In this doctoral thesis, we have studied the oxidation of carboxylic acids to obtain the corresponding acyloxy radicals, using visible light and non-toxic and inexpensive organic dyes, as photocatalysts. On the one hand, we study the photooxidation of aromatic carboxylic acids to obtain acyloxy radicals, whose decarboxylation is relatively slow (Chapter I and Chapter II). On the other hand, we describe the photooxidation of aliphatic carboxylic acids, to take advantage of the rapid decarboxylation of the corresponding acyloxy radicals, to generate nucleophilic radicals that were trapped by different reagents (Chapter III to Chapter V). It should be noted that all the protocols are free of expensive and toxic noble metals, the reactions were promoted with visible light at room temperature and the scalability of some reactions was demonstrated in batch conditions or using flow chemistry. In addition, mechanistic studies were carried out to propose plausible photocatalytic routes to all the reactions studied.

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The rapidly increasing demands for high data-rate applications and the growth of wireless devices connected to the internet overcrowded the radio frequency spectrum. This necessitates researchers to examine higher frequencies for wireless communication. Recently, visible light communication (VLC) has received significant attention as a viable solution to complement the RF technologies, thanks to the abundant unregulated/unlicensed spectrum it occupies while utilizing the existing lighting infrastructure. However, due to the physical properties of light, the signal cannot penetrate through obstacles, and the VLC system heavily relies on the existence of a line-of-sight (LoS) link between VLC transmitters and receivers. Optical reconfigurable intelligent surfaces (RISs) are recently proposed with the ability to dynamically control the wireless channel, which offers opportunities to enhance the VLC system performance by exploiting the non-LoS components of the VLC link. In this thesis, we highlight the recent developments in optical RISs and the various reflection characteristics they provide for the incident optical beams. Then, we investigate RIS-assisted VLC systems for both indoor and outdoor setups. Firstly, in indoor VLC systems, we study multi-user RIS-assisted VLC systems while considering specular and diffuse reflecting RISs. As the channel gain varies significantly between users in VLC systems, a large gap in performance is observed between users. We aim to maximize the VLC system achievable sum rate while ensuring network fairness. We formulate multi-objective optimization problems for both specular and diffuse reflecting RISs and propose a solution utilizing low complex genetic algorithm (GA) and particle swarm optimization (PSO). We highlight the advantages provided by the proposed algorithms in terms of achievable sum rate and network fairness performance. In addition, we assess the link outage ratio for specular reflecting RISs and assess the gains provided by diffuse RISs while considering an environment with mobile users. Secondly, in the context of outdoor VLC systems, we provide an overview of outdoor RIS-assisted VLC systems. In particular, we highlight the benefits of optical RISs to mitigate LoS blockage and VLC transceivers misalignment. More specifically, we focus on RIS-assisted unmanned aerial vehicles (UAVs)-based VLC, RIS-assisted vehicular VLC, and RIS-assisted streetlight-based communication. In addition, we highlight the use of RISs to support VLC outdoor-to-indoor communications.

With the huge development of semiconductor lighting technologies, the light emitting diodes (LEDs) are promising technology that eventually replacing traditional incandescent and fluorescent lamps for their high power efficiency, environmental friendliness and long predicted product lifetime. Besides lighting, the advent of high-brightness, fast-switching LED lamps has facilitated LED Communication as a new form of Optical Wireless Communication (OWC) in the visible light spectrum. This thesis study model characteristics of LED communication for indoor optical environment. Based on Matlab and SPICE, an electrical and optical LED communication model is proposed to describe light power's conversion and propagation. In details, our models include (1) models for V-I characteristics and fro small signal behavior, (2) electro-electrical conversion and emitting, (3) optical channel with path loss and noise, (4) receiving model. Moreover, a test and measurement platform for LED communication has been established to validate the proposed model. A case of study on light power distribution within 30cmX30cmX10cm in line-of-sight was implemented by measuring for comparing the theoretical simulation and experimental results. Depending on our model and the case of study, we carried out an inspection of the LED communication performance using On-Off Keying (OOK) signals and a 500 kbps transmission data rate under 10e-3 BER was achieved in our lab.

Microplastic (MP) pollution has recently been recognized as a threat to the biosphere including humans due to its widespread distribution, persistent nature and infinitesimal size. This study focused on the solid phase degradation of microplastic residues (particularly low density polyethylene, LDPE) in water through heterogeneous photocatalysis process by designed photocatalysts of zinc oxide nanorods (ZnO NRs) and platinum nanoparticles deposited on zincoxide nanorods (Pt NPs-ZnO NRs) under visible light irradiation. These photocatalysts were assessed following standard protocol (ISP 10678: 2010), and characterized using SEM, EDX andoptical spectroscopies (UV-VIS and PL). Deposition of Pt-NPs on ZnO NRs for certain minutes has been found optimum that enhanced the photodegradation process about 38% under UV irradiation and 16.5% under visible light irradiation by improving of both electrons-holes pair separation process and visible light absorption. Photocatalytic degradation of LDPE films was confirmed by FTIR spectroscopy, dynamic mechanical analyzer (DMA), optical and electron microscopes. When LDPE film irradiated in presence of Pt-ZnO, degradation was found quicker than ZnO alone of similar concentration which exhibited formation of a large number of wrinkles, cracks and cavities on the film surface. Dynamic mechanical analyzer (DMA) test indicated stiffness and embrittlement of exposed LDPE films in presence of photocatalysts. Thus, the present work provides a new insight about modified catalysts for the degradation of microplastics in water using visible light.

Connected Vehicle (CV) is a motorized vehicle that can communicate with its interior and exterior surroundings. Connected Vehicle focuses on localized vehicle-to-vehicle (V2V) and vehicle-to-infrastructure (V2I) to support safety, mobility and environmental applications. In this work, a simulation framework is presented. The framework quantifies Connected Vehicle performance in a forward collision warning situation. The simulation framework evaluates the performance using a vehicular traffic simulator with data from an intersection in Toronto, ON Canada. Various communication methodologies are evaluated at different Connected Vehicle market penetration rates. While DSRC is an interference limited communication methodology and visible light communications is a line-of-sight communication, the combination of both is evaluated to quantify the vehicular network safety performance in terms of time to collision. The performance of DSRC in a vehicular network is quantified in an interference dominant environment and the VLC performance in the vehicular network is evaluated at different weather conditions. In a specific vehicular traffic situation namely for- ward collision warning, this research quantified the VLC performance improvement in vehicular network safety to be 11% in addition to DSRC.This work concludes with the simulation and prototyping of camera communications for vehicular applications. Specifically this thesis presents multiple input / multiple output camera communications link utilizing a luminary array as a transmitter and two orthogonal low cost rolling shutter cameras as a receiver with the purpose of increasing the achievable data rate with one camera. This work has demonstrated that there is at most a doubling in the data rate using two cameras over a single one. This data rate increase is achievable using a specific camera setup namely orthogonal cameras. / Thesis / Master of Applied Science (MASc)

This doctoral thesis focuses on applying different organocatalysts in several enantioselective reactions and aerobic photooxidations using visible light. Chapter 1 describes using a chiral primary amine-salicylamide derived from (1R,2R)-cyclohexane-1,2-diamine as chiral organocatalyst in the asymmetric conjugate Michael addition of aldehydes and ketones to maleimides, giving the corresponding enantioenriched succinimides. The same organocatalyst is used in the enantioselective Michael addition of aldehydes to nitroalkenes, yielding enantiopure γ-nitroaldehydes. Furthermore, these Michael additions of aldehydes to maleimides and nitroalkenes are carried out employing sustainable and environmentally friendly deep eutectic solvents (DES), being able to reuse the catalytic system for several cycles. Chapter 2 describes using a chiral primary-amine monocarbamate derived from (1R,2R)-cyclohexane-1,2-diamine as chiral organocatalyst in the enantioselective α-amination of aldehydes with azodicarboxylates, obtaining the corresponding α,α-disubstituted aldehydes with the absence of solvent under mild conditions. This simple orgacatalytic system’s applicability is demonstrated by preparing a chiral oxazolidinone precursor of amino acids. The reaction is also successfully scaled-up. In addition, theoretical calculations were performed to demonstrate how the absolute configuration of the final adducts is produced. Chapter 3 shows how riboflavin tetraacetate, a cheap vitamin B2 derivative, is an appropriate metal-free photocatalyst in the aerobic photooxidation of xanthenes, thioxanthenes and dihydroacridines under visible light irradiation. / This research work has been possible thanks to funding from the Spanish Ministerio de Economía y Competitividad (PGC2018-096616-B-100, CTQ201788171-P), the Generalitat Valenciana (AICO 2021/013) and the University of Alicante (VIGROB-173). The author wishes to express his gratitude to the Institute of Organic Synthesis for a research contract (I-PI/21-20) and to the University of Alicante-Banco Santander consortium for a grant to spend a three-months research period in the Chemistry Interdisciplinary Project research center (ChIP) of the University of Camerino (Italy) under the supervision of Dr. Matteo Tiecco.

Visible-light communication (VLC) has several advantages over the commonly used radio frequency (RF) spectrum, including high bandwidth and low crosstalk. These features have become of more significance, especially as the proliferation of wireless devices increases and causes spectrum crowding. The white light in VLC systems is typically obtained from blue/violet light-emitting diodes (LEDs) and phosphors partially converting blue light into longer wavelength colors spanning the visible-light band. One phosphor that is frequently used is cerium-doped yttrium aluminum garnet (YAG). However, YAG suffers from a low color-rendering index (CRI) and high correlated color temperature (CCT). Lead halide perovskites provide an alternative to YAG and have been extensively utilized for optoelectronic devices owing to their tunable bandgap and high photoluminescence quantum yield (PLQY). However, their drawbacks, e.g., lead toxicity and instability, hinder their widespread application. Herein, in order to take advantage of a high-performance lead-free tin-based halide perovskite phosphor that has a high absolute PLQY of near unity and a wide spectral emission ranging from 500 to 700 nm, we fabricated ultraviolet (UV) micro light-emitting diodes (micro-LEDs) with a peak wavelength at 365 nm to match the peak of the photoluminescence excitation (PLE) spectra of the material to obtain strong yellow-spectrum emission. Together with a blue LED, white light was obtained with a CRI of 84.9 and 4115-K CCT. Despite the long PL lifetime of the perovskite material, which is in the order of μs, a net data rate of 1.5 Mb/s was achieved using orthogonal frequency-division multiplexing (OFDM) with adaptive bit and power loading to take advantage of the exceptionally high PLQY of the phosphor to improve the data throughput of the VLC system using higher modulation orders. Furthermore, through improvements to the nanostructure of lead-free tin-based halide perovskite phosphor and the use of excitation sources with a higher power, the data rate is expected to be even higher. The lead-free nature of this material, along with its wide spectrum and high conversion efficiency, makes it a promising alternative to conventional toxic perovskite-based phosphors. As the first demonstration of VLC links using lead-free perovskite, this study paves the way for safer, more sustainable VLC systems.

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