Esta Tese aborda duas importantes vertentes de pesquisa em polímeros conjungados (PC), bastante relevantes na Eletrônica Orgânica (EO) e na área de Biossensores. Com respeito à EO, estudam-se as interfaces PC - metal (M) por meio da espectroscopia vibracional de Geração de Soma de Frequências, cuja sigla mais comum é SFG - derivada do seu nome inglês Sum Frequency Generation. Este problema é de grande importância porque na interface acontecem fenômenos essenciais para o funcionamento de dispositivos, como por exemplo a injeção e coleta de cargas. Deve-se ressaltar que poucos trabalhos na literatura investigam o problema da interface PC-M, e aqueles que o fazem, ou sondam interfaces diferentes daquelas de dispositivos reais, ou são estudos teóricos, com necessidade da comprovação experimental, ou ainda usam ferramentas sem especificidade a interfaces. Neste ponto, o estudo da interface PC-M feita nesta Tese apresenta como expressivo diferencial o uso da espectroscopia SFG às interfaces PC-M do tipo encontrado em dispositivos usuais da EO. A técnica SFG permite determinar o ordenamento molecular nas interfaces através da análise quantitativa das vibrações das duplas ligações dos PC, que é a região molecular ativa durante o funcionamento dos dispositivos da EO. Além disso, a simples análise qualitativa dos espectros SFG indica a ocorrência de dopagem (transferência de carga) em algumas interfaces PC-M. Dentre as conclusões deste trabalho, destaca-se o entendimento de como a organização molecular da interface influencia a transferência de carga espontânea entre PC e M. Para tanto, construiu-se um modelo de ordenamento molecular (MOM) baseado nos resultados de SFG, que levando em conta o alinhamento energético (AE) entre os níveis de Fermi dos materiais na interface, estabelece a correlação entre arranjo molecular e transferência de carga. Para o estudo, escolheram-se os metais Al e Au, e os PCs comerciais poli(3-hexiltiofeno) (P3HT) regioregular e poli(9,9-dioctilfluoreno) (PF8), por serem comumente usados em dispositivos da EO. A combinação MOM-AE explica, por exemplo, a não ocorrência de dopagem nas interfaces P3HT-M. Neste caso, o MOM prevê o empacotamento π ao longo do plano da superfície metálica de modo que o contato PC-M estabelece-se através das cadeias alquila (isolantes) do P3HT. No caso de PF8-Au, verifica-se dopagem tipo p. Na interface PF8-Al, embora existam cadeias alinhadas à superfície metálica e com o plano dos anéis paralelo à mesma, favorecendo a transferência de carga, a igualdade das funções trabalho (AE) de cada material impede a dopagem. Também se verificaram diferenças quantitativas no ordenamento molecular do PC em função do método de preparação da amostra: i) PC depositado sobre substrato metálico ou ii) metal evaporado sobre filme do PC. De forma qualitativa, analisam-se copolímeros: poli(9,9-n-dihexil-2,7-fluorenodiilvinileno-alt-2,5 tiofeno) (L29) e iv) poli(9,9-di-hexilfluorenodiilvinileno-alt-1,4-fenilenovinileno) (L16), em interfaces com os mesmos metais. Neste caso, observa-se dopagem em todas as interfaces. O estudo inserido na área de Biosensores é motivado pela vasta gama de trabalhos que relatam o uso das propriedades ópticas (PO) de PEC como ferramenta sensora em sistemas biológicos, e sua modulação via interação com surfactantes. Foi então realizada a análise, por meio de técnicas de espectroscopia óptica convencional - Absorção Óptica (AO) e Fotoluminescência (PL) - e da técnica de Microcalorimetria Isotérmica por Titulação, da interação entre polieletrólitos conjugados (PEC) e surfactantes em solução aquosa. A formação do complexo PEC+surfactante ocorre mediante modificação do estado de agregação do polímero que, por sua vez, gera alterações em suas POs. Assim este estudo visa o entendimento de como as forças hidrofóbicas, eletrostáticas, fatores termodinâmicos e estrutura química de PECs e surfactantes influenciam as POs dos complexos formados. Pela primeira vez na literatura, relata-se a ocorrência de interação eletrônica entre PEC e surfactante. Isto acontece no caso do complexo formado pelo PEC aniônico, derivado do PPV, o poli [5 - metoxi 2 - (3 sulfopropoxi) - 1,4 fenilenovinileno] (MPSPPV), e o surfactante dodecilbenzeno sulfonato de sódio (DBS). A inédita interação eletrônica ocorre em solução, resultando em dramáticas modificações nos estados eletrônicos do MPSPPV devido à forte interação hidrofóbica com o DBS. Isto gera expressivos deslocamentos, em torno de 0,5 eV ou 100 nm, para a luminescência do complexo em relação à do MPSPPV puro. Isso torna o complexo MPSPPV+DBS bastante promissor, pois apresenta POs sintonizáveis, em função da concentração de surfactante. Para explicar as novas POs do complexo MPSPPV+DBS, propõe-se um modelo baseado na formação do complexo MPSPPV+DBS autoorganizado em um arranjo molecular específico. Neste arranjo, a proximidade entre os grupos conjugados de cada molécula leva ao realinhamento dos níveis energéticos, sob regime de forte acoplamento. A fim de estender e generalizar o trabalho, estudam-se surfactantes de diversas estruturas químicas ao constituírem complexos com o PEC aniônico (MPSPPV) e com o PEC catiônico, o poli [2,5 - bis ( 2 - (n, n -dietilamônio brometo) etoxi) - 1, 4 - alt - 1, 4 - fenileno] (DAB). Os surfactantes estudados são: dodecil sulfato de sódio (SDS), dodecilbenzeno sulfonato de sódio (DBS), t - octil - fenoxi - polietoxi - etanol (TX100) e dodeciltrimetil brometo de amônia (DTAB). Essas descobertas podem ter implicações importantes para o projeto de plataformas para aplicações em biosensores, e para a melhoria do desempenho e durabilidade de dispositivos de EO. / This Thesis addresses two important branches of the conjugated polymer (CP) research which are relevant to Organic Electronics (OE) and Biosensors. Concerning OE, the interfaces CP-metal (M) are studied by the Sum-Frequency Generation (SFG) vibrational spectroscopy. This problem is quite important since fundamental phenomena that are essential to the performance of organic devices take place at this interface, such as charge injection and collection. It should be stressed that few papers in the literature focus on the CP-M interface, and they either probe different interfaces from those present in the devices, or use analytical tools without specificity to the interfaces, or else they are theoretical studies requiring experimental verification. In this regard, the study of the CP-M interface accomplished in this Thesis shows the advantage over previous studies due to the use of SFG spectroscopy to the CP-M interfaces usually found in the organic devices. Furthermore, SFG spectroscopy allows a determination of the molecular arrangement at the interfaces by a quantitative analysis of the vibrations of the double bonds, which are the molecular regions directly involved in the operation of OE devices. Furthermore, a simple and qualitative analysis of the SFG spectra leads to the recognition of doping (charge transfer) in some CP-M interfaces. Among the most important conclusions, emerges the understanding of how the molecular order affects the spontaneous charge transfer between PC and M at the interface. This was attained through a molecular order model (MOM) based on the SFG results and on the energy alignment (EA) between the Fermi levels of the PC and metal at the interface. For this study were used the metals Al and Au, and the commercial CPs regioregular poly(3-hexylthiofene) (P3HT) and poly(9,9-dioctylfluorene) (PF8), which are commonly used in OE. The MMO-EA combination explains that reason for not detecting doping in P3HT-M interfaces, where the MMO has suggested π-stacking along the surface plane, resulting in little interaction between CPs electrons with the metal. The p-doping is found in the PF8-Au interface. For the interface PF8-Al, although the MMO implies that the polymeric chains are aligned to the metallic surface with their aromatic rings parallel to the surface, which is favorable for charge transfer process, the equality between the work functions (EA) of the materials prevents doping. It has also been observed quantitative differences in chain orientation for samples prepared by different methods: i) CP film spread over metallic substrates and ii) metal evaporated onto CP films. In a qualitative way, the 2 copolymers - poly(9,9-n-dihexyl-2,7-fluorenediilvinylene-alt-2,5 thiophene) (L29) and poly(9,9-di-hexylfluorenediilvinylene-alt-1,4-fenilenevinylene) (L16) - were analyzed at interfaces with the same metals. In all these cases, doping is observed. The study related to Biosensors is motivated by the large number of paper reporting the use of optical properties (OP) of CPE as a sensing tool in biological systems, and their modulation via interaction with surfactants. Therefore, an investigation of the interaction between conjugated polyelectrolytes (CPE) and surfactants in aquous solution was performed by convencional optical spectroscopy - Optical Absorbance (OA) and Photoluminescence (PL) - and the thermodynamic technique named Isothermal Titration Microcalometry. The formation of the CPE+surfactant complex is followed by modifications in the aggregation state of the polymer, which in turn generates modifications on its OPs. Therefore, this study aims the understanding of how hydrophobic and/or electrostatic forces, thermodynamic factors and chemical structure of the CPE and surfactants affect the OPs of the complexes. For the first time in the literature related to PEC+surfactant complexes, electrocnic interaction is noticed when the an anionic PPV derivative, poly [5 - metoxy 2 (3 sulfopropoxi) 1,4 fenilenovinileno] (MPSPPV), interacts with the surfactant Sodium dodecylbenzene sulfatonate (DBS). The striking electronic interaction occours in aqueous solution and dramatic modifications takes place in the electronic states of MPSPPV due to its strong hydrophobic interaction with DBS. The PL of complex MPSPPV+DBS presents a remarkable blue-shift of about 0,5 eV (or 100 nm), when compared to the PL of MPSPPV. Consequently, the MPSPPV+DBS has tunable OPs, within a wide range of the visible spectrum, as a function of the surfactant concentration. In order to explain these changes of OPs, is proposed a model based on the formation of a self-organized MPSPPV+DBS complex with a specific molecular arrangement. In this hybrid aggregate, the small distance between the conjugated groups of each molecule leads to a realignment of the energy levels. The complete study, however, investigated the complexes formed with the surfactants: Sodium dodecyl sulfate (SDS), Sodium dodecylbenzene sulfatonate (DBS), t - octyl - phenoxy - polyethoxy - ethanol (TX100) and dodecyltrimethyl Ammonium Bromide (DTAB), in interaction with both the anionic PEC (MPSPPV) and the cationic poly [2,5 - bys ( 2 - (n, n -diethylammonium bromide) ethoxy) - 1, 4 - alt - 1, 4 - fenylene] (DAB). These discoveries are expected to have important implications to the design of platforms for biosensor applications, and to the improvement of performance and durability of OE devices.

Made available in DSpace on 2014-06-11T19:31:04Z (GMT). No. of bitstreams: 0 Previous issue date: 2009-11-16Bitstream added on 2014-06-13T19:01:19Z : No. of bitstreams: 1 savu_r_dr_bauru.pdf: 10688901 bytes, checksum: 4c1846c73d88b2e598b43e7a14ea1b7c (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / A presente pesquisa teve como principal objetivo a obtenção de estruturas nanométricas de óxido de índio, óxido de estanho e óxido de zinco por evaporação térmica e síntese hidrotérmica e a construção e teste de sensores de gases e de fotodetectores de ultravioleta baseados nessas nanoestruturas. Foram realizados estudos da influência dos parâmetros experimentais das duas rotas de síntese usadas sobre as morfologias e as propriedades das estruturas. Para a obtenção das camadas nanoestruturadas por evaporação térmica foi especialmente construído um forno tubular que permitiu o controle da temperatura de deposição independente da temperatura de evaporação e da distância entre a fonte de evaporação e o substrato. Esses parâmetros, pouco explorados nas pesquisas reportadas na literatura, exerceram uma grande influência sobre a morfologia e as propriedades dos nanofios obtidos. O equipamento permitiu ainda um controle preciso da composição da atmosfera e da pressão de síntese. Na síntese química em solução, a construção de um reator hidrotérmico permitiu o estudo da influência da taxa de resfriamento sobre as dimensões, cristalinidade, morfologia e propriedades das nanoestruturas. Esse estudo, o primeiro do gênero na literatura, ressaltou a importância no controle deste parâmetro para sintetizar estruturas com propriedades melhoradas. As demais variáveis estudadas foram: a concentração das soluções, as camadas catalisadoras, a temperatura e o tempo de síntese. Foram testadas duas estratégias para a obtenção dos filmes nanoestruturados: spin-coating de suspensões de nanoestruturas sobre substratos de silício oxidado ou o crescimento das mesmas, durante a síntese, sobre substratos com camadas catalisadoras de zinco. Os nanofios e as camadas funcionais foram caracterizados por Difração de Raios-X (DRX), Microscopia Eletrônica de Varredura... / The subject of this thesis covers the synthesis and growth of indium, tin and zinc oxide nanostructures by thermal evaporation and hydrothermal synthesis and the fabrication and testing of gas sensors and ultraviolet photodetectors based on these nanosized structures. For both chemical and physical routes, the influence of processing conditions over the morphology, dimensions and electrical properties of the nanowires was investigated. In order to obtain nanostructured layers by thermal evaporation a tubular furnace was specifically builti, allowed the control of the source-substrate distance and the deposition temperature independently of the evaporation one. These parameters, slightly explored in the literature, granted a big influence over the nanowires morphology and properties. Moreover, the equipment permitted the control of deposition atmosphere and pressure. The design and assembly of a hydrothermal reactor allowed studying the influence of the cooling rate over the dimension, morphology, cristallinity and, consequently, the properties of the nanostructures. This study highlighted the importance of controlling this particular parameter in the hydrothermal process, yielding nanostructured materials with enhanced properties. Variables such as solution concentration, synthesis temperature and time, surfanctants and precursors were also explored in the hydrothermal process. In order to obtain nanostructured thin films using the chemical bath deposition, two processing techniques were employed: spin-coating of powder suspensions over oxidized silicon substrates and nanostructured anisotropic growth directly from solution using zinc coated substrates. The nanowires and the functional nanostructured layers were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE - SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS)... (Complete abstract click electronic access below)

Failure analysis and optimization of semiconducting devices request knowledge of their electrical properties. To meet the demands of today’s semiconductor industry, an electrical nanometrology technique is required which provides quantitative information about the doping profile and which enables scans with a lateral resolution in the sub-10 nm range. In the presented work it is shown that Kelvin probe force microscopy (KPFM) is a very promising electrical nanometrology technique to face this challenge. The technical and physical aspects of KPFM measurements on semiconductors required for the correct interpretation of the detected KPFM bias are discussed. A new KPFM model is developed which enables the quantitative correlation between the probed KPFM bias and the dopant concentration in the investigated semiconducting sample. Quantitative dopant profiling by means of the new KPFM model is demonstrated by the example of differently structured, n- and p-type doped silicon. Additionally, the transport of charge carriers during KPFM measurements, in particular in the presence of intrinsic electric fields due to vertical and horizontal pn junctions as well as due to surface space charge regions, is discussed. Detailed investigations show that transport of charge carriers in the semiconducting sample is a crucial aspect and has to be taken into account when aiming for a quantitative evaluation of the probed KPFM bias.

Existing growth methods produce single-walled carbon nanotubes (SWCNTs) with a range of structures and electronic properties, but many potential applications require pure nanotube samples. Density gradient ultracentrifugation (DGU) has recently emerged as a technique for sorting as-grown mixtures of single-walled nanotubes into their distinct ( n,m ) structural forms, but this approach has been limited to samples containing only a small number of nanotube structures, and has often required repeated DGU processing. For the first time, it has been shown that the use of tailored nonlinear density gradient ultracentrifugation (NDGU) can significantly improve DGU separations. This new sorting process readily separated highly polydisperse samples of SWCNTs grown by the HiPco method in a single step to give fractions enriched in any of ten different ( n,m ) species. In addition, minor variants of the method allowed separation of the minor-image isomers (enantiomers) of seven ( n,m ) species. Optimization of this new approach was aided by the development of instrumentation that spectroscopically mapped nanotube contents inside undisturbed centrifuge tubes. Besides, sorted nanotube samples enabled the discovery of novel oxygen-doped SWCNTs with remarkable photophysical properties. Modified nanotube samples were produced using mild oxidation of SWCNTs with ozone followed by a photochemical conversion step that induced well-defined changes in emissive properties. As demonstrated for a set of ten separated SWCNT ( n,m ) structures, chemically altered nanotubes possess slightly lower band gap energies with correspondingly longer photoluminescence wavelengths. Treated samples showed distinct, structure-specific near-infrared fluorescence at wavelengths 10 to 15% longer than the pristine semiconducting SWCNTs. Quantum chemical modeling suggests that dopant sites harvest light energy absorbed in undoped nanotube regions by trapping mobile excitons. The oxygen-doped SWCNTs are much easier to detect and image in biological specimen than pristine SWCNTs because they give stronger near-IR emission and do not absorb at the shifted emission wavelength. This novel modification of SWCNT properties may lead to new optical and electronic applications, as it provides a way to change optical band gaps in whole nanotubes or in selected sections.

Nonlinear coherent scattering phenomena from single nanoparticles have been recently proposed as alternative processes for fluorescence in multiphoton microscopy staining. Commonly applied nanoscale materials, however, have reached a certain limit in size dependent detection efficiency of weak nonlinear optical signals. None of the recent efforts in detection of second-harmonic generation (SHG), the lowest order nonlinear process, have been able to cross a ~40 nm size barrier for nanoparticles (NPs), thus remaining at the level of "large" nanoscatterers, even when resorting to the most sensitive detection techniques such as single-photon counting technology. As we realize now, this size limitation can be significantly lowered when replacing dielectric insulators or wide gap semiconductors by direct-gap semiconducting quantum dots (QDs). Herein, a new type of highly nonlinear nanoprobes is engineered in order to surpass above mentioned size barrier at the single nanoparticle scale. We consider two-photon resonant excitation in individual zinc-blende CdTe QDs of about 12.5 nm diameter, which provide efficient coherent SHG radiation, as high as 105 Hz, furthermore exhibiting remarkable sensitivity to spatial orientation of their octupolar crystalline lattice. Moreover, quantum confinement effects have been found to strongly contribute to the second-order nonlinear optical susceptibility χ(2) features. Quantitative characterization of the χ(2) of QDs by way of their spectral dispersion and size dependence is therefore undertaken by single particle spectroscopy and ensemble Hyper-Rayleigh Scattering (HRS) studies. We prove that under appropriate conditions, χ(2) of quantum confined semiconducting structures can significantly exceed that of bulk. Furthermore, a novel type of semiconducting hybrid rod-on-dot (RD) QDs is developed by building up on crystalline moieties of different symmetries, in order to increase their effective quadratic nonlinearity while maintaining their size close to a strong quantum confinement regime. The new complex hybrid χ(2) tensor is analyzed by interfering the susceptibilities from each component, considering different shape and point group symmetries associated to octupolar and dipolar crystalline structures. Significant SHG enhancement is consequently observed, exceeding that of mono-compound QDs, due to a coupling between two nonlinear materials and slower decoherence, which we attribute to the induced spatial charge separation upon photoexcitation.

Resumo: A presente pesquisa teve como principal objetivo a obtenção de estruturas nanométricas de óxido de índio, óxido de estanho e óxido de zinco por evaporação térmica e síntese hidrotérmica e a construção e teste de sensores de gases e de fotodetectores de ultravioleta baseados nessas nanoestruturas. Foram realizados estudos da influência dos parâmetros experimentais das duas rotas de síntese usadas sobre as morfologias e as propriedades das estruturas. Para a obtenção das camadas nanoestruturadas por evaporação térmica foi especialmente construído um forno tubular que permitiu o controle da temperatura de deposição independente da temperatura de evaporação e da distância entre a fonte de evaporação e o substrato. Esses parâmetros, pouco explorados nas pesquisas reportadas na literatura, exerceram uma grande influência sobre a morfologia e as propriedades dos nanofios obtidos. O equipamento permitiu ainda um controle preciso da composição da atmosfera e da pressão de síntese. Na síntese química em solução, a construção de um reator hidrotérmico permitiu o estudo da influência da taxa de resfriamento sobre as dimensões, cristalinidade, morfologia e propriedades das nanoestruturas. Esse estudo, o primeiro do gênero na literatura, ressaltou a importância no controle deste parâmetro para sintetizar estruturas com propriedades melhoradas. As demais variáveis estudadas foram: a concentração das soluções, as camadas catalisadoras, a temperatura e o tempo de síntese. Foram testadas duas estratégias para a obtenção dos filmes nanoestruturados: spin-coating de suspensões de nanoestruturas sobre substratos de silício oxidado ou o crescimento das mesmas, durante a síntese, sobre substratos com camadas catalisadoras de zinco. Os nanofios e as camadas funcionais foram caracterizados por Difração de Raios-X (DRX), Microscopia Eletrônica de Varredura... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The subject of this thesis covers the synthesis and growth of indium, tin and zinc oxide nanostructures by thermal evaporation and hydrothermal synthesis and the fabrication and testing of gas sensors and ultraviolet photodetectors based on these nanosized structures. For both chemical and physical routes, the influence of processing conditions over the morphology, dimensions and electrical properties of the nanowires was investigated. In order to obtain nanostructured layers by thermal evaporation a tubular furnace was specifically builti, allowed the control of the source-substrate distance and the deposition temperature independently of the evaporation one. These parameters, slightly explored in the literature, granted a big influence over the nanowires morphology and properties. Moreover, the equipment permitted the control of deposition atmosphere and pressure. The design and assembly of a hydrothermal reactor allowed studying the influence of the cooling rate over the dimension, morphology, cristallinity and, consequently, the properties of the nanostructures. This study highlighted the importance of controlling this particular parameter in the hydrothermal process, yielding nanostructured materials with enhanced properties. Variables such as solution concentration, synthesis temperature and time, surfanctants and precursors were also explored in the hydrothermal process. In order to obtain nanostructured thin films using the chemical bath deposition, two processing techniques were employed: spin-coating of powder suspensions over oxidized silicon substrates and nanostructured anisotropic growth directly from solution using zinc coated substrates. The nanowires and the functional nanostructured layers were characterized by X-Ray Diffraction (XRD), Field Emission Scanning Electron Microscopy (FE - SEM), Transmission Electron Microscopy (TEM) and X-ray Photoelectron Spectroscopy (XPS)... (Complete abstract click electronic access below) / Orientador: Maria Aparecida Zaghete Bertochi / Coorientador: Elson Longo / Banca: Antonio Ricardo Zanatta / Banca: Mônica Alonso Cotta / Banca: Talita Mazon Anselmo / Banca: Sidney José Lima Ribeiro / O Programa de Pós-Graduação em Ciência e Tecnologia de Materiais, PosMat, tem caráter institucional e integra as atividades de pesquisa em materiais de diversos campi da Unesp / Doutor

Esta Tese aborda duas importantes vertentes de pesquisa em polímeros conjungados (PC), bastante relevantes na Eletrônica Orgânica (EO) e na área de Biossensores. Com respeito à EO, estudam-se as interfaces PC - metal (M) por meio da espectroscopia vibracional de Geração de Soma de Frequências, cuja sigla mais comum é SFG - derivada do seu nome inglês Sum Frequency Generation. Este problema é de grande importância porque na interface acontecem fenômenos essenciais para o funcionamento de dispositivos, como por exemplo a injeção e coleta de cargas. Deve-se ressaltar que poucos trabalhos na literatura investigam o problema da interface PC-M, e aqueles que o fazem, ou sondam interfaces diferentes daquelas de dispositivos reais, ou são estudos teóricos, com necessidade da comprovação experimental, ou ainda usam ferramentas sem especificidade a interfaces. Neste ponto, o estudo da interface PC-M feita nesta Tese apresenta como expressivo diferencial o uso da espectroscopia SFG às interfaces PC-M do tipo encontrado em dispositivos usuais da EO. A técnica SFG permite determinar o ordenamento molecular nas interfaces através da análise quantitativa das vibrações das duplas ligações dos PC, que é a região molecular ativa durante o funcionamento dos dispositivos da EO. Além disso, a simples análise qualitativa dos espectros SFG indica a ocorrência de dopagem (transferência de carga) em algumas interfaces PC-M. Dentre as conclusões deste trabalho, destaca-se o entendimento de como a organização molecular da interface influencia a transferência de carga espontânea entre PC e M. Para tanto, construiu-se um modelo de ordenamento molecular (MOM) baseado nos resultados de SFG, que levando em conta o alinhamento energético (AE) entre os níveis de Fermi dos materiais na interface, estabelece a correlação entre arranjo molecular e transferência de carga. Para o estudo, escolheram-se os metais Al e Au, e os PCs comerciais poli(3-hexiltiofeno) (P3HT) regioregular e poli(9,9-dioctilfluoreno) (PF8), por serem comumente usados em dispositivos da EO. A combinação MOM-AE explica, por exemplo, a não ocorrência de dopagem nas interfaces P3HT-M. Neste caso, o MOM prevê o empacotamento π ao longo do plano da superfície metálica de modo que o contato PC-M estabelece-se através das cadeias alquila (isolantes) do P3HT. No caso de PF8-Au, verifica-se dopagem tipo p. Na interface PF8-Al, embora existam cadeias alinhadas à superfície metálica e com o plano dos anéis paralelo à mesma, favorecendo a transferência de carga, a igualdade das funções trabalho (AE) de cada material impede a dopagem. Também se verificaram diferenças quantitativas no ordenamento molecular do PC em função do método de preparação da amostra: i) PC depositado sobre substrato metálico ou ii) metal evaporado sobre filme do PC. De forma qualitativa, analisam-se copolímeros: poli(9,9-n-dihexil-2,7-fluorenodiilvinileno-alt-2,5 tiofeno) (L29) e iv) poli(9,9-di-hexilfluorenodiilvinileno-alt-1,4-fenilenovinileno) (L16), em interfaces com os mesmos metais. Neste caso, observa-se dopagem em todas as interfaces. O estudo inserido na área de Biosensores é motivado pela vasta gama de trabalhos que relatam o uso das propriedades ópticas (PO) de PEC como ferramenta sensora em sistemas biológicos, e sua modulação via interação com surfactantes. Foi então realizada a análise, por meio de técnicas de espectroscopia óptica convencional - Absorção Óptica (AO) e Fotoluminescência (PL) - e da técnica de Microcalorimetria Isotérmica por Titulação, da interação entre polieletrólitos conjugados (PEC) e surfactantes em solução aquosa. A formação do complexo PEC+surfactante ocorre mediante modificação do estado de agregação do polímero que, por sua vez, gera alterações em suas POs. Assim este estudo visa o entendimento de como as forças hidrofóbicas, eletrostáticas, fatores termodinâmicos e estrutura química de PECs e surfactantes influenciam as POs dos complexos formados. Pela primeira vez na literatura, relata-se a ocorrência de interação eletrônica entre PEC e surfactante. Isto acontece no caso do complexo formado pelo PEC aniônico, derivado do PPV, o poli [5 - metoxi 2 - (3 sulfopropoxi) - 1,4 fenilenovinileno] (MPSPPV), e o surfactante dodecilbenzeno sulfonato de sódio (DBS). A inédita interação eletrônica ocorre em solução, resultando em dramáticas modificações nos estados eletrônicos do MPSPPV devido à forte interação hidrofóbica com o DBS. Isto gera expressivos deslocamentos, em torno de 0,5 eV ou 100 nm, para a luminescência do complexo em relação à do MPSPPV puro. Isso torna o complexo MPSPPV+DBS bastante promissor, pois apresenta POs sintonizáveis, em função da concentração de surfactante. Para explicar as novas POs do complexo MPSPPV+DBS, propõe-se um modelo baseado na formação do complexo MPSPPV+DBS autoorganizado em um arranjo molecular específico. Neste arranjo, a proximidade entre os grupos conjugados de cada molécula leva ao realinhamento dos níveis energéticos, sob regime de forte acoplamento. A fim de estender e generalizar o trabalho, estudam-se surfactantes de diversas estruturas químicas ao constituírem complexos com o PEC aniônico (MPSPPV) e com o PEC catiônico, o poli [2,5 - bis ( 2 - (n, n -dietilamônio brometo) etoxi) - 1, 4 - alt - 1, 4 - fenileno] (DAB). Os surfactantes estudados são: dodecil sulfato de sódio (SDS), dodecilbenzeno sulfonato de sódio (DBS), t - octil - fenoxi - polietoxi - etanol (TX100) e dodeciltrimetil brometo de amônia (DTAB). Essas descobertas podem ter implicações importantes para o projeto de plataformas para aplicações em biosensores, e para a melhoria do desempenho e durabilidade de dispositivos de EO. / This Thesis addresses two important branches of the conjugated polymer (CP) research which are relevant to Organic Electronics (OE) and Biosensors. Concerning OE, the interfaces CP-metal (M) are studied by the Sum-Frequency Generation (SFG) vibrational spectroscopy. This problem is quite important since fundamental phenomena that are essential to the performance of organic devices take place at this interface, such as charge injection and collection. It should be stressed that few papers in the literature focus on the CP-M interface, and they either probe different interfaces from those present in the devices, or use analytical tools without specificity to the interfaces, or else they are theoretical studies requiring experimental verification. In this regard, the study of the CP-M interface accomplished in this Thesis shows the advantage over previous studies due to the use of SFG spectroscopy to the CP-M interfaces usually found in the organic devices. Furthermore, SFG spectroscopy allows a determination of the molecular arrangement at the interfaces by a quantitative analysis of the vibrations of the double bonds, which are the molecular regions directly involved in the operation of OE devices. Furthermore, a simple and qualitative analysis of the SFG spectra leads to the recognition of doping (charge transfer) in some CP-M interfaces. Among the most important conclusions, emerges the understanding of how the molecular order affects the spontaneous charge transfer between PC and M at the interface. This was attained through a molecular order model (MOM) based on the SFG results and on the energy alignment (EA) between the Fermi levels of the PC and metal at the interface. For this study were used the metals Al and Au, and the commercial CPs regioregular poly(3-hexylthiofene) (P3HT) and poly(9,9-dioctylfluorene) (PF8), which are commonly used in OE. The MMO-EA combination explains that reason for not detecting doping in P3HT-M interfaces, where the MMO has suggested π-stacking along the surface plane, resulting in little interaction between CPs electrons with the metal. The p-doping is found in the PF8-Au interface. For the interface PF8-Al, although the MMO implies that the polymeric chains are aligned to the metallic surface with their aromatic rings parallel to the surface, which is favorable for charge transfer process, the equality between the work functions (EA) of the materials prevents doping. It has also been observed quantitative differences in chain orientation for samples prepared by different methods: i) CP film spread over metallic substrates and ii) metal evaporated onto CP films. In a qualitative way, the 2 copolymers - poly(9,9-n-dihexyl-2,7-fluorenediilvinylene-alt-2,5 thiophene) (L29) and poly(9,9-di-hexylfluorenediilvinylene-alt-1,4-fenilenevinylene) (L16) - were analyzed at interfaces with the same metals. In all these cases, doping is observed. The study related to Biosensors is motivated by the large number of paper reporting the use of optical properties (OP) of CPE as a sensing tool in biological systems, and their modulation via interaction with surfactants. Therefore, an investigation of the interaction between conjugated polyelectrolytes (CPE) and surfactants in aquous solution was performed by convencional optical spectroscopy - Optical Absorbance (OA) and Photoluminescence (PL) - and the thermodynamic technique named Isothermal Titration Microcalometry. The formation of the CPE+surfactant complex is followed by modifications in the aggregation state of the polymer, which in turn generates modifications on its OPs. Therefore, this study aims the understanding of how hydrophobic and/or electrostatic forces, thermodynamic factors and chemical structure of the CPE and surfactants affect the OPs of the complexes. For the first time in the literature related to PEC+surfactant complexes, electrocnic interaction is noticed when the an anionic PPV derivative, poly [5 - metoxy 2 (3 sulfopropoxi) 1,4 fenilenovinileno] (MPSPPV), interacts with the surfactant Sodium dodecylbenzene sulfatonate (DBS). The striking electronic interaction occours in aqueous solution and dramatic modifications takes place in the electronic states of MPSPPV due to its strong hydrophobic interaction with DBS. The PL of complex MPSPPV+DBS presents a remarkable blue-shift of about 0,5 eV (or 100 nm), when compared to the PL of MPSPPV. Consequently, the MPSPPV+DBS has tunable OPs, within a wide range of the visible spectrum, as a function of the surfactant concentration. In order to explain these changes of OPs, is proposed a model based on the formation of a self-organized MPSPPV+DBS complex with a specific molecular arrangement. In this hybrid aggregate, the small distance between the conjugated groups of each molecule leads to a realignment of the energy levels. The complete study, however, investigated the complexes formed with the surfactants: Sodium dodecyl sulfate (SDS), Sodium dodecylbenzene sulfatonate (DBS), t - octyl - phenoxy - polyethoxy - ethanol (TX100) and dodecyltrimethyl Ammonium Bromide (DTAB), in interaction with both the anionic PEC (MPSPPV) and the cationic poly [2,5 - bys ( 2 - (n, n -diethylammonium bromide) ethoxy) - 1, 4 - alt - 1, 4 - fenylene] (DAB). These discoveries are expected to have important implications to the design of platforms for biosensor applications, and to the improvement of performance and durability of OE devices.

Ce travail porte sur les composés semi-conducteurs à base de séléniures pour la conversion d'énergie par effet photovoltaïque ou thermoélectrique. Une nouvelle famille de céramiques Cu₂GeSe₃-Sb₂Se₃ avec une microstructure unique a été synthétise par un procédé de fusion-trempe. L'influence de la composition du matériau et de l'ajout de l’iode sur la microstructure et les propriétés photoélectriques a été étudiée. Le réseau d’hétérojonctions formé par deux semi-conducteurs à bande interdite relativement étroite a un effet évident sur les propriétés photoélectriques. Le système Cu₃SbSe₄-Sb₂Se₃ a également été étudié avec l'objectif d'éliminer le germanium qui est un élément relativement rare. Et les résultats indiquent que le Cu3SbSe4 peut remplacer le Cu2GeSe3 pour former des hétérojonctions avec Sb₂Se₃, en maintenant une séparation et un transport de charges efficaces. Une approche basée sur une injection à chaud a été utilisée pour la synthèse de matériaux semi-conducteurs à base de séléniures pour des applications photovoltaïque ou thermoélectrique. Des nanoparticules et nano-feuillets monocristallins bidimensionnels de CuSe de haute qualité et ont été obtenus. La structure des nanocristaux de Cu₃Sb₁₋ₓSnxSe₄ a été étudiée et le mécanisme de formation des nano-feuillets a été proposé. Des nanoparticules de Cu₃Sb₁₋ₓSnxSe₄ avec une distribution de taille étroite ont été également synthétisées avec le procédé d’injection à chaud. Ces nanoparticules ont été utilisées comme précurseurs pour la préparation de matériaux massifs par pressage à chaud. Leur performance thermoélectrique a été étudiée. / This work was focused on selenide semiconducting compounds for energy conversion by photovoltaic or thermoelectric effect. A totally new family of Cu₂GeSe₃-Sb₂Se₃ ceramics with a unique microstructure was fabricated directly by melt-quenching method. The influence of the material composition and the iodine addition on the microstructure and photoelectrical properties was investigated. The interpenetrating heterojunction network formed by two relatively narrow bandgap semiconductors has an obvious enhancement effect on the photoelectrical properties. The Cu₃SbSe₄-Sb₂Se₃ system has also been studied with the objective to eliminate the germanium which is a relatively rare element. And the results indicated that Cu₃SbSe₄ can substitute the Cu₂GeSe₃ to form heterojunctions with Sb₂Se₃, maintaining the efficient charge separation and transport. A hot-injection based-approach has been used for the synthesis of selenide semiconducting materials for photovoltaic or thermoelectric applications. CuSe nanoparticles and CuSe nanoplates with high quality single-crystals and two dimensional nanostructure were prepared. The structure of the nanocrystals has been studied and the mechanism of the nanoplates formation has been proposed. Cu₃Sb₁₋ₓSnxSe₄ nanoparticles with a narrow size distribution had also been synthesized through the hot-injection route. They have been used as precursors for the preparation of bulk materials by hot-pressing and their thermoelectric performances have been studied.

La structure de bande et les propriétés électroniques des nanofils d’InAs et d’InSb sont étudiées par transport électronique en régime quasi-balistique et sous un champ magnétique montant jusqu’à 55T. Le régime quasi-balistique est mis en évidence par la quantification de la conductance. La structure de bande est sondée par l’analyse des plateaux de conductance en fonction de la concentration électronique. L’application du champ magnétique lève la dégénérescence de spin et la dégénérescence orbitale. Sous champ magnétique perpendiculaire à l’axe du nanofil, les bandes évoluent vers la quantification de Landau, accompagnée d’une réduction de la rétrodiffusion. Des fluctuations quasi-périodiques de la conductance sont mesurées en fonction du champ magnétique parallèle à l’axe du nanofil. Elles révèlent le confinement des porteurs à l’intérieur du nanofil et la formation d’orbites de Landau dans la direction du transport. Le transport électronique cohérent est mis en évidence par l’observation de fluctuations universelles de conductance et du régime de Fabry-Pérot électronique. Enfin, la mesure de photoconductivité révèle la présence de barrières de Schottky au niveau des contacts et une anisotropie en fonction de la direction de polarisation linéaire inattendue pour des nanofils d’InSb de structure cristalline Blende de Zinc. / The subband structure and electronic properties of InAs and InSb nanowires are studied experimentally by measuring the electronic transport in the quasi-ballistic regime and under magnetic field up to 55T.The quasi-ballistic regime is highlighted by the conductance quantization. The band structure is probed by analyzing the conductance plateaus as a function of the gate voltage. The application of a magnetic field lifts the orbital and spin degeneracy. Under a magnetic field perpendicular to the NW axis subbands evolved towards Landau quantization together with backscattering reduction. Fluctuations of the magneto-conductance are observed in function of magnetic field parallel to the nanowire axis. They reveal the carriers confinement within the nanowire and Landau orbits emergence in the transport direction. The coherent electron transport is jointly studied in these systems. It is highlighted by the observation of universal conductance fluctuations and electronic Fabry-Pérot oscillations. Finally the low-temperature photoconductivity measurement reveals the presence of Schottky barriers at the contacts and unexpected anisotropy according to the direction of linear polarization for InSB Zinc Blende nanowires.

<p>New acceptor moieties with extended conjugation have been developed  for further understanding of structure-property relationships in donor-acceptor type semiconducting polymers. These diketopyrrolopyrrole or isoindigo based conjugated polymers have been demonstrated as functional materials in organic field effect transistors, photoacoustic imaging and organic electrochemical transistors. With demonstrations of semiconducting molecular design, we hope to spark new research directions especially on deeper investigation of charge transport dependence on chemical structures, and new design strategies of acceptor moieties with extended conjugation could be applied for targeted applications.</p>