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This document only includes an excerpt of the corresponding thesis or dissertation. To request a digital scan of the full text, please contact the Ruth Lilly Medical Library's Interlibrary Loan Department (rlmlill@iu.edu).

Over the past several decades the phenomenon of luminescence (divided into fluorescence and phosphorescence) has received great attention in the field of biological science. This quest has motivated scientists for a variety of applications, including fluorescence imaging. Fluorescence microscopy techniques that provide unique advantages, such as high spatial resolution and superior sensitivity, have been regarded as attractive tools in biophotonics. With the progress of ultrafast laser sources, two-photon absorption (2PA), in which a molecule absorbs two photons simultaneously, has opened possibilities of using it for various applications. Two-photon fluorescence microscopy (2PFM), which affords deeper tissue penetration and excellent three-dimensional (3D) images, is now being widely employed for bioimaging. This dissertation focuses on the design, synthesis, and photophysical characterization of new fluorophores, as well as desirable applications. Chapter 1 gives an account of a brief introduction of luminescence and 2PA, as well as their utilities in biological applications. In chapter 2, a series of new BODIPY derivatives are presented along with their comprehensive linear and nonlinear characteristics. They exhibited excellent photophysical properties including large extinction coefficients, high fluorescence quantum yields, good photostability, and reasonable two-photon absorption cross sections. Two promising compounds were further evaluated as NIR fluorescent probes in one-photon and two-photon fluorescence imaging. Chapter 3 provides the design, synthesis, and photophysical characterization of two BODIPY dyes. In order to assess the potential of using the dye as a fluorescent probe, Lysotracker Red, a commercial lysosomal marker, was investigated for comparison purposes. The results indicate that figure of merit of both compounds were three orders of magnitude higher than that of Lysotracker Red. With an eye towards applications, one of the compounds was encapsulated in silica-based nanoparticles for in vitro and ex vivo one-photon and two-photon fluorescence imaging, in which the surface of the nanoparticle was modified with RGD peptides for specific targeting. The nanoprobe exhibited good biocompatibility and highly selective RGD-mediated uptake in ?V?3 integrin-overexpressing cancers, while maintaining efficient fluorescence quantum yield and high photostability. In chapter 4, the synthesis and photophysical properties of a novel photosensitizer with heavy atoms (halogen) were presented. The dye exhibited low fluorescence quantum yield, resulting in high singlet oxygen generation quantum yield. In vitro photodynamic studies demonstrated that photosensitization of the agent can induce cellular damage, subsequently leading to cell death by a necrotic cell death mechanism, supporting the therapeutic potential of using the agent for photodynamic therapy.

<p> Light emitting silicon nanostructures are of significant interest for photonics due to their potential to act as the source material for a monolithically integrated Si-based light source. This thesis reports on the experimental characterization of such luminescent structures formed in silicon nitride, oxynitride, and rare earth doped silicon oxide thin films. Changes in the electronic structure of the materials have been analyzed using soft X-ray spectroscopy by probing the constituent elements at their absorption edges. The observed near edge structure at these edges is related to the local atomic bonding environment of the probed atoms. Specifically, changes in the near edge structure at the Si K and L3,2 absorption edges can be related to the coordination of silicon atoms within the films.</p> <p> In the silicon nitrides the Si-clustering process has been observed to onset at different anneal temperatures, dependant on film composition. In films that have a small amount of excess Si higher anneal temperatures are required before a significant Si-Si bonding signal is observed. In samples with high concentrations of excess Si this clustering process is observed to occur at temperatures as low as 700 °C. In silicon oxynitride samples only a small fraction of the excess Si forms into clusters within the films. Rather, in these samples the formation of distinct silicon oxide and silicon nitride phases is observed, with strong absorption related to the formation of the oxide phase being observed after annealing at high temperatures (T ≥ 1000 °C). The nanoclusters were determined to be amorphous in nature, rather than nanocrystalline, through the use of high-resolution, energy filtered, and scanning transmission electron microscopy. This behavior was seen even for samples with high excess Si concentrations and annealed at high temperatures. This contrasts with the behavior of silicon-rich silicon oxide thin films were nanocrystals are clearly observed after similar treatments, indicative of the influence of the nitride host matrix on the cluster formation process.</p> <p> Changes in the electronic structure at these edges have been correlated with changes in the bonding structure within the films, as analyzed through Fourier transform infrared spectroscopy, and with the photoluminescent behavior of the films.</p> <p> X-ray excited optical luminescence (XEOL) has been used for the study of rare earth doped silicon oxides, allowing for site specific excitation of the films in order to analyze the origin of luminescence in the films. In O-rich samples the luminescence of the films has been observed to be strongly excited at O-related absorption edges while in Si-rich samples XEOL is observed at Si-Si bonding absorption energies. The results indicate the presence of different sensitization pathways towards luminescence in the films, including the formation of oxide or silicate phases.</p> / Thesis / Doctor of Philosophy (PhD)

<p> Nepheline syenite samples were collected from the Bancroft and Blue Mountain areas, Ontario, Canada, and were analysed for K, Rb, and Tl contents by atomic absorption spectrophotometry. The results for these elements and the corresponding K/Rb, K/Tl and Rb/Tl ratios were compared with those of nepheline syenites in various localities, and were found to be similar.</p> <p> The Tl, Rb, K contents and the K/Rb, K/Tl and Rb/Tl ratios in this study were determined to be 825 ppb, 110 ppm, 3.28%, 298, 4.11x10^4 and 135 respectively for the Bancroft nepheline syenite gneisses, and 574ppb, 93ppm, 3.28%, 353, 5.71x10^4 and 162 respectively for the Blue Mountain nepheline syenites. From these data, the nepheline syenite rocks in this study were probably originated as continental plutonics.</p> / Thesis / Bachelor of Science (BSc)