In this thesis we examine the feasibility of developing a white light source capable of producing colors between 2500 and 7500 Kelvin on the black-body radiator spectrum by simply adjusting amperage to a blue and ultraviolet (UV) light emitting diode (LED). The purpose of a lighting source of this nature is to better replicate daylight inside a building at a given time of day. This study analyzes the proposed light source using a 385 nm UV LED, a 457 nm blue LED, a 479 nm blue LED, a 562 nm peak cerium doped yttrium aluminum garnet (YAG:Ce) phosphor, and a 647 nm peak selenium doped zinc sulfide (ZnS:Se) phosphor. Our approach to this study initially examined optical performance of yellow-emitting phosphor (YAG:Ce) positioned at specific distances above a blue LED using polydimethylsiloxane (PDMS) as a substrate. An understanding of how phosphor concentration within the PDMS, the thickness of the PDMS, and how substrate distance from the LED die affected light intensity and color values (determined quantitatively by utilizing the 1931 CIE 2° Standard Observer) enabled equations to be developed for various lens designs to efficiently produce white light using a 457 nm peak wavelength LED. The combination of two luminescent sources (457 nm LED and YAG:Ce) provided a linear trend on the 1931 CIE diagram which required a red illumination source to obtain Kelvin values from 2500 to 7500. Red-emitting phosphor (ZnS:Se), selected to compliment the system, was dispersed with YAG:Ce throughout PDMS where they were stimulated with a blue LED thereby enabling all desired Kelvin values with differing concentration lenses. Stimulating ZnS:Se with the addition of a UV LED did not provide the ability to change the color value of the set up to the degree required. Many other factors resulted in the decision to remove the UV LED contribution from the multi-Kelvin light source design. The final design incorporated a combination of ZnS:Se and YAG:Ce stimulated with a blue LED to obtain a 2500 Kelvin value. A separate blue LED provides the means to obtain 7500 Kelvin light and the other color values in between, with a linear approximation, by adjusting the amperages of both LEDs. In addition to investigating the feasibility of obtaining the Kelvin values from 2500 to 7500, this thesis also examined the problem of ZnS:Se’s inability to cure in PDMS and a method to create a lens shape to provide equal color values at all points above a phosphor converted LED source. ZnS:Se was found to be curable in PDMS if first coated with a low viscosity silicon oil prior to dispersion within PDMS. The lens configuration consists of phosphors equally distributed in PDMS and cured in the shape of a Gaussian distribution unique to multiple factors in LED-based white light design.

Recently, as a promising lighting source, light-emitting diodes (LEDs) have become more and more attractive and have great opportunity to replace traditional lighting sources - incandescent, fluorescent and HID because of the advantages such as high luminous efficacy, long lifetime, quick on/off time, wide color gamut, eco-friendly etc. Based on the research from U.S. Department of Energy, over 30% of total electric consumption in U.S. each year is for lighting, 75% of which are for indoor lighting (including both residential and commercial buildings). In the indoor LED lighting application, to provide multiple current source outputs for multiple LED strings, traditional solutions usually adopt a two-stage structure, which is complicated and cost-ineffective. How to design a simple, low-cost and efficient LED driver with multiple current source outputs is in great demand and really challenging. In this thesis, a single-stage multi-channel constant current (MC3) LED driver structure has been proposed. Multiple transformer structure is utilized to provide multiple current source outputs. The current control scheme is also simple - only one LED string current is sensed and controlled; other strings' currents are cross regulated. Firstly, a PWM half bridge topology is chosen to implement the proposed single-stage MC3 LED driver concept. In order to analyze the current cross regulation, a general model is derived. The circuit has been simulated under various LED load conditions to verify its good current sharing capability. In order to further improve efficiency, simplify the driver's complexity and reduce cost, a LLC resonant topology is also investigated. LLC current gain characteristic has been derived by considering LED's i-v character and a design procedure is developed. A 100 kHz, 200 W, 4-string MC3 LLC LED driver is designed and tested. The experimental results show that the driver can maintain constant current output within the whole input and output variations, achieve good efficiency and realize current sharing under both balanced and unbalanced LED conditions. The dimming function can also be realized through frequency modulation method and burst mode control method. As a conclusion, a single-stage MC3 LED driver concept is proposed and implemented with two topologies. The proposed idea provides a simple, low-cost and efficient solution for indoor LED lighting application with multiple LED string configuration. It also has good current sharing capability and robustness to LED forward voltage variations or short failures. / Master of Science

Optimising illumination is essential for optimising the growth of phototrophic cells and their production of desired metabolites and/or biomass. This requires appropriate modulation of light and other key inputs and continuous online monitoring of their metabolic activities. Powerful non-invasive systems for cultivating heterotrophic organisms include shake flasks in online monitoring units, but they are rarely used for phototrophs because they lack the appropriate illumination design and necessary illuminatory power. This study presents the design and characterisation of a photosynthetic shake flask unit, illuminated from below by warm white light-emitting diodes with variable light intensities up to 2300 μmol m-2 s-1. The photosynthetic unit was successfully used, in combination with online monitoring of oxygen production, to cultivate Arthrospira platensis. In phototrophic growth under continuous light and a 16 h light/8 h dark cycle (light intensity: 180 μmol m-2 s-1), the oxygen transfer rate and biomass-related oxygen production were - 1.5 mmol L-1 h-1 and 0.18 mmol O2 gx-1 h-1, respectively. The maximum specific growth rate was 0.058 h-1, during the exponential growth phase, after which the biomass concentration reached 0.75 g L-1.

Submitted by Rosivalda Pereira (mrs.pereira@ufma.br) on 2017-10-02T20:17:04Z No. of bitstreams: 1 ThiagoSantos.pdf: 1103502 bytes, checksum: 16ad7405a0ab31d83423293c43110ee8 (MD5) / Made available in DSpace on 2017-10-02T20:17:04Z (GMT). No. of bitstreams: 1 ThiagoSantos.pdf: 1103502 bytes, checksum: 16ad7405a0ab31d83423293c43110ee8 (MD5) Previous issue date: 2017-09-11 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Fundação de Amparo à Pesquisa e ao Desenvolvimento Científico e Tecnológico do Maranhão / Instituto Nacional de Ciência e Tecnologia em Bioanalítica / A photoelectroanalytical sensor was developed, based on deoxyribonucleic acid (DNA) and anatase titanium dioxide (TiO2) nanoparticles sensitized with bis(ethylenedithio)tetrathiofulvalene (BEDT-TTF) for determination of the adrenaline, also denominated as epinephrine. The photosensor composite developed was denominated as BEDT-TTF/DNA/TiO2/ITO and shows a high photocurrent for the adrenaline under light emitting diode (LED) irradiation in comparison to each component of the composite material. Under optimized conditions, the BEDTTTF/DNA/TiO2/ITO sensor shows a linear response range from 10 nmol L-1 up to 100 μmol L-1 with a sensitivity of 8,1 nA L μmol-1 and limit of detection of 1 nmol L-1 for the adrenaline. The photoelectrochemical sensor showed high photocurrent to adrenaline in comparison to photocurrent response to ascorbic acid and uric acid. The BEDT-TTF/DNA/TiO2/ITO photoelectrochemical sensor was successfully applied to urine samples, with recovery values between 96 and 106%. / Um sensor fotoeletroanalítico foi desenvolvido, baseado em ácido desoxirribonucleico (DNA) e nanopartículas de dióxido de titânio anatase (TiO2) sensibilizadas com bis(etilenoditio)tetratiofulvaleno (BEDT-TTF) para a determinação de adrenalina, também denominada como epinefrina. O fotossensor compósito desenvolvido foi denominado como BEDT-TTF/DNA/TiO2/ITO e exibiu uma elevada fotocorrente para a adrenalina sob a irradiação do diodo emissor de luz (LED) em comparação com cada componente do material compósito. Sob condições otimizadas, o sensor BEDT-TTF/DNA/TiO2/ITO exibiu um intervalo de resposta linear de 10 nmol L-1 para 100 μmol L-1 com uma sensibilidade de 8,1 nA L μmol-1 e limite de detecção de 1 nmol L-1 para a adrenalina. O sensor fotoeletroquímico mostrou elevada fotocorrente para a adrenalina em comparação com a resposta de fotocorrente para ácido ascórbico e ácido úrico. O fotossensor BEDTTTF/DNA/TiO2/ITO foi aplicado com sucesso em amostras de urina, com valores de recuperação entre 96 e 106%.

An efficient Light Emitting Diode (LED) lamp driver circuit is proposed for retrofitting the conventionally used incandescent lamps with existing TRIAC dimmer. The dimming feature in a wide range of firing angle from 30¢X to 130¢X can be accomplished by means of double pulse-width modulation (DPWM) and analog current regulation. The LED lamp driver adopts a flyback converter with an auxiliary active power MOSFET for synchronous switch and an associated inductor for zero voltage switching (ZVS), leading to lower switching loss and thus achieving a higher circuit efficiency. In the thesis, the mode operation of the driver circuit is analyzed and the design equations are derived accordingly. A laboratory circuit is designed for an 50 W LED lamp which is composed of 45 high-brightness white LEDs in series. Experiments are carried out to test the circuit performances with two dimming schemes. The experimental results indicate that the driver can achieve a circuit efficiency of 95 % at the rated output. When the LED lamp is dimmed, the circuit efficiency with DPWM is higher than that with the analog current regulation. On the other hand, the LED lamp dimmed by analog current regulation has a higher efficiency but a less color shift by DPWM.

Optimising illumination is essential for optimising the growth of phototrophic cells and their production of desired metabolites and/or biomass. This requires appropriate modulation of light and other key inputs and continuous online monitoring of their metabolic activities. Powerful non-invasive systems for cultivating heterotrophic organisms include shake flasks in online monitoring units, but they are rarely used for phototrophs because they lack the appropriate illumination design and necessary illuminatory power. This study presents the design and characterisation of a photosynthetic shake flask unit, illuminated from below by warm white light-emitting diodes with variable light intensities up to 2300 μmol m-2 s-1. The photosynthetic unit was successfully used, in combination with online monitoring of oxygen production, to cultivate Arthrospira platensis. In phototrophic growth under continuous light and a 16 h light/8 h dark cycle (light intensity: 180 μmol m-2 s-1), the oxygen transfer rate and biomass-related oxygen production were - 1.5 mmol L-1 h-1 and 0.18 mmol O2 gx-1 h-1, respectively. The maximum specific growth rate was 0.058 h-1, during the exponential growth phase, after which the biomass concentration reached 0.75 g L-1.

Light has a wide and profound non-visual impact on the human body. It is related to the suppression or synthesis of a hormone called melatonin which regulates the human circadian clock. In Nordic countries like Sweden, lack of natural light in winter may lead to negative health effects such as circadian disorders or depression. At the same time, the underground metro system in Stockholm carries more than one million passengers on a weekday. The lighting in the train carriage may have distinct circadian effects on the passengers. The paper takes the metro system in Stockholm as an example, calculates the non-visual effects of the artificial lighting in the train according to Equivalent Melanopic Lux (EML), Circadian Stimulus (CS) and Melanopic Equivalent Daylight Illuminance (M-EDI) Models, compares with current guidance and suggestions, considers the daylighting conditions of Stockholm, and proposes a new design solution with adjustable LEDs to achieve a better healthful circadian lighting result.

La thèse intitulée «Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” eststructurée en cinq chapitres traitant de nouveaux: a)cyclopenta[c]pyrannes hétérocyclique; b)des propriétés fluorescentes; d) potentiels dispositifs de l'électroniquemoléculaire; d) donneurs moléculaires pour les photovoltaïquesorganiques et e) carbon‘quantum’dots électroluminescents.Le premier chapitre présente une étude des dérivéspseudoazulenique ayant une unité cyclopenta[porte sur leur synthèse, l'analyse structurale et leur comportement dansdes réactions de substitution électrophile pour obtenir des composésayant des propriétés fluorescentes.Le deuxième chapitre présentediastéréoisomères et l'étude de propriétés de fluorescencedérivés d’indenopyrone.Le troisième chapitre décrit la synthèse des nouvellesarchitectures basées sur l’unité cyclopenta[être modifiés structurellement par l'influence d'un stimulus chimiqueou électrochimique afin d'élaborer des potentiels dispositifs del'électronique moléculaire.Dans le quatrième chapitre, la synthèsedes propriétés électroniques des nouvelles molécucellules solaires organiques (OSC) ontLe cinquième et dernier chapitre décrit la passivation desdéfauts de surface des nanoparticules de carbone avec desmolécules organiques ou des polymères pour obtenir desnanoparticules de carbone photoluminescentse surnommé ‘quantum dots. / The thesis entitled “Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” isstructured into five chapters concerning new: a) heterocycliccyclopenta[c]pyrans; b) indenopyrone derivatives with fluorescentproperties; c) potential devices of molecular electronics; d)donors for organic photovoltaics and e) electroluminescent carbon‘quantum’ dots.The first chapter presents a study of pseudoazulenederivatives having a cyclopenta[c]pyran unit. The survey comprises thesynthesis, structural analysis and reactivity towards electrophilicsubstitution in order to obtain fluorescent compounds.The second chapter deals with the separation odiastereoisomers and the study of fluorescent propertiesindenopyrone derivatives.The third chapter describes the synthesis of newarchitectures based on cyclopenta[c]pyran unit that can be structurallymodified by the influence of a chemical or electrochemical stimulus inorder to work as potential devices in molecular electronics.In the fourth chapter, the synthesis andelectronic properties of new molecular donors for organic solar cellswas described.The fifth and last chapter outlines the passivation of surfacedefects on carbon nanoparticles using small organic molecules orpolymers in order to obtain photoluminescent carbon nanoparticlesdubbed as carbon‘quantum’dots.

This thesis addresses a multi-phase research and development project that spanned nearly four years, targeted at providing an ultra high-efficiency, user-friendly, and economic intelligent lighting solution for commercial facility applications, initially targeting underground parking specifically. The system would leverage the strengths of four key technologies: high brightness white Light Emitting Diodes (LEDs), wireless sensor and actuator networks, single board computers, and cloud computing. An introduction to these technologies and an overview of how they were combined to build an intelligent lighting solution is given, followed by an in-depth description of the design and implementation of one of the main subsystems – the Sensor Middleware System – residing on a single board computer. Newly-available LED luminaires (a.k.a. light fixtures) bring the combination of high efficiency, reliability, illumination quality, and long-lifetime to the lighting market. Emerging low-power – and recently low-cost – 802.15.4 wireless networks offer high controllability and responsiveness to deployed luminaires and sensors. The cost- associativity, low maintenance, and easy build-up of Internet Data Center “cloud” computing resources make data collection and remote management infrastructure for Building Automation Systems accessible to even small companies. Additionally, these resources can be much more appropriately sized and allocated, which reduces energy use. These technologies are combined to form an Intelligent Lighting System (ILS). Fitting well within the Internet of Things paradigm, this highly distributed messaging-based “system of systems” was designed to be reliable through loose coupling – spanning multiple network layers and messaging protocols. Its goal was to deliver significant energy savings over incumbent technologies, configurable and responsive lighting service behaviour, and improved experience for users within the facility (pedestrians and drivers) and those interacting with its web-based tools (building managers and ILS administrators). The ILS was partitioned into three main subsystems as follows. The installed Wireless Field Network (WFN) of luminaires and sensors provided coordinated scheduled and real-time output level adjustment (i.e. dimming), with the help of motion sensor triggers. The Monitoring and Configuration System (MCS) in the cloud provided remote data collection and a web-based monitoring and configuration Graphical User Interface application. Network hardware and Message-Oriented Middleware (MOM) were responsible for tying these subsystems together. The MOM layer that provided the message brokering, translating, envelope wrapping, and guaranteed delivery services between the WFN and MCS, as well as field supervisory and quality-of-service functions for the WFN, was called the Sensor Middleware System (SMS). It was hosted on a single board computer located at the facility. / Graduate

In this thesis I present a study of nanowires, and, in particular, I apply EBIC microscopy for investigation of their electro-optical properties. First, I describe details of the EBIC analytical technique together with a brief historical overview of the electron microscopy, the physical principles of the EBIC, its space resolution, parameters defining the signal amplitude, and the information we can acquire concerning defects, electric fields, etc. Then I focus on the characterization of LEDs based on GaN nanowires, which were analyzed in a cross-section and in a top view configurations. The EBIC measurements were correlated with micro-electroluminescence mapping. Further, I address the fabrication and measurement of nanowire-based InGaN/GaN LEDs detached from their original substrate. I present the EBIC measurements of individual nanowires either cut from their substrate and contacted in a planar geometry or kept standing on supphire substrate and cleaved to reveal the horizontal cross-section.The next part of this thesis is dedicated to an EBIC study of irregular Si nanowire array-based solar cells, and then of the regular nanowire array devices. The current generation was analyzed on a submicrometer scale. Finally, I discuss the fabrication and EBIC measurements of GaN nanowires grown on Si substrate. In particular, I show that the p-n junction was induced in the Si substrate by Al atom diffusion during the nanowire growth. / Dans cette thèse je me propose d’étudier des nano-fils, et en particulier d’utiliser la technique EBIC pour explorer leurs propriétés électro-optiques. Je décris d’abord les détails de la technique d’analyse EBIC avec un bref retour historique sur la microscopie électronique, le principe physique de l’EBIC, sa résolution spatiale, les paramètres conditionnant l’amplitude du signal, et les informations que l’on peut en tirer sur le matériau en termes de défauts, champ électrique, etc. Je m’intéresse ensuite à la caractérisation de LEDs à nano-fils à base de GaN, qui ont été observés par EBIC, soit en coupe soit en vue plane (depuis le haut des fils). Les mesures EBIC sont comparées à celles de micro-électroluminescence. Plus loin j’adresse la fabrication et la mesure de nano-fils à base de GaN séparés de leur substrat d’origine. Je présente les mesures EBIC de nano-fils uniques entiers, puis de nano-fils en coupe horizontale.La partie suivante de la thèse traite d’étude EBIC des cellules solaires à base de nano-fils Si ayant d’abord une géométrie aléatoire, puis une géométrie régulière. La génération de courant dans ces cellules solaires est analysée à l’échelle submicronique. A la fin du manuscrit je discute la fabrication et les mesures EBIC de fils GaN épitaxiés sur Si. Je montre en particulier qu’une jonction p-n est enduite dans le substrat Si par la diffusion d’Al lors de la croissance de nanofils.