In this thesis, novel regimes of mode locking in quantum dot semiconductor laser diodes have been investigated by exploiting the unique features offered by quantum dots. Using an unconventional approach, the role of excited state transitions in the quantum dots was exploited as an additional degree of freedom for the mode locking of experimental quantum dot lasers. For the first time, passive mode locking via ground (1260nm) or excited state (1190nm) was demonstrated in a quantum dot laser. Picosecond pulses were generated at a repetition rate of 21GHz and 20.5GHz, for the ground and excited states respectively, with average powers in excess of 25mW. Switching between these two states in the mode-locking regime was achieved by changing the electrical biasing conditions, thus providing full control of the operating spectral band. A novel regime for mode locking in a quantum-dot laser was also investigated, where the simultaneous presence of cw emission in the excited-state band at high injection current levels, dramatically reduced the duration of the pulses generated via the ground state, whilst simultaneously boosting its peak power. This represents a radically different trend from the one typically observed in mode-locked lasers. From this investigation, it was concluded that the role of the excited state can not be neglected in the generation of ultrashort pulses from quantum-dot lasers. Stable passive mode locking of a quantum-dot laser over an extended temperature range (from 20ºC to 80ºC) was also demonstrated at relatively high output average powers. It was observed that the pulse duration and the spectral width decreased significantly as the temperature was increased up to 70ºC. The process of carrier escape in the absorber was identified as the main contributing factor that led to a decrease in the absorber recovery time as a function of increasing temperature which facilitated a decrease in the pulse durations. These results are shown to open the way for the ultimate deployment of ultra stable and uncooled mode-locked semiconductor diode lasers.

In this thesis we investigate a system of three tunnel-coupled quantum dots, arranged in a triangular geometry and attached to a single metallic conduction band, using both analytic and semi-analytic methods and the numerical renormalisation group technique. This is the simplest coupled quantum dot system to exhibit frustration. We study three different models of the triple quantum dot device: a mirror symmetric arrangement of dots in which only one dot is connected to the conduction band, a triple quantum dot system in which only one dot is connected to the conduction band without a plane of mirror symmetry and a mirror symmetric arrangement of quantum dots in which all three dots are coupled to the conduction band. We study these models over a wide range of parameter space, and in both the presence and absence of a magnetic field. Both antiferromagnetic and ferromagnetic Kondo effects are observed, and in all three models we find that the system contains at least two phases, and so a number of quantum phase transitions may be observed, associated in some cases with significant changes in the low temperature conductance through the triple quantum dot device. In addition to zero-field Kondo physics, a number of field induced Kondo effects are also observed. Both first order quantum phase transitions and Kosterlitz-Thouless phase transitions are observed. We use both symmetry arguments and low energy effective models which we derive to explain and understand both the position of and type of phase boundary that is observed in each case, and perturbative methods are used to accurately predict Kondo temperatures for a wide range of systems.

La pollution actuelle des effluents hospitaliers par des médicaments, nécessite le développement de nouvelles techniques de traitement, la photocatalyse étant l’une des plus efficaces pour remédier à ce type de pollution. Cependant, les oxydes métalliques utilisés pour la photocatalyse (TiO2, ZnO, …) ne sont activables que sous irradiation UV. L’association de ces oxydes à des Quantum Dots (QDs), crée une hétérojonction qui étend la zone d’activation du photocatalyseur vers les rayonnements visibles et diminue les recombinaisons des porteurs de charges. La première partie de ce travail décrit le développement d’un photocatalyseur activable sous irradiation solaire pour la dégradation du colorant Orange II. Nous avons d’abord caractérisé l’hétérojonction créée entre ZnO et les QDs CuInS2/ZnS (ZCIS) puis étudié leur efficacité photocatalytique, en regardant notamment leurs capacités à générer des espèces réactives de l’oxygène. Dans la seconde partie, nous avons évalué la photodégradation d’un agent anticancéreux, l’Ifosfamide, présent dans les effluents hospitaliers. Pour cela, des réacteurs fermés agités et des microréacteurs ont été utilisés. Dans les deux cas, l’Ifosfamide, ainsi que ses intermédiaires de dégradation, sont photodégradés efficacement par le catalyseur ZnO/ZCIS sous une irradiation solaire de faible intensité (5 mW/cm2). Dans le cas des microréacteurs, le dépôt du catalyseur dans le microcanal a été optimisé et sa stabilité évaluée. Les résultats montrent que le catalyseur ZnO/ZCIS est réutilisable cinq fois sans perte d’activité, témoignant d’une bonne recyclabilité, ce qui en fait un bon candidat pour des applications photocatalytiques / The pollution of hospital effluents by pharmaceutical drugs, requires the development of new treatment techniques. Among these processes, photocatalysis is one of the most efficient one and allows the remediation of this kind of pollution. However, metal oxides used for photocatalysis (TiO2, ZnO, …) can only be activated by UV light. The association of these oxides with quantum dots (QDs) creates an heterojunction, which not only allows to extend the activation spectrum of the photocatalyst to the visible region but also decreases the charge carriers recombinations. The first part of this work describes the development of a catalyst responding to solar light irradiation for the degradation of the Orange II dye. First, we characterized the heterojunction created between ZnO and the CuInS2/ZnS (ZCIS) QDs and evaluated their photocatalytic efficiency. This work was undertaken by evaluating the capacity of the ZnO/ZCIS catalyst to produce reactive oxygen species (ROS). In the second part, we studied the photodegradation of the antineoplastic agent Ifosfamide commonly found in hospital effluents. For this purpose, closed and agitated reactors but also microreactors were used. In both cases, Ifosfamide, and the compounds originating from its degradation, can be fully photodegraded under simulated light of weak intensity (5 mW/cm2) using the ZnO/ZCIS catalyst. In the case of microreactors, the deposition of the catalyst was optimized and its stability evaluated. Results obtained demonstrate that the ZnO/ZCIS catalyst can be reused, at least five times, without significant loss in activity, thus demonstrating its ability to be used in real photocatalytic applications

A tuberculose é uma doença infecto-contagiosa de proporções continentais. A situação é bastante complexa, pois a doença está diretamente associada às precárias condições sociais, à AIDS e à crescente multirresistência às drogas. Em 1993, a OMS a declarou em estado de emergência, recomendando a DOTS para seu controle. Assim, o presente estudo teve como objetivos identificar: as características pessoais, de condições de vida e de trabalho e de saúde-doença dos pacientes sob DOTS, matriculados em Unidades de Saúde da Família da Supervisão Técnica de Saúde de Vila Prudente/Sapopemba do Município de São Paulo; as potencialidades e os limites da estratégia DOTS sob o ponto de vista desses pacientes e como interpretam a adesão ao tratamento. Após aprovação em Comitê de Ética, foram coletados depoimentos de 11 pacientes de Unidades Básicas de Saúde da Família (UBSF) da Supervisão Técnica de Vila Prudente/ Sapopemba do MSP. O material empírico foi decodificado mediante técnica de análise de discurso e analisado à luz da Teoria da Determinação Social do Processo Saúde-Doença. Os resultados evidenciaram que a tuberculose é uma doença de cunho eminentemente social e ainda impregnada de estigma. Os achados em relação às características pessoais e sobre a manifestação clínica confirmam os dados de literatura. A doença causou mudanças no cotidiano dos sujeitos de estudo, principalmente no que refere ao relacionamento com outras pessoas. A DOTS, em geral, revelou-se como estratégia incorporada ao cotidiano dos sujeitos, e que possibilita o acesso mais facilitado aos serviços de saúde. Os aspectos limitantes da DOTS se devem à distância entre a unidade de saúde e o domicílio, assim como a exposição cotidiana às variações climáticas. A atitude dos profissionais em relação ao paciente contribui para a adesão ao tratamento e para a operacionalização da DOTS / The tuberculosis is a infectum-contagious illness of continental ratios, the third part of the world-wide population is infected and presents risk to develop the disease. The situation is sufficiently complex, therefore the illness directly is associated with the precarious social conditions, the AIDS and the increasing multiresistance to the drugs. In 1993, the OMS declared the tuberculosis in emergency state, recommending the DOTS for the control of the illness. The tuberculosis is a with priority problem of health in Brazil that, together with others 22 developing countries, lodges 80% of the world-wide cases of the illness. The present study it had as objective to identify the meanings, the potentialities and the limits of according to patient strategy DOTS of the local level of the City of São Paulo (MSP). 11 depositions of patients of Basic Units of Health of Família (UBSF) of the Supervision had been collected Technique of Cautious Village Sapopemba of the MSP. The empirical material was decoded by means of technique of analysis of analyzed speech and to the light of the Theory of the Social Determination of the Health-Illness Process. The results had evidenced that the tuberculosis is illness of an eminently social and impregnated matrix of stigma, did not have association of the signals and symptoms to the tuberculosis. The illness caused changes in the form to think or to locate itself ahead of the life, of the process health-illness, in the relationship with others and proper the daily one. The negative aspects to the DOTS if must to the limitation of its operation and the positive aspects to the DOTS confirm that the support strategy, but is not the sufficient for the adhesion. Visa what it makes the vulnerable people to exceed the potentials of increasing in search of the cure is the common things and the projects of life, that stimulate the capacity to surpass the challenges of the life

O estudo teve como principal objetivo analisar a adesão ao tratamento da tuberculose a partir da operacionalização da estratégia Tratamento Diretamente Supervisionado (DOTS), sob a perspectiva de profissionais de saúde que atuavam no controle da doença na região da Supervisão Técnica de Saúde do Butantã - SP. Trata-se de pesquisa qualitativa, baseada nos pressupostos da Teoria da Determinação Social do Processo Saúde-Doença e no conceito de Adesão. No período de maio a julho de 2006, foram entrevistados 22 profissionais de saúde das Unidades Básicas de Saúde (UBS) que desenvolviam a estratégia, incluindo os Coordenadores destas UBS. Foram resguardados os procedimentos éticos. Utilizou-se de técnica de análise de discurso apropriada para o tratamento dos depoimentos, que foram decompostos e analisados a partir das categorias analíticas: significados sobre o processo saúde-doença, a forma como se organiza o trabalho na unidade de saúde, os significados sobre a DOTS e sobre a adesão ao tratamento. Os resultados mostram que, de modo geral, os sujeitos do estudo consideram a tuberculose a partir da perspectiva da multicausalidade, ainda que com ênfase nos aspectos sociais. Identificaram-se atitudes que revelam estigma, decorrentes da falta de conhecimento a respeito da enfermidade e da forma como relacionar-se com o doente. Evidenciaram-se problemas na organização dos serviços, que se referem à trajetória percorrida pelos pacientes para ter acesso ao diagnóstico da tuberculose, além da ausência da busca de sintomáticos respiratórios. Quanto à DOTS, sua estruturação é diversa entre as UBS, no intuito de considerar as necessidades dos doentes no processo terapêutico, mas também devido à falta de conhecimentos dos profissionais, no que diz respeito à operacionalização da estratégia. A equipe de enfermagem é a que mais intensamente participa da DOTS. Para os profissionais de saúde, a estratégia permite manter atenção junto ao doente evitando o abandono do tratamento. Reitera-se, com algumas ressalvas, que a estratégia apresenta impacto na adesão, uma vez que possibilita a criação de vínculo entre o profissional de saúde e o doente. Além disso, verificou-se a necessidade de ampliar o entendimento a respeito do conceito de adesão, dado que não se restringe a um comportamento pessoal e volitivo / The main goal to this research was to analyze the compliance with tuberculosis therapy by use of the DOTS strategy – (Directly Observed Treatment), under the perspective of health professionals’ who carried out the control of tuberculosis in the Supervision of Health region of Butantã in the city of São Paulo, Brazil. This is a qualitative research based on the principles of the Social Determination of the Health-Disease Process Theory and of the concept of compliance. From May to July 2006, 22 Health professionals from the Health Basic Units (HBU), who developed the DOTS strategy, were interviewed, including their unit’s coordinators. Ethical procedures were applied to protect them. By using the appropriate speech analysis technique for the handling the collected material, the interviews were fragmented and analyzed according to analytic categories: understanding about the health-disease process, the way that the work is organized within the Health Unit, the meanings about the DOTS and about the compliance with treatment. The results show that, in general, the subjects of this study consider tuberculosis from the perspective of multicausality, even though with emphasis in the social aspects. Attitudes that reveal stigma were identified, derived from the lack of knowledge about the illness and the way of interacting with the patient. Some problems occurred in the organization of the services that refer to the path taken by the patients to having access to the diagnosis of tuberculosis, as well as the lack of search for respiratory symptomatic. With regards to the DOTS, its structure is diverse among the HBU, in the intention of considering the patients’ needs in the therapeutic process, but also due to the lack of knowledge of the professionals, when it comes to exercising the strategy. The nursing team is the one which participates most intensely in the DOTS. For the health professionals, the strategy allows them to pay close attention to the patient avoiding any dropping out of the treatment. It is certain, with some exceptions, that the strategy has some impact in its initiation, once it allows for a relationship to be created between the health professional and the patient. It was also verified that there is a need to further unfold the understanding of the concept of initiating this strategy, since it isn’t restricted to a personal behavior or to free will

Durant cette thèse nous avons, dans un premier temps, mis au point un protocole robuste pour quantifier l’échange de ligands à la surface de nano-objets, en prenant les quantum dots comme particules d’étude. Cette méthode se base sur la sensibilité de détection d’un élément radioactif, le tritium. Pour étudier l’échange de ligands, nous avons synthétisé de l’acide oléique tritié, dont l’équivalent non-marqué est un composé très couramment utilisé dans la chimie des QD. Nous avons élaboré un protocole permettant de déterminer la densité de ligands à la surface de quantum dots de type CdSe zinc blende par une méthode innovante. Par ailleurs, nous avons réalisé une étude permettant de déterminer la capacité qu’a un ligand à remplacer l’acide oléique présent à la surface des QD. On a ainsi obtenu une échelle des forces relatives de liaison de diverses fonctions chimiques suivant leur aptitude à déplacer l’acide oléique. Cette étude devrait permettre d’améliorer la compréhension et la mise au point des protocoles utilisés pour la préparation des QD. Dans un second temps, nous avons développé deux stratégies d’encapsulation de QD afin de les solubiliser dans l’eau avec comme objectif des applications en imagerie in vivo. Ces deux approches tentent de répondre aux nombreuses exigences liées à l’utilisation de QD en milieux biologiques. Dans cette optique, nous avons synthétisé des amphiphiles polymérisés d’une part et des amphiphiles perfluorés d’autre part. Des lots de QD, de type CdSe/CdS/ZnS émettant dans le visible, solubilisés selon ces deux stratégies ont été préparés et leur stabilité éprouvée dans plusieurs conditions. Nous avons ensuite appliqué l’encapsulation à des QD de type CuInS2/ZnS émettant dans le proche infrarouge. Des études préliminaire sont pu être réalisées par d’imagerie de fluorescence chez la souris afin d’évaluer in vivo ces nouvelles formulations de QD. / In this thesis we have, at first, developed a robust protocol to quantify the exchange of ligands on the surface of nano-objects, using quantum dots in this study. This method is based on the detection sensitivity of a radioactive element, tritium. To study the exchange of ligands, we synthesized tritiated oleic acid, whose unmarked equivalent is commonly used for the synthesis of QD. Thanks to an innovative method, we have developed a protocol to determine the density of ligands on the surface of zinc blende CdSe quantum dots. In addition, we conducted a study to determine the ability of a ligand to replace oleic acid on the surface of the QD. A scale of relative bond strengths of various chemical functions according to their ability to displace oleic acid has been obtained. This study is expected to improve the understanding and the development of protocols for the preparation of QD.In a second step, we developed two encapsulation strategies of QD in order to obtain colloidal stability in water with in vivo imaging applications as final aim. Both approaches attempt to answer the requirements for the use of QD in biological media. In this context, we have synthesized photopolymerisable amphiphilic compounds on the one hand and perfluorinated amphiphilic compounds on the other. Batches of CdSe/CdS/ZnS QD emitting in the visible, solubilized by these two strategies have been prepared and their stability tested in several conditions. We then applied the encapsulation strategy developed to CuInS2/ZnS QD emitting in the near infrared. Some preliminary studies have been carried out by in vivo fluorescence imaging in mice to assess these new QD formulations.

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Controlled patterning of light emitting diodes on semiconductors enables a vast variety of applications such as structured illumination, large-area flexible displays, integrated optoelectronic systems and micro-total analysis systems for real time biomedical screening. We have demonstrated a series of techniques of creating quantum-based (QD) patterned inorganic light emitting devices at room temperature on silicon (Si) substrate. In particular: (I) A combination of QDs self-assembly and microcontact printing techniques were developed to form the light emission monolayer. We expand the self-assembly method with the traditional Langmuir-Schaeffer technique to rapidly deposit monolayers of core: shell quantum dots on flat substrates. A uniform film of QDs self-assembled on water was transferred using hydrophobic polydimethylsiloxane stamps with various nano/micro-scale patterns, and was subsequently stamped. A metal oxide electron transport layer was co-sputtered onto the QDs. The structure was completed by an e-beam evaporating thin metal cathode. Multicolor light emission was observed on application of voltage across the device. (II) We also demonstrate the photolithographic patterning capability of a metal cathode for top emitting QDLEDs on Si substrates. Lithographic patterning technique enables site-controlled patterning and controlled feature size of the electrode with greater accuracy. The stability of inorganic silicon materials and metal oxide based diode structure offers excellent advantages to the device, with no significant damage observed during the patterning and etching steps. Efficient electrical excitation of QDs was demonstrated by both the methods described above. The technique was translated to create localized QD-based light sources for two applications: (1) Three-dimensional scanning probe tip structures for near field imaging. Combined topographic and optical images were acquired using this new class of “self-illuminating” probe in commercial NSOM. The emission wavelength can be tuned through quantum-size effect of QDs. (2) Multispectral excitation sources integrated with microfluidic channels for tumor cell analyses. We were able to detect the variation of sub-cellular features, such as the nucleus-to-cytoplasm ratio, to quantify the absorption at different wavelength upon the near-field illumination of individual tumor cells towards the determination of cancer developmental stage. / text

This thesis consists of two parts. In the first part, the properties of excess electrons in water clusters are studied via a hybrid quantum and classical mechanics method. The existence of the solvated electron in water was experimentally demonstrated long ago, and it is among the most interesting charged species. However, a satisfactory characterization of the water clusters has always been a challenge. In our simulation, we treat a region of the cluster nearest to the centroid of the excess electron distribution quantum mechanically, while the rest of the water molecules are treated classically. The binding energies of a localized excess electron are calculated in clusters with sizes ranging from 16 to 300. The density distributions of the excess electrons verify the existence of both surface localization mode and interior localization model. We studied the energetically favored localization modes depending on the sizes of the clusters and the transition point. In the second part, the energy spectra, spin configurations, and entanglement characteristics of a system of four electrons in lateral double quantum dots are investigated using exact diagonalization (EXD), as a function of interdot separation, applied magnetic field, and strength of interelectron repulsion. As a function of the magnetic field, the energy spectra exhibit a low-energy band consisting of a group of six states, with the number six being a consequence of the conservation of the total spin of the four electrons and the ensuing spin degeneracies. These six states appear to cross at a single value of the magnetic field, with the crossing point becoming sharper for larger interdot distances. As the strength of the Coulomb repulsion increases, the six states tend to become degenerate and a well defined energy gap separates them from the higher-in-energy excited states. The appearance of the low-energy band is a consequence of the formation of a Wigner supermolecule. Using the spin-resolved pair-correlation functions, one can map the EXD many-body wave functions onto the spin functions associated with the four localized electrons. The ability to determine associated spin functions enables investigations concerning entanglement properties of the system of four electrons.

Pour que l'énergie photovoltaïque devienne compétitive, les coûts de production doivent être baissés et l'efficacité des cellules augmentée. Les cellules solaires à base de nanocristaux semi-conducteurs constituent une approche prometteuse pour remplir ces objectifs combinant une mise en œuvre par voie liquide avec la possibilité d'ajuster précisément la largeur de bande interdite et les niveaux électroniques. Aujourd'hui, les rendements de conversion des cellules constituées de nanocristaux de sulfure de plomb approchent les 7%. Seulement, à cause des normes européennes destinées à l'affranchissement du plomb du fait de ses risques pour la santé et l'environnement, de nouveaux matériaux doivent être trouvés. Cette thèse concerne la synthèse de nouveaux types de nanocristaux semi-conducteurs et leur application dans des cellules solaires. La synthèse des nanocristaux de CuInSe2 et de SnS de taille et de forme contrôlées a été effectuée, notamment par des voies de synthèses reproductibles dont le passage à grande échelle est facilement possible. Une analyse approfondie de la structure des nanocristaux de SnS par spectroscopie Mössbauer a montré que ces nanocristaux avaient une forte tendance à s'oxyder, ce qui limite leur utilisation dans des dispositifs électroniques après exposition à l'air. La constitution de couches minces continues ayant de bonnes propriétés électriques a été effectuée par le dépôt contrôlé de nanocristaux ainsi que l'échange de leurs ligands de surface. En particulier, un nouveau type de ligand inorganique a été utilisé qui a montré une augmentation de la conductivité des films multiplié par quatre ordres de grandeurs par rapport aux ligands initiaux. Enfin, la préparation de cellules solaires basées sur ces couches minces de nanocristaux a montré des résultats encourageants et notamment un clair effet photovoltaïque lorsque le dépôt est effectué sous atmosphère inerte. / In order to be cost-effective, photovoltaic energy conversion needs to improve the solar cell efficiencies while decreasing the production costs. Nanocrystal based solar cells could fulfil these requirements through solution-processing, band gap and energy level engineering. PbS nanocrystal thin films already proved their potential for use as solar cell active materials with power conversion efficiencies approaching 7%. However, since lead based compounds are not compatible with European regulations and present high risks for health and environment, semiconductor nanocrystals of alternative materials have to be developed. This thesis focuses on novel types of semiconductor nanocrystals and their application in photovoltaics. The first part of the study deals with the synthesis of size- and shape-controlled CuInSe2 and SnS nanocrystals. An in-depth investigation of the structure of SnS nanocrystals using Mössbauer spectroscopy revealed their high oxidation sensitivity, which limits their usability in optoelectronic devices after air exposure. The second part deals with the thin film preparation and the surface ligand exchange of the obtained nanocrystals. Using a fully inorganic nanocrystal-surface ligand system, the deposited films exhibited a current density improved by four orders of magnitude as compared to the initial ligands. Finally, solar cell devices based on nanocrystal thin films were fabricated, which showed encouraging results with a clear photovoltaic effect when processed under inert atmosphere.