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Passive site remediation is a new concept proposed for non-disruptive mitigation of liquefaction risk at developed sites susceptible to liquefaction. It is based on the concept of slow injection of stabilizing materials at the edge of a site and delivery of the stabilizer to the target location using the natural groundwater flow. The purpose of this research was to establish the feasibility of passive site remediation through identification of stabilizing materials, a study of how to design or adapt groundwater flow patterns to deliver the stabilizers to the right place at the right time, and an evaluation of potential time requirements and costs. Stabilizer candidates need to have long, controllable gel times and low viscosities so they can flow into a liquefiable formation slowly over a long period of time. Colloidal silica is a potential stabilizer for passive site remediation because at low concentrations it has a low viscosity and a wide range of controllable gel times of up to about 100 days. Loose Monterey No. 0/30 sand samples (Dr = 22%) treated with colloidal silica grout were tested under cyclic triaxial loading to investigate the influence of colloidal silica grout on the deformation properties. Distinctly different deformation properties were observed between grouted and ungrouted samples. Untreated samples developed very little axial strain after only a few cycles and prior to the onset of liquefaction. Once liquefaction was triggered, large strains occurred rapidly and the samples collapsed within a few additional cycles. In contrast, grouted sand samples experienced very little strain during cyclic loading. What strain accumulated did so uniformly throughout loading and the samples remained intact after cyclic loading. In general, samples stabilized with 20 weight percent colloidal silica experienced very little (less than two percent) strain during cyclic loading. Sands stabilized with 10 weight percent colloidal silica tolerated cyclic loading well, but experienced slightly more (up to eight percent) strain. Treatment with colloidal silica grout significantly increased the deformation resistance of loose sand to cyclic loading. Groundwater and solute transport modeling were done using the codes MODFLOW, MODPATH, and MT3DMS. A "numerical experiment" was done to determine the ranges of hydraulic conductivity and hydraulic gradient where passive site remediation might be feasible. For a treatment are of 200 feet by 200 feet, a stabilizer travel time of 100 days, and a single line of low-head (less than three feet) injection wells, it was found that passive site remediation could be feasible in formations with hydraulic conductivity values of 0.05 cm/s or more and hydraulic gradients of 0.005 and above. Extraction wells will increase the speed of delivery and help control the down gradient extent of stabilizer movement. The results of solute transport modeling indicate that dispersion will play a large role in determining the concentration of stabilizer that will be required to deliver an adequate concentration at the down gradient edge. Consequently, thorough characterization of the hydraulic conductivity throughout the formation will be necessary for successful design and implementation of passive site remediation. The cost of passive site remediation is expected to be competitive with other methods of chemical grouting, i.e. in the range of $60 to $180 per cubic meter of treated soil, depending on the concentration of colloidal silica used. / Ph. D.

It is estimated that there are 5x1030 microorganisms on Earth and that approximately 50% live in unconsolidated sediment on the terrestrial subsurface. Subsurface disturbances caused by the constant search for natural resources and our dependence on groundwater make the abundance and diversity of these organisms a global concern. It is vital to many environmental fields, including bioremediation, water purification, and contaminant transport, that we understand how microorganisms and other colloidal particles attach to and detach from natural sediments and ultimately how they travel through porous media. Sticking efficiency (alpha) is a major component of most particle transport theories. It is defined as the ratio of particles that adhere to a collector surface compared to the total number of particles that collide with that surface. In this study, the Interaction Force Boundary Layer (IFBL) model was used to determine the sticking efficiencies of inorganic colloidal particles and Enterococcus faecalis cells against a silica glass collector surface. Sticking efficiencies were derived from intersurface potential energies that were determined from integrated force-distance data measured by Atomic Force Microscopy (AFM). Force data were measured in buffered aqueous solutions of varying pH and ionic strength to determine the influence of solution chemistry on particle removal from solution. Zeta-potentials were measured to determine the impact of particle and collector surface charge on force measurements. The results of this study indicate that alpha is strongly influenced by solution chemistry. The response of alpha to small changes in solution pH and ionic strength may be several orders of magnitude. Zeta-potential measurements imply that sticking efficiencies are strongly influenced by the electrical charges on both the particle and collector surfaces. Zeta-potentials of bacteria did not vary significantly with changing solution pH, but did respond to changing solution ionic strength. Historically, alpha has been very difficult to predict. This study is the first to report sticking efficiencies measured using AFM and the first to successfully apply the IFBL model to colloidal particles. Æ nThe incorporation of empirical nanoscale interactions into the measurement of alpha promises to more successfully describe particle adhesion and, thus, particle transport. / Ph. D.

This work describes the techniques of assembling colloidal gold on flexible polymeric substrates from solution. The process takes advantage of the strong affinity of gold to thiol and amino groups. Polymeric substrates were modified with silanes having these functional groups prior to Au attachment or in the case of poly(urethane urea) (PUU), no surface functionalization was required. This polymer has terminal amine and N-H groups on the polymer chain, which can act as coordination points for gold. Immersion in the colloidal gold solution led to the formation of a monolayer. Increased coverage was obtained by two methods. The first was a reduction or "seeding" process, where Au was reduced onto the attached particles on the surface. The second was using different linker molecules and creating a multilayered film by a layer-by-layer assembly. Three linker molecules of different lengths were used. Films fabricated using the smallest molecule had the least resistance whereas films fabricated with the longest molecule were not conductive. The resistance of these films may be varied easily by heating. Heating the films at temperatures as low as 120 °C caused a dramatic decrease in the resistance of over six orders in magnitude. Successful attachment of gold to PUU with very good adhesion properties was also demonstrated. The attachment of gold was stable in different solvents. Upon stretching the PUU-Au films, it was observed that there is a reversible resistance increase with strain and at a certain strain, the film becomes non-conductive. This sharp transition from conductive to insulating has potential applications in flexible switches and sensors. A hysteresis in the strain-resistance curves, analogous to the hysteresis in the stress-strain curves of the polymer was also observed. Using PUU as an adhesive agent, gold electrodes were successfully assembled on Nafion-based polymer transducers. These materials showed comparable actuation behavior to the electrodes made by the Pt-reduction method, with the added advantage of the ability to form patterned electrodes for distributed transducers. Patterning techniques were developed to form colloid-polymer multilayers for use in photonic crystal materials using selective deposition on patterned silane monolayers. Patterns of gold electrodes were also made on flexible polymers using a photoresist-based method. / Ph. D.

Luminescent quantum dots (QDs) or rods are semiconductor nano-particles that may be used for a wide array of applications such as in electro-optical devices, spectral bar coding, tagging and light filtering. In the case under investigation, the nano-particles are cadmium-selenide (CdSe), though they can be made from cadmium-sulfide, cadmium-telluride or a number of other II-VI and III-V material combinations. The CdSe quantum dots emit visible light at a repeatable wavelength when excited by an ultraviolet source. The synthesis of colloidal quantum dot nanoparticles is usually an organo-metallic precursor, high temperature, solvent based, airless chemical procedure that begins with the raw materials CdO, a high boiling point ligand, and a Se-trioctylphosphine conjugate. This investigation explores the means to produce quantum dots by this method and to activate the surface or modify the reaction chemistry with such molecules as trioctylphosphine oxide, stearic acid, dodecylamine, phenyl sulfone, aminophenyl sulfone, 4,4'dichlorodiphenyl sulfone, 4,4'difluorodiphenyl sulfone, sulfanilamide and zinc sulfide during the production to allow for further applications of quantum dots involving new chemistries of the outer surface. Overall, the project has been an interesting and successful one, producing a piece of equipment, a lot of ideas, and many dots with varied capping structures that have been purified, characterized, and stored in such a way that they are ready for immediate use in future projects. / Master of Science

Bacterial biofilms are communities of micro-organisms encased a self-produced extracellular matrix. While they form readily in a nature, biofilm formation in man-made systems have economic and health consequences. Prior research demonstrated that topographical features comprised of uniform, micro-meter sized particles hindered the biofilm formation of Pseudomonas aeruginosa (P. aeruginosa), an opportunistic human pathogen. The goal of the present work is to 1) further develop a potential anti-biofilm coating by improving its robustness and 2) study the mechanism(s) by which surface topography hinders biofilm formation. The robustness of a topographical coating comprised of an array of silica particles is improved by the introduction of silica bridges through a sol-gel reaction. To study the mechanism(s), specifically, we hypothesized that the motion, or surface motility, of P. aeruginosa is hindered by the presence of micro-meter scale obstacles via physical obstruction. To test this, we analyzed the behavior of single P. aeruginosa cells at micron-scale spatial resolutions using time-lapse fluorescence microscopy, image analysis, and particle tracking techniques. We fabricated various types of micron-scale topography with curvature (particle arrays) and recti-linear features (vertical steps) and varied the critical dimension within the range of 0.5 – 10 µm which spans the dimensions of a typical P. aeruginosa cell. We found that there was a threshold feature size of 1-2 µm at which bacterial surface motility is drastically impacted. On positively curved topography (particle arrays), we found that the frequent obstacles reduced the average speed of a bacterium from 6.2  0.3 µm per 5 min on a flat surface to 2.1  0.3 µm per 5 min on an array of 2 µm particles. Furthermore, we observed that bacteria often move in-between particles, suggesting that bacteria have difficulty climbing over tall obstacles. To further investigate P. aeruginosa's ability to cope with topography, we examined the effect of recti-linear features (vertical steps) on surface motility. We found that step heights > 0.9 µm drastically reduced the probability of crossing and that the average speed when approaching the step is reduced by a factor of 2. Interestingly, we find that bacteria have a slight preference to traverse down which is against the direction of gravity in our system. In summary, these results offer insights into how a surface motile bacterium copes with a topographical surface. Our data indicate that the topography of a surface can impede the surface motility of bacterium and thus, may be an important mechanism by which topography prevents biofilm formation. / Doctor of Philosophy / Bacteria and other micro-organisms can grow on surfaces such as medical devices and cause infections. Other examples of where bacteria can grow are on drains and pipes causing clogging, and on the hulls of ships, thus increasing drag. The goal of the current work is to investigate material coatings that resist the attachment and growth of bacteria on surfaces. We demonstrate that changing the roughness of the surface can reduce the number of bacteria found on the surface. More specifically, we have made surfaces covered with spheres that are approximately the same size as a bacterium, about 1 micrometer (10x smaller than the diameter of hair). We find that the spheres act as physical obstacles that block bacteria from moving on a surface. These results suggest that changing the micro-scale geometry of a surface may reduce the rate of infections on medical devices or hinder the growth of bacteria in other systems

The quest for efficient and cost-effective thin-film photovoltaic (PV) materials has recently zeroed in on hybrid lead halide perovskites, owing to their low cost, ease of processing, and exceptional efficiency metrics—peaking at 33.9% when combined with silicon in tandem devices. Nevertheless, there are substantial concerns about the stability, toxicity, and consequential environmental footprint of lead-based perovskites, thereby necessitating rigorous research to identify and develop alternative materials with superior stability profiles and diminished toxicity. Amongst the myriad candidates, chalcogenide perovskites and their related structures, represented by the empirical formula ABQ3 (with A = Ca, Ba, Sr; B = Zr, Hf, Ti; Q = S, Se), have emerged as particularly promising contenders. These materials are distinguished by their optimal optoelectronic properties and robust stability. Notably, barium zirconium sulfide, BaZrS3, has garnered significant attention in the scientific community due to its distinctive perovskite structure and several unique optoelectronic properties, making it a frontrunner in this domain of PV materials research. However, synthetic routes to these materials, especially as colloidal nanomaterials, remain limited, due in part to their high crystallization energy and oxophilicity. In this thesis, we have successfully devised solution-based approaches to synthesize colloidal nanomaterials of BaTiS3 and BaZrS3, including its titanium- and selenium alloyed phases. Our methodology involves utilizing reactive metal amide precursors in oleylamine, with diethylthiourea and trioctylphosphine selenide serving as sources for sulfur and selenium, respectively. Chapter I discusses the general background of current and emerging PV materials. Chapter II delves into various synthetic routes reported for inorganic ternary and binary sulfide and selenide nanomaterials, incorporating transition metals from groups 3, 4, and 5. This section also encompasses our synthetic methods for BaZrS3 and BaTiS3 colloidal nanomaterials. Chapter III provides an in-depth discussion of our developed techniques for producing nanorods and nanoparticles of barium titanium sulfide. In Chapter IV, our focus shifts to the synthesis of colloidal nanoparticles of barium zirconium sulfide perovskites. Additionally, Chapter V explores the synthesis of titanium and selenium alloyed barium zirconium sulfide. Finally, the synthesis of mixed halide lead perovskite nanocrystals, achieved through a postsynthetic anion-exchange method, is discussed in Appendix E.

Cette thèse est consacrée à l’étude de processus de concentration de solutions colloïdales par voie microfluidique, pour former des matériaux denses et structurés. A partir d’un outil basé sur la perméation de l’eau à travers le PDMS : le microévaporateur, nous proposons de contrôler le séchage de solution pour maîtriser la concentration de solutés afin de former des états denses organisés au choix, alternant cristaux et états amorphes de colloïdes. En adaptant les outils de microévaporation à différentes techniques d’observations, la nucléation et la croissance d’états denses ont été finement étudiées et correlées à un modèle simple de la microévaporation. Ces études expérimentales ont montré le contrôle précis qu’apporte le microévaporateur sur les cinétiques de concentration d’espèces chimiques pour la formation d’états denses de particules.Des études complémentaires ont aussi mis en évidence l’existence d’une dynamique de construction de cristaux colloïdaux avec des réorganisations au niveau du front ainsi qu’un effet de compaction présents lors de la croissance de l’état dense. / This work is devoted to studying processes of colloidal solutions concentration by microfluidic way to shape dense and organized states. Using a tool based on the water permeation through the PDMS: the microevaporator, we propose to control drying of solution for controlling solute concentration to form dense states as one chooses, alternating crystals and amorphous states of colloids.By adapting microevaporation tool at different observation techniques, nucleation and growth are particularly studied and correlated to a simple microevaporation model. This experimental work demonstrates the good control on kinetics of chemical species concentration offered by microevaporation, in order to shape dense states of particles.Further studies also reveal existence of a dynamic construction of colloidal crystal with some reorganization in the front growth and a compaction effect of the dense state during the growth.

Nous réalisons des simulations numériques de décompositions spinodales en dessous de la température de transition vitreuse. Nous étudions l'influence de cette transition sur la séparation de phase liquide-gaz. Ces études ont été motivées pour expliquer un mécanisme de formation de gels à partir de systèmes colloïdaux ayant un potentiel d'attraction à courte portée (systèmes colloïdes/polymères non-adsorbant) mis en évidence lors de récentes expériences mais dont les raisons étaient floues. Nos résultats confirment que la structure des gels est induite par la décomposition spinodale, tandis que l'arrêt de la dynamique due à la transition vitreuse fige le système en une structure bicontinue et empêche la séparation de phase d'arriver à terme. Une étude complète (diagramme des phases, structure, distribution des longueurs, distribution des densités, longueurs caractéristiques, taille des clusters, mécanisme d'évolution) de ces systèmes en fonction du temps, de la température et de la densité est réalisée. / We realize a numerical study of spinodal decomposition under glass transition. We study the influence of glass transition on liquid-gaz phase separation. Our motivation was to explain a gel formation mecanisim of colloidal systems with short range interaction (colloid/non-adsorbing polymer system) shown in recent experiments. Their authors suggested a mecanisim taht we corroborate in this thesis. Our results confirm that gel structure is shaped by spinodal decomposition, and then glass transition slow dynamics until system get pinned in a bicontinuous structure in one hand, and avoid complete liquid-gas separation in other hand. A complete study (phase diagram, structure, length distributions, density distributions, typical lengths, cluster size, evolution mecanisim) of those systems is done in function of time, temperature and density.

Gold nanoparticle has emerged as an attractive platform for drug delivery applications by complementing the existing drug delivery carriers. Currently, only a few gold nanoparticle-based anticancer drug delivery systems have been reported, compared to the polymer-based delivery systems. Additionally, there is still a lack of understanding for the behavior and fate of the gold-drug conjugate in the body that further attention is required. The overall goal of this thesis is to investigate the in vivo behavior of colloidal gold nanoparticle and its therapeutic efficacy in an animal model, especially in a drug delivery application. To achieve this goal, we investigated the feasibility of using colloidal gold nanoparticle as an anticancer agent delivery vehicle for treatment of cancer. Then, long-term clearance, toxicity, and biodistribution of colloidal gold nanoparticle were studied to further aid in understanding of using colloidal gold nanoparticle as a drug delivery platform. In particular, two representative sizes of gold nanoparticles, 5nm and 60nm, were investigated for the size effect on the therapeutic efficacy, toxicity, biodistribution, and clearance in cancer nanotherapy. We believe that nanoparticle size plays a critical role in not only delivering the drug to the target site but also determining the in vivo behavior such as biodistribution and clearance. By choosing an appropriate size scale for the system, we successfully used the small-sized gold nanoparticles for drug delivery applications, which also displayed no apparent toxicity with desirable clearance from the biological system. This work is significant by providing an insight on a potential ideal candidate for drug delivery carrier for cancer nanotherapy.