Conductive polymers are promising pseudo capacitive materials as they feature both good conductivity and high capacitance. Formation of composite between conductive polymers and carbon nanotubes is a proven technique in enhancing the material electroactivity. In-situ polymerization of conductive polymers includes polyaniline, polypyrrole and PEDOT: PSS and composite with MWCNT has been successfully achieved. Composites fabricated by using different dopants and their performance were studied. Excellent achieved capacitive performance is due to the combination of pseudo capacitance and double layer capacitance. The MWCNTs content has significant influence on the morphology and structure of the polymerized ECP in the composite. And therefore affects the material conductivity and the charge storage performance. Two electrodes cell performance shows that Ppy/MWCNT composite shows a more promising performance as electrode materials for EC applications in contrast to PANI/MWCNT and PEDOT: PSS/MWCNT composites.

Conductive polymers are promising pseudo capacitive materials as they feature both good conductivity and high capacitance. Formation of composite between conductive polymers and carbon nanotubes is a proven technique in enhancing the material electroactivity. In-situ polymerization of conductive polymers includes polyaniline, polypyrrole and PEDOT: PSS and composite with MWCNT has been successfully achieved. Composites fabricated by using different dopants and their performance were studied. Excellent achieved capacitive performance is due to the combination of pseudo capacitance and double layer capacitance. The MWCNTs content has significant influence on the morphology and structure of the polymerized ECP in the composite. And therefore affects the material conductivity and the charge storage performance. Two electrodes cell performance shows that Ppy/MWCNT composite shows a more promising performance as electrode materials for EC applications in contrast to PANI/MWCNT and PEDOT: PSS/MWCNT composites.

Electroactive polymers (EAP) are an emerging branch of smart materials that possess the capability to change shape in the presence of an electric field. Opportunities for the advancement of knowledge were identified in the branch of EAP consisting of inherently electrically conductive polymers. This dissertation explores methods by which the unique properties of composite materials having conductive polymers as a constituent may be exploited. Chapter 3 describes the blending of polyaniline with conventional thermoplastics. Processing these polyblends into foams yielded a porous conductive material. The effect of blend composition and processing parameters on the resulting porous morphology and electrical conductivity was investigated. These findings represent the first systematic study of porous conductive polymer blends. In Chapter 4, multilayer electroactive polymer actuators consisting of polypyrrole films electropolymerized on a passive polymer membrane core were harnessed as actuators. The membrane is vital in the transport of ionic species and largely dictates the stiffness of the layered configuration. The impact of the mechanical properties of the membrane on the actuation response of polypyrrole-based trilayer bending actuators was investigated. Candidate materials with distinct morphologies were identified and their mechanical properties were evaluated. These results indicated that polyvinylidene difluoride membranes were superior to the other candidates. An electrochemical synthesis procedure was proposed, and the design of a novel polymerization vessel was reported. These facilities were utilized to prepare actuators under a variety of synthesis conditions to investigate the impact of conductive polymer morphology on the electromechanical response. Characterization techniques were implemented to quantitatively assess physical and electrochemical properties of the layered composite. Chapter 5 proposes a new unified multiphysics model that captures the electroactive actuation response inherent to conductive polymer trilayer actuators. The main contribution of this investigation was the proposal and development of a new hybrid model that unifies concepts from charge transport and electrochemomechanical models. The output of the proposed model was compared with published data and shown to be accurate to within 10%. Finally, Chapter 6 demonstrated the application of these materials for use as precision mirror positioners in adaptive optical systems.

Alternative plasmonic materials of Transparent Nitrides and Conductive Oxides (TNCOs) including Indium Tin Oxide (ITO), Al-doped ZnO (AZO) and Titanium Nitride (TiN), have been proposed as novel material platforms for Si-compatible plasmonics and metamaterials, showing enhanced light-matter interaction over a broad spectral range. It has been recently shown that these materials feature reduced optical losses compared with conventional noble metals such as Au and Ag in the visible and near-infrared spectral range. However, it is still an open challenge to tailor the structural and optical properties of these materials, and to further reduce their optical losses, in order to effectively utilize them in photonic devices. In this thesis work, I demonstrate wide tunability of the optical and structural properties of ITO, AZO and TiN thin films, by using post-deposition annealing treatments, enabling significant reduction of their optical losses. By measuring the optical bandgaps of the investigated materials, I show that the tunability of the optical properties originates from the modulation of the free carrier concentration induced by the annealing treatment. Moreover, I perform XRD characterization of the fabricated films, indicating that the annealing also effectively tunes the grain size, which is consistent with the change of the optical properties. Eventually, I investigate the role of the annealing gases for ITO and AZO, demonstrating that free-carrier modulation in ITO and AZO is due to the change in the density of oxygen vacancies after post-deposition annealing. In particular, TNCOs possess epsilon-near-zero (ENZ) condition in near-infrared range with optical loss ε^"<1, thus providing enhanced internal fields in the medium at the ENZ condition. In collaboration with Prof. Nader Engheta and the previous post-doc in our group Dr. Antonio Capretti, we demonstrate enhanced second-harmonic generation (SHG) and third-harmonic generation (THG) from ITO thin films driven by ENZ condition. It results that the SHG generation efficiency is comparable with that of a crystalline quartz plate of thickness 0.5 mm, and that the THG generation efficiency is ∼600 times larger than crystalline silicon. As an application for the fabricated TiN material, I investigate PL intensity and lifetime in Hyperbolic Metamaterials (HMMs) coupled with emitting Si Quantum Dots (QDs). In collaboration with Hiroshi Sugimoto in Prof. Minoru Fujii’s group and the previous post-doc in our group Dr. Sandeep Inampudi, we demonstrate up to 1.6-times enhanced decay rate of QDs emission. Photonic devices based on TNCO plasmonic materials offer an effective approach for the engineering of novel Si-based photonic devices with enhanced light-matter coupling over a broad spectral range. As an application for the fabricated ITO, in collaboration with Hongwei Zhao in Prof. Jonathan Klamkin’s group, electro-absorption modulators are numerically investigated to show high extinction ration of greater than 6dB, while insertion loss is less than 1.3dB for wavelength range from 1.25 µm to 1.42 µm. Additionally, we demonstrate tunable optical properties of ITO thin films in mid-infrared spectrum by thermal annealing of ITO in oxygen environment. In collaboration with Sajan Shrestha and Adam Overvig in Prof. NanFang Yu’s group, we fabricate 2D periodic arrays of ITO and show wide tuning of plasmonic resonances of ITO nanostructure from 4 µm to 10 µm. Combining with the tunability of ITO thin films in near-infrared, the ITO material platform provides a promising method for the control and engineering of Si-based tunable plasmonic and metamaterial devices in the infrared spectrum. Finally, in collaboration with my colleague Ren Wang, we experimentally demonstrate silicon nanodisk arrays with tunable anapole mode excitation in the visible spectrum. The proposed high index nanostructures can be used to enhance absorption rate for applications in semiconductor photodetector.

abstract: In today's world there is a great need for sensing methods as tools to provide critical information to solve today's problems in security applications. Real time detection of trace chemicals, such as explosives, in a complex environment containing various interferents using a portable device that can be reliably deployed in a field has been a difficult challenge. A hybrid nanosensor based on the electrochemical reduction of trinitrotoluene (TNT) and the interaction of the reduction products with conducting polymer nanojunctions in an ionic liquid was fabricated. The sensor simultaneously measures the electrochemical current from the reduction of TNT and the conductance change of the polymer nanojunction caused from the reduction product. The hybrid detection mechanism, together with the unique selective preconcentration capability of the ionic liquid, provides a selective, fast, and sensitive detection of TNT. The sensor, in its current form, is capable of detecting parts per trillion level TNT in the presence of various interferents within a few minutes. A novel hybrid electrochemical-colorimetric (EC-C) sensing platform was also designed and fabricated to meet these challenges. The hybrid sensor is based on electrochemical reactions of trace explosives, colorimetric detection of the reaction products, and unique properties of the explosives in an ionic liquid (IL). This approach affords not only increased sensitivity but also selectivity as evident from the demonstrated null rate of false positives and low detection limits. Using an inexpensive webcam a detection limit of part per billion in volume (ppbV) has been achieved and demonstrated selective detection of explosives in the presence of common interferences (perfumes, mouth wash, cleaners, petroleum products, etc.). The works presented in this dissertation, were published in the Journal of the American Chemical Society (JACS, 2009) and Nano Letters (2010), won first place in the National Defense Research contest in (2009) and has been granted a patent (WO 2010/030874 A1). In addition, other work related to conductive polymer junctions and their sensing capabilities has been published in Applied Physics Letters (2005) and IEEE sensors journal (2008). / Dissertation/Thesis / Ph.D. Electrical Engineering 2012

Made available in DSpace on 2014-06-11T19:35:05Z (GMT). No. of bitstreams: 0 Previous issue date: 2004Bitstream added on 2014-06-13T20:06:21Z : No. of bitstreams: 1 chaker_ja_dr_araiq.pdf: 4471758 bytes, checksum: 44afb42e6a0e98b7d57c6d4412d9ff10 (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Materiais híbridos orgânicos-inorgânicos são materiais bifásicos onde a interpenetração das fases em uma escala nanométrica permite preparar materiais com propriedades inéditas. Este é o caso dos eletrólitos sólidos transparentes siloxano-poli(propileno óxido) estudados neste trabalho de doutorado. Este trabalho visou estabelecer correlações entre as propriedades de condução iônica e as características estruturais destes híbridos que são preparados pelo processo sol-gel. Os objetivos específicos propostos no projeto original incluem os seguintes itens: (a) estabelecer correlações entre a estrutura e as propriedades determinantes da condutividade iônica; (b) analisar a estrutura local do dopante, sua localização no sistema, e assim determinar os sítios de adsorção bem como sua participação na formação da ligação O-Na-O ou O-K-O envolvendo oxigênios tipo éter da cadeia polimérica; (c) determinar o efeito da retração e da formação de domínios com correlação espacial em função dos diferentes sais dopantes estudados sobre as propriedades de condução iônica; (d) comparar as propriedades e estrutura dos híbridos preparados com polímeros de diferentes massas moleculares e concentrações de dopante. Para isto, estudos das propriedades microestruturais, foram realizados através das técnicas de espalhamento de raios X, e análises da estrutura local por absorção de raios X (XANES e EXAFS), e RMN 23Na e 19F, corroborados com as propriedades de condução iônica dos materiais, além de medidas de espectroscopia Raman. Foram estabelecidas diversas correlações entre a estrutura e as propriedades dos materiais. Foi verificado, para amostras dopadas com KCF3SO3, que as amostras mais condutoras são aquelas que possuem um maior número de oxigênios ao redor do potássio. Paralelo... / Siloxane-poly(oxi propylene) (PPO) or Siloxane-poly(oxi propylene) hybrid materials prepared by the sol-gel route show increasing scientific and technological interest due to its particular structure in which the polymer chains are grafted to the inorganic nanoparticules. When doped with alkaline salts these hybrids present ionic conductivity similar to that of ionic conductive polymers (10-4 S/cm), and both their mechanical and optical properties are improved. However, the nature of the mobile species, are responsible for ther conductivity (free ions, ion-pairs, aggregates) is not well established. So that the knowledge of the nature and the local structure around the mobile ions is the challenger to improve the ionic properties. The ain of this work was to establish the correlations between the local structure around the charge carriers (coordination shell, solvation sphere) and the macroscopic conductivity. To reach this objective the local structure was probed by X ray absorption (XANES and EXAFS), Raman and NMR spectroscopy and the results related to that obtained from conductivity measurements.

Resumo: Materiais híbridos orgânicos-inorgânicos são materiais bifásicos onde a interpenetração das fases em uma escala nanométrica permite preparar materiais com propriedades inéditas. Este é o caso dos eletrólitos sólidos transparentes siloxano-poli(propileno óxido) estudados neste trabalho de doutorado. Este trabalho visou estabelecer correlações entre as propriedades de condução iônica e as características estruturais destes híbridos que são preparados pelo processo sol-gel. Os objetivos específicos propostos no projeto original incluem os seguintes itens: (a) estabelecer correlações entre a estrutura e as propriedades determinantes da condutividade iônica; (b) analisar a estrutura local do dopante, sua localização no sistema, e assim determinar os sítios de adsorção bem como sua participação na formação da ligação O-Na-O ou O-K-O envolvendo oxigênios tipo éter da cadeia polimérica; (c) determinar o efeito da retração e da formação de domínios com correlação espacial em função dos diferentes sais dopantes estudados sobre as propriedades de condução iônica; (d) comparar as propriedades e estrutura dos híbridos preparados com polímeros de diferentes massas moleculares e concentrações de dopante. Para isto, estudos das propriedades microestruturais, foram realizados através das técnicas de espalhamento de raios X, e análises da estrutura local por absorção de raios X (XANES e EXAFS), e RMN 23Na e 19F, corroborados com as propriedades de condução iônica dos materiais, além de medidas de espectroscopia Raman. Foram estabelecidas diversas correlações entre a estrutura e as propriedades dos materiais. Foi verificado, para amostras dopadas com KCF3SO3, que as amostras mais condutoras são aquelas que possuem um maior número de oxigênios ao redor do potássio. Paralelo...(Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Siloxane-poly(oxi propylene) (PPO) or Siloxane-poly(oxi propylene) hybrid materials prepared by the sol-gel route show increasing scientific and technological interest due to its particular structure in which the polymer chains are grafted to the inorganic nanoparticules. When doped with alkaline salts these hybrids present ionic conductivity similar to that of ionic conductive polymers (10-4 S/cm), and both their mechanical and optical properties are improved. However, the nature of the mobile species, are responsible for ther conductivity (free ions, ion-pairs, aggregates) is not well established. So that the knowledge of the nature and the local structure around the mobile ions is the challenger to improve the ionic properties. The ain of this work was to establish the correlations between the local structure around the charge carriers (coordination shell, solvation sphere) and the macroscopic conductivity. To reach this objective the local structure was probed by X ray absorption (XANES and EXAFS), Raman and NMR spectroscopy and the results related to that obtained from conductivity measurements. / Orientador: Celso Valentim Santilli / Coorientador: Karim Dahmouche / Doutor

Neste trabalho investigamos o transporte eletrônico em dispositivos com estrutura ITO(óxido de estanho dopado com índio)/TiO2(dióxido de titânio)/RRP3HT(poli(3-hexiltiofeno)-regiorregular)/Al através de medidas de resposta espectral de fotocorrente, iluminando os dispositivos ora pelo eletrodo de ITO ora pelo de alumínio. O polímero RRP3HT é um politiofeno regiorregular e exibe uma atividade fotovoltaica relativamente alta. Os filmes de TiO2 e RRP3HT foram obtidos por spin-coating, sendo o óxido depositado a partir de uma dispersão coloidal de nanopartículas e o polímero a partir de uma solução de clorofórmio. O eletrodo de Al foi evaporado termicamente sobre o filme de polímero. As medidas de fotocorrente foram realizadas com o uso de uma lâmpada de Xe de 450W e de um monocromador e, depois de diversas medidas tendo a temperatura e a voltagem aplicada como parâmetros, obtivemos uma grande quantidade de importantes dados elétricos sobre os dispositivos. Dependendo das condições experimentais observamos diferentes respostas de fotocorrente: simbática ou antibática. Um modelo baseado em mecanismos de recombinação e na fotogeração de cargas, incluindo o perfil de absorção do RRP3HT, permitiu a obtenção de parâmetros elétricos importante em aplicações desse polímero a dispositivos fotodetectores e células solares. / In this work we investigated electronic transport phenomena in an ITO/TiO2/RRP3HT/Al structure using photoconductivity spectral response when devices were illuminated either by the ITO electrode or by the aluminum. RRP3HT is the regioregular poly(3-hexylthiophene), a polymer that exhibits a relatively strong photovoltaic activity. RRP3HT were dissolved in a solution of chloroform and nanoparticles of TiO2 were used in a colloidal dispersion. Both thin films of TiO2 and P3HT were deposited by spin coating technique over a commercial glass covered with ITO, and Al electrode was vacuum evaporated. Photoconductivity measurements were carried out making use of a Xenon lamp of 450 W and a monochromator to produce a single spectral line. After several measurements, having temperature and constant applied voltage as parameters, we obtained a great amount of important electrical data for the devices. Depending on the experimental conditions we obtained different photocurrent response, i. e. symbatic or antibatic. A model based on recombination mechanisms and photogenerated charges, including the absorption profile of the RRP3HT, allowed us to get some electrical parameters that are important for photovoltaic and photoconductive applications.

Neste trabalho, foram adicionadas diferentes concentrações de polianilina (PANI) a uma solução polimérica de poliétersulfona (PES) e N-metil-pirrolidona (NMP), com o intuito de sintetizar membranas de ultrafiltração a partir do método de inversão de fases. O desafio consistem em combinar alta condutividade elétrica, boas propriedades mecânicas e oxidação eletroquímica, permitindo assim que a oxidação de possíveis contaminantes ocorra ao mesmo tempo em que a membrana atua como uma barreira de filtração seletiva. O efeito da adição de PANI foi avaliado quanto à morfologia da membrana, capacidade de separação e desempenho, em termos de permeabilidade e condutividade. As membranas modificadas apresentaram uma morfologia muito singular quando analisadas pelo Microscópio Eletrônico de Varredura (MEV), poros maiores foram identificados, ausência da camada seletiva, diminuição da camada inferior e grandes fases aglomeradas ao longo da seção transversal. Devido ao aumento do tamanho dos poros, a seletividade das membranas modificadas foi comprometida. Os resultados de porosidade para as membranas modificadas variaram entre 53 e 66%. A permeabilidade e a condutividade das membranas modificadas aumentaram à medida que a concentração de PANI também aumentou. O fluxo mediano obtido para a membrana com concentração de 40% de PANI foi de 835 L.m-2.h-1, cerca de 5 vezes maior do que o fluxo mediano obtido para a membrana controle. Já a condutividade mediana obtida para a mesma membrana modificada foi de 1,7x10-6 S, cerca de 15 vezes maior do que a membrana controle. Durante o teste de voltametria cíclica não foram observadas reações de oxidação-redução, nem da solução de ferro-cianeto nem da própria polianilina, ao aplicar uma tensão variando entre -0,2 V e 0,8 V. Desta forma, a partir dos resultados, pode-se afirmar que a adição de Polianilina alterou a morfologia e o desempenho das membranas modificadas, destacando o incremento na permeabilidade, hidrofilicidade e condutividade, mantendo sua característica de ser uma barreira de filtração seletiva. / In this work, different concentrations of Polyaniline (PANI) were added to a polymer solution made of Polyethersulfone (PES) and N-methylpyrrolidone (NMP), in order to synthesize ultrafiltration membranes by the phase inversion method and the challenge of combine high electrical conductivity, good mechanical properties and electrochemical oxidation, thus allowing the oxidation of matter to occur at the same time that the membrane acts as a selective and reliable filtration barrier. The effect of PANI addition was evaluated regarding the membrane morphology, separation capacity and performance in terms of permeability and conductivity. The modified membranes presented a very unique morphology when analyzed by the Scanning Electron Microscope (SEM), larger pores were identified, absence of the selective layer, decrease of the lower layer and large agglomerated phases with phase contour characterization along the cross section. Due to the increase in pore size, the selectivity of the modified membranes was compromised. The porosity results for the modified membranes are only reflections of the morphology obtained, and the median porosities varied between 53 and 66%. The permeability and conductivity of the modified membranes increased as the PANI concentration also increased. The median flow obtained for the membrane with 40% PANI concentration was 835 L.m-2.h-1, about 5 times higher than the median flow obtained for the control membrane. The median conductivity obtained for the same modified membrane was 1.7x10-6 S, about 15 times higher than the control membrane. During the cyclic voltammetry test, no oxidation-reduction reactions were observed, neither the iron-cyanide solution nor the polyaniline itself, when applying a voltage ranging from -0.2 V to 0.8 V. From the results, it can be affirmed that the addition of polyaniline particles altered the morphology and performance of the modified membranes, highlighting the increase in permeability, hydrophilicity and conductivity, maintaining its characteristics of being a selective filtration barrier.

Abstract In gravure offset printing, ink is transferred with the help of an offset material from a patterned gravure plate to a substrate. This thesis is concerned with the study and further development of this printing process for electronics; on alumina, glass and polymers. The work has been divided into five parts. In the first section, the printing process is described. The second section describes the composition of the inks for gravure offset printing and the resulting ink properties. It also presents the ink transfer mechanism; the model that explains how the ink is transferred between an offset material and a substrate. The third chapter details the printing process explained by a solvent absorption mechanism. The forth chapter describes the firing/curing of printed samples and their properties. The last chapter describes applications of the method. The inks used to produce conductors on ceramics (ceramic inks) and conductors on polymers (polymer inks) contain silver particles, and were under development for gravure offset printing. The major achieved properties were the high ink pickup to the offset blanket and high transfer percentage to the substrate. 100% ink transfer from blanket to substrate for ceramic inks and almost 100% ink transfer for polymer inks was obtained. The printing of ceramic inks was able to produce 8 μm of relatively thick, 300 μm wide lines with &lt; 10 mΩ/sq. resistance. The minimum line width for conducting lines was 35 μm, with one printing. Multi printing was applied producing as many as 10 times wet-on-wet multiprinted lines with 100 % ink transfer from blanket to substrate resulting in a square resistance of 1mΩ/sq. Polymer inks were able produce a square resistance of 20 mΩ/sq. for 300 μm wide lines after curing at 140 °C for about 15 min, and the minimum width was down to 70 μm. In the optimised manufacturing process, the delay time on the blanket was reduced to 3 s. In addition to ultra-fine-line manufacturing of conductors, the method enables the manufacture of special structures e.g. laser-solder contact pads with 28/28 μm lines/spaces resolution. With industrial printing equipment it is possible to produce 100 m2/h with the demonstrated printing properties.