiO₅ polymorphs resulting from differences in the geometry, coordination, and coordinated cation atomic number surrounding the oxygens within the crystal structures. The ELF was also shown to be isostructurally related to electron density difference maps. In a combined experimental and theoretical investigation of the Al₂SiO₅ polymorphs, potential protonation sites within the crystal structures were determined at an atomic level with polarized FTIR spectroscopy and analysis of (3,-3) critical points of the negative Laplacian. The polarized FTIR spectra indicate the orientation of the OH dipole in the three polymorphs and the (3,-3) critical points indicate regions of locally concentrated electron density. Potential protonation sites were determined based on the value of the negative Laplacian, the underbonded nature of the oxygens, and the number of surrounding cations. / Ph. D.

Les travaux de cette thèse concernent l'étude de l'influence des conditions de dépôt sur la microstructure et les propriétés optiques de monocouches dans le but de réaliser des filtres optiques particuliers commercialisables. La méthode de dépôt utilisée est l'évaporation par canon à électrons avec assistance ionique. L'un des deux projets a été de vérifier la faisabilité de filtres optiques infrarouges dans la gamme [2-15] µm avec des matériaux non toxiques. Les monocouches des trois fluorures étudiées ont montré des comportements différents suivant les conditions de dépôt, notamment suivant la température du substrat qui influe fortement sur leur microstructure. L'association du BaF₂ au germanium, avec des réglages optimisés, montre pour différents filtres réalisés des résultats proches de la théorie. Ces filtres sont donc commercialisables. Le second projet a été de développer une machine de dépôt dans le but de pouvoir réaliser des filtres complexes d'une centaine de couches d'épaisseur variable (de 15 à 300 nm) associant des monocouches de TiO₂ à des monocouches de SiO₂. L'étude de l'influence des paramètres de dépôts (pression, assistance ionique, préchauffage du matériau) au travers différentes caractérisations (MEB, AFM, ellipsométrie)  a permis une optimisation des réglages de l'enceinte de dépôt plus efficace et adaptée en fonction des spécifications des filtres optiques à réaliser. Puis, une étude ellipsométrique poussée de l'indice de réfraction des monocouches de TiO₂ en fonction de leur épaisseur a conduit à une nette évolution des résultats pour la réalisation du filtre complexe. / This thesis deals the study of deposition conditions 'effect on the microstructure and optical properties of monolayers in order to achieve marketable optical filters, with particular specifications. All filters and monolayers were deposited by ion-assisted electron-beam evaporation technique. One of the two projects was to test the feasibility of infrared optical filters in the range [2-15] µm with non-toxic materials. The study of monolayers of three fluorides showed different behaviors depending on the deposition conditions especially as a function of the substrate temperature that affects their microstructure. For different filters realized, the association of BaF₂ with germanium, settings of deposition optimized, shows results close to the theory and these filters are marketable. The second project was to develop a deposition chamber in order to realize complex filters built with one hundred layers of variable thickness (15 to 300 nm) associating monolayers of TiO₂ with monolayers of SiO₂. The study of the influence of deposition parameters (pressure, ionic assistance, preheating of material) through different characterizations (SEM, AFM, ellipsometry) allowed the optimization of deposition's parameter settings more effective, and adapted according to the specifications of the optical filters to realize. Then, an ellipsometric advanced study of the refractive index of TiO₂ monolayers depending on their thickness led to a significant change in results for the realization of complex filter.

We report on the fabrication of a new complex catalytic system composed of silica-supported silver nanoparticles (AgNP) encapsulated inside polymer microcapsules (MC)s. The silver nanocatalyst itself was obtained by reduction of silver salt in the presence of SiO₂ particles acting as AgNP carriers, to provide a complex Ag/SiO₂ catalyst with the Ag surface completely free of capping agents. Ag/SiO₂ particles were enclosed inside the interior of polymer microcapsules. Due to the presence of the hydrophobic shell on the MC surface, catalytic reactions become feasible in an organic solvent environment. On the other hand, the hydrophilic nature of the MC interior forces the water-soluble reactants to concentrate inside the capsules which act as microreactors. Based on the example of catalytically driven reduction of 4-nitrophenol we demonstrate that encapsulated Ag/SiO₂ particles possess enhanced catalytic activity as compared to the catalyst being freely dispersed in reaction medium.

This master's thesis studies the electronic properties changes of graphene caused by substrate SiO2, adsorbed molecules of water and atoms of gallium. There are tested different geometrical configurations of these systems and consequently calculated band structures to derive the changes of the electronic properties: the doping effect and band gap opening of graphene layer.

Made available in DSpace on 2014-07-29T15:07:08Z (GMT). No. of bitstreams: 1 Dissertacao Alexandre Miranda de Oliveira.pdf: 4426704 bytes, checksum: 904266306eab31523948c4d6634abfe0 (MD5) Previous issue date: 2010-12-15 / This work is to study the crystallization of compounds in the form of post system alumina-yttria-silica prepared by sol-gel mixed methodology and Pechini. Powders (x / 2) Y ² ³ - (X / 2) Al ² O ³ - (1-x) SiO ² (x = 0.1 0.2, 0.3, 0.4 and 0.5 mol) were doped with erbium prepared and characterized. The physical properties of composite SiO ² ¹ YO-, 5 - AlO ¹, 5 were studied by x-ray diffraction, FTIR spectroscopy, thermogravimetry, differential thermal analysis and photoluminescence measurements. It was possible to maintain the amorphous compositions at high temperatures, no crystallization below 900 ° C and the formation of phase Y ² ² O7 Si at 1100 ° C. We obtained a reasonable life time of some compositions treated at 1000 ° C. We observed the emission of green upconversion to excite the samples with high power laser. All synthesized samples exhibit photoluminescence emission and have maximum emission at 1530 nm with a width of ~ 47nm. This broad issue is a desirable property for amplifiers used in systems division multiplexing wavelengths (WDM) and suggests that Er ³ + ions are hosted in the amorphous phase. / Neste trabalho estudo-se a cristalização de compostos na forma de pós do sistema alumina-ítria-sílica preparados pela metodologia mista sol-gel e Pechini. Pós de (x/2) Y²O³-(X/2) Al²O³-(1-x) SiO² (x=0,1 0,2, 0,3, 0,4 e 0,5 em mol) dopados com érbio foram preparados e caracterizados. As propriedades físicas dos composto de SiO²-YO¹,5- AlO¹,5 foram estudadas por difração de raios-x, espectroscopia FTIR, termogravimetria, análise térmica diferencial e medidas de fotoluminescência. Foi possível manter as composições amorfas a altas temperaturas, não houve cristalização abaixo de 900° C e a formação da fase Y²Si²O7 a 1100 °C. Obtivemos um tempo de vida razóavel de algumas composições tratadas a 1000°C. Observamos a emissão verde de upconversion ao excitar as amostras com laser de alta potência. Todas as amostras sintetizadas apresentam emissão fotoluminescente e possuem máximo de emissão em 1530 nm com largura a meia altura de ~47nm. Essa emissão larga é uma propriedade desejável para amplificadores usados em sistemas de multiplexação por divisão de comprimentos de onda (WDM) e sugere que os íons Er³+ estão hospedados na fase amorfa.

This dissertation has investigated the adsorption, thermal behavior, and radiation (both photon and electron) processing of prebiotically-relevant ices and surfaces. A custom ultra-high vacuum (UHV) chamber has been built that is coupled with a Fourier Transform-Infrared (FT IR) spectrometer and a Temperature Programmed Desorption (TPD) system that utilizes Quadrupole Mass Spectrometry (QMS) to study selected organic:surface systems. Formamide (HCONH₂) has been studied in two related but distinct studies relevant to primitive Earth and interstellar chemistry. First, in collaboration with a theory group, formamide’s interaction with kaolinite (Al6Si6O36H30), a clay mineral relevant to early Earth chemistry, has been studied experimentally and theoretically. Experimental infrared results are compared with calculated infrared frequencies obtained by our collaborators. TPD analysis is compared with the calculated values of adsorption energy, and the optimal kaolinite termination site for adsorption is reported. Second, the first thermal and radiation damage study of pure formamide and HCONH₂:H₂O mixed ices on an interstellar icy grain analog (SiO₂) is reported. A discussion of the pure formamide ice phases identified with FT-IR upon warm-up, as well as the TPD binding energies of HCONH₂ on SiO₂, is presented. The observed Lyman-alpha photochemical products and proposed formation mechanisms from pure formamide ice is reported and discussed. In addition, results of Lyman alpha processing of mixed HCONH₂:H₂O ices are provided. Low-energy electron irradiation of pure HCONH₂ and HCONH₂:H₂O mixed ices has also been reported for the first time. A third investigation has studied acetylene (C₂D₂) and acetonitrile (CH₃CN) interactions and radiation stability in mixed low-temperature ices to simulate possible prebiotic reactions that may occur on Saturn’s moon, Titan. This investigation contributes to understanding the possible consumption, trapping, and degradation of these species on the surface of Titan.

Les travaux de cette thèse concernent l'étude de l'influence des conditions de dépôt sur la microstructure et les propriétés optiques de monocouches dans le but de réaliser des filtres optiques particuliers commercialisables. La méthode de dépôt utilisée est l'évaporation par canon à électrons avec assistance ionique. L'un des deux projets a été de vérifier la faisabilité de filtres optiques infrarouges dans la gamme [2-15] µm avec des matériaux non toxiques. Les monocouches des trois fluorures étudiées ont montré des comportements différents suivant les conditions de dépôt, notamment suivant la température du substrat qui influe fortement sur leur microstructure. L'association du BaF₂ au germanium, avec des réglages optimisés, montre pour différents filtres réalisés des résultats proches de la théorie. Ces filtres sont donc commercialisables. Le second projet a été de développer une machine de dépôt dans le but de pouvoir réaliser des filtres complexes d'une centaine de couches d'épaisseur variable (de 15 à 300 nm) associant des monocouches de TiO₂ à des monocouches de SiO₂. L'étude de l'influence des paramètres de dépôts (pression, assistance ionique, préchauffage du matériau) au travers différentes caractérisations (MEB, AFM, ellipsométrie) a permis une optimisation des réglages de l'enceinte de dépôt plus efficace et adaptée en fonction des spécifications des filtres optiques à réaliser. Puis, une étude ellipsométrique poussée de l'indice de réfraction des monocouches de TiO₂ en fonction de leur épaisseur a conduit à une nette évolution des résultats pour la réalisation du filtre complexe.