Дисертації з теми "Nanomateriale"
Оформте джерело за APA, MLA, Chicago, Harvard та іншими стилями
Ознайомтеся з топ-50 дисертацій для дослідження на тему "Nanomateriale".
Біля кожної праці в переліку літератури доступна кнопка «Додати до бібліографії». Скористайтеся нею – і ми автоматично оформимо бібліографічне посилання на обрану працю в потрібному вам стилі цитування: APA, MLA, «Гарвард», «Чикаго», «Ванкувер» тощо.
Також ви можете завантажити повний текст наукової публікації у форматі «.pdf» та прочитати онлайн анотацію до роботи, якщо відповідні параметри наявні в метаданих.
Переглядайте дисертації для різних дисциплін та оформлюйте правильно вашу бібліографію.
Souza, Caio Guilherme Secco de. "Nanomateriais luminomagnéticos visando aplicações biológicas: síntese, propriedades, funcionalização e estabilidade coloidal." Universidade de São Paulo, 2015. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-11082015-090833/.
Повний текст джерелаHere, luminomagnetic nanomaterials were obtained for potential biological applications. We have studied two different types of luminomagnetic nanomaterials, which are: formation of silica-coated FePt/Fe3O4-CdSe heteronanostructures; and formation of luminomagnetic nanomaterials from covalent bond between FePt/Fe3O4-Dopa-PIMA-PEG-NH2 magnetic nanoparticles and CdSe/ZnS-LA-PEG-COOH luminescent quantum dots. For the first type of luminomagnetic nanomaterials obtained, two methodologies were studied for formation of heteronanostructures, which are: modification of colloidal stability by addition of small amounts of NaCl into a solution with hydrophobic magnetic nanoparticles and luminescent quantum dots; and hot injection method of selenium precursor into a solution with magnetic nanoparticles seeds, cadmium precursors and surface agents. The hot injection method obtained better results than the other method studied for formation of heteronanostructures. To provide colloidal stability in aqueous solution and biocompatibility, the heteronanostructures were coated using silica shell. After silica coating, the heteronanostructures showed average diameter of 25 nm and polidispersivity of 8.4%, with Ms = 11.1 emu.g-1 and superparamagnetic behavior. Moreover, these nanomaterials showed two emission peaks centered at 452 and 472 nm. For the second type of nanomaterials obtained, FePt/Fe3O4 magnetic nanoparticles were synthesized by modified polyol method coupled to seeded-mediated growth, and CdSe/ZnS luminescent quantum dots were obtained by thermal decomposition of organometallic precursors. For the ligand exchange to transfer the nanostructures from organic media to aqueous solution, were used Dopa-PIMA-PEG-NH2 and LA-PEG-COOH polymers to provide colloidal stability and biocompatibility on magnetic nanoparticle surface and quantum dot surface, respectively. The chemical conjugation between FePt/Fe3O4-Dopa-PIMA-PEG-NH2 and CdSe/ZnS-LA-PEG-COOH nanostructures was obtained by EDC coupling in aqueous solution, which linked amine and carboxylate groups in each nanostructure to provide the formation of amide bond. The luminomagnetic nanomaterials obtained showed colloidal stability in aqueous solution, narrow size distribution, with RH equal to 79.96 nm, MS around 10 emu.g-1 with low coercivity and remanent magnetization, and intense emission peak centered at 580 nm. We expect these luminomagnetic nanomaterials be promisor nanomaterials with multifunctional properties for potential biological applications.
Ahmad, Abo Markeb Ahmad Mohamed. "Environmental applications of engineered nanomaterials: synthesis and characterization." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/454768.
Повний текст джерелаThis thesis is based on the development (synthesis) of different nanomaterials for their application as adsorbent materials for the removal of pollutants from water (inorganic anions, heavy metals and pesticides) and for the adsorption of methane gas. The development of the different materials has been based on an extensive bibliographical search of the state of the art of the materials currently used for this application, and it has been tried to improve the efficiency of the process by using nanomaterials. Thus, magnetic (magnetite) nanoparticles are synthesized by different methods. These are functionalized with organic groups to adapt and/or improve their adsorption function or stabilize in supports (polymers, zeolites, sponges, etc.) to improve their application on a real scale. In addition, a new method for the formation of core-shell nanoparticles with a magnetite core is developed. All the synthesized nanomaterials have been characterized in depth, using the most advanced techniques for the characterization of nanomaterials. Techniques such as electron microscopy, X-ray diffraction, among others, allow to know the characteristics and properties of the materials (size, dispersion, crystallinity, structure, etc.) and thus conclude their contribution to the efficiency of their application with adsorbent material. As for the contaminants in water, the work focuses on fluoride, phosphates, nitrates, cadmium, nickel and pesticides, obtaining outstanding results for the nanoparticles of Ce-Ti @Fe3O4. In the case of gas treatment, on the one hand has developed a new nanomaterial based on magnetic nanoparticles stabilized in polyurethane sponges which present interesting results for the adsorption of methane and great applicability on a real scale. In addition, we have collaborated with the Institut Català de Nanotecnologia for the applicability of Metal Organic Frameworks in the oxidation of CO. Another application that has been given to magnetic nanoparticles has been its use to separate algae from wastewater treatment processes, in order to substitute the current sedimentation processes. With all this, the thesis offers a range of nanomaterials for different uses in environmental engineering, with the possibility of investigating and developing on its applicability on a large scale. To this end, different solutions are provided for the improvement of the environment.
Russo, Lorenzo. "Designing advanced nanomaterials for next generation in vitro diagnostics: development of optical and electrochemical biosensors for determination of viral and bacterial infections based on hollow AuAg nanoparticles." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/666751.
Повний текст джерелаIn this PhD thesis, the rational design of advanced nanomaterials with controlled properties was applied for their employment in biosensing, leading to the development of two diagnostic platforms for the determination of viral and bacterial infections. Firstly, a highly reproducible and robust synthetic method for the production of monodisperse AuAg alloy NSs based on GRR was developed. The protocol described allows the precise control over the particles’ morphology, in terms of shell thicknesses and void sizes, the relative composition and topological distribution of their constituting noble metals, as well as their surface roughness and porosity. This synthetic predictability, tested over a range of sizes, has been achieved through a systematic study of the convoluted interplay of each co-reagent, together with a detailed characterization of the material’s composition and structure through an array of techniques. Moreover, the analysis of AuAg NSs’ plasmonic properties evolution during their structural transformation, which spanned through almost the whole visible spectrum up to NIR wavelengths, revealed a tight dependence with their morphological and compositional features. These results, also confirmed by calculations based on Mie’s theory, provided the basis for their application as signal enhancers in the SERS-based LFA developed. Secondly, for the first time the electrochemical behavior of AuAg NSs was reported. Triggered by the controlled corrosion of Ag atoms contained in the particles’ residual cores and thin alloy shells, the voltammetric study of these hollow nanocrystals has been found to be strongly dependent on their relative elemental composition and, partially, to their size and morphology. Indeed, a peculiar electrocatalytic effect appeared only for AuAg NSs possessing a high-enough Au/Ag ratio to let the catalytic electrodeposition of Ag+ on the NSs’ surfaces occur at potentials less negative than Ag standard reduction one. Interestingly, this unreported feature was shown to be triggered only by the mild oxidating character of the electrolyte used, without the need of any other co-reagent or oxidizer. These findings constituted the rational basis for developing AuAg NSs with desirable properties to be applied in the electrochemical assay described. Taking advantage of the tunable plasmonic properties of AuAg NSs, the development of a SERS-based LFA for the sensitive and quantitative detection of MxA, a biomarker commonly associated to viral infections, was achieved. Thanks to the enhanced plasmons intensities displayed by AuAg NSs, resulting from the plasmonic cavity effect commonly observed in hollow nanostructures, their surfaces acted as a continuous hot-spot, amplifying any Raman signal emitted by the reporters thereby attached. Moreover, the possibility to precisely adjust AuAg NSs’ LSPR maximum wavelength to match the NIR excitation laser used during SERS measurements allowed to further improve the overall analytical performance. Thus, AuAg NSs were easily conjugated with anti-MxA antibodies and integrated in a LFA in order to reveal its presence in spiked serum samples. After careful optimization of the point-of-care platform parameters, MxA protein could be successfully detected down to the analytically-relevant LOD of few ng/mL. Finally, the capability to precisely modulate AuAg NSs elemental composition lead to the design of a proof-of-concept electrochemical assay for the rapid detection of two model bacterial strains, Escherichia coli and Salmonella typhimurium. AuAg NSs were used as electrochemical reporters because of the ease of generation of the electrochemical signal, triggered by the sole mild oxidating character of the biological sample matrix. Besides, the polymeric coating of the hollow particles provided the non-specific, affinity-based interaction with bacterial cells in solution, avoiding the need for costly and fragile antibodies. With this low-cost strategy, E.coli could be detected in PBS down to 102 CFU/mL, while the semi-selective discrimination of the current-concentration profiles of the two model bacterial strains was also achieved.
Spångberg, Christian. "En studie om regleringen av nanomaterial : - i The Toxic Substances Control Act (TSCA) och Registration, Evaluation, Authorisation and Restriction of Chemicals (REACH)." Thesis, Uppsala universitet, Juridiska institutionen, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-327381.
Повний текст джерелаLEPORE, EMILIANO. "An experimental study on adhesive or antiadhesiveand strong bio-inspired nanomaterials." Doctoral thesis, Politecnico di Torino, 2012. http://hdl.handle.net/11583/2498977.
Повний текст джерелаGarzón, Manjón Alba. "Synthesis of Metal Oxide Nanoparticles for Superconducting Nanocomposites and Other Applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399330.
Повний текст джерелаThermal and microwave methodologies are used to synthesize different metal oxides nanoparticles such as magnetite (Fe3O4), cerium oxide (CeO2). By modifying the precursors (Fe(R2diket)3 (R= Ph, tBu and CF3), Ce(acac)3 and Ce(OAc)3), and following the same synthetic route, it is possible to control the size and shape of the nanocrystals obtained. The general route is carried out in triethylene glycol (TREG) or benzyl alcohol (BnOH) media, due to its high boiling point and, which acts also as a capping ligand of the nanoparticles, stabilizing them in polar solvents. Nanoparticles have been characterized by several common physical laboratory techniques: High Resolution Transmission Electron Microscopy (HR TEM), infrared spectroscopy (IR), X-ray Powder Diffraction (XRPD), magnetometry via Superconducting Quantum Interference Device (SQUID), Nuclear Magnetic Resonance (RMN), Gas Chromatography-Mass Spectroscopy (GC-MS), X-ray Photoelectron Spectroscopy (XPS) and Thermogravimetric Analysis (TGA). With all these techniques, the final size, shape, composition, crystal structure, magnetic behaviour and capping ligand interaction have been studied, showing the high quality crystals generated. In addition, we demonstrate the high efficiency of all two one-pot methodologies that have been optimized to synthesize different families of nanoparticles. The stable colloidal solutions obtained in ethanol have been used to generate ex-situ hybrid YBa2Cu3O7-δ (YBCO) superconducting layers because the critical current can be increased when the nanoparticles are embedded. Finally, a new application as an antioxidant behaviour in human cells is tested for the case of CeO2 nanoparticles due to their specifically properties that make them really interested in this new field.
Rodrigues, Carolina Martins. "Desenvolvimento de materiais nanoestruturados baseados em oxidos mistos de metais de transição (Ti, Zr)." [s.n.], 2007. http://repositorio.unicamp.br/jspui/handle/REPOSIP/249015.
Повний текст джерелаDissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Quimica
Made available in DSpace on 2018-08-08T23:15:36Z (GMT). No. of bitstreams: 1 Rodrigues_CarolinaMartins_M.pdf: 50415494 bytes, checksum: b98d1323abe212ba30a7712dd028ce6f (MD5) Previous issue date: 2007
Resumo: Esta dissertação visa à obtenção de nanoestruturas partindo do óxido misto Ti1-xZrxO2. O óxido precursor foi preparado pelo método de precipitação homogênea, via tetracloreto de titânio e oxicloreto de zircônio, usando uréia como reagente precipitante. Esses óxidos foram submetidos ao tratamento hidrotérmico em autoclave, em solução de NaOH, empregando temperatura de 140 e 170°C com intervalo de tempo de 2 a 7 dias. De acordo com as caracterizações físico-químicas feitas foi observado que os produtos obtidos via tratamento hidrotérmico com x < 0,50 apresentaram morfologia de nanotubos, nanoplacas e nanobastões. Entretanto, para x acima de 0,05 mostraram a existência de duas fases cristalinas, titanato de sódio e ZrO2 tetragonal. Para x > 0,50 não apresentaram mudanças morfológicas, tendo como fase formada o ZrO2 tetragonal. Quando o precursor com x = 0,50 (fase ZrTiO4) é observado no produto do tratamento hidrotérmico manutenção da estrutura cristalina e presença de nanotubos. Foi também mostrado, para x = 0,15, que o aumento de volume da solução na autoclave promove aumento da cristalinidade e destruição da organização das partículas. O aumento do tempo e da temperatura de reação proporcionou maior cristalinidade aos produtos hidrotérmicos com x = 0,15 e 0,50; para x = 0 aumento de nanotubos e para x = 0,15 diminuição das nanoplacas e para x = 0,80 e 1 não apresentaram mudanças nem na morfologia, nem na cristalinidade. Foi avaliada a reatividade dos nanotubos (x=0) e nanobastões/nanoplacas (x = 0,15) frente às moléculas orgânicas. Foi observado que os nanotubos interagem melhor com moléculas ácidas, e que tais moléculas promovem a destruição da morfologia e mudança da estrutura cristalina, sendo estas mais drásticas quando com aquecimento. Os nanobastões/nanoplacas interagem mais fortemente com as moléculas ácidas, porém sem perda de morfologia e estrutura cristalina
Abstract: The main of this Dissertation is the preparation of nanostructures from T1-xZrxO2 mixed oxide. The precursor oxide was prepared by the homogeneous precipitation method, from titanium tetrachloride and zirconium oxichloride, using urea as the precipitating agent. The oxides were hydrothermally treated in autoclave, in NaOH solution, at temperatures of 140 and 170 °C, for period of 2 to 7 days. According to the physical-chemical characterizations, it was observed that the products prepared by the hydrohermal treatment with x < 0.50 presented morphologies like nanotubes, nanosheets and nanorods. However, for x > 0.05, it was observed the presence of two crystalline phases, sodium titanate and tetragonal ZrO2. For x > 0.50, it was not observed morphological changes, being tetragonal ZrO2 the obtained phase. Starting from the mixed oxide with x = 0.50, ZrTiO4 phase, it was observed nanotubes with the same crystalline phase. For x = 0.15, it was also observed that the increase of solution volume in the autoclave causes a crystallinity increase and destruction of the particles organization. The increase in time and temperature of reaction caused an increase in the crystallinity of the hydrothermal products for x = 0.15 e 0. 50; for x = 0, it was observed more quantity of nanotubes; and for x = 0.15, fewer nanosheets; for x = 0.80 and 1, it was not observed either morphological neither crystalline changes. The reactivity of the nanotubes (x = 0) and nanorods/nanosheets (x = 0.15) with organic molecules, which promote the morphology destructions and changes in the crystalline structure. These effects were increased with heating. The nanorods/nanosheets strongly interact with acid molecules, without loosing of morphology or the original crystalline structures
Mestrado
Quimica Inorganica
Mestre em Química
Rodríguez, Rodríguez Jordi. "Síntesis y Caracterización de Óxido de Grafeno Reducido Funcionalizado con Nanopartículas Metálicas. Aplicación en el Desarrollo de Sensores Amperométricos Basados en Materiales Nanoestructurados." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/671817.
Повний текст джерелаEl desarrollo de nuevos (bio)sensores es un campo en desarrollo dentro de la Química Analítica y, en general, de la sociedad. El uso de sensores está altamente extendido en la vida cotidiana de las personas. En el mercado, se encuentran disponibles distintos tipos de glucómetros, que pueden informar de la concentración de glucosa en sangre en tiempo real del paciente. También existe una demanda de nuevos test de diagnosis para enfermedades como la provocada por el virus SARS-COVID-19. El grafeno se ha convertido en un material de gran interés entre la comunidad científica, debido a las propiedades eléctricas, térmicas y mecánicas únicas que este material posee respecto a otros materiales carbonáceos y 2D. Debido a sus excepcionales características y propiedades el uso de grafeno como material conductor alternativo en el desarrollo de transductores electroquímicos se ha extendido ampliamente y convertido en uno de los principales recursos. Los nanocompósitos se sitúan como una alternativa muy interesante en el desarrollo de sensores amperométricos. Debido a la capacidad de integrar varios materiales con diferentes características con la finalidad de obtener un nuevo material con propiedades físicas, mecánicas y eléctricas muy diferentes a los materiales originales que lo constituyen. El uso de nanocompósitos presenta una serie de ventajas respecto a los conductores puros. Por ejemplo, versatilidad, durabilidad, facilidad de regeneración de la superficie y su capacidad de integración de otros modificadores, cualidades que proporcionan un valor añadido a los dispositivos desarrollados. Las propiedades electroquímicas de los nanocompósitos están altamente influenciadas por la naturaleza de las partículas conductoras que lo forman, así como la cantidad y la distribución espacial de estas en la matriz del nanocompósito. Una de las características más relevantes que poseen estos materiales es la similitud en su comportamiento electroquímico respecto a un haz de microelectrodos. La presencia de partículas conductoras, separadas por áreas no conductoras o aislantes en la superficie del electrodo, mimetiza la distribución más o menos ordenada de microelectrodos separados entre sí por un aislante eléctrico, configurando así un haz de microelectrodos. La respuesta electroanalítica de un haz de microelectrodos depende fundamentalmente de las dimensiones y separación entre las partículas conductoras. Por este motivo, es necesaria una optimización de la cantidad de material conductor y de su distribución con el objetivo de obtener la mejor eficacia analítica. Bajo este contexto, la primera etapa de esta Tesis es la síntesis de óxido de grafeno reducido (rGO) mediante el método de Hummers. Este método permite obtener rGO utilizando grafito comercial como material de partida para la fabricación de electrodos nanocompósitos basados en rGO y una resina epoxi (EpoTek H77). Posteriormente, se ha implementado un conjunto de técnicas instrumentales que, aplicadas de forma estratégica y sistemática, han permitido la caracterización y optimización de la composición del material conductor; así como la mejora de las propiedades electroquímicas de los electrodos nanocompósitos desarrollados con los diferentes materiales conductores sintetizados. Una vez optimizadas las propiedades de los transductores electroquímicos se procedió a la mejora de las propiedades de estos sensores, mediante la incorporación de diferentes nanopartículas (NPs) metálicas, con el objetivo de introducir un efecto electrocatalítico en el dispositivo analítico. Se desarrolló una metodología sintética que permite incorporar ad hoc NPs de diferentes metales (e.g Au, Ag, Pd) en la superficie del rGO, de una manera sencilla y mediante química verde. Finalmente, se ha desarrollado un (bio)sensor utilizando la enzima glucosa oxidasa (GOD), basado en un nanocompósito de 2Au/3Pd-NP@rGO. Estudiando el efecto catalítico que tienen las NPs bimetálicas de Au y Pd frente al H2O2. Para finalizar, se estudió el efecto de la presencia del ácido ascórbico en las medidas electroanalíticas.
The development of new (bio)sensors is a field in full development within the needs of Analytical Chemistry and society in general. The use of sensors is highly extended in people’s daily life. Different types of glucometers are available on the market, which can report the concentration of glucose in the patient’s blood in real time. Also, one can see today’s need to develop new diagnostic tests for diseases, such as that caused by the SARS-COVID-19 virus. Graphene has become a material of great interest among the scientific community, due to the unique electrical, thermal and mechanical properties that this material possesses with respect to other carbonaceous and 2D materials. Due to its exceptional characteristics and properties, the use of graphene as an alternative conductor material in the development of electrochemical transducers has become widespread and one of the main resources. Nanocomposites are a very interesting alternative in the development of amperometric sensors. Due, especially, to the capacity of integrating several materials with different characteristics in order to obtain a new material with very different physical, mechanical and electrical properties from the original materials that constitute it. The use of nanocomposites has a series of advantages over pure conductors. These advantages are, for example, versatility, durability, ease of surface regeneration and its ability to integrate other modifiers, qualities that provide added value to the developed devices. The electrochemical properties of nanocomposites are highly influenced by the nature of the conductive particles that form it as well as their amount and spatial distribution in the matrix of the nanocomposite. One of the most relevant characteristics of these materials is the similarity in their electrochemical behavior with respect to a microelectrode array. The presence of conductive particles, separated by non-conductive or insulating areas on the electrode surface, mimics the more or less ordered distribution of microelectrodes separated by an electrical insulator, forming the equivalent of a microelectrode array. The electro-analytical response of a microelectrode array depends mainly on the dimensions and separation between the conductive particles. For this reason, it is necessary to optimize the quantity of conductive material and its distribution to obtain the best analytical efficiency. In this context, the first stage of this Thesis is the synthesis of reduced graphene oxide (rGO) by Hummers’ method. This method allows obtaining rGO, from commercial graphite as a starting material, for the manufacture of nanocomposite electrodes based on rGO and an epoxy resin (EpoTek H77). Subsequently, a set of instrumental techniques have been implemented, which, applied in a strategic and systematic way, have allowed the characterization and optimization of the composition of the conductive material as well as the improvement of the electrochemical properties of the nanocomposite electrodes developed with different synthesized conductive materials. Once the properties of the electrochemical transducers were optimized, it was time to improve the analytical properties of these electrochemical sensors through the incorporation of different metallic nanoparticles (NPs) with the aim of introducing an electrocatalytic effect into the analytical device. This way a synthetic methodology was developed, allowing the incorporation ad hoc of different metal NPs (e.g. Au, Ag, Pd) on the rGO’s surface in a simple way and by means of green chemistry. Finally, a (bio)sensor has been developed using the enzyme glucose oxidase (GOD), based on a 2Au/3Pd-NP@rGO nanocomposite. Studying the catalytic effect that bimetallic Au and Pd NPs have upon H2O2. Finally, the effect of ascorbic acid’s presence in electroanalytical measurements (an interferent present in many biological samples) was studied.
Universitat Autònoma de Barcelona. Programa de Doctorat en Química
Molet, Bachs Pau. "Managing light in optoelectronic devices with resonant optical nanostructures." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673260.
Повний текст джерелаActualmente, uno de los retos en el ámbito de la manipulación de la luz a la nanoescala es la transición del laboratorio a aplicaciones reales. A pesar del gran potencial demostrado por algunas estructuras fotónicas para incrementar la eficiencia de instrumentos optoelectrónicos, su implementación en dispositivos de mercado muchas veces es obstruida por la necesidad de utilizar técnicas de fabricación poco escalables y de alto coste. Esta tesis está dedicada al diseño e implementación de estrategias de manipulación de la luz para mejorar la eficiencia en la recolección de energía de placas solares y fotodetectores, así como la mejora de la emisión en dispositivos de iluminación, mediante métodos de nanoestructuración escalables como la nano-litografía suave. Esta técnica tiene la capacidad de producir patrones y estructures con una resolución de pocos nanómetros con gran fidelidad en áreas grandes. Encima, es compatible con el procesamiento a gran escala mediante el sistema de impresión en cadena “roll-to-roll” (carrete-a-carrete). También se trata de una tecnología muy versátil, puesto que permite el uso de diferentes tipos de sustratos, es poco invasiva y generalmente puede ser introducida en el esquema de fabricación sin tener que modificar ningún paso. Con la ayuda de esta técnica de nanofabricación, exploramos una variedad de arquitecturas fotónicas y las diferentes resonancias fotónicas que las hacen especiales. Entre estas últimas podemos encontrar resonancias de Mie, modos de Brewster y modos de cristal fotónico, que proveerán al sistema con una mayor interacción luz-materia a la capa activa del dispositivo, mejorar sus capacidades ópticas. Primero, hemos desarrollado una estrategia para conseguir una absorción óptima de banda ancha en semiconductores ultra-finos, con menos de 100 nm de grosor, para todas las energías por encima de su energía de banda prohibida. La sinergia de las fuertes resonancias de interferencia de capas finas presentes y los modos del cristal fotónico de la estructura (con un alto índice de refracción) hacen que la estructura logre hasta un 81% de absorción en un amplio rango de longitudes de omda (de 400 a 1500 nm). En segundo lugar, hemos combinado la litografía suave con la deposición química de vapor (CVD en inglés) para obtener una matriz de semiesferas de silicio sobre de una guía de ondas de alto índice de refracción. Hemos estudiado las resonancias de Mie características del sustrato, como hibridan con modos casi-guiados de la guía de olas y como esto afecta en el campo próximo de la metasuperfície. Hemos ido un paso más allá estudiando como la modificación de los parámetros del diseño de la estructura afecta a las resonancias mencionadas. Finalmente, hemos demostrado una posible aplicación como sustrato para incrementar la emisión de luz por parte de una molécula emisora. En la tercera parte de la tesis, nos hemos enfocado en la implementación de estructuras de cristal fotónico bidimensional a tres dispositivos diferentes para la mejora de su eficiencia. En particular, mejoramos la eficiencia en la recolección de fotones de infrarrojo próximo en células solares de puntos cuánticos coloidales (PbS) y en fotodetectores orgánicos (P3HT: PC60BM y PBTTT: PC70BM), y mejoramos la emisión de luz de capas de nanofósforos (nanocristales de GdVO4:Eu3+). Hemos desarrollado sistemas fotónicos adaptados a cada caso y hemos hecho una caracterización óptica y electrónica de todos los dispositivos. La nanoestructuración en forma de cristal fotónico bidimensional provee a las capas activas con propiedades de guías de onda resonantes, mejorando sus propiedades de confinamiento de la luz en las longitudes de onda deseadas, demostrando así la posibilidad de implementar las arquitecturas.
Currently, one of the main challenges in light management at the nanoscale is the transition from the laboratory to real applications. Despite the great potential shown by photonic architectures to optically improve the performance of many devices, transitioning into marketable devices is often hampered by the low-throughput and expensive nanofabrication techniques involved. This thesis is devoted to the design and development of subwavelength light managing strategies to improve the light harvesting or out-coupling in solar cells, photodetectors and light emitters while using a scalable nanostructuration such as soft nanoimprint lithography (NIL). This technique has been proven to achieve resolutions down to few tens of nanometers with high fidelity in large areas, being compatible with roll to roll processing. It is also versatile regarding the materials where it can be used, non-invasive, and can be seamlessly introduced in the devices fabrication scheme. With the aid of this technique, we explore a variety of photonic architectures and the different types of resonances sustained, from Brewster modes to Mie resonances, in order to enhance the light-matter interaction with the active layer of the device. First, we develop a strategy to achieve broadband optimal absorption in ultra-thin semiconductor materials (less than 100 nm thick) for all energies above their bandgap. The interplay of strong interference thin film resonances and photonic crystal modes sustained by a high refractive index nanostructure on a gold film renders the system with a 81% total absorption over a broad spectral range (from 400 to 1500 nm). Second, we combine soft NIL and chemical vapor deposition to obtain an array of silicon hemispheres on top of a high refractive index dielectric waveguide. We study the Mie resonances supported by the substrate, how these hybridize with the guided modes of the waveguide and how their interaction influences the electromagnetic near field of the metasurface. We further explore the tunability of such resonances with the design parameters of the structure and we demonstrate a potential application of it as a substrate for enhanced photoluminescence. In the third part of the thesis, we focus on the implementation of 2D photonic structures within the active layer of three different devices to improve performance. In particular we enhance the near infrared (NIR) photon harvesting efficiency in a colloidal quantum dot solar cell (PbS-CQD) and in organic photodetectors (P3HT: PC60BM and PBTTT: PC70BM) and improve the light out coupling from a nanophosphor layer (GdVO4:Eu3+ nanocrystals). We developed photonic systems tailored for each device and provide the complete optical and electronic characterization for each case. The nanostructuration with a 2D periodic arrangement renders the active layers with resonant waveguide properties enhancing its light trapping properties in the targeted spectral ranges, hence demonstrating the possibility to implement photonic schemes within actual devices.
Universitat Autònoma de Barcelona. Programa de Doctorat en Ciència de Materials
Ballesteros, Ribera Sandra. "New end-points to assess nanomaterials exposure effects." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673866.
Повний текст джерелаLos nanomateriales (NMs) son considerados contaminantes emergentes cuya detección está creciendo en las diferentes matrices ambientales, provocando riesgos potenciales para la salud humana y para los ecosistemas. En este sentido, el principal objetivo de esta Tesis ha sido proporcionar nuevas aproximaciones metodológicas para la evaluación del peligro de los NMs a través de modelos in vitro y ex vivo avanzados, así como de nuevos biomarcadores. En nuestro primer estudio se desarrolló un modelo novedoso para comprender el riesgo de exposición de los seres humanos a las nanopartículas de poliestireno (NPPS), como modelo de micro-nanoplásticos (MNPL). Para ello, las muestras de sangre procedentes de 5 donantes se expusieron ex vivo a varias dosis de NPPS y se evaluaron diferentes biomarcadores en diversos subconjuntos de glóbulos blancos periféricos. Los resultados mostraron marcadas diferencias en la internalización de NPPS, con una absorción muy limitada en los linfocitos y muy alta en los monocitos. Además, la evaluación del daño genotóxico del ADN reveló una sensibilidad celular específica, siendo las células polimorfonucleares y monocitos aquellas células con los niveles más significativos de daño genotóxico. Además, la exposición a NPPS desencadenó cambios en el secretoma sanguíneo, con un aumento significativo en la expresión de citoquinas relacionadas con la respuesta inflamatoria e inmunitaria, el estrés y la proliferación celular. En el segundo estudio, se utilizó el modelo ex vivo antes mencionado para evaluar el impacto a nivel del secretoma sanguíneo de tres nanomateriales diferentes basados en grafeno (NMBG). Para ello, se analizó un gran panel de citoquinas y los resultados mostraron importantes cambios en su expresión, estando la mayoría de ellos relacionados con la respuesta inmunitaria e inflamatoria. Al mismo tiempo, se utilizó el ensayo de soft-agar indirecto para analizar las consecuencias funcionales de estos cambios de citoquinas. Los resultados mostraron que el secretoma alterado por NMBG puede inhibir la capacidad de crecimiento celular independiente del anclaje de las células HeLa, utilizadas como modelo de línea celular. En el tercer estudio, las propiedades de transformación celular del nanocerio se confirmaron mediante un modelo in vitro de dosis bajas a largo plazo. Se analizaron las propiedades relacionadas con las células madre cancerosas, el crecimiento independiente del anclaje y las capacidades de invasión, ya que se consideran características oncogénicas importantes impulsadas por la exposición a los NMs. Asimismo, se confirmaron sus posibles interacciones con el condensado de tabaco, como modelo de contaminante cancerígeno ambiental, mostrando una interacción positiva en la inducción de la transformación celular. Además, se evaluó una batería de microARNs relacionados con la adquisición del fenotipo tumoral, revelando que las nanopartículas de dióxido de cerio y la co-exposición producían una toxicidad potencial a nivel del transcriptoma. Finalmente, en nuestro cuarto estudio se evaluaron las posibles consecuencias epigenéticas de la exposición a largo plazo a nanopartículas de titanio y nanotubos de carbono de múltiples capas, específicamente los cambios en la expresión de microARNs. La batería de microARNs analizada reveló un gran impacto en el perfil de expresión de las células expuestas a ambos nanomateriales. Además, a partir de nuestra batería inicial, se seleccionó un pequeño conjunto de cinco microARNs como posibles biomarcadores de efecto después de la exposición a los NMs. Este conjunto fue probado en las líneas celulares BEAS-2B y MEF, previamente expuestas a largo plazo a diferentes NMs, mostrando efectos positivos en todas las muestras probadas, confirmando la idoneidad de esta batería.
Nanomaterials (NMs) are considered emerging pollutants that are increasingly detected in different environmental matrices, with potential risks for human health and the ecosystems. In this sense, the focus of this Thesis has been directed to provide new approach methodologies for hazard assessment of NMs via advanced in vitro and ex vivo models, as well as novel biomarkers. From our first study, a novel approach was developed to understand the risk of polystyrene nanoparticles (PSNPs) exposure for humans, as a model of micro-nanoplastics (MNPLs). Thus, ex vivo whole blood samples from 5 donors were exposed to several doses of PSNPLs and different end-points were evaluated in diverse subsets of white peripheral blood cells (WBCs). The results showed sharp differences in PSNPLs internalization with very limited uptake in lymphocytes and high uptake in monocytes. Moreover, the genotoxic DNA damage evaluation revealed a specific cellular sensitivity, being polymorphonuclear cells (PMNs), and monocytes those cells with the most significant levels of genotoxic damage. Additionally, PSNPLs exposure triggered changes in the whole blood secretome, with a significant increase in the expression of cytokines related to the inflammatory, immune, and stress response, as well as cell proliferation. In the second study, the before-mentioned whole blood ex vivo model was used to evaluate the impact of three different graphene-based nanomaterials (GBNMs) at the level of the blood secretome. For that purpose, a large panel of cytokines was analysed, and the results showed important cytokine expression changes, most of them related with the immune and inflammatory response. At the same time, the indirect soft-agar assay, was used to unravel the functional consequences of these cytokine changes. The results showed that the GBNMs-altered secretome can inhibit the anchorage-independent cell growth capacity of HeLa cells, used as a model cell-line. In the third study, the cell-transforming properties of nanoceria were confirmed through a long-term low-dose in vitro model. Stem-like properties, anchorage-independent growth, and invasion abilities were analysed as they are considered important oncogenic features driven by NMs exposure. Also, their potential interactions with cigarette smoke condensate (CSC), as a model of environmental carcinogenic pollutant were confirmed, showing a positive interaction in the induction of cell transformation. Besides, a battery of microRNAs related to the acquisition of the tumoral phenotype was assessed, revealing that cerium dioxide nanoparticles (CeO2NPs) and the co-exposure produced potential toxicity at the transcriptome level. Finally, our fourth study evaluated the potential epigenetic consequences of long-term exposure to titanium nanoparticles (TiO2NPs) and multi-walled carbon nanotubes (MWCNT), specifically the microRNAs expression changes. The analysed microRNA battery revealed a big impact on the expression profiling in cells exposed to both nanomaterials. Moreover, from our initial battery, a small set of five microRNAs were selected as potential biomarkers of effect after NMs’ exposures. This set was tested in BEAS-2B and MEF cells previously long-term exposed to different NMs, showing positive effects in all the tested samples, confirming the suitability of this battery.
Universitat Autònoma de Barcelona. Programa de Doctorat en Genètica
Stephan, Dietmar [Verfasser]. "Nanomaterialien im Bauwesen : Stand der Technik, Herstellung, Anwendung und Zukunftsperspektiven = Nanomaterials in civil engineering / Dietmar Stephan." Kassel : Kassel University Press, 2011. http://d-nb.info/1017995230/34.
Повний текст джерелаStarnes, Daniel L. "THE EFFECTS OF MANUFACTURED NANOMATERIAL TRANSFORMATIONS ON BIOAVAILABILITY, TOXICITY AND TRANSCRIPTOMIC RESPONSES OF CAENORHABDITIS ELEGANS." UKnowledge, 2016. http://uknowledge.uky.edu/pss_etds/74.
Повний текст джерелаDuart, Marcelo Adriano. "EFEITOS DA ADIÇÃO DE NANOTUBOS DE CARBONO E C-S-H PRECIPITADO NAS PROPRIEDADES DE NANOCOMPÓSITOS CIMENTÍCIOS." Centro Universitário Franciscano, 2017. http://www.tede.universidadefranciscana.edu.br:8080/handle/UFN-BDTD/576.
Повний текст джерелаMade available in DSpace on 2018-08-20T12:45:35Z (GMT). No. of bitstreams: 2 Tese_MarceloAdrianoDuart.pdf: 8331452 bytes, checksum: d69e28005ad96f39781d95f4cfc7f7fb (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2017-07-31
Civil construction industry has been developing technologically with the growth in the number of works in various sectors such as housing, transport, industry and infrastructure. This study is intended to contribute to the development of scientific cementitious materials by studying the use of carbon nanomaterials as carbon nanotubes (CNT) and nanoparticles of Hydrated Calcium Silicate (C-S-H) incorporated into the matrix of these materials, which can be categorized as composite, in this case nanocomposites. Materials performance is usually related to the existence of considerable flaws or deficiencies in some properties or characteristics. The incorporation of nanomaterials is a possibility for the amelioration or even create some characteristic and materials property. The use of CNT has already been investigated and the results have shown that though with increase of costs produced materials have positive characteristics such compression and tensile resistance increase and still elasticity modulus increase. Currently steel is used but the fibers and filler materials such as CNT may be an alternative because they can have tensile strength up to 100 times higher than steel, as recent research has shown. The main assumption is that nanoparticles such as C-S-H and oxidized multi walled carbon nanotubes (MWCNT-OX) favor the kinetics of cement hydration and contribute to the nucleation and crystal growth enhancing material characteristics produced as concrete and mortar, for example. In general, it was verified that the combined additions of C-S-H with Ca / Si = 0.8 ratio with nanotubes brought positive results of nanocomposite nanostructure improvements, verified by porosity, permeability analysis and qualitative analysis of electron microscopy images. An increase in the value of the mechanical properties analyzed was shown as a 33% increase in compressive strength, 38% increase in modulus of elasticity and 30% in tensile strength. It is also concluded that using the C-S-H addition with Ca/Si ratio = 0.8 in isolation is a viable alternative to produce relevant results with a lower cost than to opt for mixed additions, since CNT are still materials with high cost and more complex production than C-S-H.
A construção civil vem se desenvolvendo tecnologicamente acompanhando o crescimento do número de obras em vários setores como habitacional, transportes, industrial e infraestrutura. Este projeto pretende contribuir cientificamente para o desenvolvimento de materiais cimentícios através do estudo da utilização de nanomateriais de carbono como nanotubos de carbono (NTC) e também nanopartículas de Silicato de Cálcio Hidratado (C-S-H) incorporadas à matriz destes materiais, que podem ser classificados como compósitos, neste caso nanocompósitos. O desempenho dos materias normalmente está relacionado a existência de falhas ou deficiências consideráveis em algumas propriedades e caracteristicas. A incorporação de nanomateriais é uma possibilidade para o melhoramento ou até mesmo a criação de alguma característica ou propriedade em determinados materiais. A utilização de NTC já vem sendo pesquisada e os resultados têm demonstrado que, embora com elevação dos custos, os materiais produzidos apresentam características positivas como: aumento da resistência à compressão e flexão e também do módulo de elasticidade. Atualmente usa-se o aço e fibras mas a adição de materiais como NTC pode ser uma alternativa, pois estes podem apresentar resistência à tração até 100 vezes maior que o aço, conforme pesquisas recentes já demonstram. A hipótese principal é que nanopartículas de C-S-H e também NTC favorecem a cinética de hidratação de cimentos e contribuem para a nucleação e crescimentos de cristais de produtos hidratados melhorando características dos materiais produzidos como por exemplo: concretos e argamassas. De forma geral, verificou-se que as adições combinadas de C-S-H com relação Ca/Si=0,8 com nanotubos de carbono paredes múltiplas oxidados (NTCPM-OX) trouxeram resultados positivos de melhoria na nanoestrutura dos nanocompósitos produzidos, verificados pela análise da porosidade, permeabilidade e também pela análise qualitativa de imagens de microscopia eletrônica. Veficou-se aumento do valor das propriedades mecânicas analisadas como 33% de aumento da resistência à compressão, 38% de aumento do módulo de elasticidade dinâmico e 30% da resistência à tração. Conclui-se ainda que usar a adição de C-S-H com relação Ca/Si=0,8 de forma isolada é uma alternativa viável produzindo resultados relevantes com um custo mais baixo que optar por adições mistas, visto que ainda os NTC são materiais com custo elevado e produção mais complexa do que o C-S-H.
Jacinto, Marcos José. "Desenvolvimento de catalisadores magneticamente recuperáveis para reações de hidrogenação em fase líquida." Universidade de São Paulo, 2010. http://www.teses.usp.br/teses/disponiveis/46/46134/tde-26112010-100424/.
Повний текст джерелаA core-shell superparamagnetic catalytic support comprised of magnetite nanoparticles recovered by silica was obtained using a reverse microemulsion. The material was used as a framework for anchoring transition metal cations that were used for the fabrication of Rh(0), Pt(0) and Ru(0) nanoparticles. The catalysts were employed in the hydrogenation of alkenes and ketones in liquid phase and they showed to be easily recoverable from liquid systems by placing a small neodymium magnet on the reactor wall. The magnetic separation technique provided a complete isolation of the catalyst from the liquid phase containing the products. It also made the use of other separation techniques, commonly used in achieving product separation in liquid-solid heterogeneous systems, such as filtration and centrifugation completely unnecessary. The surface of the silica support was modified with an aminosilane leading to a substantial increasing in the metal uptake from aqueous solutions of Rh, Pt and Ru salts. The hydrogenation reactions were carried out using molecular hydrogen as the reducing agent and they did not require any drastic reducers such as metal hydrides that would go against the principles of green chemistry. The stability of the catalysts were evidenced by the outstanding recycling properties. A single portion of the Rh0 catalyst for instance could be used for up to 20 times in the hydrogenation of benzene (TON: 10,240), and no significant loss in the catalytic activity was observed giving TOF values of up to 1167 h-1. Leaching of active catalytic species which is commonly encountered in heterogeneous solid-liquid systems was also absent in the hydrogenation reactions studied and this finding can be attributed to the mild reaction conditions used, the adherence of Rh, Pt and Ru nanoparticles to the magnetic support functionalized with NH2- groups and the efficient magnetic separation method used in isolating the product that dismiss the use of extra solvents and more aggressive separation methods such as a centrifugation.
Papa, Letizia. "Synthesis of hybrid nanosheets of graphene oxide, titania and gold and palladium nanoparticles for catalytic applications." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-19062017-083751/.
Повний текст джерелаA nanocatálise surgiu nas últimas décadas como uma interface entre catálise homogênea e heterogênea, oferecendo soluções simples a problemas que os materiais convencionais não conseguiram resolver. De fato, o design de nanocatalisadores permite obter estruturas com grande área superficial, reatividade e estabilidade, e ao mesmo tempo apresentando boa seletividade e facilidade de separação de misturas reacionais. Neste trabalho apresentamos a preparação de estruturas híbridas compostas por nanopartículas de ouro, paládio e prata (Au, Pd e Ag NPs), nanofolhas de titanato (TixO2), óxido de grafeno (GO) e óxido de grafeno parcialmente reduzido (prGO). Focamos em híbridos do tipo M/TixO2, M/(pr)GO e M/TixO2/(pr)GO (M = Au, Pd ou Ag) e desenvolvemos métodos de preparação simples, versáteis e ambientalmente amigáveis, com ênfase no controle sobre tamanho, forma e composição. Para explorar as potencialidades catalíticas utilizamos a redução do 4-nitrofenol como reação modelo, e em seguida a oxidação assistida por luz do p-aminotiofenol (PATP). Com esses testes, investigamos interações metal-suporte e efeitos cooperativos que tornam as estruturas hibridas superiores a cada um dos materiais que as compõem.
Bhuiyan, Md Atiqur Rahman. "An integrated experimental and finite element study to understand the mechanical behavior of carbon reinforced polymer nanocomposites." Diss., Georgia Institute of Technology, 2013. http://hdl.handle.net/1853/52187.
Повний текст джерелаSkalička, Jiří. "Využití nanotechnologií v jaderné energetice." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2013. http://www.nusl.cz/ntk/nusl-220180.
Повний текст джерелаBerenguel, Alonso Miguel. "Lab on a chip systems for biochemical analysis, biology and synthesis: towarda simple, scalable microfabrication technolgies based on COC and LTCC." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/458140.
Повний текст джерелаLa tecnología Lab on a Chip ha experimentado un extraordinario crecimiento en las dos últimas décadas, gracias al desarrollo de nuevas tecnologías de microfabricación y al conocimiento más profundo de los fenómenos físicos dominantes a la microescala. Los sistemas LOC presentan diversas ventajas sobre los sistemas macroscópicos análogos: transporte de energía y materia más eficientes, miniaturización, automatización, integración, alta densidad de información, entra otras. Estas ventajas han llamado la atención de una amplia comunidad científica y tecnológica, relacionada con campos de aplicación tan distintos como la química, la biología, la medicina y la nanotecnología. No obstante, el campo se encuentra todavía en una fase de desarrollo, tal como demuestra el limitado número de aplicacions LOC en el mercado. Es necesario afrontar diversos retos para superar esta barrera. Por un lado, los sistemas LOC deben integrar todas las operaciones necesarias para cada aplicación en cuestión, y al mismo tiempo, proporcionar una interfaz simple a los usuarios. Además, los sistemas LOC deben superar significativamente las prestaciones de sus análogos macroscópicos para justificar la inversión en una nueva tecnología. Por otro lado, los materiales y sus tecnologías de fabricación asociadas deben proporcionar la manera de producir tales dispositivos, tanto a nivel de prototipado como de fabricación en masa. Por tanto, al desarrollar sistemas LOC debe tenerse en cuenta la escalabilidad de los procesos de fabricación, y de esta manera, abordar el obstáculo que supone la transición a fabricación en masa. Esta tesis se centra en el desarrollo de dispositivos LOC utilizando procesos de fabricación escalables basados en una aproximación multicapa. Estos sistemas LOC se han destinado a tres aplicaciones muy diferentes, ejemplo de como campos tan alejados pueden beneficiarse de esta tecnología. Los requerimientos específicos de cada aplicación han determinado la selección del material más adecuado y la integración de los elementos necesarios en el sistema LOC. El primer caso consiste en el desarrollo de un dispositivo LOC fabricado con Co-polímero de Olefina Cíclica (COC), así como un actuador magnético para el control y la manipulación de partículas magnéticas dentro del dispositivo. Este sistema analítico fue utilizado para la detección de la bacteria patógena E.~coli O157:H7, demostrando una significativa mejora de la sensibilidad y una gran facilidad de operación. El segundo ejemplo también se basa en un dispositivo de COC, en este caso, para retener y madurar oocitos. Este sistema demostró su idoneidad para aplicaciones de reproducción asistida. Asimismo, la integración de calentadores transparentes en estos sistemas sienta la base para el desarrollo de plataformas de cultivo/fertilización totalmente independientes. En ambos ejemplos, el COC proporciona ventajas significativas como por ejemplo, una alta transparencia, baja autofluorescencia y biocompatibilidad. El último caso consiste en el desarrollo de microreactores fabricado con cerámicas de sinterización a baja temperatura (LTCC por sus siglas en inglés). Éstos se destinaron a la intensificación de procesos sintéticos de nanomateriales diseñados para aplicaciones analíticas. Este sustrato y su tecnología de fabricación asociada permiten la integración monolítica de calentadores, estructuras complejas 3D y ventanas ópticas. Se sintetizaron nanopartículas de Magnetita y Carbon Dots bajo duras condiciones de reacción, aprovechando la estabilidad química y estructural del material LTCC. Los resultados presentados en esta tesis demuestran la versatilidad de la tecnología LOC y las ventajas que proporciona a un amplia abanico de aplicaciones. Además, las metodologías de fabricación desarrolladas podrían ser potencialmente extrapoladas a procesos de fabricación en masa, hecho de gran importancia para la transferencia de tecnolgía hacia las aplicaciones comerciales e industriales.
Lab on a Chip (LOC) technology has experienced a remarkable growth in the last two decades, owing to the development of novel microfabrication technologies and the better understanding of physical phenomena at the microscale. LOC systems present several advantages over conventional macroscopic systems: enhanced mass and energy transport, miniaturization, automation, integration and throughput, among others. These advantages have drawn the attention of a wide scientific and technological community, related to very different application areas such as chemistry, biology, medicine and nanotechnology. However, the field is still in a development stage, as proven by the limited number of LOC products in the market. Different challenges need to be addressed to overcome this issue. On the one hand, the LOC system should integrate all the required operations for a given application, while keeping a simple interface for the end-users. Moreover, LOC systems should significantly outperform existing macroscopic analogues in order to justify the required investment in a new technology. On the other hand, materials and fabrication technologies need to provide the means to achieve that, both at a prototyping and mass production levels. Therefore, the scalability of the fabrication process should also be considered in order to bridge the gap between research prototyping and commercial production. This dissertation is focused on the development of LOC devices using scalable processes based on multilayer fabrication approaches. These LOC systems are targeted at very different applications, examples of how different fields can benefit from this technology. The specific requirements of each application have driven the selection of the substrate and the integration of the necessary elements on the LOC systems. The first case consists on the development of a LOC device using Cyclic Olefin Co-polymer (COC) as substrate and a simple magnetic actuator for the control and actuation of Magnetic Beads \emph{on-chip}. This analytical system was devoted to the detection of pathogenic E.~coli O157:H7 whole cells, demonstrating an enhanced performance and simple operation. The second example is also based on a COC device, in this case, to trap and culture oocyte cells. This LOC system demonstrated its suitability for Assisted Reproductive Technology applications. Moreover, the integration of transparent heaters lays the grounds for a fully independent culture/fertilization platform. In both cases, COC provides significant advantages such as high transparency, low autofluorescence and biocompatibility. The last case consists on the development of Low Temperature Co-fired Ceramics (LTCC) microreactors for the synthetic process intensification of nanomaterials designed for analytical applications. This substrate and its associated fabrication technology enabled the monolithic integration of heaters, complex 3D-structures and optical windows. Magnetite nanoparticles and Carbon Dots were synthesized under harsh reaction conditions, taking advantage of the chemical and structural stability of the LTCC substrate. The results presented in this dissertation demonstrate the versatility of LOC technology and the advantages that it provides in a wide range of applications. Moreover, the fabrication methodologies developed could potentially be extrapolated to a mass production scale, which is of paramount importance for the technology transfer to commercial and industrial applications.
Mesquita, Paulo Roberto Ribeiro de. "Síntese via rota sonoquímica e caracterização de nanopartículas de sulfeto de bismuto." reponame:Repositório Institucional da UFBA, 2013. http://www.repositorio.ufba.br/ri/handle/ri/13088.
Повний текст джерелаSubmitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2013-10-02T13:52:06Z No. of bitstreams: 1 Dissertação_Impressão FINAL.pdf: 23959288 bytes, checksum: 4ba5e564089149b8fafe9a4c74558367 (MD5)
Approved for entry into archive by Ana Hilda Fonseca(anahilda@ufba.br) on 2013-10-02T14:12:03Z (GMT) No. of bitstreams: 1 Dissertação_Impressão FINAL.pdf: 23959288 bytes, checksum: 4ba5e564089149b8fafe9a4c74558367 (MD5)
Made available in DSpace on 2013-10-02T14:12:03Z (GMT). No. of bitstreams: 1 Dissertação_Impressão FINAL.pdf: 23959288 bytes, checksum: 4ba5e564089149b8fafe9a4c74558367 (MD5) Previous issue date: 2013
O sulfeto de bismuto faz parte da família de compostos do tipo A2VB3VI formados por calcogênios e metais (sendo A= Sb, Bi. B= S, Se, Te) que se destacam por suas propriedades semicondutoras. O Bi2S3 forma um sólido de coloração preta de solubilidade muito baixa em água, possuindo energia de band gap na faixa de 1,3 a 1,7 eV, com potencial para aplicações nas áreas de optoeletrônica e fotocatálise, entre outras. As propriedades físicas e químicas de nanopartículas de Bi2S3, e outros nanomateriais, são fortemente dependentes de diferentes tamanhos e morfologias dos nancristais. Este trabalho teve como objetivo desenvolver um método sonoquímico para produção de nanopartículas de Bi2S3. Utilizou-se os reagentes Bi(NO3)3 e Na2S2O3 como precursores dissolvidos em solvente orgânico contendo o surfactante brometo de cetiltrimetilamônio (CTAB), sendo o meio reacional exposto a irradiação de ultrassom de alta intensidade, através de um sistema com sonda de titânio e imersão direta. As nanopartículas de Bi2S3 obtidas foram caracterizadas por difração de raios X (XRD), microscopia eletrônica de varredura (MEV) e microscopia eletrônica de transmissão (TEM). O método sonoquímico foi otimizado através do planejamento fatorial completo em dois níveis, onde se verificou que os parâmetros ciclo das ondas ultrassônicas e tempo influenciam significativamente no rendimento da reação. Fixando-se o ciclo em 80% e a amplitude em 20%, verificou-se que no tempo de reação de 15 min foram obtidas as nanopartículas com menor diâmetro médio (11,8 nm) e cristalinidade satisfatória. O método sonoquímico (15 min) foi comparado com o método de aquecimento convencional sob refluxo (90 min), mostrando-se mais rápido e eficiente na obtenção de nanopartículas com alta homogeneidade morfológica. O método sonoquímico produziu superestruturas tipo flor (3D) formadas pela agregação de nanobastões de Bi2S3 com diâmetro médio em torno de 11-15 nm. A morfologia e a qualidade dos nanocristais mostraram-se dependentes do tipo de solvente empregado na síntese. Superestruturas em 3D semelhantes a flores foram obtidas quando etilenoglicol puro foi usado como solvente, enquanto estruturas em 1D na forma de nanobastões foram obtidas quando se utilizou uma mistura de dimetilsulfóxido e etilenoglicol. Foi proposto um mecanismo para a síntese sonoquímica do Bi2S3 e os papéis do solvente e do surfactante nesta síntese foram discutido
Salvador
Contreras, Rodríguez Ada Rebeca. "Removal of cadmium (II), lead (II) and chromium (VI) in water with nanomaterials." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/328421.
Повний текст джерелаA great challenge for this century lies in cleaning-up the waste generated during industrial, domestic and agricultural activities. Water, as vital part of the life cycle is heavily affected by these activities and eventually, turns it unusable. Among the numerous contaminants found in water, heavy metals require special attention, as they are non-biodegradable, and often accumulate in the environment causing both short and long term adverse effects, even at low concentrations. The adsorption process proved to be economically feasible and efficient over other technologies, especially for removing pollutants from dilute solutions. In this sense new adsorbents based on nanomaterials are being extensively studied. With this in mind, the development of new, efficient and low cost nanomaterials for their application in water/wastewater has been of great interest in the last years, due to the special properties such as high reactivity and strong sorption. In this framework, the feasibility of using different nanomaterials for the removal of cadmium (II), lead (II) and chromium (VI) dissolved in water has been studied. The nanomaterials used could be grouped into three main groups: i) metal oxides nanoparticles (NMOs), cerium oxide (CeO2) titanium oxide (TiO2) and iron oxide (Fe3O4), ii) polymer, catechol-based nanoparticles (NPs) and iii) graphene oxide (GO)-based nanomaterials, CeO2 NPs attach to reduced graphene oxide (RGO). The viability of using NMOs for the adsorption of dissolved Cd (II) was tested obtaining the adsorption and kinetics parameters. CeO2 NPs also were tested with different operational parameters, two different pH and in single and multicomponent system. The catechol-based NPs adsorption experiments were performed at par with activated carbon, obtaining the higher adsorption capacity with the NPs. Bioluminescent test and cytotoxic assays also were performed in order to assess the toxicity of the nanomaterial. Finally, GO and CeO2/RGO nanomaterials were characterized and tested in adsorption process. The attachment of CeO2 to GO follow two different strategies, in situ-growth and self-assembly approach. In conclusion, nanomaterials showed promising results in the removal of heavy metals, and in this way is reaffirmed once again that nanomaterials can be used as effective adsorbents for water/wastewater treatment.
Álvarez, Prada Luis Ignacio. "Ruthenium and Platinum Nanoparticles For Artificial Photosynthesis." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673692.
Повний текст джерелаLa creciente demanda energética, necesaria para cubrir las necesidades de una población cada vez más numerosa, ha acelerado el cambio climático en las últimas décadas, debido al empleo predominantemente de combustibles fósiles, que además de contaminantes son finitos y están mal distribuidos globalmente. Esto ha propiciado el interés por emplear energías más limpias. Así, tomando la naturaleza como ejemplo, surge la Fotosíntesis Artificial, una forma de almacenar la ingente energía solar que recibimos en la Tierra en forma de enlaces químicos en diferentes sustancias. Este proceso incluye, además de la oxidación de agua a dioxígeno, la reacción de reducción de protones y la reducción de CO2, obteniéndose, respectivamente, dihidrógeno y productos derivados del carbono como metano o metanol. En ambos casos se requiere el empleo de un catalizador para hacer el proceso eficiente, y un material fotoactivo que desencadene el proceso inducido por la luz. En el Capítulo I, se desarrolla aún más la problemática del cambio climático y el estado actual de los procesos de reducción de protones y CO2, señalando el empleo de semiconductores como el nitruro de carbono como material fotoactivo y de nanopartículas metálicas como catalizadores. Se destaca, además, el empleo del método organometálico para la preparación de estos catalizadores, en condiciones suaves de reacción y con un gran control sobre sus características físicas y químicas. En el Capítulo II, se exponen los objetivos de este trabajo, centrados en el diseño, caracterización multitécnica y uso de materiales basados en nanopartículas metálicas para llevar a cabo estos procesos. En el Capítulo III, se preparan nanopartículas de rutenio empleando diferentes ligandos como estabilizadores, observando diferencias en su actividad y estabilidad electrocatalítica en la reducción de protones, relacionados con sus propiedades y composición. En el Capítulo IV, se emplea carburo de nitrógeno grafítico mesoporoso (mpg-CN) como material fotoactivo para la reducción fotoinducida de CO2. Se comprueba el efecto que tiene la incorporación de nanopartículas de platino al semiconductor, mejorando notablemente la eficiencia y la selectividad del proceso. En el Capítulo V, vuelve a utilizarse mpg-CN pero con nanopartículas de rutenio y platino para la fotorreducción de protones. Las nanopartículas de rutenio se preparan de diferentes maneras, utilizando ligandos estabilizadores, materiales de carbono o directamente en el semiconductor. Se comprueba que, independientemente de la técnica, la eficiencia catalítica observada es similar en todos estos sistemas, y muy inferior a la obtenida con Pt. Las observaciones catalíticas se respaldan con estudios fotofísicos. En el Capítulo VI, se perparan nanopartículas de Pt soportadas en cuatro materiales de carbono diferentes (nanohorns y nanotubos de carbono, óxido de grafeno reducido y grafito), que son incorporadas a un sistema de detección electroanalítica, mostrándose eficaces para la detección de parabenos a niveles de ultratraza. Finalmente, en el Capítulo VII se exponen las conclusiones globales.
The increasing energy demand, necessary to meet the needs of the growing world population, has accelerated climate change in recent decades, due to the predominantly use of fossil fuels, which in addition to being pollutants are non-renewable and ill-distributed. This has aroused interest in cleaner energetic alternatives. Thus, taking Nature as an example, Artificial Photosynthesis emerges as a way to store the enormous amount of solar radiation received by the Earth, in the form of chemical bonds of a fuel. This process includes, besides the oxidation of water to dioxygen, the reduction of protons and the reduction of CO2, obtaining, respectively, dihydrogen and products derived from carbon such as methane or methanol. In both cases, the use of a catalyst is required to make the process efficient, and a photoactive material that triggers the process induced by light. Chapter I further develops the problem of climate change and the current state of the proton and CO2 reduction processes, pointing out the use of semiconductors such as carbon nitride as photoactive material and metallic nanoparticles as catalysts. In addition, the use of the organometallic method for the preparation of these catalysts is highlighted, under mild reaction conditions and with great control over their physical and chemical features. In Chapter II, the objectives of this work are exposed, centered on the design, multi-technique characterization and testing of materials based on metallic nanoparticles to carry out these processes. In Chapter III, ruthenium nanoparticles are prepared using different ligands as stabilizers, observing differences in their activity and electrocatalytic stability in the reduction of protons, related to their physical properties and composition. In Chapter IV, mesoporous graphitic nitrogen carbide (mpg-CN) is used as a photoactive material for photoinduced CO2 reduction. The effect of the loading of platinum nanoparticles to the semiconductor is tested, notably improving the efficiency and selectivity of the process. In Chapter V, mpg-CN is used again but with ruthenium and platinum nanoparticles for the photoreduction of protons. Ruthenium nanoparticles are prepared in different ways, using stabilizing ligands, carbon materials or directly deposited in the semiconductor. It is found that, regardless of the technique, the observed catalytic efficiency is similar in all these systems, and much lower than the performance of Pt. The catalytic observations are supported by photophysical studies. In Chapter VI, Pt nanoparticles supported on four different carbon materials (carbon nanohorns, carbon nanotubes, reduced graphene oxide and grahpite) are prepared and incorporated into an electroanalytical sensing platform, proving effective for the detection of parabens at ultra-trace levels. Finally, in Chapter VII the global conclusions are presented.
Universitat Autònoma de Barcelona. Programa de Doctorat en Química
Sethi, Manish. "INTERACTIONS AND EFFECTS OF BIOMOLECULES ON AU NANOMATERIAL SURFACES." UKnowledge, 2011. http://uknowledge.uky.edu/gradschool_diss/822.
Повний текст джерелаFilho, Paulo Cesar de Sousa. "Estudos sobre síntese, propriedades estruturais e espectroscópicas de oxossais de terras raras para aplicações como luminóforos de ultravioleta de vácuo." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-25072013-095144/.
Повний текст джерелаThe rare earth elements (RE) have figured in the academic scenario for over two centuries, being an integral part of most up-to-date developed technologies in several fields of expertise. Regarding the applications of luminescent materials over the last years, the unique spectroscopic properties of RE elements have made them almost irreplaceable in classic tricolor devices, such as compact fluorescent lamps or cathode ray tubes. Nevertheless, the advent of new visualization and lighting technologies, like the high-resolution compact displays and the elimination of mercury from fluorescent lamps, has stimulated scientists to investigate the synthesis and properties of RE-based phosphors. In this work, we have evaluated the processes available for the synthesis of nanostructured RE phosphates and vanadates capable of acting as phosphors under vacuum ultraviolet excitation, and conducted the structural and spectroscopic characterization of these materials. We used three strategies to prepare the solids: the polymeric precursor method (Pechini), precipitation into reverse microemulsions, the colloidal precipitations. These methods can be adapted to the synthesis requirements and enable the control of morphology, composition and particle aggregation, thus constituting highly efficient ways to obtain nanostructured RE phosphates and/or vanadates. We synthesized orthophosphates (REPO4), phosphovanadates (REP1-xVxO4), and core@shell structures (REVO4@REPO4) with different composition, to generate of red, green, and blue phosphors, as well as solids with upconversion emissions. We characterized the prepared compounds by X-ray diffractometry, electron microscopy, dynamic light scattering, thermal analysis, and vibrational and luminescence spectroscopies (emission/excitation, luminescence lifetimes, quantum yields, chromaticity, and Judd-Ofelt intensity parameters).
Pereira, Maria Luiza de Oliveira. "Asfalteno: um desafio para indústria de petróleo e a busca de soluções pela nanociência." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/46/46136/tde-12042018-103610/.
Повний текст джерелаAsphaltenes are composed by polycyclic aromatic hydrocarbons that belong to one of the most polluting and carcinogenic chemical classes. They are well known for forming hard scales that obstruct pipelines and may even lead to the well shut down. They can constitute up to 20% of petroleum, which still remains the main source of energy used in our planet. At the present time, asphaltenes are converted into asphalt and coke by destructive distillation, in spite of the high cost and polluting technology involved, which employs high temperatures and releases sulfur compounds into the atmosphere. However, their conversion into more valuable raw materials, for instance, by photocatalytic or oxidative cracking using suitable catalysts, would be a better, more economic option. In recent years, nanotechnology has been incorporated into oil research, opening new economic and environmental perspectives, including the improvement and recovery of heavy oils. In general, nanomaterials have the advantage of being better dispersed and exhibiting differentiated properties in relation to the bulk. In this study the interactions between asphaltenes and different nanomaterials exhibiting remarkable magnetic, optical, and electronic properties, such as iron oxide nanoparticles (Nmag), hybrids of gold nanoparticles with reduced graphene oxide (RGO@AuNP) and the gold nanorods (AuNRs) respectively were investigated. The interactions between asphaltenes and Nmags with different surface-passivating ligands (C8H20O4Si and C6H17NO3Si) were made by performing isotherms curves and adsorption tests, revealing the types of binding between these materials, their coverage and the adsorptive capacity. The nanoparticle coating and the asphaltene concentration influence the adsorption. Theinteraction was stronger using the free Nmag, indicating coordination of the iron with the aromatic rings of the asphaltene, having a monolayer cover. Functionalized Nmags interact by intermolecular forces with asphaltenes, having a multilayer coverage. At high concentrations of asphaltene in toluene, the adsorption was more effective for the functionalized Nmags, since the coordination with the iron was hampered due to the formation of reverse micelle, prevailing the hydrophobic interactions. There was a drastic reduction in the asphaltene cracking temperature in the presence of Nmags, bigger than 100ºC, showing its potential on the oxidative catalysis of asphaltenes. The interactions of RGO@AuNP and AuNR materials with asphaltene films were investigated by dark field hyperspectral microscopy. As a result there was a shift and a broadening of the band in the electronic spectrum, indicating the occurrence of charge transfer between the species. From this, photocatalysis were performed with the RGO@AuNP, at room temperature, under visible light, using 9-antraldehyde (9-ATA) as a model compound for asphaltene. The reaction leads to the formation of cyclic endoperoxides that undergo further reactions, resulting in their cleavage, with 90% yield for the 9-ATA degradation. Finally, a mechanistic study was carried out using a fluorogenic sensor of reactive oxygen species to evaluate the photocatalytic activity of RGO@AuNP. It was showed that photoinduced electron transfer from AuNP to RGO can occur in ~11 fs time scale, with a quantum yield of ~35%, and superoxide radicals anions (O2•-) can be generated by synergistic effects after the hybrid photoexcitation.
Camargo, Marcelo de. "Estudos preliminares sobre a produção de nanocelulose a partir de algodão "Never Dried" utilizando hidrólise enzimática seguida de sonicação com ultrassom." [s.n.], 2010. http://repositorio.unicamp.br/jspui/handle/REPOSIP/266921.
Повний текст джерелаDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Química
Made available in DSpace on 2019-01-18T11:50:46Z (GMT). No. of bitstreams: 1 Camargo_Marcelode_M.pdf: 25344897 bytes, checksum: 8146c1fb634f94d4bb4152d5bcc07e66 (MD5) Previous issue date: 2010
Resumo: Este estudo trata-se de um novo método de obtenção de fibras de nanocelulose a partir de algodão "Never Dried Cotton" NDC, (algodão nunca seco). O algodão classificado como NDC, apesar de possuir a mesma cristalinidade do algodão normal e muito mais poroso e, portanto, muito mais suscetível a eventuais tratamentos químicos. Esta maior porosidade deve-se ao fato de que o NDC, no seu estado natural, ainda não passou pelo processo de colapso do lumen devido a evaporação da seiva presente no seu interior. Com este colapso da estrutura, as inúmeras pontes de hidrogênio formadas entre as hidroxilas da celulose estabelecem-se em um arranjo molecular diferente do NDC, e neste novo arranjo os poros fecham-se irreversivelmente, num processo que na área de celulose chama-se "hornification", que diminui a acessibilidade da celulose. Neste trabalho aplicamos uma hidrolise enzimática seguida da sonicação com ultrasom de 400 e 1000 W de potencia, submetendo as amostras a 20, 30, 40, e 50 minutos de tratamento com ultrasom. As analises de microscopia eletrônica revelaram fibras com comprimento médio de aproximadamente 30 Fm e de ate 232 nm de diâmetro para a sonicação com ultrassom de 1000 W durante 50 minutos no algodão Never Dried. Na viscose com a mesma potencia e tempo de tratamento foram obtidas nano fibras de ate 197 nm. Para o ultrassom de 400 W obtivemos fibras com 800 nm de diâmetro apos 50 minutos de tratamento. Contudo somente com a microscopia de Transmissão eletrônica e que pudemos identificar a presença de nano fibras com ate 40 nm de diâmetro já com apenas 20 minutos de tratamento e utilizando o ultrassom de menor potencia de 400 W. As analises de medição de tamanho de partícula por laser demonstraram que as amostras obtidas com ultrassom de 1000 W são mais homogêneas em relação as suas dimensões.
Abstract: This study is about a new method of obtainning Cellulose nano fibers from cotton "Never Dried Cotton" NDC. The cotton classified as NDC, despite has the same cristalinity of the normal cotton it is much more porous and, therefore, much more susceptible to eventual chemical treatments. This higher porosity is because the NDC, in natural state, is not in process of collapse of the lumen due to evaporation of the sap in the interior of fiber. With the collapse of the structure makes the innumerable hydrogen links formed between cellulose hydroxyls to agroup themselves molecular arrangement different from NDC, and in this new arrangement the pores close on a irreversible way, in a process that in the cellulose field is called of "hornification", wich reduces the accessibility of the cellulose. In this work we apply an enzymatic hydrolysis followed the sonication with 400 and 1000 W power ultrasound, submitting the samples the 20, 30, 40, and 50 minutes of treatment with ultrasound. The analyses of electronic microscopy disclosed fibers with average length of approximately 30 Pm and up to 232 nm of diameter for the sonication with 1000 W ultrasound during 50 minutes in the Never Dried Cotton. Nano fibers of up to 197 nm were obtained from viscose, with the same power and time of treatment. Utilizing ultrasound of 400 W fibers with 800 nm of diameters were obtained after 50 minutes of treatment. However only with Transmission electronic Microscopy it was possible to identify the presence of nano fibers with up to 50 nm of diameter with only 20 minutes of treatment and using an ultrasound of 400 W power. The analyses of measurement of particle size with laser had disclosed that the samples gotten with ultrasound of 1000 W are more homogeneous compared to its dimensions.
Mestrado
Ciencia e Tecnologia de Materiais
Mestre em Engenharia Química
Nataša, Samardžić. "Анализа квантних механизама транспорта присутних у мемристивним уређајима на бази наноматеријала". Phd thesis, Univerzitet u Novom Sadu, Fakultet tehničkih nauka u Novom Sadu, 2016. https://www.cris.uns.ac.rs/record.jsf?recordId=101710&source=NDLTD&language=en.
Повний текст джерелаIstaživanja u okviru doktorske disertacije imaju za cilj da pruže doprinos dubljem razumevanju fizičkih mehanizama prisutnih kod memristora, s obzirom da u stručnoj literaturi i dalje postoje otvorena pitanja vezana za ključni proces koji indukuje memristivni efekat u materijalu. Kao funkcionalni materijal za memorije na bazi promene valence, na kom se ispituje memristivni efekat, odabran je titanijum dioksid jer se već pokazao kao dobar kandidat za rezistivno-prekidačke memorije. Eksperimentalni rezultati pokazuju efekat kvantizacije provodnosti za TiO2 memristore, što zahteva razvijanje i primenu modela balističkog transporta za opisivanje električnih karakteriristika uzorka.
Research topics in this PhD thesis aims to provide contribution in deeperunderstanding of physical mechanisms which drives resistive-switchingmechanism in memristors, as existing literature provides open questions forkey mechanism processes which influences memristive effect in materials. Inorder to test response of Valance Change Memories, TiO2 nanomaterial wasused as the functional layer, as this material was already shown suitable forthese applications. Measured results show conductance quantization effectfor TiO2 based memristors, which requiers ballistic transport model forinterpretation of electrical response of the device.
Xiao, Juan. "Development of electron tomography on liquid suspensions using environmental scanning electron microscopy." Thesis, Lyon, 2017. http://www.theses.fr/2017LYSEI050/document.
Повний текст джерелаESEM (Environmental Scanning Electron Microscopy) allows the observation of liquids under specific conditions of pressure and temperature. When working in the transmission mode, i.e. in STEM (Scanning Transmission Electron Microscopy), nano-objects can even be analyzed inside the liquid (“wet-STEM” mode). Moreover, in situ evaporation of water can be performed to study the materials evolution from the wet to the dry state. This work aims at developing electron tomography on liquid suspensions using STEM-in-ESEM, to obtain the 3D structure of nano-objects dispersed in a liquid. In a first part, Monte Carlo simulations and 2D wet-STEM experimental images are combined to study the contrast. Two kinds of liquid nano-materials are chosen as the sample: spherical gold particles (diameter around 40 nm) in suspension in water; latex SBA-PMMA suspension, a copolymer derived from styrene and metacrylic acid esters in aqueous solution, 3% PMMA shell included as steric surfactant. The comparison between simulated and experimental results helps to determine how water can affect the contrast of hydrated nano-materials. Tomography experiments are then performed on dry PU-carbon nanotubes nanocomposites using a previously developed home-made tomography device, and the volume is well reconstructed. When performing tomography on latex suspension, limitations are found on the temperature control of samples. We propose an optimization of the device with new observations conditions to better control water evaporation and condensation of liquid samples. Afterwards, a full 3D analysis on SBA-PMMA latex from dilute suspension to very concentrated one is performed, and a further study is presented in presence of a surfactant. The encouraging reconstruction results are used to model the particles arrangement. This shows the potentialities of wet-STEM tomography for the characterization of both solid and liquid nano-materials
Ferrando, Villalba Pablo. "Thermal characterization of Si-based nanostructures." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/399339.
Повний текст джерелаThermoelectricity is a promising technology for scavenging energy from environmental temperature differences. The development of materials that transform heat into electricity in a more efficient way making use of this principle is necessary for opening new application niches. Nanostructuring a material has been demonstrated to increase the thermoelectric figure of merit of crystalline materials via a thermal conductivity reduction driven by enhanced phonon scattering. This thesis is committed to give a better insight into the processes that affect thermal transport in potential Si-based nanomaterials for thermoelectric generation. In Chapter 1, a general introduction exposes the need for reducing fossil fuel consumption and generally using renewable energies. Also, the benefit of tuning the thermal conductivity of materials for thermal management applications is discussed. Chapter 2 provides an overview of the theory behind thermal transport. First, the heat equation is derived from the classical irreversible thermodynamics framework. Then, phonons are introduced as heat carrying quasiparticles. The application of the Boltzmann Transport Equation to both phonons and electrons allows understanding the effect of different scattering mechanisms on the thermoelectric properties of materials. Finally, several strategies for enhancing the figure of merit of materials are reviewed. In Chapter 3, the necessary tools for measuring the thermal conductivity of nanomaterials are developed. Two cryostats are set up along with the temperature control systems that allow measuring at stable temperatures. Later, three sensors are developed for measuring the thermal conductivity of different materials. First, suspended structures intended for measuring the in-plane thermal conductivity of suspended membranes and nanowires are fabricated, and the errors and uncertainties produced in such measurements are characterized. Second, the 3ω method is introduced, allowing the measurement of the out-of-plane thermal conductivity in thin films. The emergence of the 3ω voltage is demonstrated, and the relation between this voltage and the thermal conductivity of the substrate and the thin-film is found. Finally, a sensor for the 3ω-Völklein method is developed, which allows characterizing the in-plane thermal conductivity of thin-films during the layer growth. In Chapter 4, the thermal conductivity of suspended Si membranes is measured, finding the expected reduction in thermal conductivity due to phonon surface scattering, as well as confinement effects in the 17.5 nm thick membrane. Moreover, the nanopatterning of these Si membranes with focused ion beam (FIB) is optimized through a systematic study of its amorphization finding an optimal spatial resolution of 200 nm when using 50 μC/cm2. In Chapter 5, the thermal conductivity of porous Si nanowires is studied for wires with different porosity, length and diameters, showing an unexpected dependence on its diameter that suggests that the wire core is generally less porous than the shell. The structural Si thermal conductivity is found to be one fiftieth of that of the bulk, promising a good thermoelectric figure of merit. In Chapter 6, the thermal conductivity of a novel SiGe graded superlattice is measured, showing a considerable reduction in its thermal conductivity, even below the thin-film alloy limit. The measurement of the thickest superlattice confirms the absence of coherent phonon effects. In Chapter 7, the thermal conductance of a suspended SiNx membrane is measured with a high precision while depositing on it organic (TPD) and metallic (Indium) materials. The results show an initial conductance reduction that cannot be explained with the Fourier law. This reduction is found to be related to an increased diffusive boundary scattering, which could be easily extrapolated to other thermoelectric nanomaterials, reducing their thermal conductivity. Also, the growth dynamics of both materials are characterized through their signal in the conductance.
DI, MAURO VITTORIA. "Novel insights into the protective role of miR-133a in the heart and its therapeutic application for the treatment of cardiac pathologies." Doctoral thesis, Università degli Studi di Milano-Bicocca, 2017. http://hdl.handle.net/10281/170792.
Повний текст джерелаSo far, a plethora of studies demonstrated the importance of miRNAs, in embryo development and in the onset of basically all kinds of pathologies. In the cardiac system, the role of miR-133a was extensively characterized from embryogenesis to the development of cardiac defects. Nevertheless, much remains to be learned about the functions of miR-133. The main scope of my PhD thesis was to investigate these additional functions of miR-133 firstly in cardiac development, focusing on its potential ability to control signal pathways at the transcriptional level, and secondly in the already well characterized cardiac pathologies. Moreover, the ultimate goal of my research was to translate the additional roles of miR-133 into its therapeutic use by developing a new strategy that, based on the use of nanomaterials, allows for the specific and controlled delivery of miR-133 into the cardiac system.
Martinez, Jimenez Mawin Javier 1985. "Mecanismos de condução em filmes nanoestruturados de óxidos de grafeno." [s.n.], 2017. http://repositorio.unicamp.br/jspui/handle/REPOSIP/330593.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Instituto de Física Gleb Wataghin
Made available in DSpace on 2018-09-02T19:37:47Z (GMT). No. of bitstreams: 1 Jimenez_MawinJavierMartinez_D.pdf: 7578838 bytes, checksum: def5bc65d8270856f55d63211e1e0f09 (MD5) Previous issue date: 2017
Resumo: Para alcançar alto desempenho em dispositivos e aplicações faz-se necessário uma melhor compreensão do comportamento de materiais a base de grafeno em nanoescala para otimização de design e fabricação. A síntese química é uma excelente rota alternativa para produzir compósitos em nanoestruturas bem definidas de tamanhos semelhantes, garantindo propriedades elétricas reprodutíveis para aplicações confiáveis. O grafeno, na forma de pontos quânticos (QDs, do inglês quantum dots) em dimensão zero e nanofolhas (NPLs, do inglês graphene nanoplateletes) bidimensionais (2D), são materiais emergentes com funcionalidades únicas promissoras para novas aplicações. Neste trabalho apresentamos um estudo detalhado dos mecanismos de transporte em nanoestruturas formadas pela técnica de automontagem por adsorção física (LbL, do inglês Layer-by-Layer) na forma de multicamadas, com controle de espessura em nível molecular. Os filmes LbL foram formados por óxido de grafeno reduzido (rGO) funcionalizado com diferentes polieletrólitos tanto na forma de QDs quanto nanofolhas. As caracterizações elétricas indicaram corrente limitada pela carga espacial em algumas amostras, e em outras arquiteturas moleculares, mecanismo de condução via Poole-Frenkel seguindo a lei de Mott dominada por saltos variáveis. A flexibilidade da técnica LbL aliada à dimensão dos materiais utilizados foram favoravelmente exploradas como um ajuste fino para controle da mobilidade de portadores dentro das nanoestruturas formadas. Foi observado em alguns casos uma condução planar no interior da camada contendo rGOs na estrutura LbL com mobilidade eletrônica efetiva de ~ 35 cm² V^-1 s^-1. Em outros casos um mecanismo de condução 3D (interplanar ao longo de toda nanoestrutura LbL) com mobilidade eletrônica de ~ 151 cm² V^-1 s^-1. Medidas em função da temperatura indicaram alta probabilidade de saltos randômicos entre ilhas condutoras de rGO distribuídas ao longo da camada contendo os pontos quânticos, que contribui para um maior tempo de trânsito dos portadores e, consequentemente, mobilidades menores. O oposto ocorre para as nanofolhas de rGO, que requerem maiores energias de ativação devido ao tamanho e presença de defeitos, resultando em caminhos condutores maiores e com maiores mobilidades
Abstract: To achieve high-performance in devices and applications it is important a better comprehension of the behavior at nanoscale of graphene-based materials to promote a rational design and fabrication. The chemical synthesis is an excellent alternative route to optimize graphene-based composites in well-defined nanostructures of similar sizes, ensuring reproducible electrical properties for reliable applications. Graphene as quantum dots (QDs) and nanoplatelets (NPLs) presents emerging zero- and two-dimensional (2D) materials with promising unique functionalities to novel applications. We present here a detailed study of the charge transport mechanisms in multilayered nanostructures formed by physical adsorption through the layer-by-layer (LbL) technique, with molecular level thickness control. The LbL films were formed by reduced graphene oxides (rGO) functionalized with different polyelectrolytes and processed either as QDs or nanoplatelets. The electrical characterizations indicated a space-charge-limited current (SCLC) in some samples, while in other molecular architectures it was found a Poole-Frenkel conduction mechanism dominated by a Mott-variable range hoping model. The LbL assembly together with the dimensionalty of the materials could be favorably used as a fine tuning to control the charge carrier mobility inside the formed nanostructures. The flexibility of the LbL technique together with the dimensionality of the materials were favorably explored as a fine tuning of the charge carrier mobility inside the nanostructures. It was observed in some cases a 2D intra-planar conduction within the rGO layer in the LbL films, with an effective charge carrier mobility of ~ 35 cm² V-1 s-1, and in other cases a 3D conduction mechanism (interplanar along with the LbL nanostructure) with electronic mobility of ~ 151 cm² V-1 s-1. Temperature measurements indicated a higher probability of random jumps between rGO conducting "islands" distributed along with the plane layer having quantum dots, which contributes for a longer transit time of the carriers and, consequently, lower mobility values. The opposite occurred for the rGO nanoplatelets that required higher activation energy due to size and presence of defects, resulting in larger conductive pathways and higher mobilities
Doutorado
Física
Doutor em Ciências
1247719
CAPES
FAPESP
Gras, Charles Maria del Roser. "Síntesi i nanoestructuració de compostos fotoactius basats en perilendiimida." Doctoral thesis, Universitat Autònoma de Barcelona, 2015. http://hdl.handle.net/10803/286187.
Повний текст джерелаThe current Doctoral Thesis is divided into parts. The first part describes the development of luminescent materials that responds to external stimulus. It is important to note that this research area, which has emerged as an important area of research in the last years, includes the development of (bio)chemical devices for sensing and imaging and systems for information processing and storage. In this sense, the Doctoral Thesis shows the preparation of new multifunctional switchable systems that are sensitive to different stimulus. These new molecular systems are based on two units, which are covalently linked, the perylenediimide unit (PDI, electron acceptor moiety) and the switchable unit (dithienylethylene and stilbene, electron donor moiety). The quenching of the fluorescent properties of one of the two states of those molecular switches is triggered by applying different external stimulus such as protons, electricity or light. The second part of the Doctoral Thesis is devoted to the fabrication of onedimensional (1D) micro- and nanostructures made of self-assembled π- conjugated molecules. One of the most promising and an active of research fields due to the fabrication and miniaturization of opto-electronic devices, e.g. sensors and solar cells. For this study it is decided to build multicomponent materials by self-assembly of molecular systems based on a perylenediimide unit and the switchable unit (stilbene). The preparation of those compounds composed by electron donor and acceptor moieties may display good photoconductivity properties for being applied in photovoltaics. The present work also shows that the shape (nanorod and nanotubes) and the size (micrometer- and nanometer dimensions) of the obtained 1D nanostructures is strongly dependent on the methodology used for making them. Finally, the degree of order of the nanostructures as well as the electro-optical properties of the resulting materials have been investigated by means of microscopy and spectroscopy techniques.
Ferrazza, Livio. "Nanomateriales basados en hidroxiapatita para la conservación del patrimonio cultural en soporte pétreo y pintura mural." Doctoral thesis, Universitat Jaume I, 2018. http://hdl.handle.net/10803/463083.
Повний текст джерелаThe objective of this doctoral thesis is the preparation of nanoparticles with pure hydroxyapatite stoichiometry Ca10(PO4)6(OH)2 and the evaluation of these materials in consolidation and protection treatments in stone support and wall painting. This multidisciplinary work is developed in two complementary areas of research: nanomaterials, focusing on the preparation and characterization of hydroxyapatite particles with a size of the order of nanometers, whose structural and morphological characteristics are chemically modified. The second part is related to the conservation of cultural assets by focusing the application of these materials on restoration treatments such as the consolidation and protection in stone support and mural painting.
Wang, Weiqiang. "Prion inspired nanomaterials and their biomedical applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670982.
Повний текст джерелаLos amiloides muestran una estructura fibrilar altamente ordenada. Muchos de estos ensamblajes aparecen asociados a enfermedades humanas. No obstante, la naturaleza controlable, estable, modulable y robusta de las fibras amiloides se puede emplear para construir nanomateriales notables con una amplia gama de aplicaciones. Los priones funcionales constituyen una clase particular de amiloides. Estas proteínas transmisibles exhiben una arquitectura modular, con un dominio priónico desordenado responsable del ensamblaje y uno o más dominios globulares que dan cuenta de la actividad. Cabe destacar que la proteína globular original se puede reemplazar con cualquier proteína de interés sin comprometer el potencial de fibrilación. Estas fusiones genéticas forman fibrillas en las que el dominio globular permanece plegado, lo que genera nanoestructuras funcionales. Sin embargo, en muchos casos, el impedimento estérico restringe la actividad de estas fibrillas. Esta limitación puede resolverse diseccionando los dominios de priones en secuencias más cortas que mantengan sus propiedades de autoensamblado mientras permiten un mejor acceso a la proteína en el estado fibrilar. En esta tesis doctoral, exploramos el "soft amyloid core" (SAC) del prion de levadura Sup35p como una unidad modular de autoensamblaje, que recapitula la propensión a la agregación del dominio priónico completo. Fusionamos el SAC con diferentes proteínas globulares de interés que difieren en conformación y tamaños, creando un enfoque genético general y directo para generar nanofibrillas dotadas de las funcionalidades deseadas. El modelado computacional nos permitió obtener información sobre la relación entre el tamaño de los dominios globulares y la longitud del conector que los une con el SAC, proporcionando la base para el diseño de nanomateriales con diferentes propiedades mesoscópicas, ya sean nanofibrillas o nanopartículas. Sobre esta base, diseñamos y producimos, por primera vez, nanopartículas amiloides esféricas, altamente activas, no tóxicas, de tamaño definido, y diseñamos nanoestructuras bifuncionales con aplicación en la administración dirigida de fármacos. Las lecciones aprendidas en estos ejercicios permitieron la construcción de una nanofibrilla similar a un anticuerpo biespecífico con potencial para su uso en inmunoterapia. En resumen, los nanomateriales funcionales similares a los priones descritos aquí aprovechan la metodología de fusión genética para generar un nuevo conjunto de estructuras con aplicación en biomedicina y biotecnología.
Amyloids display a highly ordered fibrillar structure. Many of these assemblies appear associated with human disease. However, the controllable, stable, tunable, and robust nature of amyloid fibrils can be exploited to build up remarkable nanomaterials with a wide range of applications. Functional prions constitute a particular class of amyloids. These transmissible proteins exhibit a modular architecture, with a disordered prion domain responsible for the assembly and one or more globular domains that account for the activity. Importantly, the original globular protein can be replaced with any protein of interest, without compromising the fibrillation potential. These genetic fusions form fibrils in which the globular domain remains folded, rendering functional nanostructures. However, in many cases, steric hindrance restricts the activity of these fibrils. This limitation can be solved by dissecting prion domains into shorter sequences that keep their self-assembling properties while allowing better access to the protein in the fibrillar state. In this PhD thesis, we exploited the "soft amyloid core (SAC)" of the Sup35p yeast prion as a modular self-assembling unit, which recapitulates the aggregation propensity of the complete prion domain. We fused the SAC to different globular proteins of interest differing in conformation and sizes, building up a general and straightforward genetic approach to generate nanofibrils endowed with desired functionalities. Computational modeling allowed us to gain insights into the relationship between the size of the globular domains and the length of the linker that connects them to the SAC, providing the basis for the design of nanomaterials with different mesoscopic properties, either nanofibrils or nanoparticles. On this basis, we designed and produced, for the first time, highly active, non-toxic, spherical amyloid nanoparticles of defined size and engineered bifunctional nanostructures with application in targeted drug delivery. The lessons learned in these exercises resulted in the construction of a bispecific antibody-like nanofibril, showing potential in immunotherapy. In summary, the prion-like functional nanomaterials described here take profit of the genetic fusion approach to render a novel set of structures with application in biomedicine and biotechnology.
Mallón, Pernia Laura. "Surface-functionalized and hybrid nanocatalysts for water splitting." Doctoral thesis, Universitat Autònoma de Barcelona, 2021. http://hdl.handle.net/10803/673661.
Повний текст джерелаUna solución para conseguir una fuente de energía libre de carbono es la fotoproducción de H2 mediante la división catalítica del agua (Water splitting, WS, Ecuación 1) utilizando la luz solar. 2H2O + hv --> 2H2 + O2 (Ecuación 1) WS es un proceso en el que el agua se oxida a dioxígeno en el ánodo (reacción de evolución del oxígeno, REO, Ecuación 2), constituyendo así la fuente de electrones para reducir los protones a H2 en el cátodo (reacción de evolución del hidrógeno, REH, Ecuación 3). 2H2O --> O2 + 4H+ + 4e- (Ecuación 2) 2H+ + 2e- --> H2 (Ecuación 3) El desarrollo de catalizadores de WS altamente activos y eficientes es esencial para la correcta cinética de estas dos semireacciones. Las nanopartículas (NPs) son verdaderos catalizadores potenciales debido a su alta estabilidad y relación superficie/volumen, exponiendo altas cantidades de sitios activos. En esta tesis doctoral se han sintetizado diferentes nanoelectrocatalizadores siguiendo el método organometálico, que resulta ventajoso para obtener nanomateriales de superficie limpia. Para entender los factores que afectan a la actividad electrocatalítica de los nanomateriales, se han realizado cálculos teóricos sobre la base de conceptos bien aceptados (energía libre de adsorción de hidrógeno, δGH*, y diagramas de volcán). Dado que los ligandos presentes en la superficie de las NPs metálicas pueden influir en la actividad electrocatalítica, se realizaron cálculos DFT para determinar los modos de coordinación más favorables de diferentes ligandos y obtener los valores de δGH*, obteniéndose correlaciones satisfactorias entre los datos experimentales y los de DFT. Diferentes estudios confirman que los soportes conductores de carbono mejoran la actividad electrocatalítica al restringir la agregación de los nanocatalizadores y mejorar la transferencia de electrones desde el nanocatalizador metálico al electrodo. En esta tesis doctoral se han utilizado dos materiales de carbono, el óxido de grafeno reducido (OGr) y las microfibras de carbono (FC), como soportes de NPs metálicas. Además, se ha estudiado el efecto del dopaje de N y P sobre el OGr en la REH, obteniendo un efecto sinérgico positivo entre heteroátomos y NPs de Ru. A diferencia del grafeno, las microfibras de carbono son más fáciles de manipular y pueden utilizarse directamente como electrodos. Así, se han sintetizado NPs de Ru y Co sobre dos microfibras diferentes, que difieren en la presencia o no de grupos -COOH en la superficie. Además, se han empleado dos metodologías diferentes, in situ y ex situ, para modificar la interfaz entre las NPs y el soporte de carbono mediante la adición de diferentes disolventes (THF o 1-heptanol) o ligandos (4-fenilpiridina, 4PP). Los resultados evidencian que una adecuada interacción entre las NPs y la superficie del soporte es clave para una mejor actividad catalítica, obteniéndose mejores resultados en los sistemas en los que tienen lugar interacciones π-π entre las estructuras Ru-4PP NPs/C o enlaces H entre las NPs de Co(OH)2 y -COOH en la FC. Otra estrategia prometedora es la adición de otro metal a una nanoestructura metálica, lo que conduce a efectos electrónicos beneficiosos al cambiar el entorno químico de los centros metálicos. En este sentido, se sintetizaron sistemas bimetálicos de Ru@Ni-espuma y NPs de RuCo. Se ha estudiado la influencia de diferentes porcentajes de dopaje de Ru en los sistemas de Ru@Ni-espuma sobre la actividad catalítica hacia la REO. Finalmente, se sintetizaron NPs de RuCo utilizando tres ligandos diferentes, 4’-(4-metilfenil)-2,2’:6’,2””-terpiridina, 4-PP y 1-heptanol, con el fin de determinar la influencia del ligando y de la ratio Ru/Co en el tamaño y la morfología de las NPs. Los estudios electrocatalíticos realizados abren una nueva puerta para explorar el interés de los nanocatalizadores bimetálicos en WS y la producción de hidrógeno.
One solution to achieve a carbon free energy source is the photoproduction of H2 by the catalytic water splitting (WS, Eq. 1) using sunlight. 2H2O + hv --> 2H2 + O2 (Eq. 1) WS is a process in which water is oxidized to dioxygen in the anode (oxygen evolution reaction, OER, Eq. 2), thus constituting the source of electrons to reduce protons to H2 in the cathode (hydrogen evolution reaction, HER, Eq. 3). 2H2O --> O2 + 4H+ + 4e- (Eq. 2) 2H+ + 2e- --> H2 (Eq. 3) Developing highly efficient and active WS catalysts is essential for the proper kinetics of these two reactions. Nanoparticles (NPs) are true potential catalysts due to their high stability and surface per volume ratio, exposing high amounts of active sites. In this PhD, different nanoelectrocatalysts have been synthesized by following the organometallic approach which is advantageous for obtaining clean-surface nanomaterials compared to other synthesis methodologies. To understand the factors affecting the electrocatalytic activity of the nanomaterials, theoretical DFT calculations have been performed on the basis of well accepted concepts (hydrogen adsorption free energy, δGH*, and volcano plots). Given that the ligands present on the surface of metal NPs can influence the electrocatalytic activity, DFT calculations were performed to determine the most favorable coordination modes of different ligands and to obtain the δGH* values of the resulting NPs. Successful correlations between experimental and DFT data have been obtained. Conductive C-based supports are known to enhance the electrocatalytic activity by restraining the aggregation of the nanocatalysts and improving the electron transfer from the metal nanocatalyst to the electrode. In this PhD, two different carbon materials, reduced graphene oxide (rGO) and carbon microfibers (CF) have been used as supports for metal NPs. Furthermore, the effect of N and P doping onto rGO has been studied towards the HER, obtaining a positive synergistic effect between the heteroatoms and Ru NPs. In contrast to graphene, CF are easier to handle and can be directly used as electrodes, thus avoiding the issues related to the NPs deposition onto macroscopic electrodes (GC, FTO). Thus, Ru and Co NPs have been synthesized on top of two different CF, differing in the presence or not of –COOH moieties onto the surface. Two different methodologies, in-situ and ex-situ, have been employed in order to tune the interface between the NPs and the C support by adding different solvents (THF or 1-heptanol) for Co NPs or ligands (4-phenylpyridine, 4PP) for Ru NPs. The results evidence that a proper interaction between the NPs and the support surface is key for an improved catalytic activity of the hybrid materials, obtaining better results in the systems where π-π interactions between Ru-4PP NPs/C structures or H-bonds between Co(OH)2 and COOH moieties in the CF take place. Another promising strategy is the addition of another metal onto a metallic nanostructure, leading to beneficial synergistic electronic effects by changing the chemical environment of the metal centers and decreasing the adsorption energy of the reactants. In this sense, bimetallic Ru@Ni-foam and RuCo NPs systems were synthesized. The influence on the catalytic activity towards OER of different percentages of Ru-doping in Ru@Ni-foam systems has been studied. Finally, RuCo bimetallic systems were synthesized by using three different ligands, 4’-(4-methylphenyl)-2,2’:6’,2”-terpyridine, 4-PP and 1-heptanol. The influence of the ligand and the Ru/Co metal ratio on the size and morphology of the NPs has been determined. Preliminary electrocatalytic tests have been performed, opening a new door to explore the interest of bimetallic nanocatalysts for the water-splitting and the production of hydrogen.
Universitat Autònoma de Barcelona. Programa de Doctorat en Química
Miranda, Barbara Santos de 1984. "Síntese e modificação de nanomateriais visando o desenvolvimento de sensores." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/248399.
Повний текст джерелаTese (doutorado) - Universidade Estadual de Campinas, Instituto de Química
Made available in DSpace on 2018-08-23T23:55:15Z (GMT). No. of bitstreams: 1 Miranda_BarbaraSantosde_D.pdf: 3761472 bytes, checksum: d04db9862f7022a5bea49d756efbfdbc (MD5) Previous issue date: 2013
Resumo: Este trabalho apresenta o desenvolvimento de dois sensores distintos que através da aplicação de nanomateriais em seus sistemas apresentam uma melhora no desempenho. Com o objetivo de estabilizar a fase alfa do hidróxido de níquel, foi proposta uma nova síntese que resultou em um novo material de hidróxido de níquel e nanopartículas de ouro. O do hidróxido de níquel se apresentou com a estrutura alfa desejada, a estrutura e morfologia das nanopartículas de ouro foram preservadas. O material híbrido se apresenta nanoestruturado e sem separação de fases. Sugere-se que este novo material seja formado como um nanocompósito onde as nanopartículas de ouro formam a matriz e o hidróxido de níquel recobre a superfície. A estabilidade do novo material é bem superior que a do hidróxido de níquel puro, quedas de corrente após 50 ciclos consecutivos de 6% contra 50% respectivamente. A atividade eletrocatalítica deste novo nanomaterial foi investigada frente à glicose e a constante eletrocatalítica obtida para o nanocompósito foi cerca de 7 vezes maior que para o hidróxido de níquel puro. A sensibilidade do eletrodo modificado com a-Ni(OH)2/AuNP se manteve similar aos da literatura. O segundo sensor estudado foi a aplicação de nanopartículas fluorescentes como marcadores do imunosensor para a detecção precoce do esporo do fungo da ferrugem asiática da soja. As nanopartículas fluorescentes permitiram alcancar um baixo limite de detecção, 2.2 ng/mL, o menor encontrado na literatura. Além disso, foi investigado outros parâmetros para o desenvolvimento de um dispositivo point-of-care, como o melhor substrato para reter o analito, a membrana de nitrocelulose, se apresentou com as melhores propriedades frente as alternativas. Ainda mais, o dispositivo foi construido para que possa ser utilizado por pessoas não treinadas no campo, em um tempo de análise menor que ELISA e PCR, sem o uso de equipamento caros e complicados, usando somente uma lâmpada de UV simples como fonte de excitação e a visualização do sinal a olho nu com um limite de detecção de apenas 300 esporos, o que e ainda dez vezes mais baixo que o atual teste comercial.
Abstract: This work presents the development of two distinct sensors that have shown great improvements in their performance trough nanoparticle application in their systems. The first study aims to stabilize the nickel hydroxide alpha structure for future carbohydrate detection. We proposed a new synthesis, which resulted in a nickel hydroxide and gold nanoparticle hybrid material. The new material has the expected nickel hydroxide alpha structure, maintains gold nanoparticle¿s structure and morphology and allows a simple electrode modification. We suggest that the new material is a nanocomposite where gold nanoparticles are the matrix while the nickel hydroxide cover the surface. The new material has higher stability properties than the pure nickel hydroxide, after 50 cycles the current decreased 6 and 50% respectively. In addition, an improvement was observed in the catalytic constant, approximately 7 times bigger than plain nickel hydroxide. Although the new material showed these good improvements, the electrode sensitivity did not differ from other studies in the literature. The second study presented comprehends the application of fluorescent nanoparticles as markers of an immunosensor for early diagnosis of Asian soybean rust spore. The use of these nanoparticles resulted in a very low limit detection sensor, 2.2 ng/mL, the lowest ever found in the literature. Moreover, others parameters were investigated in order to develop a point-of-care device, as the substrate to retain the analyte for the assay. Furthermore, the device was built in order to be used by the farmer himself, in loco, fast, without expensive equipment, a UV lamp as an excitation source and the signal is visible to naked eye. The visual detection limit is around 300 spores, which is tenfold lower than the available commercial kit.
Doutorado
Físico-Química
Doutora em Ciências
Mesquita, Alexandre. "Preparação e caracterização de materiais ferroelétricos de composição Pb1-xLaxTiO3 em escala nanométrica." Universidade de São Paulo, 2007. http://www.teses.usp.br/teses/disponiveis/88/88131/tde-12092007-163646/.
Повний текст джерелаThe main objective of this work was to obtain ferroelectric materials of Pb1-xLaxTiO3 (PLT) composition, with x = 0.10, 0.15 and 0.20, in nanometer scale in order to prepare nanostructure ceramic and thin films and characterize their structural and electric properties. The nanoparticles used to prepared ceramic samples and the solution used to prepared thin films was obtained using the conventional high temperature sintering method and by using high pressure and high temperature simultaneously. The structural modification due to particle size and lanthanum amount was followed by X-Ray diffraction (XRD), Raman spectroscopy and X-Ray absorption techniques. The transition process was followed from XRD pattern and from the Raman spectra. Samples calcined at 400 oC that were characterized as amorphous present different X-ray absorption spectra. The ceramic samples sinterized at high temperature and ambient pressure presented a microstructure (microsized grains) and electrical properties (normal ferroelectric) similar to that observed in the same samples obtained from the solid-state reaction method. On the other hand, the ceramic sample with x = 0.20 prepared at high pressure and at room temperature formed only by nanoparticles present a behavior characteristic of a relaxor ferroelectric material showing the influence of the grain size on the electrical properties of these samples.
Lima, Juliana Fonseca de. "Nanocompostos a base de cério com aplicações na absorção da radiação ultravioleta." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/59/59138/tde-04042013-150245/.
Повний текст джерелаLight and oxygen induce degradation reactions (photo-oxidation) that modify the physical and chemical properties of the matter. The damaging UV radiation is responsible for the discoloration of dyes and pigments, weathering, yellowing of plastics, loss of gloss and mechanical properties (cracking), sunburnt skin and other problems associated to UV light. UV absorbers or UV filters have been used in order to reduce these damaging effects and achieve an adequate conservation of the properties of the materials. In front of this problem, cerium based nanomaterials are promising inorganic UV absorbers for the substitution of zinc and titanium oxide, once it presents high UV absorptivity, a lower refraction index than TiO2 and ZnO, and a higher chemical inertia (and thus a lower photocatalytic activity). Nanostructured cerium phosphates (CePO4) were prepared by Pechini, hydrothermal and reverse microemulsion synthesis, and some parameters (calcinations temperature and reactants rate) employed in each synthesis were investigated. Cerium metal oxide systems synthesized by sol-gel (non-alcooxide) and applied as powder and thin films materials were investigated too. The methodology of the synthesis were chosen aiming ideal morphology and particles size. In this work we explored and elucidated the properties of UV absorber cerium based nanomaterials , due to 4f-5d transitions of Ce3+ ions, charge transference of Ce4+ and, a little portion is due to the contribution of valence and conduction band. The samples were characterized by UV-Vis absorption spectroscopy , Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), electron diffraction, magnetic susceptibility (MS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), diffuse reflectance spectroscopy (DRS), photocatalytic activity (PA) and electron paramagnetic resonance (EPR). The excellent morphological, optical and photocatalytic properties indicate the possible application of cerium based materials in solar protection for cosmetics (creams, shampoos, sprays etc.) or materials (paints, varnishes, glass and others).
Jia, Xiaoting. "In-situ TEM study of carbon nanomaterials and thermoelectric nanomaterials." Thesis, Massachusetts Institute of Technology, 2011. http://hdl.handle.net/1721.1/69666.
Повний текст джерелаThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 103-112).
Graphene nanoribbons (GNRs) are quasi one dimensional structures which have unique transport properties, and have a potential to open a bandgap at small ribbon widths. They have been extensively studied in recent years due to their high potential for future electronic and spintronic device applications. The edge structures - including the edge roughness and chirality - dramatically affect the transport, electronic, and magnetic properties of GNRs, and are of the critical importance. We have developed an efficient way of modifying the edges structures, to produce atomically smooth zigzag and armchair edges by using insitu TEM with a controlled bias. This work provides us with many opportunities for both fundamental studies and for future applications. I also report the use of either furnace heating or Joule heating to pacify the exposed graphene edges by loop formation in the graphitic nanoribbons. The edge energy minimization process involves the formation of loops between adjacent graphene layers. An estimation of the temperature during in-situ Joule heating is also reported based on the melting and evaporation of Pt nanoparticles. In this thesis work, I have also investigated the morphological and electronic properties of GNRs grown by chemical vapor deposition. Our results suggest that the GNRs have a surprisingly high crystallinity and a clean surface. Both folded and open edges are observed in GNRs. Atomic resolution scanning tunneling microscopy (STM) images were obtained on the folded layer and the bottom layer of the GNR, which enables clear identification of the chirality for both layers. We have also studied the electronic properties of the GNRs using low temperature scanning tunneling spectroscopy (STS). Our findings suggest that edges states exist at GNR edges which are dependent on the chiral angles of the GNRs.
by Xiaoting Jia.
Ph.D.
Mingorance, Ferrer Alba. "Solution processable oxides for inverted and carbon based perovskite solar cells." Doctoral thesis, Universitat Autònoma de Barcelona, 2019. http://hdl.handle.net/10803/669401.
Повний текст джерелаThis thesis is dedicated to the enhancement of the photovoltaic response of Perovskite Solar Cells (PSCs) with the use of semiconductor oxides as electronic transport materials. Semiconductor oxides of the type REOx, where RE stands for rare earth, can serve as charge transporting materials, due to their good transparency and charge transfer. The selected hole transport materials (HTMs) and electron transport material (ETMs) have been characterized using experimental techniques such as X-Ray Diffraction (XRD) and Photoelectron Spectroscopies (XPS-UPS) in order to better understand the degree of crystallinity and the electronic properties of these semiconductor oxides. Two architectures have been used, in order to improve efficiency, stability and reduce manufacturing costs: inverted and carbon-based architectures. C-based PSCs are fully printable and provide a rather simple fabrication. We have also found that the use of NiOx as a HTM in an inverted architecture can improve the photovoltaic parameters of PSC devices. Microscopy techniques, such as Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM), Focused Ion Beam (FIB) were also employed to determine the morphology of the layers and to understand the degradation mechanisms that occur at the interface level with the final aim of enhancing the photovoltaic performance and stability of solar cell devices. Finally, the functionalization of metal-oxide interlayers (TiO2/ZrO2) in C-based PSCs using organic molecules such as 5 aminovaleric acid iodide (5-AVAI) has been increased the performance of these kind of solar cells. We experimentally fabricated a C-based PSC with a PCE as high as 11.5 % under AM 1.5G illumination at 100 mW/cm2 after several optimization of the complete working device. Also, the CPSCs show good long-term stability under irradiation conditions as has been reported for more than 1000 h. This work addresses the technological issues stated above and proposes suitable concepts for the improvement in terms of efficiency and stability employing semiconductor oxides in PSCs.
Becerril-Garcia, Hector Alejandro. "DNA-Templated Nanomaterials." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd1823.pdf.
Повний текст джерелаMaggio, Mario. "Carbon-based nanomaterials." Doctoral thesis, Universita degli studi di Salerno, 2017. http://hdl.handle.net/10556/2482.
Повний текст джерелаNew layered carbon-based materials were prepared and exhaustively characterized exploiting different characterization techniques, such as thermogravimetry (TGA), differential thermal calorimetry (DSC), Fourier transform infrared (FTIR) and wide angle X-ray diffraction (WAXD). Pristine graphite (G) with high surface area and carbon black (CB) samples with different surface areas were selected as starting materials to prepare the corresponding oxidized samples, i.e. graphite oxide (GO) and carbon black oxide (oCB), with the Hummers’ method. Thanks to the strong hydrophilicity and to the lamellar structure of oxidized carbon-based materials, a rich intercalation chemistry is permitted. In fact, after treatments of GO and oCB by strong basis, ordered intercalation compounds have been obtained, not only if the starting material is crystalline like graphite oxide, but also if it is completely amorphous like oxidized carbon black. Starting basified GO, free-standing papers can be obtained by vacuum filtration, as well as by casting procedure, of colloidal dispersions of graphene oxide sheets. The use of basified GO leads to more flexible, solvent resistant and thermally stable GO papers. Spectroscopic analyses of the obtained papers have been conducted aiming to a possible rationalization of the observed behavior. [edited by author]
Per questo lavoro di tesi di dottorato, sono stati preparati nuovi nanomateriali basti su carbonio ed esaustivamente caratterizzati con tecniche quali termogravimetria (TGA), calorimetria a scansione differenziale (DSC), spettroscopia infrarossa (FT-IR) e diffrazione dei razzi X (WAXD). I materiali di partenza utilizzati per questo lavoro di tesi, sono stati la grafite ad alta area superficiale e carbon black con differenti valori di area superficiale, al fine di ottenere i corrispondenti materiali ossidati quali ossido di grafite (GO) e carbon black ossidato (oCB). Il metodo utilizzato per le ossidazioni dei suddetti starting materials è quello di Hummers. Grazie alla forte idrofilicità ed alla struttura lamellare posseduta dai materiali carboniosi ossidati, è possibile ottenere svariati composti di intercalazione trattando il GO (cristallino) e l’oCB(amorfo) con basi forti e con conseguente funzionalizzazione ionica con cationi di natura organica. Inoltre, partendo da dispersioni di GO basificato, sono stati ottenuti fogli di ossido di grafite e di grafene mediante filtrazione e/o per lenta evaporazione del solvente. Utilizzando una base nella procedura di ottenimento dei cosiddetti fogli di ossido di grafite/grafene, sono stati preparati campioni free-standing con elevata flessibilità, resistenza ai solventi e alle alte temperature. [a cura dell'autore]
XIV n.s.
Oliveira, Thiago Mielle Brito Ferreira. "Biossensores EnzimÃticos para DetecÃÃo e QuantificaÃÃo de Carbamatos em Amostras de Alimentos." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=11864.
Повний текст джерелаEste trabalho contempla trÃs estratÃgias para o biossensoriamento de pesticidas da classe dos carbamatos (CBM) em alimentos naturais, utilizando biossensores à base de polifenoloxidases como dispositivos analÃticos: (i) eletrodo de pasta de nanotubos de carbono (EPNC) modificado com lacase de Tramites versicolor (LAC) por entrapment da enzima diretamente no material compÃsito, definido como LAC-EPNC; (ii) eletrodo de pasta de grafeno (EPG) modificado com filmes de Azul da PrÃssia (AP), seguido da imobilizaÃÃo de LAC por drop coating, definido como LAC/AP/EPG; e (iii) EPG modificado por eletrodeposiÃÃo de filme hÃbrido composto por quitosana (CS), nanopartÃculas de ouro (NpAu) e mistura das enzimas LAC e tirosinase de Agaricus bisporus (TIR), definido como LAC-TIR-NpAu-CS/EPG. Tomado por base o processo redox do substrato 4-aminofenol (4-AMF), a presenÃa dos nanotubos de carbono e do grafeno proporcionou uma sÃrie de vantagens aos dispositivos, a saber: aumento nos valores de corrente de pico, catÃlise do processo redox, melhoria na reversibilidade e, consequentemente, na cinÃtica de transferÃncia eletrÃnica. Filmes de AP (imobilizaÃÃo direta da enzima sem a necessidade de regente para cross-linking), CS (biocompatibilidade adequada, maior imobilizaÃÃo e fixaÃÃo das enzimas) e NpAu (reduÃÃo da resistÃncia a transferÃncia de carga) tambÃm apresentaram importante papel na configuraÃÃo eletrÃdica dos biossensores. As curvas analÃticas foram construÃdas por voltametria de onda quadrada, baseando-se na capacidade dos CBM (carbofurano, carbaril, formetanato, pirimicarbe, propoxur e ziram) de inibir a atividade das polifenoloxidases. Em geral, os procedimentos propostos apresentaram sensibilidade (limites de detecÃÃo variando de 0,001 a 0,093 mg kg-1) que contempla os limites mÃximos estabelecidos pelas agÃncias de seguranÃa e controle alimentar brasileira e europeia para resÃduos de CBM em hortaliÃas (tomate, alface e batata) e frutas cÃtricas (laranja, tangerina e limÃo), com baixo nÃvel de interferentes. Os ensaios de recuperaÃÃo foram realizados em extratos QuEChERS das amostras, com porcentagens de recuperaÃÃo variando de 91,0  0,1% a 101,10  0,1%; para contaminaÃÃes de 0,01 a 3,14 mg kg-1. Portanto, LAC-EPNC, LAC/AP/EPG e LAC-TIR-NpAu-CS/EPG podem ser ferramentas promissoras na anÃlise de CBM em matrizes alimentares.
This work contemplates three strategies for carbamate pesticides (CBM) biosensing in natural food, using polyphenoloxidases based biosensors as analytical device: (i) carbon nanotubes paste electrode (CNPE) modified with laccase from Tramites versicolor (LACC), namely as LACC-CNPE; (ii) graphene paste electrode (GPE) modified with Prussian Blue films (PB), followed by the LACC immobilization by drop coating, namely as LACC/PB/GPE; and (iii) GPE modified by the electrodeposition of a hybrid film composed for chitosan (CS), gold nanoparticles (AuNp) and a mixing of LACC and tyrosinase from Agaricus bisposrus (TYR), namely as LACC-TYR-AuNp-CS/GPE. Based on 4-aminophenol (4-AMP) redox process, the presence of carbon nanotubes and graphene allowed several advantages to the devices, such as: increase of the peak currents values, catalysis of the redox process, improvement of the reversibility and electronic-transfer kinetic. PB films (direct enzymatic immobilization without cross-linking reagent), CS (suitable biocompatibility, higher immobilization and fixation of the enzymes) and AuNp (reduction of the charge-transfer resistance) also showed important role on biosensors electrodic configuration. Analytical curves were constructed by square-wave voltammetry, based on CBM (carbofuran, carbaryl, formetanate, pirimicarb, propoxur and ziram) capability to inhibit the polyphenoloxidase activity. In general, the proposed procedures had sensitivity (detection limits ranging from 0.001 to 0.093 mg kg-1) in compliance with the maximum limit established by Brazilian and European food surveillance and control agencies for the analysis of CBM residues in vegetable crops (tomato, lettuce and potato) and citrus fruits (orange, tangerine and lemon), with negligent interfering effect. Recuperation experiments were carried out with QuEChERS extracts of the samples, allowing recuperation values from 91.0 Â 0.1% to 101.1 Â 0.1%; for spiking levels from 0.01 to 3.14 mg kg-1. Thus, LACC-CNPE, LACC/PB/GPE and LACC-TYR-AuNp-CS/GPE are promisor tools for CBM analysis in food matrices.
Silva, Ricardo Fernandes da. "Estudo de caracterização de pós nanoestruturados de fosfato de cálcio e nanocompósitos fosfato de cálcio sio2n para aplicações biomédicas." Universidade do Estado de Santa Catarina, 2007. http://tede.udesc.br/handle/handle/1712.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
The nanotechnology can be understood as the term used to describe the creation, manipulation and exploration of materials in nanometric scale. This Science is used for study nanostructured materials, constituted of atoms, molecules and/or particles. Brazil comes detaching some areas development some nanotechnology products, for applications in chemical analyses, medical and odontologic treatments and in the development of nanoparticles, nanotube, nanowires and cristalografic analysis. The nanoestructured powder-ceramic synthesis calcium phosphate and materials nanocomposites are promising in surgical applications medical-odontologics in the setting of prothesis, wedding bone, in coverings for the implantations, the stabilization of implantations and as matrical element in the reconstitution of the bone structure. This work had as objective the characterization of powder nanoestructured calcium phosphate and nanocomposite calcium phosphate/SiO2n, in the percentile nanometric silicom compositions (SiO2n) of 5%, 10% and 15% in volume; through the techniques of scanning electron microscopy, X-ray diffractometry and the method of numerical simulation were used for determination of surface area nanopowder. The studies using the method of numerical simulation had been carried through on the ones powder nanoestructured gotten of the calcination 9000C/2h. This method can be an innovative methodology, in the determination of surface area nanoparticles, since, the results obted in this work if approach to the values found for BET. The gotten results of these studies, had evidenced the presence for powder nanoestructured phase b-calcium phosphate calcinations 9000C/2h, b and a - calcium phosphate ones powder thermal treatment 1300ºC/2h. The morphology of the bone matrix calcium phosphate, gotten of the drying in rotoevaporador, is formed by nanoparticles agglomerated with average size 20nm. For the ones powder gotten nanocomposites the drying it observed type of morphology the same, more the presence of nanopartículas of SiO2n. For the powder gotten of the calcination and the thermal treatment, it was evidenced to have modification of the morphology of particles, being observed the germination and growth of the average diameter of nanopartículas in function of the temperature. The method of numerical simulation, allowed to identify the surface of average area of nanopartilces for the powder nanoestrutured gotten the calcination. A preliminary study of citotoxidade and the cellular viability was also become fullfilled, on the powder nanoestrutured gotten of the calcination and the thermal treatment. The gotten results of this study are entertainers and the values of the index of cellular viability had on average presented up 80% for all the nanoestrutured compositions of powder from in the tests of 24h, 48h and 72h.
A nanotecnologia pode ser entendida como sendo o termo utilizado para descrever a criação, manipulação e exploração de materiais em escala nanométrica. Esta Ciência é utilizada para investigação de materiais nanoestruturados, constituídos por átomos, moléculas e/ou partículas. O Brasil vem se destacando em algumas áreas de desenvolvimento de alguns produtos nanotecnológicos, destes se destacam os produtos utilizados em aplicações de análises químicas, tratamentos médicos e odontológicos, o desenvolvimento de nanopartículas, nanotubos, nanofios e análises cristalográficas. A síntese e caracterização de pós biocerâmicos nanoestruturados de fosfato de cálcio e nanocompósitos é um método promissor de produção de pós biocerâmicos com características morfológicas, de superfície de área e da microporosidadeade favoráveis para uso em aplicações cirúrgicas médico-odontológicas, na fixação de próteses, enchimento ósseo, em revestimentos de implantes, na estabilização de implantes e como elemento matricial na reconstituição da estrutura óssea. Este trabalho teve como objetivo a caracterização de pós nanoestruturados de fosfato de cálcio e nanocompósito fosfato de cálcio/SiO2n, nas composições percentuais de sílica nanométrica (SiO2n) de 5%, 10% e 15% em volume; através das técnicas de microsopcopia eletrônica de varredura, difratometria de raios-X e o método de simulação numérica foi utilizado para determinação da superfície de área das nanopartículas. Os estudos utilizando o método de simulação numérica foram realizados sobre os pós nanoestruturados obtidos da calcinação a 9000C/2h. Este método pode ser uma metodologia inovadora, na determinação de superfície de área de nanopartículas, visto que, os resultados obidos neste trabalho se aproximam dos valores encontrados por BET. Os resultados obtidos destes estudos, evidenciaram a presença da fase fosfato de cálcio-b para os pós nanoestruturados obtidos da calcinação a 900ºC/2h e as fases fosfato de cálcio a e b, para os pós obtidos do tratamento térmico a 1300ºC/2h. A morfologia da matriz óssea de fosfato de cálcio, obtida da secagem em rotoevaporador, é formada por nanopartículas aglomeradas com tamanho médio inferior a 20nm. Para os pós nanocompósitos obtidos da secagem observou o mesmo tipo de morfologia, mais a presença das nanopartículas de SiO2n. Para os pós obtidos da calcinação e do tratamento térmico, constatou-se haver modificação da morfologia das partículas, observando a germinação e crescimento do diâmetro médio das nanopartículas em função da temperatura. O método de simulação numérica, permitiu identificar a superfície de área média das nanopartículas para os pós nanoestruturados obtidos da calcinação. Realizou-se também um estudo preliminar de citotoxidade e da viabilidade celular, sobre os pós nanoestruturados obtidos da calcinação e do tratamento térmico. Os resultados obtidos deste estudo são animadores e os valores do índice de viabilidade celular apresentaram-se em média superior a 80% para todas as composições de pós nanoestruturados a partir de nos testes de 24h, 48h e 72h.
Bellini, Odair José. "Síntese e caracterização de uma matriz óssea de fosfato de cálcio e nanocompósitos fosfato de cálcio/sio2n para substituição e regeneração óssea." Universidade do Estado de Santa Catarina, 2007. http://tede.udesc.br/handle/handle/1713.
Повний текст джерелаCoordenação de Aperfeiçoamento de Pessoal de Nível Superior
The synthesis of nanostructured calcium phosphate powders, and nanocomposite has called attention in different areas of biomedical, and odontological applications mainly in the replacement, and regeneration of bone tissues. This is due, mainly, because these nanomaterials present good biocompatibility and mineralogical characteristics similar of human skeleton apatite. These nanomaterials also offer good bone tissue reabsorption, osteointegration, and osteoinduction towards the inner part of nanomaterial structure, which accelerate new bone tissue regenaration, reconstitution, and formation. This work goal has been focused on optimization of aqueous suspension synthesis method, from a calcium phosphate SiO2n nanostructured and nanocomposites calcium phosphate matrix bone in the concentration of 5, 10 and 15% in silicon nanometric volume spread in the bone matrix inter-intragranular position. This method has allowed obtaining nanostructured powders through small agglomerated particles with size below 100 nm. Nanostructured powders originated from this synthesis have undergone calcinations through a temperature of 900o.C/2h aimed to eliminate organic material stemmed from the synthesis process, and for calcium phosphate phase. Presented results are related to synthesis method, morphological characterization, microstructural, nanostructural, and mineralogical of the thermal behavior for nanostructured obtained from 900oC/2h calcinations, from thermal treatment through a temperature of 1300oC/2h for syntherized and annealing biomaterials. The mechanical properties were determined by different compositions of nanostructured biomaterial obtained from 1300oC/2h syntherization annealing at a temperature of 1100oC/30min. A preliminary citotoxity and cellular viability study has also been made on the nanostructured powders obtained from calcinations and thermal treatment. Results obtained from this study are encouraging, and cellular viability index have presented an average higher than 80% for all compositions of nanostructured powders after 24 hours.
A síntese de pós nanoestruturados de fosfatos de cálcio e nanocompósitos tem despertado interesses em diferentes áreas de aplicações biomédicas e odontológicas, principalmente na substituição e na regeneração de tecido ósseo. Isto se deve principalmente por estes nanomateriais apresentarem boa biocompatibilidade e características mineralógicas semelhantes a da apatita do esqueleto humano. Estes nanomateriais oferecem também uma boa reabsorção, osteointegração e osteoindução do tecido ósseo para o interior da estrutura do nanomaterial, o que acelera a regeneração, a reconstituição e a formação do novo tecido ósseo. O objetivo deste trabalho se concentrou na otimização do método de síntese via úmida, de uma matriz óssea de fosfato de cálcio nanoestruturado e nanocompósitos fosfato de cálcio/SiO2n, nas concentrações de 5, 10 e 15% em volume de sílica nanométrica dispersa em posição inter-intragranular na matriz óssea. Este método permitiu a obtenção de pós nanoestruturados formados por finas partículas aglomeradas com tamanho menor que 100 nm. Os pós nanoestruturados obtidos da síntese, foram calcinados a temperatura de 900oC/2h, com objetivo de eliminação de material orgânico, resultante do processo de síntese e para formação da fase fosfato de cálcio- Ò. Os resultados apresentados estão relacionados ao método de síntese, à caracterização morfológica, microestrutural, nanoestrutural, mineralógica do comportamento térmico para os pós nanoestruturados obtidos da calcinação a 900oC/2h e do tratamento térmico a temperatura de 1300oC/2h, e para os biomateriais sinterizados e recozidos. As propriedades mecânicas foram determinadas para as diferentes composições de biomateriais nanoestruturados obtidos da sinterização a 1300oC/2h e recozidos a temperatura de 1100oC/30min. Realizouse também um estudo preliminar de citotoxidade e da viabilidade celular, sobre os pós nanoestruturados obtidos da calcinação e do tratamento termico. Os resultados obtidos deste estudo são animadores e os valores do índice de viabilidade celular apresentaram-se em média superiores a 80% para todas as composições de pós nanoestruturados a partir de 24h.
Costa, Nuno Mouta Faria da. "Short term toxicity of nanomaterials in different development stages of amphibians." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14129.
Повний текст джерелаThe production of engineered nanomaterials is rising and constantly growing. The fast advances in this industry are causing the introduction of nanomaterials (NMs) into the environment, namely into aquatic ecosystems. The specific properties that these new compounds exhibit may promote higher toxicity to biota, comparatively to their bulk counterparts. Size, charge, surface area, aggregation index, among others, may dictate the availability and the degree of toxicity of NMs in aquatic environments, especially when assembled with environmental changing conditions such as pH and temperature. Amphibians are excellent bioindicators to study the risk associated with the release of NM into the aquatic environment, since they inhabit a wide variety of freshwater habitats associated with industrial contamination. The present work intended to study the toxicity of NMs to different life stages of amphibians, concerning the increase of global temperature that is currently taking place. In order to achieve this, two specific goals were determined: i) evaluate the influence of temperature in the toxicity of NMs of hidrophobically modified polyacrylic acid (HM-PAA) to tadpoles of Epidalea calamita and Pelophylax perezi. For this, tadpoles of E. calamita and P. perezi were exposed to a range of six concentrations of HM-PAA plus a control, at 20ºC and 25ºC. Results showed lethal and sublethal toxicity of HM-PAA, but a clear pattern of temperature influence in the toxicity of HM-PAA could not be unveiled; ii) assess the influence of Si-NM size and temperature in the toxicity of this NM to embryos of Pelophylax perezi. To attain this goal, embryos of P. perezi were exposed to a range of six concentrations of three differently sized Si-NMs (SM30-7nm, HS30-12nm, and TM40-22nm) plus a control, at 20ºC and 26ºC. Results obtained show lethal and sublethal toxicity caused by all the Si-NM and an increased toxicity at higher temperatures. Furthermore, it was observed that the NM presenting the lowest primary size exhibited the highest toxicity.
A produção de nanomateriais artificiais está em constante crescimento. Os rápidos avanços nesta indústria promovem a introdução de nanomateriais (NMs) no meio ambiente, nomeadamente nos ecossistemas aquáticos. As propriedades específicas que estes compostos apresentam podem promover uma maior toxicidade comparativamente aos seus correspondentes de tamanho não nano. Tamanho, carga, área superficial, índice de agregação, entre outras propriedades, podem ditar o grau de toxicidade dos NMs em ambientes aquáticos, especialmente quando combinados com as constantes mudanças de vários parâmetros ambientais, por exemplo pH e temperatura. Os anfíbios são excelentes bioindicadores para estudar o risco associado à introdução de NMs no meio aquático, uma vez que habitam uma grande variedade de habitats de água doce potencialmente contaminados com descargas industriais. O presente trabalho teve como objetivo estudar a toxicidade de NMs em diferentes estágios de vida de anfíbios, tendo em perspetiva a influência do aumento da temperatura global que atualmente afeta o planeta Terra. A fim de alcançar este objetivo, foram realizados dois estudos que pretenderam: i) avaliar a influência da temperatura na toxicidade de NMs de ácido poliacrílico hidrofobicamente modificado (HM-PAA) para girinos de Epidalea calamita e Pelophylax perezi. Para tal, girinos de E. calamita e P. perezi foram expostos a uma gama de seis concentrações de HM-PAA e a um controlo, a temperaturas de 20ºC e 25ºC. Os resultados mostram toxicidade letal e sub-letal provocada pelo HM-PAA, no entanto, não foi visível um padrão claro de influência da temperatura na toxicidade deste NM; ii) determinar a influência do tamanho de Si-NMs e da temperatura na sua toxicidade para embriões de Pelophylax perezi. Ovos de P. perezi foram expostos a uma gama de seis concentrações de três Si- NPs com diferentes tamanhos (SM30-7nm, HS30-12nm, e TM40- 22nm) e a um controlo, a temperaturas de 20ºC e 26ºC. Os resultados obtidos mostram toxicidade letal e sub-letal causadas pelos 3 NMs e um aumento da toxicidade com temperaturas mais elevadas. Mais ainda o NM com menor tamanho apresentou maior toxicidade.
Díaz, Caballero Marta. "Prion inspired assemblies to build up functional bionanomaterials." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/670481.
Повний текст джерелаPese a que el ensamblaje amiloide se ha relacionado tradicionalmente con las enfermedades, en las últimas dos décadas, se ha destacado su implicación en importantes funciones biológicas. Estos hallazgos han incrementado el interés por el desarrollo de nanomateriales inspirados en amiloides en múltiples áreas como la biomedicina, la nanoelectrónica, las ciencias medioambientales o la nanotecnologia. La complejidad de la producción y manipulación de proteínas amiloides completas ha manifestado la necesidad de obtener bloques alternativos que mimeticen sus propiedades para el ensamblaje de nanomateriales basados en amiloides. El uso de péptidos cortos naturales o sintéticos ha surgido como una de las soluciones más atractivas, la síntesis de los cuales resulta más fácil, rápida y barata en comparación con las secuencias completas. Los priones y las proteínas prion-like muestran velocidades de agregación más lentes en comparación con los amiloides clásicos y, en determinadas condiciones, el proceso puede ser reversible, dos propiedades que las hacen más atractivas para el desarrollo de nanomateriales. Pese a esta potencialidad, el diseño de novo y la síntesis de péptidos cortos inspirados en priones para aplicaciones nanotecnológicas no se ha explorado hasta hace poco tiempo. En esta tesis, se recogen una serie de estudios en referencia al diseño y la caracterización de nanomateriales sintéticos inspirados en priones. Se ha explorado la capacidad de los péptidos cortos diseñados basados en la composición de los priones para polimerizar en agregados amiloides y se han estudiado las interacciones moleculares que permiten su organización supramolecular. Además, se han ilustrado algunas de sus potenciales aplicaciones, explorando sus propiedades biocatalíticas, su acoplamiento al sistema biotina-estreptavidina i su decoración con cationes metálicos divalentes. También se ha explorado como los ensamblajes de este tipo de péptidos se puede controlar de manera reversible mediante la manipulación del pH. Finalmente, la última parte de la tesis se focaliza en el estudio de las propiedades citotóxicas de los ensamblajes solubles iniciales que pueblan la reacción de fibrilación de nanoestructuras inspiradas en priones funcionales. En general, esta tesis destaca la potencialidad de las secuencias prion-like para generar bionanomateriales, enfatizando en su versatilidad y adaptabilidad funcional para múltiples aplicaciones nanobiotecnológicas. También se propone que los estudios de bioseguridad deberían ser implementados rutinariamente durante el desarrollo de nanomateriales basados en amiloides.
Despite amyloid scaffolds have been traditionally related to disease, in the last two decades, it has been highlighted their involvement in important biological functions. These findings raised the interest in the development of amyloid based nanomaterials in multiple areas like biomedicine, nanoelectronics, environmental sciences and nanotechnology. The complexity of the production and manipulation of amyloidogenic full-length proteins evidenced the need for alternative building-blocks that mimic their properties to assemble amyloid-based nanomaterials. The use of natural and artificial short peptides has emerged as one of the most appealing solutions, their synthesis and purification resulting easier, faster and cheaper compared to complete protein sequences. Prion and prion-like proteins present a slow aggregation rate compared to classical amyloids and, under certain conditions, the assembly process can be reverted, two properties that make them attractive for the development of nanomaterials. Despite this potentiality, the de novo design and synthesis of short prion-inspired peptides for nanotechnological purposes has been scarcely explored until recent time. In this thesis, we collect a series of studies regarding the design and characterization of synthetic prion-inspired nanomaterials. We addressed the capacity of designed short peptides to polymerize into amyloid assemblies and studied the molecular interactions behind their supramolecular organization. Furthermore, we illustrated some of their potential applications exploring their biocatalytic properties, their coupling with the biotin-streptavidin system and their decoration with divalent metallic cations. We also explored how the assembly of this kind of peptides can be controlled in a reversible manner by manipulating the environmental pH. Finally, the last part of this thesis focused on the study of the cytotoxic properties of the early soluble assemblies that populate the fibrillation reaction of functional prion-inspired nanostructures. Overall, this thesis highlights the potentiality of prion-like peptidic sequences to generate bionanomaterials, emphasizing their functional versatility and adaptability for multiple nanotechnological applications. It also proposes that biosafety studies should be routinely implemented during the development of amyloid-based nanomaterials.
Rasel, Md Alim Iftekhar. "Experimental exploration of boron nitride nanoparticle interaction with living cells." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/118067/1/Alim_Rasel_Thesis.pdf.
Повний текст джерелаVila, Vecilla Laura. "Desarrollo de un modelo in vitro de barrera intestinal para la evaluación del riesgo de los nanomateriales." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/398242.
Повний текст джерелаThe field of nanotechnology is increasing every day. For this reason, the social concern about the possible effects of their products (nanomaterials; NMs) in living organisms is also growing. Since the main routes of exposure to NMs are dermal contact, inhalation, and ingestion, the intestinal barrier is very important due to the presence of NMs in food and food packaging, in addition to its presence in many other daily products. In this context, the objective of this Thesis is to develop an intestinal model formed by Caco-2 cells in order to assess the risk of NMs. Caco-2 cells are from colon adenocarcinoma and have the capacity to differentiate into enterocytes of the small intestine. Under the framework of the NANoREG’s project, the results have shown that we have successfully developed a robust protocol to obtain stable and reproducible in vitro intestinal barrier composed of these differentiated Caco-2 cells. Using sub-toxic concentrations of TiO2NPs, ZnONPs, SiO2NPs, CeO2NPs, AgNPS and MWCNT for 24 hours, we have performed different types of analysis: a) assessment of the integrity and permeability of the monolayer, b) cellular internalization, c) translocation of NMs, d) evaluation of genotoxic damage, d) assessment of the integrity of the monolayer through changes in mRNA expression. The results after exposure to sub-toxic concentrations showed no alteration in the integrity or the permeability of the monolayer. Furthermore, internalization of AgNPS was observed in both the cytoplasm and nucleus while TiO2NPs and CeO2NPs found sedimented on the apical membrane of cells. The ability to evaluate the translocation of NMs through the cell barrier proved to be very limited. TEM-EDX, confocal microscopy, and ICP-MS showed limited translocation of TiO2NPs, ZnONPs, and CeO2NPS. In the evaluation of genotoxic damage by comet assay, it was observed that only AgNPS are capable of producing oxidative DNA damage and only at the highest concentration tested (50 μg/mL). In assessing mRNA expression of genes of cellular transporters (SI and SLC15A1) and cell-cell adhesion (OCCLUDIN and CLAUDIN2), results showed a lot of variability between replicates and no significant changes were found in any of them after exposure to AgNPS. Besides the European project and in order to assess the risk of exposure to NMs in the long term, Caco-2 cells in their undifferentiated state were exposed for 6 weeks to sub-toxic concentrations of AgNPS evaluating its transformation capacity. These cells were subjected to a period of adaptation in which the cells decreased the rate of division due to exposure until regaining it at the end of the treatment. After 6 weeks of exposure, the Caco-2 cells expressed some features of the transformed cells: a) increased the proliferation rate, b) acquired the ability to grow in soft agar, and promoted the growth of other tumour cells (HCT116) in soft-agar, c) increased the secretion of MMPs, and d) increased their migratory capacity. However, exposure didn’t show changes in the expression of genes involved in EMT, cell adhesion, cytoskeleton or tumour suppressors. Despite this, the overall results indicate that the AgNPS are not safe in terms of carcinogenesis.
Cakir, Deniz. "Enhanced Raman signatures on copper based-materials." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTS066/document.
Повний текст джерелаThis thesis studies the enhanced Raman signatures on copper based materials. Thin copper films were prepared and studied before and after thermal oxidation in air, under 200 °C. Their microstructure has been characterized by SEM and AFM. The thickness of the copper and cuprous oxide films have been characterized locally by those techniques, and by ellipsometry and UV-visible absorption spectroscopic techniques. A modeling of the UV-visible spectra has been performed based on interference calculations using Fresnel equations, allowing the determination of both the thicknesses and the refractive indices of the films. Raman study of these samples allows a quantification of the interference enhanced Raman phenomenon (IERS). Other copper nanostructured samples covered with single layer graphene (SLG) have been studied, and The Raman intensity of SLG discussed in terms of IERS. The last part of the manuscript is dedicated to SERS studies of molecules deposited on nanostructured golden commercial substrates and to the evolution of the Raman the signal after covering these substrates with a thin copper layer
Santos, Douglas Arnold Silveira Gioielli. "Preparação e caracterização de nanopartículas de metais nobres pelo método de agregação gasosa." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-22102018-031310/.
Повний текст джерелаIn the midst of main advances in material science and technology we can highlight the new techniques of preparation, manipulation and analyses of structures of very small size. They have physical properties (magnetic, electronic and optical) different from those presented by the same material, but in bigger dimension. Noble metal nanoparticles, mainly gold and silver, are incorporated into various technologies in order to take advantage of their optical or electric properties. In this work, we present a technique to produce noble metal nanoparticles by a physical method that also permits to imbed them in a dielectric material matrix. The samples, produced using the gas aggregation technique, were prepared in a nanoparticle gun, developed on one of the guns of a commercial magnetron sputtering system (AJA International). In the nanoparticles generator, atoms are removed from the target and thermalized by the flow of the sputtering working gas, and they are also condensed to form the nanoparticles. The nanoparticles are extracted from the generator aerodynamically and then they proceed to the substrate. Using another gun of the sputtering system we can deposit the nanoparticles produced in a dielectric or metallic matrix. We can also deposit under and capping layers of thin films on the nanoparticles layer produced. The samples of gold and silver nanoparticles produced were characterized by scanning electron microscopy (SEM), Rutherford backscattering analysis (RBS), UV-Visible spectrophotometry and near field optical microscopy (SNOM). In the SEM images, from the distribution and morphology of the nanoparticles it was possible infer the presence of the dielectric matrix, and this was also confirmed by the RBS measurements. Finally, absorbance spectrum of the samples together with the SNOM images have demonstrated the plasmonic character of the samples produced, specially for the NPs co-deposited in the dielectric matrix.