This document describes an experimental investigation into dense collections of hard spherical particles just large enough to be studied using a light microscope. These particles display colloidal properties, but also some similarities with granular materials. We improve the quantitative analysis of confocal micrographs of dense colloidal systems, which allows us to show that methods from simulations of granular materials are useful (but not sufficient) in analysing colloidal systems, in particular colloidal glasses and sediments. Collections of spheres are fascinating in their own right, but also make convincing models for real systems. Colloidal systems undergo an entropy-driven fluid-solid transition for hard spheres and a liquid-gas transition for suitable inter-particle attraction. Furthermore, experimental colloidal systems display a so far not well-understood glass transition at high densities, so that the equilibrium state is not achieved. This may be due to limited experimental timescales, but experiments under reduced gravity (both using the Space Shuttle and densitymatching solvents) suggest that it is not. Most colloidal studies have used scattering (i.e. non-microscopical) techniques, which provide no local information. Microscopy (particularly confocal) allows individual particles and their motion to be followed. However, quantitative microscopy of densely-packed, solidlyfluorescent particles, such as colloidal glasses, is challenging. We report, to our knowledge for the first time, a quantitative measure of confidence in individual particle locations and use this measure in an iterative best-fit procedure. This method was crucial for the investigation of the colloidal samples reported in this thesis. One of the disadvantages of microscopy is that it requires particles too large to be truly colloidal; gravity is no longer negligible. The particles used here rapidly sediment to form solid ”plugs”, which are supposedly ”random close packed” (RCP). At least in some cases, this is not the case, since some particles remain free to move. This observation, as well as some literature results, suggest that gravity has some influence on the structure of the sediment. In this document we consider some ideas from literature not normally considered in colloidal studies. Firstly, we discuss the RCP state, and the preferred Maximally Random Jammed state. Secondly, we borrow a technique designed to identify structures known as bridges in simulations of granular materials. Finding bridges, i.e. structures stable against gravity, in colloidal samples is the primary aim of this thesis. Gravity is important in colloidal sphere packings both in sediments and in glasses; its effect is not known but the best available candidate is bridging. The basic results of this analysis, the bridge size distributions, are close to those for granular systems, but differ little for samples of different volume fractions. We identify important stages of the analysis which require more investigation. Whilst questioning the usefulness of the bridge properties, we identify some related packing properties which show interesting trends. No theoretical predictions exist for these quantities. We investigated initially a non-density-matched system, but compare our results with a nearly density-matched system. The results from both systems are similar, despite the particles apparently acquiring a charge in the latter case. This thesis shows that reliable confocal microscopy of very dense systems of solidly-fluorescent particles is possible, and provides a range of unreported properties of dense sedimenting and sedimented nearly-Brownian sphere packings. It provides several suggestions for further analysis of these experimental systems, as well as some to be performed by those who simulate granular matter.

<p>The microphase segregation behavior, which exhibits periodic patterns on a mesoscale, has been found in many systems where it has demonstrated its extreme industrial usefulness in the diblock copolymer system. When studying more general isotropic colloidal systems, periodic microphases should ubiquitously emerge in systems for which short-range inter-particle attraction is frustrated by long-range repulsion~(SALR). The morphological richness of these phases makes them desirable material targets, but our relatively coarse understanding of even simple models hinders controlling their assembly both from thermodynamic and dynamic points of view. The thermodynamic question is what should be the appropriate potential to stabilize microphases, such as cluster crystal, cylindrical, double gyroid and lamellar, while the dynamic question is whether the current experiments are long enough for these phases to appear. This dissertation will focus on solving these two parts of problems and hopefully guide the experiments to discover a simple material that can have microphase segregation behavior. In order to answer the thermodynamic problem of the stability of the microphases, we use a novel thermodynamic integration method as well as density functional methods in comparing the free energy of the microphases with uniform liquids. With the thermodynamic integration, we locate FCC-cluster, cylindrical, double gyroid and lamellar phases as well as nontrivial interplay between cluster, gel and microphase formation for a model microphase former. We also extended the methods to the model with a shorter and longer repulsion region where we found that the shorter region of the system may be in the Wigner glass of clusters of different sizes rather than the microphases. We also compare our simulation results with that from the density functional theory where we demonstrate that the classical density functional theory is qualitatively right but the simple improvement of the radial distribution functional by assuming the system is the same as Percus-Yevick hard sphere does not make a quantitatively difference. Our finding confirms that if the colloidal system has proper SALR potential as well as the right regime of area fraction and temperature, the microphase will be found in these systems. We then answer the second question which is whether the slow dynamics hinders the formation of microphases. We study the modeled microphase former and track the change of the first peak in the structure factor as well as the structural correlation time. We found that the system has a very complex dynamical regimes, including homogeneous fluid, void micelle, liquid gel and solid gel. The system becomes extreme slow in the solid gel regime but if in the regime that density and temperature are near the order-disorder transition, the lamellar self-assembly is much faster than the relaxation time of the solid gel which may explain why in the experimental system, the colloids seem stuck forever. We have collaborated with an experimental group to realize the SALR self-assemble behavior in a well controlled system. We have calibrated the system using a high precision thermodynamic integration by determining and matching the critical point and triple point of the experiments when the system is set up in the purely attractive regime. The system, however, becomes unpredictable when it goes into the SALR system where both higher body and other interactions become dominant. Finally, we try to extend our system to a spherocylinder model, which is an anisotropic particles with SALR. We have developed a novel cell list method here to accelerate the simulation. By determining the percolation transition and the order parameter, we find that the simple anisotropic interaction will introduce a much complex phase behavior of the system even in the disordered regime. We have identified several disordered phases, including homogeneous liquid, micellar liquid, free rotator gel, nematic gel and smectic gel.</p> / Dissertation

Lanthanide-based nanoparticles can be used in a variety of applications, including biomedical work such as imaging and cancer therapies, and in solar cells. This thesis presents two different potential applications for lanthanide-based nanoparticles and a possible new method for single nanoparticle analysis. Each of the projects presented in this thesis starts from the colloidal synthesis of the nanoparticles and then explores their varying properties, such as size and size distribution, crystallinity, elemental composition, and optical properties. Chapter 1 presents a short introduction to lanthanides and explores their ability to luminesce and upconvert. These optical properties make lanthanide-based nanoparticles attractive in both the visible and near-infrared (NIR) range. Chapter 2 explores the possibility of using β-LaF3:Nd3+ (5%) nanoparticles in a colloidal laser to overcome some issues that solid state lasers face due to thermal effects. A colloidal laser requires small nanoparticles that can emit a useful wavelength and that are dispersed in a high boiling point liquid. In Chapter 3, a cation exchange of ytterbium for yttrium and erbium in water-dispersible β-NaYF4:Er3+ nanoparticles across a polyvinylpyrrolidone (PVP) surface coating was tested as a possible synthesis route for radioactive nanoparticles. Incorporating radioactive materials at the end of a therapy preparation would limit the number of synthesis steps in an isotope laboratory. Chapter 4 presents single-particle analysis of β-NaYF4:Er3+ (50%) nanoparticles using X-ray absorption spectroscopy (XAS) at the Canadian Light Source (CLS). Electron beams in scanning electron transmission microscopes (STEM) can damage the samples, making quantification of nanoparticles challenging. Finally, Chapter 5 discusses some conclusions and suggests possible future work. / Graduate / 0494

Permanent magnets are used heavily for multiple applications in industry and current electronic technologies. However, the current permanent landscape is muddled by high cost of materials and insufficient magnetic or thermal properties. The primary focus of this dissertation work is the synthesis and optimization of a new permanent magnetic material, in the form of cobalt carbide nanomaterials. The optimization revolved around controlling the crystal phase and particle shape of synthesized cobalt carbide particles; these parameters have significant impact on the observed magnetic properties of magnetic nanoparticles. Co3C was identified to be the preferred crystal phase, leading to better magnetic properties. Cobalt Fumarate was found to be the ideal precursor to synthesize anisotropic Co3C particles and enhance magnetic properties of the synthesized cobalt carbide particles. Lastly, an ethanol based reduction system was employed to develop the greener synthesis of Co and Ni magnetic particles.

Nous avons considéré autant les aspects thermodynamiques que cinétiques de la complexation d'ions métalliques (Cu2+ et Ni2+) par la 5-phénylazo-8-hydroxyquinoline (5Ph8HQ) et le cyclame greffés sur des nanoparticules de silice en dispersion colloïdale. Les silices pyrogénées, caractérisées par des surfaces spécifiques respectives d'environ 200 et 390 m2/g, ont été sélectionnées avec l'objectif d'obtenir des suspensions colloïdales stables. Nous avons démontré l'aptitude des colloïdes obtenus à extraire des cations divalents à l'état de traces (de l'ordre du micromolaire). Nous avons eu recours à l'ultrafiltration pour séparer la phase silicique dispersée de la phase aqueuse. Nous avons également montré l'intérêt de remplacer une pseudophase micellaire solubilisant l'extractant par nos phases solides. Nous avons décrit les cinétiques de complexation en utilisant la technique de la spectrophotométrie à écoulement bloqué pour les réactions les plus rapides. La dépendance de la constante de vitesse observée vis-à-vis de la concentration en cation métallique, du contre-ion considéré (acétate ou chlorure), de la force ionique et du pH a été évaluée. Pour décrire la cinétique de réaction du Ni2+ avec la 5Ph8HQ greffé, il nous a fallu prendre en compte les propriétés spectrophotométriques du complexe sur nanoparticules de silice. C'est un comportement original de la 5Ph8HQ sur silice puisque les densités optiques de solutions contenant la 5Ph8HQ en milieu micellaire ou le cyclame greffé sur silice suivent la loi de Beer-Lambert. L'étude du cyclame greffé qu'il s'agisse des cinétiques ou à l'équilibre est compliquée en raison du relargage de ce dernier en solution. / We considered both the thermodynamic and kinetic aspects of metal ions (Cu2+ and Ni2+) complexation by 5-phenylazo-8-hydroxyquinoline (5Ph8HQ) and cyclam grafted onto silica nanoparticles in colloidal dispersion. Fumed silicas with specific areas of respectively 200 and 390 m2/g were selected to get stable colloidal suspensions. We demonstrated the ability of these colloids to extract trace elements (at micromolar level). We used the ultrafiltration process to separate the dispersed silica phase from the aqueous phase. We also showed interest of our solid dispersed phases instead of a pseudo micellar one. We described complexation kinetics by stopped flow technique for the fastest reactions. The influence of metal cation concentration, counter-ion nature (acetate or chloride), ionic strength and pH on observed rate constant has been investigated. To describe the Ni2+ kinetics with grafted 5Ph8HQ, we took into account the spectrophotometric properties of the complex on silica nanoparticles. This is an original behaviour of 5Ph8HQ on silica since the optical densities of solutions containing 5Ph8HQ solubilised in micelles or cyclam grafted onto silica follow the Beer-Lambert's law. The study of grafted cyclam whether the kinetics or equilibrium is complicated due to the release of the latter in solution.

Arthur Ashkin's Nobel Prize-winning single-beam gradient force optical tweezers have revolutionized research in many fields of science. The invention has enabled various atomic and single molecular studies, proving to be an essential tool for observing and understanding nature at the nanoscale. This thesis showcases the uniqueness of single-beam gradient force traps and the advances necessary to overcome the limitations inherent in conventional techniques of optical trapping. With decreasing particle sizes, the power required for a stable trap increases and could potentially damage a particle. This is a significant limitation for studying biomolecules using conventional optical traps. Plasmonic nanoaperture optical trapping using double-nanohole apertures is introduced as a solution to overcoming these limitations. Achievements in double-nanohole optical trapping made possible by the pioneering work of Gordon et. al are highlighted as well. This thesis focuses on the advances in nanoaperture fabrication methods and improvements to experimental techniques adopted in single molecular optical trapping studies. The technique of colloidal lithography is discussed as a cost-effective high-throughput alternative method for nanofabrication. The limitation in using this technique for producing double-nanohole apertures with feature sizes essential for optical trapping is analyzed. Improvements to enable tuning of aperture diameter and cusp separation is one of the main achievements of the work detailed in this thesis. Furthermore, the thesis explains the modified fabrication process tailor-made for designing double-nanohole apertures optimized for optical trapping. Transmission characterization of various apertures fabricated using colloidal lithography is carried out experimentally and estimated by computational electrodynamics simulations using the finite-difference time-domain (FDTD) method. Optical trapping with double-nanohole apertures fabricated using colloidal lithography is demonstrated with distinct results revealing trapping of a single polystyrene molecule, a rubisco enzyme and a bovine serum albumin (BSA) protein. / Graduate

Neste trabalho, utilizou-se a técnica de decaimento de fluorescência resolvida no tempo para estudar a dinâmica agregação intra-polimérica do [3,22]-ioneno e da interação destes agregados com co-íons e contra-íons. Brometo de [3,22]-ioneno apresenta supressão intra-polimérica da sonda fluorescente pireno, eliminada pela quaternização dos grupos amino terminais com cloreto de benzila e pela troca do contra-íon Br- por Cl-, obtendo-se o cloreto de NT-benzil-[3,22]-ioneno, viabilizando a realização de medidas fotofísicas. Medidas da dinâmica de formação de excímeros de pireno e seus derivados evidenciaram que, em contraste às micelas de cloreto de hexadeciltrimetilamônio, os agregados formados por NT-benzil-[3,22]-ioneno participam de um eficiente processo intra-polimérico de fusão/fissão que facilita a migração de sondas e supressores durante o tempo de vida da sonda excitada. A existência deste processo de migração intra-polimérica requer a presença de vários microdomínios ao longo da cadeia do ioneno. Medidas em temperaturas baixas (&#60;15°C), onde o processo de fusão/fissão intrapolimérica torna-se mais lento que a supressão, forneceram uma estimativa do número de agregação dos microdomínios de 20,5. A constante de velocidade do processo de fusão/fissão (kfus) foi estimada a partir do estudo da dinâmica da formação de excímeros de pireno e derivados. Os dados para a dinâmica de saída de co-íons e de contra-íons supressores dos microdomínios de NTbenzil-[3,22]-ioneno foram tratados, levando em conta os dois mecanismos de migração, ou seja, pela fase aquosa e facilitada pelo processo de fusão/fissão. As constantes de velocidade de saída e de supressão para os microdomínios de NT-benzil-[3,22]-ioneno e micelas de CTAC1 apresentam dependências similares com o aumento da concentração de sal comum adicionado. / In this dissertation, the technique of time-resolved fluorescence quenching has been employed to investigate the dynamics of intrapolymeric aggregation of the [3,22]-ionene and the interaction of the resultant aggregates with coions and counterions. Undesirable quenching of the fluorescence of pyrene solubilized in [3,22]-ionene bromide was eliminated by quaternization of the amino terminal groups with benzyl chloride and by exchanging the counterion from Br- to Cl-, to give NT-benzyl-[3,22]-ionene chloride. Measurements of the dynamics of excimer formation by pyrene and its derivatives showed that, in contrast to cetyltrimethyanonium chloride (CTACl) micelles, the NT-benzyl-[3,22]-ionene aggregates undergoe an efficient intrapolymeric fusion/fission process that promotes the migration of probes and quencher between the aggregates. The existence of this intrapolymeric process requires that there be various microdomains distributed along the main ionene chain. At low temperature (&#60;15°C), where the intrapolymeric fusion/fission process becomes much slower than quenching, an estimate of 20.5 ionene subunits is obtained for the aggregation number of the microdomains. The rate constant for the fusion/fission process (kfus) was estimated from the dynamics of excimer formation of pyrene and its derivatives. Data for the dynamics of exit of coions and counterions from the microdomains of NT-benzyl-[3,22]-ionene were analyzed by taking into account two simultaneous migration mechanisms: via the aqueous phase and via the fusion/fission route. The added common salt concentration dependences of the rate constants for exit and quenching are similar for both the NTbenzyl-[3,22]-ionene microdomains and CTACl micelles.

by Wong Chun Wing = 銀膠媒介內結晶紫的表面增強共振拉曼散射研究 / 黃振榮. / Thesis submitted in: December 2004. / Thesis (M.Phil.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (leaves 74-79). / Text in English; abstracts in English and Chinese. / by Wong Chun Wing = Yin jiao mei jie nei jie jing zi de biao mian zeng qiang gong zhen la man san she yan jiu / Huang Zhenrong. / Abstract --- p.1 / Chapter Chapter 1 --- Introduction --- p.2 / Chapter Chapter 2 --- Experimental Setup --- p.7 / Chapter 2.1 --- Raman probe --- p.7 / Chapter 2.2 --- Spectrophotometer for absorption spectra --- p.7 / Chapter 2.3 --- TEM and AFM --- p.8 / Chapter Chapter 3 --- Sample Preparation --- p.9 / Chapter 3.1 --- Chemicals --- p.9 / Chapter 3.2 --- Silver Colloid --- p.9 / Chapter 3.3 --- Slide Coated with Silver Colloid --- p.10 / Chapter 3.4 --- Sampling Probe --- p.10 / Chapter Chapter 4 --- Results and Discussion --- p.12 / Chapter 4.1 --- Dependence of SERRS on CV Concentration --- p.12 / Chapter 4.1.1 --- Resonant Raman spectra of CV --- p.12 / Chapter 4.1.2 --- TEM Images of Ag Colloid --- p.17 / Chapter 4.1.3 --- SERRS at different CV Concentrations in Solution --- p.20 / Chapter 4.2 --- Dependence of CV SERRS on Ag Concentration --- p.36 / Chapter 4.3 --- Dependence of CV SERRS on NaCl Concentration --- p.42 / Chapter 4.3.1 --- UV-VIR Absorption Spectra of NaCl added Ag Colloid --- p.42 / Chapter 4.3.2 --- Dependence on NaCl Concentration --- p.49 / Chapter Chapter 5 --- Conclusions --- p.64 / Appendix A / Chapter A.1(part A) --- Estimation of the Number Density of Colloidal Ag Particles --- p.66 / Chapter A.1(part B) --- Estimation of CV Concentration needed for Monolayer Coverage on Ag colloids --- p.67 / Chapter A.2 --- Assignments of Crystal Violet (CV) Vibrational Modes --- p.69 / Appendix B Estimation of the Probed Volume of the Microscope Objective --- p.70 / Appendix C Estimation of the Effective Molar Absorption Coefficient (α) of CV --- p.71 / References --- p.74

The objective of this research was the development of an efficient method for the preparation of silver-polymer nanocomposites containing finely dispersed silver nanoparticles. The surface of nanosilver was functionalized by thiolation with 2-aminoethanethiol. Amino-modified nanosilver was covalently bonded to polyacrylic acid, biodegradable polymers like acid terminated polylactic acid, ester terminated poly(DL-lactide-co-glycolide) and acid terminated poly(DL lactide-co-glycolide) in the presence of diisopropylcarbodiimide by carbodiimide method. Esterification of the carboxyl groups of Ag-polyacrylic acid by hydrochloric acid in methanol resulted in the formation of a stable colloidal dispersion of Ag nanoparticles in the polymer matrix. It was observed that not just acid terminated polymers but also ester terminated polymers could react with functionalized nanosilver. This unusual reaction was due to the aminolysis of the ester bond in the polymer chain by the surface amino groups. Silver-polymer nanocomposites obtained with acid terminated polylactic acid and poly(DL-lactide-co-glycolide) contained highly dispersed nanosilver in the polymer matrix in comparison with the ester terminated poly(DL-lactide-co-glycolide). Chemical and structural characteristics of the obtained materials were studied by instrumental methods. Attained biodegradable materials confirmed X-ray contrast and bactericidal properties, which could be eventually used for biomedical applications.

La fabrication de nano-cristaux métalliques suscite un effort de recherche en constante augmentation depuis plusieurs années. Cet immense intérêt est motivé par les propriétés uniques et fascinantes qui apparaissent à l’échelle des tailles nanométriques. En effet, le confinement des électrons au sein d’un nanocristal est un moyen puissant de moduler les propriétés électroniques, optiques et magnétiques d’un matériau. Les synthèses par voies chimiques sont des stratégies très rependues pour fabriquer des nanoparticules métalliques avec des morphologies originales en exploitant la versatilité des milieux réactionnels liquides pour contrôler les mécanismes de formation. Cependant, si la chimie employée lors de ces synthèses n’est pas très compliquée, la compréhension des processus de nucléation/croissance en milieu liquide complexe et l’influence de chaque espèce chimique est un tout autre challenge. Pour y répondre, nous avons utilisé la microscopie électronique en transmission en milieu liquide pour visualiser des phénomènes de croissance à l’échelle nanométrique. Cette récente technique de microscopie in situ nous a permis d’étudier en temps réel la dynamique de croissance de nanoparticules d’or et d’or-cuivre dans des milieux réactionnels de composition contrôlée. Le premier objectif de cette thèse était de distinguer les effets cinétiques (liés aux flux de matière) et les effets thermodynamiques (liés à l’équilibre des nanostructures en fonction de leur environnement) qui dictent tous les deux la forme finale des nanoparticules. De plus, des études systématiques nous ont permis de séparer les inévitables effets du faisceau d’électron, des effets de paramètres spécifiques de la synthèse, comme la forme des germes ou la fonctionnalisation organique, qui sont de toute première importance en chimie des colloïdes. Enfin, des phénomènes induits par le faisceau ont aussi été exploité pour comprendre l’influence de l’irradiation sur la chimie du milieu réactionnel, qui peut induire des réactions d’oxydo-réductions réversibles et contrôlables dans les nano-systèmes bimétalliques. / Recent years have seen a remarkable increase in research activities related to the synthesis of metallic nanocrystals. This intense interest is fueled by the unique and fascinating properties delivered at such size domains. Indeed, electrons confinement by nanocrystals is a powerful means to modulate electronic, optical and magnetic properties of a material. Most current strategies employ chemical synthesis to formulate unique nanoparticle morphologies by exploiting the versatility of liquid reaction media to control the formation mechanisms. Although the chemistry of metal nanocrystal synthesis is not complicated, understanding the nucleation and growth processes in complex liquid media and the influence of each chemical species is altogether a different challenge. It is in this regard, that we have utilized liquid cell transmission electron microscopy to visualize relevant growth phenomenon at the nanoscale. This recent in situ technique allowed us to study in real time the dynamics of growth of Au and Au-Cu nanoparticles in reaction media of controlled composition. The primary goal of this thesis was to distinguish the kinetics effects (related to the flow of matter) and the thermodynamics effects (related to the environment-dependent equilibrium of nanostructures) on final nanoparticle shapes. In addition to this, systematic studies were performed to separate the inevitable beam effects from the influence of specific synthesis parameters such as the seed crystal morphology and the organic functionalization that are of primary importance for colloidal chemists. Beam induced phenomena were also utilized to understand the solution chemistry of the exposed solvent which is in turn responsible for driving reversible redox reactions in bimetallic nano-systems.