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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Philosophiae Doctor - PhD / Fossil fuels are part of fuels that are formed from natural processes and they are called non-renewable sources of energy. These include natural gas, coal and oil. They have been used for decades to produce energy globally. However, there are some factors that related with the use of fossil fuels which results in an increase in the requirement of large amounts of energy. In addition, the use of fossil fuels as energy source has a negative impact on the environment and they cannot be reused. It is expected that at some point they will run out. Thus, a need for a renewable, clean and plentiful source of energy is urgent. Solar energy is one of the energy sources that may overcome fossil fuel drawbacks.

Solved area is located in the center of Vyškov and is directly connected to the square. It forms one end of the chip Square. The proposal was to create a dominant object, which will close the square and end with the visual axis, which in recent years is not very flattering. The building would be dominant, but only so that did not compete with dominant main square, with the town hall. At the same time the goal was to design a functional building, which, thanks to the cartridge housing, shops and bring more people into the center and revive him.

Many new instrumentation and different instrumental techniques have been developed to deal with increasing complexity of samples encountered. Many researchers also have coupled these instrumental techniques with chemometric algorithms to assist in the quantitative analysis of multi-component samples in the hope of alleviating the need of tedious separation and cleanup procedures. These newer chemometric procedures tend to be complex and difficult to understand and implement and are successful under different circumstances and conditions. In this study, we start from the very simple beginning and examine the factors that can present difficulties with obtaining the correct results and observe how the system behaves so as to find a better and simpler chemometric procedure to perform mixture quantitative analysis. We have used simulated and actual experimental data obtained from a UV-VIS spectrophotometric measurement of metal complexes to conduct the study. Well understood and defined systems tend to give good results. The main obstacle has been, and still is, interferences in spectral information one gets from the measurement.

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.

Hydrogen is a vital component in several different chemical reactions as well as a potential fuel source for the future. The water gas shift (WGS) reaction converts CO and water to hydrogen and CO2. The objective of this work is to first, characterize the potential benefits of the addition of lanthanum oxide (lanthana) to the iron-chromium-copper (Fe-Cr-Cu) oxide catalysts industrially used in high temperature water gas shift processes, and second, analyze these catalysts using in-situ UV-Visible spectroscopy. The benefits of each component in the catalyst are discussed as well as potential benefits from the addition of lanthana. Lanthana is a rare earth oxide that dramatically increases the surface area of the iron based WGS catalysts, and small concentrations of other rare earth oxides (i.e. cerium) have been shown to increase the rate of desorption of CO2 from iron surfaces (Hu Yanping 2002). Lanthana has similar chemical properties to other rare earth oxides tested and has not been previously tested as an additive to the WGS catalyst. Therefore catalysts with 0, 1, 2, 5, 10, and 20 wt% lanthana were made via a co-precipitation method in order to measure changes in activity, physical stability, and thermal stability. Catalyst characterization techniques utilized include electron dispersive X-ray spectroscopy (EDX), temperature programmed reduction (TPR) with hydrogen, and nitrogen physisorption (BET). The kinetic analysis was performed utilizing both mass spectroscopy (MS) and gas chromatography (GC). The addition of 1 wt% lanthana to the Fe-Cr-Cu catalysts increases WGS reaction rates of the catalyst at 425°C and 350°C, however the 0% La catalyst has the highest rates at 375°C and 400°C. The 0% La catalyst shows significant drop off in rate at 425°C, suggesting that the lanthana provides a small thermal stabilizing, i.e. the addition of lanthana prevents catalyst sintering at higher temperatures. Traditionally, chromia acts as the sole thermal stabilizer in these catalysts. The addition of large amounts of lanthana inhibits the chromia stabilizing effect, however small additions of lanthana appear to have an additional catalyst promotional effect without interfering with the chromia thermal stabilization. The increased WGS reaction rates at higher temperatures could allow for greater throughput of reactants in industrial settings. Higher concentrations of lanthana decrease the activity due to what is believed to be disruption of the chromia stabilizing effect as well as reduced amount of the active phase of catalyst. In-situ UV-Visible analysis shows that the oxidation state of the iron in the catalyst has a direct correlation to the UV-Visible light absorbance of the surface of the iron catalyst. Extent of reduction is traditionally measured with a synchrotron which is significantly more expensive than UV-Vis spectroscopy. This study uses the more economical UV-Vis spectrometer to determine similar information. The lanthana doped catalysts show an over-reduction of iron during WGS conditions (i.e. rapid reduction of Fe2O3 to Fe3O4 and FeO).

The structural and functional roles of lanthana in unsupported iron-based catalysts for the high-temperature water-gas shift reaction and Fischer-Tropsch synthesis were investigated. The performance of the catalysts with varying lanthana contents was based on their activity, selectivity, and stability. With regard to the former reaction, extent of reduction of the iron in Fe2O3/Cr2O3/CuO/La2O3 water-gas shift catalysts is a key parameter that was characterized using UV-visible spectroscopy. Minor addition of lanthana (<0.5 wt%) produces more active and stable catalysts apparently because it stabilizes the iron-chromium spinel, increases the surface area of the reduced catalysts, enhances the reduction of hematite to the magnetite active phase, and facilitates the adsorption of CO on the surface of the catalyst modeled by an adsorptive Langmuir-Hinshelwood mechanism. Statistical 95% confidence contour plots of the adsorption equilibrium constants show that water adsorbs more strongly than CO, which inhibits the reaction rate. A calibration curve that correlates the oxidation state of surface iron domains to normalized absorbance of visible light was successfully generated and applied to the water-gas shift catalysts. UV-visible studies indicated higher extent of reduction for surface Fe domains for the catalysts promoted with 1 wt% of lanthana and showed potential to be a more convenient technique for surface chemistry studies than X-ray absorption near edge spectroscopy (XANES). Lanthana addition to iron-based Fischer-Tropsch catalysts enhances the olefin-to-paraffin ratio, but decreases their activity, stability, and selectivity to liquid hydrocarbons. Adding lanthana at the expense of potassium reduces the water-gas shift selectivity and enhances the activity and stability of the catalysts. Finally, a model that simulates heat and mass transfer limitations on the particle scale for the Fischer-Tropsch reaction applicable at lab-scale suggests optimal operating and design conditions of 256°C, 30 bar, and 80 mirons are recommended for higher selectivity to liquid hydrocarbons. The model considers pressure drop, deactivation, pore diffusion, film heat transfer, and internal heat transfer when solving for the optimal conditions, and maps them as functions of design variables. This model can be up-scaled to provide guidance for optimal design of commercial-size reactors.

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.