Es werden die exzitonischen Eigenschaften von Halbleiter-Quantengräben im Magnetfeld theoretisch untersucht. Unter Benutzung der Enveloppen-Näherung wird der Hamilton-Operator des Exzitons aufgestellt. Ein allgemeines Theorem für die diamagnetische Verschiebung (DMV) des exzitonischen Grundzustands wird abgeleitet. Im ersten Teil werden Effekte der Unordnung berücksichtigt. Die numerische Ergebnisse zeigen, daß die DMV ein Maß für die Lokalisierung der Wellenfunktion ist. Einzelne Exzitonzustände, wie sie für optische Nahfeldexperimente relevant sind, zeigen eine breite Verteilung der DMV-Werte, wobei der Mittelwert mit der Energie anwächst (abnehmende Lokalisierung). Die Absorptions- und Photolumineszenz-Spektren im Fernfeld werden mit dem Magnetfeld breiter. Unter Ausnutzung der strukturellen Information über die lokale chemische Zusammensetzung einer gegebenen Probe werden die statistischen Eigenschaften der Unordnung in einem realen Quantengraben analysiert. Das ermöglicht die numerische Erzeugung neuer Unordnungspotentiale, die dann für die Simulation der optischen Eigenschaften wie DMV-Statistik und Photolumineszenzspektren genutzt werden. Der Vergleich mit den experimentellen Daten für verschiedene Temperaturen zeigt eine sehr gute Übereinstimmung. Der zweite Teil dieser Dissertation beschäftigt sich mit Quantenpunkten und Quantenringen, die in einem Quantengraben eingebettet sind, und konzentriert sich auf den exzitonischen Aharonov-Bohm Effekt. Der persistente Strom und die Magnetisierung werden berechnet. Für zirkuläre Symmetrie wird der enge Zusammenhang zwischen der oszillatorischen Komponente der Exziton-Energie und dem persistenten Strom aufgezeigt. Für nichtzirkuläre Ringe sind die Oszillationen ebenfalls beobachtbar, jedoch mit kleinerer Amplitude. Eine Untersuchung der Exzitonenkinetik zeigt die wichtige Rolle nichtradiativer Prozesse auf und setzt Grenzen für die Beobachtbarkeit der Oszillationen und für die Auslöschung der Photolumineszenz. / Excitonic properties of semiconductor quantum wells (QWs) with applied magnetic field are investigated theoretically. Using the envelope function approximation, the exciton Hamiltonian is constructed. A general theorem for the diamagnetic shift (DMS) of the lowest exciton energy is derived. In a first part, disorder is taken into account. The numerical results show that the DMS is a measure of wave function localization. Individual exciton states as relevant for optical near-field experiments show a broad distribution of DMS values while its average value increases with energy (decreasing localization). Far-field absorption and photoluminescence spectra become wider with increasing magnetic field. Using structural information on the local chemical composition of a given sample, the statistical properties of the disorder in a real QW have been analyzed. This allowed to generate new disorder potentials as input for the simulation of DMS statistics and photoluminescence spectra. Their comparison with experimental data at different temperatures shows very good agreement. The second part of the thesis deals with quantum dots and rings embedded in the QW, focusing on the exciton Aharonov-Bohm effect. Persistent current and magnetization are evaluated. For circular symmetry, a close relation between the oscillatory component of the exciton energy and the persistent current is revealed. For non-circular rings, oscillations can be observed too but with lower amplitude. A study of the exciton kinetics points to the important role of non-radiative processes, and sets limits for the experimental observability of energy oscillations and photoluminescence quenching.

Nesse trabalho foram estudados os compostos intermetalicos do tipo RAg (R = Nd, Gd e Ho) por calculos teoricos desenvolvidos dentro do formalismo da Teoria do Funcional Densidade (DFT). O metodo APW+lo (Augmented Planes Waves + lo- cal orbitals) foi aplicado para resolver a equacao de Kohn-Sham e a Aproximacao do Gradiente Generalizado (GGA) usada para tratar de forma aproximada o potencial de troca-correlacao. O codigo computacional utilizado foi o WIEN2k. As atividades foram focalizadas em duas frentes. Numa delas, determinou-se a fase magnetica do estado fundamental dos compos- tos HoAg e NdAg. Para isso, simulou-se as 4 estruturas magneticas possiveis (para as celulas cristalinas cubicas) desses dois sistemas (uma ferromagnetica (0,0,0) e as antifer-romagneticas: (0,0,¼), (¼,¼,0) e (¼,¼,¼)) e com a confeccao de gra¯cos de energia das celulas cristalinas dessas estruturas magneticas pela variacao dos volumes de tais celulas, chegou-se na estrutura magnetica (¼,¼,0) como a mais provavel para o estado fundamental magnetico de ambos os compostos. Tambem observou-se que o sistema de NdAg apre- senta uma pequena diferenca entre as energias das estruturas antiferromagnetica (¼,¼,0) e ferromagnetica. Creditou-se a esse efeito a explicacao de encontrar-se na literatura re- sultados experimentais diferentes para a estrutura magnetica do composto de NdAg puro e dopado com o atomo de 140Ce (entrando no sitio do Nd). Acredita-se que a dopagem do NdAg com o atomo de 140Ce (em uma porcao reduzida), gera alteracao no sinal da integral de troca (acoplamento RKKY), mudando-o de positivo para negativo, e isso implica na modficacao da fase magnetica do estado fundamental, passando da estrutura (¼,¼,0) µa 0,0,0). Assim, com a informacao anterior da estrutura magnetica do composto de NdAg quando dopado com o atomo de 140Ce, entrou-se na segunda etapa do estudo. Nela, fez-se os calculos das estruturas eletronicas usando a aproximacao de supercelulas nos compostos de GdAg e NdAg dopados com o atomo de Ce, garantindo que esse substituisse um atomo de terra rara nas supercelulas cristalinas montadas para determinar no Ce o campo hiperfino magnetico e suas componentes geradoras. Os compostos de GdAg e NdAg (dopados com Ce), respectivamente, tiveram suas celulas cristalinas montadas ferromagnetica e antiferromagneticamente. Utilizou-se a polarizacao orbital (DFT+U) nos eletrons da camada 4f das terras raras (excluindo-se o atomo de Gd que nao apresenta momento angular). Dessa forma, em ambos os sistemas foi possivel fazer varias simulacoes, nas quais a camada 4f do atomo de Ce foi populada de maneiras diferentes, afim de se obter varios valores de momento angular e com isso diversos resultados de campo hiperfino orbital foram conseguidos; assim, automaticamente o campo magnetico hiperfino tambem assumiu diferentes valores. Escolheu-se os sub-estados da camada 4f do Ce para serem simulados por meio da regra de Hund. Como esperado o campo hiperfino magnetico orbital gerado na camada 4f e a principal componente do campo hiper¯no total no atomo de Ce e ele apresenta sinal contrario µa componente de contato. Apesar dos resultados teoricos do campo hiperfino magnetico terem consideravel discrepancia dos resultados experimentais, pode-se verificar que o unico eletron da camada 4f do atomo de Ce (nos dois compostos) possivelmente esta em um dos seguintes sub-estados da camada 4f: ml = ¡2, ml = ¡1 ou ainda uma combinacao dos dois. / In this work the magnetic hyper¯ne ¯eld acting on Ce atoms substituting the rare-earths in RAg compounds (R = Gd e Nd) was studied by means of ¯rst-principles electronic structure calculations. The employed method was the Augmented Plane Waves plus local orbitals (APW+lo), embodied in the WIEN2k program, within the framework of the Density Functional Theory (DFT) and with the Generalized Gradient Approximation (GGA) for the exchange and correlation potential. The super-cell approach was utilized in order to simulate for the Ce atoms acting as impurities in the RAg matrix. In order to improve for correlation e®ects within the 4f shells, a Hubbard term was added to the DFT hamiltonian, within a procedure called GGA+U. It was found that the magnetic hyper¯ne ¯eld (MHF) generated by the Ce 4f electron is the main component of the total MHF and that the Ce 4f ground state level is probably a combination of the ml = ¡2 and ml = ¡1 sub-levels. In addition, the ground-state magnetic structure was determined for HoAg and NdAg by observing the behavior of the total energy as a function of the lattice volume v for several possible magnetic ordering in these compounds, namelly, ferromagnetic, and the (0,0,¼), (¼,¼,0) and (¼,¼,¼) types of anti-ferromagnetic ordering of rare-earth atoms. It was found that the ground-state magnetic structure is anti-ferromagnetic of type (¼,¼,0) for both, the HoAg and NdAg compounds. The energy di®erence of the ferromag-netic and antiferromagnetic ordering is very small in the case of the NdAg compound.

Os campos magnéticos estáticos interferem com o sistema nervoso central lesado, modificando a atividade de diferentes estruturas e recuperando o comportamento afetado pela lesão. Esse trabalho tem por objetivo investigar os efeitos dos polos magnéticos em ratos Wistar saudáveis e as repercussões comportamentais no Labirinto em Cruz Elevado (LCE) induzidas por pentilenotetrazol (PTZ) e por Alprazolam (ALP) sob o efeito da estimulação magnética. EXPERIMENTO I - Foram utilizados 107 ratos albinos Wistar, machos, pesando entre 270 - 300g. Após quatro dias da implantação de um magneto (3200 Gauss) no crânio dos animais, esses foram submetidos à avaliação comportamental no LCE. Grupos injetados receberam, via intraperitoneal, 30 mg/kg de PTZ ou salina. Os dados obtidos foram analisados por ANOVA, as significâncias foram evidenciadas pelo pós-teste de Holm Sidak com valor de P significativo<0,05. Observamos diminuição no número de entradas nos braços abertos nos grupos PN, PTZ e SMPTZ em relação ao grupo C, e um aumento nas entradas do grupo PSPTZ sobre os grupos PTZ e SMPTZ (F6, 158= 1,91). Análise etológica revelou um aumento da apresentação do comportamento espreitar nos grupos PTZ, SMPTZ, PNPTZ, PSPTZ (F6, 79= 3,51), diminuição na apresentação dos comportamentos mergulho de cabeça (F6, 79= 2,40) e levantamentos (F6, 79= 17,64) nos grupos PN, PS, PTZ, SMPTZ, PNPTZ e PSPTZ em relação ao C. EXPERIMENTO II - Participaram 79 animais mantidos nas mesmas condições experimentais que no experimento I, injetados com Alprazolam (1mg/kg - intraperitoneal) ou salina. Observamos um aumento no número de entradas nos braços abertos nos grupos ALP e SMALP em relação ao grupo C (F6, 144= 3,53). A porcentagem de entradas nos braços abertos foi maior nos grupos ALP e SMALP em relação ao C (F6, 72= 2,41), e a porcentagem de tempo nos braços abertos foi maior no PNALP, comparado com o C (F6, 72= 3,95). A análise etológica revelou um aumento na frequência dos comportamentos mergulho de cabeça (F6, 72= 10,79) e exploração da extremidade final (F6, 72= 6,00) nos grupos ALP, SMALP e PNALP em relação ao C. Para o comportamento de levantamentos (F6, 72= 4,71) também observamos um aumento da frequência desse comportamento para os grupos ALP, SMALP e PSALP em relação ao C. No experimento I, o polo Sul conseguiu antagonizar o efeito do PTZ, na variável espaço-temporal entradas nos braços abertos, além disso, a estimulação magnética polo Norte, mimetizou o efeito do PTZ. No experimento II, ambos os polos magnéticos antagonizaram o efeito ALP na variável espaço-temporal entradas nos braços abertos. As variáveis etológicas também revelaram um antagonismo da resposta ALP, pelo polo Norte e pelo polo Sul. Dessa maneira, esse trabalho mostra através da análise comportamental no LCE que os campos magnéticos podem interferir de maneira distinta com as modificações no comportamento de ratos injetados com PTZ ou ALP / Static magnetic fields interfere with the injured central nervous system, modifying the activity of different structures and recovering the behavior affected by the lesion. The objective of this study was to investigate the effects of magnetic poles on healthy Wistar rats and the behavioral repercussions of the Penzolenotetrazole (PTZ) and Alprazolam (ALP) induction on the Elevated Plus-Maze (EPM) under the effect of magnetic stimulation. EXPERIMENT I - 107 male Wistar rats weighing between 270 and 300 g were used. After four days of implantation of a magneto (3200 Gauss) in the cranium of the animals, they were submitted to behavioral evaluation in the EPM. Injected groups received intraperitoneally 30 mg / kg of PTZ or saline. The data were analyzed by ANOVA, the significance was evidenced by the Holm Sidak post-hoc with a significant P value <0.05. We observed a decrease in the number of entrance open arms in the PN, PTZ and SMPTZ groups compared to group C, and an increase in the PSPTZ group on PTZ and SMPTZ groups (F6, 158 = 1.91). Ethological analysis showed an increase in the peeking out behavior in the PTZ, SMPTZ, PNPTZ, PSPTZ groups (F6, 79 = 3.51) and a decrease in the performance of the head dipping behavior (F6, 79= 2.40), and of rearing in PS, PTZ, SMPTZ, PNPTZ and PSPTZ in relation to C (F6, 79= 17.64). EXPERIMENT II - Participated 79 animals maintained in the same experimental conditions as in experiment I, injected with Alprazolam (1mg / kg - intraperitoneal) or saline. We observed an increase in the number of entrance into open arms in the ALP and SMALP groups compared to group C (F6, 144 = 3.53). And the percentage of open arms entries was higher in the ALP and SMALP groups than C (F6, 72 = 2.41), and the percentage of open arms time spented was higher in PNALP, compared to C (F6, 72 = 3.95). The ethological analysis revealed an increase in the frequency of head dipping behaviors (F6, 72 = 10.79) and end-arm activity (F6, 72 = 6.00) in the groups ALP, SMALP and PNALP in relation to C. Already for the rearing (F6, 72 = 4.71), we also observed an increase in the frequency of this behavior for the ALP, SMALP and PSALP groups in relation to C. In the experiment I, the South pole was able to antagonize the PTZ effect, as reported for the space-time variable in the open arms, besides the North pole magnetic stimulation, mimics the PTZ effect. In the experiment II, both magnetic poles antagonize the ALP effect in the space-time variable in the open arms. The ethological variables also revealed an antagonism of the ALP response, by the North and South poles. Thus, this work shows through the behavioral analysis in the EPM that the magnetic fields can interfere in a different way with the modifications in the behavior of injected rats with PTZ or ALP

The detection and location of faults on power transmission lines is essential to the protection and maintenance of a power system. Most methods of fault detection and location rely on measurements of electrical quantities provided by current and voltage transformers. These transformers can be expensive and require physical contact with the monitored high voltage equipment. In this work, current transformers were replaced by magnetic field sensing coils. Such coils can be located remotely from substations and switching stations and do not require physical contact with the conductors. Rather than observing each individual conductor, the use of the magnetic field sensors allows the monitoring of the transmission line condition using a collective quantity. This study explores the use of the magnetic field sensors as an alternative measurement device for fault detection and location.

Les effets de la force magnétique orthogonale (MF) sur le processus d'électropolymérisation de l'aniline dans une solution d’acide chlorhydrique ont été étudiés.La voltammétrie cyclique (CV), la chronoampérométrie et la spectroscopie d'impédance électrochimique (EIS), ont été utilisées pour examiner le processus de transfert de masse et le processus de réaction électrochimique. Différentes techniques, telles que la microscopie électronique à balayage (MEB), la microscopie à force atomique (AFM) et la diffraction à rayons X (XRD) ont été utilisées pour caractériser les revêtements préparés.Les résultats montrent que la vitesse de dépôt augmente avec la force magnétique et la concentration du monomère d’aniline en raison de la convection magnétique et les propriétés magnétiques du radical.L’imagerie MEB et l'analyse topologique ont révélé que, sous MF les films sont essentiellement composés de gonflement des nanofibres et des ilots des polymères qui sont bien répartis sur la surface. Les études de diffraction à rayons X révèlent une amélioration de la cristallinité des couches, sans orientations préférentielles.Mots clés: polymère, polyaniline, aniline, champ magnétique, électropolymerisation, impédance électrochimique, DFT, susceptibilité magnétique. / The effects of static orthogonal magnetic force (MF) on the electropolymerization process of aniline from hydrochloric bath have been investigated. Cyclic voltammetry (CV), Chronoamperometry and electrochemical impedance spectroscopy (EIS) techniques were used to examine the mass transfer process and electrochemical reaction process. Different techniques, such as Scanning Electron Microscopy (SEM), Atomic Force Microscopy (AFM) and X-ray Diffraction (XRD) were employed to characterize the prepared coatings. The results show that deposit rate increased with increasing MF and aniline monomer concentration due to the magneto-convection involving the mass transport and radical magnetic properties. SEM imagery and topological analysis revealed that under MF the films are essentially composed of swelling of the nanofibers and ilots of polymers that are well distributed on the surface. The XRD studies reveal an enhancement of the crystallinity of the coatings without any preferential orientations.Keywords: Polymers, Polyaniline, aniline, Magnetic fiels, Electropolymerization, electrochemical impedance, DFT, magnetic susceptibility .

Jusqu'à présent, les modifications de la réplication de l'ADN entre cellules normales et cancéreuses ont été peu étudiées. Dans ce travail, nous avons utilisé le séquençage des fragments d'Okazaki, une technique récemment développée au laboratoire, pour déterminer la directionalité des fourches de réplication dans plusieurs lymphomes de Burkitt (LB), qui surexpriment l'oncoprotéine Myc à la suite de translocations chromosomiques spécifiques, ainsi que dans des lignées lymphoblastoides contrôles (LLC) et dans des léiomyosarcomes (LMS). Les profils de directionalité des fourches de réplication permettent de déduire la localisation et l'efficacité des sites d'initiation et de terminaison de la réplication le long du génome. Nous avons observé de nombreuses (~2000) différences de zones d'initiation entre les lignées Raji (LB) et GM06990 (LLC) ainsi qu'entre les lignées BL 79 et IARC385, une paire LB/LLC provenant d'un même patient. Nous avons détecté un nombre comparable de différences en comparant deux à deux les lignées étudiées. Cependant, les profils de BL79 et de Raji (deux LB) sont un peu plus proches l'un de l'autre que de la lignée contrôle GM06990. Ceci suggère l'existence de changements de la réplication récurrents dans les lignées LB. L'importance des différences observées entre les lignées IARC385 et GM06990 indique de façon surprenante une grande variabilité entre les LLC normales, provenant de différents individus. De façon intéressante, de nombreuses différences observées entre les lignées LB et LLC sont associées à des changements de l'expression des gènes ou de la liaison de l'oncoprotéine Myc. La comparaison des profils des deux LMS avec tous les profils disponibles au laboratoire montre que c'est à celui de fibroblastes normaux (IMR90) qu'ils ressemblent le plus. Ceci suggère que les cellules de tumeurs musculaires lisses auraient subi une transformation fibroblastique au cours de la tumorigénèse. Des données récentes suggèrent que les champs magnétiques peuvent perturber certains processus cellulaires comme l'assemblage du cytosquelette. Nous avons utilisé le séquençage de fragment d'Okazaki pour rechercher d'éventuels effets d'un champ magnétique sur la réplication de l'ADN chez la levure. Aucun effet du champ magnétique sur la directionalité des fourches de réplication n'a été détecté. / Changes in DNA replication profiles between cancer and normal cells have been poorly explored. In this work, sequencing of Okazaki fragments, a novel methodology developed in the laboratory, was used to determine replication fork directionality (RFD) in several Burkitt's lymphomas (BL), which overexpress the Myc oncoprotein due to specific chromosomal translocations, and control normal lymphoblastoid cell lines (LCL), and in leiomyosarcomas (LMC). RFD profiles allow to infer the location and efficiency of replication initiation and termination sites genome-wide. A larger number (~2000) of differences in replication initiation zones were observed genome-wide between Raji (BL) and GM06990 (LCL), and between BL79 and IAR385, a BL / LCL pair of cell lines established from a single patient. Comparably large numbers of changes were slightly more similar to each other than to GM06990. This suggests the occurrence of some recurrent replication changes in BL cell lines. The large number of changes observed between IARC385 and GM06990 also indicates an unexpectedly large variation between normal LCLs of different individuals. Interestingly, many changes in RFD profiles between BLs and and LCLs are associated with cell-type specific gene expression and differential binding of the Myc oncoprotein. Comparison of the two LMS profiles with all RFD profiles available in the laboratory reveals that they most resemble normal fibroblasts (IMR90). This suggests that the smooth muscle cancer cells might have undergone a fibroblastic transformation during tumorigenesis. Magnetic fields have been reported to perturb cellular processes such as cytoskeleton assembly. Sequencing of Okazaki fragments was used in a preliminary investigation of the possible effects of magnetic fields on DNA replication in yeast cells. No effect of magnetic fields on replication fork directionality were observed.

Dois modelos descrevendo sistemas magnéticos modulados são estudados na presença de um campo magnético. Na primeira parte consideramos um modelo de Ising com interações competitivas numa única direção espacial (modelo ANNNI). A superfície crítica, a linha tricrítica, a estrutura das fases moduladas, e os diagramas de fases são determinados na aproximação de campo médio. O comportamento crítico e tricrítico é analisado através do método de Grupo de Renormalização. Na segunda parte estudamos um modelo adequado à descrição do composto MnP. Cálculos realizados na aproximação de campo médio e através do método de Grupo de Renormalização contribuem para esclarecer os resultados experimentais acerca do ponto de Lifshitz observado neste composto. / Two models describing modulated magnetic systems are studied in the presence of a magnetic field. The first part is dedicated to the study of an Ising model with competing interactions along one of the spatial directions (ANNNI model). The critical surface, the tricritical line, the structure of the modulated phases, and the phase diagrams are determined in the mean field approximation. The critical and the tricritical behaviour is analised by the Renormalization Group method. The second part is concerned with a model suitable for the description of the compound MnP. Calculations carried out in the mean field approximation and through the Renormalization Group method provide a better understanding of the experimental results on the Lifshitz point observed in this compound.

Atualmente, a intensidade de campo elétrico, campo magnético e campo eletromagnético é um fator determinante não só para a implantação de novas instalações, mas também, para as instalações existentes no sistema elétrico. Apesar de não existir nenhum estudo conclusivo que comprove a evidência direta entre a exposição a estes campos e os efeitos nocivos na saúde das pessoas, muitos países, inclusive o Brasil, definiram em suas legislações limites básicos à exposição de campos elétrico e magnético provenientes dos sistemas elétricos. Este trabalho tem como objetivo contribuir para análise de campo magnético de linhas subterrâneas de alta tensão existentes ou linhas em fase inicial de projeto, visando atender os limites de exposição vigentes na legislação local. Nele é apresentada a metodologia de cálculo de campo magnético baseada na Lei de Biot-Savart e no princípio da superposição. Estudos analíticos para verificação da influência dos parâmetros de instalação e elétricos de linhas sobre o campo magnético são apresentados para linhas subterrâneas de alta tensão compostas por um e dois circuitos com diferentes tipos de instalação e aterramentos. Comparações entre valores analíticos e valores de medições de campo magnético de linhas subterrâneas de alta tensão existentes em operação também são abordadas neste trabalho. As principais técnicas de mitigação de campo magnético utilizadas em linhas subterrâneas de alta tensão, tais como técnicas de compensação envolvendo laços de cabos e técnicas de blindagens com materiais metálicos externos aos cabos, também são apresentadas. Devido ao campo elétrico externo ao cabo isolado ser praticamente zero, assuntos referentes a este campo não são abordados neste trabalho. Por simplicidade, campo magnético refere-se à densidade de fluxo magnético neste documento. / Nowadays, the intensity of electric field, magnetic field and electromagnetic field is a determining factor, not only for implantation of new installations, but also for existing installations in the power system. Although no exist conclusive study that proves the direct evidence between exposure to these fields and adverse effects on human health, many countries, including Brazil, have defined in their laws basic limits for exposure to electric and magnetic fields produced by the electric system. This work aims to contribute to analysis of magnetic field for both existing high voltage underground lines and lines in initial stage of project, aiming the actual exposure limits of the local legislation. In it, is shown the magnetic field calculation methodology based on the Biot-Savart\'s law and the superposition principle. Analytical studies to verify the influence of installation and electrical parameters of lines on the magnetic field are presented for high voltage underground lines consist of one and two circuits with different types of installation and earthing. Comparisons between analytical and measurement values of magnetic field of existing high voltage underground lines in operation are also addressed in this work. The main mitigation techniques of magnetic field used in high voltage underground lines, such as compensation techniques by loop of cables and shielding by metallic materials, are also presented. Due the electric field outside the insulated cable be practically zero, issues related to the electric field are not addressed in this work. For simplicity, the magnetic field refers to the magnetic flux density in this document.

Organic semiconductors (OSCs) have already been shown to have great potential to play an important role in the future of clean energy generation (organic solar cells) and provide energy efficient lighting (organic light-emitting diodes, OLED). Prior research has found that the light-emission efficiency of OLED is severely limited by the magnetic state (technically the spin-configuration) of the light-emission process. In this thesis, we work on the processes using external magnetic fields that can overcome these magnetic limitations. A major focus of this research is to enhance the performance of OLED, while at the same time to unravel the scientific mechanisms by which magnetic fields act on OSCs devices. Thermally activated delayed fluorescence (TADF) is a next-generation OLED emission technology which enables nearly 100% light-emission efficiency without using heavy precious metals. TADF characteristics depend on the probability of reverse intersystem crossing (RISC) from the triplet excited states (T1) to singlet excited states (S1). The conversion (T1 to S1) process depends strongly on spin dynamics, thus we predict a dramatic magnetic field effects (MFEs) in such TADF OLED devices. In subsequent experiments we observed that changes in TADF devices due to various forms of electrical stress can lead to enormous increases in magnetic field effects (MFEs) on the current (> 1400%) and electroluminescence (> 4000%). Our work provides a flexible and inexpensive pathway towards magnetic functionality and field sensitivity in current organic devices. Such OLED pave the way for novel magnetic sensitive OSCs devices with integrated optical, electronic and magnetic characteristics. Organic magnetoresistance (OMAR) has been observed to alter the current and efficiency of OLED without any ferromagnetic components. Here we utilizes slight alterations to the device properties, the addition of a radical-doped functional layer, in which the spin-relaxing effects of localized nuclear spins and electronic spins interfere, to address the assumption about the importance of the hyperfine interaction and to attempt to differentiate between the different models for OMAR. A feature where the magnitude of OMAR exhibits a plateau over a wide range of doping fraction was observed at all temperatures investigated. This phenomenon is well explained by a theory in which a single dopant spin strongly interacts, by exchange, with one of the bottleneck sites. A similar can be used to explain the efficiency increases observed in organic solar cells for certain doping fractions.

Recently, technological advancement and the promise of next-generation devices have created an overwhelming push for the continued miniaturization of active systems to the micro- and nanometer scale. In this regime, traditional mechanical systems are largely inaccessible and as a result new active or stimuli-responsive materials are required. The work presented in this dissertation provides an understanding of the responsive nature of polymer and biopolymer interfaces especially in contact with metal nanoparticles. This understanding was utilized in conjunction with top-down template-based and self-assembly fabrication strategies to create hybrid protein based films and active polymer-metal hybrids that exhibit large and well-defined modulation of mechanical and optical properties. These materials processing developments represent advancement in the current state of the art specifically in three major areas: 1. template-based top-down control of protein chain conformation, 2. high-throughput synthesis and assembly of strongly coupled plasmonic nanoparticles with modulated optical properties (both near- and far-field), 3. field-assisted assembly of highly mobile and non-close packed magnetic nanorods with capabilities for rapid actuation.