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Zhao, Hongxia. "Studies of thermal, mechanical and fracture behaviors of rigid nanoparticulates filled polymeric composites /." access full-text access abstract and table of contents, 2005. http://libweb.cityu.edu.hk/cgi-bin/ezdb/thesis.pl?phd-ap-b19887589a.pdf.
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Thesis (Ph.D.)--City University of Hong Kong, 2005."Submitted to Department of Physics and Materials Science in partial fulfillment of the requirements for the degree of Doctor of Philosophy" Includes bibliographical references.
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Luechau, Frank. "Process considerations for the recovery of bio-nanoparticulates in polymer-salt aqueous two-phase systems." Thesis, University of Birmingham, 2002. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.289385.
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Wen, William Y. "Development of New Characterisation Methods to Study the Photocatalysis Processes at Nanoparticulate TiO2 Film Electrodes." Thesis, Griffith University, 2011. http://hdl.handle.net/10072/366132.
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Titanium dioxide, TiO2, has a wide range of applications as a photocatalyst in the field of solar energy conversion and environmental remediation including water purification and wastewater treatment. In general, a TiO2 photocatalytic process consists of three major steps, namely, the mass transfer process in solution, the interfacial step, and the photoelectron transport inside the catalyst. This work explores the characterisation of TiO2 photocatalysis using a photoelectrochemical method to focus on each fundamental reaction steps. Each of these steps will be used to gain an accurate understanding of processes and identify possible improvements of the overall performance of TiO2 semiconductor photocatalysts. In this work, nano-sized TiO2 semiconductor photocatalysts were prepared by the solgel method, and immobilised onto a conducting ITO glass substrate to form a photoanode. Photocatalytic studies utilising immobilised TiO2 thin films have many advantages over the suspension/slurry system, including the elimination of the separation process. Most importantly however, photocatalysis by immobilised TiO2 photocatalyst can be manipulated by applying an external potential bias to focus on understanding certain aspects of the photocatalytic process (e.g. the rate determining steps).Thesis (PhD Doctorate)
Doctor of Philosophy (PhD)
Griffith School of Environment
Science, Environment, Engineering and Technology
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Huang, Shanshan. "Nanoparticulate nickel sulfide." Thesis, Cardiff University, 2008. http://orca.cf.ac.uk/54754/.
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Nickel sulfide possesses a variety of typical structures and stoichiometries that distinguish itself from iron sulfide and exhibits unique roles in the prebiotic reactions which are proposed to be involved in the origin of life. Nickel sulfide precipitate is hydrated and nanocrystalline, modelled as a 4 nm sphere with a 1 nm crystalline and anhydrous NiS (millerite) core, surrounded by a hydrated and defective mantle phase. It is a metastable but fairly robust structural configuration. It may be formulated as NiSxFbOx approximates to 1.5 and decreases on heating. The fresh nanoparticulate nickel sulfide precipitates undergo structural transformation from the initial millerite-like NiS to the more crystalline polydymite-like Ni3S4. This reaction is accompanied by the formation of a less crystalline Ni3S2 (heazlewoodite) phase. The reaction, happening in ambient conditions, occurs more readily for the solids precipitated from acidic environments (i.e., pH 3) and may be facilitated by the hydrogen and water bonding contained in this material. The performance of nickel sulfide and iron sulfide precipitates is investigated in the formaldehyde world under ambient and sulfidic environments which mimic the ambient ancient Earth environments to some extent. The catalytic capacity of the metal sulfides is not obvious in these experiments. An interesting finding is that, trithiane, the cyclic (SCH2)3, also suppresses the pyrite formation and thus promotes the greigite formation in the reaction between FeS and H2S. This provides another cause for the greigite formation in the Earth sedimentary systems and adds information to the origin-of-life theory in the iron sulfur world. Voltammetry experiments reveal that the nickel-cysteine complex lowers the overpotential for molecular H2 evolution in sea water to -1.53 V under ambient conditions. This catalytic property of the abiotic nickel-cysteine complex apparently mimics the Ni-S core in some hydrogenase enzymes functioning in physiological conditions. This bridges the abiotic and biotic worlds and supports the idea that life originated in the prebiotic ancient ocean.
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Keating, Siobhan. "Nanoparticulate delivery systems for 5-fluorouracil." Thesis, Queen's University Belfast, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343028.
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Govender, Thirumala. "Enhancing drug incorporation into nanoparticulate systems." Thesis, University of Nottingham, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299551.
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Smugowski, Hubert Jakub. "Magnetic nanoparticulate catalysts in flow processes." Thesis, University of Bath, 2011. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.548956.
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Abass, Sara Abdelazeem Hassan. "Electronic properties of printed nanoparticulate silicon." Master's thesis, University of Cape Town, 2011. http://hdl.handle.net/11427/10027.
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Printed silicon is an award-winning technology in the development of a large area of flexible electronics. In an investigation of the fundamental properties of printed nanoparticulate silicon composites, layers were screen printed and successfully characterised to establish their electrical performance using a Hall Measurement System (HMS). To explore properties of the nanoparticulate silicon composite a magnetoconductivity tensor model was developed and applied to extract parameters governing the electrical properties of the material. All the layers showed at least two carrier types. The effect of particle loading and temperature on the electrical properties was also investigated. Although carrier concentrations are generally low, their mobility was found to be comparable to, or even better than, similar classes of semiconductor materials.
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Kramberger, Iris. "Organic/inorganic hybrid nanoparticulate resonant contrast agents." Thesis, University of Oxford, 2016. https://ora.ox.ac.uk/objects/uuid:a1af88c4-493b-45b0-b98c-5de9e09bdae1.
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An intriguing frontier for magnetic resonance imaging (MRI) is the development of responsive Gd3+-based contrast agents (CAs) that can report physiological variations in the tissue microenvironment.[1] Heterogeneous biological milieu and quantification of the CA concentration at the site of interest are the major limitations of responsive concentration-dependent protic MRI probes. A ratiometric approach based on dualmode CAs containing a 19F MRI reporter, in addition to a paramagnetic moiety, is one of the feasible strategies to overcome this drawback. Since high fluorine content is required for in vivo imaging, nanoparticles offer advantageous characteristics over molecular probes due to their large surface area and size, allowing the incorporation of high concentrations of uorinated probes and paramagnetic CAs. For emerging applications of Gd3+ complexes at ultra-high magnetic fields, it was found that not only octadentate (q = 1), but also highly kinetically stable nonadentate (q = 0) Gd3+-DOTA systems can be incorporated into the mesopores of silica nanoparticles, resulting in an 8-fold increase in proton longitudinal relaxivity from 0.7 mM-1 s-1 to 6.2 mM-1 s-1 at 4.7 T compared to their molecular counterparts. A further 7-fold increase in longitudinal relaxivity was achieved when the silica surface of such particles was functionalised with highly acidic propyl sulphonates, enabling faster proton transfer through a hydrogen-bonded hydronium network. pH responsiveness of Gd3+ complexes tethered to particles has, on the other hand, been achieved through either local mobility or water access regulated by pH-responsive polymers acting as gating valves on the mesopores. Moreover, symmetric 19F MRI CAs were accommodated within micron- and nanosized matrices comprised of polyelectrolytes, quaternary ammonium first generation dendrimers and centrifugable oil-containing silica nanocapsules. For these, the biggest challenge has been posed by restricted local mobility, which notably shortens transverse relaxation time and attenuates the 19F NMR signal. Finally, polymers based on uorinated quaternary ammonium, pH-sensitive and Gd3+-DOTA methacrylates were prepared, exhibiting a dual 19F/1H MRI contrast with reverse pH response.
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Gonfa, Girma Goro. "Hall effect in printed Nanoparticulate Silicon Networks." Doctoral thesis, University of Cape Town, 2010. http://hdl.handle.net/11427/6529.
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Silicon nanoparticles for the application of printed electronics were successfully synthesised and characterised. High energy milling has been proven to yield uncontaminated powder of median particle size 150 nm satisfying a lognormal distribution. Single crystalline P- and N-type silicon wafers, and metallurgical grade silicon were used as starting materials. The structural characterisation of all milled powders using X-ray diffraction (XRD), Small Angle X-ray Scattering (SAXS) and electron diffraction proved that the silicon nanoparticles are polycrystalline with a crystallite size of about 40 nm. For the first time, we have formulated printable semiconducting inks from nanoparticulate silicon. Silicon nanoparticles were mixed with organic binders, such as linseed oil and acrylic, to produce printable inks. Similarly nanoparticulate silicon ink, doped with inorganic salts, which is a different procedure to conventional impurity doping of the silicon structure, was produced with linseed oil. A home-built Hall measurement system was used to characterise layers of doped ink, for which a complete carrier type reversal was observed. Based on the result of elemental mapping, two possible models were suggested to explain the doping effect. A state-of-the-art Hall measurement system was used to perform field dependent analysis of screen printed silicon inks in van der Pauw geometry. A magnetoconductivity tensor model was developed to extract the carrier properties. All the layers were demonstrated to have at least two carrier types. Inks produced from P-type silicon maintained their carrier type, but reversal was observed for the N-type layers. The mobility of the carriers is better or comparable to similar classes of semiconducting materials. 2 More information on the interparticle connections were obtained from IV and impedance spectroscopy measurements which demonstrated the capacitive effects present in the printed layers. The capacitors originate at the interfaces between the metal and the layers and between the particles.
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Bilton, Matthew William. "Nanoparticulate hydroxyapatite and calcium-based CO2 sorbents." Thesis, University of Leeds, 2012. http://etheses.whiterose.ac.uk/3847/.
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This thesis is focused on the development of synthesis and characterisation protocols for two different nanoparticulate materials; hydroxyapatite (HA), a biomaterial well recognised as chemically akin to human bone, and CaO, a material often used for the sequestration of CO2 at elevated temperatures. For the analysis of these materials various bulk and particle level characterisation techniques have been employed, which are complemented by the versatile analytical methods available in the transmission electron microscope (TEM). The first chapter of results reveal that a hydrothermal synthesis route achieved phase-pure nanoparticulate HA with Ca/P atomic ratios close to the stoichiometric target (1.67). Impure HA nanopowders were produced by a sol-gel synthesis route with analysis by X-ray diffraction (XRD) revealing secondary phases of calcium phosphates, CaCO3 and CaO. The Ca/P ratios of each powder were determined at the particle level using TEM with energy dispersive X-ray spectroscopy (TEM-EDX), having first established a threshold electron fluence below which significant electron-beam-induced alteration of the composition of HA does not occur. Results showed a greater variability of particle composition from the sol-gel preparation route compared to the hydrothermal route. This technique provides results in reasonable agreement to bulk Ca/P ratio analysis carried out by X-ray fluorescence (XRF) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS). The second component of the thesis relates to the production of nanoparticulate CaO powder sorbents for the sequestration of CO2 gas. The CaO nanopowders were produced by the thermal decomposition of calcium acetate hydrate (CaAc); this process was analysed by thermogravimetric analysis (TGA) and by in-situ hot-stage XRD. The CO2 uptake capability of the CaO powder sorbents was analysed by TGA following the reaction: CaO + CO2 ↔ CaCO3 Results showed a molar conversion ratio, χ (of CaO to CaCO3) of 0.92, after 15 minutes of carbonation with structural analysis by SEM and TEM showing consistent growth and densification of rounded CaCO3 crystals upon carbonation. Multiple cycles of carbonation and decarbonation were then carried out by TGA to investigate sorbent regenerability. A 0.32 decrease in χ was found after 9 cycles which is attributed to the sintering (reduction in surface area) of the sorbent with progressive decarbonations at 800 °C. Structural analysis of decarbonated samples extracted from the TGA, by XRD, SEM and TEM, highlighted the issue of sorbent hydration upon storage, sample preparation and analysis. A TEM based technique has been developed for the structural analysis of multicycle CO2 capture using an ex-situ environmental cell (E-cell). This technique allows for multicycle capture to be carried out and then analysed in the TEM with minimal exposure to the atmosphere, therefore providing a closer microstructural match to what occurs in the TGA. Results showed that slow, low-vacuum decarbonation (in the E-cell) creates a densified ‘skeleton’ of CaO, consistent with the drop in capture capacity observed by TGA. Finally, modifications of CaO sorbents using spacer materials has been carried out with the aim of declining the decay in sorbent performance during multiple cycles of carbonation and decarbonation in the TGA. Promising results were found using CaO sorbents modified a commercial YSZ powder and also with CaZrO3/ZrO2.
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Monteiro, Vitor Augusto de Rego. "Nanoparticulas de polifosfato de aluminio." [s.n.], 1998. http://repositorio.unicamp.br/jspui/handle/REPOSIP/250300.
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Orientador: Fernando GalembeckDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Sistemas coloidais de polifosfatos metálicos (M3+) são versáteis fontes de novos materiais. Nos últimos anos, nesse laboratório, foram obtidos sóis, géis, espumas e partículas ocas. Os polifosfatos de metais são obtidos pela precipitação em meio aquoso, formando sistemas bifásicos, dos quais os diferentes materiais são obtidos de acordo com as condições experimentais usadas na sua preparação e processamento. As suspensões aquosas de partículas amorfas de polifosfato de alumínio (PfAI) foram preparadas em diferentes composições (3 ?: P/AI ?: 0.4) a partir das soluções aquosas de sulfato de alumínio, polifosfato de sódio e hidróxido de amônio em uma larga faixa de concentrações. A mistura dos três reagentes foi agitada à temperatura ambiente formando uma polidispersão estável. Cada amostra foi centrifugada e a medida de diâmetro efetivo das partículas do sobrenadante revelou valores entre 120 e 200 nm. A análise dos histogramas segundo uma distribuição multimodal ajustada à função de autocorrelação revelou a presença de partículas da ordem de 1 O nm e outras ainda menores. Em excesso de polifosfato (P/AI :? 4.5), o número de partículas obtido é menor, ao passo que em excesso de alumínio o diâmetro efetivo das partículas aumentou. As micrografias eletrônicas de transmissão (MET) mostraram partículas pequenas isoladas e agregados de nanopartículas formados durante a secagem provavelmente por agregação das nanopartículas por adesão capilar. O diâmetro das partículas secas, observadas por MET, está na faixa de 2 a 16 nm. As características dos colóides de polifosfatos permitem traçar o seguinte modelo: a associação de íons polivalente hidratados em solução aquosa forma redes poliônicas com alto grau de hidratação. Essa nova fase é formada quando um tamanho crítico das redes é atingido em função de um número crítico de associações entre os íons. A tensão interfacial desse sistema é baixa porque ela depende fortemente da composição das fases. Baixos valores de tensão interfacial permitem a formação e estabilização de nanopartículas
Abstract: M3+ polyphosphates colloidal systems are versatile sources of new materiais. ln recent years we have demonstrated the formation of sois, gels, foams and hollow particles, by using these salts. They are formed by precipitation in aqueous media; this phase separation yields different products, depending on the actual conditions used. Particles of noncrystalline aluminum polyphosphate (AI PP) of many different compositions (3 ? P/AI ; ? 0.4) are prepared from aqueous solutions of aluminum sulphate, sodium polyphosphate and ammonium hydroxide within a broad concentration range. The admixture of dilute aqueous solutions of the parent reagents, under strong stirring and at a room temperatura yields stable aqueous dispersions of AIPP nanoparticles within 3 ; ? P/AI ;? 2 molar ratios. After centrifugation, the supernatants of these dispersions have an effective particle diameter ranging from 120 to 200 nm. However, the analysis of the autocorrelation function assuming a multimodal particle size distribution reveals the presence of a population of parti eles as small as 1 O nm. ln the presence of an excess of phosphate (P/AI ;? 4.5), the number of nanoparticles obtained is reduced while in the presence of an excess of aluminum the effective particle diameter is increased. The transmission electron micrographs of the particles show large regions with isolated nanoparticles and also aggregates, formed during sample drying probably by capillary adhesion and coalescence among particles. The diameters of isolated nanoparticles are in 2 - 16 nm range. Ali the features of the metal polyphosphates colloids are understood following this model: the strongly hydrated polyvalent ions associate in solution, forming polyionic network domains, with a high degree of hydration. The network domains separate as a new phase when a criticai size is reached, but the interfacial tension with the parent liquid is strongly dependent on the chemical composition. Very low interfacial tensions allow the formation of nanoparticles, depending on the extent of the networks and thus on the ionic concentration
Mestrado
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Buthelezi, Motlalepula Isaac. "Synthesis and properties of nanoparticulate titanium dioxide compounds." Thesis, University of the Western Cape, 2009. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_9038_1298632656.
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An electrolytic cell was designed and constructed for the preparation of TiO2 nanotubes. Conditions of anodic oxidation were established to reproducibly prepare TiO2 nanotubes of average length 35-50 &mu
m vertically orientated relative to the plain of a pure titanium metal sheet. A non-aqueous solution of ethylene glycol containing small percentage of ammonium fluoride was used as the electrolyte with an applied voltage of 60 V. The morphology and dimensions of the nanotube arrays were studied by scanning (SEM) and transmission (TEM) electron microscopy. The effect of calcination under different conditions of temperature and atmosphere (nitrogen, argon and air) were assessed by both X-ray diffraction (XRD) and cyclic voltammetry (CV). Cyclic voltammetry studies were made possible by construction of a specially designed titanium electrode upon which the nanotubes were prepared. CV studies established a positive correlation between crystallinity and conductivity of the nanotubes. Doping of the nanotubes with nitrogen and carbon was established by elemental analysis, X-ray photoelectron spectroscopy (XPS) and Rutherford back scattering (RBS). The effect of nonmetal doping on the band gap of the TiO2 nanotubes was investigated by diffuse reflectance spectroscopy (DRS).
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Mergler, Bianca Isolde. "Enterocyte uptake of nanoparticulate iron(III) oxo-hydroxide." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610413.
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Salvage, Jonathan Peter. "A novel phosphorylcholine-based nanoparticulate drug delivery system." Thesis, University of Brighton, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.499068.
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Phosphorylcholine (PC) based materials have been shown to have increased biocompatibility when compared to more established bio-implantable materials. This has been attributed to the ability of PC to mimic the cell lipid bilayer membrane, resulting in reduced protein adhesion and cellular interaction / activation. PC research has previously focused on the areas of contact lens formulation and medical device coating. This project sought to harness the biomimetic properties of PC to develop novel systems for drug delivery, with the emphasis being focused on microparticulate drug delivery.
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Solana, Oluwole David. "Production and characterisation of nanoparticulate silicon photovoltaic devices." Master's thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/9024.
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Includes bibliographical references (leaves 104-111).A first approach in fabricating electronically functional nanoparticulate silicon solar cells, by using low cost screen printing on paper substrates, has been developed. The semiconductor materials used consisted of n- and p-type silicon nanoparticles produced by means of high energy mechanical milling, as well as commercially sourced nanophase intrinsic silicon powder. Results from microscopy revealed that the nanoparticles had formed clusters that were capable of transporting charge through the device. Results from the electrical characterisation show that the printed devices exhibit electrical properties characteristic of silicon PV devices, confirming that the experimental process followed resulted in the successful production of a functional silicon solar cell. This thesis outlines the particle production process, ink formulation technique, and the device fabrication process. Results from the physical characterisation of the nanopowders and printed layers using optical and scanning electron microscopy, as well as an analysis of the electrical performance of the printed devices are also presented.
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Foston, Marcus Bernard. "Cyclic, tethered and nanoparticulate silicones for material modification." Diss., Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/24762.
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Thesis (Ph.D.)--Polymer, Textile and Fiber Engineering, Georgia Institute of Technology, 2009.Committee Chair: Dr. Haskell W. Beckham; Committee Member: Dr. Anselm Griffin; Committee Member: Dr. Johannes Leisen; Committee Member: Dr. Sankar Nair; Committee Member: Dr. Uwe Bunz.
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OLIVEIRA, Rodrigo José de. "Surfatantes fotorreativos para síntese de nanoparticulas." Universidade Federal de Pernambuco, 2012. https://repositorio.ufpe.br/handle/123456789/11857.
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CNPq CAPES RENAMI Merck-Southampton
Uma nova classe de surfatantes, chamados fotorreativos (PRS) é apresentada aqui. Estes são anfifilos que podem atuar como precursores em reações fotoquímicas para a síntese de nanopartículas metálicas e de óxidos. Nesta tese foram estudados os seguintes PRSs: 2- etilhexanoato de cobalto (II), Co(EH)2; 2-etilhexanoato de bismuto (III), Bi(EH)3; 2- etilhexanoato de ferro (III), Fe(EH)3 e o 2-etilhexanoato de Manganês (II), Mn(EH)2. As micelas invertidas destes PRSs foram estudadas por viscosidade e espalhamento de nêutrons a baixo ângulo, SANS. Foi verificado que, quando dispersos em hidrocarbonetos como o heptano, estes PRSs formam agregados pequenos com números de agregação entre 3 e 7. Da mesma forma, micelas invertidas mistas de PRS e aerosol-OT (AOT) foram estudadas por viscosimetria, condutividade e SANS. A adição do PRS no sistema misto em heptano não levou a consideráveis mudanças na estrutura micelar, mas em ciclohexano há um aumento na curvatura das micelas, fato atribuído à baixa penetração das moléculas do solvente no filme interfacial e ao efeito de blindagem das repulsões eletrostáticas entre os grupos polares. O efeito da quantidade de PRS em relação a AOT foi estudado por SANS, e observou-se que o aumento da curvatura está diretamente ligada à valência do contra-íon do PRS. Nestes sistemas, a excitação da banda de transferência de carga metal-ligante, LMCT, leva a uma transferência de elétrons do PRS para seu respectivo contra-íon, promovendo a geração de nanopartículas metálicas e de óxidos metálicos nas micelas invertidas. Neste trabalho, é apresentada a prova do conceito do uso de PRS como precursor na síntese fotoquímica de nanopartículas inorgânicas aproximadamente monodispersas. Foram obtidas nanopartículas de Co3O4 e Bi em altas concentrações (10-2 M) pela irradiação das micelas invertidas com luz UV sem a presença de agentes redox ou outras moléculas. O método também se mostrou eficaz para a síntese de óxido de ferro, óxido de cério e óxido de manganês. Estes resultados demonstram que estes sistemas são uma nova abordagem na síntese de nanomateriais em sistemas auto-ordenados fotossensíveis, representando uma rota limpa, direta e simples para síntese de materiais.
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Figueiredo, Leandro Carlos. "Sistemas magnéticos nanoparticulados à base de maghemita." reponame:Repositório Institucional da UnB, 2009. http://repositorio.unb.br/handle/10482/4868.
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Este trabalho apresenta a investigação das propriedades magnéticas de fluido magnético iônico contendo nanopartícula de maghemita ( -Fe2O3). Ademais, apresenta a investigação das propriedades magnéticas do sistema constituído de nanocápsulas de albumina contendo nanopartículas de maghemita, inseridas na matriz polimérica via o fluido magnético iônico. As técnicas utilizadas para a investigação foram técnicas de ressonância magnética eletrônica, magnetização e birrefringência magnética estática. Primeiramente, foram estudadas as características estruturais das nanopartículas de maghemita utilizando-se técnicas de difração de raios-X e microscopia eletrônica de transmissão. As nanopartículas (nanocápsulas) magnéticas apresentam diâmetro médio e dispersão em diâmetro de 8,15 nm e 0,30 (73 nm e 0,37), respectivamente. Os dados de ressonância magnética foram tratados considerando que partículas com diâmetros levemente maiores que a média apresentam absorção ressonante em campo inferior ao máximo de absorção. Por outro lado, partículas menores apresentam absorção em campo superior. Considerando as características da variação da largura de linha de ressonância com a temperatura e com a orientação da amostra congelada (dependência angular), verifica-se que as partículas menores são as que sofrem maior influência decorrente do efeito das interações. A magnetização foi estudada para o sistema de nanocápsulas magnéticas considerando a implementação de um modelo de barreira de energia que inclui termos para descrever os fenômenos de interação entre as partículas. Os resultados sugerem que as interações entre as partículas são responsáveis pelas variações no perfil das curvas de histerese obtidas em diferentes temperaturas. Uma assinatura relacionada à susceptibilidade magnética da amostra em função da temperatura foi observada na evolução do perfil das interações. Verifica-se, ainda, que a implementação do modelo se aplica a outros sistemas de nanopartículas magnéticas. Por fim, os resultados de birrefringência magnética estática foram analisados considerando os mesmos argumentos utilizados no modelo de avaliação dos dados de magnetização. Valores da concentração de partículas e frações de agregados que contribuem para a birrefringência foram calculados. __________________________________________________________________________________________ ABSTRACT
This work presents the investigation of magnetic properties of an ionic magnetic fluid containing maghemite (y-Fe2O3) nanoparticles. Moreover, this work presents the investigation of the magnetic properties of the system consisting of albumin nanocapsules containing maghemite nanoparticles embedded in the polymer matrix via the ionic magnetic uid. The techniques used in our investigation were magnetic resonance, magnetization and static magnetic birefringence. Firstly, we investigated the structural characteristics of the maghemite nanoparticles using X-ray di raction and transmission electron microscopy. Nanoparticles and (nanocapsules) were found to present average diameter and diameter dispersion of 8.15 nm and 0.29 (73 nm and 0.37), respectively. The magnetic resonance data were analyzed considering that particles with a diameter slightly larger than the average size present resonant absorption eld smaller than the eld for maximum absorption. On the other hand, smaller particles present resonant absorption at elds above the eld for maximum absorption. Given the characteristics of both the temperature dependence of the resonance linewidth and the resonance parameters of eld-frozen samples (angular dependence measurements) it appears that smaller particles are subjected to stronger in uence due to the e ect of particle-particle interaction. The magnetization data of magnetic nanocapsules were analyzed considering an energy barrier model including terms to describe the interaction among the supported magnetic particles. The results suggest that interactions between particles are responsible for changes in the pro le of hysteresis curves at di erent temperatures. A signature related to the particle interaction was observed in the temperature dependence of the magnetic susceptibility. We found, in addition, that the model used to analyze our magnetization data applies to other systems containing magnetic nanoparticles. Finally, the static magnetic birefringence data were analyzed considering the same arguments used in the analysis of the magnetization data. Values of particles concentration and fractions of aggregates contributing to the birefringence signal were determined.
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Singh, Pankaj Kumar. "Dispersion of nanoparticulate suspensions using self-assembled surfactant aggregates." [Gainesville, Fla.] : University of Florida, 2002. http://purl.fcla.edu/fcla/etd/UFE1001182.
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Convery, Joanne Marie. "Analysis of nanoparticulate coatings with relevance to dentine sensitivity." Thesis, University of Liverpool, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.501564.
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Dentine sensitivity is a common dental complaint. It is caused by the exposure of root dentine to the oral environment. A popular method of overcoming dentine sensitivity is the occlusion of the dentinal tubules. In this thesis the use of nanoparticulate silica sols, of sizes 7, 14 and 21 nm diameter for the treatment of dentine sensitivity, as occluding agents was explored. Previous work at the University of Liverpool has identified a simple two step method for coating surfaces in silica nanoparticles. This process required the use of a poly cationic polymer (Zetag 7689). TEM and QCM-D were used to observe the creation of nanoparticulate coatings, in the absence and following manipulation of the polymer binding layer. It was demonstrated that on gold, carbon and hydroxyapatite surfaces a polymer binding layer was required. However, using the QCM-D and XPS it was identified that on dentine surfaces a polymer binding layer was unnecessary.
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Palgrave, Robert. "Chemical vapour deposition of nanoparticulate and nanocomposite thin films." Thesis, University College London (University of London), 2007. http://discovery.ucl.ac.uk/1444997/.
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Gold nanoparticle and gold / semiconductor nanocomposite thin films have been deposited using aerosol assisted chemical vapour deposition. Two gold precursors have been investigated which would be unsuitable for use with conventional atmospheric pressure chemical vapour deposition. HAuCU was used in methanol solution to deposit films at substrate temperatures of 350 - 500 °C. Powder X-ray diffraction and X-ray photoelectron spectroscopy revealed that these films consisted of metallic gold. The optical properties of these films corresponded to nanoscale gold particles, specifically displaying surface plasmon resonance (SPR) absorption. The wavelength of the SPR absorption maximum varied with precursor concentration and substrate temperature from 1000 - 600 nm. Scanning electron microscopy revealed particles a wide variety of sizes and shapes, as well as regions of island growth morphology. Depositions carried out from solutions of HAuCU and a range of quaternary ammonium ion surfactants led to films of particles with narrow size distributions. The use of tetraoctylammonium bromide (TOAB) led to films of spherical particles, the mean diameter of which could be altered by changing HAuCU : TOAB ratio, deposition temperature and solvent volume. Films with mean particle diameters ranging from 65 nm to 120 nm and arithmetic standard deviations of less than 20% of the mean could be deposited in this way. Toluene solutions of pre-formed gold particles were used to deposit films. These films showed similar optical properties to the original precursor solution. Nanocomposite films were deposited by combining HAuCU or pre-formed gold particles with a conventional CVD precursor in a single precursor solution. W(CO)6 , Mo(CO)6 , W(OPh)6 , TiPrU were combined with a gold precursor to deposit metal oxide films with incorporated gold particles. The concentration of gold within the films could be varied by changing the precursor ratios. These films showed SPR peaks that were redshifted compared to gold particles alone.
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Kroner, Anna Barbara. "Effect of ceria and zirconia on nanoparticulate rhodium catalysts." Thesis, University of Southampton, 2009. https://eprints.soton.ac.uk/67241/.
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Rh metal was implemented as a core component in the so-called three-way automotive exhaust catalyst (TWC) due to its excellent properties such as thermal stability, poison resistance and inert behaviour to react with any support materials. These catalysts are often loaded with small amount of promoter elements such as Ce and Zr that enhance their overall catalytic performances and catalyst lifetime. It is therefore desirable to develop new CeOx-based catalyst with both high redox activity and high thermal resistance. Samples of two surface coverages of rhodium on a non-porous high area alumina been synthesised; at 1.6 Rh and 4 wt % Rh loading. Ceria and zirconia have been deposited on the pre-supported Rh catalysts by the controlled surface reaction between the reduced Rh surface and an organometallic precursors: Zr(acac)4 and Ce(acac)3, with different cerium : zirconium ratios: Ce:Zr;1:0, 1:1, 2:1, 0:1. Ceriated Rh catalysts have been also prepared by a different synthesis method, wherein the ceria was deposited on γ-Al2O3 and subsequently Rh metal was added. A series of Rh catalysts produced has been characterised ex situ by BET surface area measurement, TEM, STEM HAADF, EDX, XPS, and XAFS. The combination of Diffuse Reflectance Infrared Fourier Transform Spectroscopy (DRIFTS), Mass Spectrometry (MS) and Energy Dispersive X-ray Absorption Fine Structure (EDE) techniques in a synchronous, time-resolved manner has been applied to determine the complementary information about structural and kinetic changes of the chemical system throughout CO exposure and two catalytic processes: CO oxidation and the reduction of NO by CO in the temperature range between 298 K to 573 K. It has been shown that advanced characterisation techniques, used in the time-resolved, in situ manner were needed in order to understand the behaviour of these complex catalytic systems under operating conditions. The effects of the catalysts’ composition, temperature and pulsed gas flow on catalyst performance have been effectively mapped by the combined DRIFTS/MS/EDE studies. The synthesis procedure has been found to be crucial to achieve the desired interaction between CeOx and Rh particles. No enhancement of ceriated Rh catalysts was observed when ceria was deposited directly on γ-Al2O3 (method I). The addition of each promoter element by the controlled surface modification procedure (method II) exhibits multiple effects on the catalysts performance. The DRIFTS/XAFS studies have confirmed that CeOx and ZrO2 facilitate the protection of Rh particles against extensive oxidation in atmospheres of air, O2 and CO. Larger Rh core particles of ceriated and zirconiated Rh catalysts have been observed when compared with undoped Rh samples. DRIFTS results indicate that by interaction of CO with Rh particles a significantly larger amount of linear CO species was formed on the ceriated Rh surface than in the non-ceriated Rh catalysts case suggesting the presence of predominant metallic Rh phase for that system. Moreover, only ceria doping was found to improve the catalytic activity of promoted Rh catalysts throughout CO oxidation in the temperature ramp mode under different (O2/CO) gas composition.
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Balbinot, Carlos Eduardo Agostini. "Avaliação de propriedades mecânicas de resinas compostas nanoparticuladas." Pontifícia Universidade Católica do Rio Grande do Sul, 2006. http://hdl.handle.net/10923/482.
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license.txt: 581 bytes, checksum: 44ea52f0b7567232681c6e3d72285adc (MD5)The purpose of this study was evaluate selected mechanical properties (compressive strength, diametral tensile strength, flexural strength e flexural moduli) of four differents nanofilled composite and a microhybrid composite, in dentin e enamel A2 shades. Were maded ten samples for each group of each test. The flexural moduli was calculated by the results of the flexural strength`s test. The results were compared statistically with ANOVA e Tukey (p<0,01). There was no statistical difference for compressive strength, with values that range into 141. 04 MPa for 4 Seasons A2E and 206. 08 MPa Grandio A2O. For flexural strength, there was statistical difference for the tested groups, and the values range into 59. 16 MPa for 4 Seasons A2E and 122 MPa for Supreme XT A2E. There was statistical difference for flexural moduli and in this test the values range between 3. 4 GPa for 4 Seasons A2E and 13. 30 GPa for Grandio A2O. For diametral tensile strength, Esthet-X A2O showed value (34. 87 MPa) statiscally lower than the others groups, and Supreme XT A2E (50. 26 MPa), statiscally higher than the others tested groups; between the others groups there was no statistical difference. Even with differences for the values between the tested groups for flexural strength, flexural moduli and diametral tensile strength, the nanofiller composites, based in the results of this study, present mechanical properties similar from microhibrid resin.
Este estudo teve como objetivo avaliar as propriedades mecânicas selecionadas (resistência à compressão, resistência à tração diametral, resistência flexural de trêspontos e módulo flexural) de quatro marcas diferentes de resina composta nanoparticuladas e uma resina composta microhíbrida, nas cores A2 esmalte e dentina. Foram confeccionadas dez amostras para cada grupo de cada teste. O módulo flexural foi calculado a partir dos resultados do teste de resistência flexural. Os resultados obtidos nos ensaios foram comparados estatisticamente com análise de variância e teste de Tukey (p < 0,01). Não houve diferença estatisticamente significante para os grupos testados no teste de resistência à compressão, sendo que as médias variaram entre 141,04 MPa para a resina 4 Seasons A2E e 206,08 MPa para a resina Grandio A2O. No teste de resistência flexural, houve diferença estatisticamente significativa entre os grupos, onde as medias variaram entre 59,16 MPa para a resina 4 Seasons A2E e 122 MPa para a resina Supreme XT A2E. Houve diferença estatisticamente significante para módulo flexural e neste teste as médias variaram entre 3,4 GPa para a resina 4 Seasons A2E e 13,30 GPa para a resina Grandio A2O. No teste de resistência à tração diametral, a resina Esthet-X A2O apresentou média (34,87 MPa) estatisticamente menor que os demais grupos, e a resina Supreme XT A2E (50,26 MPa), estatisticamente maior que os demais grupos testados; entre os demais grupos não houve diferença estatisticamente significante. Apesar de diferenças nos valores entre os grupos testados nos testes de resistência flexural, módulo flexural e resistência à tração diametral, as resinas nanoparticuladas, baseados nos resultados obtidos neste estudo, apresentam propriedades mecânicas semelhantes da resina microhíbrida.
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Costa, Inês Henriques da Silva e. "Nanotoxicologia: métodos para avaliação do perfil toxicológico de sistemas nanoparticulares." Master's thesis, [s.n.], 2013. http://hdl.handle.net/10284/4085.
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Projeto de Pós-Graduação/Dissertação apresentado à Universidade Fernando Pessoa como parte dos requisitos para obtenção do grau de Mestre em Ciências FarmacêuticasA nanotecnologia é uma ciência promissora em diversas áreas, incluindo a indústria farmacêutica, na qual o seu principal objetivo é o desenvolvimento de novas terapias. As nanopartículas lipídicas sólidas (SLN) foram desenvolvidas com o objetivo de ultrapassar os limites dos sistemas coloidais tradicionais como lipossomas, emulsões e as nanopartículas poliméricas. São partículas com tamanhos inferiores ao mícron, entre 50-1000nm, constituídas por lípidos fisiológicos, biodegradáveis, e biocompatíveis, que se mantêm sólidos à temperatura corporal e ambiente. Neste projeto é abordada a nanotecnologia associada a estas partículas, como os excipientes utilizados, os métodos de produção, as suas principais aplicações e a sua toxicidade. Apesar destas nanopartículas apresentarem todos os pré-requisitos para serem considerados sistemas de transporte seguros, sendo esperada baixa ou até nenhuma toxicidade, a sua utilização médica requer mais evidência sobre a sua segurança. A maioria dos dados disponíveis na literatura sobre o comportamento destas partículas in vitro parece confirma-la, mas alguns resultados discordantes também já foram apresentados. O stress oxidativo é um dos danos mais largamente associados às nanopartículas, mas nas SLN este efeito não tem tido amplamente estudado. Os poucos estudos realizados revelam resultados contraditórios, o que nos incentivou a averiguar a possível indução de stress oxidativo por uma série de cSLN em HepG2, uma linha celular do carcinoma hepatocelular. Averiguámos a geração de espécies reativas de oxigénio (ROS) e a alteração na atividade dos sistemas antioxidantes enzimáticos após exposição às cSLN. O ensaio de DCFH-DA revelou um enorme aumento da presença ROS, a atividade da superóxido dismutase aumentou e a atividade da glutationa redutase diminuiu drasticamente (início de apoptose), o que nos indica que estas nanopartículas causam, realmente, stress oxidativo nesta linha celular. Em adição, investigámos se tal toxicidade é causada pelo lípido catiónico usado nas formulações em causa (brometo de cetiltrimetilamônio, CTAB). Os resultados direcionam-no como uma razão para tal toxicidade, mas não a única. Contudo, os nossos resultados foram contraditórios e mais investigação deve ser levada a cabo. Nanotechonology is a promising science in several fields, including the pharmaceutical industry, in which its main goal is to develop new therapeutics. Solid lipid nanoparticles (SLN) were developed to overcome the limits of traditional colloidal carriers such as liposomes, emulsions and polymeric nanoparticles. They are submicron particles with size in the range of 50-1000 nm and are composed of physiological, biodegradable and biocompatible lipids that remain solid at body and room temperature. In this thesis it is described the nanotechnology associated to SLN, materials used as excipients, methods of production, their main applications and their toxicology. Although these particles present all pre-requisites to be considered safe drug carries, being expected to present low or even none toxicity, their use in medicine requires more evidence of their safety. The available data on the in vitro behavior of these systems seem to confirm it, but some contradictory results have also been reported. Oxidative stress is one of the most reported damage associated to nanoparticles, but in SLN it has not been widely studied. The few performed studies have revealed some contradictory result, which led us to study the possibility of oxidative stress induction by a set of cSLN in HepG2, a human hepatocellular carcinoma cell line. We ascertained the generation of reactive oxygen species (ROS) and the alteration on antioxidant enzymes’ activity after exposure to the cSLN. DCFH-DA assay revealed great increase of ROS presence, the activity of superoxide dismutase was increased and the activity of gluthatione redutase was largely decreased (apoptosis initiation), indicating that these nanoparticles caused, indeed, oxidative stress in this cell line. In addition, we investigated if such toxicity is caused by the cationic lipid used in the formulations (cetyl trimethylammonium bromide, CTAB), our main suspect. The results direct it as one, but not the only, reason of such toxicity. Nevertheless, our results were contradictory and more investigations must be carried out.
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Smith, Bryan Ronain. "Nanoparticulate platforms for molecular imaging of atherosclerosis and breast cancer." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1150309580.
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Libor, Zsuzsanna. "Chemical synthesis of nanoparticles and electrohydrodynamic manipulation of nanoparticulate suspensions." Thesis, Cranfield University, 2009. http://dspace.lib.cranfield.ac.uk/handle/1826/4486.
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This research concerns the study of nanoparticle synthesis methods and the influence that nanoparticles can have on the physical and electrical properties of non-polar fluids. In this study it is demonstrated that a very small volume fraction of nanoparticles can have a very large effect on the macroscopic properties of fluids. Characterization of nanoparticles and nanofluids has led to the creation of new techniques for controlled deployment of nanoparticles within larger structures. A new dielectrophoretic technique can be used for (1) uniformly sized droplet generation and manipulation with controllable droplet size, (2) oil-in-water emulsion creation in unique way, (3) recycling nanoparticles from nanoparticulate suspensions and (4) creation of core-shell structures. Different types, sizes and morphologies of nanoparticles have been made successfully by chemical synthesis and new synthesis routes have been created. A new wet chemical route has been devised to synthesise nickel nanoparticles with controllable size and different morphology including new shapes such as micro-flower and nano-stars. PZT nanoparticles have been synthesized hydrothermally with controllable size and new morphologies created such as nearly spherical nanoparticles and pellets. A novel wet chemical synthesis method was developed to produce core-shell structures of Ni- and also Fe3O4 - coated SiO2, BT, and PZT particles. The characterization of non-polar fluid-based nanofluids included a sedimentation study, studies of the fluidic properties (viscosity and surface tension) and electrical properties such as DC conductivity and dielectric permittivity. The results clearly show that the macroscopic properties of base fluids (silicone oil and perfluorinated oil) were changed even with a very low concentration (< 0.6 vol %) of nanoparticles added. The properties of nanofluids are found to depend on the properties of the base fluid and also on the properties of the dispersed nanoparticles. Importantly, the properties are demonstrated to depend on the fluid-particle interaction.
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Sommer, Katherine. "Nanoparticulate copolymers for the encapsulation and release of bioactive molecules." Thesis, University of Reading, 2013. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.606942.
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Three nanoparticle systems were investigated for the nano-encapsulation and release of bioactive molecules. The first series of hydroxyethyl methacrylate-co-carboxyethyl acrylate random polymers were found, above their critical aggregation concentration (CAC), to self-assemble into spherical nanoparticles which dissociated when the external pH rose above 4. The second and third series were core:shell microgels, crosslinked with ethylene glycol dimethacrylate (EGDMA), made from a core composed of hydroxyethyl methacrylate (HEMA) and a carboxyethyl acrylate (CEA) shell which underwent volume transitions when the external solution was raised above pH 4. These nanoparticle systems were investigated using proton NMR, zeta-potential, dynamic light scattering (DLS), potentiometric titrations, gel permeation chromatography (GPC) and turbidity studies. The shape, morphology and core:shell architecture were imaged using transmission electron microscopy (TEM) staining with uranyl acetate and phosphotungstic acid (PTA), Cryo-TEM, scanning electron microscopy (SEM), cryo-SEM, confocal microscopy and optical microscopy. The micro gels were all shown to have good biocompatibility by slug mucosal tests. The uptake and release of three dyes; Rhodamine 6G, Coumarin 153, and 9-diethylamino-5-benzo[a]phenoxazinone (Nile red) were investigated. High uptake of the dye molecules was observed at pH 4 and high release at pH 7, with microgel particle separation from the aqueous solution being achieved by centrifugation. The micro gel systems were investigated for the uptake of the model pharmaceuticals paracetamol, caffeine, dopamine, ibuprofen, carbamazepine and riboflavin; all of which have been detected globally in drinking water supplies. The uptake of pharmaceuticals by the microgel systems was shown to be low at both pH 4 and pH 7. The low uptake was concluded to be caused by the carboxylic acids groups localised on the microgel surface creating a collapsed skin layer, so inhibiting the inward diffusion of additional drugs. The uptake and release experiments were performed using spectrofluorescence analysis and UV -visible spectrometry. All three nanoparticulate systems were filterable from aqueous media at low (15 psi) pressure using lab-cast polyethersulphone (PES) ultrafiltration membranes with a molecular weight cut off (MWCO) of 10kDa.
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Cousins, Brian G. "The effect of a nanoparticulate silica coating on cellular response." Thesis, University of Liverpool, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.420280.
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Emamzadeh, Mina. "Polymer-gold nanoparticulate formulations for combinational photochemotherapy of pancreatic cancer." Thesis, University College London (University of London), 2018. http://discovery.ucl.ac.uk/10059498/.
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Pancreatic cancer is one of the most deadly of all types of cancer, with a yearly incident that equals its mortality. Gemcitabine (Gem) is currently the first-line chemotherapeutic drug used to treat pancreatic cancer. The major deficiencies of Gem therapy are poor cell membrane permeability, short plasma half-life and toxic side effects. In order to improve the pharmacokinetic characteristics and overcome the obstacles to achieve effective drug delivery, a nanoparticulate drug delivery system can be utilised; gold nanoparticles (GNPs) have been investigated as carriers for drug delivery due to their appealing physicochemical and optical properties. This research project concerns the development of a new generation of GNPs for cancer treatment by co-delivering anti-cancer drugs in combination with laser-induced photothermal effects confined at the diseased areas. Gold nanoshells (GNShells) were synthesised with the capability to carry and deliver Gem and exert phototherapeutic properties. Protein repellent thiol capped poly (ethylene glycol) methyl ether methacrylate polymers were synthesised by RAFT polymerisation and used as efficient particle stabilising ligands. Significant stability enhancement was achieved allowing for the co-functionalisation of GNShells with Gem for applications in in vitro assays against pancreatic cancer cells. GNShells mediated strong photothermal effect owing to their strong surface plasmon absorption in the red/NIR region. This property was exploited to enhance the toxicity of Gem using laser light as the external stimulus. The concerted antitumor activity of Gem with the photothermal effect of the GNShells upon irradiation with a continuous wave laser, increase the cellular uptake and efficacy of Gem-loaded GNShells against MiaPaCa-2 cells. Therefore, the proposed nanoformulation might provide an active strategy for synergistic chemo-photothermal combined therapy.
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Benin, Bogdan Markovich. "Synthesis and Characterization of Novel Gold-Based Nanoparticulate Chemotherapeutic Agents." Kent State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1461088605.
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Murshidi, Julie Andrianny. "Hydrogen storage studies of nanoparticulate AI and TiMn based compounds." Thesis, Curtin University, 2012. http://hdl.handle.net/20.500.11937/175.
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Concerns about the impact that fossil fuels have on the environment and their increasing price to the consumer have led to research being undertaken to evaluate and refine other energy carriers that will be comparable to fossil fuels. Significant interest has been associated with hydrogen. Hydrogen is widely known as a promising energy carrier for the transportation sector. However at present no known material or storage means exists that satisfies all requirements to enable high-volume automotive application. Transition to using hydrogen storage technology in vehicles might first include its implementation in specialty vehicles, portable power supply and stationary power supply. Due to this fact, research into materials based hydrogen storage has grown significantly over the past decade. Of the wide variety of materials based hydrogen storage, three different materials were chosen as the primary focus of this project; (1) Aluminium nanoparticles, (2) AlH3 nanoparticles and (3) TiMn alloy.Al nanoparticles were synthesised by mechanochemical reactions of AlCl3 + 3Li → Al + 3LiCl using different LiCl:Al volume ratios (6.786:1 , 9.665:1 and 12.544:1). LiCl was used as the buffer. Sample synthesised without the addition of buffer led to the formation of Al nanoparticles with an average particle size of 50 nm. Addition of sufficient quantity of buffer resulted in the formation of Al with average particle sizes down to 13 nm. The addition of LiCl as a buffer helps to separate the synthesized Al particles, essentially restricting particle growth and promoting nanoparticle formation. Attempted hydrogenation of Al nanoparticles (13 nm) using a mixed H2/scCO2 media showed no H2 absorption. This indicates that an Al particle size less than (13 nm) is required to introduce hydrogen into pure Al at pressure and temperature attempt herein (73.8 bar and 31.1C). Furthermore the presence of oxide layer (Al2O3) on Al nanoparticles during scCO2/H2 reaction limited the rate of hydrogen permeation on Al nanoparticles.AlH3 nanoparticles were synthesised by mechanochemical reactions of the 3LiAlH4 + AlCl3 using different LiCl:AlH3 volume ratios (0.76:1, 2:1, 5:1 and 10:1) at 77 K. The addition of LiCl as a buffer leads to the reduction of the synthesized AlH3 crystallite size, restricting AlH3 decomposition and preventing high Al yields. Quantitative Rietveld results coupled with hydrogen desorption measurements suggest the presence of an amorphous AlH3 phase in mechanochemically synthesized samples. TEM results show that the synthesized AlH3 comprised of 10 - 30 nm particle size range. For hydrogen desorption measurements, it is clear that AlH3 particle size reduction when ball milling using buffer does effectively increase the H desorption rate compared to the case without using buffer. For hydrogen absorption measurements, decomposed AlH3 nanoparticles with 10 - 30 nm in size underwent pressures of 280 bar at -196 C, 1420 bar at 25C, 1532 bar at 50°C, 1734 bar at 100°C and 1967 bar at 150°C with no hydrogen absorption was detected.Ti-Mn alloy compounds with the composition TiMn2, Ti0.97Zr0.019Mn1.5Cr0.57 and Ti0.7875Zr0.2625Mn0.8Cr1.2 were synthesised and compared to the commercially available Ti0.97Zr0.019V0.439Fe0.097Cr0.045Al0.026Mn1.5 alloy composition. An amorphous Ti-Mn alloy was formed when the starting reagents were mechanical alloying for 40 h. The corresponding crystalline phase TiMn was formed when the amorphous alloy was annealed at 800C. The addition of a process control agent (Toluene) leads to the formation of a carbide phase (TiC) in the samples. The presence of impurities, carbide (TiC) and oxide (TiO) phases resulted a decrease in C14 laves phase wt.% in the synthesised samples. Only 37.24, 31.5 and 32.81 wt.% C14 phase was formed in TiMn2, Ti0.97Zr0.019Mn1.5Cr0.57 and Ti0.7875Zr0.2625Mn0.8Cr1.2 respectively. The result also showed that the theoretical value of 1.9 hydrogen wt.% could not be reached by these samples.
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Saleh, Yara. "Etude de la pathogénicité pulmonaire des polluants atmosphériques nanoparticulaires." Thesis, Lille 2, 2019. http://www.theses.fr/2019LIL2S014.
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Introduction : Des études épidémiologiques montrent que les polluants atmosphériques particulaires augmentent le risque de morbidité et de mortalité liées à des maladies respiratoires. La toxicité des particules dépend de leur composition chimique, leur conférant des propriétés mutagènes et/ou cancérogènes, mais également de leur granulométrie qui va conditionner leur pénétration et rétention dans les voies respiratoires.Les particules fines (PF<2,5μm) et surtout les particules ultrafines (PUF<0,1μm) peuvent ainsi atteindre les voies aériennes les plus profondes où leur épuration s’effectuera lentement par clairance macrophagique. Bien que les PUF possèdent une réactivité de surface et donc une toxicité potentielle plus élevées que les PF, leur impact toxicologique réel reste à déterminer.Matériels et méthodes : Pour ce projet, nous avons comparé l’impact sur la santé respiratoire d’une exposition prolongée à des PF et PUF collectées sur un même site urbano-industriel. Après caractérisation physico-chimique des particules (granulométrie, composition surfacique, élémentaire, en HAP), nous avons exposé des souris BALB/c par voie intranasale de manière aiguë à des doses uniques croissantes de PF ou de PUF (10, 50 ou 100 μg) et de manière subchronique pendant 1 mois ou 3 mois, à raison de 3 doses de 10 μg de particules par semaine. Les souris ont été ensuite sacrifiées, des lavages broncho-alvéolaires (LBA) ont été réalisés et différents tissus (sang, poumons, foie, fémurs) ont été prélevés pour effectuer des analyses toxicologiques.Résultats : La composition chimique élémentaire des PF et PUF n’a pas montré de différences majeures mais atteste leur origine industrielle par leur richesse en certains métaux. Par ailleurs, une teneur légèrement supérieure en HAP a été détectée dans les PF par rapport aux PUF. Pour toutes les conditions expérimentales, aucun effet génotoxique et/ou mutagène in vivo n’a été mis en évidence (tests des comètes, des micronoyaux, Pig-A négatifs). En revanche, l’étude de la cellularité des LBA, la quantification de l’expression génique des cytokines et l’analyse histologique des tissus pulmonaires suggèrent la survenue d’une inflammation chronique chez les souris exposées. L’apparition de zones lésionnelles étendues3est cependant plus précoce et plus marquée dans les poumons des souris exposées aux PUF. Des analyses transcriptomiques ont montré d’une part que le nombre de gènes dérégulés croît avec la dose et le temps d’exposition, et d’autre part que ce nombre est largement supérieur chez les souris exposées aux PUF par rapport à celles exposées aux PF. L’identification des principales voies de signalisation les plus significativement impactées confirme que les PUF induisent une réponse des tissus pulmonaires plus intense et plus précoce que les PF.En ce qui concerne les études épigénétiques, une dérégulation de la méthylation de l’ADN, des modifications d’histones et de l’expression génique de certains miARN était plus prononcée chez les souris exposées aux PUF. L’analyse fonctionnelle en cours des miARN spécifiquement dérégulés par les PUF, ou dérégulés communément par les PUF et les PF, devrait permettre l’identification de leurs ARNm cibles.Conclusion : Les résultats issus de ce projet suggèrent que les PUF ont un impact plus nocif sur la santé respiratoire que les PF, et devraient permettre l’identification de nouveaux biomarqueurs d’atteintes tissulaires. Les informations issues de ce projet pourront être transmises aux différents organismes en charge des polluants atmosphériques et de leurs effets sur la santé [...]Background: Air pollution is one of the leading causes of premature death worldwide. Among air pollutants, particulate matter (PM) is a major health risk factor, through the development of pulmonary diseases. The toxicity of PM depends on their chemical composition and size which increases their mutagenic and/or carcinogenic properties and determine their penetration and retention in the respiratory tract. Fine particles (FP <2,5μm) and ultrafine particles (UFP <0,1μm) can thus reach the deepest airways where their purification will be carried out slowly by macrophage clearance. Compared to FP, less is known about the toxicological impact of UFP.Methods: We first compared the impact of prolonged exposure to PF and PUF collected on the same urban-industrial site on the respiratory health in mice. After physicochemical characterization of the particles (granulometry, surface composition, elementary composition, PAH), BALB/c mice were intranasally exposed to increasing single doses of PF or PUF (10, 50 or 100 μg) and subchronically for 1 month or 3 months, to 3 doses of 10 μg of particles per week. Mice were then sacrificed, bronchoalveolar lavages (BAL) were performed and different samples (blood, lungs, liver, femurs) were taken for toxicological analyses.Results: The elemental chemical composition of FP and UFP did not show any major differences but highlights their industrial origin due to their high content of metals. On the other hand, a slightly higher PAH content was detected in FP compared to PUF. For all experimental conditions, no in vivo genotoxic and / or mutagenic effects were detected (comet, micronucleus, Pig-A negative tests). However, the study of the cellularity of BAL, the quantification of cytokine gene expression and histological analysis of lung tissue suggest the occurrence of chronic inflammation in exposed mice lungs. More extended lesioned areas were, however, observed in the UFP-exposed mice. Transcriptomic analyses have shown, on the one hand, that the number of deregulated genes increases with the dose and the time of exposure, and on the other hand that this number is much higher in mice exposed to UFP compared to those exposed to FP. The identification of the main signalling pathways most5significantly impacted confirms that UFP induce greater and earlier lung tissue response than PF. Concerning the epigenetic analyses, deregulation of DNA methylation, histone modifications, and gene expression of some miRNAs was more pronounced in PUF-exposed mice. The ongoing functional analysis of miRNAs specifically deregulated by PUFs, or commonly deregulated by PUFs and PFs, should allow the identification of their target mRNAs.Conclusion: The results of this study suggest that UFP have greater impact on the respiratory system than FPs which would allow the identification of new biomarkers of tissue damage. The information resulting from this project can be transmitted to the different organizations in charge of air pollutants and their effects on health, to the concerned authorities and to the industries in order to contribute to make better decisions regarding the reduction of emissions of particulate pollutants of greatest concern. They will thus help to update the current regulations in order to include UFP and limit their emissions
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David, Cintia de. "Detecção de nano-partículas calcificantes (NPC) em materiais biológicos." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2006. http://hdl.handle.net/10183/8667.
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Nanobactérias (NB) são estruturas não convencionais, com tamanho de 100 a 1000 vezes menor do que bactérias comuns; além disso, sua taxa de crescimento é muito lenta, o que torna sua detecção difícil pelos métodos convencionais. Estas estruturas têm sido isoladas do meio ambiente e, também, em amostras de sangue e urina de animais e humanos, com um envoltório de apatita (fosfato de cálcio) em sua parede celular, relacionando-as à formação de cálculos renais e de outras calcificações patológicas. Os objetivos deste estudo foram analisar diversos materiais biológicos por diferentes metodologias para se verificar a presença de estruturas morfologicamente semelhantes a NB, às quais denominamos de Nano-Partículas Calcificantes (NPC), além de padronizar um teste de ELISA para detecção de anticorpos contra estas estruturas. As amostras foram analisadas utilizando-se as técnicas de microscopia ótica, microscopia eletrônica de varredura, imunofluorescência indireta e ELISA. O uso de microscopia ótica e eletrônica permitiu a observação de partículas com morfologia muito semelhante às NB nas amostras de linhagens celulares, de soro fetal bovino comercial e de cálculos renais humanos. Utilizando-se soros de animais imunizados com NPC, resultados preliminares evidenciaram que o teste de ELISA mostrou boa especificidade.Nanobacteria (NB) are unconventional agents, 100 to 1000-fold smaller than common bacteria; furthermore, their multiplication rate is very slow, making their detection difficult using standard microbiological methods. These structures have been isolated as from environment as human and animal blood and urine. They produce a carbonate apatite (calcium phosphate) layer and they have been associated to kidney stone formation and other pathological calcifications. The aims of this study were analyze various biological materials using different methods to verify the presence of these structures morphologically similar to NB, named as Calcifing Nano-Particles (CNP), and to develop an ELISA test to detect antibodies against these structures. The samples were analyzed using optical microscopy, scanning electron microscopy, indirect immunofluorescence and enzyme-linked immunossorbent assay (ELISA). The optical and electron microscopy allowed us to observe particles with morphology closely similar to NB on cell lineages, commercial fetal bovine sera and human kidney stones samples. Using sera collected from animal immunized with CNP, preliminary results displayed a good specificity of ELISA test.
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Zampiva, Rubia Young Sun. "Síntese e dopagem com érbio de forsterita nanoestruturada e sua caracterização microestrutural e de propriedades óticas." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2017. http://hdl.handle.net/10183/169760.
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A forsterita é um óxido ternário que pertence ao grupo mineral das olivinas. Sua formula empírica é Mg2SiO4, sendo principalmente composta pelo ânion SiO44- e pelo cátion Mg2+ na proporção molar de 1:2. A estrutura do Mg2SiO4 consiste de tetraedros de (SiO4)4- isolados, onde cada um dos oxigênios do tetraedro é compartilhado por três cátions octaédricos (MgO6). Os sítios octaédricos possuem duas conformações cristalográficas não equivalentes, sendo uma maior e menos organizada em relação à outra, ambos os sítios podem ser substituídos por íons tais como metais de transição e terras raras. Esta conformação estrutural faz da forsterita um promissor hospedeiro para aplicações óticas. Entre as terras raras, destaca-se o érbio que já é amplamente aplicado em telecomunicações. O íon Er3+ apresenta conversão ascendente (absorção de dois fótons de menor energia, com emissão em regiões de maior energia) quando excitado no infravermelho próximo emitindo no UV-vis, mantendo esta propriedade de conversão de energia como dopante em diferentes hospedeiros. Conforme o hospedeiro, as linhas de absorção e emissão podem variar em intensidade e posição no espectro. Em outras palavras, o íon dopante pode apresentar propriedades óticas distintas dependendo do hospedeiro em que for inserido. Devido ao leque de possibilidades que se abrem quando as estruturas de forsterita são dopadas, principalmente quando se trata das suas propriedades óticas, e aproveitando das interessantes propriedades das terras raras, em especial do érbio, neste trabalho foram produzidas diferentes nanoestruturas de forsterita dopadas com érbio (nanopartículas, nanofilmes, estruturas unidimensionais e bulk a partir das nanopartículas) para aplicação em três emergentes distintos campos: Biomedicina, produção de energias limpas e lasers de estado sólido com aplicabilidade em macro e nanodispositivos. O sistema Mg2SiO4:Er3+ é apresentado pela primeira vez nesta tese. As análises de conversão ascendente e descendente para todas as estruturas compostas por este sistema apresentaram atividade na faixa ótica de interesse das aplicações sugeridas. Estas somadas a possibilidade de produção a baixo custo com elevada qualidade, quantidade e reprodutibilidade, tornam o sistema Mg2SiO4:Er3+ um material com potencial aplicação industrial.Forsterite is a ternary oxide that belongs to the olivine mineral group. Its empirical formula is Mg2SiO4, mainly consisting of SiO44- anions and Mg2+ cations in the molar ratio of 1: 2. The structure of Mg2SiO4 consists of isolated (SiO4)4-tetrahedra, where each of the tetrahedral oxygens is shared by three octahedral cations (MgO6). The octahedral sites have two non-equivalent crystallographic conformations, one being larger and less organized relativily to the other, and both sites can be replaced by ions such as transition metals and rare earths. This structural conformation makes forsterite a promising host for optical applications. Among rare earths, the erbium, which is already widely applied in telecommunications, stands out. The Er3+ ion presents the upconversion phenomenon (absorption of two photons of lower energy, with emission in higher energy regions) when excited in the near infrared with emission in the UV-vis, keeping the upconversion property as dopant in different hosts. According to the host, the absorption and emission lines can vary in intensity and position in the spectrum. In other words, the dopant ion can present distinct optical properties depending on the host in which it is inserted. Based on the forsterite and erbium properties, this present thesis proposes the synthesis of erbium doped forsterite nanostructures (nanoparticles, nanofilms, one-dimensional structures and bulk from nanoparticles) for application in three different emerging fields: Biomedicine, clean energy and solid state lasers with applicability in macro and nanodevices. The Mg2SiO4: Er3+ system is presented for the first time in this thesis, for the best of our knowledge. The upconversion and downconversion analyses for all erbium concentrations studied in this system showed activity in the optical range of interest of the suggested applications. These results, combined with the possibility of low cost production with high quality, quantity and reproducibility make the Mg2SiO4: Er3+ system a material with potential for industrial application.
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Brunner, Tobias J. "Application of nanoparticulate biomaterials for injectable bone cements and dental repair." kostenfrei kostenfrei, 2007. http://e-collection.ethbib.ethz.ch/view/eth:30076.
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Adisa, Akintayo Oluwole. "Deposition on nanoparticulate metals at the liquid/liquid and templated interface." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498795.
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This thesis considers the deposition of nanoparticulate metals at the liquid/liquid and templated interfaces. It comprises an introduction to the relevant literature. The literature reviewed serves as an introduction to the preparation of nanoparticles in the solution phase, particle growth mechanisms and deposition at the liquid / liquid interface and within porous structures.
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Hall, M. "Design and evaluation of nanoparticulate delivery systems for prodrugs of fluorouracil." Thesis, Queen's University Belfast, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.398106.
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Hapuarachchi, Tharindu Dhanushka. "Development and characterisation of flame retardant nanoparticulate bio-based polymer composites." Thesis, Queen Mary, University of London, 2010. http://qmro.qmul.ac.uk/xmlui/handle/123456789/532.
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Since the discovery of carbon nanotubes (CNTs) and nanoclays, there has been a great deal of research conducted for uses in applications such as: energy storage, molecular electronics, structural composites, biomedical to name but a few. Owing to their unique intrinsic properties and size means that they have an ever growing potential in the consumer and high technology sectors. In recent years the concept of using these as fillers in polymers has shown great potential. One such function is, as flame retardant additives. These possess much better environmental credentials than halogenated based additives as well as only needing to use a small loading content compared to traditional micron sized fillers. The combination of the above make these fillers ideal candidates for polymers and their composites. Especially with regards to natural fibre composites. Owing to environmental awareness and economical considerations, natural fibre reinforced polymer composites seem to present a viable alternative to synthetic fibre reinforced polymer composites such as glass fibres. However, merely substituting synthetic with natural fibres only solves part of the problem. Therefore selecting a suitable material for the matrix is key. Cellulose is both the most common biopolymer and the most common organic compound on Earth. About 33 % of all plant matter is cellulose; i.e. the cellulose content of cotton is 90 % and that of wood is 50 %. However just like their synthetic counterparts, the poor flame retardancy of bio-derived versions restricts its application and development in important fields such as construction and transportation. Abstract -vi- Traditional methods to improve the flame retardancy of polymeric material involve the use of the micron sized inorganic fillers like ammonium polyphosphate (APP) or aluminium trihydroxide (ATH). Imparting flame retardancy with these inorganic fillers is possible but only with relatively high loadings of more than 50 wt. %. This causes detrimental effects to the mechanical properties of the composite and embrittlement. Applying nanofillers can achieve similar if not better flame retarding performances to their micron sized counterparts but at much lower loading levels (<10 wt.%), thus preserving better the characteristics of the unfilled polymer such as good flow, toughness, surface finish and low density. This is the main focus of this study and it will be achieved by using various experimental techniques including the cone calorimeter and the newly developed microcalorimeter. After a comprehensive literature survey (Chapter 2), the experimental part of the thesis starts with a feasibility study of a flame retardant natural reinforced fibre sheet moulding compound (SMC) (Chapter 3). This work demonstrated that with a suitable flame retardant the peak heat release rate can be reduced. Chapter 4 deals with further improving the flame retardancy of the previously used unsaturated polyester resin. The aim is to study any synergistic behaviour by using aluminium trihydroxide in conjunction with ammonium polyphosphate whilst testing in the cone calorimeter. In Chapter 5, nanofillers are used to replace traditional micron sized fillers. In unsaturated polyester, multi-walled carbon nanotubes and sepiolite nanoclay are used together to create a ternary polymer nanocomposite. The microcalorimeter was employed for screening of the heat release rate. This work showed that the ternary nanocomposite showed synergistic behaviour with regards to significantly reducing the peak heat release rate. Abstract -vii- The same nanofillers were utilised in Chapters 6 and 7 but this time in combination with a thermoplastic (polypropylene) and bio-derived polymer (polylactic acid), respectively. In both systems an improved flame retardancy behavior was achieved whist meeting the recyclability objective. Chapter 8 attempts to show how the optimised natural fibre composite would behaviour in a large scale fire test. The ConeTools software package was used to simulate the single burning item test (SBI) and to classify the end product. This is a necessity with regards to commercialising the product for consumer usage. Finally, Chapter 9 is a summary of the work carried out in this research as well as possible future work that should be conducted.
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Smith, Graeme. "Degradation of the nanoparticulate Pt/C air cathode by cyclic thermammetry." Thesis, University of Cambridge, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.610273.
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Yaa, Asantewaa. "Development of a chitosan based glucose responsive nanoparticulate insulin delivery system." Thesis, University of Nottingham, 2014. http://eprints.nottingham.ac.uk/14204/.
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Research into responsive polymeric insulin delivery systems for the management of diabetes mellitus is gaining increasing interest due to the rise in the incidence rate and the burden of daily multiple subcutaneous insulin injections that needs to be endured by the patient. The present study attempted to formulate a nanoparticulate glucose responsive insulin delivery system from a natural polymer chitosan, using a safe glucose sensor, phenyl boronic acid (PBA), which is known to interact with glucose. In the present project, a new method for the production of chitosan tripolyphosphate (TPP) nanoparticles via ultrasonication was developed and optimised. The electrostatic method of tagging PBA onto chitosan was unsuccessful, but the method of N-reductive alkylation of introducing the PBA was successful. Evidence of PBA bonding on to chitosan was assessed by FTIR, ToF-SIMS, DSC and glucose adsorption sensitivity measurements. Glucose adsorption sensitivity to PBA-bonded chitosan polymer was directly related to the amount of PBA functionality within the conjugates and the physical nature of the matrices (porous or crystalline) as revealed by scanning electron microscopy (SEM). The nanoparticles showed glucose concentration dependent swelling with swelling decrease at a glucose concentration above 2.5mg/ml. Encapsulation of insulin into the nanoparticulate matrix was achieved by both the ionotropic gelation and polyelectrolyte complexation methods. Smaller particles with z-average between 140 – 150nm, lower Pdi and zeta potential between 17.5-19.1mV were characteristic of particles produced by PEC, whilst slightly larger particles with z-averages between 170-200nm, higher Pdi and zeta potential between +17.6-21.6mV were noticed for the particles produced by ionotropic gelation. Higher encapsulation of insulin of about 90% was achieved using the PEC method as compared to 34% from the ionotropic gelation series. The amount of drug encapsulated in both methods was pH dependent. In vitro xxi glucose dependent insulin release studied on PEC formulations showed a glucose and fructose concentration dependent release which was affected by the buffer system used. Lower insulin release from higher concentration of the sugars was attributed to the formation of bidentate interaction between the diols in the sugar and PBA, which restricts further expansion of the nanoparticles and hence reduces insulin release. This was confirmed by the SEM images of the nanoparticles after exposure to buffer, glucose and fructose in buffers at pH 7.4. Nanoparticles exposed to fructose showed more spherical and intact matrices whilst the buffer samples showed fragmented particles. The samples exposed to glucose showed some degree of fragmentation but not high as compared to that of nanoparticles exposed to buffer. The release of insulin from this formulation was therefore dependent on a complex interplay between the components of the buffer and the amount of sugar present.
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Männl, Ulrich Philipp. "Electronic properties and microstructure of nanoparticulate silicon systems for diode applications." Doctoral thesis, University of Cape Town, 2014. http://hdl.handle.net/11427/12978.
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Includes bibliographical references.In printed electronics the use of semiconducting silicon nanoparticles allows more than the simple printing of conductive materials. It gives the possibility of fabricating robust and inexpensive, active components. This work presents the design, fabrication, and characterization of Schottky barrier diodes using silicon nanoparticulate composites. Within this work it could be shown, that silicon nanoparticles produced by high energy milling can be used to replace the pigment in water-based graphic inks, which on curing have unique semiconducting properties, arising from the transport of charge through a percolation network of crystalline silicon nanoparticles. In this thesis scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, and mid-infrared scanning near-field optical microscopy (IR s-SNOM) were employed to investigate the micro-scale as well as the meso-scale structure of the printed particle networks and, more importantly the structure of the interface between particles. A close contact between lattice planes of different particles was observed, without the presence of a thick intervening oxide layer. Altogether, the results presented in this thesis suggest that highly doped silicon nanoparticles produced by high energy milling are suitable to be used for Schottky barrier diodes fabricated by screen printing. The saturation current of the diodes was about 0.11µA for reverse bias voltages up to 5V with an ideality factor of 10.6, and rectification ratios of approximately 10⁴ were observed.
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Kandanapitiye, Murthi S. "Synthesis of Biocompatible Nanoparticulate Coordination Polymers for Diagnostic and Therapeutic Applications." Kent State University / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=kent1429019837.
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Freitas, Jilian Nei de. "Celulas fotovoltaicas hibridas de polimeros condutores e nanoparticulas inorganicas." [s.n.], 2009. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248441.
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Orientadores: Ana Flavia Nogueira, Jonas GruberTese (doutorado) - Universidade Estadual de Campinas, Instituto de Quimica
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Resumo: Este trabalho consistiu no desenvolvimento e caracterização de materiais para aplicação em células fotovoltaicas híbridas. No Capítulo I, uma introdução geral sobre o funcionamento e estado da arte de células solares, e sobre as propriedades de polímeros condutores e nanopartículas inorgâncias é apresentada. O Capítulo II contém os objetivos deste trabalho. No Capítulo III, foram investigados novos polímeros condutores, baseados na combinação de unidades fluoreno com unidades tiofeno e/ou benzeno. As propriedades fotofísicas, eletroquímicas e de transporte de cargas foram caracterizadas, e esses polímeros foram então combinados com um derivado solúvel de fulereno (PCBM) e os compósitos formados (heterojunção) foram aplicados em células solares com configuração ITO | PEDOT:PSS | Heterojunção | LiF | Al. A seguir, foram sintetizadas nanopartículas de CdSe com diferentes tamanhos, usando um método descrito na literatura. Essas partículas foram caracterizadas por medidas de absorção e emissão, voltametria cíclica (VC), difração de Raios-X (DRX) e microscopia eletrônica de transmissão (TEM), conforme apresentado no Capítulo IV. Os polímeros investigados inicialmente foram combinados com as nanopartículas de CdSe, e esses materiais foram utilizados na montagem de células solares híbridas. De modo geral, os dispositivos apresentaram valores baixos de fotocorrente, o que foi atribuído ao fato de as nanopartículas inorgânicas não transportarem elétrons de forma efetiva nesses dispositivos. A seguir, propôs-se um novo sistema, em que a heterojunção constitui na mistura ternária polímero/CdSe/PCBM. Esses dispositivos foram caracterizados por curvas de corrente-potencial e pela resposta espectral do sistema, mostrando resultados extremamente promissores. Os sistemas ternários foram então investigados por diversas técnicas, como absorção, emissão, DRX, VC, TEM e microscopia de força atômica, a fim de determinar a atuação de cada componente da mistura ternária quando aplicados nas células solares. Esses resultados são apresentados no Capítulo V. No Capítulo VI, novos polímeros condutores derivados do polifluoreno, contendo unidades funcionais como grupos piridina, ou compostos aromáticos do tipo "push-pull", foram sintetizados pelo método de Gilch. A estrutura desses polímeros foi desenhada visando sua aplicação nas células híbridas, combinandoos com as nanopartículas de CdSe previamente sintetizadas. Esses materiais foram caracterizados por ressonância magnética nuclear de hidrogênio, espectroscopia no Infravermelho com transformada de Fourier. cromatografia por permeação em gel, análises térmicas e medidas eletroquímicas e de fotofísica. No Capítulo VII, propôs-se a introdução de um corante orgânico comercial (Disperse Red 1), como terceiro componente em uma mistura de poli(fluorenilenovinileno) e PCBM, visando aumentar a absorção de luz pela camada ativa do dispositivo. Foi realizado um extenso estudo usando técnicas fotofísicas e eletroquímicas para investigar o efeito da adição do corante, bem como determinar quais os tipos de processos (transferência de elétrons ou energia) ocorrem no sistema ternário. Finalmente o Capítulo VIII contém as principais conclusões deste trabalho e perspectivas de continuação para esta linha de pesquisa.
Abstract: This PhD Thesis investigated the development and characterization of new materials aiming at the application in hybrid solar cells. In Chapter I, a general introduction on the working principles and state-of-the-art of the organic solar cells, properties of the conducting polymers and the inorganic nanoparticles are presented. Chpater II highlights the aims of this work. In Chapter III, new conducting polymers based on the combination of fluorene, thiophene and/or benzene units are investigated. The photophysical and electrochemical characteristics, and charge mobility, are discussed. The polymers were also combined with a soluble fullerene derivative (PCBM) and these composites were used as active layer in bulk-heterojunction solar cells with the following configuration: ITO | PEDOT:PSS | Heterojunction | LiF | Al. Then, CdSe nanoparticles with different sizes were synthesized using a well-established method, and characterized using absorption and emission measurements, cyclic voltammetry (CV), X-ray diffraction (XRD) and transmission electron microscopy (TEM), as presented in Chapter IV. The previously characterized polymers were combined with the CdSe nanoparticles, and the nanocomposites were used to assemble hybrid solar cells. The devices showed very low photocurrent values, which were attributed to a poor electronic transport in the nanoparticles phase. Thus, a new system was suggested, based on a mixture of polymer/CdSe/PCBM. The photocurrent-potential curves and spectral response of the devices assembled with the ternary systems were evaluated, leading to very promising results. The absorption, emission, XRD, CV, TEM and atomic force microscopy measurements of the films were also performed to investigate/elucidate the role of each component in the ternary systems, as discussed in Chapter V. In Chapter VI, new conducting polymers based on poly(fluorenylenevinylene) containing functional units, such as pyridine or push-pull type aromatic units, were synthesized via the Gilch route. The structures of these materials were designed aiming at their application in hybrid solar cells, in combination with the previously synthesized CdSe nanoparticles. The polymers were characterized by magnetic nuclear resonance, Fourier transform infrared spectroscopy, gel permeation chromatography, and thermal, electrochemical and photophysical measurements. These polymers were combined with CdSe and/or PCBM and used as active layer in solar cells. In Chapter VII the addition of the commercial organic dye Disperse Red 1 in the mixture of poly(fluorenylenevinylene)/PCBM to enhance the light absorption in the active layer was investigated. A systematic study using photophysical and electrochemical measurements was performed in order to elucidate the effect of the dye addition, as well as the energy or electron transfer processes in this new ternary system. Finally, Chapter VIII summarizes the main conclusions of this work and highlights some perspectives for this exciting research filed.
Doutorado
Quimica Inorganica
Doutor em Ciências
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Guerra, Rubens Antônio. "Estudo da interação de porfirinas com nanoparticulas magnéticas biocompativeis." Universidade Federal de Goiás, 2015. http://repositorio.bc.ufg.br/tede/handle/tede/4479.
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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
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O objetivo deste trabalho de mestrado é o estudo das interações entre porfirina de base livre (TMPP) e seu complexo metálico (ZnTMPP) com nanopartículas magnéticas biocompatíveis com diferentes camadas de cobertura. O sistema em estudo mostrou potencial para possíveis aplicações na medicina moderna, particularmente na terapia fotodinâmica ou como marcador fluorescente na magnetohipertermia. O presente sistema foi investigado através do uso de técnicas espectroscópicas de onde foram obtidas constantes de ligação, supressão, anisotropia e constante de velocidade bimolecular.
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Mendes, Paulo Gedeão. "ESTUDO DA CINÉTICA DE SINTERIZAÇÃO EM SISTEMAS NANOPARTICULADOS DE SnO2." UNIVERSIDADE ESTADUAL DE PONTA GROSSA, 2009. http://tede2.uepg.br/jspui/handle/prefix/1443.
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Previous issue date: 2009-08-21Several synthesis methods exist for ceramic materials. According to the method of synthesis used to prepare oxide materials different morphologic and microstructural properties can be obtained. This work consisted of studying the Co-doped tin dioxide powders synthetized by microwave-assisted hydrothermal synthesis (MAHS) and the results were compared to powders synthesized by Pechini method. Powders synthesized by MAHS presented size of particles in the order of 5 nm while the size of particles obtained by Pechini was about five times greater. Besides the characterization of those materials in the powder form, the material was compacted and sintered. Sintering at different constant hating rates of constant heating allowed the calculation of the apparent global energy of sintering using the master sintering curve model. The material synthesized by MAHS presented a smaller apparent global energy of sintering than that obtained by Pechini route, and in the same proportion of their size differences. The results of this work lead to the conclusion that the sintering process and the saturation of dopants are strongly influenced by the particle size of starting powders.
Vários são os métodos de síntese dos materiais cerâmicos. Conforme o método de síntese utilizado para preparar materiais óxidos, diferentes serão suas propriedades morfológicas e microestruturais. Este trabalho consistiu em estudar o dióxido de estanho dopado com óxido de cobalto a partir da síntese de hidrotermalização assistida por micro-ondas (HTMW) e os resultados foram comparados aos da síntese via método Pechini. Pós sintetizados via HTMW apresentaram tamanho de partículas da ordem de 5 nm enquanto via Pechini em torno de cinco vezes maior. Além da caracterização desses materiais na forma de pó, o material foi compactado e sinterizado em dilatômetro. A sinterização a partir de diferentes taxas de aquecimento constante tornou possível o cálculo da energia global aparente de sinterização a partir do modelo da curva mestre de sinterização. O material sintetizado via HTMW apresentou energia global aparente de sinterização menor que o sintetizado via Pechini, na mesma proporção de suas diferenças de tamanho. Assim com este trabalho conclui-se que o processo de sinterização e a saturação de dopantes são fortemente influenciados pelo tamanho de partícula do pó de partida.
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Balbinot, Carlos Eduardo Agostini. "Avalia??o de propriedades mec?nicas de resinas compostas nanoparticuladas." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2006. http://tede2.pucrs.br/tede2/handle/tede/1173.
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Previous issue date: 2006-12-11Este estudo teve como objetivo avaliar as propriedades mec?nicas selecionadas (resist?ncia ? compress?o, resist?ncia ? tra??o diametral, resist?ncia flexural de tr?spontos e m?dulo flexural) de quatro marcas diferentes de resina composta nanoparticuladas e uma resina composta microh?brida, nas cores A2 esmalte e dentina. Foram confeccionadas dez amostras para cada grupo de cada teste. O m?dulo flexural foi calculado a partir dos resultados do teste de resist?ncia flexural. Os resultados obtidos nos ensaios foram comparados estatisticamente com an?lise de vari?ncia e teste de Tukey (p < 0,01). N?o houve diferen?a estatisticamente significante para os grupos testados no teste de resist?ncia ? compress?o, sendo que as m?dias variaram entre 141,04 MPa para a resina 4 Seasons A2E e 206,08 MPa para a resina Grandio A2O. No teste de resist?ncia flexural, houve diferen?a estatisticamente significativa entre os grupos, onde as medias variaram entre 59,16 MPa para a resina 4 Seasons A2E e 122 MPa para a resina Supreme XT A2E. Houve diferen?a estatisticamente significante para m?dulo flexural e neste teste as m?dias variaram entre 3,4 GPa para a resina 4 Seasons A2E e 13,30 GPa para a resina Grandio A2O. No teste de resist?ncia ? tra??o diametral, a resina Esthet-X A2O apresentou m?dia (34,87 MPa) estatisticamente menor que os demais grupos, e a resina Supreme XT A2E (50,26 MPa), estatisticamente maior que os demais grupos testados; entre os demais grupos n?o houve diferen?a estatisticamente significante. Apesar de diferen?as nos valores entre os grupos testados nos testes de resist?ncia flexural, m?dulo flexural e resist?ncia ? tra??o diametral, as resinas nanoparticuladas, baseados nos resultados obtidos neste estudo, apresentam propriedades mec?nicas semelhantes da resina microh?brida
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Boita, Jocenir. "Estudos in situ da formação de compostos de cobre nanoparticulados." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/21698.
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Neste trabalho foi realizado o monitoramento da formação de agregados de cobre (micro e nano) particulados em solução aquosa através da técnica de DXAS in situ (Espectroscopia de Absorção de Raios X no modo Dispersivo), com resolução temporal. Uma parte importante deste trabalho foi o desenvolvimento de um reator adequado para a realização dos experimentos in situ. Os espectros de XAS mostraram a evolução temporal das propriedades eletrônicas e estruturais na vizinhança dos átomos de cobre, desde os íons em solução até a formação de agregados. Foi estabelecida uma correlação entre os resultados obtidos por DXAS com outras técnicas de caracterização utilizadas (MEV, DRX, XPS). O trabalho desenvolvido nesta dissertação contribuirá para futuros estudos de processos envolvidos na formação de nanopartículas, visando suas aplicações em catalisadores, células combustíveis e biosensores.In this work, we have monitored the formation of copper based aggregates (micro and nano sized) in aqueous solution using the DXAS in situ technique (dispersive x-ray absorption spectroscopy), in the time resolved mode. A crucial part of this work was the development of a dedicated reactor for the in situ experiments. The XAS spectra showed the evolution of the structural and electronic properties around the copper atoms, from the ions in solution until the formation of the aggregates. A correlation between the results obtained by DXAS and by other characterization methods (SEM, XRD, XPS) was established. The work developed in this dissertation will contribute for future investigations of the processes involved in the formation of nanoparticles in solution, which may be applied for catalysts, fuel cells and biosensors.
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Gallardo, Marie-Madeleine. "Caractérisations physico-chimiques de systèmes nanoparticulaires de polyisobutyl-2-cyanoacrylate." Paris 11, 1991. http://www.theses.fr/1991PA114816.
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Sharma, Ankur. "Development of nanoparticulate drug delivery systems for anti-metastatic Ran GTPase therapeutics." Thesis, Ulster University, 2017. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.725342.
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