Dissertations / Theses on the topic 'Colloidal approaches'
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Derelli, Davide. "Self-assembly of colloidal particles - a combination of experimental and simulation approaches." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/18076/.
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In this project, self-assembly behaviour of colloidal particles was investigated by a combination of both computer simulations and experimental approach. In particular, a Brownian Dynamics algorithm was used to simulate either steep-repulsive spheres or spherocylinders in a shrinking spherical confinement. In accordance with literature, in the former case packed spheres were shown to crystallize into a distinctive icosahedral structure. In the latter study, spherocylinders clearly revealed a local tendency to form smectic layers. After the synthesis of micro-sized fluorescent-labelled silica spheres and rods, particle self-assembly in a spherical confinement was experimentally explored. While our selected method widely produced well-defined spherical supraparticles, it generally failed in inducing crystalline or liquid-crystalline ordering. This outcome was supposed to emerge due to fast compression of particles inside the confinement.
In the last part of the project, Brownian Dynamics simulations of mixtures of rods and spheres in a spherical confinement were performed. Our preliminary investigation unveiled a modest tendency for rod-rich mixtures to form a binary smectic configuration. However, same-shape phase separation prominently occurred for increasing fractions of spheres. Notably, a quantitative analysis on the simulated configurations was accomplished by introduction of a novel binary smectic local order parameter.
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Staicu, Lucian. "Production of colloidal biogenic elemental selenium and removal by different coagulation-flocculation approaches." Thesis, Paris Est, 2014. http://www.theses.fr/2014PEST1180/document.
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Le sélénium (Se) est un élément chalcogène avec un domaine de concentration étroit entre essentialité et toxicité. La toxicité est principalement liée à la spéciation chimique du Se qui évolue en fonction des conditions redox du milieu. Les formes oxyanioniques de Se, le sélénite (Se [IV], SeO32-) et le séléniate (Se [VI], SeO42-), sont solubles dans l'eau, biodisponibles et toxiques. En revanche, le sélénium élémentaire, Se(0), est insoluble et moins toxique. Néanmoins, les nanoparticules du Se(0) sont potentiellement dangereuses pour certains groupes des mollusques (comme les bivalves) et aussi pour les poissons. En outre, lorsque le Se(0) est rejeté dans les écosystèmes aquatiques, sa ré-oxydation jusqu'au sélénite et séléniate peut se produire. Le sélénium élémentaire d'origine biogénique Se(0) a été produit par la réduction de SeO42- dans des conditions anaérobies en utilisant un inoculum microbien mixte (boues granulaires) et par la réduction de SeO32- dans des conditions aérobies en utilisant une culture bactérienne pure (une nouvelle souche de Pseudomonas moraviensis identifiée et caractérisée pour la première fois dans cette thèse). Les deux types de Se(0) ont montré une forte stabilité colloïdale dans l'écart de pH variant de 2 à 12. La stabilité colloïdale est due à la charge négative (-15 mV à -30 mV) de la couche de biopolymère qui entoure Se(0) et à la taille nanométrique des particules de Se(0). La taille des particules de Se(0) produite par la boue anaérobie granulaire se situait entre 50 et 300 nm, avec une taille moyenne de 166 nm. A l'inverse, les nanoparticules de Se(0) produites par Pseudomonas moraviensis stanleyae sont caractérisées par un diamètre plus faible (~ 100 nm).Compte tenu des risques pour l'environnement engendrés par le relargage du Se(0) biogénique, des mesures appropriées doivent être mises en œuvre pour la séparation solide-liquide en utilisant une technologie efficace. Le potentiel de séparation solide-liquide de Se(0) généré a été évaluée par centrifugation, filtration, coagulation-floculation et électrocoagulation. Alors que toutes les approches présentent des rendements de séparation de Se(0) variables, l'électrocoagulation en utilisant des électrodes sacrificielles de fer a montré l'efficacité d'élimination le plus élevée (97%)Selenium (Se) is a chalcogen element with a narrow window between essentiality and toxicity. The toxicity is mainly related to the chemical speciation that Se undergoes under changing redox conditions. Se oxyanions, namely selenite (Se[IV], SeO32-) and selenate (Se[VI], SeO42-), are water-soluble, bioavailable and toxic. In contrast, elemental selenium, Se(0), is solid and less toxic. Nevertheless, Se(0) nanoparticles are potentially harmful as particulate Se(0) has been reported to be bioavailable to filter feeding mollusks (e.g. bivalves) and fish. Furthermore, Se(0) is prone to re-oxidation to toxic SeO32- and SeO42- when discharged into aquatic ecosystems. Biogenic Se(0) under investigation was produced by the reduction of Na2SeO4 under anaerobic conditions using a mixed bacterial inoculum (anaerobic granular sludge) and through the reduction of Na2SeO3 under aerobic conditions using a pure microbial culture (Pseudomonas moraviensis stanleyae, a novel strain identified and characterized for the first time herein). Both types of Se(0) showed strong colloidal stability within the 2-12 pH range. The colloidal stability is caused by the negatively charged (-15 mV to -30 mV) biopolymer layer covering biogenic Se(0) particles and by their nanometer size. The particle size of Se(0) produced by anaerobic granular sludge ranged between 50 and 300 nm, with an average size of 166 nm. Conversely, the Se(0) particles produced by Pseudomonas moraviensis stanleyae are characterized by a lower diameter (~ 100 nm).The solid-liquid separation potential of Se(0) was assessed by centrifugation, filtration, coagulation-flocculation and electrocoagulation. While all approaches can bring about Se(0) removal from suspension with various degrees of success, electrocoagulation using iron sacrificial electrodes showed the highest removal efficiency (97%). Because biogenic Se(0) is harmful to the environment, appropriate measures must be implemented for the solid-liquid separation using an efficient technology
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Yin, Yadong. "Self-assembly approaches to photonic structures /." Thesis, Connect to this title online; UW restricted, 2002. http://hdl.handle.net/1773/10603.
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Bleier, Blake J. "Droplet-Based Approaches to Probe Complex Behavior in Colloidal Fluids with High Composition Resolution." Research Showcase @ CMU, 2018. http://repository.cmu.edu/dissertations/1173.
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In this work, microfluidic and millifluidic droplets are utilized to study and control complex fluid behavior with high composition resolution. Different techniques are used on two length scales to create unique approaches towards the same goal of merging droplet-based experiments with classical colloidal characterization experiments. First, a microfluidic dehydrating droplet device is characterized and a procedure established by concentrating a phase separating organic-inorganic system on chip and using geometric calculations to determine composition. The device is then expanded to a more complex, particle-polymer system to investigate suspension stability and interparticle behavior. A model system containing silica particles and PEO polymer is found to transition from a bridging flocculation mechanism to polymer-coated particle jamming based on the mass ratio of polymer to particle. Lastly, a phase separating particle-polymer system consisting of polystyrene particles and hydroxyethyl cellulose is concentrated on-chip. Interparticle interactions are controlled by varying particle size, polymer size, and polymer type and the effects on phase behavior are examined. Droplet experiments are scaled-up to millifluidic droplets and concentration gradients are used to produce high composition resolution in place of time, used in the dehydrating microfluidic experiments. A novel, millifluidic containment device is created to study aggregation and sedimentation in droplets containing carbon black and OLOA surfactant suspended in dodecane. A slow increase in stabilization behavior is observed as opposed to the previously observed sharp “on-off” effect. The droplet production technique is then improved to achieve more complex composition paths and the device is expanded for a small angle neutron scattering (SANS) application. SANS is performed on flowing droplets with varying concentration to map interparticle interactions and phase behavior of complex particulate systems. Feasibility of device is demonstrated and preliminary model systems of silica particles and polymer, salt, and surfactant are analyzed and characterized.
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Sato, Ai. "Technological approaches for controlling foaming properties of food proteins toward on-site consumption." Doctoral thesis, Kyoto University, 2021. http://hdl.handle.net/2433/263709.
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Elsayed, Mustafa Mohammed Abdelaziz Verfasser], Reinhard H. H. [Akademischer Betreuer] [Neubert, Gregor [Akademischer Betreuer] Cevc, and Alfred [Akademischer Betreuer] Blume. "Analytical approaches to physicochemical characterization of colloidal drug carriers / Mustafa Mohammed Abdelaziz Elsayed. Betreuer: Reinhard Neubert ; Gregor Cevc ; Alfred Blume." Halle, Saale : Universitäts- und Landesbibliothek Sachsen-Anhalt, 2011. http://d-nb.info/1025202058/34.
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Williams, P. M. "Protein ultrafiltration : a colloidal interaction approach." Thesis, Swansea University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636643.
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The influence of the physicochemical conditions on the permeation rate in dead-end and cross flow ultrafiltration of protein dispersions is investigated. The rigorous mathematical models developed are based on sophisticated descriptions of the protein-protein interactions within the layer close to the membrane surface which is responsible for controlling the permeation rate. The calculations are expressed in terms of an osmotic pressure which accounts for the multiparticle electrostatic interactions, dispersion forces and configurational entropy. Electrostatic interactions are accounted for by a Wigner-Seitz cell approach including a numerical solution of the non-linear Poisson-Boltzmann equation. London-van der Waals forces are calculated using a computationally efficient means of approximating screened, retarded Lifshitz-Hamaker constants. Configurational entropy effects are calculated using an equation of state giving excellent agreement with molecular dynamic data. Electroviscous effects are also taken into account. These descriptions of colloidal interactions are used to develop a priori models, with no adjustable parameters, that allow quantitative prediction of the osmotic pressure and the rate of filtration of protein dispersions as a function of zeta potential (and hence pH), protein size, ionic strength, protein concentration, applied pressure and membrane resistance. The model shows good agreement with literature experimental data for the osmotic pressure of the protein bovine serum albumin (BSA). A further refinement to the models has been the development of a surface charge regulation model from knowledge of the amino acid groups giving rise to the protein charge. For cross flow ultrafiltration, the osmotic pressure is further used in the calculation of the gradient diffusion coefficient from the generalised Stokes-Einstein equation. The filtration models have been tested by conducting dead-end and cross flow ultrafiltration experiments with protein dispersions of BSA and lactoferrin. Good agreement between theory and experiment has been obtained for the dead-end model, but further work is required for the cross flow filtration model.
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Guarino, Andrew Joseph Wrenn Steven Parker. "A colloidal science approach to the study of atherosclerosis /." Philadelphia, Pa. : Drexel University, 2006. http://dspace.library.drexel.edu/handle/1860/723.
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Torrecilla, Paula Jauregi. "Colloidal gas aphrons (CGA) : a novel approach to protein recovery." Thesis, University of Reading, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387771.
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Zeidan, Michael. "Colloidal aggregation with application to soot mediated lubricating fluids : a multi-level simulation approach." Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.432657.
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Lopian, Tobias. "Characterization of a metal-extracting water-poor microemulsion." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT206/document.
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Le recyclage des terres rares à partir de déchets électroniques n'a toujours pas trouvé une réalisation industrielle significative. L'une des raisons est le manque de procédures de séparation optimisées en raison de connaissances fondamentales médiocres sur ces systèmes. En raison des similitudes chimiques et physiques de ces métaux, la conception d'une formulation efficace, adaptative et prédictive est toujours hors de portée des possibilités. L'interprétation supramoléculaire de la formation complexe dans la phase organique est de plus en plus importante au cours des dernières années. C'est l'approche la plus prometteuse permettant l'explication de divers phénomènes, tels que la formation de la troisième phase et les signaux forts dans de petites expériences de diffusion et de revenir à des méthodes bien connues de la science des tensioactifs. Notre contribution à une compréhension plus complète dans cette matière est l'analyse du comportement électrodynamique de ces phases et la corrélation de ces résultats avec les résultats des propriétés d'auto-assemblage et du transport de masse dans ces médias. Pour cette étude, nous avons spécifiquement conçu un modèle de référence, en passant un processus d'extraction à ses quatre composants fondamentaux: l'extracteur avant l'extraction (acide Di-(2-éthylhexyl) phosphorique, HDEHP), l'extrait après extraction (son sel de sodium, NaDEHP ), le toluène comme diluant apolaire et de l'eau. Un prisme de phase de Gibbs a été préparé (illustré sur la figure 1), où l'axe z donne le rapport de HDEHP à NaDEHP, ce qui représente le développement d'une extraction. Couvrant le domaine de basse fréquence, la spectroscopie d'impédance a été la méthode de choix afin de déterminer la conductivité dépendant de la fréquence. En utilisant la spectroscopie de relaxation diélectrique, nous révélons des processus dynamiques rapides à haute fréquence. Des mesures combinées SAXS et SANS ont été effectuées pour comparer les tendances électrodynamiques avec les propriétés d'agrégation et les interactions entre groupes. Deux phénomènes ont été identifiés comme responsables du profil de conductivité dans les systèmes micellaires inverse: la formation d'agrégats chargés par la dissimulation et la percolation. Tout au long du système de référence, ces deux processus ont été sondés en fonction de trois variables: la concentration totale d'agent d'extraction, le rapport eau-agent tensioactif et le rapport Na: H. En tant que résultat majeur, l'eau joue un rôle important dans les deux processus. En cas de percolation, les agrégats inverse ne peuvent pas fusionner en l'absence d'eau. Par conséquent, la conductivité électrique est interdite. Dans les systèmes dilués, l'eau facilite le processus de dismutation, entraînant une augmentation de la conductivitéRecycling of rare earths from electronic waste has still not found a significant industrial realization. One reason is the lack of optimized separation procedures due to poor fundamental knowledge on these systems. Due to the chemical and physical similarities of these metals, designing an efficient, adaptive and predictive formulation is still out of scope of possibilities. The supramolecular interpretation of complex-formation in the organic phase has gained an increasing importance in the last years. It is the most promising approach allowing the explanation of diverse phenomena, such as third phase formation and strong signals in small scattering experiments and to revert to methods well known from surfactant science. Our contribution towards a more complete understanding in this matter is the analysis of the electrodynamic behaviour of such phases and the correlation of these findings with the results of self-assembly properties and mass transport in these media.For this study, we specifically designed a reference model, breaking an extraction process down to its four fundamental components: The extractant before extraction (Di-(2-ethylhexyl)phosphoric acid, HDEHP), the extractant after extraction (its sodium salt, NaDEHP), toluene as apolar diluent and water. A Gibbs phase prism has been prepared (illustrated in Figure 1), where the z-axis gives the ratio of HDEHP to NaDEHP, representing the development of an extraction. Covering the low frequency-domain, impedance spectroscopy has been the method of choice in order to determine the frequency-dependent conductivity. Using dielectric relaxation spectroscopy, we reveal fast dynamic processes at high frequencies. Combined SAXS and SANS measurements have been performed to compare the electrodynamic trends with aggregation properties and intercluster interactions.Two phenomena have been identified to be responsible for the conductivity profile in reverse micellar systems: the formation of charged aggregates through dismutation and percolation. Throughout the reference system, these two processes have been probed as function of three variables: total extractant concentration, the water-to-surfactant ratio and the Na:H-ratio. As a major result, water plays a significant role in both processes. In case of percolation, reverse aggregates are not able to merge in the absence of water. Therefore, electrical conductivity is prohibited. In dilute systems, water facilitates the dismutation–process leading to an increase in conductivity
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Johnson, Elizabeth Edna. "Colloidal gas aphron foams : a novel approach to a hydrogel based tissue engineered myocardial patch /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/10579.
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Olivier, Bernard J. "In situ measurements of the approach to scaling of colloidal cluster size distributions during aggregation." Kansas State University, 1987. http://hdl.handle.net/2097/18447.
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Sanci, Rukiye. "Synthesis Of Colloidal Silver Particles With Different Sizes By Seeding Approach For Surface Enhanced Raman Scattering (sers) Studies." Master's thesis, METU, 2009. http://etd.lib.metu.edu.tr/upload/3/12611076/index.pdf.
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In this study, silver nanorods and nanospheroids were prepared both in aqueous solution and on the surface of glass slides through seed-mediated growth approach at room temperature and used as a surface enhanced Raman scattering (SERS) substrate. The synthesis of metallic nanorods was started with the production of silver nanospheres as seed utilizing sodium borohydride and trisodium citrate as reducing and capping agents, respectively. These seeds were then added to a growth solution containing additional silver salt, ascorbic acid and cetyltrimethylammonium bromide (CTAB.)
Nanorod preparation conditions were first optimized in solution phase. The plasmon absorption of the formed nanocrystals was monitored by UV-Visible spectrometry. The largest red shift in the longitudinal plasmon resonance absorption of silver nanostructures was tried to be achieved in order to realize the highest electromagnetic enhancement in Raman measurements. The images of the formed nanorods were recorded using field emission scanning electron microscopy (FE-SEM).
The optimized colloidal growth conditions were adopted for the growth of nanorods on the surface of the glass substrate. Sol-gel coated glass slides were used in order to increase the porosity on the surface for an effective seeding process. We reported the development of a novel SERS substrate prepared by growing silver nanorods directly on the surface of glass surface without using any linker molecule.
The SERS performances of the nanorod growth surfaces were evaluated with crystal violet (CV), brilliant cresyl blue (BCB) and benzoic acid (BA). Some modifications such as the increase in the AgNO3 concentration in the growth solution and the addition of hydrocarbons to the growth solution were investigated for the enhancement of the SERS signal. The intense spectra obtained for the model compounds demonstrated the efficiency of the prepared substrate for the SERS enhancement and its potential as a SERS detection probe for chemical and biological analysis.
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Zengin, Adem. "Modelling the colloidal behaviour of food systems in the presence of fragmented proteins/macromolecules : a self-consistent field approach." Thesis, University of Leeds, 2016. http://etheses.whiterose.ac.uk/13249/.
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This thesis presents a theoretical examination of the possibility that the fragments of a protein may provide better colloidal stability than the intact protein itself in the case of αs1-casein. It more generally considers the surface adsorption behaviour of fragmented proteins. In colloidal systems the polymers are mostly present as polydisperse entities. Polydispersity can either be naturally present or be the result of fragmentation, as happens for food proteins during enzymatic modification. Majority of proteins do not possess the most optimum primary structure expected of an ideal colloidal stabiliser. More desirable surface functionality maybe achieved by hydrolysis of edible proteins. For the theoretical examination of this argument we had to extend and develop a new Self Consistent Field (SCF) approach which also had to be validated first. Although this new approach is an extension of the traditional SCF approach, it is capable of modelling highly polydisperse systems in a manner not currently possible with the more usual technique. In this preliminary work we present the results of our method for both homopolymers and proteins. In the homopolymer case, we investigate how the preferential adsorption of homopolymer fragments is influenced by various parameters such as solution concentration, degree of hydrolysis (DH), the intact size of the original homopolymer and the strength of affinity of monomers to the surface. The colloidal stabilising and surface adsorption properties of fragmented proteins were investigated taking the bovine milk protein αs1-casein as an example. The protein was fragmented by selective single bond and also non-selective multiple bond hydrolysis, assumed to be induced by the action of enzyme trypsin. The investigation was carried out at different levels of hydrolysis (DH) and various pH values. We find that the non-selective peptide bond hydrolysis in the case of αs1-casein did not provide a better colloidal stability compared to the intact αs1-casein, at none of the pH values studied here. However, it was shown that a better colloidal stability can be achieved by the selective peptide bond cleavage of particular bonds.
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Narayanan, Vishak. "A Colloidal Approach to Study the Dispersion Characteristics of Commercially Processed Nanocomposites: Effect of Mixing Time and Processing Oil." University of Cincinnati / OhioLINK, 2018. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1535703328357695.
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Dorney, Kevin Michael. "A Chemical Free Approach for Increasing the Biochemical Surface-Enhanced Raman Spectroscopy (SERS)-Based Sensing Capabilities of Colloidal Silver Nanoparticles." Wright State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=wright1401206511.
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Dev, Choudhury Bikash. "Deterministic Silicon Pillar Assemblies and their Photonic Applications." Doctoral thesis, KTH, Halvledarmaterial, HMA, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-184709.
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It is of paramount importance to our society that the environment, life style, science and amusement flourish together in a balanced way. Some trends in this direction are the increased utilization of renewable energy, like solar photovoltaics; better health care products, for example advanced biosensors; high definition TV or high resolution cameras; and novel scientific tools for better understanding of scientific observations. Advancement of micro and nanotechnologies has directly and positively impacted our stance in these application domains; one example is that of vertical periodic or aperiodic nano or micro pillar assemblies which have attracted significant research and industrial interest in recent years. In particular, Si pillars are very attractive due to the versatility of silicon. There are many potential applications of Si nanopillar/nanowire assemblies ranging from light emission, solar cells, antireflection, sensing and nonlinear optical effects. Compared to bulk, Si pillars or their assemblies have several unique properties, such as high surface to volume ratios, light localization, efficient light guiding, better light absorption, selective band of light propagation etc. The focus of the thesis is on the fabrication of Si pillar assemblies and hierarchical ZnO nanowires on Si micro structures in top-down and bottom-up approaches and their optical properties and different applications. Here, we have investigated periodic and aperiodic Si nano and micro structure assemblies and their properties, such as light propagation, localization, and selective guiding and light-matter interaction. These properties are exploited in a few important optoelectronic/photonic applications, such as optical biosensors, broad-band anti-reflection, radial-junction solar cells, second harmonic generation and color filters. We achieved a low average reflectivity of ~ 2.5 % with the periodic Si micropyramid-ZnO NWs hierarchical arrays. Tenfold enhancement in Raman intensity is also observed in these structures compared to planar Si. These Si microstructure-ZnO NW hierarchical structures can enhance the performance and versatility of photovoltaic devices and optical sensors. A convenient top-down fabrication of radial junction nanopillar solar cell using spin-on doping and rapid thermal annealing process is presented. Broad band suppressed reflection, on average 5%, in 300- 850 nm wavelength range and an un-optimized cell efficiency of 6.2 % are achieved. Our method can lead to a simple and low cost process for high efficiency radial junction nanopillar solar cell fabrication. Silicon dioxide (SiO2) coated silicon nanopillar (NP) arrays are demonstrated for surface sensitive optical biosensing. Bovine serum albumin (BSA)/anti-BSA model system is used for biosensing trials by photo-spectrometry in reflection mode. Best sensitivity in terms of limit of detection of 5.2 ng/ml is determined for our nanopillar biosensor. These results are promising for surface sensitive biosensors and the technology allows integration in the CMOS platform. Si pillar arrays used for surface second harmonic generation (SHG) experiments are shown to have a strong dependence of the SHG intensity on the pillar geometry. The surface SHG can be suitable for nonlinear silicon photonics, surface/interface studies and optical sensing. Aperiodic Si nanopillar assemblies in PDMS matrix are demonstrated for efficient color filtering in transmission mode. These assemblies are designed using the ‘‘molecular dynamics-collision between hard sphere’’ algorithm. The designed structure is modeled in a 3D finite difference time domain (FDTD) simulation tool for optimization of color filtering properties. Transverse localization effect of light in our nanopillar color filter structures is investigated theoretically and the results are very promising to achieve image sensors with high pixel densities (~1 µm) and low crosstalk. The developed color filter is applicable as a stand-alone filter for visible color in its present form and can be adapted for displays, imaging, smart windows and aesthetic applications.QC 20160407
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Lee, Seung Geol. "Structure-property relationship of hydrogel: molecular dynamics simulation approach." Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/44844.
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We have used a molecular modeling of both random and blocky sequence hydrogel networks of poly(N-vinyl-2-pyrrolidone-co-2-hydroxyethyl methacrylate) (P(VP-co-HEMA)) with a composition of VP:HEMA = 37:13 to investigate the effect of the monomeric sequence and the water content on the equilibrium structures and the mechanical and transport properties by full-atomistic molecular dynamics (MD) simulations. The degree of randomness of the monomer sequence for the random and the blocky copolymers, were 1.170 and 0.104, respectively, and the degree of polymerization was fixed at 50. The equilibrated density of the hydrogel was found to be larger for the random sequence than for the blocky sequence at low water contents (< 40 wt %), but this density difference decreased with increasing water content. The pair correlation function analysis shows that VP is more hydrophilic than HEMA and that the random sequence hydrogel is solvated more than the blocky sequence hydrogel at low water content, which disappears with increasing water content. Correspondingly, the water structure is more disrupted by the random sequence hydrogel at low water content but eventually develops the expected bulk-water-like structure with increasing water content. From mechanical deformation simulations, the stress-strain analysis showed that the VP is found to relax more efficiently, especially in the blocky sequence, so that the blocky sequence hydrogel shows less stress levels compared to the random sequence hydrogel. As the water content increases, the stress level becomes identical for both sequences. The elastic moduli of the hydrogels calculated from the constant strain energy minimization show the same trend with the stress-strain analysis. Ascorbic acid and D-glucose were used to study the effect of the monomeric sequence on the diffusion of small guest molecules within the hydrogels. By analyzing the pair correlation functions, it was found that the guest molecule has greater accessibility to the VP units than to the HEMA units with both monomeric sequences due to its higher hydrophilicity compared to the HEMA units. The monomeric sequence effect on the P(VP-co-HEMA) hydrogel is clearly observed with 20 wt % water content, but the monomeric sequence effect is significantly reduced with 40 wt % water content and disappears with 80 wt % water content. This is because the hydrophilic guest molecules are more likely to be associated with water molecules than with the polymer network at the high water content. By analyzing the mean square displacement, the displacement of the guest molecules and the inner surface area, it is also found that the guest molecule is confined in the system at 20 wt % water content, resulting in highly anomalous subdiffusion. Therefore, the diffusion of the guest molecules is directly affected by their interaction with the monomer units, the monomeric sequence and the geometrical confinement in the hydrogel at a low water content, but the monomeric sequence effect and the restriction on the diffusion of the guest molecule are significantly decreased with increasing the water content.
We also investigated the de-swelling mechanisms of the surface-grafted poly(N-isopropylacrylamide) (P(NIPAAm)) brushes containing 1300 water molecules at 275 K, 290 K, 320 K, 345 K, and 370 K. We clearly observed the de-swelling of the water molecules for P(NIPAAm) above the lower critical solution temperature (LCST) (~305 K). Below the LCST, we did not observe the de-swelling of water molecules. Using the upper critical solution temperature (UCST) systems (poly(acrylamide) brushes) for comparison purposes, we did not observe the de-swelling of water molecules at a given range of temperatures. By analyzing the pair correlation functions and the coordination numbers, the de-swelling of the water molecules occurred distinctly around the isopropyl group of the P(NIPAAm) brush above the LCST because C(NIPAAm) does not offer sufficient interaction with the water molecules via the hydrogen bonding type of secondary interaction. We also found that the contribution of the N(NIPAAm)-O(water) pair is quite small because of the steric hindrance of the isopropyl group. By analyzing the change in the hydrogen bonds, the hydrogen bonds between polar groups and water molecules in the P(NIPAAm) brushes weaken with increasing temperature, which leads to the de-swelling of the water molecules out of the brushes above the LCST. Below the LCST, the change in the hydrogen bonds is not significant. Again, the contribution of the NH(NIPAAm)-water pairs is insignificant; the total number of hydrogen bonds is ~20, indicating that the interaction between the NH group and the water molecules is not significant due to steric hindrances. Lastly, we observed that the total surface area of the P(NIPAAm) brushes that is accessible to water molecules is decreased by collapsing the brushes followed by the de-swelling of water molecules above the LCST.
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Spreng, Benjamin [Verfasser], and Gert-Ludwig [Akademischer Betreuer] Ingold. "Plane-wave approach to the Casimir interaction between colloid particles / Benjamin Spreng ; Betreuer: Gert-Ludwig Ingold." Augsburg : Universität Augsburg, 2021. http://d-nb.info/1233601164/34.
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Scheele, Marcus [Verfasser], and Horst [Akademischer Betreuer] Weller. "Ein kolloidchemischer Ansatz zur Darstellung nanostrukturierter Thermoelektrika mit verbesserter Gütezahl = A colloidal chemistry approach to nanostructured thermoelectric materials with enhanced figure of merit / Marcus Scheele. Betreuer: Horst Weller." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2011. http://d-nb.info/1020383178/34.
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Lazzaro, Fanny. "Comprendre les comportements des micelles de caséines dans des environnements variés, de leur équilibre minéral à leurs propriétés colloïdales et fonctionnelles : émulsion et coagulation présure." Thesis, Rennes, Agrocampus Ouest, 2017. http://www.theses.fr/2017NSARB301/document.
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Les micelles de caséines, composées de caséines, minéraux et eau, sont en équilibres dynamiques, elles échangent en permanence de leur matière avec leur environnement. Les micelles de caséines possèdent d’intéressantes fonctionnalités pour la fabrication de produits laitiers, telles que leur capacité à stabiliser des émulsions et à former des gels sous l’action de la présure. Des changements environnementaux, variations de pH, additions de sels ou d’agents chélatants, affectent les équilibres des micelles et induisent des modifications de leurs compositions et propriétés colloïdales. Ces changements modifient également leurs propriétés fonctionnelles, bien que cet aspect soit peu décri. Le but de ce projet était de comprendre les relations liant l’environnement, l’équilibre minéral, les propriétés colloïdales et fonctionnelles des micelles de caséines. L’impact de cinq facteurs (pH, Na3Cit, NaCl, CaCl2, MgCl2) modifiant les micelles fut étudié en focalisant sur leurs propriétés émulsifL’acidification et l’addition de Na3Cit ont causé les modifications minérales les plus importantes en solubilisant le phosphate de calcium micellaire. Le premier conduisit au « gonflement » des micelles alors que l’agent chélatant causa leur dissociation en petits agrégats. L’ajout de NaCl n’eut aucun impact sur le contenu minéral des micelles mais provoqua aussi la libération d’agrégats, révélée par cryo microscopie électronique et diffusion de rayons-X aux petits angles. Le rôle du phosphate de calcium sur les fonctionnalités fut confirmé et l’étude révéla l’importance de contrôler la libéCaseins micelles, composed of caseins, minerals and water, are under dynamic equilibria, they constantly exchange materials with their surrounding environments. In addition, casein micelles possess valuable functionalities in regards to the formation of dairy products, such as the ability to stabilize emulsions or to form rennet gels. Environmental changes, such as variations in pH, additions of salts or chelating agents, affect the casein micelles equilibria and lead to modifications in their compositional and colloidal properties. Such changes also modify their functional properties, although this aspect is poorly described in the literature. This project aimed to understand the relationships that link the environmental modifications, the mineral balance, the colloidal and functional properties of the casein micelles. The impact of five modifying factors (pH, Na3Cit, NaCl, CaCl2, MgCl2) of the casein micelles were studied and the focus was placed on emulsion and rennet coagulation fuThe former only induce the swelling of casein micelles while the latter led to their disruption into smaller aggregates. NaCl had no impact on the micellar mineral content but also caused the release of small aggregates, as revealed by electronic microscopy and small angle X-ray scattering analyses. The decisive role of micellar calcium phosphate on the functionalities was confirmed and this study highlighted the importance of monitoring the release of small aggregates, as they strongly affected emulsions stability and gels firmness. CaCl2 and MgCl2 additions slightly increased the mineral c
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Stoll, Madeleine [Verfasser], Thorsten [Gutachter] Schaefer, Eva [Gutachter] Schill, and Ruben [Gutachter] Kretzschmar. "Colloid mobility controlling processes in single fractures : a bottom-up approach / Madeleine Stoll ; Gutachter: Thorsten Schaefer, Eva Schill, Ruben Kretzschmar." Jena : Friedrich-Schiller-Universität Jena, 2018. http://d-nb.info/1170395538/34.
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Zhou, Dan [Verfasser], Irina [Akademischer Betreuer] Engelhardt, Irina [Gutachter] Engelhardt, and Martin [Gutachter] Sauter. "Development of numerical methods and approaches to simulate colloid transport and stream-aquifer interaction in heterogeneous natural soils / Dan Zhou ; Gutachter: Irina Engelhardt, Martin Sauter ; Betreuer: Irina Engelhardt." Berlin : Technische Universität Berlin, 2018. http://d-nb.info/1156184711/34.
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Jarray, Ahmed. "Mesoscopic modeling, experimental and thermodynamic approach for the prediction of agglomerates structures in granulation processes." Phd thesis, Toulouse, INPT, 2015. http://oatao.univ-toulouse.fr/15112/1/jarray.pdf.
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Wet granulation process requires the addition of a coating agent or binder, typically composed of surfactants, water, plasticizers and fillers. In dry granulation however, the coating agent is added to the system in the form of fine solid particles. Our goals are to investigate the particles behaviour and agglomeration mechanism in dry and aqueous systems at the micro and meso scales, and also, to develop predictive methodologies and theoretical tools of investigation allowing to choose the adequate binder and to formulate the right coating solution. In this study we chose materials widely used in food and pharmaceutical industries, including; coating agents such as Hydroxypropyl-methylcellulose (HPMC) and Ethyl cellulose (EC), binders such as Polyvinylpyrrolidone (PVP) and Microcrystalline cellulose (MCC), hydrophobic filler such as Stearic acid (SA) and plasticizer such as Polyethylene glycol (PEG). A successful granulation requires good affinity between host and guest particles. In this context, in the first part of this work, two approaches to predict the binder-substrate affinity in dry and in aqueous media were compared; one based on the work of adhesion and the other based on the ideal tensile strength. The concept of ideal tensile strength was extended to ternary systems and applied for granulation in aqueous media. The developed approaches were thereafter tested for various systems (composed of PVP, MCC, HPMC, SA, EC, PEG and water) and compared to experimental observations. Approaches yielded results in good agreement with the experimental observations, but the work of adhesion approach might give more accurate affinity predictions on the particles affinity than the ideal tensile strength approach. Both approaches predicted that HPMC is a good binder for MCC. Results also indicated that PEG has a good affinity with HPMC and SA. In a second part of our work, we used mesoscale simulations and experimental techniques to investigate the structure of agglomerates formed in aqueous colloidal formulations used in coating and granulation processes. For the simulations, dissipative particle dynamics (DPD) and a coarse-grained approach were used. In the DPD method, the compounds were described as a set of soft beads interacting according to the Flory-Huggins model. The repulsive interactions between the beads were evaluated using the solubility parameter (δ) as input, where, δ was calculated by all-atom molecular simulations. The mesoscale simulation results were compared to experimental results obtained by Cryogenic-SEM, particle size distribution analysis and DSC technique. According to the DPD simulations, HPMC polymer is a better stabilizing agent for SA than PVP and MCC. In addition, HPMC is able to cover the SA particle with a thick layer ant to adsorb in depth into its inner core, preventing SA agglomeration and crystal growth. But, for high amounts of SA (above 10% (w/w)), HPMC is unable to fully stabilize SA. We also found that PEG polymer diffuses inside HPMC chains thereby extending and softening the composite polymer. Experimental results presented similar trends; particle size distribution analysis showed that in the presence of HPMC, for low percentages of SA (below 10% (w/w)), the majority of SA particles are below 1 μm in diameter. SEM images revealed that HPMC surrounds SA crystals with a hatching textured film and anchors on their surface.
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Kirillova, Alina, Georgi Stoychev, and Alla Synytska. "Programmed assembly of oppositely charged homogeneously decorated and Janus particles." Royal Society of Chemistry, 2016. https://tud.qucosa.de/id/qucosa%3A36153.
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The exploitation of colloidal building blocks with morphological and functional anisotropy facilitates the generation of complex structures with unique properties, which are not exhibited by isotropic particle assemblies. Herein, we demonstrate an easy and scalable bottom-up approach for the programmed assembly of hairy oppositely charged homogeneously decorated and Janus particles based on electrostatic interactions mediated by polyelectrolytes grafted onto their surface. Two different assembly routes are proposed depending on the target structures: raspberry-like/half-raspberry-like or dumbbell-like micro-clusters. Ultimately, stable symmetric and asymmetric microstructures could be obtained in a well-controlled manner for the homogeneous–homogeneous and homogeneous–Janus particle assemblies, respectively. The spatially separated functionalities of the asymmetric Janus particle-based micro-clusters allow their further assembly into complex hierarchical constructs, which may potentially lead to the design of materials with tailored plasmonics and optical properties.
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Asokan, Subashini. "Chemical processing of colloidal cadmium selenide nanoparticles: New approaches to dimensional and morphological control." Thesis, 2008. http://hdl.handle.net/1911/22180.
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Cadmium selenide (CdSe) quantum dots (QDs) are colloidal semiconductor nanoparticles (NPs) that are nanometer sized fragments of the corresponding bulk crystals. They are being probed as a very interesting system for their applications in LEDs, solar cells and biomedical labeling because of their rich photophysics arising from their size dependent optical and electronic properties and flexible processing chemistry. 1-Octadecene was the only non-coordinating solvent used for the synthesis of CdSe NPs. It was imperative to understand the chemistry of synthesis of CdSe NPs using other non-coordinating solvents. Also, there is a constant search for the greener, cheaper, reproducible and scalable methods for the synthesis of CdSe NPs while not compromising on their quality. Towards the above mentioned goals, the use of heat transfer fluids was successfully demonstrated as cost-effective alternative solvents for quantum dot synthesis. Heat transfer fluids (HTF) are a class of organic liquids commonly used in chemical process industries to transport heat between unit operations. The solvents were found suitable for the hot injection synthesis of QDs while reducing the cost of the raw materials. These solvents were found to slow the growth kinetics of the CdSe NPs, leading to greater control over QD diameter.
Although the chemistry of synthesis of CdSe spherical and rod shaped particles were well understood, the synthesis of tetrapod shaped NPs with uniform size and shape is especially difficult to carry out at a large scale. Post-synthesis separation can be applied though this leads to additional processing steps and reduced particle yields. Cationic surfactant ligands were discovered to lead to the successful formation of tetrapod shaped CdSe NPs with highly uniform arm lengths, arm widths and shape. Typical selectivity values for the tetrapod morphology exceeded 90%, much higher than the previously reported values of 40%. The cationic surfactant ligands were found to induce anisotropy during the growth of the CdSe NPs, with cetyltrimethylammonium bromide (CTAB) and didodecyldimethylammonium bromide (DDAB) leading to the specific tetrapod shape. Optimization of the synthesis procedure led to the control over the range of dimensions of the tetrapod shaped particles. The uniformity of size and shape of the CdSe tetrapodal NPs were found to be very sensitive to the ratio of the surfactants and the precursors. It was also observed that the presence of the cationic surfactants led to the exclusive formation of zinc-blende nuclei which is indispensable for the growth of nuclei into tetrapodal NPs. The growth of CdSe tetrapodal NPs from the preformed zinc-blende CdSe NPs, just by the addition of CTAB, demonstrated the crucial role of the cationic surfactants in inducing anisotropy. These findings were helpful in gaining insight in to the nucleation and growth of the anisotropic nanoparticles.
These new methods should lead to improvements in current synthesis methods of tetrapodal shaped CdSe NPs, enabling the faster development of polymer/tetrapod photovoltaic devices. These results may be applicable to other compositions, leading to opportunities for large-scale application of shaped NPs.
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Seyed, Shariatdoust Mirali. "Novel approaches to plasmonic enhancement applications: upconverters, 2D materials and tweezers." Thesis, 2021. http://hdl.handle.net/1828/13352.
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In this thesis, the local field enhancement from multiple plasmonic structures were studied in different experiments. A new approach was applied to enhance the emission from upconverting nanoparticles to harvest energy from photons below the bandgap. A novel nanofabrication method was introduced to make double nanoholes for use in optical trapping, which was implemented to observe the nonlinear response from 2D materials and the enhanced emission from upconverting single nanoparticles. This method makes a large amount of apertures and is inexpensive. Selective plasmon-enhanced emission from erbium-doped nanoparticles using gold nanorods was demonstrated. Upconversion nanoparticles were excited with a dual-wavelength source of 1520~nm and 1210~nm simultaneously. The power dependence of the observed upconversion emission confirmed the contribution of both excitation bands in the upconversion process. Gold nanorods with resonances at 980~nm and 808~nm were implemented to selectively enhance the upconversion emission in order to harvest light with Si and GaAs solar cells, respectively. I also used colloidal lithography to fabricate double nanoholes which were plasmonic structures used for protein and nanoparticle trapping. This bottom-up technique enabled the fabrication of a large number of structures at low cost. Plasma etching of polystyrene nanoparticles using this technique tuned the cusp separation of double nanoholes down to 10~nm. The smaller cups separation enables to have more confined field in the gap which can be used in plasmonic sensing and plasmon enhanced upconversion processes. This technique can be used to fabricate plasmonic structures for nanoparticle trapping, spectroscopy, and sensing. In the next project, hexagonal boron nitride nanoflakes were trapped in a double nanohole fabricated with the colloidal lithography method. A second harmonic signal was detected at 486.5~nm where the particle was trapped and pumped with an ultra-low power laser at 973~nm. The power dependence measurements supported the second order process for second harmonic generation. Finite-difference time-domain (FDTD) simulations showed a 500-fold field intensity enhancement at the fundamental wavelength and a 450-fold enhancement in the Purcell factor at the second harmonic generation wavelength. This scheme is promising for ultra-fast imaging nonlinear optics technologies. In the last project, colloidal lithography double nanoholes were used to trap upconverting nanocrystals. Colloidal lithography double nanoholes with 32~nm cusp separation achieved 50 times larger emission compared to rectangular apertures. FDTD simulations showed the largest field enhancement in the aperture with the largest upconversion enhancement. 1550~nm emission from the trapped nanoparticle can be used as single-photon source.Graduate
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Jiang, Peng. "Colloidal crystal approach to the fabrication of photonic band gap materials." Thesis, 2001. http://hdl.handle.net/1911/17980.
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Planar single-crystalline colloidal crystals are fabricated by exploiting the spontaneous crystallization of monodisperse silica spheres into close-packed arrays using a convective self-assembly method. Film thicknesses ranging from single monolayers to over 200 layers can be precisely controlled through varying solution concentration and colloid diameter. These high quality periodic arrays exhibit partial photonic band gaps, whose positions and band width depends on the sphere diameters and the number of layers. Their optical transmission is well described by the scalar wave approximation to Maxwell's equations. The thickness dependence of the photonic band gap has also been studied for the first time.
Superlattice colloidal crystals comprised of alternating layers of different sphere sizes can also be formed by the convective self-assembly method. The resulting photonic crystal structures exhibit optical properties which resemble the superposition of the properties of each individual component, with additional structure that suggests the onset of superlattice-type miniband formation. These superlattice structures thus provide a new way to couple light into and out of photonic crystals.
These planar colloidal films are then used as scaffolds to make macroporous materials with crystalline arrays of voids. Macroporous polymers are formed by filling the interstitial area with monomer which is subsequently polymerized. The silica templates can be removed by etching with hydrofluoric acid. The large voids defined by the silica colloids are not isolated, but rather interconnected by a network of monodisperse smaller pores whose sizes can be controlled by varying the polymerization temperature. These membranes exhibit striking optical properties and their photonic band gap behavior agrees well with theory.
A seeded electroless deposition technique has also been developed for forming macroporous metal membranes. The gold particles attached to the thiol-coated silica colloidal crystals can catalyze the electroless deposition of metals (Ag, Au, Cu, Ni, Co, Pt) inside the arrays and lead to fully dense macroporous metallic films after silica removal. These samples are mechanically robust, electrically active, and possess unusual diffractive optical properties.
The macroporous polymers are again used as hosts to grow a wide variety of complex and unusual colloidal structures. This modern "lost-wax" method effectively capitalizes on the perfection of the starting colloids and the resulting template voids to form monodisperse colloids and their colloidal crystals. A wide variety of highly monodisperse inorganic, polymeric and metallic solid and core-shell colloids, as well as hollow colloids with controllable shell thickness and their colloidal crystals can be made. The polymer template can be uniformly deformed to alter colloidal shape and elliptical particles with precisely controlled aspect ratios are formed for the first time. The hollow sphere titania colloidal crystals exhibit partial photonic band gaps, whose spectral position and width depend on the thickness of the shell and on the overlap between adjacent spheres, in a manner consistent with numerical simulations.
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Lin, Chun-Ying, and 林俊穎. "Investigation of deposition process for colloidal articles using Monte Carlo approach." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/71206960243132234275.
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碩士元智大學
化學工程與材料科學學系
98
We developed a numerical model for TiO2 colloid particle distribution and sedimentation in aqueous solution by using kinetic Monte-Carlo algorithm. The system was assumed these particles were influenced by the Van der Waals and particle-particle electrostatic forces. The particle sedimentation process was calculated with the consideration of Van der Waals potential and electrostatic potential in the following study. Results show that the particles will be aggregated together whenever the Van der Waals forces present in the system only; while the particles can be dispersed by the electrostatic forces. After applying the two-stage process of surface potential, we can lower the number of vacant sites. If we applied three-stage process of surface potential before whole system reaching stability, the number of vacant sites increase. These results can be applied in the particle self-assembly process system.
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Bessa, Ricardo Sá. "A biophysical approach to mitochondrial gene therapy: gemini surfactant-based colloidal vectors." Master's thesis, 2016. https://repositorio-aberto.up.pt/handle/10216/91003.
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Bessa, Ricardo Sá. "A biophysical approach to mitochondrial gene therapy: gemini surfactant-based colloidal vectors." Dissertação, 2016. https://repositorio-aberto.up.pt/handle/10216/91003.
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Haque, Munima. "A colloidal science approach to characterize the nanoscale aggregation behavior of corn protein zein /." 2009. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3362917.
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Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2009.Source: Dissertation Abstracts International, Volume: 70-06, Section: B, page: 3637. Adviser: K. D. Bhalerao. Includes bibliographical references (leaves 69-78) Available on microfilm from Pro Quest Information and Learning.
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Mallory, Stewart Anthony. "An Active Approach to Engineering the Microscopic." Thesis, 2017. https://doi.org/10.7916/D8D22955.
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Active colloids, which can be thought of as the synthetic analog of swimming bacteria, exhibit remarkable collective behavior. Using a combination of computer simulations and analytical theory, I have looked to provide quantitative answers to fundamental questions concerning the phase behavior and material properties of active suspensions. A primary focus of my Ph.D work has been devoted to developing novel techniques to exploit the active nature of these particles to manipulate and self-assemble matter at the colloidal scale. In the introductory chapter, I discuss recent advances in the self-assembly of self-propelled colloidal particles and highlight some of the most exciting results in this field. The remaining chapters are each self-contained and focus on a particular topic within active colloidal self-assembly. These chapters are ordered in terms of system complexity, and begins with characterizing the thermomechanical properties of an ideal active fluid. The next three chapters are centered around characterizing the effective interactions induced by an active suspension. The last two chapters focus on using self-propulsion as a tool to improve colloidal self-assembly, and understanding the interplay between self-propulsion and anisotropic pair interaction.
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Ng, Sio-kit, and 吳紹傑. "Effective electrostatic interactions between 2-D colloid particles: a modeling approach." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/98385187035370582656.
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碩士國立中央大學
生物物理研究所
98
Interaction among charged colloidal particles has been investigated for long. One remarkable success, the so-called DLVO theory, considered the effects of both the van der Waals attraction and the screened Coulomb repulsion. In our current work, both the attractive and repulsive parts of the effective potential energy are observed while we consider the electrostatic effect only. In our model, we investigate the regime where the electrostatic interaction dominates and the counter-ions condense or fluctuate nearby each macro-ion. We use Monte Carlo simulations to obtain the average electrostatic interactions versus the distance between two macro-ions embedded in 2-dimensions. When the number of counter-ions is small, we obtain a short-range attraction and long-range repulsion. However, the attraction tends to vanish when the number of counter-ions increases. We provide possible scenarios for the sources of the attraction and repulsion.
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Chen, Huaiqun. "Prediction Of Permeate Flux Decline In Crossflow Membrane Filtration Of Colloidal Suspension: A Radial Basis Function Neural Network Approach." Thesis, 2005. http://hdl.handle.net/10125/10427.
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Filby, André [Verfasser]. "Interaction of colloids with mineral surfaces : a microscopical and nanoscopical approach / von André Filby." 2009. http://d-nb.info/999417835/34.
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