In this thesis, synthesis, characterization and electrical transport of Carbon nanotubes (CNTs) have been discussed. The first chapter contains a brief introduction of various forms of carbon including CNT. The CNTs are currently the materials of intense research interest due to their remarkable mechanical and electrical properties. CNTs can be visualized as a graphene sheet that has been rolled into a seamless tube. CNTs are either single-walled carbon nanotubes (SWCNT) or multi-walled carbon nanotubes (MWCNT). SWCNT is a tube with only one wall and MWCNT has many coaxial tubes and weak Van der Waal forces hold them together. The properties depend on chirality, diameter and length of the tubes. Chirality is defined by the symmetry and the chiral angle formed between the carbon bonds. The atomic structure of CNTs is described in terms of the tube chirality, which is defined by the chiral vector Ch and the chiral angle . The chiral vector is Ch = na1 + ma2, where the integers (n, m) are the number of steps along the zig-zag carbon. Depending on the tube chirality the electrical properties of the CNTs differ; they can be metallic or semiconducting. When n-m = 3p, where p is an integer, the CNTs are metallic and when n-m  3p, the CNTs are semiconducting. Due to the high anisotropy and high aspect ratio, CNTs have many potential applications with great technological importance such as functionalized molecules, conductive wires, bearings of rotational motors, field emitters, hydrogen storage, sensors, polymer composites, nanotube yarn and nanotube filters, X-ray generator, electron sources for microscopy and lithography, gas discharge tubes and vacuum microwave amplifiers, etc. The first chapter gives a brief introduction about various forms of carbon and their properties, particularly of CNTs. The nature of the CNTs depends on the method of production, which controls the degree of graphitization, the tube diameter and the chirality. Most synthesis methods originate from the idea of obtaining adequately active carbon atomic species or clusters from carbon sources and assembling them into CNTs without or with catalysts. The commonly used methods for the synthesis of carbon nanotubes are arc-discharge, Laser ablation, high-pressure catalytic decomposition of carbon monoxide (HiPCO), electrophoretic deposition (EPD), flame synthesis, pyrolysis, chemical vapour deposition (CVD), hot-filament CVD, plasma enhanced chemical vapour deposition (PECVD) using DC, RF, and micro wave power sources, hot-filament dc (HF-dc PECVD), inductively coupled plasma (ICPECVD) and electron cyclotron resonance (ECR PECVD). Although many efforts have been made to develop various synthesis methods, most of them require many steps. Moreover, the complicated and rigorous control of parameters and expensive materials are unavoidable that has put limitation in reproducing the same in large scale. In this chapter, a simple method for the synthesis of CNTs on a large scale that eliminates nearly the entire complex and expensive machinery associated with widely used growth techniques has been discussed. In Chapter 2, the synthesis and characterization of entangled CNTs are discussed. It is shown that entangled CNTs can be synthesized in one step by using double stage furnace. Tetrahydrofuran as carbon source material and nickelocene as catalyst source material have been used to synthesize CNTs. With this method CNTs can be synthesized at a temperature as low as at 600 0C. In this technique the self-developed pressure carries the vapours to the hot zone of the furnace. This has led to think in modifying the double stage furnace. A single stage furnace having temperature gradient is made to synthesize CNTs. The vapours are carried from low temperature zone to hot zone where the carbon species and catalysts react to form CNTs. The advantage of this furnace is that it is one-step process. Using another carbon source material such as Diethyl Ether and nickelocene as catalyst source material CNTs are synthesized. The as synthesized and purified CNTs are characterized by X-ray diffraction (XRD), Scanning electron microscope (SEM), transmission electron microscope (TEM), high resolution TEM (HRTEM) and Raman spectroscopy. The CNTs are multi-walled in nature as observed by HRTEM. In Chapter 3, the synthesis of aligned CNTs is discussed by using benzene as carbon source and ferrocene as catalyst source materials. Aligned MWCNTs were synthesized in the temperature range between 650 - 1100 0C in a single stage furnace without the need for carrier gas nor predeposited metal catalyst substrate. The essential need of CNTs are (1) to obtain aligned nanotubes with millimeter lengths to enable the formation of novel nanotube-polymer composites that incorporate continuous nanotubes throughout their thickness for highly anisotropic thermal and electrical conductivities; and (2) to provide samples for detailed physical characterization - tensile strength, thermal, electrical conductivity, field emission etc. SEM observation reveals the increase in length of nanotubes from 85 m to 1.4 mm with the increase of preparation temperature. The diameter as investigated by high-resolution transmission electron microscopy (HRTEM) remains almost constant 70-80 nm (75-85 layers). Once nanotube formation is established, the growth continues in the same direction and may well be reinforced by the presence of surrounding CNTs i.e. almost every particle produces a nanotube and bundling of neighboring tubes lead to collective vertical growth. The increase in length is due to the enhanced diffusion of active carbon with increasing preparation temperatures. The alignment of CNTs is also observed to the lateral side of the substrate. In Chapter 4, the synthesis and characterization of carbon nanoribbon and singled crystal iron filled CNTs is discussed. Particularly interesting are those CNTs filled with magnetic nanowires, which can provide an effective barrier against oxidation and consequently ensure a long-term stability in the core. The filling of metals within carbon nanotubes has extended the potential application base of these materials to quantum memory elements, high density magnetic storage media, semiconducting devices, field electron emitters, high resolution magnetic atomic force microscopy tips, magnetic field sensors and scanning probe microscopes etc. Tetrahydrofuran as carbon source material and ferrocene as catalyst materials has been used to synthesize mixture of carbon nanoribbons and iron filled CNTs. The techniques used to characterize the materials are XRD, SEM, HRTEM and superconducting quantum interference device (SQUID). The powder XRD pattern shows that the bcc -Fe phase of iron is present. HRTEM studies reveal the presence of multi-walled carbon nanotubes and well-crystallized -Fe phase filled inside the core region. Closer inspection of the HRTEM images indicated that the bcc structure -Fe nanowires are monocrystalline and Fe (110) plane is indeed perpendicular to the G (002) plane. Large coercivity (i.e. 1037 Oe at 300 K and 2023 Oe at 10 K) in the iron filled CNTs and carbon nanoribbons have been observed. The high coercivity is mainly attributed to the following two factors. Firstly, it is known that due to the uniaxial magnetic anisotropy of the nano size iron in the core region of the carbon nanotubes. Secondly, ferromagnetic behavior exhibited by the localized states at the edges of the carbon nanoribbons. The anisotropic electrical transport property of MWCNTs has been discussed in the chapter 5. The activated diffusive nature of transport along axial direction of CNT is explained. The transport perpendicular to the tube direction is explained in terms of a hopping mechanism. The anisotropic resistivity (N/P) value obtained is 3. The temperature dependent magnetoresistance (MR) is studied in magnetic fields up to 11 Tesla at low temperatures both in the parallel and perpendicular direction of an aligned MWCNT mat. In both cases a negative MR is observed. Chapter 6 discusses the preparation of CNT-polymer composites. The temperature dependence of the conductivity and magnetoresistance (MR) has been studied making four-point contact method on the carbon nanotubes polymer composites as result of increasing CNT content. The conductivity increases with increasing carbon nanotube weight percentage. The increase in conductivity as a function of the CNT weight percent is attributed to the introduction of conducting CNT paths in the polymer matrix. With the increasing CNT content the number of interconnections present in a random system is found to vary. Electrical conduction in nanotube mat or nanotube composites is explained by a variable range hopping (VRH) conduction mechanism. The negative magnetoresistance has been observed for the polymer composites. It is consistent with the report on CNTs bundles and polymer composites. Finally a brief summary of the work presented in this dissertation is discussed along with future directions in this research.

Sensores de filme de carbono, construídos a partir de resistores com 2 Ω de resistência nominal, foram utilizados para aplicações em áreas de interesse ambiental e farmacêutico sem a modificação prévia de suas superfícies. Através de um tratamento eletroquímico em meio ácido, é possível obter uma faixa de potencial (para ambos os limites anódico e catódico) maior comparado aos eletrodos de carbono convencionalmente utilizados. Devido ao fato dos sensores serem confeccionados em escala industrial na Alemanha, seu custo é muito baixo, tornando possível sua utilização na forma de eletrodos descartáveis. Além disso, são caracterizados por uma grande versatilidade, reprodutibilidade e estabilidade. Para comprovar a viabilidade dos eletrodos de filme de carbono como transdutores voltamétricos, amostras de paraquat foram analisadas em águas de rio e potável. A associação com a voltametria de onda quadrada possibilitou obter um limite de detecção inferior ao limite máximo estabelecido para o herbicida em água potável. Estudos por voltametria cíclica mostraram dois picos para a redução do paraquat, similares aos descritos na literatura. Os sensores de filme de carbono também foram adaptados ao sistema de análise por injeção em fluxo para a determinação amperométrica de paracetamol e de ambroxol em formulações farmacêuticas. Em ambos os estudos, foi possível obter ampla faixa linear de concentração, baixos limites de detecção e sensibilidade elevada. Estudos de repetibilidade com os dois analitos apresentaram desvios padrões relativos de até 3%, comprovando a ausência de efeito de memória. Os resultados obtidos durante as análises em fluxo com os novos sensores amperométricos concordaram com as metodologias descritas nas farmacopéias. Ao longo dos quatro anos de doutoramento também foram desenvolvidos outros estudos, os quais estão descritos nos apêndices desta tese. / Carbon film sensors, built from resistors of 2 Ω nominal resistance, were employed for application in the environment and pharmaceutical fields without previous modification of the electrode surface. When these sensors are electrochemically treated they obtain a wider potential window (both anodic and cathodic regions) than many other forms of carbon. Due to the fact that sensors are produced on industrial scale in Germany, the cost of each unit is very low, a feature that enables the use of these electrodes in disposable form. Moreover, they have great versatibility, reproducibility and stability. To prove the suitability of the carbon film electrodes as voltammetric sensors paraquat samples were analysed in river and drinking water. The association with the square wave voltammetry led to a detection limit below the allowed upper limit for herbicide analysis in drinking water. Previous results with cyclic voltammetry showed two peaks for paraquat reduction, in agreement with the literature data. The carbon film sensors were also adapted to the flow injection analysis system for amperometric determination of acetaminophen and ambroxol in pharmaceutical formulations. It was possible to obtain a wide linear working range, low detection limit and high sensitivity for both analytes. During the repeatabilty studies, acetaminophen and ambroxol showed relative standard desviations lower than 3% without any memory effect. The results obtained with a new amperometric sensor associated to FIA were in good agreement with those recommended by pharmacopoeias. In the appendices of this thesis are described other studies which have been developed for four years of PhD.

Orientador: Cecilia A. C. Zavaglia / Tese (doutorado) - Universidade Estadual de Campinas, Faculdade de Engenharia Mecanica / Made available in DSpace on 2018-08-07T02:27:14Z (GMT). No. of bitstreams: 1 Uzumaki_EmiliaTieko_D.pdf: 44142340 bytes, checksum: e8db433907d2fd2f88b260ed4cd8a791 (MD5) Previous issue date: 2006 / Resumo: O carbono tipo diamante ("diamond-like carbon" - DLC) tem demonstrado características, como alta dureza, baixo atrito, resistência ao desgaste e à corrosão, e biocompatibilidade, que podem melhorar as propriedades de implantes sólidos e articulados. O processo de imersão em plasma vem sendo usado para depositar DLC em substratos tridimensionais, pois, com esta técnica, se consegue melhor adesão do que com as técnicas convencionais. Neste trabalho, filmes de DLC foram depositados, pelo processo de imersão em plasma, em lamínulas de vidro, silício e liga de titânio Ti-13Nb-13Zr. A caracterização da microestrutura, morfologia, dureza e adesão dos filmes de DLC foi feita por espectroscopia Raman, microscopia eletrônica de varredura (MEV), microscopia de força atômica (MFA), nanoindentação e ensaio de puxamento. Como exemplos de peças tridimensionais, filmes de DLC foram depositados em implantes osteoarticulares de quadril e joelho, titânio poroso (esponja de célula-aberta, semelhante à estrutura do osso esponjoso, expandida a vácuo), facas industriais, bisturi cirúrgico, engrenagem de motor, tubos de quartzo e de alumínio, e outros objetos. O filme obtido apresentou boas propriedades mecânicas, aumentando em 2 vezes a dureza da liga de Ti, alta adesão (filme sem interface definida e sem delaminação), resistência ao desgaste, baixa rugosidade e uniformidade de deposição em superfícies tridimensionais. Os resultados de corrosão (polarização de Tafel e espectroscopia de impedância eletroquímica em fluido corporal simulado) mostraram que o revestimento de DLC melhora a resistência da liga de Ti à corrosão. No ensaio de biocompatibilidade in vitro, com células fibroblásticas, foram estudados a citotoxicidade, adesão e morfologia celular (estudo citoquímico, microscopia de contraste de fase, MEV e MFA). No ensaio de biocompatibilidade in vivo, a liga de Ti-13Nb-13Zr, revestida com DLC, foi investigada em tecido muscular e ósseo de ratos após 4 e 12 semanas do procedimento cirúrgico. A interface formada entre o DLC e o tecido foi investigada por histologia convencional, e os implantes retirados por MEV. A interface entre o implante e o tecido ósseo, não descalcificado, foi estudada por MEV na modalidade retroespalhamento. Os resultados mostraram a biocompatibilidade in vitro e in vivo do filme de DLC, e foi verificado também que os implantes revestidos com DLC possuem resposta biológica mais favorável do que os implantes não revestidos / Abstract: Diamond-like carbon (DLC) films are often considered a suitable coating material for orthopaedic applications. It has proven characteristics, such as hardness, wear resistance, low friction coefficient and biocompatibility that improve the properties of solid and articulated implants. Recently, the plasma immersion process was used to deposit DLC films with superior adhesion properties to those prepared with conventional techniques. DLC coatings were deposited on glass coverslips, silicon (Si) and Ti-13Nb-13Zr substrates using the plasma immersion process. The microstructure, morphology, roughness, hardness and adhesion of DLC films were characterized using Raman spectroscopy, scanning electron microscopy (SEM), atomic force microscopy (AFM), nanoindentation and pull-test. As examples, DLC films produced by plasma immersion were deposited on industrial knives, surgical knives, knee implants, femoral heads (of hip prostheses), titanium foams, transmission gears of motorcycles, aluminium pipes, quartz pipes, and others objects. The corrosion susceptibility of DLC coatings produced by plasma immersion was studied in a simulated body fluid environment (Hanks' solution) using polarization test and electrochemical impedance spectroscopy (EIS). Electrochemical results showed that DLC coating produced by plasma immersion could improve corrosion resistance, and no significant damage has been observed. Vero cells (fibroblasts) were utilized for the in vitro biocompatibility studies, by cytotoxicity, adhesion and cell morphology (phase contrast microscopy, SEM, AFM, and cytochemical study). DLC-coated Ti-13Nb-13Zr was investigated in an animal model using the muscular tissue and femoral condyles of rats for intervals of 4 and 12 weeks postoperatively. The interface between the implants and tissue were analysed by light microscopy, and the removed implants by SEM. The SEM by backscattering was used to access the interface between the implants the bone tissue without decalcifying. Our results indicate that DLC coatings are biocompatible in vitro and in vivo / Doutorado / Materiais e Processos de Fabricação / Doutor em Engenharia Mecânica

Sensores de filme de carbono, construídos a partir de resistores com 2 Ω de resistência nominal, foram utilizados para aplicações em áreas de interesse ambiental e farmacêutico sem a modificação prévia de suas superfícies. Através de um tratamento eletroquímico em meio ácido, é possível obter uma faixa de potencial (para ambos os limites anódico e catódico) maior comparado aos eletrodos de carbono convencionalmente utilizados. Devido ao fato dos sensores serem confeccionados em escala industrial na Alemanha, seu custo é muito baixo, tornando possível sua utilização na forma de eletrodos descartáveis. Além disso, são caracterizados por uma grande versatilidade, reprodutibilidade e estabilidade. Para comprovar a viabilidade dos eletrodos de filme de carbono como transdutores voltamétricos, amostras de paraquat foram analisadas em águas de rio e potável. A associação com a voltametria de onda quadrada possibilitou obter um limite de detecção inferior ao limite máximo estabelecido para o herbicida em água potável. Estudos por voltametria cíclica mostraram dois picos para a redução do paraquat, similares aos descritos na literatura. Os sensores de filme de carbono também foram adaptados ao sistema de análise por injeção em fluxo para a determinação amperométrica de paracetamol e de ambroxol em formulações farmacêuticas. Em ambos os estudos, foi possível obter ampla faixa linear de concentração, baixos limites de detecção e sensibilidade elevada. Estudos de repetibilidade com os dois analitos apresentaram desvios padrões relativos de até 3%, comprovando a ausência de efeito de memória. Os resultados obtidos durante as análises em fluxo com os novos sensores amperométricos concordaram com as metodologias descritas nas farmacopéias. Ao longo dos quatro anos de doutoramento também foram desenvolvidos outros estudos, os quais estão descritos nos apêndices desta tese. / Carbon film sensors, built from resistors of 2 Ω nominal resistance, were employed for application in the environment and pharmaceutical fields without previous modification of the electrode surface. When these sensors are electrochemically treated they obtain a wider potential window (both anodic and cathodic regions) than many other forms of carbon. Due to the fact that sensors are produced on industrial scale in Germany, the cost of each unit is very low, a feature that enables the use of these electrodes in disposable form. Moreover, they have great versatibility, reproducibility and stability. To prove the suitability of the carbon film electrodes as voltammetric sensors paraquat samples were analysed in river and drinking water. The association with the square wave voltammetry led to a detection limit below the allowed upper limit for herbicide analysis in drinking water. Previous results with cyclic voltammetry showed two peaks for paraquat reduction, in agreement with the literature data. The carbon film sensors were also adapted to the flow injection analysis system for amperometric determination of acetaminophen and ambroxol in pharmaceutical formulations. It was possible to obtain a wide linear working range, low detection limit and high sensitivity for both analytes. During the repeatabilty studies, acetaminophen and ambroxol showed relative standard desviations lower than 3% without any memory effect. The results obtained with a new amperometric sensor associated to FIA were in good agreement with those recommended by pharmacopoeias. In the appendices of this thesis are described other studies which have been developed for four years of PhD.

Nous avons utilisé la méthode de CEMOVIS (Cryo-Electron Microscopy Of Vitreous Sections) pour étudier l’ultrastructure des cellules HT29 (lignée cancéreuse colique humaine) et plus particulièrement l’organisation de la chromatine au sein du noyau. Pour améliorer la méthode, nous avons développé un micromanipulateur qui facilite la collecte des coupes et leur transfert sur la grille. Nous avons également cherché à préparer de nouveaux films métalliques (en remplacement du carbone) permettant une meilleure adhésion des coupes sur le support Au vu des premiers tests réalisés, les films de TiO2 que nous avons fabriqués au laboratoire et caractérisés par microscopie électronique (HR, spectroscopie et cartographie EELS) semblent offrir des perspectives intéressantes que nous attribuons à leur propriétés de conducteur électrique à basse température (ce qui reste à démontrer). Les organites cellulaires (noyaux, réseaux de filaments du cytosquelette, systèmes multilamellaires) ont été identifiés in situ. Les conditions d’imagerie choisies nous ont permis d’obtenir une résolution permettant d’identifier les deux feuillets des bicouches membranaires. Dans le noyau, nous avons observé des motifs striés, distants de 2.7 à 3.5 nm que nous attribuons à la molécule d’ADN enroulée autour du cœur d’histones. Comparées aux images de phases denses de nucléosomes, ces images suggèrent que les nucléosomes (jamais identifiés in situ jusqu’à présent) présentent un ordre très local au sein de la chromatine, que nous discutons à la lumières des modèles polymériques actuels. / The ultrastructure of HT29 cells (human epithelial adenocarcinoma cell line) was studied by CEMOVIS (Cryo-Electron Microscopy of Vitreous Sections) with a special emphasis on chromatin organization in the cell nucleus. We proposed methodological improvements for this technique:- We first developed a grid holding micromanipulator to facilitate both cryosections collect and deposition on carbon-coated TEM grids.- We also developed new metallic thin films (to replace carbon-base supports) to enhance the adhesion of cryosections on their support. The TiO2 thin films that we produced and analysed by electron microscopy (high resolution imaging, EELS and chemical mapping) seem to be an interesting alternative to carbon films for the deposition of cryosections. Their adhesive properties could be due to Titanium high electric conductance at low temperature (although this relation has not been clearly demonstrated yet).In HT 29 cells, we indentified cell organites (nucleus; cytoskeleton filament bundles, multilamellar bodies) in situ. Selected imaging conditions provide for a high enough resolution to visualise the two membrane leaflets. In the cell nucleus, we observed striated patterns separated from 2.7 to 3.5 nm that we assume to be DNA molecule turns wrapped around the histone protein core. Compared with the dense phases formed in vitro by nucleosome core particle in solution, our images suggest that nucleosomes are locally ordered in chromatin. This observation is discussed regarding the chromatin polymeric models.