Thesis (Ph.D.)--University of Delaware, 2009. / Principal faculty advisors: Anne Skaja Robinson and Christopher J. Roberts, Dept. of Chemical Engineering. Includes bibliographical references.

No description available.

Thesis (M.Ch.E.)--University of Delaware, 2008. / Principal faculty advisor: Christopher J. Roberts, Dept. of Chemical Engineering. Includes bibliographical references.

The concept of "aggregation-induced emission" (AIE) effect has induced a great deal of attention these days. Now, exploration of new AIE-active molecular system and multiple high technique applications for AIE materials are the two research hotspots. Cyanostilbene, as a classical structural unit in photoelectric functional materials, also exhibited this unique luminescence behavior. The research background was illustrated in Chapter 1, which mainly introduced the development of this subject. In this project, Chapter 2 and Chapter 3 presented two classes of functionalized AIE-active molecules based on cyanostilbene moiety, and their applications were investigated, while Chapter 4 demonstrated a series of donor-acceptor (D-A) molecules with highly emissive unit, and their photophysical properties were studied.;In Chapter 2, four different donor-substituted cyanostilbene-based dipyrrins were synthesized and characterized. The investigation of photophysical properties confirms that these molecules are AIE-active, which should be attributed to the cyanostilbene moiety. The introduction of different donor groups showed little impact on their luminescence. Furthermore, the emission properties of these molecules were found to be sensitive to Zn2+, that is, addition of Zn2+ enormously enhanced its fluorescence in THF. The titration experiments proved they showed good selectivity and sensitivity for Zn2+ detection with relatively low limit of detection. Job's curve and spectral studies of their corresponding zinc complex indicated that the ratio for dipyrrins and Zn2+ is 2:1, which suggested the formation of zinc complex by chelation-enhanced fluorescence (CHEF) effect should be the reason of the enhanced fluorescence. By combining dipyrrin with typical AIE-active moiety tetraphenylethylene (TPE), an AIE-active TPE-based dipyrrin was prepared. The studies of its fluorogenic Zn2+ detection confirmed that the CHEF effect together with AIE effect are responsible for the intense fluorescence, indicating the potential application as a Zn2+ detector in aqueous media.;In Chapter 3, the cyanostilbene backbone was functionalized with a terpyridine unit to construct four terpyridine-based cyanostilbene molecules with different donor substitutents. The investigation of their photophysical properties confirms that they are AIEE-active. With the effect of different electron-donating groups, their solid-state fluorescence color was adjusted from blue to orange-red successfully. According to the calculation results of their frontier molecular orbitals, terpyridine has little impacts on their luminescence, but would influence their solid-state emission obviously owing to its large steric hindrance. This class of molecules displayed higher luminescence efficiency in solid state than in their dissolved state. The twisted molecular conformation in single crystal, which effectively avoids close π-π stacking, was assumed to be responsible for the high luminescence efficiency in solid state. This kind of molecules show distinct switched fluorescence by stimuli of acid/base vapors, and this phenomenon derives from the protonation effect of nitrogen atoms in the terpyridine unit. Moreover, three of these molecules exhibit good electroluminescence properties. Especially, the crystal of non-donor substituted molecule show amplified spontaneous emission (ASE) properties, indicating this blue-emissive material can be used in multiple areas such as chemical sensor, organic light emitting diodes (OLEDs) and organic laser media.

Core-shell nanohybrids have wide applications in pollutant degradation. In this study, core-shell nanohybrid was formed through heteroaggregation between neutral nanoparticles (i.e., hematite nanoparticles or HemNPs) and charged nanoparticles (i.e., carboxylated polystyrene nanoparticles or PSNPs). In the dispersant solution of 1 mM NaCl at pH 6.3, HemNPs were neutral and underwent favorable homoaggregation, whereas PSNPs were negatively charged and underwent no homoaggregation. When the two types of particles were mixed, homoaggregation of HemNPs and heteroaggregation between HemNPs and PSNPs took place simultaneously, forming HemNPs-PSNPs heteroaggregates. The transmission electron microscopy images of heteroaggregates show that HemNPs and PSNPs formed core-shell structure in which HemNPs were the cores and PSNPs were the shells. The size of the core-shell nanohybrids can be controlled by varying the concentration ratio of HemNPs to PSNPs. The increase of the size of charged nanoparticles resulted in larger nanohybrids. This new method has lower energy footprint than existing ones. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection

In 1745 a Scotch Benedictine monk Andrew Gordon discovered Contact Charge Electrophoresis (CCEP) which remained in dormant state for centuries until gaining renewed prominence in the field of particle manipulation and actuation. Contact Charge Electrophoresis (CCEP) refers to the continuous to and fro motion of a conductive object between two electrodes subject to an applied voltage. The continuous motion of the conductive particle and the low power requirement provide an attractive alternative to traditional methods for particle manipulation techniques such as dielectrophoresis. Recent efforts to understand and apply CCEP have focused on the motion of single particles and we present dynamics of multiple conductive particles dispersed in non-conducting media that utilize CCEP to perform tasks like pumping and cargo transport operations as well as multiparticle clusters capable of tailored trajectories. Chapters 1 provides motivation for this work and background on CCEP. Providing brief details on development of microfluidic devices and modeling that are covered in more details in subsequent chapters. It also focuses on the historical aspect of CCEP, relevant background, mechanism, physics, application strategies in literature, strategies developed for single particle systems and possible extension to multiparticle systems. Chapters 2 and 3 talk about the dynamics and modeling of multiple conductive particles both in dispersion and aggregates/clusters powered by CCEP. In Chapter 2, we propose a new hybrid approach based on image-based method proposed earlier by Bonnecaze[18] for modeling CCEP. It covers challenges to modeling a multiple particle system in confinement, dynamics of chain formation and dynamics of cluster comprising conductive and non-conductive particles between two electrodes. While Chapter 3 focuses on details of methods and techniques used in development of the simulation for dispersion of conductive particles in confinement. Here we also illustrate variation of conductivity for complete range of electrode separation with varying volume fraction. Chapter 4 expands on multiple particle CCEP and shows that when we physically constrain particle trajectories to parallel tracks between the electrodes, the traveling waves of mechanical actuation can be realized in linear arrays of electromechanical oscillators that move and interact via electrostatic forces. Conductive spheres oscillate between biased electrodes through cycles of contact charging and electrostatic actuation. The combination of repulsive interactions among the particles and spatial gradients in their natural frequencies lead to phase locked states characterized by gradients in the oscillation phase. The frequency and wavelength of these traveling waves can be specified independently by varying the applied voltage and the electrode separation. We demonstrate how traveling wave synchronization can enable the directed transport of material cargo. Our results suggests that simple energy inputs can power complex patterns of mechanical actuation with potential opportunities for soft robotics and colloidal machines. Chapter 5 systematically investigate the dynamics of cluster comprising multiple spherical conductive particles driven via contact charge electrophoresis (CCEP). We are specifically interested in understanding dynamics of closed packed cluster of particles with both conductive and non-conductive particles in three dimensions(3D). Finally, Chapter 6 summarizes new ideas and proposes possible applications for multiple particle Contact charge electrophoresis motivated by this dissertation.

Thesis (Ph. D.) in Chemistry--University of Maine, 2002. / Includes vita. Includes bibliographical references (leaves 157-169).

Thesis (M.C.E.)--University of Delaware, 2008. / Principal faculty advisor: Chin-Pao Huang, Dept. of Civil and Environmental Engineering. Includes bibliographical references.

Tungsten is considered the prime candidate material for plasma facing components within fusion reactors. However, exposure of tungsten to neutron flux brings about transmutation of tungsten into by-products: Re, Os and Ta. Under increasing levels of radiation damage, irradiation induced clustering/precipitation takes place that embrittles and thus reduces lifetime of such tungsten components. This thesis was undertaken to explore this subject on a deeper level. There are three components to this study. The first part considers the effect of Re content on irradiation induced clustering. Lab-made plate W-xRe (x: 2, 5, 10 and 25at.%) alloys were exposed to 1.2, 3.9 and 33dpa, self-ion irradiated at 773K. Analysis of cluster number density and volume fraction found they increase with damage level and bulk Re content. Based on these trends and existing literature data, a hypothesis was proposed suggesting clusters originate from vacancy clusters. Also, at 33dpa, rod shaped clusters form in W-25Re alloys while spherical clusters are present in other alloys. The clusters show close correspondence with irradiation induced precipitates and appear to be precursor phase. In the second part of this thesis, the effect of Os and Ta on cluster formation and alloy mechanical properties is examined. Lab-made plate W-1Re-1Os and W-2Re-1Ta alloys were irradiated at 33dpa at 573 and 773K and compared against control W-2Re alloy. At 33dpa and 573K, the Os and Ta presence suppresses cluster formation. Both ternary alloys contain smaller cluster diameter, composition, number density and volume fraction than the W-2Re alloy. However, at 33dpa and 773K, Os and Ta have opposing effects on cluster behaviour. Os increases the cluster nucleation rate and raises irradiation hardening (compared to W-2Re). Meanwhile, Ta presence decreased cluster number density and reduced the irradiation hardening (compared to W-2Re alloy). As well, Ta showed no evidence of clustering, only Re clusters form in the W-2Re-1Ta alloy. The final aspect of the thesis analyzes the effect of material microstructure and external variables on cluster formation in W-Re alloys. Commercial wire form W-25Re alloy was irradiated at 1.2dpa at 573 and 773K as atom probe needles and bulk sample. The larger free surface on atom probe needle samples appears to act as a sink for self-interstitials and vacancies at both temperatures. The effect of grain size and dislocation density was examined by irradiating commercial W-5Re wire (0.5-1μm diameter) and plate (1-3mm diameter) samples (annealed and unannealed) to 33dpa and 573K. It was found grain boundaries and dislocations act as defect sinks at 573K. Additionally, radiation enhanced Re grain boundary enrichment was observed for first time. The effect of grain size on cluster behaviour at 773K was also analysed. Commercial wire and lab-made plate W-3Re, W-5Re and W-25Re alloys were irradiated to 33dpa at 773K. The larger grain boundary area in wire samples is suspected of acting as a sink for self-interstitials leaving more vacancies for promoting cluster formation compared to lab-made samples. The discoveries made in this thesis broaden our current understanding of irradiation induced phase formation in tungsten. Their implications on plasma facing component design are discussed as well as recommendations for improvements. Further, areas requiring further research in this field are also highlighted.

Alzheimer's disease (AD) is the most common cause of dementia; a problem that is growing in size and cost as the population ages. Early soluble aggregates composed misfolded 'amyloid' peptide sequences have been implicated as key to the initiation and onset of AD pathology, although little is definitively known as to when and how these assemblies form or interact to instigate pathology. The primary focus of this study was to evaluate whether L-Tryptophanol (Trol) signal, which has been shown to be induced via soluble amyloid species, increases with AD severity in a range of ex vivo human samples. Testing of this hypothesis was carried out in several stages: Initially synthetic versions of the amyloid beta (Aβ) peptide were tested in vitro to corroborate Trols propensity to associate to amyloid assemblies and allow for method development. Next, a range of brain lysates from several transgenic mouse lines and aged human AD cases and controls were assessed using the reporter. These experiments demonstrated Trols sensitivity to Aβ and tau, and provided compelling evidence that Trol signal tracks disease progression in brain lysates. During the final stage of testing cerebrospinal fluid (CSF) from AD and Parkinson's disease (PD) patients, and blood plasma samples from PD patients was evaluated. Results from this phase of testing indicated that Trol was able to detect differences in sample composition between healthy and diseased individuals, however differences were not clear cut and could have been affected by confounding factors. Overall, the data presented here suggest that Trol may be able to track disease progression in amyloidopathies when implemented in brain lysates. However, further testing is required to completely validate this finding. These findings highlight the potential of simple techniques for amyloid detection to aid within the diagnosis, evaluation of disease progression and study of AD and other neurodegenerative diseases.