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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
101

Design and performance analysis of optical attocell networks

Yin, Liang January 2018 (has links)
The exponentially increasing demand for high-speed wireless communications will no longer be satisfied by the traditional radio frequency (RF) in the near future due to its limited spectrum and overutilization. To resolve this imminent issue, industrial and research communities have been looking into alternative technologies for communication. Among them, visible light communication (VLC) has attracted much attention because it utilizes the unlicensed, free and safe spectrum, whose bandwidth is thousand times larger than the entire RF spectrum. Moreover, VLC can be integrated into existing lighting systems to offer a dual-purpose, cost-effective and energy-efficient solution for next-generation small-cell networks (SCNs), giving birth to the concept of optical attocell networks. Most relevant works in the literature rely on system simulations to quantify the performance of attocell networks, which suffer from high computational complexity and provide limited insights about the network. Mathematical tools, on the other hand, are more tractable and scalable and are shown to closely approximate practical systems. The presented work utilizes stochastic geometry for downlink evaluation of optical attocell networks, where the co-channel interference (CCI) surpasses noise and becomes the limiting factor of the link throughput. By studying the moment generating function (MGF) of the aggregate interference, a theoretical framework for modeling the distribution of signal-to-interference-plus-noise ratio (SINR) is presented, which allows important performance metrics such as the coverage probability and link throughput to be derived. Depending on the source of interference, CCI can be classified into two categories: inter-cell interference (ICI) and intra-cell interference. In this work, both types of interference are characterized, based on which effective interference mitigation techniques such as the coordinated multipoint (CoMP), power-domain multiplexing and successive interference cancellation (SIC) are devised. The proposed mathematical framework is applicable to attocell networks with and without such interference mitigation techniques. Compared to RF networks, optical attocell networks are inherently more secure in the physical layer because visible light does not penetrate through opaque walls. This work analytically quantifies the physical-layer security of attocell networks from an information-theoretic point of view. Secrecy enhancement techniques such as AP cooperation and eavesdropper-free protected zones are also discussed. It is shown that compared to AP cooperation, implementing secrecy protected zones is more effective and it can contribute significantly to the network security.
102

Aproveitamento de radiação solar na geração de hidrogênio empregando fotocatalisadores do tipo CdS, ZnS e Cd (1-x)ZnxS

Lopes, Paula Aparecida Lima 07 1900 (has links)
Submitted by Ana Hilda Fonseca (anahilda@ufba.br) on 2014-10-21T15:52:48Z No. of bitstreams: 1 Dissertação de mestrado Paula Lopes.pdf: 3114896 bytes, checksum: 64c14138aec1c0f19b0f9445d7a07625 (MD5) / Approved for entry into archive by Ana Hilda Fonseca (anahilda@ufba.br) on 2014-10-29T17:29:36Z (GMT) No. of bitstreams: 1 Dissertação de mestrado Paula Lopes.pdf: 3114896 bytes, checksum: 64c14138aec1c0f19b0f9445d7a07625 (MD5) / Made available in DSpace on 2014-10-29T17:29:36Z (GMT). No. of bitstreams: 1 Dissertação de mestrado Paula Lopes.pdf: 3114896 bytes, checksum: 64c14138aec1c0f19b0f9445d7a07625 (MD5) / Energia e Ambiente ocupam posições de destaque dentre os grandes desafios da hu manidade e a produção de hidrogênio a partir da reforma foto - induzida de solução aquosa de glicerol é uma investigação de grande interesse científico e importância para a sociedade e o meio ambiente , pelo fato de gerar energia limpa a partir de fontes reno váveis e com baixo custo. Neste sentido, o presente trabalho propõe desenvolver semicondutores do tipo sulfetos metálicos e soluções sólidas do tipo Cd (1 - x) Zn x S capazes de absorver luz visível e assim conduzir a reação de decomposição da água e glicerol le vando à produção de hidrogênio assistida por um simulador de luz solar . Para tanto, foi desenvolvido um método sonoquímico de síntese de nanopartículas dos sulfetos com diferentes proporções Cd:Zn:S nas soluções de partida. As análises de difração de raios X confirmaram a obtenção das fases dos sulfetos puros e soluções sólidas. As micrografias obtidas por microscopia eletrônica de varredura revelam diferentes morfologias a depender do teor de zinco nas soluções sólidas e a formação de nanoesferas de CdS pu ro em fase hexagonal. Os materiais ainda foram caracterizados por EDX, DRS e análise textural por adsorção de N 2 . A avaliação da atividade fotocatalítica na produção de hidrogênio revelou que todas as amostras contendo Cd em sua composição foram ativas, co m exceção da amostra S 8 ( Cd:S 1:8). O fotocatalisador que apresentou melhor atividade foi a solução sólida obtida com a proporção 1:8:4 (Cd:Zn:S), com uma taxa de produção de hidrogênio de 239  mol g - 1 h - 1 . Os resultados demonstraram que a introdução de zinco na matriz wurtzita de CdS aumenta a atividade fotocatalítica e a estab ilidade do fotocatalisador em me io aquoso. / Energy and Environment are ones of the great challenges of humanity and the production of hydrogen from photo - induced reforming of glycerol aqueous solution is an investigation of great scientific interest and importan t fo r the society and the environment . This process can generate clean e nergy from renewable sources with low cost. In this sense, the present work proposes to develop semiconductor s, metal sulfide type and solid solutions type, Cd (1 - x) Zn x S , able to absorb vis ible light and decompos e water and glycerol leading to hydrogen production assisted by a simulator sunlight. Thus , it was developed a sonochemical method to synthesi ze semiconductor nanopar ticles with different Cd:Zn:S ratios in starting solutions. X - ray d iffraction analysi s confirmed the formation of pure sulfides and solid solutions phase s . The micrographs obtained by scanning electron microscopy reveal different morphologies depending on the zinc content in the solid solutions and the formation of CdS na no - spheres in hexagonal pure phase. The material s w ere also ch aracterized by EDX, DRS and textural analysi s by N 2 adsorption . The assessment of photocatalytic activity in hydrogen production showed that all samples containing Cd were active with respect to hydrogen production , exception S 8 sample ( Cd:S 1:8). The photocatalyst that showed the best activity was the solid solution obtained with the ratio 1:8:4 (Cd:Zn:S), with a hydrogen production rate of 239 μmol g - 1 h - 1 . The results demonstrated that the int roduction of zinc in CdS wurtzite matrix increases the photocatalyt ic activity and stability of the photocatalyst in aqueous medium
103

DYRP-VLC: a dynamic routing protocol for visible light communication networks

Matheus, Luiz Eduardo Mendes 03 September 2018 (has links)
Submitted by Renata Lopes (renatasil82@gmail.com) on 2018-11-19T12:44:23Z No. of bitstreams: 1 luizeduardomendesmatheus.pdf: 1606990 bytes, checksum: 2736fa2230ff16ef4aaa41155178b616 (MD5) / Approved for entry into archive by Adriana Oliveira (adriana.oliveira@ufjf.edu.br) on 2018-11-23T13:06:46Z (GMT) No. of bitstreams: 1 luizeduardomendesmatheus.pdf: 1606990 bytes, checksum: 2736fa2230ff16ef4aaa41155178b616 (MD5) / Made available in DSpace on 2018-11-23T13:06:46Z (GMT). No. of bitstreams: 1 luizeduardomendesmatheus.pdf: 1606990 bytes, checksum: 2736fa2230ff16ef4aaa41155178b616 (MD5) Previous issue date: 2018-09-03 / Na última década, o interesse (acadêmico e comercial) em torno da Comunicação por Luz Visível (VLC) aumentou consideravelmente, devido a fatores como a crescente demanda por recursos sem fio na Internet e às vantagens oferecidas pela transmissão de dados através da luz visível. Entretanto, a utilização da luz como meio de comunicação, principalmente em ambientes internos, oferece diversos desafios, como interferência e bloqueios criados por obstáculos. Ao mesmo tempo, este tipo de ambiente oferece uma rica infraestrutura de fontes de luz, que podem ser utilizadas para auxiliar na comunicação através de mecanismos multi-hop. A maioria dos trabalhos presentes na literatura adotam técnicas simples para construção de mecanismos multi-hop em redes VLC, focando principalmente em aumento de distância. Neste trabalho, foi desenvolvido um protocolo de roteamento dinâmico, DYRP-VLC (DynamicRoutingProtocolforVisibleLightCommunication),quetemcomoobjetivo aumentar o desempenho de sistemas VLC em ambientes dinâmicos, enquanto reage à obstáculos construindo rotas alternativas na rede. A avaliação do protocolo foi realizada em um ambiente real, utilizando a plataforma embarcada OpenVLC 1.0 e métricas adotadas para problemas de roteamento. Os resultados obtidos mostram que, usando o DYRP-VLC, a rede foi capaz de se adaptar a mudanças dinâmicas na comunicação, como sombras e obstáculos, com pouca sobrecarga. / In the last decade, the interest in Visible Light Communication (VLC) has increased considerably, from both academic and commercial perspectives, due to factors such as the growing demand for wireless resources and the advantages offered by the transmission of data through visible light. However, the use of light as a communication medium, especially in indoor environments, offers several challenges, which includes shadowing and interference caused by obstacles. At the same time, this type of environment offers a rich infrastructure of light sources, which can be used to aid communication through multi-hop mechanisms. Most of the works present in the literature adopt simple techniques to construct multi-hop mechanisms in VLC networks, focusing mainly on increasing distance. Inthisthesis,wedevelopedDYRP-VLC(DynamicRoutingProtocolforVisibleLight Communication), a reactive routing protocol which aims to increase the performance ofVLCsystemsindynamicenvironments,whilereactingtoobstaclesbyconstructing alternative routes in the network. The evaluation of the protocol was performed in a real environment, using OpenVLC 1.0 embedded platform and adopting metrics for routing problems. The results show that, by using DYRP-VLC, the network was able to adapt to dynamic changes in communication, such as shadows and obstacles, with low overhead.
104

Using angle diverse and modulated optical sources for 3D indoor positioning

Lam, Emily 19 May 2020 (has links)
Indoor positioning is an enabling technology primed to impact the indoor application space as Global Navigation Satellite Systems (GNSS) did for the outdoor space. Amongst the competing positioning technologies are methods of different mediums: light, radio frequency and ultra-wideband, ultrasonic, and imaging; methods of different modalities: received signal strength, angle-of-arrival, time-of-flight; and methods of different mathematics: trilateration, triangulation, machine learning, and signal processing. Light-based positioning compared to other positioning schemes exploits fixed-location directional luminaires placed regularly throughout a space as anchor points -- there is an efficiency argument for multi-purpose lighting and a cost-share argument for infrastructure-based positioning. Similar to the satellite infrastructure with GNSS, with anchor points and models for light propagation and construction, position is estimated based on received signals at active photodiode-equipped target devices. Received signal strength, a common first order attribute, alone is not noise resilient enough for centimeter-level 3D positioning. Methods using angle diversity produce better results particularly in 3D but with more complex hardware. For this dissertation, we exploit angle diversity and modulated optical sources in light-based positioning systems to estimate position to centimeter-level accuracy in 3D. We propose, analyze, and contribute two novel positioning schemes that use these concepts. One of the proposed schemes is a new hybrid 3D indoor positioning technique, Ray-Surface Positioning (RSP), which incorporates a narrow field-of-view (FOV) optical source (Ray) with wide diffuse optical sources (Surfaces) to position active devices in 3D. The second scheme, a Zone-based Positioning Service (ZPS), is a positioning scheme and architecture that incorporates an angle diverse narrow FOV optical source at the positioned device. This unique design decision allows the active device to position itself directly with respect to photovoltaic anchor points but also to position other devices in its FOV called transitive positioning. Along with these contributions, we also investigate several other related topics. Concisely, as part of the dissertation, we contribute (a) review of the state-of-the-art, (b) analysis for steering Lambertian sources, (c) method of creating angle diversity from a narrow FOV optical source, (d) novel positioning approaches in (1) RSP and (2) ZPS, (e) proof of concept prototypes for (1) RSP and (2) ZPS, and (f) architectures for indoor positioning applications.
105

Návrh a realizace modulu optického přijímače pro VLC aplikace / Design and realization of an optical receiver module for VLC purposes.

Grygar, Josef January 2017 (has links)
This work is focused on free space optical communication in visible electromagnetic spectrum known as visible light communication (VLC). Basic parameters of standard IEEE 802.15.7, advantages and disadvantages are discussed in the theoretical part of this work. Furthermore, optical link and it´s parts are described. The largest part of the work is focused on design and simulation of optical receiver for visible spectrum. Selection of component, noise and SNR calculation is discussed as well. This work also includes calculation of power energy in different parts of optical connection, PCB design of optical receiver, transmitters and power supply and output board. Behavior and parameters of electronic circuits, components and optical connection are explored, measured and compared with theoretical values.
106

Design and Development of Homogeneous Photosystems Based on Heteroleptic Cu(I) Photosensitizers for Solar Hydrogen Production

Saeedi, Sima 24 May 2022 (has links)
No description available.
107

Mesure de distance et transmission de données inter-véhicules par phares à LED / Vehicle-to-Vehicle Visible Light Range-Finding and Communication Using the Automotive LED Lighting

Bechadergue, Bastien 10 November 2017 (has links)
En réponse aux problèmes croissants liés aux transports routiers - accidents, pollutions,congestions - les véhicules à faibles émissions, équipés de systèmes de transports intelligents (ITS)sont progressivement développés. Si la finalité de cette démarche est le véhicule entièrementautonome, on peut néanmoins s'attendre à voir d'abord sur nos routes des véhicules automatisés surdes phases de conduite spécifiques. C'est le cas du convoi automatisé, qui permet à plusieursvéhicules de rouler en convois de manière automatique et donc d'augmenter la capacité des voies decirculation tout en réduisant la consommation de carburant. La fiabilité de cet ITS repose surplusieurs briques technologiques, et en particulier sur la mesure de distance et la transmission dedonnées véhicule-véhicule (V2V).De nombreux systèmes permettent de réaliser ces deux fonctions vitales comme, par exemple, lesradars ou lidars pour la mesure de distance et la technologie IEEE 802.11p pour la communicationvéhiculaire. Si ces différents dispositifs présentent de très bonnes performances, ils sont néanmoinsparticulièrement sensibles aux interférences, qui ne cessent de se multiplier à mesure que le nombrede véhicules équipés augmente et que le trafic est dense. Pour pallier les dégradations deperformances induites par de telles situations, des technologies complémentaires pourraient donc êtreutiles. Le récent développement des diodes électroluminescentes (LED) blanches, en particulier pourl'éclairage automobile, a permis l'émergence des communications optiques visibles sans fil (VLC).Les phares à LED sont alors utilisés pour transmettre des données entre véhicules et avec lesinfrastructures. Malgré la puissance limitée de ces éclairages, plusieurs études ont montré qu'unetransmission de qualité est possible sur quelques dizaines de mètres, faisant de la VLC uncomplément particulièrement intéressant à l'IEEE 802.11p, en particulier pour les convoisautomatisés. Par analogie, on peut alors se demander si les phares ne pourraient pas être aussi utiliséspour mesurer la distance V2V.Le but de cette thèse est donc de proposer et évaluer un système dédié aux situations de convoisautomatisés qui, à partir des phares avant et arrière des véhicules, transmet des données et mesuresimultanément la distance V2V. Dans un premier temps, une étude détaillée de l'état de l'art de laVLC pour la communication V2V est effectuée afin de déterminer l'architecture de base de notresystème. La fonction de mesure de distance est ensuite ajoutée, après une revue des différentestechniques usuelles. Une fois l'architecture générale du système établie, elle est dans un premiertemps validée par des simulations avec le logiciel Simulink. En particulier, les différents paramètressont étudiés afin de déterminer leur impact sur la résolution de mesure de distance et les performancesen transmission de données, puis afin de les optimiser. Si ces simulations fournissent des indicateursimportants pour la compréhension du système, elles ne peuvent cependant remplacer les tests d'unprototype réel. L'implémentation de ce prototype est alors détaillée ainsi que les tests réalisés dansdifférentes configurations. Ces différents tests démontrent l'intérêt des solutions proposées pour lamesure de distance et la communication V2V en convois automatisés. / In response to the growing issues induced by road traffic - accidents, pollution, congestion- low-carbon vehicles equipped with intelligent transportation systems (ITS) are being developed.Although the final goal is full autonomy, the vehicles of the near future will most probably be selfdrivingin certain phases only, as in platooning. Platooning allows several vehicles to moveautomatically in platoons and thus to increase road capacity while reducing fuel consumption. Thereliability of this ITS is based on several core technologies and in particular on vehicle-to-vehicle(V2V) distance measurement and data transmission.These two vital functions can be implemented with several kinds of systems as, for instance, radars orlidars for range-finding and IEEE 802.11p-based devices for vehicular communication. Althoughthese systems provide good performances, they are very sensitive to interferences, which may be agrowing issue as the number of vehicles equipped will increase, especially in dense traffic scenario.In order to mitigate the performance degradation occurring in such situations, complementarysolutions may be useful. The recent developments of white light-emitting diodes (LED), especiallyfor the automotive lighting, has allowed the emergence of visible light communication (VLC). WithVLC, the vehicle headlamps and taillights are used to transmit data to other vehicles orinfrastructures. Despite the limited optical power available, several studies have shown thatcommunication over tens of meters are possible with a low bit error rate (BER). VLC could thus bean interesting complement to IEEE 802.11p, especially in platooning applications. By analogy, onecould wonder if the automotive lighting can also be used for V2V range-finding.The goal of this thesis is thus to propose and evaluate a system dedicated to platooning configurationsthat can perform simultaneously the V2V distance measurement and data transmission functionsusing the headlamps and taillights of the vehicles. The first step of this study is thus a detailed stateof-the art on VLC for V2V communication that will lead to a first basic architecture of our system.Then, the range-finding function is added, after a careful review of the classical techniques. Once thegeneral architecture of the system is drawn, it is validated through simulations in the Simulinkenvironment. The different degrees of freedom in the system design are especially studied, in orderfirst to evaluate their impact on the measurement resolution and the communication performances,and then to be optimized. Although these simulations provide crucial keys to understand the system,they cannot replace real prototype testing. The implementation of the prototype is thus fullydescribed, along with the results of the different experiments carried out. It is finally demonstratedthat the proposed solution has a clear interest for V2V range-finding and communication inplatooning applications.
108

Tailoring Biomass for Light Active Compounds and Materials

Singathi, Ravichandranath 06 August 2020 (has links)
No description available.
109

Composite Nanostructures as Effective Catalysts for Visible-Light-Driven Chemical Transformations

Rasamani, Kowsalya Devi, 0000-0002-1717-1426 January 2020 (has links)
The development of nanoscale heterostructure photocatalysts for the effective, direct utilization of visible light (400-750 nm, ~44% of solar spectrum) to drive important chemical conversions is a prime research area in the field of photocatalysis. Particles at nanoscale dimensions have a large surface area-to-volume ratio, expose a high number of active surface sites, and exhibit unique electronic properties (different from bulk) that are beneficial for improving the overall catalytic activity. However, the advantages of size reduction are often overshadowed by the low optical absorption (as absorption power  size3) and colloidal instability (extensive aggregation) of particles at the nanoscale. In this dissertation, we demonstrate a strategy to improve the colloidal stability and enhance the optical absorption of nano-sized semiconductor and metal nanoparticles (NPs) that exhibit weak visible light absorption. The colloidal, free-standing NPs are placed on transparent, dielectric silica nanospheres (SiOx NSs) that act as optical antenna supports, forming SiOx/NP composite nanostructures. The spherical morphology of SiOx enables scattering resonances (Fabry Perot or Whispering Gallery Modes) which enhances the local electric field on or near the surface of the NS. The NPs placed on the surface of SiOx NS interact with the locally enhanced electric field and exhibit improved optical absorption. By varying the size of the SiOx NS, the resonance wavelengths and the intensity of the local electric field enhancement can be tuned, offering the ability of such structures to effectively utilize a wide range of energies in the visible region. Composite nanostructures comprised of various classes of nanomaterials such as metal-doped semiconductor, plasmonic, and non-plasmonic metal NPs were investigated to perform the desirable solar-to-chemical transformations. First, we employed SiOx-loaded silver-doped silver chloride (SiOx/AgCl(Ag)) photocatalyst to investigate the role of metal-induced gap states in AgCl, a wide bandgap semiconductor. SiOx/AgCl(Ag) exhibit high catalytic performance and photostability after 10 cycles of the probe reaction, methylene blue (MB) degradation under visible light irradiation. The results indicate that the visible light absorption due to metal-induced gap states can be further improved by employing the SiOx NSs as supports that act as optical nanoantenna. We then studied the influence of NP size on the catalytic activity to understand the effect of size in promoting the generation and transfer of hot electrons to surface adsorbates. Our findings indicate that upon employing Ag NPs of different particle size (<10 nm and >10 nm) and normalizing for the optical absorption and moles of surface Ag atoms, the efficient generation and transfer of photoexcited hot electrons is favored in the small-sized Ag NPs (size <10 nm) than bigger Ag NPs. Next, we investigated the selective partial hydrogenation of nitroarene to N-aryl hydroxylamine using SiOx-loaded platinum (SiOx/Pt) photocatalysts. We found that change in the surface electronic structure of the small Pt NPs (size <5 nm) due to light illumination and surface modification (by adding suitable organic ligands), minimize the adsorption of the electron-rich hydroxylamine molecules and minimize their complete conversion to aniline, resulting in high N-hydroxylamine selectivity. Overall, our work shows that well-controlled composite nanostructures comprising of active catalyst loaded on dielectric SiOx NS supports that act as optical nanoantenna are a promising class of photocatalysts for driving photon-to-chemical transformations with high activity and product selectivity. / Chemistry
110

Production of New Carbon-Heteroatom Bonds Induced by Visible Light

Herrera Luna, Jorge Carlos 05 January 2023 (has links)
[ES] En la presente tesis doctoral se describen metodologías novedosas, simples y rápidas con luz visible para producir compuestos con nuevos enlaces C-heteroátomo como C-B, C-P y C-S que representan estructuras valiosas en la síntesis orgánica moderna. La luz visible se emplea como fuente de energía más suave y sostenible que la tradicional (energía térmica). Por otro lado, también se han empleado nanorreactores espaciales como las redes de gel viscoelástico mediante enfoques 'ascendentes' para mejorar diferentes procesos en comparación con la disolución, en términos de cinética, selectividad o procesabilidad. Por lo tanto, el Capítulo 3 describe un procedimiento novedoso, directo y rápido para producir tiofenos que contienen boro empleando luz visible en disolución anaeróbica sin el uso de ningún fotocatalizador externo. Este estudio se ha ampliado a la borilación de haluros de heteroareno comerciales en condiciones aeróbicas en un nanorreactor de gel fácil de usar (Capítulo 4). La red de gel proporciona un microambiente estabilizador adecuado para soportar una amplia gama de sustratos, incluidos los ésteres de boronato de furano, tiofeno, selenofeno y de pirrol. El Capítulo 5 se centra en una nueva estrategia para lograr una fosforilación aeróbica eficiente de heteroarenos de cinco miembros mediante catálisis fotorredox dicromática en un nanorreactor basado en gel. La metodología, que opera mediante un mecanismo de transferencia de electrones fotoinducida consecutiva (ConPET), se ha aplicado con éxito a la síntesis sencilla y limpia de varios fosfonatos de heteroareno diferentes (furano, tiofeno, selenofeno, pirrol, oxazol o tioxazol), extendiéndose a la etapa tardía de la fosforilación del anticoagulante rivaroxabán. Por último, el Capítulo 6 muestra una tiolación (formación enlaces C-S) simple y efectiva, libre de metales, de haluros de heteroareno comerciales usando luz visible. Los resultados experimentales son consistentes con una reacción basada en un complejo aceptor-donador de electrones (EDA) entre una alquilamina y el haluro de heteroareno. El mecanismo del proceso se ha demostrado mediante estudios espectroscópicos, mientras que la robustez se ha demostrado mediante experimentos a escala de gramo y derivatización de última etapa. / [CA] En la present tesi doctoral es descriuen metodologies noves, simples i ràpides amb llum visible per a produir compostos amb nous enllaços C-heteroàtom com C-B, C-P i C-S que representen estructures valuoses en la síntesi orgànica moderna. La llum visible s'utilitza com a font d'energia mes suau i sostenible que la tradicional (energia tèrmica). D'altra banda, també s'han emprat nanorreactors espacials com les xarxes de gel viscoelàstic mitjançant enfocaments 'ascendents' per a millorar diferents processos en comparació amb la dissolució, en termes de cinètica, selectivitat o procesabilitat. Per tant, el Capítol 3 descriu un procediment nou, directe i ràpid per a produir tiofens que contenen bor emprant llum visible en dissolució anaeròbica sense l'ús de cap fotocatalitzador extern. Aquest estudi s'ha ampliat a la borilació d'halurs d'heteroaré comercials en condicions aeròbiques en un nanorreactor de gel fàcil d'usar (Capítol 4). La xarxa de gel proporciona un microambient estabilitzador adequat per a suportar una àmplia gamma de substrats, inclosos els èsters de boronat de furan, tiofé, selenofé i de pirrol. El Capítol 5 se centra en una nova estratègia per a aconseguir una fosforilació aeròbica eficient de heteroarens de cinc membres mitjançant catàlisis fotorredox dicromàtica en un nanorreactor basat en gel. La metodologia, que opera mitjançant un mecanisme de transferència d'electrons fotoinducida consecutiva (ConPET), s'ha aplicat amb èxit a la síntesi senzilla i neta de diversos fosfonats d'heteroaré diferents (furan, tiofé, selenofé, pirrol, oxazol o tioxazol), estenent-se a l'etapa tardana de la fosforilació de l'anticoagulant rivaroxabán. Finalment, el Capítol 6 mostra una tiolació (formació d'enllaços C-S) simple i efectiva, lliure de metalls, d'halurs d'heteroaré comercials usant llum visible. Els resultats experimentals són consistents amb una reacció basada en un complex acceptor-donador d'electrons (EDA) entre una alquilamina i l'halur d'heteroaré. El mecanisme del procés s'ha demostrat mitjançant estudis espectroscòpics, mentre que la robustesa s'ha demostrat mitjançant experiments a escala de gram i derivatització d'última etapa. / [EN] This thesis doctoral describes novel, simple, and rapid methodologies using visible light to produce compounds with new C-heteroatom bonds such as C-B, C-P and C-S that represent valuable scaffolds in modern organic synthesis. The employment of visible light as energy source highlights the concepts of green and sustainable chemistry considering its mild, safe, and eco-friendly advantages. On the other hand, spatially nanoreactors such as viscoelastic gel networks by 'bottom-up' approaches to improve different processes in comparison to solution, in terms of kinetics, selectivity or processability have been also developed. Thus, Chapter 3 describes a novel, straightforward, and fast procedure to produce boron-containing thiophenes employing visible light in anaerobic solution. Interestingly, the process does not require the use of any external photocatalyst. This study has been extended to the borylation of commercially available heteroarene halides under aerobic conditions in an easy-to-use gel nanoreactor (Chapter 4). The gel network provides an adequate stabilizing microenvironment to support wide substrate scope, including furan, thiophene, selenophene, and pyrrole boronate esters. Chapter 5 focus on a new strategy to achieve efficient aerobic phosphorylation of five-membered heteraroenes using dichromatic photoredox catalysis in a gel-based nanoreactor. The methodology, which operates by a consecutive photoinduced electron transfer (ConPET) mechanism, has been successfully applied to the straightforward and clean synthesis of a number of different heteroarene (furan, thiophene, selenophene, pyrrole, oxazole, or thioxazole) phosphonates, extending to the late-stage phosphonylation of the anticoagulant rivaroxaban. Lastly, regarding the construction of new C-S bonds, Chapter 6 shows a simple and effective metal-free thiolation of commercial heteroarene halides using visible light. The experimental results are consistent with the reaction taking place from an electron donor-acceptor (EDA) complex between an alkylamine and the heteroarene halide. Mechanistic aspects of the whole process have been demonstrated by spectroscopic measurements whereas the strength of this novel method has been proven by gram-scale experiment and late-stage derivatization. / Herrera Luna, JC. (2022). Production of New Carbon-Heteroatom Bonds Induced by Visible Light [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/191051

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