A novel synthesis technique for the production of copper zinc tin sulfide (CZTS) nanocrystals has been developed using aerosol spray pyrolysis. CZTS is a quaternary semiconducting material that shows promise as a replacement to common semiconductors such as CdTe and CIGS for use in photovoltaic devices. CIGS is currently being commercialized in the photovoltaic industry, but rare and expensive indium and gallium components threaten its long term viability. CZTS looks to be one of the best alternatives to CIGS with all earth abundant and non-toxic materials and recent impressive gains in efficiency. A number of synthesis techniques have been thoroughly studied and detailed previously. In our novel approach, we synthesis single phase nanocrystals, starting with zinc, copper, and tin diethyldithiocarbamate precursors in a toluene solvent. The precursor solution is aerosolized using an ultrasonic nebulizer wherein the droplets are vacuumed through a tube furnace and nucleation occurs. We reproducibly synthesize kesterite, Cu2ZnSnS4, nanocrystals. This technique continuously converts the chemical precursor into high-purity nanopowder with a production rate of ~50 mg/hour for an un-optimized, lab-scale reactor. Using the same precursor chemistry, we have also been able to deposit high-quality CZTS thin films directly onto Mo-coated Swiss glass substrates using the aerosol spray pyrolysis technique. A thorough discussion of the current photovoltaic field, the processing parameters and challenges of nanocrystal and thin film production, and the experimental results will be presented. Characterization via Raman spectroscopy, EDS, XRD, TEM and XPS will be offered along with future recommendations and considerations.

Detrital Cr-spinels from the Jack Hills region of Western Australia co-exist in conglomerates with the oldest terrestrial zircons (≤4.4 Ga). In this study, these Cr-spinel are examined to determine their age and tectonic setting using a new geochemical approach of combining highly siderophile element (HSE: Os, Ir, Ru, Pt, Pd, Re) abundances and Re-Os isotope systematics with major, minor, and trace element mineral chemistry.The Cr-spinels exhibit high ZnO (≤13 wt.%), low average Mg# (15), and moderate average Cr# (61), consistent with chemical modification during metamorphism. The measured 187Os/188Os ratios (0.10517-0.10667) of Cr-spinel separates are strongly sub-chondritic (γOschon = -6.8 to -12). When corrected for Re ingrowth, the initial 187Os/188Os ratios (0.09218-0.09924) lie at or close to the Solar System initial or are modestly supra-chondritic. The time of rhenium depletion age (TRD), which is a minimum model age, indicates formation of the Cr-spinels ~3.23 ±0.16 billion years ago (2σ uncertainty). The Cr-spinels have between 34 to 53 ng/g Os and the HSE abundance patterns show significant Pt and Pd depletion relative to Os, Ir, and Ru.

Two-dimensional vortex interactions and merging in fluid flows have long been a subjectof significant research interest, with particular focus on clarifying their role in the inverse energy cascade of two-dimensional turbulence. Previous research has generally taken one of two forms: detailed study of the interaction of two vortices in isolation, or macroscopic study of a field of many vortices. Bridging the gap between these has been difficult, due to the complexity of the two-vortex, i.e., vortex pair, interaction and its varied outcomes when the vortices are unequal. In order to rectify this, this research considers in detail the interaction of two unequal co-rotating vortices in viscous fluid, and develops a method to quantitatively assess their outcomes. This enables a simple characterization of interaction outcomes in terms of certain key parameters. Using this, the case of a vortex pair interacting in linear shear which serves as a simple model of the background flow generated by a field of many vortices, is then studied. Collectively, this work establishes a method for studying the influence of background flow on interacting vortices.

For the present research, numerical simulations are performed of vortex pairs having arange of vortex strength ratios in background flow having a linear shear velocity profile having a range of strengths, for finite Reynolds number. A method is introduced to monitor the flow development continuously, enabling the quantitative assessment of interaction outcomes in terms of an enhancement factor, ε, and a merging efficiency. η, which compare the circulations at the start and end of the convective interaction. The variation of these outcomes is found to be well-characterized by a mutuality parameter, a quantity directly related to the vortices’ enstrophy ratio. The presence of shear is then found to produce two distinct flow regimes: separation, in which the vortices move apart continuously, and hendition, in which they interact to form a single vortex similar to, and similarly characterized as in, the isolated-pair case. However, the presence of shear is observed to alter the timing of key physical interaction processes, which may in some cases significantly alter the ultimate outcome. Taken together, these findings imply a general framework for two-dimensional co-rotating vortex interactions that can be incorporated into turbulence models.

The field of solid state chemistry studies the reactivity and chemical transformations of solid phase materials. Although the tools used for analyzing the chemical properties and dynamics in solids have historically been rudimentary, one of the great advantages of studying solids is that all of the atoms are arranged in precise positions. Knowing this information can provide a great sense of control and understanding of the reaction environment present in solids. By analyzing compounds in the crystalline state, structural variations, such as functional group substitutions and deletions, can be rigorously monitored and their exact effect on the compound's solid state reactivity can be understood. To this extent, my work has focused on studying the effects of synthetic modification and solid state analysis towards two fields--crystalline molecular machines in the form of bridged molecular gyroscopes and solid state photochemistry by synthetically altering α-santonin.

Chapter one provides a brief introduction to the field of organic solid state chemistry, in which the fundamentals of both molecular machines and solid state photochemistry are discussed. The molecular machines overview reviews the first molecular machines and the advancement of molecular gyroscopes through the literature. The area of solid state photochemistry is also described, and its underlying principles such as the topochemical postulate, are examined.

Chapter two details a general strategy for synthesizing bridged molecular gyroscopes. A one-pot macrocyclic synthesis was developed and it was found to be robust in forming ether and ester linked macrocyclization. The results yielded both singly and triply bridged molecular gyroscopes and revealed the propensity for bridged molecular gyroscopes to "collapse" in toward the rotator, ultimately hindering the desired rotation.

Chapter three describes the design synthesis and solid state characterization of an azobenzene bridged molecular gyroscope that was made to function as a photochromic molecular brake. The compound was synthesized and its solid state physical characteristics were analyzed using UV-Vis absorption spectroscopy, single crystal X-ray diffraction and spin echo 2H NMR. The compound was found to undergo a photochromic isomerization between a cis and trans isomer as a nanocrystalline suspension and the energy of activation for the cis and trans states was measured to be 4.6 kcal/mol and 5.1 kcal/mol, respectively, indicating a 0.5 kcal/mol difference between the two states.

Chapter four explores the addition of different functional groups to the bridged molecular gyroscopes in order to understand and control the packing of the molecules. Two of the compounds were found to have isostructural packing and crystallized in the desired lamellar sheet arrangement. The data suggested that the electronic and steric environment shared between these functional groups was key in attaining the lamellar structure.

Chapter five was done in collaboration with the Naumov group at New York University in Abu Dhabi and describes the synthesis, crystal packing, and photochemical reactions of α-santonin and its methyl, ethyl, n-propyl, and n-butyl derivatives. The photosalient effect of α-santonin was captured, using a high-speed camera, and its splitting found to occur normally to the b axis of the unit cell. The study analyzed the crystal structures and the photochemistry both solution and using nanocrystalline suspensions in water. The solution photochemistry was in accord with literature precedence and the crystalline suspensions yielded a variety of photoproducts including a hydrate, which is not commonly observed in neutral water. An exocyclic alkene photoproduct was also discovered and its presence is hypothesized to be produced by an intermolecular deprotonation caused by a molecule of water present in the crystal.

This dissertation investigates the Ottoman Empire’s settlement of refugees fleeing Russian persecution along the empire’s desert frontiers between 1866 and 1918. I contend that Muslim refugees from the Caucasus and the state officials who planned their settlement developed the internal frontiers of the Ottoman Empire to transform these regions’ societies, politics, and environments well into the twentieth century. The dissertation is thus an intervention in the histories of population mobility, the environment, and the project of modernity in the Ottoman Empire. It investigates the implications of Istanbul’s policies, driven by what I refer to as a “civilizing attitude,” for the refugee settlers, administrators, local populations, and the environments of the Middle East. The Ottoman state enacted a program of creating model agricultural settlements populated by refugees to sedentarize nomads, whom officials viewed as backwards. The dissertation argues for the agency of the refugees, who adapted to challenging circumstances and ultimately influenced the drawing of borders in the Middle East after the collapse of the Ottoman Empire. The analysis takes as its case studies settlement schemes in Benghazi, eastern Libya; Quneitra, southern Syria; and Resülayn, northern Mesopotamia to conclude that small communities of refugees at the far edges of empire altered historical trajectories on the regional, imperial, and global levels.