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.

Nucleation is a key step in the crystallisation process, where a new crystalline solid phase is created from a supersaturated solution. The applications of crystallisation as a purification and separation technique span many industries, yet still no definitive molecular mechanism for nucleation exists. This PhD is part of a critical mass research project involving researchers from both the Universities of Manchester and Leeds. The aim is to reveal the relationship between structural components of the nucleation transition state, solution phase molecular self-assembly and nano cluster formation, through to critically sized crystalline nuclei which then grow to crystals. All work has been carried out on a small organic molecule, p-aminobenzoic acid (PABA). This PhD has delivered successful characterisation of PABA in the solid and solution state, along with a detailed understanding of its nucleation kinetics and growth rates from a range of solvents. PABA has two enantiotropically related polymorphs, α and β, with the former constructed of carboxylic acid dimers and the latter of a hydrogen bonded tetramer network linking alternate acid and amine functionalities. New determinations of the crystal structures of both forms were submitted to the CCDC with Ref codes of AMBNAC07 and 08 for α and β PABA respectively. A detailed morphological study on both forms of PABA employing modelling and experimental methods has revealed the effect of solvent on the growth habit. In all polar solvents, α PABA displays a more important or slower growing (002) face than the calculated morphology implies. In water, β PABA has a much smaller (101 ̅) face in comparison to β PABA grown from alcohols. Crystallisation experiments demonstrate a clear solvent effect on the appearance of the two polymorphs. From organic solvents only α PABA is obtained, from water both α and β PABA are crystallised. A database search (CCDC) suggests that water may play an important role in the stabilisation of the nucleation transition state for both α and β PABA. This is not possible in organic solvents. Detailed nucleation and crystal growth kinetics have been measured for α PABA at 20°C in water, acetonitrile, ethyl acetate and 2-propanol. A clear solvent trend was observed in both the derived rates of molecular attachment and crystal growth. These were fastest in water, followed by acetonitrile, then ethyl acetate and finally slowest, in 2-propanol. This can be explained by the solvation of the carboxylic acid functional group, where 2-propanol is deemed the most effective solvator of building units in solution and on a crystal surface. This conclusion is supported by the solution FTIR spectroscopy, which clearly confirms strong solvation.

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Variability of magmatic textures records a wide array of physicochemical and mechanical processes that have operated in a magma chamber during its crystallization. Here I investigate how the final textural record can quantitatively be used to decipher the magma crystallization history and internal dynamics of magma chambers. The thesis is based on a formulation of numerical models of texture formation under the activity of various crystallization processes. Numerical results are then compared to the new quantitative textural datasets derived from four distinct magmatic systems in the Bohemian Massif: (i) Fichtelgebirge-Smrčiny granite batholith; (ii) Krkonoše-Jizera plutonic complex; (iii) Kdyně mafic intrusion; (iv) České středohoří volcanic complex. Combination of the field textural studies with their interpretation via numerical crystallization models provides new implications regarding magmatic crystallization and internal dynamics of magma chamber. The most important results of this Ph.D. thesis are as follows: (i) a new method has been developed that allows the rates of nucleation and growth of crystals to be derived from quantitative textural data. The method requires using the crystallinity evolution in time as an independent constraint in order to provide unique solution. In case of the...

P-aminobenzoic acid (PABA) is a polymorphic compound with two known polymorphs - alpha with a needle morphology and β with a rhombic morphology. It is an enantiotropic compound with a transition temperature at 13.8oC, where alpha is more thermodynamically stable above transition temperature and β is more thermodynamically stable below. At the beginning of this project, crash-cooling crystallisation experiments were conducted to determine the effect of solvent, temperature and supersaturation on the nucleating polymorphs of PABA. Three solvents were tested (water, ethanol and isopropyl alcohol) over a range of supersaturations and temperatures. The results suggested that polymorph appearance of PABA was heavily influenced by kinetics, as opposed to thermodynamics of the system, disagreeing with Ostwald's rule of stages. The project then focussed on the ability of tailor-made additives to select the crystallising polymorph of PABA from supersaturated solutions of PABA in isopropyl alcohol. Crash-cooling crystallisation experiments were performed using two additives: 4-amino-3-nitrobenzoic acid, and 4-amino-3-methoxybenzoic acid. Results showed that alpha PABA crystallised below a critical concentration of either additive, and above that critical concentration, β PABA would crystallise. To determine whether the additives were affecting the nucleation and/or growth kinetics of alpha PABA and β PABA, a series of nucleation and growth experiments were conducted using a Crystal16 multiple stirred reactor and a crystal growth cell respectively. The results showed that both additives greatly reduced the attachment frequency of growth units to alpha PABA nuclei, and inhibited the growth rate of alpha PABA seed crystals. Nucleation data could not be obtained for β PABA, but in terms of crystal growth, both additives did not affect growth rate of β PABA to a noticeable degree. Gravimetric and HPLC experiments were also employed to measure the solubility effects of both additives on PABA in isopropyl alcohol. Results showed that both additives did not appear to affect PABA's solubility to a noticeable degree.

abstract: Zinc oxide (ZnO) has attracted much interest during last decades as a functional material. Furthermore, ZnO is a potential material for transparent conducting oxide material competing with indium tin oxide (ITO), graphene, and carbon nanotube film. It has been known as a conductive material when doped with elements such as indium, gallium and aluminum. The solubility of those dopant elements in ZnO is still debatable; but, it is necessary to find alternative conducting materials when their form is film or nanostructure for display devices. This is a consequence of the ever increasing price of indium. In addition, a new generation solar cell (nanostructured or hybrid photovoltaics) requires compatible materials which are capable of free standing on substrates without seed or buffer layers and have the ability introduce electrons or holes pathway without blocking towards electrodes. The nanostructures for solar cells using inorganic materials such as silicon (Si), titanium oxide (TiO2), and ZnO have been an interesting topic for research in solar cell community in order to overcome the limitation of efficiency for organic solar cells. This dissertation is a study of the rational solution-based synthesis of 1-dimentional ZnO nanomaterial and its solar cell applications. These results have implications in cost effective and uniform nanomanufacturing for the next generation solar cells application by controlling growth condition and by doping transition metal element in solution. / Dissertation/Thesis / Ph.D. Materials Science and Engineering 2012

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Colloidally-stable zero valent iron nanoparticles (nZVI) were synthesized through a classical redox reaction of iron sulfate with minor modifications using cellulose nanocrystals (CNCs) as stabilizers. We obtained spherical nZVI particles with high surface roughness and a mean size of 130nm. Particles remain colloidally stable after more than two months. Cellulose nanocrystals play a dual role in nZVI stability: a foreign surface to encourage stable nucleation over fast aggregation and a stabilizer to prevent iron nanoparticles aggregating into fractal colloids. Our results highlight the impact of the presence of CNCs on the rates and mechanisms of nucleation, growth, aggregation, and aging of nZVI particles, indicating promise in controlling size and morphology of similarly redox-generated nanoparticles. Cellulose nanocrystal-stabilized nZVI nanoparticles demonstrate properties well-suited for enhanced soil and groundwater remediation. //Nanocomposites composed of carboxylated cellulose nanocrystals and iron (Fe-oxCNC) were prepared through a classical redox reaction of iron sulfate using TEMPO-oxidized cellulose nanocrystals (oxCNCs) as a template and stabilizer. Morphological control over Fe-oxCNC nanoparticles was realized by varying the amount of oxCNC added to the redox process. As the molar ratio between oxCNC and Fe was increased from 1 to 8, the morphology of Fe-oxCNC nanoparticles evolved from rounded iron aggregates supported by cellulose nanocrystals to thin film iron-coatings on cellulose nanocrystals. Transmission electron microscopy (TEM), Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), and chemical analyses (EDX, EELS) revealed that oxCNCs were coated by iron. Small changes to the density and type of functional groups on the CNC surface have large impacts on the morphology and the oxidation state of adsorbed iron nanoparticles. / Thesis / Master of Applied Science (MASc)

Controlling the size and size distribution of colloidal nanoparticles have gained extraordinary attention as their physical and chemical properties are strongly affected by size. Ligands are widely used to control the size and size distribution of nanoparticles; however, their exact roles in controlling the nanoparticle size distribution and the way they affect the nucleation and growth kinetics are poorly understood. Therefore, understanding the nucleation and growth mechanisms and developing theoretical/modeling framework will pave the way towards controlled synthesis of colloidal nanoparticles with desired sizes and polydispersity. This dissertation focuses on identifying the possible roles of ligands and size on the kinetics of nanoparticle formation and growth using in-situ characterization tools such as small-angle X-ray scattering (SAXS) and kinetic modeling. The presented work further focuses on developing kinetic models to capture the main nucleation and growth reactions and examines how ligand-metal interactions could potentially alter the rate of nucleation and growth rates, and consequently the nanoparticle size distribution. Additionally, this work highlights the importance of using multi-observables including the concentration of nanoparticles, size and/or precursor consumption, and polydispersity to differentiate between different nucleation and growth models and extract accurate information on the rates of nanoparticle nucleation and growth. Specifically, during the formation and growth of colloidal nanoparticles, complex reactions are occurring and as such nucleation and growth can take place through various reaction pathways. Therefore, sensitivity analysis was applied to effectively compare different nucleation and growth models and identify the most important reactions and obtain a reduced model (e.g. a minimalistic model) required for efficient data analysis. In the following chapters, a more sophisticated modeling approach is presented (population balance model) capable of capturing the average-properties of nanoparticle size distribution. PBM allows us to predict the growth rate of nanoparticles of different sizes, the ligand surface coverage for each individual size, and the parameters involved in altering the size distribution. Additionally, thermodynamic calculations of nanoparticle growth and ligand-metal binding as a function of size and ligand surface coverage were conducted to further shed light on the kinetics of nanoparticle formation and growth. The combination of kinetic modeling, in-situ SAXS and thermodynamic calculations can significantly advance the understanding of nucleation and growth mechanisms and guide toward controlling size and polydispersity. / Doctor of Philosophy / The synthesis of colloidal metal nanoparticles with superior control over size and size distribution, and has attracted much attention given the wide applications of these nanomaterials in the fields of catalysis, photonics, and electronics. Obtaining nanoparticles with desired sizes and polydispersity is vital for enhancing the consistency and performance for specific applications (e.g., catalytic converters for automotive emission). Ligands are often employed to prevent agglomeration and also control the nanoparticle size and size distribution. Ligands can affect the precursor reactivity and therefore the reduction/nucleation by binding with the metal precursor. Nucleation refers to the assimilation of few atoms to form initial nuclei acting as templates for nanoparticle growth. Additionally, ligands can bind with the nanoparticle surface sites and change the rate of surface growth and therefore the final nanoparticle size. Despite strong effects of ligands in the colloidal nanoparticle synthesis, their exact role in the nucleation and growth kinetics is yet to be identified. Additionally, nucleation and growth models capable of unraveling the underlying mechanisms of nucleation and growth in the presence of ligands are still lacking in the literature. Therefore, obtaining nanoparticles with desired sizes and polydispersity mostly relies on trial-and-error approach making the synthesis costly and inefficient. As such, developing models capable of predicting suitable synthesis conditions is contingent upon understanding the chemistry and mechanism involved during nanoparticles formation. Therefore, in this study, novel kinetic models were developed to capture the nucleation and growth kinetics of colloidal metal nanoparticles under different synthetic conditions (different types of solvents, different concentrations of ligand and metal). In-situ SAXS was further employed to measure the average diameter, concentration of nanoparticles, and polydispersity during the synthesis and extract the nucleation and growth rates (evolution of concentration of nanoparticles and size). First, an average-property model was developed to account for ligand-metal bindings and capture the size and concentration of nanoparticles during the synthesis. Then, a more complex modeling approach; PBM, accompanied by the thermodynamic calculations of surface growth and ligand-nanoparticle binding enthalpies was implemented to capture the size distribution. As it will be shown later, the determination of the underlying mechanisms resulted in a highly predictive kinetic model capable of predicting the synthetic conditions to obtain nanoparticles with desired sizes. The proposed methodology can serve as a powerful tool to synthesize nanoparticles with specific sizes and polydispersity.