Dissertations / Theses: 'Nanotubes of carbon'

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Brunner, Eric W. "Bioapplications of carbon nanotubes and carbon nanotube assemblies." Thesis, University of Surrey, 2010. http://epubs.surrey.ac.uk/2858/.

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As new materials are discovered, their potential and applications are investigated widely across the various scientific disciplines for general or highly specialized applications. While new nanomaterials such as carbon nanotubes have received the greatest interest for electronics, optics, and structural composites, their applications have also been explored for biological applications such as sensing, selective cell destruction, cellular growth scaffolds, and intracellular delivery of bioactive cargos. Carbon nanotubes are unique materials particularly suited for these applications as they possess characteristic optical and electronic properties in conjunction with large aspect ratios and massive surface areas. The work of this thesis explores the use of carbon nanotubes for cellular growth scaffolds in Chapters 3, tailoring the various properties of these scaffolds in Chapter 4, and their cellular internalization and intracellular locations in Chapter 5. The aim of Chapters 3 and 4 are to create a surface that mimics a cell's natural environment by varying characteristics such as roughness, pore size distribution, wettability, and chemical functionalization of the carbon nanotubes surface. Such variations can have beneficial, detrimental or abnormal effects on the tested cell line as a cell's natural environment within the body consists of a three dimensional mesh of extracellular matrix proteins which is not at all replicated by the commonly used polystyrene tissue culture flask. Carbon nanotubes possess diameters ranging from 0.7 to several nanometers and lengths that can range up to several microns thereby allowing certain types of CNTs to scale with these extracellular matrix proteins and thus impart a nanoscale textured topology that more closely resembles a cell's in vivo environment. Additionally, the replacement of extracted extracellular matrix proteins for coating cellular growth surfaces with synthetic carbon nanotubes eliminates any risk of pathogen contamination and batch-to-batch variability of biological specimens. Fundamental understanding of the interactions between carbon nanotube surfaces and adhered cell cultures will provide a foundation for carbon nanotube applications in 3- dimensional cellular growth scaffolds and tissue implantation devices. Chapter 5 explores the interactions between designed peptides with slight variations in their amino acid sequences and the consequential effects of these peptide interactions with carbon nanotubes for cellular internalization and intracellular location. The efficacy of pharmaceutical drugs and the cellular responses to biomacromolecules depends heavily upon their abilities to transverse the cellular plasma membranes, and exploring the interactions with designed biomolecules such as synthetic peptides provides simple methods for increasing the cellular internalization of carbon nanotubes and altering the intracellular delivery location. The results and methods investigated within these chapters can then be easily applied to other carbon nanotube transporter schemes.,

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Pach, Elzbieta. "Electron microscopy studies on functional carbon nanotubes." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/456581.

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La presente tesis doctoral se centra en el estudio exhaustivo de nanotubos de carbono funcionales por medio de técnicas de microscopía electrónica. Los nanotubos de carbono (CNTs) funcionales están atrayendo una creciente atención debido a su potencial uso para aplicaciones biomédicas, incluyendo para la adquisición de imágenes in vivo, acumulación selectiva en tumores y sistemas de administración de fármacos. Una ventaja intrínseca de los nanotubos de carbono es que su cavidad interna puede llenarse con una carga útil de interés mientras que la superficie externa puede modificarse para mejorar su dispersabilidad y biocompatibilidad. Debido a su potencial aplicación en el campo biomédico, es esencial una caracterización detallada de las muestras en todas las etapas de su proceso de preparación (purificación, acortamiento, llenado y funcionalidad externa). Para lograr este objetivo, en esta tesis doctoral hemos empleado tanto los análisis ya establecidos que incluye microscopía electrónica de transmisión de alta resolución para estudiar la estructura del material de relleno o espectroscopia de dispersión de energía de rayos X para evaluar su composición, pero también hemos explorado el uso de otras técnicas para ampliar las posibilidades de caracterización de las muestras. En este sentido, hemos optimizado las condiciones para el estudio de las longitudes de CNTs monocapa purificados por microscopía electrónica de barrido de alta resolución (HRSEM) con sensibilidad superficial. Además, la microscopía electrónica de transmisión y barrido (STEM) a bajos voltajes se ha demostrado como una técnica eficiente y rápida para evaluar el rendimiento del rellenado y la pureza del material. De hecho, la combinación de alta resolución espacial y el trabajo a bajos voltajes de esta técnica la ha hecho particularmente adecuada para el estudio de la interacción de nanotubos de carbono funcionales con muestras biológicas, como por ejemplo células. Algunos de los compuestos con interés para aplicaciones biomédicas empleados en este trabajo tienen una estructura laminar. Se sabe que los materiales laminares forman monocapas que pueden tener propiedades mejoradas o nuevas debido a efectos de confinamiento. Los CNT pueden actuar como plantillas para guiar los materiales laminares a formar nanotubos monocapa. Este es el caso de los haluros de lutecio y el yoduro de plomo. En esta tesis de doctorado hemos conseguido la formación de nanotubos de haluros de lutecio de tamaño subnanométrico, y su naturaleza tubular se ha demostrado mediante STEM con corrector de aberraciones y simulaciones de imagen. Además, se ha logrado el crecimiento con alto rendimiento de nanotubos de PbI2 en el exterior de CNTs. La estructura de los híbridos se ha revelado mediante STEM con aberración corregida y tomografía electrónica. Cabe destacar que las propiedades ópticas de los híbridos difieren de las del PbI2 en masa. El desplazamiento azul observado por fotoluminiscencia se ha confirmado mediante análisis en híbridos PbI2-CNT individuales por catodoluminiscencia-STEM. En conclusión, durante este proyecto de doctorado la gama de técnicas de microscopía electrónica utilizadas para el estudio de CNT funcionales se ha ampliado para obtener una caracterización exhaustiva de las muestras.
The present PhD thesis focuses on the thorough study of functional carbon nanotubes by means of electron microscopy techniques. Functional carbon nanotubes (CNTs) are attracting an increased attention due to their potential use for biomedical applications, including in vivo imaging, tumour targeting and drug delivery systems. An intrinsic advantage of carbon nanotubes is that their inner cavity can be filled with a chosen payload whilst the outer surface can be modified to improve their dispersability and biocompatibility. Being the envisaged application in the biomedical field, a detailed characterization of the samples in all the steps of the preparation process (namely purification, shortening, filling and external functionalization) is mandatory. To achieve this goal, in this PhD thesis we have employed already established analysis including high resolution transmission electron microscopy to study the structure of the filling material, or energy dispersive X-ray spectroscopy to assess their composition, but also we have explored the use of other techniques to expand the possibilities of characterization of the samples. In this sense, we have optimized the conditions for the study of the lengths of as-purified single-walled CNTs by surface sensitive high resolution scanning electron microscopy (HRSEM). Besides, low voltage scanning transmission electron microscopy (STEM) has been demonstrated as a time-efficient technique for assessment of filling yield and purity. Indeed, the combination of high spatial resolution and low voltage operation of this technique has made it particularly suitable for the study of the interaction of functional carbon nanotubes with biological samples such as cells. Some of the employed compounds with interest for biomedical applications have a layered structure in their bulk form. Layered materials are known to form monolayers which may exert enhanced or novel properties due to the confinement effects. CNTs may act as templates to guide those layered materials to form single-layered nanotubes. This is the case of lutetium halides and lead iodide. In this PhD thesis we have succeeded in the formation of lutetium halide subnanometer-sized nanotubes, and proved their tubular nature by aberration corrected STEM and image simulations. Additionally, the high yield growth of PbI2 nanotubes on the exterior of CNTs has been achieved. Thanks to aberration corrected HAADF STEM and electron tomography, the structure of the hybrids has been revealed. Remarkably, the optical properties of the hybrids differ from those of the bulk PbI2. The blue shift observed by photoluminescence has been further confirmed by cathodoluminescence STEM analysis detected on individual PbI2-CNT hybrids. In conclusion, during this PhD project the range of electron microscopy techniques used for the study of functional CNTs has been expanded to get a thorough characterisation of the samples.

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Fifield, Leonard S. "Functional materials based on carbon nanotubes : carbon nanotube actuators and noncovalent carbon nanotube modification /." Thesis, Connect to this title online; UW restricted, 2003. http://hdl.handle.net/1773/11560.

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Maestro, Luis Fernando. "Aperfeiçoamentos na obtenção de nanotubos de carbono com paredes simples (NTCPS) e possíveis aplicações na estocagem de energia." [s.n.], 2005. http://repositorio.unicamp.br/jspui/handle/REPOSIP/277457.

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Orientador: Carlos Alberto Luengo
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Fisica Gleb Wataghin
Made available in DSpace on 2018-08-04T03:18:18Z (GMT). No. of bitstreams: 1 Maestro_LuisFernando_M.pdf: 1958027 bytes, checksum: cb56dc89c2faea48a95f3fa1350d5666 (MD5) Previous issue date: 2005
Resumo: Desde a sua descoberta em 1991, os Nanotubos de Carbono (NTC) têm atraído muito a atenção da comunidade científica, devido as suas propriedades. Neste trabalho é apresentada uma breve revisão das pesquisas em NTC e algumas definições básicas relevantes para a sua estrutura e propriedades. Em vista da utilização deste material em uma futura aplicação e devido ao interesse do grupo na área de energia, é apresentado o estado da arte do armazenamento de Hidrogênio e, em particular, no armazenamento em sólidos de grande área superficial, classe a qual os NTC pertencem. Apresentam-se as modificações realizadas em um Reator de Arco Elétrico (Forar II) para se realizar a Síntese de NTC, são relatadas as experiências e a caracterização das amostras obtidas utilizando-se Microscopia Eletrônica de Varredura e Espectroscopia Raman.
Abstract: Since their discovery in 1991 Carbon Nanotubes (CNT) have received increasing attention by the scientific community due to their properties. Here is presented a brief review of ongoing CNT research, and basic definitions useful to understand their structure and significant properties. Because of future applications in the energy area, are presented developments in Hydrogen storage, more specifically its adsorption in solids with large internal surface areas, a characteristic of CNT materials. Modifications of the existing FORAR II to obtain CNT by the electric arc method are presented, and a description of the routines employed to obtain CNT. The characterization of catalysts and CNT by Scanning Electron Microscopy and Raman Spectroscopy are presented and discussed.
Mestrado
Física da Matéria Condensada
Mestre em Física

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Martinčić, Markus. "Encapsulation of inorganic payloads into carbon nanotubes with potential application in therapy and diagnosis." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/458136.

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Los nanotubos de carbono representan un grupo de materiales relativamente nuevo con potencial aplicación en diferentes áreas científicas. Esta tesis se centra en beneficiarse de sus cavidades internas para encapsular compuestos biomédicamente relevantes. Los nanotubos de carbono permiten el confinamiento de materiales en su interior impidiendo su fuga y, en consecuencia, reduciendo los efectos secundarios, no deseados, de estos materiales en el medio circundante. Esto hace que los nanotubos de carbono sean unos vectores elegantes para el diagnóstico y tratamiento de enfermedades. Se ha demostrado que el proceso utilizado para purificar muestras de nanotubos de carbono permite no sólo la reducción de impurezas, que podrían causar citotoxicidad, sino también acortar la longitud de los nanotubos. Teniendo en cuenta que el análisis termogravimétrico es una técnica ampliamente utilizada para evaluar la pureza de muestras de nanotubos de carbono, se ha investigado la influencia que tienen diferentes parámetros que controlan este análisis para asegurar que los resultados obtenidos son lo más precisos y representativos posible. El proceso de purificación también ha sido reajustado para minimizar la cantidad de catalizador en muestras de nanotubos de carbono. También hemos desarrollado un protocolo que permite determinar el contenido de catalizador en muestras de nanotubos de carbono mediante espectroscopía ultravioleta-visible de una manera precisa y fiable. Se ha investigado la preparación de cloruro de samario(III) anhidro a partir de óxido de samario(III), así como la capacidad que ofrece el material preparado para el llenado de nanotubos de carbono, ya que éste tiene interés para el desarrollo de radiotrazadores. El proceso de llenado de nanotubos de carbono resulta en muestras que contienen grandes cantidades de material externo, no encapsulado, lo cual puede comprometer el rendimiento del material en el contexto biológico. Hemos desarrollado un protocolo para monitorizar la eliminación del material no encapsulado a través de espectroscopía de ultravioleta-visible, que a la vez permite mejorar el procedimiento de lavado. El uso de nanotubos de carbono multicapa tiene algunos beneficios sobre sus homólogos monocapa debido a la presencia de una cavidad interna más grande que puede contener más material. Se ha investigado el cierre espontáneo de las puntas de nanotubos de carbono multicapa a través de su calentamiento térmico a diferentes temperaturas, así como la encapsulación de distintos materiales en el mismo rango de temperaturas. Finalmente, distintas muestras de nanotubos de carbono multicapa llenos han sido examinadas in-vitro con el fin de evaluar su citotoxicidad y la captación celular de los nanosistemas desarrollados.
Carbon nanotubes present a relatively novel group of materials with potential application in different scientific fields. The scope of this Thesis is to benefit from their inner cavities to encapsulate biomedically relevant payloads. Carbon nanotubes allow the confinement of selected materials within their walls, preventing their leakage and, as a consequence, undesired effects of such materials to the surrounding media. This makes filled carbon nanotubes very elegant vectors for the diagnosis and therapy of diseases. The process used to purify samples of carbon nanotubes proved to be a valuable asset, not only in the reduction of impurities which might cause cytotoxicity, but also for shortening the length of nanotubes. Thermogravimetric analysis is a widely-used technique in evaluating the purity of carbon nanotube samples. The role of different parameters that control the analysis has been investigated to assure that the most appropriate and representative results are obtained. The purification process has also been readjusted to assure the presence of the lowest amount of catalyst possible in the carbon nanotube samples with the employed purification strategy. We have also introduced a simple UV-Vis spectrophotometric assertion of the catalyst content in samples of nanotubes in a precise and reliable manner. The preparation of dry samarium(III) chloride from samarium(III) oxide was investigated, together with the nanotube filling-ability of the prepared material, of interest for the development of radiotracers. Bulk filling of carbon nanotubes results in samples that contain a large amount of external, non-encapsulated material, which can compromise the performance of the material in the biological context. We have developed a protocol to monitor the removal of the non-encapsulated material by means of UV-Vis, which in turn allows improving the washing procedure. The usage of multi-walled carbon nanotubes has some benefits over their single-walled counterparts, due to the presence of a bigger cavity which can host more material. The spontaneous closure of the tips of multi-walled carbon nanotubes by thermal annealing was investigated at different temperatures, along with the encapsulation of different materials. The prepared filled multi-walled samples were tested in-vitro to assess cytotoxicity and cellular uptake of the developed nanosystems.

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Amanatidis, Ilias. "Carbon Nanotubes and Carbon Nanomotors." Thesis, Lancaster University, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.524723.

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Durán, Valdeiglesias Elena. "Study of optical and optoelectronic devices based on carbon nanotubes." Thesis, Université Paris-Saclay (ComUE), 2019. http://www.theses.fr/2019SACLS100/document.

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La photonique silicium est reconnue comme la technologie à même de répondre aux nouveaux défis des interconnexions optiques. Néanmoins, la photonique silicium doit faire face à d'importants défis. En effet, le Si ne peux pas émettre ou détecter de la lumière dans la plage de longueurs d'onde des télécom (1,3 µm à 1,5 µm). Par conséquent, les sources et les détecteurs sont mis en œuvre avec du Ge et des matériaux III-V. Cette approche multi-matériaux complique la fabrication des dispositifs et augmente le coût final du circuit. Cependant, les nanomatériaux ont été identifiés comme alternative pour la mise en œuvre d’émetteurs-récepteurs moins chers et plus petits.Cette thèse est dédiée à l'étude et au développement de dispositifs optiques et optoélectroniques sur la plateforme photonique silicium basés sur l’utilisation de nanotubes de carbone mono paroi (SWCNT). L’objectif principal est de démontrer les blocs fonctionnels de base qui ouvriront la voie à une nouvelle technologie photonique dans laquelle les propietés actives proviennent des nanotubes de carbone.Les nanotubes de carbone ont été étudiés comme matériaux pour la nanoélectronique avec la démonstration de transistors ultra-compacts à hautes performances. De plus, les SWCNTs semi-conducteurs (s-SWCNTs) sont également des matériaux très intéressants pour la photonique. Les s-SWCNTs présentent une bande interdite directe qui peut être ajustée dans la gamme de longueurs d'onde du proche infrarouge en choisissant le bon diamètre. Les s-SWCNT présentent une photoluminescence et une électroluminescence, pouvant être exploitées pour la mise en œuvre de sources de lumière. Ils présentent également diverses bandes d’absorption pour la réalisation de photodétecteurs. Ces propriétés font que les nanotubes de carbone sont des candidats très prometteurs pour le développement de dispositifs optoélectroniques pour la photonique.Le premier objectif de la thèse était l'optimisation des solutions de nanotubes de carbone. Une technique de tri par ultra-centrifugation assistée par polymère a été optimisée, donnant des solutions de haute pureté en s-SWCNT. Sur cette base, plusieurs solutions de s-SWCNTs ont été élaborées pour obtenir des SWCNTs émettant dans les longueurs d'onde comprise entre 1µm et 1,6µm.Le deuxième objectif était d’étudier l'interaction des s-SWCNT avec des guides d'onde silicium et des résonateurs optiques. Plusieurs géométries ont été étudiées dans le but de maximiser l'interaction des s-SWCNT avec le mode optique en exploitant la composante transverse du champ électrique. D'autre part, une approche alternative a été proposée et démontrée en utilisant la composante longitudinale du champ électrique. En utilisant la composante longitudinale, une amélioration de la photoluminescence, un seuil d’émission avec la puissance de pompe ainsi qu’un rétrécissement de la largeur spectrale des résonances dans les microdisques ont été observés. Ces résultats sont un premier pas très prometteur vers la démonstration d’un laser intégré à base de SWNTs.Le troisième objectif était d'étudier les dispositifs optoélectroniques à base de s-SWCNTs. Plus spécifiquement, une diode électroluminescente (DEL) et un photodétecteur ont été développés, permettant la démonstration du premier lien optoélectronique sur puce basé sur les s-SWCNT.Le dernier objectif de la thèse était d'explorer le potentiel de s-SWCNT pour l’optique non linéaire. Il a été démontré expérimentalement, qu’en choisissant la chiralité des s-SWCNTs, le signe du coefficient Kerr pouvait être soit positif ou négatif. Cette capacité unique ouvre un nouveau degré de liberté pour contrôler les effets non linéaires sur puce, permettant de compenser ou d'améliorer les effets non linéaires pour des applications variées
Silicon photonics is widely recognized as an enabling technology for next generation optical interconnects. Nevertheless, silicon photonics has to address some important challenges. Si cannot provide efficient light emission or detection in telecommunication wavelength range (1.3μm-1.5μm). Thus sources and detectors are implemented with Ge and III-V compounds. This multi-material approach complicates device fabrication, offsetting the low-cost of Si photonics. Nanomaterials are a promising alternative route for the implementation of faster, cheaper, and smaller transceivers for datacom applications.This thesis is dedicated to the development of active silicon photonics devices based on single wall carbon nanotubes (SWCNTs). The main goal is to implement the basic building blocks that will pave the route towards a new Si photonics technology where all active devices are implemented with the same technological process based on a low-cost carbon-based material, i.e. SWCNT.Indeed, carbon nanotubes are an interesting solution for nanoelectronics, where they provide high-performance transistors. Semiconducting SWCNT exhibit a direct bandgap that can be tuned all along the near infrared wavelength range just by choosing the right tube diameter. s-SWCNTs provide room-temperature photo- and electro- luminescence and have been demonstrated to yield intrinsic gain, making them an appealing material for the implementation of sources. SWCNTs also present various absorption bands, allowing the realization of photodetectors.The first objective of this thesis was the optimization of the purity of s-SWCNT solutions. A polymer-sorting technique has been developed and optimized, yielding high-purity s-SWCNT solutions. Based on this technique, several solutions have been obtained yielding emission between 1µm and 1.6µm wavelengths.The second objective was the demonstration of efficient interaction of s-SWCNT with silicon photonics structures. Different geometries have been theoretically and experimentally studied, aiming at maximizing the interaction of s-SWCNT with optical modes, exploiting the electric field component transversal to light propagation. An alternative approach to maximize the interaction of s-SWCNT and the longitudinal electric field component of waveguide modes was proposed. Both, a power emission threshold and a linewidth narrowing were observed in several micro disk resonators. These results are a very promising first step to go towards the demonstration of an integrated laser based on CNTs.The third objective was to study optoelectronic SWCNT devices. More specifically, on-chip light emitting diode (LED) and photodetector have been developed, allowing the demonstration of the first optoelectronic link based on s-SWCNT. s-SWCNT-based LED and photodetector were integrated onto a silicon nitride waveguide connecting them and forming an optical link. First photodetectors exhibited a responsivity of 0.1 mA/W, while the complete link yielded photocurrents of 1 nA/V.The last objective of the thesis was to explore the nonlinear properties of s-SWCNT integrated on silicon nitride waveguides. Here, it has been experimentally shown, for the first time, that by choosing the proper s-SWCNT chirality, the sign of the nonlinear Kerr coefficient of hybrid waveguide can be positive or negative. This unique tuning capability opens a new degree of freedom to control nonlinear effects on chip, enabling to compensate or enhancing nonlinear effects for different applications

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Casanova, Cháfer Juan. "Gas Sensing with Modified Carbon Nanotubes, Graphene and Diamondoids." Doctoral thesis, Universitat Rovira i Virgili, 2020. http://hdl.handle.net/10803/669791.

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Aquesta tesi està centrada en el desenvolupament de diferents sensors de gasos mitjançant la modificació de nanomaterials de carboni. Concretament, al llarg d’aquest treball s’han modificat nanotubs de carboni (CNT), grafè i nanodiamants, amb diferents aproximacions. Per exemple, s’ha procedit a la seva decoració amb nanopartícules d’òxids metàl·lics, la formació de monocapes auto-assemblades o la seva funcionalització amb diferents molècules o àtoms, entre altres estratègies. Malgrat que els nanomaterials de carboni presenten extraordinàries propietats electròniques, fisico-químiques, i mecàniques, encara no s’han pogut desenvolupar sensors a escala comercial basats en el seu ús. Açò és a causa de problemes intrínsecs en la detecció de molècules gasoses, com per exemple la seva baixa especificitat i limitada reactivitat. Per tant, en aquesta tesi s’han desenvolupat diversos sensors modificant els diferents nanomaterials de carboni amb la finalitat de millorar paràmetres clau en el sensat de gasos, com poden ser la selectivitat, sensibilitat i temps de resposta. A més a més, s’ha dut a terme una exhaustiva caracterització dels nous nanomaterials desenvolupats mitjançant tècniques espectroscòpiques i microscòpiques. Així mateix, s’han proposat detallats mecanismes de sensat, és a dir, s’han estudiat les interaccions fisico-químiques entre els nanomaterials i els gasos. Per tant, aquest treball ofereix una visió integral per al desenvolupament de nous sensors, des del seu disseny i caracterització, fins als seus principis de funcionament a escala atòmica. A més a més, considerant les inquietuds de la nostra societat, els sensors desenvolupats solen treballar a temperatura ambient, amb la conseqüent dràstica reducció del consum energètic. Com a conclusió, els nanomaterials de carboni desenvolupats són capaços de detectar gasos tòxics, com per exemple el diòxid de nitrogen, a concentracions traça, molt per sota dels límits establerts per la legislació.
Esta tesis está centrada en el desarrollo de distintos sensores de gases mediante la modificación de nanomateriales de carbono. Concretamente, a lo largo de este trabajo se han modificado nanotubos de carbono (CNT), grafeno y nanodiamantes, con distintas aproximaciones. Por ejemplo, se ha procedido a su decoración con nanopartículas de óxidos metálicos, la formación de monocapas autoensambladas o su funcionalización con distintas moléculas o átomos, entre otras estrategias. A pesar de las extraordinarias propiedades electrónicas, físico-químicas y mecánicas de los nanomateriales de carbono, todavía no se han podido desarrollar sensores a nivel comercial basados en su uso. Esto es debido a sus problemas intrínsecos en la detección de moléculas gaseosas, como por ejemplo su baja especificidad y limitada reactividad. Por tanto, en esta tesis se han desarrollado diversos sensores modificando los nanomateriales de carbono con la finalidad de mejorar parámetros clave en la monitorización de gases, como puede ser la selectividad, sensibilidad y tiempos de respuesta. Además, se ha llevado a cabo una exhaustiva caracterización de los nuevos nanomateriales desarrollados mediante técnicas espectroscópicas y microscópicas. Asimismo, se han propuesto detallados mecanismos de detección, es decir, se han estudiado las interacciones físico-químicas entre los nanomateriales y los gases. Por tanto, este trabajo ofrece una visión integral para el desarrollo de nuevos sensores, desde su diseño y caracterización, hasta sus principios de funcionamiento a nivel atómico. Además, considerando las inquietudes de nuestra sociedad, los sensores desarrollados suelen trabajar a temperatura ambiente, con la consiguiente drástica reducción del consumo energético. Como conclusión, los nanomateriales de carbono desarrollados son capaces de detectar gases tóxicos, como por ejemplo el dióxido de nitrógeno, a concentraciones traza, muy por debajo de los límites establecidos por la legislación.
This thesis focuses in the development of different gas sensors through the modification of carbon nanomaterials. In particular, we employed carbon nanotubes (CNT), graphene and diamondoids, with different approaches. For instance, these nanomaterials were either decorated with metal oxide nanoparticles, modified of self-assembled monolayers of thiols or functionalized with different molecules or atoms, among other strategies. Despite the outstanding properties of carbon nanomaterials, such as their electronic, physicochemical and mechanical properties, it has not been possible so far to develop commercial sensors based on these nanomaterials. The main reason is derived from their inherent problems in the gas molecule detection process, such as low specificity and limited reactivity. Thus, we developed new gas sensors by modifying carbon nanomaterials to improve essential gas sensing parameters, such as selectivity, sensitivity and response time. Furthermore, an exhaustive material characterization was carried out through spectroscopic and microscopic techniques. Also, detailed gas sensing mechanisms were proposed, ergo, the physicochemical interactions between nanomaterials and gases were studied. In consequence, this thesis provides a comprehensive vision for the development of new gas sensors employing carbon nanomaterials, from their design and characterization to their working principles at to the atomic scale. In consideration of the social concerns, the sensors developed usually work at room temperature. Therefore, the device power-consumption was drastically reduced. In summary, the modified carbon nanomaterials employed in this thesis can detect harmful gases, such as nitrogen dioxide, at trace concentration, even at lower levels than those established by law as threshold limit values.

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Willey, Anthony D. "Thin Films of Carbon Nanotubes and Nanotube/Polymer Composites." BYU ScholarsArchive, 2012. https://scholarsarchive.byu.edu/etd/3540.

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A method is described for ultrasonically spraying thin films of carbon nanotubes that have been suspended in organic solvents. Nanotubes were sonicated in N-Methyl-2-pyrrolidone or N-Cyclohexyl-2-pyrrolidone and then sprayed onto a heated substrate using an ultrasonic spray nozzle. The solvent quickly evaporated, leaving a thin film of randomly oriented nanotubes. Film thickness was controlled by the spray time and ranged between 200-500 nm, with RMS roughness of about 40 nm. Also described is a method for creating thin (300 nm) conductive freestanding nanotube/polymer composite films by infiltrating sprayed nanotube films with polyimide.

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Sippel-Oakley, Jennifer A. "Charge induced actuation in carbon nanotubes and resistance changes in carbon nanotube networks." [Gainesville, Fla.] : University of Florida, 2005. http://purl.fcla.edu/fcla/etd/UFE0010052.

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Sattari, Andrea Poopak. "Field emission of carbon nanotubes and electroless silver deposition in carbon nanotubes, utilizing carbon nanotubes formed in porous aluminum oxide." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape7/PQDD_0004/MQ45626.pdf.

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12

Vishnubhatla, Kapil Bharadwaj. "Catalyst Immobilization for Patterned Growth of Carbon Nanotubes." University of Cincinnati / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1282053821.

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13

Abraham, Jürgen. "Functionalization of carbon nanotubes." [S.l.] : [s.n.], 2005. http://deposit.ddb.de/cgi-bin/dokserv?idn=97712293X.

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14

Korneva, Guzeliya Gogotsi IU G. Schweitzer-Stenner Reinhard. "Functionalization of carbon nanotubes /." Philadelphia, Pa. : Drexel University, 2008. http://hdl.handle.net/1860/2797.

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15

Samsonidze, Georgii G. "Photophysics of carbon nanotubes." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/38921.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2007.
Includes bibliographical references (leaves 213-233).
This thesis reviews the recent advances made in optical studies of single-wall carbon nanotubes. Studying the electronic and vibrational properties of carbon nanotubes, we find that carbon nanotubes less than 1 nm in diameter exhibit dramatic changes in their electron and phonon dispersion relations due to the curvature of the nanotube sidewall and the enhanced electron correlation effects associated with one dimensionality. The optical transition energies in small-diameter carbon nanotubes show a strong dependence on their geometrical structure, as was first observed in the photoluminescence experiments. The frequencies of the Raman-active phonon modes also become very sensitive to the geometrical structure of small-diameter carbon nanotubes. In particular, certain phonon modes exhibit anomalous behavior that significantly affects resonance Raman spectra of small-diameter carbon nanotubes. We have developed the extended tight-binding and advanced force-constant models that properly take into account the curvature effects in the small-diameter limit. The many-body corrections are fitted to the photoluminescence and resonance Raman spectroscopy data.
(cont.) The resulting extended tight-binding model with semiempirical many-body corrections shows a good agreement with the experimental results. The electron-photon and electron-phonon transition matrix elements are calculated within the framework of the extended tight-binding model. Finally, the photoluminescence and Raman intensities in the graphene sheet and carbon nanotubes are calculated. The calculated intensities show a reasonable agreement with the experimental results and allow structural characterization of carbon nanotubes by their spectroscopic signatures.
by Georgii G. Samsonidze.
Ph.D.

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16

Singh, Charanjeet. "Synthesis of carbon nanotubes." Thesis, University of Cambridge, 2002. https://www.repository.cam.ac.uk/handle/1810/272043.

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17

Sandoval, Rojano Stefania. "Functionalization of carbon nanomaterials with nitrogen, halides and oxides." Doctoral thesis, Universitat Autònoma de Barcelona, 2016. http://hdl.handle.net/10803/394000.

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Los materiales compuestos por grafeno y nanotubos de carbono (CNTs) han despertado un amplio interés debido a sus propiedades excepcionales. La variación de éstas, empleando diversas técnicas de modificación aumentan sus aplicaciones potenciales en muchos campos. Ésta tesis describe la funcionalización de nanomateriales de carbono con nitrógeno y diversos haluros y óxidos. La modificación de la estructura de nanotubos de carbono multicapa (MWCNTs) y derivados de grafeno se llevó a cabo mediante reacciones sólido-gas y sólido-líquido. Hemos empleado diferentes métodos de funcionalización, que incluyen oxidación, funcionalización con nitrógeno y dopaje, así como modificaciones de las cavidades internas y superficies externas de los nanotubos de carbono, para modular las propiedades de las nanoestructuras preparadas. Mediante un estudio sistemático de las condiciones de tratamiento y una exhaustiva caracterización se determinaron las características estructurales de las muestras y se evaluaron algunas de sus propiedades fisicoquímicas. En ésta tesis proponemos un método simple, eficiente y reproducible para la síntesis de óxido de grafeno reducido (RGO) modificado con nitrógeno. La naturaleza de los átomos de nitrógeno dentro de la red del RGO se ha modulado mediante tratamientos de amonolísis de óxido de grafeno (GO) a temperaturas comprendidas entre 25 ˚C y 800 ˚C. El protocolo propuesto permite tanto la introducción de grupos funcionales alifáticos (funcionalización con N) como la de nitrógeno estructural (dopaje con N). Adicionalmente, la composición estructural de las muestras funcionalizadas y dopadas con nitrógeno se modificó mediante tratamientos posteriores empleando altas temperaturas y atmosferas no oxidantes. Éstos tratamientos provocan rearreglos internos que confieren mayor estabilidad térmica a los materiales. Por otro lado, se llevó a cabo el llenado de las cavidades y la decoración de las superficies externas de los MWCNTs con compuestos inorgánicos. Reportamos la formación de nanotubos inorgánicos monocapa dentro de los nanotubos de carbon empleando una técnica de capilaridad del material laminar en su fase fundida. Además, mediante la optimización de los parámetros experimentales conseguimos favorecer el crecimiento de éstos sistemas inorgánicos monocapa con respecto la formación de otras nanoestructuras, tales como, nanopartículas, nanobarras y nanoserpientes de los halogenuros empleados. Hemos descrito una nueva técnica para el aislamiento ó liberación de las sustancias previamente introducidas en las cavidades de los MWCNTs. Así, exploramos el uso potencial de los fulerenos como agentes aisladores o promotores de la liberación de estructuras huéspedes. Finalmente, hemos preparado MWCNTs decorados con óxidos de titanio reducidos empleando tratamientos a altas temperaturas. Mediante la oxidación de los nanotubos se obtuvieron “nanocollares” de titania libres de carbono. Los materiales soportados presentan una actividad fotocatalítica superior a la del material de referencia titania P25.
Graphene and carbon nanotubes (CNTs) are of wide interest in materials science due to their outstanding properties. Several approaches allow modulating their properties further expanding their potential applications in many fields. This thesis reports on the functionalization of carbon nanomaterials with nitrogen, halides and oxides. The modification of the structure of multiwalled carbon nanotubes (MWCNTs) and graphene derivatives has been carried out through solid-gas and solid-liquid reactions. Different methods of functionalization, which include oxidation, nitrogen functionalization and doping, as well as endohedral and exohedral modifications have been employed for tuning the properties of the prepared nanostructures. A systematic study of the conditions of treatment and an extensive characterization has allowed the determination of the structural characteristics of the samples and the evaluation of some of their physical and chemical properties. In this thesis we propose a simple, efficient and reproducible method for the synthesis of nitrogen-containing reduced graphene oxide (RGO). The nature of the nitrogen atoms within the RGO lattice has been tuned by ammonolysis treatments of graphene oxide (GO) in the range of 25 ˚C-800 ˚C. The reported protocol allows the introduction of aliphatic moieties (N-functionalization) and structural nitrogen (N-doping). Additionally, the structural composition of the N-containing RGO has been modified by post-annealing the material under non-oxidizing atmospheres. High temperature treatments induce internal rearrangements, leading to samples with an enhanced thermal stability. On the other hand, endohedral and exohedral functionalization of MWCNTs with inorganic materials have been carried out. We report on the formation of single-layered inorganic nanotubes within the cavities of MWCNTs through a molten phase capillary wetting technique. We have optimized the conditions of the synthesis to enhance the growth of the single-layered nanotubes, while decreasing the formation of other nanostructures (nanoparticles, nanorods and nanosnakes). A new technique for the confinement and/or release of the filled substances within the hollow cavity of the CNTs has also been developed. We have explored the potential of fullerenes as corking agents and as promoting species for the release of guest structures. Finally, we have prepared MWCNTs decorated with reduced titanium oxides employing high temperature treatments. By oxidation of MWCNTs self-standing titania “nano-necklaces” are formed. The photocatalytic performance of the carbon supported materials overpasses that of the reference material titania P25.

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Eberhardt, Oliver, and Thomas Wallmersperger. "Molecular mechanics methods for individual carbon nanotubes and nanotube assemblies." SPIE, 2015. https://tud.qucosa.de/id/qucosa%3A35032.

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Since many years, carbon nanotubes (CNTs) have been considered for a wide range of applications due to their outstanding mechanical properties. CNTs are tubular structures, showing a graphene like hexagonal lattice. Our interest in the calculation of the mechanical properties is motivated by several applications which demand the knowledge of the material behavior. One application in which the knowledge of the material behavior is vital is the CNT based fiber. Due to the excellent stiffness and strength of the individual CNTs, these fibers are expected to be a promising successor for state of the art carbon fibers. However, the mechanical properties of the fibers fall back behind the properties of individual CNTs. It is assumed that this gap in the properties is a result of the van-der-Waals interactions of the individual CNTs within the fiber. In order to understand the mechanical behavior of the fibers we apply a molecular mechanics approach. The mechanical properties of the individual CNTs are investigated by using a modified structural molecular mechanics approach. This is done by calculating the properties of a truss-beam element framework representing the CNT with the help of a chemical force field. Furthermore, we also investigate the interactions of CNTs arranged in basic CNT assemblies, mimicking the ones in a simple CNT fiber. We consider the van-der-Waals interactions in the structure and calculate the potential surface of the CNT assemblies.

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19

Kierkowicz, Magdalena. "Development of carbon nanocapsules for biomedical applications." Doctoral thesis, Universitat Autònoma de Barcelona, 2017. http://hdl.handle.net/10803/458543.

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La alta superficie y el hueco interior de los nanotubos de carbono (del inglés CNTs) los convierte en candidatos ideales para el desarrollo de nanovectores inteligentes para su aplicación en nanomedicina. Su cavidad interna puede emplearse para alojar compuestos seleccionados para propósitos de diagnóstico o terapéuticos, mientras que las paredes externas pueden modificarse para aumentar su biocompatibilidad e incluso para su direccionamiento. Un reto importante para trasladar los sistemas basados en CNT a su uso clínico es la reducción o eliminación de su toxicidad. Teniendo en cuenta la preocupación sobre salud y seguridad de nanomateriales, se han intensificado los esfuerzos de investigación para mejorar la biocompatibilidad de los CNTs, incluyendo el desarrollo de nuevas estrategias para el acortamiento y purificación de los mismos. La primera parte de esta tesis se enfoca en el estudio de la influencia del vapor de agua sobre la longitud, pureza y la integridad de las paredes de los nanotubos de carbono monocapa (del inglés SWCNTs) producidos tanto por deposición catalítica en fase de vapor (del inglés CVD ) como por descarga de arco. Para obtener nanotubos de carbono individualizados desarrollamos un protocolo que consiste en dispersar las muestras en orto-diclorobenceno y hemos empleado microscopía electrónica de barrido para adquirir las imágenes. CVD CNTs cortos con una longitud media de aprox. 200 nm se obtienen después de 10 h de tratamiento con vapor de agua, mientras que los CNT sintetizados por descarga de arco muestran una baja reactividad frente el vapor de agua. También se investigó la eficiencia de otros métodos de acortamiento comúnmente empleados, como son la molienda de bolas, una mezcla de ácido sulfúrico/nítrico y el tratamiento con piraña, tanto para SWCNTs como para CNTs multicapa (del inglés MWCNT) producidos por CVD. La combinación de piraña y vapor de agua resultó ser la más eficiente para el acortamiento de SWCNTs, y la combinación de ácido sulfúrico/nítrico con vapor de agua para MWCNTs. Estos protocolos proporcionan un buen equilibrio entre la obtención de nanotubos cortos con una distribución de longitud pequeña y la pureza de las muestras con un alto rendimiento de producción. En la segunda parte, estudiamos la encapsulación de distintos haluros metálicos, de interés tanto para imagen como para terapia, dentro de SWCNTs preparados por CVD y por descarga de arco. Se ha investigado el papel que juega la temperatura de calientamiento en el grado de cierre de las puntas de los nanotubos de carbono. Este estudio ha permitido la preparación de CNTs llenos con haluros metálicos de forma eficiente. El llenado de nanotubos de carbono da lugar a muestras que contienen una gran cantidad de material no encapsulado, externo a los nanotubos de carbono, que puede afectar e incluso dominar las propiedades de los nanotubos de carbono llenos. Por lo tanto, desarrollamos un protocolo que permite la eliminación de compuestos no encapsulados en poco tiempo y respetuoso con el medio ambiente, utilizando agua como solvente "verde" en un sistema Soxhlet, a la vez que se minimiza la cantidad de agua residual. La última parte de la tesis describe la modificación de las paredes externas de CNTs llenos. SWCNTs se han funcionalizado covalentemente a través de las reacciones de Tour y Prato, la primera resultando en un grado de funcionalización mayor. Para completar el estudio, las paredes externas de MWCNT llenos con cloruro de lutecio fueron decoradas con nanopartículas de oro. Estas nanocápsulas híbridas tienen interés para su uso como agentes duales para el diagnóstico y la terapia. En resumen, esta tesis aporta nuevos conocimientos sobre la preparación de nanocápsulas de carbono, para el desarrollo de la siguiente generación de agentes teranósticos.
The high surface area and hollow core of carbon nanotubes (CNTs) make them ideal candidates for the development of smart nanovectors in nanomedicine. Their inner cavity can be employed to host selected payloads for either diagnosis or therapeutic purposes while the external walls can be modified to increase their biocompatibility and even for targeting purposes. A major challenge to turn the potential of CNT based devices into customer applications is to reduce or eliminate their toxicity. Taking into account health and safety concerns, intensified research efforts are conducted to improve the biocompatibility of CNTs, including the development of new shortening and purification strategies. The first part of this thesis focused on the influence of steam on the length, purity, and sidewall integrity of chemical vapor deposition (CVD) and arc discharge single-walled carbon nanotubes (SWCNTs). In order to obtain individualized carbon nanotubes we developed a protocol that consisted of dispersing the samples in ortho-dichlorobenzene and employed scanning electron microscopy (SEM) to acquire the images. Short CVD CNTs with median length of ca. 200 nm can be obtained after 10 h of steam treatment, whereas arc discharged CNTs show low reactivity towards steam. The efficiency of other commonly employed shortening methods, namely ball milling, sulfuric/nitric acids, and piranha was also investigated for both SWCNT and multi-walled CNTs (MWCNTs) grown by CVD. A combination of piranha and steam turned out to be the most efficient for SWCNTs, and a combined sulfuric/nitric acids and steam for MWCNTs. These protocols provide a good balance between length distribution, sidewall integrity and purity of samples with a high yield of production. In the second part, we report on the encapsulation of selected metal halides, of interest for both imaging and therapy, inside CVD and arc discharge SWCNTs. The role of temperature on the degree of end-closing has been investigated, which has allowed the preparation of closed-ended metal halide filled CNTs. Bulk filling of carbon nanotubes results in samples that contain a large amount of non-encapsulated material, external to the carbon nanotubes, which can affect and even dominate the properties of filled carbon nanotubes. Therefore, we developed a straight forward approach that allows the removal of non-encapsulated compounds in a time efficient and environmentally friendly manner, using water as a “green” solvent in a Soxhlet setup, while minimizing the residual waste. The last part of the thesis describes the external modification of previously filled CNTs. SWCNTs have been covalently functionalized via Tour and Prato reactions, the former resulting in a higher degree of functionalization. To complete the study, lutetium chloride filled MWCNTs were externally decorated with gold nanoparticles. The developed hybrid nanocapsules hold potential to be employed as dual agents for diagnosis and therapy. To summarize, this thesis brings new insights in the preparation of carbon nanocapsules, i.e. close-ended filled carbon nanotubes with chosen payloads, for the development of the next generation of theranostic agents.

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Yu, Zhixin. "Synthesis of Carbon Nanofibers and Carbon Nanotubes." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemical Engineering, 2005. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-508.

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Carbon nanofibers (CNFs) and carbon nanotubes (CNTs) have attracted intense research efforts with the expectation that these materials may have many unique properties and potential applications. The most promising way for large-scale synthesis of CNFs and CNTs is chemical vapor deposition (CVD).

CNFs were synthesized on a series of hydrotalcite (HT) derived 77 wt.% Ni-Fe/Al₂O₃ catalysts in order to achieve the optimization of productivity and quality. It was found that only the Fe catalyst was active in CO disproportionation and only the Ni catalyst was active in ethylene decomposition, whereas all catalysts were active in ethylene decomposition when the reactants were a mixture of C₂H₄/CO. More control over the structure and diameter of the CNFs has been realized with the HT catalysts. At the same time, a high yield can be obtained. The synthesis process has been further studied as a function of various process parameters. It turned out that high hydrogen concentration, space velocity, and reaction temperature would enhance the production of CNFs. However, a slightly lower quality was associated with the higher productivity. The optimum CNF yield of 128 gCNF/gcat could be reached within 8 h on the HT catalyst with a Ni/Fe ratio of 6:1. Therefore, HT derived catalysts present a new promising route to large-scale controlled synthesis of CNFs.

CNTs has been synthesized from CO disproportionation on Ni-Fe/Al₂O₃ supported catalysts with metal loadings of 20 and 40 wt.%. A high space velocity resulted in a high production rate but a short lifetime and a low carbon capacity. Increasing the metal loading to 40 wt.% significantly increased the reaction rate and productivity, and produced similarly uniform CNTs. Furthermore, H₂was found to be necessary for a high productivity, and the H₂partial pressure could be changed to adjust the orientation angle of the graphite sheets.

The effects of catalyst particle size and catalyst support on the CNT growth rate during CO disproportionation were studied over SiO₂and Al₂O₃ supported Fe catalysts with varying particle sizes. It was found that there was an optimum particle size at around 13-15 nm for the maximum growth rate, and the growth rate was influenced both by the particle size and the support but the particle size was the dominating factor. The trends have been demonstrated at two different synthesis temperatures of 600 and 650°C. The effect of gas precursors on the yield and structure of carbon growth has been systematically investigated over powder Fe and Fe/Al₂O₃ catalysts. CO/H₂, CO, CH₄, and C₂H₆/H₂were the gas precursors studied. The carbon yield was higher on powder Fe from CO, but the yield was higher on Fe/Al₂O₃ from hydrocarbons. Completely different or similar carbon nanostructures were synthesized, depending on the gas precursors. It was suggested that the reactivity of gas precursors and the structures of carbon deposits are determined by the size and crystallographic faces of the catalyst particles, which are dictated by the interactions among metal particles, support, and the reactants. Controlled synthesis of CNT, platelet nanofiber, fishbone-tubular nanofiber, and onion-like carbon with high selectivity and yield was realized. A mechanism was proposed to illustrate the growth of different carbon nanostructures.

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Pereira, Aline Cristina [UNESP]. "Estudo da cinética de cura e das propriedades térmicas da resina benzoxazina e de seus compósitos nanoestruturados." Universidade Estadual Paulista (UNESP), 2011. http://hdl.handle.net/11449/94420.

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Made available in DSpace on 2014-06-11T19:27:11Z (GMT). No. of bitstreams: 0 Previous issue date: 2011-07-06Bitstream added on 2014-06-13T18:31:00Z : No. of bitstreams: 1 pereira_ac_me_guara.pdf: 1301531 bytes, checksum: bc9fd4753c17ea915b6f6ca3419e26a1 (MD5)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
As resinas polibenzoxazinas constituem uma nova classe de resinas fenólicas termorrígidas que surgiram nas últimas décadas, superando as propriedades das tradicionais resinas epóxi e fenólicas aplicadas na indústria aeroespacial. A incorporação de baixa concentração em massa de nanotubo de carbono (NTC) em matrizes poliméricas pode produzir materiais estruturais com propriedades superiores. Nesse sentido, o presente trabalho tem como objetivo a preparação de compósitos nanoestruturados de resina benzoxazina/NTC, bem como o estudo da cinética de cura da resina benzoxazina e de seus compósitos nanoestruturados. Além disso, objetiva-se, ainda, a caracterização térmica da resina benzoxazina curada e de seus compósitos nanoestruturados também curados pelo mesmo ciclo de cura. O estudo da cinética de cura foi realizado por meio da técnica de calorimetria exploratória diferencial (DSC) sob condições não-isotérmicas (dinâmicas). A caracterização térmica foi realizada por meio do uso de termogravimetria, da análise dinâmico-mecânica, da análise termomecânica, do DSC e por análises de espectroscopia de infravermelho com transformada de Fourier e microscopia eletrônica de varredura. A partir destas análises, concluiu-se, de maneira geral, que os nanotubos de carbono agem como catalisadores da cura da matriz de benzoxazina sem afetar suas temperaturas iniciais e finais de polimerização. A adição de NTC não modifica a estabilidade térmica da resina benzoxazina e nem a temperatura de transição vítrea (Tg) dos compósitos nanoestruturados, com exceção da adição de 0,1% em massa de NTC na matriz polimérica que gera um aumento na Tg
Polibenzoxazine resins are a new class of thermosetting phenolic resins that have emerged in recent decades, overcoming the traditional properties of epoxy and phenolic resins applied in the aerospace industry. The addition of small amount of carbon nanotube in polymeric matrices can produce superior structural materials. Thus, this work aims to prepare nanostructured composite benzoxazine resin/NTC as well the study of the cure kinetic of neat benzoxazine resin and their nanostructured composites produced. Moreover, the objective is also the thermal characterization of cured neat benzoxazine resin and their composites nanostructured also cured by the same cure cycle. The study of cure kinetics was performed using the technique of differential scanning calorimetry (DSC) under non-isothermal (dynamic). The thermal characterization was performed by using thermogravimetry, dynamic mechanical analysis, thermomechanical analysis, DSC analysis and infrared spectroscopy with Fourier transformed and scanning electron microscopy. From these tests, it can be concluded, in general, that the carbon nanotubes act as catalysts for curing the benzoxazine matrix without affecting the initial and final temperatures of polymerization. The addition of CNT does not change neither the thermal stability of the benzoxazine resin nor the glass transition temperature (Tg) of nanostructured composites, except for the addition of 0.1 wt% of CNT in polymer matrix that generates a slight increase in Tg

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Miranda, Reyes Cesar Alejandro. "Thermoelectric properties of carbon nanotube films." Thesis, University of Cambridge, 2019. https://www.repository.cam.ac.uk/handle/1810/289715.

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Thermoelectric generators are solid state machines used to convert temperature gradients into electrical energy. They are formed by several thermoelectric units connected electrically in series and thermally in parallel. These units are made by creating a junction between a p-type and an n-type conductor. This investigation documents the characterisation of the thermoelectric properties of carbon nanotube (CNT) films and the fabrication process of carbon nanotube-based thermoelectric devices. The Seebeck coefficient is a intrinsic property of a thermoelectric material that correlates the voltage produced by a conductor and the temperature gradient applied to it. To measure the Seebeck coefficient of films, an experimental set-up was fabricated and calibrated using constantan as standard material. CNT films of aligned nanotubes fabricated using a chemical vapour deposition method were analysed. The Seebeck coefficient along and across the samples did not show significant variations, with values between 40$\mu$V/K and 80$\mu$V/K. Using these CNT films, thermoelectric cells were fabricated with the CNT as the p-type conductor and constantan as the n-type. As a proof of concept, two hand-made thermoelectric generators were assembled by connecting hundreds of these thermoelectric cells. These devices were subjected to a temperature gradient of $\approx$200K, which was enough to produce enough power to light an LED. Other analytical techniques were used to characterise the materials used in this work. Electrical conductivity measurements, thermogravimetric analysis, Raman spectroscopy and scanning electron microscopy were performed. Using a deposition technique, films of nanotubes were produced from a liquid phase. The impact of the production method on their properties was evaluated. Characterisation equipment was developed to measure the Seebeck coefficient and thermal conductivity. Thermoelectric devices made with the carbon nanotube films were fabricated and characterised. The values of thermal conductivity of the CNT films analysed in this work are between 0.86Wm$^{-1}$K$^{-1}$. The electrical conductivity of these materials is between 3500Sm$^{-1}$ and 14100Sm$^{-1}$. The maximum figure of merit of the carbon nanotube thermoelectric devices fabricated in this work is $ZT$=0.35.

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PRADHAN, NIHAR R. "Thermal Conductivity of Nanowires, Nanotubes and Polymer-Nanotube Composites." Digital WPI, 2010. https://digitalcommons.wpi.edu/etd-dissertations/112.

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Ever rising power densities and smaller transistor dimensions are increasing the challenge of thermal management within integrated-circuit chips and their surrounding packaging. In addition, the need for sustainable energy has placed urgent emphasis on energy conversion. Thermoelectric phenomena, involving the conversion of heat to electrical current, provide a central focus for both needs. Specifically, there is a need to engineer materials or composites with low thermal conductivity and high electrical conductivity for energy conversion and the opposite for heat management. In this presentation, experimental results will be presented of the specific heat and thermal conductivity of cobalt nanowires (CoNW), carbon nanotubes (CNT) and polymer-carbon nanotubes, in various composite arrangements with our high precession Calorimetric technique. Due to the nature of these samples, boundary and defect scattering of phonons in nanomaterials can dominate. This scattering phenomena shows decreasing thermal conductivity in metal nanowires, turns to be good for thermoelectric application. For the CNT, and possibly due to the high volume per atom leading to ballistic phonon propagation, the observed thermal conductivity along the nanotube direction, which leads to manage the heat dissipation problem in integrated circuits (ICs) and microprocessors. The thermal conductivity of a single Single-Wall Carbon Nanotube (SWCNT) was found to be 6600 W/mK, theoretically, twice that of diamond. When such high thermal conductivity materials are dispersed in a low thermal conducting polymer (PMMA), the effective thermal conductivity and thermal stability of the composite can change dramatically. The experimental results show good agreement with theoretical model proposed by Nelsen, Hamilton, Crosse, Geometric, and Xue. The thermal relaxation phenomena such as glass transition temperature (Tg) and dynamics of the molecules in the polymer-nanotubes composites, changes significantly different than the pure polymers during thermal treatment and is one of the focusing point of this presentation. Liquid crystalline materials confined to restrictive nano-channels are of great interest in many potential applications of electro-optics and display technology. This part of the presentation investigates the unexplored phenomenon of the coating and filling of 8CB and 10CB liquid crystals inside ~200nm diameter Multi-Wall Carbon nanopipes. The phase transition characteristics of the confined liquid crystal films were studied using MDSC technique and will be the last part of this presentation.

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24

Pantoja, Suárez Luis Fernando. "Carbon nanotubes grown on stainless steel for supercapacitor applications." Doctoral thesis, Universitat de Barcelona, 2019. http://hdl.handle.net/10803/667708.

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The ability of humans to study, manipulate and understand matter at the nanoscale has enabled us to develop materials that can combine physical, chemical, optical, magnetic and mechanical properties that bulk materials do not possess. One of the materials that triggered interest in the world of Nanoscience and Nanotechnology was carbon nanotubes (CNTs). These nanostructures had already been reported more than forty years ago, but it is not until the beginning of the 90s that Dr. Sumio Iijima manages to produce them under stable conditions in his laboratory. From that time onwards, the resources devoted to the research and production of these carbon-based materials were on the rise. Although today they do not capture the same scientific interest as they did until 2010, their importance in the scientific world and especially in the market is relevant. In fact, since the technology for the production of CNTs on an industrial scale has matured, they are found in an infinite number of applications, such as reinforcing polymers, acting as scaffolds for the growth of artificial tissue, in the manufacture of conductive inks or as part of new generation battery electrodes and supercapacitors. It is precisely in this last application that scientific interest has been focused with special attention. Together with other carbon-based materials, such as graphene, they are excellent support materials for materials with high capacitance. Research groups and companies around the world are spending a lot of resources to obtain electrodes that have a three-dimensional architecture at the nanoscale and whose specific surface is high. In that sense, the objective of this work was to synthesize CNTs on the surface of a flexible and conductive material: 304 stainless steel. We focused on optimizing the growth processes by plasma enhanced chemical vapor Deposition (PECVD) and water assisted chemical vapor deposition (WACVD) with and without the contribution of external catalyst material. In addition, as will be seen in the development of this work there is an important effort to understand the effects that thermal processes, necessary for CNTs growth, produced on the properties of steel. Especially the influence on corrosion resistance, since the final use of stainless steel CNTs is the manufacture of electrodes exposed to corrosive environments.
La capacidad de los seres humanos para estudiar, manipular y comprender la materia a escala nanométrica nos ha permitido desarrollar materiales que pueden combinar propiedades físicas, químicas, ópticas, magnéticas y mecánicas que los materiales a granel no poseen. Uno de los materiales que despertó el interés en el mundo de la Nanociencia y la Nanotecnología fueron los nanotubos de carbono (CNTs por sus siglas en inglés). Estas nanoestructuras ya habían sido reportadas hace más de cuarenta años, pero no es hasta principios de los años 90 que el Dr. Sumio Iijima logra producirlas en condiciones estables en su laboratorio. A partir de ese momento, los recursos dedicados a la investigación y producción de estos materiales basados en el carbono fueron en aumento. Aunque hoy en día no captan el mismo interés científico que hasta 2010, su importancia en el mundo científico y especialmente en el mercado es relevante. De hecho, ya que la tecnología para la producción de CNTs a escala industrial ha madurado, estos se encuentran en un gran número de aplicaciones, tales como en el refuerzo de polímeros, actuando como andamiajes para el crecimiento de tejidos artificiales, en la fabricación de tintas conductoras o como parte de los electrodos para baterías y de los supercondensadores de nueva generación. Es precisamente en esta última aplicación donde el interés científico se ha centrado con especial atención. Junto con otros materiales a base de carbono, como el grafeno, son excelentes materiales de soporte para materiales con alta capacitancia. Los grupos de investigación y las empresas de todo el mundo están invirtiendo muchos recursos en la obtención de electrodos que tienen una arquitectura tridimensional a nanoescala y cuya superficie específica es elevada. En ese sentido, el objetivo de este trabajo fue sintetizar CNTs sobre la superficie de un material flexible y conductor: el acero inoxidable 304. Nos centramos en la optimización de los procesos de crecimiento mediante el depósito químico en fase de vapor asistido por plasma (PECVD por sus siglas en inglés) y el depósito químico en fase de vapor asistido por agua (WACVD por sus siglas en inglés) con y sin la contribución de material de catalizador externo. Además, como se verá en el desarrollo de este trabajo, hubo un esfuerzo importante para entender los efectos que los procesos térmicos, necesarios para el crecimiento de CNTs, producen sobre las propiedades del acero. Especialmente la influencia en la resistencia a la corrosión, ya que el uso final de los CNTs en acero inoxidable es la fabricación de electrodos expuestos a ambientes corrosivos.

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25

Parlapalli, Rohit. "Effect of twist on load transfer and tensile strength in carbon nanotube bundles." University of Cincinnati / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1382372894.

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26

Papadopoulos, Christo. "Nanotube engineering and science, synthesis and properties of highly ordered carbon nanotube arrays and Y-junction carbon nanotubes." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 2000. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape4/PQDD_0018/MQ53443.pdf.

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27

Montalti, Massimo. "Spectroscopical investigation of carbon nanostructures : carbon nanotubes and carbon onions." Thesis, University of Newcastle Upon Tyne, 2004. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.413968.

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28

Zhu, Mingyao. "Carbon nanosheets and carbon nanotubes by RF PECVD." W&M ScholarWorks, 2006. https://scholarworks.wm.edu/etd/1539623509.

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A planar antenna RF plasma enhanced chemical vapor deposition apparatus was built for carbon nanostructure syntheses. When operated in inductive and capacitive plasma discharging modes, two carbon nanostructures, carbon nanotube (CNT) and carbon nanosheet (CNS), were synthesized, respectively.;A nanosphere lithography method was developed and used to prepare catalyst patterns for CNT growth. Using capacitively coupled C2H2/NH 3 plasma, randomly oriented CNT were synthesized on Ni dot patterned Si substrates. Aligned CNT arrays were grown on SiO2 coated Si substrates, using both C2H2/NH3 and CH 4/H2 capacitive plasmas.;When operated in inductive coupling mode, CNS were successfully deposited on a variety of substrates without any catalyst. Carbon nanosheets are a novel two-dimensional structure, have smooth surface morphologies and atomically thin edges, and are free-standing roughly vertical to substrate surfaces. CNS have a defective graphitic crystalline structure, and contain only C and H elements. Typical CNS growth parameters are 680??C substrate temperature, 40% CH4 in H2, 900 W RF power, and 100 mTorr total gas pressure. Morphology, growth rate, and structure of CNS change with the variations in the growth parameters. Increasing substrate temperature yields a less smooth morphology, a faster growth rate, and more defects in CNS; increasing CH 4 concentration causes a faster growth rate and more defects in CNS, but only slightly changes the morphology; increasing RF power results in a more smooth morphology, a faster growth rate, and less defects in CNS; and decreasing total gas pressure induces a less smooth morphology, a faster growth rate, and more defects in CNS.;In CNS growth mechanism, a base layer forms underneath the vertical sheets; the growth of CNS is through growth species surface diffusion; the electric field near substrate surfaces promotes and keeps the vertical orientation of the CNS, and the atomic hydrogen etching keeps the CNS atomically thin.;Carbon nanosheets have large surface areas, and can stabilize metal thin films into particles 3-5 nm in diameters. For field emission testing, typical CNS have turn-on fields of 5-10 V/mum, a maximum emission current of 28 mA, an emission current density of 2 mA/mm2, and a life-time of 200 hours.

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29

Choi, Yongho. "Growth, fabrication, and characterization of carbon nanotubes, nanotube films, and nanowires." [Gainesville, Fla.] : University of Florida, 2008. http://purl.fcla.edu/fcla/etd/UFE0022789.

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30

Yaghoobi, Parham. "Electron emission from carbon nanotubes." Thesis, University of British Columbia, 2009. http://hdl.handle.net/2429/7112.

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In this thesis, I will provide an overview of the subject from various experimental and theoretical angles with an emphasis on the limited number of theoretical works that exist in calculating the emission current. I will then present a first-principles calculation of the emission current in a single-walled carbon nanotube using the non-equilibrium Green's function and Fisher-Lee's transmission formulation to describe electronic transport through the system. The simulation results reproduce the trends observed in experimental data closely and, in particular, the current saturation behavior observed in experiments and the deviation from the Fowler-Nordheim behavior. The proposed numerical approach is useful whenever a region of vacuum is present in the device Hamiltonian, which existing commercial transport solvers do not model. To better characterize nanotube electron sources, I have also done some preliminary experimental work, which has involved building equipments and developing recipes for growing carbon nanotubes.

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31

Goh, Roland Ghim Siong. "Carbon nanotubes for organic electronics." Queensland University of Technology, 2008. http://eprints.qut.edu.au/20849/.

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This thesis investigated the use of carbon nanotubes as active components in solution processible organic semiconductor devices. We investigated the use of functionalized carbon nanotubes in carbon nanotubes network transistors (CNNFET) and in photoactive composites with conjugated polymers. For CNNFETs, the objective was to obtain detailed understanding of the dependence of transistor characteristics on nanotubes bundle sizes, device geometry and processing. Single walled carbon nanotubes were functionalized by grafting octadecylamine chains onto the tubes, which rendered them dispersible in organic solvents for solution processing. To investigate the dependence of electronic properties of carbon nanotubes networks on bundle size, we developed a centrifugal fractionation protocol that enabled us to obtain nanotube bundles of different diameters. The electronic properties of networks of nanotube bundles deposited from solution were investigated within a CNNFET device configuration. By comparing devices with different degree of bundling we elucidated the dependence of key device parameters (field effect mobility and on/off ratio) on bundle sizes. We further found that, in contrast to traditional inorganic transistors, the electronic properties of the CNNFETs were dominated by the channel rather than contact resistance. Specifically, the apparent mobility of our devices increased with decreasing channel length, suggesting that the charge transport properties of CNNFETs are bulk rather than contacts dominated. This meant that charge traps in the channel of the device had a significant effect on transport properties. We found that charge traps in the channel region introduced by adsorbed oxygen and silanol groups on the SiO2 surface were responsible for the dominant p-type conductance in as-fabricated devices. Based on this understanding, we demonstrated the p-type to n-type conversion of the transistor characteristics of CNNFETs by depositing nanotubes on electron-trapfree dielectric surfaces. Finally, by combining annealing and surface treatment, we fabricated CNNFETs with high n-type mobility of 6cm2/V.s. For polymer composites, the objective was to obtain detailed understanding of the interactions between carbon nanotubes and the conjugated polymer; a prerequisite for using these composites in organic electronic devices. We fabricated well dispersed nanotube/polymer composites by using functionalized carbon nanotubes and studied the effect of nanotubes addition on the photophysical properties of the technologically important conjugated polymer poly(3-hexylthiophene) (P3HT). Measurement of the photoluminescence efficiency of nanotubes/polymer composites showed that addition of 10wt% carbon nanotubes effectively quenched the polymer emission indicating close electronic interactions. This indicated that nanotubes/polymer composites have potential in organic photovoltaic or light-sensing devices. Further analysis of the steady-state photoluminescence spectra revealed that nanotube addition resulted in increased structural disorder in the polymer. The incorporation of structural disorder into the polymer with the addition of even a small amount of carbon nanotubes may be detrimental to charge transport. UV-vis adsorption studies revealed that one-dimensional templating of P3HT chains by nanotubes resulted in a red-shifted feature in the solutionstate optical adsorption spectra of P3HT. This suggested that presence of nanotube surface templates the polymer self-organisation to produce highly ordered coating of P3HT chains around the nanotube. In order to elucidate the nanoscale origin of this phenomenon, we performed detailed STM studies on individual nanotubes adsorbed with P3HT chains. Since carbon nanotubes can be considered as rolled up sheets of graphite, we also performed STM on P3HT chains assembly on graphite for comparison. For P3HT assembly on HOPG, we found that while 2D crystals were observed when P3HT was cast onto HOPG from dilute solution, a thicker and more disordered film resulted when cast from concentrated solutions and subsequent layers were more likely to align normal to an underlying monolayer of P3HT on the HOPG surface. STM studies of nanotube/polymer mixtures revealed that the P3HT chains are adsorbed on nanotubes surface in such a way that the thiophene and hexyl moieties of the polymer associated with the nanotube surface in identical manner to P3HT monolayer depositions on graphite. This resulted in the increased order as inferred from adsorption UV-Vis spectroscopy, where the polymer chains, which are otherwise prone to chain kinks and twists in solution, adopt a planar configuration when adsorbed onto the nanotube surface.

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32

Palser, Adam H. R. "Theoretical properties of carbon nanotubes." Thesis, University of Oxford, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.365716.

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33

Shi, Mingxing. "Mode transformation in carbon nanotubes." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500487.

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34

Andrews, Robert. "Carbon nanotubes : synthesis and functionalization." Thesis, University of Edinburgh, 2007. http://hdl.handle.net/1842/2395.

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This thesis focuses on two of the major challenges of carbon nanotube (CNT) research: understanding the growth mechanism of nanotubes by chemical vapour deposition (CVD) and the positioning of nanotubes on surfaces. The mechanism of growth of single–walled nanotubes (SWNTs) has been studied in two ways. Firstly, a novel iron nanoparticle catalyst for the production of single–walled nanotubes was developed. CVD conditions were established that produced high quality tubes. These optimised CVD conditions were then used as the basis of several comparative CVD experiments showing that the quality of nanotubes and the yield of carbon depended on the availability of carbon to react. The availability could be controlled by the varying concentration of methane in the gas phase or the residence time of the methane over the catalyst. Evidence is presented that the diameters of the tubes produced were affected by the availability of methane. A second mechanistic investigation was carried out to study the validity of the previously proposed ring addition mechanism for the growth of carbon nanotubes from camphor. In this mechanism, the formation of tubes is thought to occur through the addition of preformed carbon rings: so it would be expected that there would be a relationship between the molecular structure of the precursor and the resulting SWNTs. To explore this relationship, comparative CVDs were carried out to produce SWNTs with several different cyclic and acyclic compounds similar in structure to camphor. The vapour pressure and the chemical stability of the precursor were found to be important to the formation of nanotubes, while the compound’s structure was not related to the quality of tubes produced. The lack of a relationship between the structure of the precursor and the production of SWNTs suggests that preformed rings are not vital to the production of SWNTs. Differences in the growth of SWNT from benzene and methane were related to the stability of each compound. In particular, differences in the distributions of the diameters of the tubes formed from methane and benzene have been observed. These differences have been explained in terms of the relative kinetic stabilities of these molecules, and in terms of a competition between end–cap and sidewall growth. Positioning of nanotubes on surfaces has been explored using two approaches. In the first approach, commercially obtained SWNTs were functionalized by a sulfur plasma so that the products would form bonds with gold surfaces. The nanotubes were found to selectively deposit themselves onto gold surfaces from ethanolic dispersions of the functionalized samples. This selective deposition of the nanotubes allowed the production of prototype carbon nanotube field–effect transistors with higher device yields than were obtained with unfunctionalized tubes. In a second approach to positioning of carbon nanotubes, the growth of tubes on surfaces by CVD was explored. Iron nitrate and different magnesium compounds were dip–coated onto SiO2 surfaces so that MgO supported–Fe catalysts would be formed by calcination. SWNTs were grown on the surfaces by CVD. Surface area measurements of the equivalent powdered catalysts showed that a high surface area was vital to produce dense growth of high quality SWNTs. The morphology of the surface was also found to play a key role in the growth of the tubes. Patterned growth of carbon nanotubes was accomplished using soft lithography techniques to control the localization of catalyst deposition onto a surface. A long calcination step (10 h, 950 °C) before CVD, was found to improve the quality of nanotubes grown. Catalysts that had been calcined for 10 hours were also found to produce smaller diameter nanotubes than uncalcined samples. The formation of smaller diameter tubes was explained in terms of the formation of MgFe2O4 alloys, consistent with results reported previously in the literature. In addition, Raman spectroscopy of the calcined catalysts with 3% w/w loadings of Fe was used to confirm directly the presence of MgFe2O4.

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35

Sajjad, Muhammad Tariq. "Exciton dynamics in carbon nanotubes." Thesis, University of Surrey, 2012. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.576127.

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ABSTRACT The confinement of excited charges in carbon nanotubes has significant effect on their optical and electronic properties. The absorption of light generates strongly correlated electron-hole pairs (excitons) in carbon nanotubes. We present a study of the decay of these photogenerated excitons in solutions of semiconducting SWNTs using the degenerate pump probe technique. Under specific experimental conditions, the exciton-exciton reactions on carbon nanotubes were found to correspond to an ideal ID coalescence-diffusion system with distinct regions of reaction-limited and diffusion-limited behaviours. We provided the first experimental evidence for such a system of 'universal behaviour' at longer times which exhibits a power law decay whose exponent and amplitude are independent of the initial population - one of the key characteristics of this reaction-diffusion system. We also show for the first time that exciton-exciton interactions are long-range, and further that the transition between reaction-limited and diffusion-limited regimes is much more abrupt than is predicted by existing theories. A modified theory incorporating a finite reaction length provided an excellent fit to the experimental data for a reaction length of -7 nm. We determined the reaction rate constant of k; = (3.76 ± 0.04) nmfps and the diffusion coefficient of D = (8.1 ± 0.4) nm2/ps from fitting of the asymptotic regimes with rate equations. We also provided the first experimental evidence of sub-diffusive transport of excitons in quasi ID SWNTs through studies of exciton annihilation dynamics in HiPco and CoMoCat SWNTs, where we observed that excitons in HiPco SWNTS exhibit normal diffusive transport where decay follows a Clal power law with decay exponent (a :::::: 0.5), whereas excitons in CoMoCat SWNTs decay more slowly with decay exponent (a :::::: 0.3) as result of sub-diffusive transport. We correlate this slow decay to a higher defect concentration in CoMoCat SWNTs as compared to HiPco measured using Raman spectroscopy and X-ray photoelectron spectroscopy. The experimental results were also compared to results from a Monte Carlo simulation of ID diffusion in a fluctuating potential landscape which shows good agreement with experiment and underlines the necessity to consider spatial aspects (separation of defects and interaction range) in theoretical approaches to the dynamics. The study of excitonic decay in single walled carbon nanotubes is very important in terms of understanding of fundamental photophysics of ID system and their possible application in electronics and photonic devices especially in light emitting devices and non-linear optics. 2

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36

Haque, M. S. "Gas sensors using carbon nanotubes." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.603677.

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A novel approach has been adopted for in-situ growth of CNTs on CMOS Silicon on Insulator (SOI) devices. The growth and deposition of CNTs on SOI CMOS has been successfully implemented at high temperature (>700°C) using tungsten as an interconnect. A detailed study of the nanotubes growth dependence on a number of parameters has been carried out on fully processed SOI CMOS substrates. A novel growth process of depositing CNTs using the very low power CMOS microhotplate acting as the thermal source has also been carried out. One of the key advantages of this process is the confinement of high temperature to the heater region only during the CNT growth, thereby, keeping the electronic circuitry unaffected. The results of the growth were highly repeatable with no degradation of the CMOS devices. High quality multi walled CNTs were locally grown, self-aligned onto the pre-formed sensing metal interdigitated electrodes. A low temperature process (<450°C) for single walled and multi walled CNTs was also developed using a hot filament stage. This process is suitable for devices with aluminium interconnect and is CMOS compatible. The locally growth CNTs on the sensor devices were tested with NO₂ extensively and showed response at room temperature which was an improvement on the present gas sensing technologies. The sensor was found to offer reasonable sensitivity to 100 ppb of NO₂ and faster chemical response time at elevated temperatures (tens of seconds). The smart CNT micro-sensor also showed responses to ammonia, methanol and ethanol. The ultra-low power consumption of the hotplates on ultra-thin CMOS compatible membranes and the growth of CNTs on multi-chips at the same time, in parallel, show great potential for high volume manufacturability and is a potential way forward for the next generation nanostructured material sensors.

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37

Longhurst, Matthew James. "Fluid interactions with carbon nanotubes." Thesis, Imperial College London, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.486910.

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Using a purpose built molecular dynamics (MD) code. we simulate a range of infinite and finite length H-terminated carbon nanotubes in vacuo. We find that the radial breathing mode (RBM) of the finite nanotubes approaches that of the infinite nanotubes for nanotubes greater than 5 nm in length. We investigate the effect on the RBM frequency' of immersion in water and find that external wetting is responsible for an upshift in the RBM of around 4-10 wave numbers. and internal wetting approximately 2-6 wave numbers. The upshift is comprised of two components: increased hydrostatic pressure on the nanotube due to curvature effects. and the dynamic coupling of the RBM with a shell of adsorbed fluid: In contrast to much of the current literature, we find that the latter of the two effects . is dominant. The upshift can be modelled analytically by considering the adsorbed fluid as an infinitesimally thin shell which interacts with the nanotube via-a continuum Lennard-Jones potential. Using MD, the RBM of carbon nanotubes in fluids can be accurately reproduced by replacing the fluid molecules with a mean field harmonic shell potential. greatly reducing simulation times. The pressure dependence of shifts in the vibrational modes of individual carbon nanotubes is strongly affected by the nature of the pressure transmitting medium as a result of adsorption at the nanotube sUrfade. Using analytical methods, as well as MD, we observe an as yet unreported low frequency breathing mode for the adsorbed fluid at around 50 cm-1 , as well as diameterdependent upshifts in the RBM frequency with pressure, suggesting metallic nanotubes may wet more than semiconducting ones. Finally. we describe a methodology for the continuous pumping of fluid through carbon nanotubes. Fluid is imbibed from a reservoir at 300 K. heated. and subsequently ejected from the hot end. Very high pressures are developed in the smaller nanotubes due to strong capillary forces, suggesting thAir use as nanoscale reaction vessels. A theoretical framework is developed allowing us to predict pumping fluxes over a range of nanotube diameters and temperatures.

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38

Cullen, Sarah Louise. "Electron microscopy of carbon nanotubes." Thesis, University of Cambridge, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387605.

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39

Aitkaliyeva, Assel. "Irradiation Stability of Carbon Nanotubes." [College Station, Tex. : Texas A&M University, 2009. http://hdl.handle.net/1969.1/ETD-TAMU-2009-08-3251.

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40

Rushfeldt, Scott I. "Sensor applications of carbon nanotubes." Thesis, Massachusetts Institute of Technology, 2005. http://hdl.handle.net/1721.1/33619.

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Thesis (M. Eng.)--Massachusetts Institute of Technology, Dept. of Materials Science and Engineering, 2005.
Includes bibliographical references (leaves 47-49).
A search of published research on sensing mechanisms of carbon nanotubes was performed to identify applications in which carbon nanotubes might improve on current sensor technologies, in either offering improved performance, reduced cost of manufacture, or both. Using this overview of carbon nanotube-based sensors, specific sensor technologies that could benefit from the use of newly developed techniques for producing aligned and ordered bundles of carbon nanotubes were selected. Reports of chemical/gas, biological, optical, mechanical, and a few other sensor applications of carbon nanotubes are reviewed. Only a few of these applications might benefit from aligned and ordered bundles of carbon nanotubes. Of these potential applications, only applications in semiconducting gas sensors, DNA sensors, and infrared sensors appear to have clearly defined market niches and are sufficiently technologically mature to allow a detailed assessment of commercial potential. It is argued that DNA and infrared sensors have good commercial potential with a medium amount of risks, while gas sensors have a smaller potential. Finally, DNA sensors are believed to derive the most value from aligned and ordered bundles of carbon nanotubes.
by Scott I. Rushfeldt.
M.Eng.

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41

Scardaci, Vittorio. "Carbon nanotubes for photonic devices." Thesis, University of Cambridge, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612536.

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42

Oei, Shu-Pei. "Novel applications of carbon nanotubes." Thesis, University of Cambridge, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.611680.

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43

Miners, Scott A. "Chemical reactions inside carbon nanotubes." Thesis, University of Nottingham, 2016. http://eprints.nottingham.ac.uk/33062/.

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The work presented in this thesis describes the development and application of strategies to evaluate the influence of extreme confinement within narrow single-walled carbon nanotubes (SWNT) on the pathways of preparative chemical reactions. Methodologies to reduce carbon nanotube length were critically assessed in order to aid the access and egress of reactants and products to and from the SWNT internal channel during confined reactions. A reliable procedure for the encapsulation of organic molecules within carbon nanotubes was developed utilising a novel fractional distillation procedure which exploits the effect of nanoscale confinement on the phase behaviour of liquids. Confinement of the halogenation of N-phenylacetamide within SWNT demonstrated, for the first time, that narrow SWNT are effective hosts for chemical reactions on a preparative scale in the absence of metallic catalysts. The selective formation of the para-brominated regioisomer improved from 68 to 97% as a direct result of confinement. Furthermore, the confinement of a range of azide-alkyne 1,3-dipolar cycloaddition reactions within SWNT showed a consistent increase in selectivity for the 1,4-triazole (up to a 55% increase). The magnitude of this effect can be tuned by varying the SWNT diameter or the steric bulk of the reactant substituents. In addition to the dominant steric factors, the results herein suggest that the electronic properties of carbon nanotubes induce an additional, more subtle influence on selectivity. Investigating the autocatalytic Soai reaction in the presence of carbon nanotubes demonstrated, on a fundamental level, that the helicity of SWNT induces an effect on the formation of chiral molecules. Since carbon nanotubes exist as a racemic mixture of P and M enantiomers, their presence has a symmetrising effect whereby an enantioselective Soai reaction affording 90% ee becomes racemic upon the addition of (6,5)-SWNT. These results clearly demonstrate the ability of carbon nanotubes to influence the properties of preparative chemical reactions.

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44

Stoppiello, Craig Thomas. "Inorganic synthesis inside carbon nanotubes." Thesis, University of Nottingham, 2017. http://eprints.nottingham.ac.uk/41855/.

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The use of single-walled carbon nanotubes (SWNTs) as test tubes for the encapsulation of metallic nanoparticles (MNPs) and the formation of inorganic nanomaterials has been advanced. A methodology to encapsulate the group 10 and 11 metals inside SWNTs to investigate their properties has been optimised. Each metal interacts with carbon differently at the atomic level, as shown by aberration-corrected high resolution transmission electron microscopy (AC-HRTEM), leading to the promotion of a plethora of different processes stimulated by MNPs under the electron beam. Additionally, interactions between SWNTs and small clusters of the group 10 metals have been examined, revealing marked differences between metal-carbon bonding for each metal. This has allowed for a useful insight into metal-carbon interactions on the atomic level which could have profound implications on the future development of new catalysts or nanoscale devices. Following on from this, a series of chemical reactions with platinum compounds were carried out within SWNTs which have shown SWNTs to be both a very effective reaction vessel and template for the formation of low-dimensional PtX2 (X = I, S) nanocrystals, materials that are difficult to create by traditional synthetic methods. The stepwise synthesis within SWNTs has enabled the formation of the platinum compounds to be monitored at each reaction stage by AC-HRTEM, verifying the atomic structures of the products and intermediates, and also by an innovative combination of fluorescence-detected X-ray absorption spectroscopy (FD-XAS) and Raman spectroscopy, monitoring the oxidation states of the platinum guest compounds within the nanotube and the vibrational properties of the host SWNT respectively. The stepwise synthesis has appeared to offer only limited preparative potential because of the lack of stoichiometric control in the resultant inorganic nanomaterials. A new approach for nanoscale synthesis in nanotubes developed in this study utilises the versatile coordination chemistry of platinum which has enabled the insertion of the required chemical elements (e.g. metal, and halogens or chalcogens) into the nanoreactor in the correct proportions for the controlled formation of PtI¬2 and PtS2 with the exact stoichiometry and structure. FD-XAS has also been used to probe the transformations of Pt(acac)2@SWNT to Pt@SWNT, and Cu(acac)2@SWNT to Cu2Ox@SWNT (where x > 1). It was shown that the temperature of both transformations was significantly lower than required for the same reactions in the bulk, which demonstrates the ability of SWNTs to lower the activation energy by polarising encapsulated molecules. Finally, a variety of novel MNPs and MO¬x¬ (M = Pt, Pd, Ni) materials were encapsulated within hollow graphitised carbon nanofibres (GNFs) and evaluated for the sensing of glucose. MOx@GNFs were revealed to be more active sensors than their corresponding MNPs which can be attributed to the increase in Lewis acidity of the metal centres upon oxide formation. Furthermore, the effectiveness of each metal and their corresponding oxides for glucose detection was found to increase in the order Pt > Pd > Ni which can be attributed to both physical and chemical properties of the respective metals. Overall, this thesis demonstrates that nanotubes can be used effectively to not only investigate chemical transformations on the atomic level, but also act as nano-sized test tubes and templates for the formation of novel, low-dimensional inorganic materials with bespoke structure and composition.

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45

Zhang, Ru. "Spectroscopic Studies of Carbon Nanotubes." Ohio University / OhioLINK, 2008. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1196402233.

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46

Johnson, Aaron A. "Thermal Processing of Carbon Nanotubes." University of Cincinnati / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1399629659.

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47

Abdallah, Banu. "Carbon nanotubes in cancer therapy." Thesis, University of Central Lancashire, 2013. http://clok.uclan.ac.uk/9658/.

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Carbon Nanotubes (CNTs) are highly attractive vehicles for the delivery of bio-molecules into living systems specifically for applications in cancer therapy. Two main types of CNTs; single-walled (SWNT) and multi-walled (MWNT) have been investigated. Pristine CNTs are poorly soluble in aqueous solvents, and therefore need to be functionalized (f-CNT) to enhance their solubility and biocompatibility. The f-CNTs possess the ability to cross cell membranes and enter cells consequently having the potential as vehicles for drug delivery. Polyethylene glycol (PEG400) and Pluronic®F127 (PF127) functionalized SWNTs and MWNTs have been investigated in this study for in vitro cancer therapy. Both have demonstrated high tumour suppression efficacy with respect to an anti-cancer drug Paclitaxel, when utilised solely. However, f-CNTs for the delivery of anti-cancer agents for brain tumours, in particular the most common tumour Glioblastoma, have not been researched. The toxicity of these materials is another issue that requires further investigation. Cytotoxicity of CNTs is thought to be dependent on several characteristics such as length, purity and type of functionalization. The aim of this study was to characterize, functionalize and investigate in vitro cell cytotoxicity of f-CNTs with and without Paclitaxel (PTX). As dispersing and stabilization agents two polymeric systems were used; PEG400 and PF127. CNTs characteristics have been investigated by using various techniques and two stabilization and dispersing agents have been used for functionalization. Raman spectra have been recorded using two laser lines at 325 nm and 488 nm. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) were used to analyse their structure and morphology. All samples were functionalized, homogenised, centrifuged and their ζ-potentials were measured. CNTs were found to be in a size range of 100 nm to several microns long, with diameter values ranging from 07 ± 1.0 nm for SWNT and inner diameter I.D. 10-20 nm and 30-40 nm Outer Diameter values (O.D.) with 6-12 concentric walls for MWNT. Both SWNT and MWNT exhibited stability in both polymeric systems implemented even after a 10 day period. Particularly PEG400 based formulations showed superior performance in terms of greater ζ-potential values. Notable shifts in G-band were examined confirming the presence of f-CNTs. Higher entrapment efficiency was accomplished with f-CNTs reaching a maximum efficiency at 200 μg/ml. Cell lines SVGp12 and U87-MG were exploited for cytotoxicity evaluations. SWNT and MWNT demonstrated insignificant cytotoxic effects on SVGp12 (normal astrocytes) cell lines even at elevated concentrations of up to 15 mg/ml. Nevertheless, f-CNTs showed significant reduction in the cell viability at low Paclitaxel concentrations on U87-MG grade IV Glioblastoma. As a selection of CNTs have been investigated by various researchers, it is exceptionally challenging to conclusively state whether or not they are indeed toxic. This research into CNTs has successfully examined the effects of co-formulation with various components and the potential effects on drug delivery for cancer cells. Conceptually, CNTs are rightfully labelled as the king of nanomaterials due to their elusive chemical and physical properties; ensure that they are likely to receive much attention in the not too distant future.

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48

Motavas, Saloome. "Optical absorption in carbon nanotubes." Thesis, University of British Columbia, 2014. http://hdl.handle.net/2429/50121.

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Due to their unique optical properties, carbon nanotubes have been widely investigated for use in photonic and optoelectronic devices and optical absorption and emission with nanotubes have been achieved in experiments. On the other hand, the structural characteristics of nanotubes, e.g. the chirality, diameter, and length, as well as other factors such as the polarization of the incident light, presence of a magnetic field and mechanical deformation can significantly affect the optical properties of these structures. Some of these effects have been theoretically studied at the tight-binding approximation level. However, a systematic first-principles-based study of nanotubes that addresses these effects did not exist in the literature prior to the present work. This thesis aims at performing such a fundamental study. We first describe a method for calculating the dipole moments and transition rates in nanotubes. This also enables the study of selection rules, based on which a modified set of rules is defined. The probability of absorption is studied in the full range of infrared-visible-ultraviolet. We show that π-σ*, σ-π*, and σ-σ* transitions that are neglected in previous works are allowed and can lead to high probabilities of transition. We then investigate several effects caused by the curvature of the nanotube sidewall and their impacts on the optical properties. The overall effect is shown to not only depend on the diameter, but also on the chirality of the nanotube. Through the study of the light polarization effect, we show that the overall transition rate spectrum of the perpendicularly polarized light is suppressed for smaller-diameter nanotubes in the IR/VIS range. In the UV region, however, perpendicular polarization is generally absorbed at a higher rate compared to parallel polarization. Finally, we show how the absorption spectra of short nanotube segments can be different from those of long nanotubes. We examine the effect of length on individual absorption peaks and also investigate the effect of spin on the optical properties of nanotube segments. The calculation method described in this thesis and the results can be used to estimate the effects of structural and environmental factors on the optical absorption properties of nanotubes.
Applied Science, Faculty of
Electrical and Computer Engineering, Department of
Graduate

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49

Zhang, Qiuhong. "Carbon Nanotubes on Carbon Fibers: Synthesis, Structures and Properties." Dayton, Ohio : University of Dayton, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=dayton1272515887.

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Thesis (Ph.D. in Materials Engineering) -- University of Dayton.
Title from PDF t.p. (viewed 06/23/10). Advisor: Liming Dai. Includes bibliographical references (p. 136-162). Available online via the OhioLINK ETD Center.

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50

Gontijo, Régis Fernandes. "Aplicação de técnicas de planejamento experimental e de espectroscopia de absorção óptica ao estudo da dispersibilidade de nanotubos de carbno de parede única em solução aquosa de surfactantes." CNEN - Centro de Desenvolvimento da Tecnologia Nuclear, Belo Horizonte, 2011. http://www.bdtd.cdtn.br//tde_busca/arquivo.php?codArquivo=255.

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Nenhuma
Neste trabalho os nanotubos de carbono de parede única (SWNTs, do inglês single-walled carbon nanotubes) sintetizados pelo método HiPco foram dispersados em solução aquosa de três surfactantes aniônicos: colato de sódio (NaC), dodecilbenzenosulfonato de sódio (NaDDBS) e dodecilsulfato de sódio (SDS). Foi empregado um procedimento de dispersão que consiste de uma uma etapa inicial de desagregação ultrassônica, seguida de uma etapa de centrifugação, para remoção do material não desagregado. A concentração inicial de SWNTs foi fixada em 0,25 mg⋅mL−1. Todas as amostras foram preparadas em duplicatas. Quatro variáveis foram investigadas simultaneamente: a concentração de surfactante, o tempo de sonificação, a aceleração centrípeta e o tempo de centrifugação. Foram aplicadas técnicas de planejamento estatístico de experimentos para compreender a influência simultânea destes fatores e como eles interagem entre si. Como variável de resposta foi utilizada a área das absorções ressonantes na região de 500 a 1000 nm. As medidas de espectroscopia de absorção óptica foram realizadas em quatro datas diferentes para avaliar a degradação das amostras ao longo do tempo. A microscopia eletrônica de transmissão foi utilizada para avaliar a qualidade e o estado de agregação de algumas dispersões em função das condições experimentais. Foi desenvolvido um algoritmo computacional para automatizar o tratamento dos dados. No primeiro passo os dados são processados por um filtro de ruído espectral que calcula as médias sobre valores de absorção óptica consecutivos. No passo seguinte as absorções ressonantes dos SWNTs são obtidas após a correção da linha de base típica de materiais grafíticos. No passo final, são calculadas as áreas espectrais e identificadas as posições de máximo das linhas espectrais. Os resultados mostraram que nas condições experimentais estudadas, os fatores tempo de sonificação, aceleração centrípeta e tempo de centrifugação foram significativos. Como esperado, verificou-se que o tempo de sonificação contribui para aumentar a concentração final dos nanotubos dispersos e que o aumento da aceleração centrípeta e do tempo de centrifugação contribui para reduzir a concentração final. Verificou-se que todas as interações entre as variáveis consideradas no planejamento experimental (AB+CD, AC+BD e AD+BC) influenciam na absorção óptica das dispersões, apesar de terem menor influência que os efeitos principais B, C e D. Através de um modelo de ajuste para as áreas totais, foi estimada a absorção óptica média na faixa de 500 a 1000 nm, em excelente concordância com os valores médios obtidos experimentalmente. Em relação à microscopia eletrônica de transmissão (MET), esta revelou a presença de feixes de nanotubos em todas as dispersões analisadas. Todavia, devido às limitações da técnica, não foi possível afirmar se esta estrutura agregada existe em solução ou foi formada durante a preparação da grade de microscopia. A análise por MET também revelou uma característica importante da amostra utilizada. Observou-se que estes nanotubos encontram-se altamente decorados com nanopartículas esféricas de ferro, cujos diâmetros são da ordem de 5 nm e que foram encontradas mesmo após condições rigorosas de centrifugação (120.000 g por 120 min). Isso evidencia a existência de uma forte interação entre as nanopartículas de Fe e os SWNTs nesta amostra.
In this work, HiPco single-walled carbon nanotubes (SWNTs) were dispersed in aqueous solutions of three anionic surfactants: Sodium cholate (NaC), sodium dodecylbenzenesulfonate (NaDDBS) and sodium dodecyl sulfate (SDS). The dispersion procedure employed consisted of an initial ultrasonic disaggregation step, followed by a centrifugation step for the removal of the non disaggregated material. The initial concentration of SWNTs was set at 0.25 mg⋅mL−1. All samples were prepared in duplicate. Four variables were investigated simultaneously: the surfactant concentration, the sonication time, the centripetal acceleration, and the centrifugation time. Experimental design techniques were employed to evaluate the simultaneous influence and interaction of the factors. The response variable used was the area of the resonant absorptions ranging from 500 nm to 1,000 nm. Optical absorption measurements were performed at four different dates to evaluate the degradation of the samples over time. Transmission electron microscopy was used to evaluate the quality and the state of aggregation of some dispersions as a function of the experimental conditions. A computer algorithm was developed for the automatic data processing. In the first step the data were processed with a spectral noise filter that calculated the average of consecutive absorption values. In the next step, with the help of a hyperbolic baseline, the resonant absorptions of the SWNTs were obtained after correction of the typical baseline of graphitic materials. In the last step, the area above the baseline, or the specific area - AE, the total area - AT , and the ratio of the two (the percent area) Apct were calculated. The algorithm also allowed the identification of maximum absorption peak positions. The results shows that in the experimental conditions investigated, the factors sonication time, centripetal acceleration, and centrifugation time were significant. As expected, it was observed that the sonication time contributes to increase the final concentration of the dispersed nanotubes and that the increase in the centripetal acceleration and in the centrifugation time contributes to reduce the final concentration. However, its contribution was insignificant for NaC and little important for NaDDBS. All the interactions considered in the experimental design (AB+CD, AC+BD, and AD+BC) influenced the optical absorption of the nanotube dispersions, despite their smaller influence in relation to the main effects B, C, and D. The average optical absorption in the range from 500 nm to 1,000 nm was estimated using a fitting model for the total areas, giving excellent agreement with the average values obtained from the experimental data. Transmission electron microscopy (TEM) analysis revealed the presence of nanotube bundles in the dispersions analyzed. However, due to technical limitations, it is not possible to state whether this aggregate structure existed in solution or whether it was formed during the preparation of microscopy grids. The TEM analysis also revealed an important characteristic of the samples studied. These HiPco SWNTs are highly decorated with spherical iron nanoparticles with diameter in the order of 5 nm, which were also observed even after rigorous ultracentrifugation (120,000g for 120 min), making it clear that there is a strong interaction between Fe nanoparticles and SWNTs in this sample.

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