There is a compelling need for the development of new sensory and neural prosthetic devices which are capable of more precise point stimulation. Current prosthetic devices suffer from the limitation of low spatial resolution due to the non-specific stimulation characteristics of electrical stimulation, i.e., the spread of electric fields generated. We present a visible light stimulation method for modulating the firing patterns of electrically-excitable cells using surface plasmon resonance phenomena. In in-vitro studies using gold (Au) nanoparticle-coated nanoelectrodes, we show that this method (substrate coated with nanoparticles) has potential for incorporating the technology into neural stimulation prosthetics, such as cochlear implants, with arbitrarily high spatial resolution. Au nanoparticles (NPs) were coated on micropipettes using aminosilane linkers; and these micropipettes were used for stimulating and inhibiting the action potential firing patterns of SH-SY5Y human neuroblastoma cells and neonatal cardiomyocytes. Our findings pave the way for development of biomedical implants and neural testing devices using nanoelectrodes capable of temporally and spatially precise excitation and inhibition of electrically-excitable cellular activity.

Visible light-driven photocatalysis has shown considerable potential in the area of clean and renewable energy, as well as in wastewater treatment. This thesis describes the synthesis, characterization and applicability of a visible-light active photocatalyst, bismuth oxybromide (BiOBr). The photocatalytic activity of BiOBr was investigated through its preparation via hydrothermal and solvothermal synthesis routes under various conditions. Hydrothermal catalyst was prepared using non template based method while for solvothermal synthesis CTAB was used as a template. Parameters of temperature and time of thermal treatment were optimized for each synthesis method and overall tests for catalyst dosage and recyclability were performed. An overall optimal route leading to high photocatalytic performance was also proposed based on the obtained results. Studies were also conducted to examine the applicability of optimally synthesized BiOBr in drinking water applications by studying catalyst-mediated disinfection of E. coli and degradation of phenol. Favourable results were obtained, confirming the prospective application of BiOBr as a viable photocatalyst for disinfection. Furthermore, the potential of enhancing BiOBr to further improve its performance is described through synthesis of a novel PdCl2/BiOBr based photocatalyst. Overall, the performance of BiOBr under various conditions in this study establishes its potential as a holistic photocatalyst and merits further development.

Ce travail a pour objectif de réorienter un cristal liquide nématique par la photoisomérisation de deux composés azoïques greffés sur des lames de verre, le DR19 et le DR1. Dans une première étape, nous avons procédé à la silanisation de ces composés photosensibles afin de pouvoir les greffer chimiquement sur des substrats siliciques. Nous avons ensuite greffé ces chromophores sur de la silice mésoporeuse afin d’optimiser la méthode de greffage. Deux paramètres ont été pris en compte dans cette étude : la nature du solvant et le taux d’hydratation de la surface. Une analyse quantitative, structurale et spectroscopique des matériaux hybrides, nous a permis de conclure à la chimisorption des deux azosilanes sur la surface de la silice. Les greffages du DR19Si en milieu éthanolique aqueux d’une part, et du DR1Si dans le THF sur de la silice hydratée d’autre part, ont donné les meilleurs résultats du point de vue quantitatif. A partir de ces résultats, nous avons procédé au greffage des azosilanes sur les lames de verre en mettant en évidence l’importance du film d’eau physisorbé en surface. La caractérisation chimique par les spectroscopies UV/Visible et SPX a démontré la présence des chromophores sur la surface des lames. Une modélisation par SPX des lames de verre fonctionnalisées a été également effectuée puis confirmée par MFA. Enfin, l’action de ces lames fonctionnalisées par greffage sur la réorientation du 5CB a été appréciée au moyen d’un montage pompe-sonde. L’efficacité cinétique et quantitative des chromophores greffés sur une surface a été comparée à celle des chromophores libres dispersés dans la mésophase. / This work aims to reorientate a nematic liquid crystal by the photoisomerization of two azo compounds grafted on glass slides, the DR19 and the DR1. First, we have proceeded to the silanisation of these photosensitive compounds in order to be able to graft them chemically on silica substrates. Then we have grafted these chromophores on mesoporous silica in order to optimize the grafting method. Two parameters have been taken into account in this study: the nature of the solvent and the surface hydration rate. A quantitative, structural and spectroscopic analysis of hybrid materials enabled us to conclude to the chemisorption of both azosilanes on silica surface. Quantitatively, the DR19Si grafting in an ethanolic aqueous solution, and the DR1Si one, in a THF solution on hydrated silica gave the best results. From these results, we have proceeded to the azosilanes grafting on the glass slides while highlighting the importance of the physisorbed water film on the surface. Chemical characterization by UV/Visible and XPS spectroscopy has shown the presence of chromophores on the slides surface. A modelling by XPS, of the functionalized glass slides was also carried out and confirmed by AFM. Lastly, the action of these slides functionalized by grafting on the 5CB reorientation has been appreciated by means of an experimental pump-probe set-up. The kinetic and quantitative effectiveness of grafted chromophores on a surface have been compared with the one of free chromophores dispersed in the mesophase.

Essa pesquisa objetiva avaliar a eficácia de uma estratégia educacional aplicada junto a funcionários do setor de evisceração de um abatedouro de frango com vistas à diminuição de contaminação gastrointestinal de carcaças. A estratégia classifica-se como treinamento para exercer a função, externo ao serviço, específico e individual. Foi utilizado o método de aula expositiva-dialogada e motivacional. O conteúdo do treinamento procurou explicitar a relação entre as inadequações técnicas e comportamentais no setor de evisceração que resultam em ruptura do trato gastrointestinal, contaminação visível das carcaças e possibilidade de multiplicação de microrganismos patogênicos. Enfocou a gravidade das doenças para os consumidores bem como a corresponsabilidade e agravantes para a empresa e funcionários. Depois do treinamento (DT), os dados referentes à ocorrência e à persistência de contaminação não apresentaram, em termos de mediana, diferença significativa quando comparados ao período antes do treinamento (AT). Com relação à variância, houve diminuição significativa para a ocorrência de contaminação fecal (? = 1%) e fecal e biliar (? = 4%) quando comparada ao período AT. No período DT, a variância do percentual de persistência de contaminação diminuiu significativamente para todos os tipos de contaminação (? = 1% para contaminações fecal e biliar e 2% para gástrica) quando comparada à fase AT. Os picos (dias com persistência de contaminação maior ou igual a 1%) foram reduzidos de 38% para 4% (fecal), de 45% para 26% (biliar) e de 41% para 35% (gástrica). Embora existam fatores influentes do pré-abate, os funcionários do setor de evisceração são os principais responsáveis pela geração de contaminação visível, devido ao corte ou ruptura do trato gastrointestinal e não retirada da contaminação. Assim, diante da dificuldade em conter a maioria dos fatores que ocasionam a contaminação visível no abatedouro e da evidência do baixo nível de conscientização e instrução dos funcionários para as questões pertinentes à segurança do alimento, o investimento em um adequado programa de treinamento pode ser a ação com a melhor relação custo-benefício a fim de diminuir a persistência de contaminação visível em carcaças, os prejuízos decorrentes da sua alta ocorrência e proporcionar um alimento seguro ao consumidor e a sobrevivência da empresa no mercado global. / This research aims to evaluate the effectiveness of an educational strategy applied to employees from evisceration area of a broiler slaughterhouse, in order to decrease gastrointestinal contamination of carcasses. The strategy is classified as training to perform the function, outside the service, specific and individual. The methodology used was the exposition and dialogue lecture and motivational. The content of the training aimed explain the relationship between the technical and behavioral inadequacies in the sector of evisceration that result in rupture of the gastrointestinal tract, visible contamination of carcasses and possible growth of pathogens. It was focused on the severity of foodborne illness to consumers as well as the joint responsibility and losses for the company and employees. After training (AT), the data regarding the occurrence and persistence of contamination did not present a significant difference in terms of median, when compared to before training (BT) period. Regarding the variance, a significant decrease was observed for the occurrence of fecal contamination (? = 1%) and fecal and bile (? = 4%) when compared to BT. In the after training period, the variance of persistence contamination percentage was significantly reduced for all kinds of contamination (? = 1% bile and fecal contamination, and 2% to gastric) when compared to BT period. The persistence of contamination peaks were reduced from 38% to 4% (fecal), 45% to 26% (bile) and from 41% to 35% (gastric). Although there are factors influencing the pre-slaughter, the evisceration sector employees are the major responsible for the generation of visible contamination, due to cuts or rupture of the gastrointestinal tract and non removel of contamination. Thus, given the difficulty in containing most of the factors that cause visible contamination at the slaughterhouse, and evidence of low level of awareness and training of employees on issues related to the food safety, investment in an appropriate training program can be the action with the most costeffective to decrease the persistence of visible contamination of carcasses, the negative effects of high occurrence and provide a safe food to consumers and the company\'s survival in the global market.

Photopolymerization has become the standard for many coating and printing applications that require rapid curing at room temperature due to its potential to reduce volatile organic compound (VOC) emissions while providing a means for efficient manufacturing processes. These advantages could be useful in a variety of emerging applications, such as anisotropic conductive films (ACF) if photopolymerization could extend into relatively narrow shadow regions which are not directly illuminated, and if visible wavelengths that are not absorbed by polyimide films could be used to trigger the reaction. The broad objectives of this research are i) to examine the factors that determine the attainable extent of shadow cure in free radical polymerizations, and ii) to develop initiator systems effective for polymerization using visible light and light emitting diode (LED) lamps. Project I: Shadow Cure in Free Radical Photopolymerizations In this project, the extent of shadow cure in visible-light-induced free radical photopolymerization is investigated. A number of effective methods such as adding additives, utilizing a reflective stage, and increasing the light intensity are introduced. In addition, the use of fluorescent dyes in multi-component photoinitiator systems proved to be very effective for shadow cure because the fluorescent light emitted from the dye could irradiate the shadow region. When considering practical resins, mixtures of oligomers and monomers, the viscosity is the major barrier that must be overcome in order to achieve high conversion in the shadow regions using visible-light-induced multi-component photoinitiator systems. Hence, instead of using multi-component systems, a commercial visible-light-induced single-component photoinitiator is investigated. As a result, a high conversion in shadow regions of the viscous oligomer containing resin is achieved. Project II: Experimental and Modeling Studies of Photoinitiator Systems for Effective Polymerizations with LEDs In this project, various LED photocuring systems are investigated and characterized. The light intensities of LEDs become weaker as their peak emission wavelengths decrease. Therefore, to design the practical process of LED curing, the effect of both the light intensity and the emission spectrum of the lamp must be considered. Photopolymerization for four representative UV photoinitiators with different LEDs are investigated experimentally and theoretically. The effective light source is dependent on the photoinitiators and several LEDs demonstrate high thin cure ability. The calculated results from a model display good qualitative correspondence with the experimental results. Various interesting suggestions are obtained using this model. For example, the commercialization of 355 nm LEDs might be able to superior photopolymerization compared to other currently available LED lamps.

The past decade witnessed the rapid development of III-nitride light-emitting diodes (LEDs) and laser diodes (LDs), for smart lighting, visible-light communication (VLC), optical storage, and internet-of-things. Recent studies suggested that the GaN-based LDs, which is free from efficiency droop, outperform LEDs as a viable high-power light source. Conventionally, the InGaN-based LDs are grown on polar, c-plane GaN substrates. However, a relatively low differential gain limited the device performance due to a significant polarization field in the active region. Therefore, the LDs grown on nonpolar m-plane and semipolar (2021)-plane GaN substrates are posed to deliver high-efficiency owing to the entirely or partially eliminated polarization field. To date, the smart lighting and VLC functionalities have been demonstrated based on discrete devices, such as LDs, transverse-transmission modulators, and waveguide photodetectors. The integration of III-nitride photonic components, including the light emitter, modulator, absorber, amplifier, and photodetector, towards the realization of III-nitride photonic integrated circuit (PIC) offers the advantages of small-footprint, high-speed, and low power consumption, which has yet to be investigated. This dissertation presents the design, fabrication, and characterization of the multi-section InGaN laser diodes with integrated functionalities on semipolar (2021)-plane GaN substrates for enabling such photonic integration. The blue-emitting integrated waveguide modulator-laser diode (IWM-LD) exhibits a high modulation efficiency of 2.68 dB/V. A large extinction ratio of 11.3 dB is measured in the violet-emitting IWM-LD. Utilizing an integrated absorber, a high optical power (250mW), droop-free, speckle-free, and large modulation bandwidth (560MHz) blue-emitting superluminescent diode is reported. An integrated short-wavelength semiconductor optical amplifier with the laser diode at ~404 nm is demonstrated with a large gain of 5.32 dB at 6 V. A high-performance waveguide photodetector integrated LD at 405 nm sharing the single active region is presented, showing a significant large modulation bandwidth of 230 MHz. Thus these seamlessly integrated elements enable photonic IC at the visible wavelength for many important applications, such as smart lighting and display, optical communication, switching, clocking, and interconnect. The findings are therefore significant in developing an energy-saving platform technology that powers up human activities in a safe, health- and environmental-friendly manner.

Aromatic rings are universal motifs in natural products, pharmaceuticals, agrochemicals, and wide variety of organic materials. Aromatic halides are widely used as synthetic precursors in all these applications. Therefore, tremendous effort has been devoted to activate aryl halides in the past decades. The common methods to activate aryl halides require the use of transition-metals either in the form of Grignard reagents or through the use of transition-metal catalysis. <br>Over the past decade, photoredox catalysis has attracted significant attention as a cogent tool to develop greener synthetic processes and enable new molecular activation pathways under mild conditions. The most common of these approaches uses a photoredox/nickel dual catalytic cycle.<br>While this technology has greatly expanded the toolbox of organic chemists, this method still requires expensive rare-metal-based catalyts. Herein, we present a series of visible light-induced methods that are transition-metal-free. These new base-promoted transformations and their mechanistic work will be discussed in the following order:<br>We will first present our discovery that the dimsyl anion enables visible-light-promoted charge transfer in cross-coupling reactions of aryl halides. This work was applied to the synthesis of unsymmetrical diaryl chalcogenides. This method has a broad scope and functional group tolerance. An electron-donor-acceptor (EDA) complex between a dimsyl anion and the aryl halide is formed during the reaction and explains the observed aryl radical reactivity observed.<br>Then, a visible-light-induced borylation and phosphorylation of aryl halides under mild conditions was developed. Inspired by the mechanistic breakthroughs observed in the previous work. The mechanism of this reaction also involves an aryl radical that is presumed to be formed also via an EDA complex. In other work, a photo-induced phosphonation of ArI using N,N-diisopropylethylamine (DIPEA) and trialkyl phosphites was developed. This method uses very mild conditions, which allowed the preparation a wide variety of functionalized aromatic phosphonates derivatives, including natural products and medicinal compounds. Finally, a photochemical amination of amides was developed via a C(sp 3 )–H bond functionalization<br>process under visible light irradiation. This reaction showed good functional group compatibility without the use of external radical initiators, strong oxidants, or heat source. An EDA complex between N-bromophthalimide and LiOtBu is formed during the reaction.

Diplomová práce si dává za cíl navrhnout a uvést v praxi metodiku snímání oční duhovky ve viditelném spektru. Klade přitom důraz na kvalitu snímků, věrohodné podání barev vůči reálnému podkladu a hlavně na kontinuální hloubku ostrosti, která odhaluje dosud nezkoumané aspekty a detaily duhovky. V poslední řadě se také soustředí na co nejmenší vystavení duhovky fyzickému stresu. Metodika obsahuje přesné postupy jak snímat duhovku a zajištuje tím konzistentnost snímků. Tím umožní vytvářet databáze duhovek s ohledem na jejich vývoj v čase či jiném aspektu jako je například psychologický stav snímané osoby. Na úvod je v práci představena anatomie lidského oka a zejména pak duhovky. Dále pak známé způsoby snímání duhovky. Následuje část, jež se zabývá správným osvětlením duhovky. To je nutné pro požadovanou úroveň kvality snímků zároveň ale vystavuje oko velkému fyzickému stresu. Je tedy nutné najít kompromis mezi těmito aspekty. Důležitý je popis samotné metodiky obsahující podrobný popis snímání. Dále se práce zabývá nutnými postprodukčními úpravami jako je například složení snímků s různou hloubkou ostrosti do jednoho kontinuálního snímku či aplikací filtrů pro odstranění vad na snímcích. Poslední část práce je rozdělena na zhodnocení výsledků a závěr, v němž se rozebírají možné rozšíření či úpravy metodiky tak, aby ji bylo možné použít i mimo laboratorní podmínky.

Diplomová práce si dává za cíl navrhnout a uvést v praxi metodiku snímání oční duhovky ve viditelném spektru. Klade přitom důraz na kvalitu snímků, věrohodné podání barev vůči reálnému podkladu a hlavně na kontinuální hloubku ostrosti, která odhaluje dosud nezk- oumané aspekty a detaily duhovky. V poslední řadě se také soustředí na co nejmenší vys- tavení duhovky fyzickému stresu. Metodika obsahuje přesné postupy jak snímat duhovku a zajištuje tím konzistentnost snímků. Tím umožní vytvářet databáze duhovek s ohledem na jejich vývoj v čase či jiném aspektu jako je například psychologický stav snímané os- oby. Na úvod je v práci představena anatomie lidského oka a zejména pak duhovky. Dále pak známé způsoby snímání duhovky. Následuje část, jež se zabývá správným osvětlením duhovky. To je nutné pro požadovanou úroveň kvality snímků zároveň ale vystavuje oko velkému fyzickému stresu. Je tedy nutné najít kompromis mezi těmito aspekty. Důležitý je popis samotné metodiky obsahující podrobný popis snímání. Dále se práce zabývá nutnými postprodukčními úpravami jako je například složení snímků s různou hloubkou ostrosti do jednoho kontinuálního snímku či aplikací filtrů pro odstranění vad na snímcích. Poslední část práce je rozdělena na zhodnocení výsledků a závěr, v němž se rozebírají možné rozšíření či úpravy metodiky tak, aby ji bylo možné použít i mimo laboratorní podmínky.

The limited overcrowded radio frequency spectrum compelled researchers to ex plore higher frequency ranges for wireless transmission. In recent decades, visible light communications (VLC) have gained lots of research attention thanks to the abundant bandwidth and the existing lighting infrastructure they offer. Throughout this dissertation, we study the downlink of multi-user VLC systems with the aim of operation and architecture enhancement. In this context, we accommodate the chal lenges imposed by the visible light nature such as illumination requirements and mod ulation constraints. On the operation optimization front, we investigate three VLC setups: indoor single cell, outdoor energy harvesting enabled single cell, and indoor energy harvesting enabled multi-cell VLC systems. We formulate, and provide low complexity solutions to, resource allocation problems for each setup while accounting for scenario-tailored system objectives and quality of service requirements. For the first setup, the temporal average illumination is maintained fixed while maximizing the system SE and dynamic time-division-multiple-access is employed to serve users in an interference free setup. As for the second setup, owing to the favored joint lighting and SE maximization, we solve a multi-objective optimization problem accounting for both objectives. We found that the severity of the illumination - communications tradeoff increases as the available system power budget decreases or the minimum rate requirements get tighter. In the third setup, transmitters average currents and receivers fields of view tuning strategies are developed to maximize both spectral ef ficiency and energy harvesting objectives in an interference limited scenario, where spatial illumination uniformity is required. It is found that receivers fields of view tuning is substantial to performance enhancement in dense deployments. On the architecture optimization front, we propose two intelligent reflecting surfaces-aided VLC systems and derive their power density distribution in the receiver plane. In addition, we prove their power concentration capability and quantify their relative gain with respect to one another and with respect to the reflector-free VLC systems enjoying direct line of sight. Finally, we study the channel impulse response of the proposed reflecting systems and quantify the incurred delay spread through exact ex pression, simplified bounds and asymptotic expressions when the number of reflecting elements grows unboundedly.