Tesis sobre el tema "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.
Texto completoMartin, Christopher Paul. "Pattern formation in self-organised nanoparticle assemblies". Thesis, University of Nottingham, 2007. http://eprints.nottingham.ac.uk/10772/.
Texto completoWang, Haolan. "Nanoparticle formation through the liquid arc method". Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.613366.
Texto completoHaubold, Danny, Annett Reichhelm, Alexander Weiz, Lars Borchardt, Christoph Ziegler, Lydia Bahrig, Stefan Kaskel, Michael Ruck y 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.
Texto completoVanella, Andrea. "Nanoparticle formation in nanoporous structures and applications". Doctoral thesis, Università di Siena, 2022. http://hdl.handle.net/11365/1210313.
Texto completoVoloshko, Andrey. "Nanoparticle formation by means of spark discharge at atmospheric pressure". Thesis, Saint-Etienne, 2015. http://www.theses.fr/2015STET4011/document.
Texto completoDuring 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
Huo, Zhijie. "Modelling of Soot Nanoparticle Formation in Turbulent Flames". Thesis, The University of Sydney, 2020. https://hdl.handle.net/2123/24858.
Texto completoTobler, Dominique Jeanette. "Molecular pathways of silica nanoparticle formation and biosilicification". Thesis, University of Leeds, 2008. http://etheses.whiterose.ac.uk/359/.
Texto completoLin, Jiashu. "La formation et le transport des particules dans le plasma froid". Thesis, Orléans, 2020. http://www.theses.fr/2020ORLE3029.
Texto completoThis 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
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.
Texto completoNanoparticles 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
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.
Texto completoMiclea, 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.
Texto completoSong, Delong. "Starch crosslinking for cellulose fiber modification and starch nanoparticle formation". Diss., Georgia Institute of Technology, 2011. http://hdl.handle.net/1853/39524.
Texto completoVancea, Ioan. "Pattern formation in nanoparticle suspensions : a Kinetic Monte Carlo approach". Thesis, Loughborough University, 2011. https://dspace.lboro.ac.uk/2134/8420.
Texto completoMendoza, 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.
Texto completoAkroyd, 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.
Texto completoAltman, Igor y 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.
Texto completoUdoh, Christiana. "Formation of polymer-nanoparticle capsules with tuneable morphologies by solvent extraction". Thesis, Imperial College London, 2018. http://hdl.handle.net/10044/1/59753.
Texto completoYaacob, 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.
Texto completoAltman, Igor. "Peculiarities of Nanoparticle Formation and Implications to Generation of Environmental Aerosols". Thesis, Griffith University, 2005. http://hdl.handle.net/10072/366347.
Texto completoThesis (PhD Doctorate)
Doctor of Philosophy (PhD)
School of Environmental Engineering
Full Text
Faivre, Damien. "Biological and biomimetic formation and organization of magnetic nanoparticles". Thesis, Universität Potsdam, 2014. http://opus.kobv.de/ubp/volltexte/2014/7202/.
Texto completoBiologische 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.
Chittipotula, Thirumalesha [Verfasser] y 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.
Texto completoMenéndez-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.
Texto completoJenei, 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.
Texto completoVITALI, 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.
Texto completoIn 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, acasein, Sic1 and asynuclein, 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.
Souva, Matthew Scott. "High Throughput Block Copolymer Nanoparticle Assembly Methods". The Ohio State University, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=osu1503101272745765.
Texto completoZhang, 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.
Texto completoSchneider, 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.
Texto completoMendoza, 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.
Texto completoSchneider, 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.
Texto completoRothfuß, Hannah [Verfasser] y 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.
Texto completoIzuhara, 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.
Texto completoLohse, 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.
Texto completoApplications 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
Committee in charge: Victoria De Rose Chairperson; James E. Hutchison, Advisor; Catherine Page, Member; Darren W. Johnson, Member; Miriam Deutsch, Outside Member
Paskevicius, Mark. "A nanostructural investigation of mechanochemically synthesised hydrogen storage materials". Thesis, Curtin University, 2009. http://hdl.handle.net/20.500.11937/254.
Texto completoMcKenzie, 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.
Texto completoGovender, 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.
Texto completoRedkov, A. V., A. A. Lipovskii y 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.
Texto completoZimmermann, M. y 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.
Texto completoCouëdel, 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.
Texto completoIncludes 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.
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.
Texto completoCouedel, 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.
Texto completoComplex (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.
Mothiba, Maborwa Tebogo. "The effects of clofazimine on mycobacterium smegmatis biofilm formation". Diss., University of Pretoria, 2013. http://hdl.handle.net/2263/31569.
Texto completoDissertation (MSc)--University of Pretoria, 2013.
Immunology
Unrestricted
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.
Texto completoThe 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
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.
Texto completoTexto em português e inglês
Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia de Alimentos
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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
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.
Texto completoAhmed, 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.
Texto completoPh.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
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.
Texto completoFlegg, 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.
Texto completoDichiara, 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.
Texto completoWang, 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.
Texto completoCatalysts 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