Rozprawy doktorskie: „Nanoparticle formation”

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Maguire, Steven. "Magnetic field control of silver nanoparticle formation". Thesis, University of Ottawa (Canada), 2006. http://hdl.handle.net/10393/27390.

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Silver nanoparticles can be readily generated in micellar environments by ketyl radicals formed from the photoreduction of benzophenone in the presence of a suitable hydrogen donor. The yield of these ketyl radicals can be increased by extending the lifetime of the triplet radical pair through Zeeman splitting of the triplet sublevels in an externally applied magnetic field. This provides control over the rate of photogeneration of nanoparticles under very mild conditions. The rate of photogeneration can be monitored by the distinctive surface plasmon resonance absorption around 420 nm. In this work, micelles of sodium dodecyl sulphate (SDS) were employed, and 1,4-cyclohexadiene (1,4-CHD), an excellent hydrogen donor, was used to promote the generation of ketyl radicals. When benzophenone and a silver salt are added to this system and it is irradiated in the presence of a magnetic field, the rate of appearance of the plasmon band is enhanced. In addition to serving as a hydrogen donor, 1,4-CHD also has a stabilising influence on the nanoparticles, adsorbing onto the surface and preventing aggregation. 1,4-CHD added to a solution of nanoparticles synthesised without the diene present will even break up existing aggregates.

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Martin, Christopher Paul. "Pattern formation in self-organised nanoparticle assemblies". Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/10772/.

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An extremely wide variety of self-organised nanostructured patterns can be produced by spin-casting solutions of colloidal nanoparticles onto solid substrates. This is an experimental regime that is extremely far from thermodynamic equilibrium, due to the rapidity with which the solvent evaporates. It is the dynamics of ﬂow and evaporation that lead to the formation of the complex structures that are observed by atomic force microscopy (AFM). The mechanisms involved in the formation of these patterns are not yet fully understood, largely because it is somewhat challenging to directly observe the evaporation dynamics during spin-casting. Monte Carlo simulations based on a modiﬁed version of the model of Rabani et al. [1] have allowed the study of the processes that lead to the production of particular nanoparticle morphologies. Morphological image analysis (MIA) techniques are applied to compare simulated and experimental structures, revealing a high degree of correspondence. Furthermore, these tools provide an insight into the level of order in these systems, and improve understanding of how a pattern’s speciﬁc morphology arises from its formation mechanisms. Modifying the properties of a substrate on the scale of a few hundred nanometres by AFM lithography has a profound eﬀect on the processes of nanoparticle pattern formation. The simulation model of Rabani et al. was successfully modiﬁed to account for the eﬀect of surface modiﬁcation. The simulations were further modiﬁed to reproduce cellular structures on two distinct length scales– a phenomenon that is commonly seen in experiments. The dynamic behaviour of simulated nanoparticle structures is examined in the “scaling” regime in relation to recent experiments carried out by Blunt et al. [2] in an attempt to understand the coarsening mechanism. Finally, a genetic algorithm approach is applied to evolve the simulations to a target morphology. In this way, an experimental target image can be automatically analysed with MIA techniques and compared with an evolving population of simulations until a target “ﬁtness” is reached.

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Wang, Haolan. "Nanoparticle formation through the liquid arc method". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613366.

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Haubold, Danny, Annett Reichhelm, Alexander Weiz, Lars Borchardt, Christoph Ziegler, Lydia Bahrig, Stefan Kaskel, Michael Ruck i Alexander Eychmüller. "The Formation and Morphology of Nanoparticle Supracrystals". Saechsische Landesbibliothek- Staats- und Universitaetsbibliothek Dresden, 2016. http://nbn-resolving.de/urn:nbn:de:bsz:14-qucosa-209752.

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Supracrystals are highly symmetrical ordered superstructures built up from nanoparticles via self-assembly. While the NP assembly has been intensively investigated, the formation mechanism is still not understood. To shed some light onto the formation mechanism, we are using one of the most common supracrystal morphologies, the trigonal structures, as a model system to investigate the formation process in solution. To explain the formation of the trigonal structures and determining the size of the supracrystal seeds formed in solution, we introduce the concept of substrate-affected growth. Furthermore, we show the influence of the NP concentration on the seed size and extend our investigations from Ag towards Au. 1.

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Vanella, Andrea. "Nanoparticle formation in nanoporous structures and applications". Doctoral thesis, Università di Siena, 2022. http://hdl.handle.net/11365/1210313.

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In the recent years the scientific community demonstrates an increasing interest in the study of nanoparticles and their properties, such as interaction with a surface and the adsorption/desorption characteristic. The latte properties, as well the formation and growth of nanoparticles, can be controlled by a proper light source. On the other hand having a much larger specific surface to increase the adsorbed amount of atoms, is a desirable characteristic of the system. That is on of the reason of the large exploitation of nanoporous material in many different research fields. Porous glass presents a wide variety of benefits: thermal and chemical stability, low production cost, easiness of handling and large value of specific surface area, which can be of the order tens square meters per grams. This thesis work falls into the context described above, in particular it aims to investigate the adsorption/desorption process of alkali atoms onto different randomly oriented pores structures, as well the formation of aggregates in the pores of the adsorbed atoms by using different external light sources. The control of the desorption process as well as the formation and the desorption of nanoparticles make use of two light induced process: Light Induced Atomic Desorption or LIAD and the Surface Plasmon Induced Desorption. The main difference between these two effects, beside the physics behind the two effects is intrinsically different, is that for the latter is required a resonant light source resonant with the plasmonic oscillation while for the LIAD it is not needed any resonant wavelength. The main and newer part of the work is done in a chamber were is present an Ultra High Vacuum regime. Most of the studies on this topic were performed in vapor filled cells. The use of an Ultra High Vacuum regime for this work is done to overcome some drawback of the vapor cells, such as the impossibility to change atomic species once that a cell is built or the difficult controlling of the atomic density. Indeed in this apparatus the loading process is done with an externally removable dispenser controlled by a current flowing into it. Hence the loading process is no more continuous an can be switched off by switching off the flowing current. Once the UHV regime is reached, the first step is the loading of the porous sample. Then the adsorption properties at different wavelengths are studied as well as that eventual desorption of the atomic specimen. The formation of nanoparticles in the porous structures are induced by an external light source under different condition of intensity and illumination time. Similar studies are also performed in alkali vapor filled cells, in order to compare the results. There were performed simultaneously measurements by on the optical signal and electric signal by means of a channeltron. The measurements performed in this work showed that by using porous glass, with different average pores size and under an appropriate illumination, it is possible to exploit the LIAD effect to enhance the aggregation of Rb nanoparticles in UHV regime. The most satisfying sample revealed to be a film of nanoporous alumina of 300 nm thickness.

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Voloshko, Andrey. "Nanoparticle formation by means of spark discharge at atmospheric pressure". Thesis, Saint-Etienne, 2015. http://www.theses.fr/2015STET4011/document.

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Au cours de la dernière décennie, les nanoparticules métalliques ont trouvé de nombreuses applications dans divers domaines tels que l'optique, la photonique, la catalyse, la fabrication de matériaux, les énergies renouvelables, l'électronique, la médecine et même les cosmétiques. Les nouveaux développements de ces applications nécessitent des méthodes de synthèse de nanoparticules fiables donnant une grande quantité de nanoparticules aux propriétés spécifiques. Les méthodes à base de plasma, tels que des décharges d'étincelles et d’arcs sont parmi les plus prometteuses car elles permettent une augmentation considérable de la vitesse de production et une diminution des coûts. Le contrôle de ces processus est cependant toujours difficile et nécessite de nombreuses études détaillées, à la fois expérimentales et théoriques. Dans cette thèse, les décharges d'étincelles sont étudiées numériquement. L'objectif principal est de mieux comprendre les principaux mécanismes impliqués dans la décharge d'étincelle avec un faible écartement d’électrodes et sous pression atmosphérique. Ensuite, sur la base de la modélisation détaillée proposée, la quantité de nanoparticules produites ainsi que leur distribution en taille est prédite et est comparée avec les résultats expérimentaux correspondants. Dans le modèle proposé, seules les conditions initiales, la géométrie du système et les propriétés du matériau sont utilisés comme paramètres d'entrée. Une décharge d’étincelle unique est divisée en plusieurs unités selon les échelles spatiales et temporelles des processus physiques comme suit: modèles de (i) flux plasma, (ii) décharge, (iii) hydrodynamique, (iv) couche cathodique, (v) érosion d’électrode et (vi) formation de nanoparticules. Les résultats du modèle combiné sont ensuite comparés à la fois avec d'autres résultats théoriques et à des résultats expérimentaux. Enfin, les possibilités d'optimisation de la production de nanoparticules par décharge d'étincelles sont proposées sur la base de la variation des paramètres expérimentaux et sur l'analyse de la quantité de particules produites et de leur taille moyenne
During last decade, metal nanoparticles have found many applications in various areas, such as optics, photonics, catalysis, material manufacturing, renewable energy, electronics, medicine and even cosmetics. Further development of these applications requires reliable nanoparticle synthesis methods providing a large amount of nanoparticle with required properties. Plasma-based methods, such as spark and arc discharges are among the most promising since they allow a considerable increase in the production rate and a decrease in costs. The control over these processes is, however, still challenging and requires many detailed studies, both experimental and theoretical. In this thesis, spark discharge is investigated numerically. The main objective is to better understand main mechanisms involved in spark discharge with a short gap under atmospheric pressure. Then, based on the proposed detailed modeling, the amount of the produced nanoparticles, their size distribution should be predicted and compared with the corresponding experimental results. In the proposed model, only initial conditions, geometry of the system and material properties are used as input parameters. A single spark event is divided into several units according to localization and time scales of physical processes as follows: (i) streamer model, (ii) discharging model, (iii) hydrodynamic model, (iv) cathode layer model, (v) electrode erosion model and (vi) nanoparticle formation model. The results of the combined model are then compared both with other theoretical and experimental results. Finally, possibilities of optimization the nanoparticle production by spark discharge are proposed based on the variation of the experimental parameters and on the analysis of the resulted particle yield and mean size

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Huo, Zhijie. "Modelling of Soot Nanoparticle Formation in Turbulent Flames". Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/24858.

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Soot emission from hydrocarbon fuel combustion is a major source of particulate pollution. The increasingly stringent regulations on emissions have necessitated the developments of soot models to aid designs of combustion devices with cleaner performance. Such models will also make valuable contributions in designing and optimising processes that produce beneficial carbonaceous particulates, e.g. carbon black plants and processes requiring enhanced soot-induced radiation. The present work aims to develop a detailed soot model and implements the model in the sparse multiple mapping conditioning (MMC) - large eddy simulation (LES) framework to form a predictive tool for soot evolution in turbulent flames. The thesis consists of two major parts presenting soot evolution without and with turbulence, respectively. In the first part, the fundamental physics of soot evolution processes is presented, followed by a review of soot formation modelling that focuses on the sectional methods. The current work uses a sectional soot kinetics scheme that approximates solutions to the population balanced equations by lumped species and replaces individual growth/oxidation models by a sequence of equivalent physicochemical reactions with Arrhenius-like rate expression. The soot kinetics is a reduced version derived from a multisectional soot mechanism (Sirignano et al., Energy & Fuels 27, 2013). In this work, a novel generalised model describing the interaction potential well depth between soot particles of any size and composition is proposed for a thermal rebound based coagulation model to account for the probability of combining electrically neutral entities, i.e. nucleation, condensation and coagulation. The coagulation model is then simplified into Arrhenius expression so that the gas and soot kinetics can be integrated into a fully coupled system. The model is tested by comparisons to the experimental data of a series of ethylene burner stabilised stagnation (BSS) premixed flames and a methane laminar coflow diffusion flame, and the sensitivity to model parameters is investigated. Overall, the simulation results show good agreement with the experimental measurement, but strong sensitivity to the parameter λ that accounts for void fractions of soot particles is observed. In the second part, the turbulence and combustion models are reviewed. The focus is placed on the LES and MMC methods and the closure strategies in the methods. As the source terms of a lumped species reflecting different evolution processes are represented by a chemical source term in the sectional soot kinetics model, the filtered transport equation of lumped species can be straightforwardly closed by a joint filtered density function (FDF) of gas-phase species and lumped species. This work employs the sparse generalised MMC-LES, a stochastic FDF type method but uses much fewer notional particles (usually fewer than the number of LES cells) than the traditional FDF method. Combined with the code developments with some emphasis on computational load balancing models, the coupled turbulence-chemistry-soot model is shown to provide detailed soot evolution solutions, such as particle size distribution (PSD), with reasonable computational costs. The model is examined by comparison to the experimental data of the Delft Adelaide flame. Although discrepancies exist, the numerical predictions on soot volume fraction and intermittency are in reasonable accuracy. Detailed investigations on the probability density functions of the soot volume fraction show that the model captures the key features of soot formation but predicts significantly more soot in the range between 0.1 ppb and 6.4 ppb than the experimental measurements. Lastly, the predicted soot PSDs are presented. The results suggest that the PSDs in the turbulent flame simulation are in mixed unimodal and bimodal distributions.

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Tobler, Dominique Jeanette. "Molecular pathways of silica nanoparticle formation and biosilicification". Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/359/.

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Biosilicification and silica nanoparticle formation occur in many modem terrestrial environments and they also played an important role in ancient geological settings. This thesis presents results from (i) field studies in Icelandic geothermal waters that aimed at quantifying the parameters that control the growth rate and texture of sinters and the diversity and silicification of associated microbial communities and (ii) lab studies that focussed on the kinetics and mechanisms of silica nanoparticle forination under conditions mimicking natural geothermal environments. The analysis of growth rates and textures of sinters from five geochemically very different Icelandic geothermal areas showed that the inorganic silica precipitation rate was strongly influenced by temperature, pH, ionic strength, and silica concentration. In addition, the presence of thick biofilms seemed to have aided the precipitation process by simply providing "sticky" surfaces. In turn, the structural and textural development of sinters was affected by the precipitation rate and mechanism (subaqueously and/or subaerially) as well as the presence and absence of microbial communities. As a result, porous, subaequeouss inters developed at sites with medium to high sinter growth rates and low microbial activity. Conversely, dense, heterogeneouss inters formed in geothermal waters characterized by low precipitation rates and extensive biofilms. With time these biofilms became fully silicified and well preserved within the sinter edifices. The diversity of microbial communities in hot spring environments appeared to be directly controlled by the physico-chernical conditions of the geothermal waters (i. e., T,pH, salinity and sinter growth rate) and the most dominant phylotypes were related to Aquificae, Deinococci and y-Proteobacteria. The rates and mechanisms of the initial steps of silica polymerisation and silica nanoparticle formation were quantified in-situ and time-resolved using synchrotron-based small angle x-ray scattering (SAXS). The experiments were carried out in near neutral pH solutions with initial Si02 between 640 - 1600 ppm, ionic strength of 0.02 - 0.22 M, and added organics (glucose, glutarnic acid, xanthan gum). The polymerization reactions were induced either by neutralising a high pH solution or by rapid cooling of a supersaturatedh ot silica solution. From the analysis of the time-resolved SAXS data, a kinetic model for the nucleation and growth of silica nanoparticles was derived suggesting a 3-stage process: (1) homogeneous nucleation of critical nuclei (I -2 run; depending on the concentration regimes), (2) 3-dimensional, surface-controlled particle growth following 1st order reaction kinetics and (3) Ostwald ripening and particle aggregation. At the end of this 3-stage process, regardless of the tested silica concentration, ionic strength or added organics, the final particle diameter was about 8nm characterised by open, polymeric (i. e., mass fractal) structures. The kinetics of particle growth were unaffected by the two different methods to induce silica polymerisation (pH-drop vs. T-drop) however, the growth processes proceeded substantially slower if silica polymerisation was induced by fast cooling as opposed to pH-drop. In contrast, the addition of organics did not affect the reaction rates. The nucleation and growth of silica nanoparticles under constant re-supply Of fresh silica solution (i. e., hot springs) was simulated using a flow-through geothermal simulator system. The effect of silica concentration ([Si02D, ionic strength (IS), temperature and organic additives on the size and polydispersity of silica nanoparticles was quantified. VVhile the applied increase in IS did not affect the size (30 - 35 nm) and polydispersity (± 9 nm) observed at 58 C, an increase in [Si02] notably enhanced silica polymerisation and also resulted in slightly smaller particle sizes. The biggest effect was observed with a decrease in temperature (58 to 33 C) or the addition of glucose: in both cases particle growth was restricted to sizes below 20 mn. Conversely, the addition of xanthan gum induced the development of a thin silica-rich film that enhanced silica aggregation.

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Lin, Jiashu. "La formation et le transport des particules dans le plasma froid". Thesis, Orléans, 2020. http://www.theses.fr/2020ORLE3029.

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Les plasma poudreux sont des plasmas qui contiennent des particules solides dont les tailles vont quelques nanomètres à quelques dizaines de micromètres. La présence de ces particules solides, dans les plasmas, a été découverte dans les procédés de l'industrie de microélectronique. Les particules dans le plasma étaint considérées comme la source principale de la contamination de ces procédés. Les premiers travaux de recherche était focalisées sur les méthodes et moyens de les éliminer et d'empêcher leur formation. Suite à l'identification des différentes phase de formation et la découverte de la structure cristalline des nanoparticules qui se forment dans la première phase des applications très prometteuses ont commencé à se développer dans différents domaines tels que le photovoltaïque, la nanoélectronique etc., Ceci a donné une nouvelle impulsion aux activités de recherches sur les propriétés du plasma poudreux ont attiré l'attention de plus en plus de chercheurs à travers le monde.Les plasmas poudreux sont des plasmas qui contiennent des particules solides dont les tailles vont de quelques nanomètres à quelques dizaines de micromètres. La présence de ces particules solides, dans les plasmas, a été découverte dans les procédés de l'industrie de microélectronique. Les particules dans le plasma étaient considérées comme la source principale de la contamination de ces procédés. Les premiers travaux de recherche étaient focalisées sur les méthodes et moyens deles éliminer et d’empêcher leur formation. Suite à l’identification des différentes phases de formation et la découverte de la structure cristalline des nanoparticules qui se forment dans la première phase des applications très prometteuses ont commencé à se développer dans différents domaines tels que le photovoltaïque la nanoélectronique etc…, Ceci a donné une nouvelle impulsion aux activités de recherches sur les propriétés du plasma poudreux et ont attiré l’attention de plus en plus de chercheurs à travers le monde.Les travaux de recherche, entrant dans le cadre de cette thèse, sur les plasmas poudreux, ont été focalisés essentiellement sur le contrôle de la formation des particules solides et leur transport dans le plasma. Par conséquent, cette thèse est composée par deux parties, la première concerne la formation des particules en phase gazeuse dans le plasma et la deuxième traitera du comportement et du transport du nuage dense de particules dans le plasma. Ces travaux ont été effectués au sein du laboratoire GRMI (Université d’Orléans, France) et du Département d’électronique du Kyoto Institute of technology (Japon), respectivement, dans le cadre d’une co-tutelle.Les travaux sur la formation des particules a été réalisée dans un plasma RF généré dans un mélange gazeux composé d’Argon (Ar, 98%) et d’Acétylène (C2H2, 2%). Le processus de formation des particules s’effectue en trois étapes: la nucléation (phase chimique), l'agglomération, et la croissance par dépôt radicalaire sur la surface des particules. Nous sommes intéressés à l'étape de nucléation. L'influence de la puissance, la pression et la température des gaz sur le temps de nucléation est étudiée. L'évolution temporelle de la tension d'auto polarisation de la décharge est utilisée comme un indice pour détecter la fin de l'étape de nucléation. Les résultats montrent que le temps de nucléation augment avec l'augmentation de la température mais diminue avec celle de la puissance et de la pression. Cela dit, plus la température est basse, la puissance et la pression sont élevées, plus la phase de nucléation est rapide. La dépendance de la nucléation de la température est expliquée par le mécanisme de la relaxation de l’excitation translationnelle-vibrationnelle des molécules du gaz précurseur. En effet l’énergie d’excitation vibrationnelle joue le rôle d’énergie d’activation pour les réactions chimiques ayant lieu lors de cette phase. Par contre, celles sur la puissance et la pression, elles sont expliqué
This thesis studies the dust particles in plasmas. It consists of two parts. The first part is the formation of dust particles, that is to study how the dust particles are generated from the reactive gas in the plasmas. The second part is the transport behaviour of dust particles, that is to study how the dust particles act in the plasmas.In the part of the formation of dust particles, carbon dust particles are generated in the plasmas. It is known that the formation process of dust particles in plasmas can be determined by 3 steps: nucleation, agglomeration and surface grow. The nucleation step is focused. The results of experiments show that the nucleation process occurs faster in higher power, higher pressure and lower temperature. The dependency of the nucleation time on the temperature is explained by the vibration-transition energy relaxation mechanism, and that on the RF power and pressure is explained by the ratio of the charge and diffusion time of the small dust particles.In the part of the transport behaviours of dust particles, industrially fabricated particles with determined size are injected into Ar plasmas. The particles in the plasmas are observed by laser scattering with a CCD camera. The diagnostics of plasma are performed by a double langmuir probe. Pulse-time modulation to the Ar RF plasmas is studied to be a factor to influence and to control the transport of dust particles. Particles of mono-dispersed size are firstly studied in the plasmas. It is shown that the levitating positions and falling down processes can be controlled by the RF power and pulse-time modulation. Secondly, two sizes particles are injected into the plasma at same time. The different transport behaviours, as like the segmentation of levitation and different timing of falling down basis on their size, are observed. Particles of mixture sizes can be separated one size particles from other sizes. The mechanisms of transport behaviours of the dust particles are investigated by the combination of the diagnostic of plasma parameters (electron temperature and ion density in principle) by the double langmuir probe and calculation of the forces acting on the dust particles. Calculation methods adjusting to the specific experiment setup are established. The calculation results have a good agreement with that of the experiments

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Marichal, Laurent. "Interactions protéines-nanoparticules : émergence de nouveaux facteurs déterminant la formation de la couronne de protéines". Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS100/document.

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Les nanoparticules sont de plus en plus présentes dans notre quotidien et leur présence dans les organismes vivants est aujourd’hui avérée. Aussi, dans un milieu biologique, des protéines recouvrent spontanément la surface des nanoparticules pour former une couronne de protéines. Suivant la composition de cette couronne, une nanoparticule acquiert une "identité biologique" spécifique qui peut conditionner sa biodistribution ainsi que son éventuelle toxicité.De nombreuses zones d’ombre persistent quant à la connaissance des mécanismes d’adsorption des protéines sur les nanoparticules. Deux caractéristiques physico-chimiques, peu abordées jusqu’à maintenant, ont été étudiées ici : la taille des protéines et la présence de modification post-traductionnelles. Aussi, du fait de leur forte utilisation, nous nous sommes concentrés sur les nanoparticules de silice (SiNPs).L’adsorption d’hémoprotéines, de nature similaire mais de tailles différentes, sur des SiNPs, elles-mêmes de tailles différentes, a été étudiée. Les isothermes d’adsorption et les titrations calorimétriques ont notamment montré qu’il existe une relation entre la taille des protéines et leur affinité pour une surface de silice. Des différences plus fines ont aussi pu être observées selon la taille des nanoparticules. Une analyse structurale des protéines adsorbées a également été effectuée par dichroïsme circulaire et diffusion de neutrons aux petits angles. Les hémoprotéines apparaissent comme des protéines très structurées qui sont peu affectées par l’adsorption. Cependant, bien que la structure quaternaire soit conservée, des modifications structurales sont observables.Des études faites en présence de mélanges de protéines (extraits de protéines de levure) ainsi que de peptides de synthèse ont également montré le rôle important de la diméthylation asymétrique de l’arginine sur l’interaction protéines/SiNPs. L’utilisation d’un panel de techniques expérimentales et de simulations a permis de comprendre le mécanisme responsable de la forte affinité de peptides contenant cette méthylation particulière. De façon plus générale, nos travaux suggèrent que les modifications post-traductionnelles peuvent influencer notablement les interactions de biomolécules avec des surfaces minérales
Nanoparticles are ubiquitous in our environment and their presence inside our bodies is now established. Besides, in a biological medium, nanoparticles are spontaneously covered by proteins that form the so-called protein corona. Depending on the corona composition, a nanoparticle will possess a specific "biological identity" conditioning its biodistribution as well as its potential toxicity.Despite being highly studied, many aspects of the protein adsorption mechanisms remain unknown. Here we particularly focused on the influence of two physicochemical characteristics, which had rarely been addressed: protein size and post-translational modifications. Also, because of their intensive use, we worked on silica nanoparticles (SiNPs).We studied the adsorption of hemoproteins on SiNPs, both of them having different sizes. Adsorption isotherms and calorimetry studies showed a relationship between the protein size and its affinity towards silica surfaces. Finer differences could also be observed by varying the SiNPs size. Additionally, structural analyses of adsorbed proteins were performed using circular dichroism and small-angle neutron scattering. The adsorption of hemoproteins, which are well-structured proteins, seems to have little effects on their structure. However, even though the quaternary structure is maintained, structural modifications can be seen.Using yeast protein extracts and synthetic peptides, the major role of arginine asymmetric dimethylation on proteins/SiNPs interaction could be established. The use of experimental and simulation techniques allowed us to understand the mechanism responsible for the high affinity of peptides having this peculiar methylation. As a whole, this work suggests that post-translational modifications can influence considerably the interactions between biomolecules and mineral surfaces

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Mullaugh, Katherine M. "Formation and persistence of cadmium sulfide nanoparticle in aqueous solution". Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 232 p, 2009. http://proquest.umi.com/pqdweb?did=1885682071&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.

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Miclea, Paul-Tiberiu. "Formation and characterization of metal nanoparticle coatings on oxide nanospheres". [S.l.] : [s.n.], 2002. http://deposit.ddb.de/cgi-bin/dokserv?idn=965234754.

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Song, Delong. "Starch crosslinking for cellulose fiber modification and starch nanoparticle formation". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39524.

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As a low cost natural polymer, starch is widely used in paper, food, adhesive, and many other industries. In order to improve the performance of starch, crosslinking is often conducted either in the processes of starch modification or during the application processes. Many crosslinkers have been developed in the past for crosslinking starch. Ammonium zirconium carbonate (AZC) is one of the common crosslinkers for crosslinking starch in aqueous solutions, having been widely used as a starch crosslinking agent in paper surface coating for more than 20 years. However, the mechanisms of starch crosslinking with AZC have not been well studied. In order to optimize the crosslinking chemistry of starch and find new paths for the utilization of starch in papermaking, a better understanding of the starch crosslinking mechanism is necessary. This thesis focuses on the fundamental study of starch crosslinking in an aqueous solution and its applications in fiber surface grafting, filler modification, and starch nanoparticle formation. Particularly, the thesis contains three major parts: (1) Mechanism study of starch crosslinking induced by AZC: In this thesis, the crosslinking (or gelation) kinetics of starch/AZC blends were investigated by using rheological measurements. The evolution of viscoelastic properties of AZC solutions and the AZC-starch blends was characterized. It was found that for both AZC self-crosslinking and AZC-starch co-crosslinking, the initial bond formation rate and the gel strength had a strong power law relationship with the concentrations of both AZC and starch. It is suggested that the development of the crosslinking network is highly dependent on the AZC concentration, while the starch concentration effect is less significant. It was determined that the activation energy of AZC self-crosslinking was approximately 145-151 kJ/mol, while the activation energy of AZC-starch co-crosslinking was 139 kJ/mol. (2) Fiber and filler modifications with starch and crosslinkers: Besides reacting with starch, AZC can react with cellulose which also contains hydroxyl groups. Theoretically, it is possible to use AZC as a crosslinker / coupling agent to graft starch onto cellulose fibers. It is believed that the grafted starch on fiber surfaces can improve the fiber bonding capability. In this thesis, a facile method to graft starch onto cellulose fiber surfaces through the hydrogen bond formation among cellulose, starch and AZC was developed. Compared with the paper sheets made of fibers with an industry refining level (420 ml CSF), the paper sheets made of fibers with a much lower refining degree but with grafted starch showed higher paper strengths, including the tensile strength, stiffness and z direction tensile; meanwhile, a faster drainage rate during web formation could also be achieved. Not only can the fiber-fiber bonding be improved by grafting starch onto fiber surfaces, but the filler-fiber bonding can also be improved if starch can be effectively coated on the filler surface. This concept has been supported by the early studies. In this thesis, the effects of the crosslinking of starch in the filler modification for the papermaking application were also studied. (3) Mechanism of starch nanoparticle formation during extrusion with crosslinkers: It was reported that starch crosslinking could facilitate the reduction of starch particle size during reactive extrusion. However, the mechanism of the particle size reduction by starch crosslinking was not illustrated. The reason that the crosslinking can cause the particle size reduction of starch during extrusion is fundamentally interesting. In this thesis, the mechanism of starch particle size reduction during extrusion with and without crosslinkers was investigated by identifying the contributions of thermal and mechanical effects. The effects of extrusion conditions, including temperature, screw speed, torque, starch water content and crosslinker addition, on the particle size were studied. It was found that the addition of crosslinkers could significantly increase the shear force (torque), and consequently facilitate the reduction of the particle size. The results indicate that for extrusion without a crosslinker, the starch particle size decreased with the increase of temperature. At 100 degree Celsius, the starch particles with a size of 300 nm could be obtained. With the addition of appropriate crosslinkers (glyoxal), the starch particle size could be reduced to around 160 nm, even at a lower extrusion temperature of 75 degree Celsius .

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Vancea, Ioan. "Pattern formation in nanoparticle suspensions : a Kinetic Monte Carlo approach". Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8420.

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Various experimental settings that involve drying solutions or suspensions of nanoparticles often called nano-fluids have recently been used to produce structured nanoparticle layers. In addition to the formation of polygonal networks and spinodal-like patterns, the occurrence of branched structures has been reported. After reviewing the experimental results, the work presented in this thesis relies only on simulations. Using a modified version of the Monte Carlo model first introduced by Rabani et al. [95] the study of structure formation in evaporating films of nanoparticle solutions for the case that all structuring is driven by the interplay of evaporating solvent and diffusing nanoparticles is presented. The model has first been used to analyse the influence of the nanoparticles on the basic dewetting behaviour, i.e., on spinodal dewetting and on dewetting by nucleation and growth of holes. We focus, as well, on receding dewetting fronts which are initially straight but develop a transverse fingering instability. One can analyse the dependence of the characteristics of the resulting branching patterns on the driving effective chemical potential, the mobility and concentration of the nanoparticles, and the interaction strength between liquid and nanoparticles. This allows to understand the underlying fingering instability mechanism. We describe briefly how the combination of a Monte Carlo model with a Genetic Algorithm (GA) can be developed and used to tune the evolution of a simulated self-organizing nanoscale system toward a predefined nonequilibrium morphology. This work has presented evolutionary computation as a method for designing target morphologies of self-organising nano-structured systems. Finally, highly localised control of 2D pattern formation in colloidal nanoparticle arrays via surface inhomogeneities created by atomic force microscope (AFM) induced oxidation is presented and some simulations are shown. Furthermore, the model can be extended further, and by including the second type of nanoparticle, the binary mixture behaviour can be captured by simulations. We conclude that Kinetic Monte Carlo simulations have allowed the study of the processes that lead to the production of particular nanoparticle morphologies.

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15

Mendoza, Gonzalez Norma Yadira. "CFD Modeling of nanoparticle formation in a plasma synthesis reactor". Mémoire, Sherbrooke : Université de Sherbrooke, 2003. http://savoirs.usherbrooke.ca/handle/11143/1206.

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16

Akroyd, Jethro. "Mean reaction rate closures for nanoparticle formation in turbulent reacting flow". Thesis, University of Cambridge, 2012. https://www.repository.cam.ac.uk/handle/1810/244968.

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This thesis investigates mean reaction rate closures for turbulent reacting flow. The closures model the mean rate of reaction in the flow and are applied to simulations of nanoparticle formation. The simulations couple detailed chemical reaction, particle population dynamics and turbulent flow, and offer the potential to improve the understanding of a range of industrial processes. The numerical behaviour of a mean reaction rate closure based on the direct quadrature method of moments using the interaction by exchange with the mean micromixing model (DQMoM-IEM) is studied in detail. An analytic expression is presented for the source terms and a filter function introduced to address issues of boundedness and singularity. Analytic integrals are presented for special cases of specific terms. The implementation of the method in the Star-CD computational fluid dynamics code is described in detail and validated against a test problem. The numerical performance of DQMoM-IEM is systematically compared to the stochastic fields (SF) turbulent reaction model. The methods share many similarities and are presented in a common mathematical framework for the first time. They differ in their treatment of key terms that make DQMoM-IEM numerically challenging. A variance reduction technique using antithetic sampling is introduced to increase the efficiency of the SF method. However, DQMoM-IEM is shown to remain competitive for the test problem considered. A new methodology is presented to couple a detailed particle model to simulations of turbulent reacting flow. A projected fields (PF) method based on DQMoM-IEM is used to combine detailed chemistry and the method of moments with interpolative closure (MoMIC) population balance model in Star-CD. The method is applied to the example of the chloride process for the industrial synthesis of titania nanoparticles and includes full coupling between the flow, chemistry and particles undergoing simultaneous inception, coagulation and surface growth.

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17

Altman, Igor, i n/a. "Peculiarities of Nanoparticle Formation and Implications to Generation of Environmental Aerosols". Griffith University. School of Environmental Engineering, 2005. http://www4.gu.edu.au:8080/adt-root/public/adt-QGU20051111.122816.

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This Thesis considers peculiarities of nanoparticle formation from the gas in different systems. The main role of the surface condensation in the nanoparticle growth in metal flames was established through a series of experiments and was described by the developed model. The stagnation of the post-nucleation nanoparticle growth was experimentally revealed and theoretically explained. The influence of generation conditions on the post-processing nanoparticle properties was examined. The non-isothermal approach to correct the homogeneous nucleation theory was developed. The results of this work can be summarized in 3 categories: (1) Nanoparticle formation in metal flames. In this work, it was demonstrated that the surface condensation is a main process responsible for nanooxides growth during metal combustion. It was shown that the rate of this condensation growth is consistent with the exponential law, which could lead to the formation of the lognormal particle size distribution in the system, where the Brownian coagulation is suppressed. The post-nucleation stagnation of the nanoparticle growth was found. The particle overheating was suggested as a cause of the growth stagnation. The found stagnation leads to the accumulation of the supercritical clusters in the system generating nanoparticles. The role of these supercritical clusters in the nanoparticle agglomeration was considered. (2) Study of properties of nanoparticles generated in different metal flames. The light absorption, photoluminescence and magnetic properties of nanoparticles produced in different metal flames were examined. The significant broadening of the absorption edge was found in nanooxides produced by direct metal combustion. This broadening allowed one to excite the unforeseen photoluminescence from these nanoparticles. The significant light absorption in the visible light found in the titania particles produced by metal combustion allows one to consider these particles as a prospective photocatalyst. The unusual optical properties revealed were related to the extreme conditions of the nanoparticle formation, namely, to high energy release (about 5 eV per condensing molecule). The stabilization of spinel structure was found in iron oxide particles synthesized by iron combustion. It allowed one to produce nanoparticles with magnetization close to the high-limit value of the bulk. (3) Approach to correct the homogeneous nucleation theory. The existing homogeneous nucleation theory implies that nucleation occurs at isothermal conditions, i.e. subcritical clusters have the same temperature as the ambient gas does. However, the theory overestimates the actual nucleation rate and underestimates the critical cluster size. It is understandable that due to release of the latent heat of condensation, the cluster temperature in the nucleating system should be higher than the environment temperature. In this work, it was suggested the method to account for the cluster overheating during nucleation. It was demonstrated that the consistent description of the detailed balance in the nucleating system may allow one to evaluate magnitudes of overestimation of the actual nucleation rate and underestimation of the number of molecules in the critical cluster, usually obtained by the isothermal nucleation theory. The numerical estimates are in good agreement with the wellknown experimental results. The implications of the results to generation of atmospheric aerosols were discussed.

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18

Udoh, Christiana. "Formation of polymer-nanoparticle capsules with tuneable morphologies by solvent extraction". Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/59753.

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Capsules are employed in a range of industries as essential vehicles for the storage and delivery of drugs, biologically active species, surfactants, and personal care formulations. Key performance aspects are dictated by the capsule's overall shape and dimensions, porosity and internal microstructure. Various approaches are employed in the fabrication of capsules with precise size and shape control. This work focuses on the formation of capsules by the selective removal of solvent from monodisperse solution droplets - produced using microfluidics - upon immersion in an external solvent. The microfluidic generation of microporous polymer capsules using an ex-situ phase inversion process is presented and the effect of various process parameters on capsule structure and internal microstructure examined. These include polymer concentration, droplet size and non-solvent quality. Further, the effect of ternary solution thermodynamics on the microstructure of the capsules is explored, and precise control over pore size and distribution is demonstrated. Building on these findings and polymer-colloid phase behaviour, the fabrication of nanocomposite capsules, generated from polymer-nanoparticle mixtures, is reported and a well-defined external and internal morphology diagram established. These include nucleated and bicontinuous microstructures, as well as isotropic and non-isotropic external shapes. Upon dissolution, rapid and modulated, pulsed, release of the nanoparticle clusters over timescales ranging seconds to hours is demonstrated. The release profile is found to be dependent on capsule morphology, and a systematic study of the role of extraction solvent and kinetics on capsule gradient structure is presented; this provides an effective strategy to decouple demixing and coarsening timescales from the capsule solidification time, and is exploited to controllably design capsules with varied internal microstructures: hollow, core-shell, bicontinuous and compact domains. Overall, the work presents a robust and facile microfluidic approach for the design and fabrication of microcapsules, exhibiting a wide range of internal and external morphologies, by exploiting solution/mixture thermodynamics, solvent exchange kinetics, and phase inversion.

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19

Yaacob, Khatijah Aisha. "Formation and characterisation of CdSe-TiO2 nanoparticle films by electrophoretic deposition". Thesis, Imperial College London, 2011. http://hdl.handle.net/10044/1/6917.

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Electrophoretic deposition (EPD) was used to form a composite layer of mercaptoundeconic acid (MUA) capped CdSe-TiO2 nanoparticle on a fluorine doped indium tin oxide (FTO) substrate. The CdSe-TiO2 layer can be employed to fabricate a quantum dot sensitized solar cells (QDSSC), increased contact between CdSe and TiO2 nanoparticles and leading to improved efficiency of the solar cells. A colloidal suspension of TOPO capped CdSe nanoparticles was prepared by the hot injection method, followed with ligand exchange in order to produce MUA capped CdSe nanoparticles. CdSe particle of diameter in the range of 2.44 nm to 3.26 nm were to be used in this research. The TiO2 nanoparticles were prepared by hydrolysis of titanium isopropoxide in water and produced particles size of 4.66 nm. Both nanoparticles were suspended in ethanolic medium. Electrophoretic deposition parameters were optimized. The results show that an applied voltage of 5 V, was suitable to be used to deposit single layer of MUA capped CdSe, TiO2 nanoparticles and the mixture of MUA capped CdSe-TiO2 nanoparticles. Smooth, uniform and dense layer were produced under this applied voltage. EPD also allows deposition of multilayer structures, in this research two layer structures of MUA capped CdSe on electrophoretically deposited TiO2 on FTO and mixed MUA capped CdSe-TiO2 on electrophoretically deposited TiO2 on FTO were formed. Three layer structures of MUA capped CdSe/MUA capped CdSe-TiO2/ TiO2/FTO were also synthesised. The photocurrent was measured on single layer, two layer and three layers electrodes. The optimum photocurrent parameters for each single layer were studied, in order to measure the photocurrent at the best condition possible. The highest IPCE value recorder was 0.70 % on MUA capped CdSe on FTO, with the MUA capped CdSe size of 2.94 nm. The lowest IPCE, 0.011 %, was obtained from three layer structure of MUA capped CdSe/MUA capped CdSe-TiO2/ TiO2/FTO.

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20

Altman, Igor. "Peculiarities of Nanoparticle Formation and Implications to Generation of Environmental Aerosols". Thesis, Griffith University, 2005. http://hdl.handle.net/10072/366347.

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This Thesis considers peculiarities of nanoparticle formation from the gas in different systems. The main role of the surface condensation in the nanoparticle growth in metal flames was established through a series of experiments and was described by the developed model. The stagnation of the post-nucleation nanoparticle growth was experimentally revealed and theoretically explained. The influence of generation conditions on the post-processing nanoparticle properties was examined. The non-isothermal approach to correct the homogeneous nucleation theory was developed. The results of this work can be summarized in 3 categories: (1) Nanoparticle formation in metal flames. In this work, it was demonstrated that the surface condensation is a main process responsible for nanooxides growth during metal combustion. It was shown that the rate of this condensation growth is consistent with the exponential law, which could lead to the formation of the lognormal particle size distribution in the system, where the Brownian coagulation is suppressed. The post-nucleation stagnation of the nanoparticle growth was found. The particle overheating was suggested as a cause of the growth stagnation. The found stagnation leads to the accumulation of the supercritical clusters in the system generating nanoparticles. The role of these supercritical clusters in the nanoparticle agglomeration was considered. (2) Study of properties of nanoparticles generated in different metal flames. The light absorption, photoluminescence and magnetic properties of nanoparticles produced in different metal flames were examined. The significant broadening of the absorption edge was found in nanooxides produced by direct metal combustion. This broadening allowed one to excite the unforeseen photoluminescence from these nanoparticles. The significant light absorption in the visible light found in the titania particles produced by metal combustion allows one to consider these particles as a prospective photocatalyst. The unusual optical properties revealed were related to the extreme conditions of the nanoparticle formation, namely, to high energy release (about 5 eV per condensing molecule). The stabilization of spinel structure was found in iron oxide particles synthesized by iron combustion. It allowed one to produce nanoparticles with magnetization close to the high-limit value of the bulk. (3) Approach to correct the homogeneous nucleation theory. The existing homogeneous nucleation theory implies that nucleation occurs at isothermal conditions, i.e. subcritical clusters have the same temperature as the ambient gas does. However, the theory overestimates the actual nucleation rate and underestimates the critical cluster size. It is understandable that due to release of the latent heat of condensation, the cluster temperature in the nucleating system should be higher than the environment temperature. In this work, it was suggested the method to account for the cluster overheating during nucleation. It was demonstrated that the consistent description of the detailed balance in the nucleating system may allow one to evaluate magnitudes of overestimation of the actual nucleation rate and underestimation of the number of molecules in the critical cluster, usually obtained by the isothermal nucleation theory. The numerical estimates are in good agreement with the wellknown experimental results. The implications of the results to generation of atmospheric aerosols were discussed.
Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental Engineering
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21

Faivre, Damien. "Biological and biomimetic formation and organization of magnetic nanoparticles". Thesis, Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7202/.

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Biological materials have ever been used by humans because of their remarkable properties. This is surprising since the materials are formed under physiological conditions and with commonplace constituents. Nature thus not only provides us with inspiration for designing new materials but also teaches us how to use soft molecules to tune interparticle and external forces to structure and assemble simple building blocks into functional entities. Magnetotactic bacteria and their chain of magnetosomes represent a striking example of such an accomplishment where a very simple living organism controls the properties of inorganics via organics at the nanometer-scale to form a single magnetic dipole that orients the cell in the Earth magnetic field lines. My group has developed a biological and a bio-inspired research based on these bacteria. My research, at the interface between chemistry, materials science, physics, and biology focuses on how biological systems synthesize, organize and use minerals. We apply the design principles to sustainably form hierarchical materials with controlled properties that can be used e.g. as magnetically directed nanodevices towards applications in sensing, actuating, and transport. In this thesis, I thus first present how magnetotactic bacteria intracellularly form magnetosomes and assemble them in chains. I developed an assay, where cells can be switched from magnetic to non-magnetic states. This enabled to study the dynamics of magnetosome and magnetosome chain formation. We found that the magnetosomes nucleate within minutes whereas chains assembles within hours. Magnetosome formation necessitates iron uptake as ferrous or ferric ions. The transport of the ions within the cell leads to the formation of a ferritin-like intermediate, which subsequently is transported and transformed within the magnetosome organelle in a ferrihydrite-like precursor. Finally, magnetite crystals nucleate and grow toward their mature dimension. In addition, I show that the magnetosome assembly displays hierarchically ordered nano- and microstructures over several levels, enabling the coordinated alignment and motility of entire populations of cells. The magnetosomes are indeed composed of structurally pure magnetite. The organelles are partly composed of proteins, which role is crucial for the properties of the magnetosomes. As an example, we showed how the protein MmsF is involved in the control of magnetosome size and morphology. We have further shown by 2D X-ray diffraction that the magnetosome particles are aligned along the same direction in the magnetosome chain. We then show how magnetic properties of the nascent magnetosome influence the alignment of the particles, and how the proteins MamJ and MamK coordinate this assembly. We propose a theoretical approach, which suggests that biological forces are more important than physical ones for the chain formation. All these studies thus show how magnetosome formation and organization are under strict biological control, which is associated with unprecedented material properties. Finally, we show that the magnetosome chain enables the cells to find their preferred oxygen conditions if the magnetic field is present. The synthetic part of this work shows how the understanding of the design principles of magnetosome formation enabled me to perform biomimetic synthesis of magnetite particles within the highly desired size range of 25 to 100 nm. Nucleation and growth of such particles are based on aggregation of iron colloids termed primary particles as imaged by cryo-high resolution TEM. I show how additives influence magnetite formation and properties. In particular, MamP, a so-called magnetochrome proteins involved in the magnetosome formation in vivo, enables the in vitro formation of magnetite nanoparticles exclusively from ferrous iron by controlling the redox state of the process. Negatively charged additives, such as MamJ, retard magnetite nucleation in vitro, probably by interacting with the iron ions. Other additives such as e.g. polyarginine can be used to control the colloidal stability of stable-single domain sized nanoparticles. Finally, I show how we can “glue” magnetic nanoparticles to form propellers that can be actuated and swim with the help of external magnetic fields. We propose a simple theory to explain the observed movement. We can use the theoretical framework to design experimental conditions to sort out the propellers depending on their size and effectively confirm this prediction experimentally. Thereby, we could image propellers with size down to 290 nm in their longer dimension, much smaller than what perform so far.
Biologische Materialien wie Knochen, Muscheln und Holz wurden von den Menschen seit den ältesten Zeiten verwendet. Diese biologisch gebildeten Materialien haben bemerkenswerte Eigenschaften. Dies ist besonders überraschend, da sie unter physiologischen Bedingungen und mit alltäglichen Bestandteilen gebildet sind. Die Natur liefert uns also nicht nur mit Inspiration für die Entwicklung neuer Materialien, sondern lehrt uns auch, wie biologische Additiven benutzen werden können, um einfache synthetische Bausteine in funktionale Einheiten zu strukturieren. Magnetotaktischen Bakterien und ihre Kette von Magnetosomen sind ein Beispiel, wo einfache Lebewesen die Eigenschaften von anorganischen Materialien steuern, um sich entlang den magnetischen Feldlinien der Erde zu orientieren. Die von den Bakterien gebildeten Magnetosomen sind von besonderem Interesse, da mit magnetischen Eisenoxid-Nanopartikeln in den letzten zehn Jahren einer Vielzahl von Bio-und nanotechnologischen Anwendungen entwickelt worden sind. In dieser Arbeit stelle ich eine biologische und eine bio-inspirierte Forschung auf der Grundlage der magnetotaktischen Bakterien vor. Diese Forschung verbindet die neuesten Entwicklungen von Nanotechnik in der chemischen Wissenschaft, die neuesten Fortschritte der Molekularbiologie zusammen mit modernen Messverfahren. Mein Forschungsschwerpunkt liegt somit an der Schnittstelle zwischen Chemie, Materialwissenschaften, Physik und Biologie. Ich will verstehen, wie biologische Systeme Materialien synthetisieren und organisieren, um Design-Prinzipien zu extrahieren, damit hierarchischen Materialien mit kontrollierten Eigenschaften nachhaltig gebildet werden.

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Chittipotula, Thirumalesha [Verfasser], i Dominique [Akademischer Betreuer] Thevenin. "Numerical prediction of nanoparticle formation in flames / Thirumalesha Chittipotula. Betreuer: Dominique Thévenin". Magdeburg : Universitätsbibliothek, 2012. http://d-nb.info/1053914326/34.

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Menéndez-Manjón, Tartiere Ana [Verfasser]. "Metal nanoparticle formation by laser ablation in liquids / Ana Menéndez-Manjón Tartiere". Hamburg : tredition, 2012. http://d-nb.info/1027046932/34.

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Jenei, István Zoltán. "Nanoparticle assisted tribofilm formation and material transfer studied with SEM and TEM". Doctoral thesis, Stockholms universitet, Fysikum, 2015. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-114745.

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The discovery and subsequent synthesis of metal containing fullerenes- IFS (Inorganic Fullerene-like Structures) by R. Tenne et al. has generated considerable scientific interest with great potential impact in many industrial application areas such as lubrication. The lubrication mechanism (tribofilm formation) via exfoliation and deposition of the atomic layers from this cage-like IF-particles was revealed and demonstrated first by this research group. The incorporation of the nanoparticles into lubricants (oils, greases) is however not straightforward. When two surfaces are sliding against each other and a lubricant is used, a thin layer (tribofilm) is formed on the contact area. The friction reducing effects of the nanoparticles can be altered or hindered by certain additives that are used in lubricative oils. The effects of such additives on the tribological behavior of the nanoparticles are investigated by analyzing the tribofilms formed on the worn surfaces using energy-dispersive X-ray spectroscopy in a scanning electron microscope. Another challenge of nanoparticles in lubricants is the penetration of the nanoparticles into the contact zone. A possible solution of this problem is briefly discussed. A modified burnishing technique can be used to coat sliding metallic surfaces with a friction reducing tribofilm. The morphology and composition of these tribofilms was investigated with analytical electron microscopy techniques. In the second part of the thesis electron microscopy was used to investigate the material transfer. Titanium is an elements with high adhesive ability to the counter surface, it displays poor tribological properties in sliding metallic contacts. This can lead to material transfer and consequently severe surface damage. The cold formation and machining of titanium, thus can lead rapid tool wear and poor surface finish. Electron microscopy techniques were used to study the mechanism of titanium transfer to different counter surfaces.

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25

VITALI, MICHELE. "Dynamics of nanoparticle-protein corona: formation, evolution and insight on protein structure". Doctoral thesis, Università degli Studi di Milano-Bicocca, 2018. http://hdl.handle.net/10281/199091.

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In tamponi fisiologici, le proteine formano complessi transitori con nanoparticelle (NP), mediati da adsorbimento competitivo alla superficie di quest’ultime, fino alla formazione di una corona proteica stabile (HPC). Lo studio della dinamica d’interazione è fondamentale per ideare terapie basate su NP, in quanto l'HPC determina l'identità biologica delle NP in vivo. La forte affinità tra superfici di NP e proteine può compensare la destabilizzazione che le NP sperimentano in tamponi ad elevata forza ionica, stabilizzandole. Quest’interazione è immediata (soft -non stabile -PC) ma evolve nel tempo (HPC). Numerosi approcci volti a studiare la composizione dell'HPC hanno raffigurato uno scenario confuso, a causa delle dimensioni delle NP (comparabili con proteine) e della complessità composizionale del siero. Molti di questi studi non offrono un metodo affidabile per determinare la composizione dell'HPC e in alcuni casi sono contraddittori. La scarsa conoscenza della risposta dei nanomateriali in mezzi biologici è un punto chiave di queste controversie. Numerosi parametri, come l’aggregazione, sono sottostimati, ma risultano critici per comprendere la formazione dell'HPC. È necessario quindi sviluppare un protocollo semplice ma efficiente ed affidabile per studiare questi processi. In questo lavoro si è studiata la formazione di NP-PC con un approccio semplice e attendibile, al fine di determinare composizione e proprietà fisicochimiche dell'HPC oltre alle propriteà strutturali delle proteine adsorbite. Nella prima parte è studiato l’evoluzione nel tempo del PC su NP di oro 20 nm, come modello di NP metalliche utilizzato in medicina, monitorando evoluzione di proprietà fisicochimiche del PC con spettroscopia UV-Vis, Dynamic Light Scattering, Z-Potential. L’evoluzione dell’HPC proveniente dall'incubazione in siero è confrontata con quella risultante dall'incubazione con solo albumina o IgG, le proteine sieriche più abbondanti. L'evoluzione del PC quando coniugato con una proteina, è inteso come un'impronta digitale dell'adsorbimento di quella specifica proteina. Pertanto, questo confronto suggerisce la composizione finale dell'HPC. La dinamica del PC proveniente dal siero esibisce la dominanza fisicochimica dell'albumina, con poche differenze forse collegate alla presenza di composti minori nell’HPC. L'analisi proteomica conferma il risultato. L'HPC mantiene le sue caratteristiche nel tempo ed esercita un effetto protettivo sul nucleo della NP se introdotte in condizioni di attacco chimico (NaCN e HNO3) che mimano la degradazione metabolica del PC. La proteolisi limitata dell’HPC indica un’alterata metabolizzazione proteica all'interno dell'HCC, probabilmente dovuta ad una sua variazione strutturale. Nella seconda parte, HPC è studiato su NP di SiO2 di 50 nm, come modello di NP di ossido utilizzato in nanomedicina, utilizzando sia proteine globulari che intrinsecamente disordinate (IDP), con lo scopo di indagare cambiamenti conformazionali indotti dall'interazione con NP. Le IDP esistono in soluzione in un insieme conformazionale, le cui caratteristiche in presenza di NP sono sconosciute. Tre IDP, a-caseina, Sic1 e a-sinucleina sono state analizzate rispetto a lisozima e transferrina (proteine globulari modello). Le struttura nell’HPC è studiata mediante dicroismo circolare e spettroscopia infrarossa a trasformata di Fourier. I risultati indicano che le IDP mantengono il disordine strutturale all'interno dell'HPC, sperimentando minori transizioni conformazionali ma essendo stabilizzate contro variazioni dell’intorno. Le globulari, invece, tendono a perdere la loro struttura ordinata. Le proteine nell'HPC sono visualizzate mediante elettroforesi mentre microscopia elettronica mostra un HPC formato da un singolo strato di molecole proteiche. Quest'ultima parte apre ampie prospettive sull'uso di NP come agenti che imitano partner molecolari.
In complex physiological media proteins form transient complexes with nanoparticles (NPs), mediated by competitive binding between proteins and NP surfaces, leading to the formation of a stable (hard) protein corona (HPC). Understanding the formation and the dynamics of this interaction is crucial for designing NP-based therapies, since HPC determines the biological identity of the NPs in vivo. The strong affinity between NPs surfaces and proteins can compensate the destabilization forces that colloidal NPs experience in high ionic strength media, stabilizing them. This interaction is immediate (soft -non stable –PC) and evolves with time (HPC). Nowadays, different studies regarding HPC composition show contradictory results. The complexity of serum composition, being NP size in the same range of proteins, and lack of reliable methods to determine composition of HPC, are behind these controversies. Several underestimated parameters regarding the response of NPs in physiological media (aggregation, dissolution) are critical determinants to be carefully addressed to better understand the formation of the HPC. In this context, it is necessary to develop simple but efficient and reliable protocols to study these processes. In this work, consequences of NP-PC formation providing a simple and reliable approach for determining both composition and physicochemical characterization of the HPC, and the implication for protein structures, is shown. In the first part, the hardening of the PC on 20 nm AuNPs, as a model case of metallic NP widely used in medicine, was monitored over time by UV-Vis spectroscopy, Dynamic Light Scattering and Z-Potential. Results of the process of HPC formation with only albumin or IgG were compared to results of HPC formation in serum. Time evolution of the NP-PC when conjugated with one protein can be understood as a fingerprint of the adsorption of that specific protein. Thus, the study of the PC evolution in serum provided information about the final composition of the HPC. Results showed similar pattern as when incubated when only albumin. Proteomic analysis confirmed the results. In addition, experiments mimicking the natural metabolic degradations of bioconjugates using etching agents (NaCN and HNO3), indicated that HPC exert protective effect on the NP core. Finally, limited proteolysis experiments indicated an altered metabolization of the protein inside the HPC, which can be related to a protein altered conformation in this adsorbed state. In the second part, HPC was studied on 50 nm SiO2 NPs, as a model case of metal oxide NP widely used in nanomedicine, by using either globular and intrinsically disordered proteins (IDPs), with the aim to investigate conformational changes induced by the interaction with NPs. IDPs exist in solution as conformational ensembles, whose features in the presence of NPs are still unknown. Three IDPs, acasein, Sic1 and asynuclein, were analyzed compared to lysozyme and transferrin (globular proteins model), describing conformational properties inside the HPC by circular dichroism and Fourier-transform infrared spectroscopy. Results indicated that IDPs maintain structural disorder inside HPC, experiencing minor, protein-specific, induced folding and stabilization against further conformational transitions. Oppositely, the analyzed globular proteins displayed the tendency to lose their ordered structure. Finally, the Transferrin-Tb complex, was also used in the HPC formation. The detection of the fluorescent properties of Tb upon HPC preparation is reported. By electrophoresis it was observed all the proteins forming the HPC and electron microscopy showed an HPC of a single layer of protein molecules. This latter part of work opens broad perspectives on the use of NP as agents that mimic macromolecular partners, allowing the comprehension of the effect of different factors affecting the interaction by rational design of NP surfaces.

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Souva, Matthew Scott. "High Throughput Block Copolymer Nanoparticle Assembly Methods". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503101272745765.

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Zhang, Xiaolu. "NANOPARTICLE BEHAVIOR IN BIOLOGICAL GELS AND BIOFLUIDS: THE IMPACT OF INTERACTIONS WITH CHARGED BIOGELS AND THE FORMATION OF PROTEIN CORONAS ON NANOPARTICLES". UKnowledge, 2015. http://uknowledge.uky.edu/chemistry_etds/57.

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With the rapid growth of nanotechnology, situations where nanomaterials will interact with biological systems will unquestionably grow. Therefore, it is increasingly understood that interactions between nanomaterials and biological environments will play an essential role in nanomedicine. Biological polymer networks, including mucus and the extracellular matrix, serve as a filter for the exchange of molecules and nanoparticles. Such polymer networks are complex and heterogeneous hydrogel environments that regulate transport processes through finely tuned particle-network interactions. In chapters 3 and 4, we investigate the role of electrostatics on the basic mechanisms governing the diffusion of charged molecules inside model polymer networks by using fluorescence correlation spectroscopy (FCS). In chapter 3, we show that particle transport of charged probe molecules in charged hydrogels is highly asymmetric and that the filtering capability of the gel is sensitive to the solution ionic strength. Brownian dynamics simulations are in quantitative agreement with our experimental result. In chapter 4, we focus on hyperbranched cationic dendrimer macromolecules (polyamidoamine, PAMAM) which differ from probes in size, charge density and chain flexibilities. Our results show PAMAM has strongly reduced mobility in like charge gels and greatly enhanced apparent diffusivity in oppositely charged gels. Further studies with salt suggest that the oppositely charged polymer network acts as a giant counterion enhancing the mobility of PAMAM by changing its conformation to a more compacted state. Due to their large surface areas, nanomaterials in biological fluids are modified by adsorption of biomolecules, mainly proteins, to form so called “protein coronas”. These coronas ultimately define the biological identity of the nanoparticles and dictate the interactions of cells with the protein-NP complex. We have studied the adsorption of human transferrin and bovine serum albumin on the surface of sulfonated polystyrene nanoparticle. In chapter 5, we show the formation of multi-layered protein coronas and compare to established adsorption models. In addition we followed for the first time the protein binding kinetics as a function of pH and salt. Through these studies, we aim to gain quantitative knowledge of the dynamic rearrangement of proteins on engineered nanomaterials.

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Schneider, Cornelia Marion [Verfasser]. "Investigation of Early Clusters in Nanoparticle Formation by Analytical Ultracentrifugation / Cornelia Marion Schneider". Konstanz : KOPS Universität Konstanz, 2019. http://d-nb.info/122457561X/34.

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Mendoza, Gonzalez Norma Yadira. "Theoretical study of nanoparticle formation in thermal plasma processing Nucleation, coagulation and aggregation". Thèse, Université de Sherbrooke, 2008. http://savoirs.usherbrooke.ca/handle/11143/1831.

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This work presents a mathematical modeling study of the synthesis of nanoparticles in radio frequency (RF) inductively coupled plasma (ICP) reactors. The purpose is to further investigate the influence of process parameters on the final size and morphology of produced particles. The proposed model involves the calculation of flow and temperature fields of the plasma gas. Evaporation of raw particles is also accounted with the particle trajectory and temperature history calculated with a Lagrangian approach. The nanoparticle formation is considered by homogeneous nucleation and the growth is caused by condensation and Brownian coagulation. The growth of fractal aggregates is considered by introducing a power law exponent Df. Transport of nanoparticles occurs by convection, thermophoresis and Brownian diffusion. The method of moments is used to solve the particle dynamics equation. The model is validated using experimental results from plasma reactors at laboratory scale. The results are presented in the following manner. First, use is made of the computational fluid dynamics software (CFD), Fluent 6.1 with a commercial companion package specifically developped for aerosols named: Fine Particle Model (FPM). This package is used to study the relationship between the operating parameters effect and the properties of the end products at the laboratory scale. Secondly, a coupled hybrid model for the synthesis of spherical particles and fractal aggregates is developped in place of the FPM package. Results obtained from this model will allow to identify the importance of each parameter in defining the morphology of spherical primary particles and fractal aggregates of nanoparticles. The solution of the model was made using the geometries and operating conditions of existing reactors at the Centre de Recherche en Energie, Plasma et Electrochimie (CREPE) of the Université de Sherbrooke, for which experimental results were obtained experimentally. Additionally, this study demonstrates the importance of the flow and temperature fields on the growth of fractal particles; namely the aggregates.

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30

Schneider, Cornelia M. [Verfasser]. "Investigation of Early Clusters in Nanoparticle Formation by Analytical Ultracentrifugation / Cornelia Marion Schneider". Konstanz : KOPS Universität Konstanz, 2019. http://d-nb.info/122457561X/34.

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Rothfuß, Hannah [Verfasser], i C. [Akademischer Betreuer] Barner-Kowollik. "Single-Chain Nanoparticle Formation Induced by Metal Complexation / Hannah Rothfuß ; Betreuer: C. Barner-Kowollik". Karlsruhe : KIT-Bibliothek, 2019. http://d-nb.info/118832182X/34.

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Izuhara, Masayasu. "Prevention of neointimal formation using miRNA-126-containing nanoparticle-conjugated stents in a rabbit model". Kyoto University, 2018. http://hdl.handle.net/2433/231000.

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Lohse, Samuel E. 1981. "Direct Synthesis of Thiolate-Protected Gold Nanoparticles Using Bunte Salts as Ligand Precursors: Investigations of Ligand Shell Formation and Core Growth". Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11531.

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xx, 242 p. : ill. (some col.)
Applications of ligand-protected nanoparticles have increased markedly in recent years, yet their controlled synthesis remains an under-developed field. Nanoparticle syntheses are highly specialized in their execution and often possess significant limitations. For example, the synthesis of thiol-stabilized gold nanoparticles (AuNPs) with core diameters greater than 5.0 nm is difficult to achieve using existing methods. This dissertation describes the development of a synthetic strategy for thiolate-stabilized AuNPs over a wide range of core sizes using alkyl thiosulfates (Bunte salts) as ligand precursors. The use of Bunte salts permits the synthesis of larger AuNPs than can be achieved using thiols by allowing the AuNP cores to grow to larger diameters before the formation of the thiolate ligand shell. Chapter II details the development of a direct synthesis strategy using Bunte salts as ligand precursors that produces AuNPs with diameters up to 20 nm. Chapter III describes an investigation of the ligand shell formation that occurs during these syntheses. The ligand shell formation involves the adsorption of the Bunte salt to the AuNP surface, where it is converted to the thiolate. This conversion requires an excess of sodium borohydride in the synthesis of >5 nm AuNPs, but not for the synthesis of smaller AuNPs. This synthetic strategy was adapted for use in flow reactors to attain simultaneous AuNP synthesis and characterization. Chapter IV demonstrates that thiol-stabilized AuNPs can be synthesized in a microfluidic device with product monitoring provided by UV-vis absorbance spectroscopy. The development of a capillary flow reactor that permits the incorporation of new monitoring techniques is presented in Chapter V. The incorporation of Small-Angle X-ray Scattering (SAXS) analysis provides quantitative in situ determinations of AuNP diameter. The combination of synthetic control and monitoring makes capillary flow reactors powerful tools for optimization of NP syntheses and monitoring NP growth. In Chapter VI, the capillary flow reactor is used in an investigation of AuNP core growth. We also review AuNP growth mechanisms and show how to differentiate these using SAXS and UV-vis analysis. In these studies, AuNP growth is unexpectedly shown to involve a coalescence mechanism. This dissertation includes previously published and co-authored material.
Committee in charge: Victoria De Rose Chairperson; James E. Hutchison, Advisor; Catherine Page, Member; Darren W. Johnson, Member; Miriam Deutsch, Outside Member

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Paskevicius, Mark. "A nanostructural investigation of mechanochemically synthesised hydrogen storage materials". Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/254.

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Aluminium, aluminium hydride (alane), and magnesium hydride nanoparticles have been mechanochemically synthesised in order to study their hydrogen sorption properties in contrast to the bulk. Nanoparticle formation was facilitated by the addition of a salt phase to ball milled chemical reagents that matched the reaction byproduct phase. The presence of a salt buffer during ball milling prevents agglomeration and thus restricts particle growth.Aluminium nanoparticles were mechanochemically synthesised with particle sizes from 40 – 55 nm. The LiCl salt by-product phase was removed by washing with a nitromethane/AlCl[subscript]3 solution resulting in 55 nm Al particles (single crystals) that did not display any crystalline oxide phases. High pressure hydrogen absorption experiments were undertaken up to 2 kbar at temperatures from 77 – 473 K to examine if there were any major thermodynamic changes to the Al. No hydrogen absorption could be detected proving that either smaller Al is required to form AlH3 under these conditions or higher pressures are needed. Ni-coated and Ti-doped Al nanoparticles were also synthesised in order to verify if catalytic metals could enhance hydriding kinetics and allow hydrogenation to occur at lower pressures. However the doped samples did not display any hydrogen absorption up to 108 bar.Alane nanoparticles were synthesised using both room temperature and cryogenic mechanochemical synthesis with particle sizes < 100 nm. The evolution of alane production was investigated as a function of milling time under a variety of milling conditions. Cryogenic milling was verified to form higher yields of AlH[subscript]3 than room temperature milling and four different alane phases (α, α', β, γ) were identified by XRD structural investigations. The LiCl reaction by-product phase was removed by washing with a nitromethane/AlCl[subscript]3 solution, which adversely reacted with the AlH[subscript]3 nanoparticles. The hydrogen desorption kinetics in washed samples were hindered, and the maximum H[subscript]2 wt.% was halved although no crystalline oxide or hydroxide phases were found using XRD. Unwashed mechanochemically synthesised AlH[subscript]3 was found to desorb at room temperature over months and significantly at 50ºC in a 24 hr period. Quantitative Rietveld results coupled with hydrogen desorption measurements suggested the presence of an amorphous AlH[subscript]3 phase in the mechanochemically synthesised samples.The mechanochemical synthesis of MgH[subscript]2 was undertaken with varying LiCl buffer quantities. Increasing the buffer resulted in MgH[subscript]2 crystallite sizes down to 6.7 nm, measured by XRD, whilst TEM investigations showed that increasing the buffer resulted in smaller, more highly dispersed MgH[subscript]2 nanoparticles. The size of these MgH[subscript]2 particles approached theoretical predictions for thermodynamic changes, where the MgH[subscript]2 is only physically bound by the LiCl. Hydrogen equilibrium pressure measurements were used to determine the decomposition enthalpy and entropy for MgH[subscript]2 nanoparticles that were mechanochemically synthesised. A reduction in both the decomposition enthalpy (ΔH decrease of 2.84 kJ/mol H[subscript]2) and entropy (ΔS decrease of 3.8 J/mol H[subscript]2/K) was found for ~7 nm MgH[subscript]2 nanoparticles in relation to bulk MgH[subscript]2. The consequence of this thermodynamic destabilization is a drop in the 1 bar hydrogen equilibrium pressure of ~6°C. The temperature drop is not as large as theoretical predictions due to the decrease in reaction entropy which partially counteracts the effect from the decrease in reaction enthalpy.

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McKenzie, Lallie Cobb. "Mechanistic insights on nanoparticle formation : investigation of reaction pathways and development of controlled synthesis for triphenylphosphine-stabilized undecagold /". Connect to title online (ProQuest), 2009. http://proquest.umi.com/pqdweb?did=1798969441&sid=1&Fmt=2&clientId=11238&RQT=309&VName=PQD.

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Govender, Yageshni. "Isolation, purification and characterization of a 'factor' from Fusarium oxysporum responsible for platinum nanoparticle formation". Thesis, Rhodes University, 2008. http://hdl.handle.net/10962/d1003982.

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Nanoparticles are microscopic particles in the nanometre range of between 1-100 nm. A wide variety of metal nanoparticles have been found to be produced by prokaryotic and eukaryotic organisms including several fungal species, when exposed to solutions containing metal salts. Previous studies have suggested that this bioreduction of metal particles may occur via an active reductase/hydrogenase enzyme process where H2 is the electron donor and positively charged platinum species act as the electron acceptors becoming reduced to a neutral metal nanoparticle. In view of this on going research, the current study investigated the “factors” in the fungus Fusarium oxysporum which were responsible for platinum nanoparticle formation. The fungus F.oxysporum was used in this study as it has been previously shown to produce a variety of nanoparticles including gold and silver. During exposure of the biomass to H2PtCl6 the initial response to the platinum salts was metal internalisation and subsequent reduction of H2PtCI6 to produce platinum nanoparticles. The observed localization and distribution of platinum precipitates provided some evidence for a hydrogenase mediated bioreduction of platinum salts to produce nanoparticles. Factors secreted by the fungus into the extracellular fluids, were shown to be responsible for platinum nanoparticle formation. From the identification, purification and characterisation studies it was concluded that a hydrogenase and other “factors” were responsible for platinum nanoparticle formation in F.oxysporum. Purification of the hydrogenase by freeze-drying and Sephacryl S200 size exclusion- ion exchange chromatography revealed the enzyme to be a dimer with a 29.4 and 44.5 kDa when analysed by a 10 % SDS-PAGE. Characterisation of the enzyme revealed optimal activity at a pH of 7.5 and temperature of 38 °C while it exhibited a poor thermal stability with a half life of 36 minutes. The kinetic parameters Vmax and Km were 3.16 U ml-1 and 3.64 mM respectively. The purified hydrogenase was used in subsequent experiments for the reduction of platinum salts, H2PtCl6 and PtCl2. the results indicated an over 90 % reduction of the platinum salts and TEM micrographs indicated the production of platinum nanoparticles under the various experimental conditions.

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Redkov, A. V., A. A. Lipovskii i V. V. Zhurikhina. "Formation and Self-arrangement of Nanocomposite Materials via Glass Anneal in Hydrogen". Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34796.

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The process of metal nanoparticles formation in glass during its annealing in hydrogen is studied. On the basis of phase transition theory the strict system of equations describing this process is developed and simulated. The simulation shows that the system has two qualitatively different solutions: continuous distribution of nanoparticles in bulk glass and Liesegang-like layers. The results of the numerical modeling agree well with known experimental data: both types of the distributions have been registered in experiments. The dependence of final nanoparticles distribution on system parameters (initial concentrations diffusion coefficients) has been analysed. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34796

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Zimmermann, M., i G. Garnweitner. "Formation Studies on the Nonaqueous Synthesis of Metal Oxide Nanoparticles in a 1.5 L Reactor System". Thesis, Sumy State University, 2012. http://essuir.sumdu.edu.ua/handle/123456789/34891.

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In the last years, the nonaqueous synthesis has been demonstrated as a highly versatile method for the simple synthesis of highly crystalline metal oxide nanoparticles and nanomaterials. Thereby, we have presented the synthesis of a multitude of different metal oxides (e.g., TiO2, ZrO2, BaTiO3, Fe3O4). The mechanisms of particle formation as well as the influence of process parameters on the particle properties however remain largely unknown so far, as the molecular mechanisms are rather complex. In this paper, we show that the synthesis of metal oxide nanoparticles is feasible also on a multi-gram reactor scale on the example of anatase TiO2 nanoparticles. Using a reactor system equipped with a sampling system for with-drawal of samples at different stages of the reaction, the kinetics of particle formation could be determined and compared to the formation of organic side products and water. Additionally, insights into the influence of different process parameters on the particle properties are shown and can be utilized to tailor size and morphology of the product nanoparticles. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/34891

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Couëdel, Lénaïc Gaël Hervé Fabien. "Nanoparticle formation and dynamics in a complex (dusty) plasma : from the plasma ignition to the afterglow". Connect to full text, 2008. http://hdl.handle.net/2123/4121.

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Thesis (Ph. D.)--University of Sydney, 2009.
Includes graphs and tables. Cotutelle thesis submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the Complex Plasma Laboratory, School of Physics, Faculty of Science, University of Sydney and the degree of Docteur de l'Université Orléans. Title from title screen (viewed May 5, 2009) Degree awarded 2009; thesis submitted 2008. Includes bibliographical references. Also available in print form.

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40

Couedel, Lenaic Gael Herve Fabien. "Nanoparticle formation and dynamics in a complex (dusty) plasma: from the plasma ignition to the afterglow". Thesis, The University of Sydney, 2008. http://hdl.handle.net/2123/4121.

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Complex (dusty) plasmas are a subject of growing interest. They areionized gases containing charged dust particles. In capacitively-coupled RF discharges, dust growth can occur naturally and two methods can be used to grow dust particles: chemically active plasmas or sputtering. The growth of dust particles in argon discharges by RF sputtering and the effect of dust particles on theplasma have been investigated from the plasma ignition to the afterglow. It was shown that plasma and discharge parameters are greatly affected by the dust particles. Furthermore, plasma instabilities can be triggered by the presence of the dust particles. These instabilities can be due to dust particle growth or they can be instabilities of a well established dust cloud filling the interelectrode space. When the discharge is switched off, the dust particles act like a sink for the charge carrier and consequently affect the plasma losses. It was shown that the dust particles do keep residual chargeswhich values are greatly affected by the diffusion of the charge carriers and especially the transition from ambipolar to free diffusion.

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Couedel, Lenaic Gael Herve Fabien. "Nanoparticle formation and dynamics in a complex (dusty) plasma: from the plasma ignition to the afterglow". University of Sydney, 2008. http://hdl.handle.net/2123/4121.

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Doctor of Philosophy(PhD)
Complex (dusty) plasmas are a subject of growing interest. They areionized gases containing charged dust particles. In capacitively-coupled RF discharges, dust growth can occur naturally and two methods can be used to grow dust particles: chemically active plasmas or sputtering. The growth of dust particles in argon discharges by RF sputtering and the effect of dust particles on theplasma have been investigated from the plasma ignition to the afterglow. It was shown that plasma and discharge parameters are greatly affected by the dust particles. Furthermore, plasma instabilities can be triggered by the presence of the dust particles. These instabilities can be due to dust particle growth or they can be instabilities of a well established dust cloud filling the interelectrode space. When the discharge is switched off, the dust particles act like a sink for the charge carrier and consequently affect the plasma losses. It was shown that the dust particles do keep residual chargeswhich values are greatly affected by the diffusion of the charge carriers and especially the transition from ambipolar to free diffusion.

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Mothiba, Maborwa Tebogo. "The effects of clofazimine on mycobacterium smegmatis biofilm formation". Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/31569.

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Chemotherapy of tuberculosis (TB), a disease caused by Mycobacterium tuberculosis (M. tuberculosis), is successful against actively-growing bacilli but ineffective against dormant/persistent organisms, found mainly in a protective lipid-laden granuloma, possibly necessitating the use of lipophilic antibiotics. In vitro, these bacilli are encased in lipid-rich biofilms. In this study, the antimycobacterial activity of one such agent, clofazimine, and its nanoparticle formulation, have been investigated against Mycobacterium smegmatis (M. smegmatis), as a surrogate for M. tuberculosis, by determining the bacteriostatic and bactericidal activities of the native (NC) and spray-dried (SDC) preparations of this agent on planktonic and biofilm populations, as well as their effects on biofilm formation and its lipid compositions, specifically free mycolic acid (FM) content. Both preparations were comparable, being bacteriostatic for rapidly-proliferating bacilli, bactericidal for slow-growing, biofilm-producing sessile bacteria, but ineffective against non-replicating, biofilm-encased M. smegmatis organisms. However, similar studies in M. tuberculosis are required.
Dissertation (MSc)--University of Pretoria, 2013.
Immunology
Unrestricted

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Lemoine, Asseline. "Organisation et ségrégation lors de la formation de nanoalliages d'AgCo étudiés par diffusion aux petits et aux grands angles et effet anomal". Thesis, Orléans, 2015. http://www.theses.fr/2015ORLE2067/document.

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Ce travail de thèse a pour objectif d'étudier les rôles de la taille, de la composition et de la cinétique de croissance sur la morphologie, la structure, et l'état de mélange de l'argent et du cobalt dans des nanoparticules bimétalliques supportées AgCo. Dans ce but, des mesures in-situ et en temps réel par diffusion des rayons X aux petits et aux grands angles en géométrie d'incidence rasante, et en condition anomale, ont été effectuées au cours de la croissance des nanoparticules AgCo dans des conditions de dépôt simultané ou successif des métaux. Des recuits ont ensuite été réalisés afin d'étudier la stabilité des structures obtenues à température ambiante, et d'observer d'éventuelles transitions activées thermiquement. Pour l'ensemble des modes de dépôt, les nanoparticules (dans une gamme de taille comprise entre 2 et 7nm) présentent une configuration chimique ségrégée. Pour des dépôts successifs de Co puis d'Ag, les nanoparticules sont constituées d'un (ou plusieurs) domaine(s) d'Ag juxtaposé(s) à un domaine de Co, tandis que pour un dépôt d'Ag puis de Co les particules présentent une configuration de type coeur-coquille (Co-Ag). Pour les dépôts simultanés, la configuration cœur-coquille est obtenue à très faible composition en Ag (< ou =20%), au-delà la configuration multidomaines monométalliques est observée. Quelle que soit la configuration initiale, le recuit conduit à une séparation de phase des métaux sous forme de particules Janus et à des réorganisations structurales
The aim of this work is to study the role of size, composition and growth kinetic conditions on the morphology, the structure and the chemical configuration of AgCo bimetallic supported nanoparticles. Thus, in-situ and in real-time anomalous grazing incidence small and wide angle X-ray scattering measurements were performed during AgCo nanoparticles growth. Two types of growth conditions were studied : simultaneous or successive deposition of the two metals. Samples were also annealed to study the stability of the structures observed at room temperature, and to investigate if structural transitions occur due to thermal activation. For all kind of deposition modes, the nanoparticles (in a size range between 2 and 7 nm) exhibit a segregated chemical configuration. For the deposition of Co followed by Ag deposition, the nanoparticles are constituted of one (or several) Ag domain(s) juxtaposed with a Co domain, whereas for Ag deposition followed by Co deposition, the nanoparticles present a (Co-Ag) core-shell configuration. For simultaneous depositions and Ag poor compositions (< or =20%), the core-shell configuration is obtained. For richer compositions, the multidomain configuration is observed. Whatever the initial configuration, annealing leads to a phase separation of the two metals towards Janus particles and some structural reorganizations occur

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Picone, Carolina Siqueira Franco 1983. "Formação de nanopartículas por associação de biopolímeros e surfactantes = Formation of nanoparticles by biopolymer - surfactant association". [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/254194.

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Orientador: Rosiane Lopes da Cunha
Texto em português e inglês
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
Made available in DSpace on 2018-08-20T12:57:32Z (GMT). No. of bitstreams: 1 Picone_CarolinaSiqueiraFranco_D.pdf: 4074904 bytes, checksum: 1a2779daa118fabb35ba241a8f6bf16f (MD5) Previous issue date: 2012
Resumo: As nano partículas possuem grande potencial para a liberação controlada de bioativos, porém ainda são pouco exploradas na área de alimentos. Neste trabalho foi estudada a formação de nanopartículas a partir da autoagregação de surfactantes, associação surfactante-polissacarídeo e complexação eletrostática entre diferentes polissacarídeos, no caso, quitosana e gelana. A compreensão das interações moleculares responsáveis pela formação das partículas e o conhecimento das variáveis que afetam sua formação permitem predizer e controlar suas propriedades. Tais interações dependem fortemente das características de cada macromolécula, como flexibilidade, estado conformacional e densidade de cargas que são diretamente afetadas pelas condições físico-químicas do meio como pH, força iônica e temperatura. Por isso, este trabalho foi dividido em três etapas. (I) Inicialmente foi avaliado o comportamento em solução dos polissacarídeos utilizados posteriormente para a formação de complexos. Os efeitos do pH e da temperatura nas características reológicas e no estado conformacional de soluções puras de gelana e quitosana foram estudados. A agregação da gelana foi mais sensível às alterações do meio que a quitosana. (II) Na segunda etapa, nanopartículas foram formadas por autoassociação de polissorbatos na presença de quitosana. A influência do comprimento da cauda hidrofóbica do surfactante e do pH do meio nas propriedades das partículas foi estudada por espalhamento de luz, reologia, condutivimetria e microscopia de luz polarizada. O tamanho e estrutura das partículas formadas pelo surfactante de menor cadeia hidrofóbica foram mais favoráveis à associação com a quitosana. O pH do meio (3,0 ou 6,7) não influenciou de maneira significativa as características das partículas. O efeito da concentração de quitosana na estrutura e tamanho de partículas foi analisado. Maiores concentrações levaram a viscosidades mais elevadas, impedindo a agregação das micelas e formando partículas menores. (III) No terceiro estudo, nanopartículas foram obtidas pela complexação eletrostática de gelana e quitosana. Os efeitos da razão de concentração de cada polissacarídeo, do tempo de estocagem a 25 °C e da presença de um surfactante nãoiônico (polissorbato) no tamanho, carga e quantidade de partículas formadas foram avaliados. Devido à menor densidade de carga e flexibilidade da gelana, maior quantidade deste polissacarídeo foi necessária para obtenção de partículas neutras. De forma geral, as partículas apresentaram aumento de tamanho ao longo das primeiras 100 horas após o preparo e não foram observadas mudanças significativas das propriedades das partículas devido à adição de surfactante. O método de preparo das amostras também foi estudado. Partículas preparadas pela mistura das soluções de polissacarídeos em dois passos foram consideravelmente maiores que as preparadas pela mistura em uma única etapa. Este trabalho confirmou a possibilidade de formação de nanopartículas promissoras para a encapsulação de bioativos em alimentos a partir da associação de biopolímeros e surfactantes, cujas propriedades poderiam ser moduladas em função da composição e condições de processo
Abstract: Nanoparticles are promising vehicles for bioactive delivery, but their potential has not been fully explored by the food industry. This work studied the formation of nanoparticles by self-assembly of surfactants, polysaccharide-surfactant association, and electrostatic complexes formed by different polysaccharides, especially chitosan and gellan gum. The knowledge of molecular interactions and the variables that affect particle formation allows predicting and controlling the properties of nanoparticles. These interactions depend on the characteristics of each macromolecule such as conformation, charge density and flexibility, which are affected by the physicol-chemical properties of the solution, such as pH, ionic strength and temperature. This work was divided in three parts: (I) Firstly it was studied the behaviour of each polysaccharide alone. The influence of the pH and temperature on the rheological properties and structural conformation of the pure gellan and chitosan samples was determined. Gellan aggregation was more strongly affected by such variables than chitosan. (II) In the second part, nanoparticles were obtained by polysorbate-chitosan association. The effect of the length of surfactant tail and the solution pH on the particle properties was studied by dynamic light scattering, rheological and conductivity measurements and polarizing microscopy. The size and structure of nanoparticles composed by the shorter surfactant were more appropriated to chitosan assembly. The pH (6.7 or 3.0) did not affect significantly the particle properties. The effects of chitosan concentration on particle structure and size were studied. Greater chitosan concentration led to smaller particles due to the increase in viscosity values which prevented micelles aggregation. (III) In the third study nanoparticles were produced by electrostatic complexation of chitosan and gellan gum. Particle size, charge density, stability and complexes number were evaluated as a function of polysaccharide concentration, chitosan:gellan ratio and the presence of a non-ionic surfactant. Due to the stiffness and low charge density of gellan gum, a greater amount of such polysaccharide was necessary to obtain neutral particles. Overall particles showed an increase in size during 100 hours of storage at 25 °C, but no significant changes on particle properties were observed due to surfactant addition. The methodology of particle preparation was also evaluated. Particles prepared by 2 mixing steps were markedly larger than those prepared by mixing polysaccharides in a single step (all together). This work showed that it is possible to produce nanoparticles with promising application on bioactive delivery by biopolymer-surfactant association, since their properties could be modulated as a function of composition and process conditions
Doutorado
Engenharia de Alimentos
Doutor em Engenharia de Alimentos

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Boudie, Claire. "Physical characterisation of ionic liquid solutions and their potential applications as media for nanoparticle formation or batteries". Thesis, Queen's University Belfast, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.725391.

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In this study, solutions of 1-ethyl-2-methylimidazolium acetate, butanoate and octanoate ILs in binary mixtures with water will be investigated with the aim to investigate the effect of aggregation by increasing the carbon chain lengths from 2 to 8 carbons of the alkyl-carboxylate anion. A wide range of techniques will be applied, starting from the characterisation of their physical properties as well as spectroscopic techniques in function of temperature and mixture compositions in order to gain a full understanding of their interaction behaviour. Furthermore, these carboxylate ionic liquids will be used in two separate applications. The first application will use those solutions to make copper(ll) oxide nanoparticles by an in-situ method and to investigate the role of ILs and the presence of water in the nanoparticle formation. The second application will use ILs in binary mixture with a new solvent; propylene carbonate (PC), to investigate the role of these ILs in terms of overcoming current safety-issues with electrolytes for sodium-ion batteries. Those two applications are supported by a comprehensive study on the IL binary mixtures with water which will lead to a better understanding of the role of these ILs as “designer solvent”.

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Ahmed, Selver. "FORMATION, DYNAMICS AND CHARACTERIZATION OF SUPPORTED LIPID BILAYERS ON SiO2 NANOPARTICLES". Diss., Temple University Libraries, 2012. http://cdm16002.contentdm.oclc.org/cdm/ref/collection/p245801coll10/id/213126.

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Chemistry
Ph.D.
This work is devoted to understanding the formation of supported lipid bilayers (SLBs) on curved surfaces as a function of lipid properties such as headgroup charge/charge density and alkyl chain length, and nanoparticle properties such as size and surface characteristics. In particular, the formation of SLBs on curved surfaces was studied by varying the size of the underlying substrate SiO2 nanoparticles with size range from 5-100 nm. Curvature-dependent shift in the phase transition behavior of these supported lipid bilayers was observed for the first time. We found that the phase transition temperature, Tm of the SLBs first decreased with decreasing the size of the underlying support, reached a minimum, and then increased when the size of the particles became comparable with the dimensions of the lipid bilayer thickness; the Tm was above that of the multilamellar vesicles (MLVs) of the same lipids. The increase in Tm indicated a stiffening of the supported bilayer, which was confirmed by Raman spectroscopic data. Moreover, Raman data showed better lipid packing and increased lateral order and trans conformation for the SLBs with increasing the curvature of the underlying support and decrease of the gauche kinks for the terminal methyl groups at the center of the bilayer. These results were consistent with a model in which the high free volume and increased outer headgroup spacing of lipids on highly curved surfaces induced interdigitation in the supported lipids. These results also support the symmetric lipid exchange studies of the SLBs as a function of the curvature, which was found to be slower on surfaces with higher curvature. Further, the effect of surface properties on the formation of SLBs was studied by changing the silanol density on the surface of SiO2 via thermal/chemical treatment and monitoring fusion of zwitterionic lipids onto silica (SiO2) nanoparticles. Our findings showed that the formation of SLBs was faster on the surfaces with lower silanol density and concomitantly less bound water compared to surfaces with higher silanol density and more bound water. Since the two SiO2 nanoparticles were similar in other respects, in particular their size and charge (ionization), as determined by zeta potential measurements, differences in electrostatic interactions between the neutral DMPC and SiO2 could not account for the difference. Therefore the slower rate of SLB formation of DMPC onto SiO2 nanoparticles with higher silanol densities and more bound water was attributed to greater hydration repulsion of the more hydrated nanoparticles. Lastly, we have investigated the effect and modulation of the surface charge of vesicles on the formation of SLBs by using different ratios of zwitterionic and cationic DMPC/DMTAP lipids. Through these studies we discovered a procedure by which assemblies of supported lipid bilayer nanoparticles, composed of DMPC/DMTAP (50/50) lipids on SiO2, can be collected and released from bilayer sacks as a function of the phase transition of these lipids. The lipids in these sacks and SLBs could be exchanged by lipids with lower Tm via lipid transfer.
Temple University--Theses

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Huang, Yan. "Micro- and Nanogel Formation through the Ionic Crosslinking of Polyelectrolytes". University of Toledo / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=toledo1417781855.

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Flegg, Mark Bruce. "Theoretical investigation of mechanisms of formation and interaction of nanoparticles". Thesis, Queensland University of Technology, 2010. https://eprints.qut.edu.au/31843/1/Mark_Flegg_Thesis.pdf.

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In this thesis an investigation into theoretical models for formation and interaction of nanoparticles is presented. The work presented includes a literature review of current models followed by a series of five chapters of original research. This thesis has been submitted in partial fulfilment of the requirements for the degree of doctor of philosophy by publication and therefore each of the five chapters consist of a peer-reviewed journal article. The thesis is then concluded with a discussion of what has been achieved during the PhD candidature, the potential applications for this research and ways in which the research could be extended in the future. In this thesis we explore stochastic models pertaining to the interaction and evolution mechanisms of nanoparticles. In particular, we explore in depth the stochastic evaporation of molecules due to thermal activation and its ultimate effect on nanoparticles sizes and concentrations. Secondly, we analyse the thermal vibrations of nanoparticles suspended in a fluid and subject to standing oscillating drag forces (as would occur in a standing sound wave) and finally on lattice surfaces in the presence of high heat gradients. We have described in this thesis a number of new models for the description of multicompartment networks joined by a multiple, stochastically evaporating, links. The primary motivation for this work is in the description of thermal fragmentation in which multiple molecules holding parts of a carbonaceous nanoparticle may evaporate. Ultimately, these models predict the rate at which the network or aggregate fragments into smaller networks/aggregates and with what aggregate size distribution. The models are highly analytic and describe the fragmentation of a link holding multiple bonds using Markov processes that best describe different physical situations and these processes have been analysed using a number of mathematical methods. The fragmentation of the network/aggregate is then predicted using combinatorial arguments. Whilst there is some scepticism in the scientific community pertaining to the proposed mechanism of thermal fragmentation,we have presented compelling evidence in this thesis supporting the currently proposed mechanism and shown that our models can accurately match experimental results. This was achieved using a realistic simulation of the fragmentation of the fractal carbonaceous aggregate structure using our models. Furthermore, in this thesis a method of manipulation using acoustic standing waves is investigated. In our investigation we analysed the effect of frequency and particle size on the ability for the particle to be manipulated by means of a standing acoustic wave. In our results, we report the existence of a critical frequency for a particular particle size. This frequency is inversely proportional to the Stokes time of the particle in the fluid. We also find that for large frequencies the subtle Brownian motion of even larger particles plays a significant role in the efficacy of the manipulation. This is due to the decreasing size of the boundary layer between acoustic nodes. Our model utilises a multiple time scale approach to calculating the long term effects of the standing acoustic field on the particles that are interacting with the sound. These effects are then combined with the effects of Brownian motion in order to obtain a complete mathematical description of the particle dynamics in such acoustic fields. Finally, in this thesis, we develop a numerical routine for the description of "thermal tweezers". Currently, the technique of thermal tweezers is predominantly theoretical however there has been a handful of successful experiments which demonstrate the effect it practise. Thermal tweezers is the name given to the way in which particles can be easily manipulated on a lattice surface by careful selection of a heat distribution over the surface. Typically, the theoretical simulations of the effect can be rather time consuming with supercomputer facilities processing data over days or even weeks. Our alternative numerical method for the simulation of particle distributions pertaining to the thermal tweezers effect use the Fokker-Planck equation to derive a quick numerical method for the calculation of the effective diffusion constant as a result of the lattice and the temperature. We then use this diffusion constant and solve the diffusion equation numerically using the finite volume method. This saves the algorithm from calculating many individual particle trajectories since it is describes the flow of the probability distribution of particles in a continuous manner. The alternative method that is outlined in this thesis can produce a larger quantity of accurate results on a household PC in a matter of hours which is much better than was previously achieveable.

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Dichiara, Anthony. "Etude chronologique de la formation de nanotube de carbone par CVD d'aérosol à l'aide de diagnostics in situ : des premiers instants à la fin de la croissance". Phd thesis, Ecole Centrale Paris, 2012. http://tel.archives-ouvertes.fr/tel-00763604.

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Dans le vaste domaine des nanosciences et nanotechnologies, les nanotubes de carbone (NTC) suscitent un intérêt particulier en raison de leur structure originale qui leur confère des propriétés exceptionnelles. Alors que le nombre d'applications ainsi que la quantité de NTC produite ne cessent d'augmenter chaque année, il est essentiel de comprendre les mécanismes régissant la formation de ces nanomatériaux afin de contrôler leur structure et leur organisation, optimiser les rendements, diminuer les risques sanitaires et environnementaux et améliorer les performances des matériaux et composants sous-jacents. Parmi les techniques de synthèse répertoriées, la CVD d'aérosol (Chemical Vapor Deposition) développée au laboratoire MSSMat, permet la croissance continue de NTC multi-feuillets de haute qualité sur divers substrats par l'injection simultanée de sources carbonées liquide (xylène) et gazeuse (acétylène) et de précurseur catalytique (ferrocène) dans un réacteur porté à une température comprise entre 400 et 1000°C. L'objectif de cette étude a consisté à examiner les différentes étapes de la formation des NTC dès l'injection des précurseurs jusqu'à la fin de la croissance. Grâce une nouvelle approche expérimentale faisant intervenir plusieurs diagnostics in situ couplés à des modèles numériques, nous avons pu suivre l'évolution des différents réactifs et produits lors de synthèses dans des conditions thermodynamiques (flux de gaz et températures) et chimiques (concentrations des différents précurseurs) variées. De fait, après avoir examiné l'évolution spatiale des gouttelettes formées lors de l'injection, la germination des nanoparticules en phase gazeuse a été étudiée par incandescence induite par laser (L2I) et spectroscopie de plasma induit par laser (LIPS). Une relation entre la taille de ces particules et celle des NTC a ainsi pu être mise en évidence. Les réactions chimiques pendant la synthèse ont ensuite été analysées par spectrométrie de masse et chromatographie en phase gazeuse. Différents mécanismes réactionnels ont ainsi pu être identifiés en fonction des sources de carbone utilisées, alors que l'effet de l'hydrogène sur la croissance, soit accélérateur ou soit inhibiteur selon les conditions, a été étudié. Les rôles du substrat ont par ailleurs été examinés en comparant la croissance et la morphologie des NTC obtenus sur différentes surfaces telles que des plaques de quartz, des fibres de carbone ou des micro-particules d'alumine, de carbure de silicium, de carbure de titane et de graphène de formes variées. L'effet catalytique de certains substrats ou mélanges de substrats sur la croissance des NTC a d'ailleurs été mis en évidence, de même que l'importance du rapport surface/volume des substrats sur les rendements massiques des NTC. La cinétique de croissance des NTC a finalement été étudiée et différents mécanismes à l'origine de la désactivation des catalyseurs ont été identifiés. Enfin, les différentes nanostructures hybrides issues de la croissance de NTC sur différents substrats ont servi à concevoir des matériaux composites multi-fonctionnels à hautes-performances dont les propriétés électriques, thermiques et mécaniques ont été analysées.

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Wang, Dong. "Nouveaux catalyseurs recyclables pour les réactions de formation de liaisons carbone-carbone et carbone-azote". Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0128/document.

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Les catalyseurs supportés sur des dendrimères et nanoparticules magnétiques acquièrent actuellement une importance accrue dans le contexte de la chimie verte et du développement durable car ils sont séparés facilement des produits de réaction par filtration ou à l’aide d’un aimant et recyclables. Dans cet esprit, la thèse a été dédiée à la synthèse, à la caractérisation et aux applications catalytiques de catalyseurs moléculaires, nano-et dendritiques immobilisés impliquant le ruthénium, le cuivre et le palladium. Les catalyseurs magnétiquement recyclables de ruthenium (II), de cuivre (I) et des nanoparticules de palladium ont produit d’excellentes performances en terme d’activité, de stabilité et de recyclabilité pour les réactions de cycloaddition entre les alcynes et les azotures et les réactions de couplage croisé carbone-carbone. Enfin, la synthèse de complexes mono-et polymétalliques du palladium contenant les ligands 2-pyridyl-1,2,3-triazole a également été réalisée et leurs proprietiés catalytiques ont été étudiées
Catalysts based on dendrimers and magnetic nanoparticles are becoming increasing utilized in the context of green and sustainable chemistry, because they are easily separated by precipitation or by using asimple magnet respectively, and they are recyclable. In this spirit, the thesis has been devoted to the synthesis, characterization and catalytic applications of iron oxide magnetic nanoparticles-immobilized molecular, nano-and dendritic catalysts involving Ru, Cu and Pd. Magnetically recyclable ruthenium(II) and Cu(I) complexes and Pd nanoparticles have provided excellent catalytic performances in terms of activity, stability and recyclability, using alkyne-azide cycloaddition and carbon-carbon cross coupling reactions. The synthesis of mono-and polymetallic palladium complexes containing the 2-pyridyl-1,2,3-triazole ligand or nonabranch-derived ligands has also been carried out, and their catalytic properties in coupling reactions has been studied

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