Photocatalysis is a robust synthetic tool capable of breaking and assembling chemical bonds using single electron chemistry. This is achieved through the catalytic conversion of light energy to chemical energy in situ, such that the photons being delivered are themselves reagents. Herein, an inexpensive and environmentally-benign platform for scaling up photocatalytic reaction is disclosed, harnessing blue light naturally emitted by deep-sea bioluminescent bacteria. Photobacterium angustum GB-1 was demonstrated to photoexcite both polypyridyl organometallic chromophores and organic dyes at short molecular distances, enabling photocatalysis without any external energy-consuming lamps.While improving the eco-friendliness of photocatalysis itself, we also present a method to use photocatalysis for environmental remediation. Using visible light, a nontoxic organic photosensitizer, and oxygen, we demonstrate the controlled oxidative depolymerization of polystyrene—including polystyrene retrieved from waste receptacles in Havemeyer—to acetophenone. This method is based on results obtained in the controlled aerobic deannulation of cycloalkanes, which is also discussed herein. Lastly, a means by which catalysis itself can be made more cost, resource, and time effective is presented. An innovative computational platform in development predicts new catalysts for reactions currently energetically inaccessible. In collaboration with the developers, we present experimental validation of their theoretical predictions, as well as perform the synthesis of a de novo fluorinated thiazolium precatalyst calculated to significantly lower the energetic barrier of an otherwise energetically prohibitive Stetter reaction.

The aim of this paper is to summarize and evaluate properties of polymers modified modified mortar, their durability and the possibility of surface treatment. Recently, the requirements for additional surface treatment of architectonal concrete are increased and the application of polymer-modified mortar can accelerate and simplify the realization of visible concrete. Polymer-modified mortar with the addition of powder photocatalysts can significantly reduce and thus increase the availability of photoactive concrete structures. The experimental part deals with the addition of photocatalyst to the polymer-modified mortar and the subsequent assessment of the photocatalytic properties, the possibility of modification cement mortars with anorganic pigments and the application of transparent coatings for the enhancement of color saturation and resistance.

This diploma thesis deals with photoelectrochemical cells containing photoactive titanium dioxide anode and their use for photocatalytic degradation of organic compound from water solutions. The electrical properties of the produced photoelectrochemical cells were determined by the use of voltamperometric characteristics, the oxidation ability of the cells was monitored by measuring the fluorescence of the oxidative intermediates. To study these reactions, benzoic acid was used as the fluorescence probe for OH˙ radicals. The aim of the study was to study the influence of material composition and spatial arrangement of the cathode and the relationship between irradiation, current and rate of electrode processes.

The diploma thesis deals with photocatalytic degradation of organic polutants on water- suspended UV activated anatase particles. The measurements are executed on a pilot plant UV photoreactor and the aim the thesis is to figure out the time course of azo dyes degradation under different photoreactor settings and subsequently infer the effectivity of the photoreactor under different settings. The degree of the aze dyes degradation is evaluated via UV-VIS spectrometry.

This work deals with the optimization of the preparation process of WO3 photoanodes nad their characterization. For compositions were prepared, which were applied to a substrate via spin-coating process and subsequently annealed at 450 °C. The length of milling of precursor particles contained in the coating formulations determined properties of deposited layers. were examined for. The additivity of the individual compositions was also observed. The structure of the layers was observed by optical microscopy and scanning electron microscopy (SEM), their composition by the X-ray diffraction (XRD) and their thickness and surface roughness was defined by contact profilometry. Photoelectrochemical properties of the prepared layers were also investigated by linear voltametry and chronoamperometry.

V této práci byl popsán princip fotokatalýzy. Práce se soustřeďuje na kovové oxidy, které mají široké využití ve fotokatalytických aplikacích. Bylo také popsáno různé použití fotokatalytických materiálů. Tato práce se zaměřuje zejména na využití fotokatalytických materiálů pro rozklad organických vodu znečisťujících látek. Popsaný fotokatalyzátor je oxid měďný, který má velmi dobré vlastnosti pro rozklad organických látek pomocí fotokatalýzy. Schopnost rozkladu organických látek oxidu měďného byla popsána na rozkladu organického barviva methylová oranž.

Water pollution is a major environmental issue, which mankind is facing in modern times. Pollutants (especially dyes, antibiotics and bacteria) released by human activity into wastewater are harmful to humans, animals and water bodies. Therefore, it is urgent to remove these pollutants from wastewater. Amongst conventional wastewater tertiary treatment techniques, there are adsorption and advanced oxidation processes (AOPs) including photocatalysis. These two methodologies can have important benefit from the use of nanomaterials. Despite the plethora of reports about adsorption or photocatalysis for wastewater treatment, there are still some issues in this field, i.e.: (1) In photocatalysis, one of the most common photocatalysts, titanium dioxide (TiO2), has been widely used to degrade organic pollutants in water, but it has the limitation to be operated by ultraviolet (UV) light and, therefore, by means of a non-sustainable and high associated cost methodology. (2) Most of the literature presented one material to remove only one kind of pollutant at a time. However, as we all know, wastewater is a complex matrix comprising several species. (3) Most researchers have used only one technique, e.g. adsorption or photocatalysis, to treat wastewater. However, adsorption or photocatalysis has its own limitations, which may be overcome by their combined use. Only few researchers combined adsorption and photocatalysis for wastewater treatment and this field is still in its infancy. (4) Few research reports deal with nanocomposites simultaneously possessing antibacterial activity and the ability to remove organic pollutants of different chemical composition and properties, such as dyes and antibiotics. (5) After wastewater treatment, the recovery and the reuse of the photocatalytic materials used as slurry photocatalysts are generally problematic. The aim of this thesis is to tackle some of these issues by developing new multifunctional nanocomposites capable of removing different kinds of pollutants – namely dyes, antibiotics and bacteria – from wastewater through a sustainable and cost-effective treatment. Moreover, the new nanocomposites will have to be easy to recover and reusable. In this context, different kinds of polymer-based magnetic nanocomposites comprising a core of Fe3O4/poly(N-isopropylacrylamide-co-methacrylic acid) (Fe3O4/P(NIPAM-co-MAA)) microspheres were prepared. To reach this aim, the different kinds of nanomaterials to be combined in the composites were synthesized and thoroughly studied. The first material is silver-titanium dioxide nanoparticles (Ag-TiO2 NPs), which were prepared by synthesizing Ag NPs on the surface of commercial TiO2 P25 via a photochemical reduction method. Compared with TiO2 P25, the prepared Ag-TiO2 NPs showed enhanced visible light photocatalytic degradation of the two antibiotics ciprofloxacin (CIP) and norfloxacin (NFX). Besides, the visible light photocatalytic mechanism of Ag-TiO2 NPs underlying the photodegradation of CIP was studied. Moreover, recycling experiments of Ag-TiO2 NPs demonstrated that Ag-TiO2 NPs could be reused. Last but not least, Ag-TiO2 NPs displayed an excellent ability to inhibit the growth of Escherichia coli (E. coli). Subsequently, Fe3O4/P(NIPAM-co-MAA) microspheres were prepared and characterized according to a previously published procedure. After the single components were obtained, studied and characterized, a large part of the thesis was devoted to the preparation of the Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites, which showed excellent adsorption, photocatalytic and antibacterial activities. The new multifunctional nanocomposites could not only adsorb dyes like basic fuchsin (BF), but also degrade antibiotics like CIP and NFX under visible light irradiation. More importantly, the nanocomposites could adsorb and degrade the pollutants mixture (BF and CIP) in water under visible light irradiation and showed good antibacterial activity towards E. coli. Due to the superparamagnetic properties of Fe3O4 NPs, the nanocomposites could be easily reused. Finally, another material, polyamidoamine (PAMAM) dendrimer-grafted Fe3O4/P(NIPAM-co-MAA) nanocomposite, was prepared by combining the previously prepared Fe3O4/P(NIPAM-co-MAA) microspheres with dendrimers. The obtained nanocomposites showed excellent adsorption activities towards differently charged dyes. In particular, thanks to the carboxylic groups on MAA in the Fe3O4/P(NIPAM-co-MAA) microspheres, the nanocomposites could adsorb positively charged dyes (e.g. BF), while, thanks to the amino groups on PAMAM dendrimers, also negatively charged dyes such as methyl orange (MO) could be adsorbed. Due to the superparamagnetic properties of the Fe3O4 NPs, the nanocomposites could be easily reused. In conclusion, these multifunctional nanocomposites in this thesis work overcame some current limitations, which hinder the use of nanomaterials in wastewater treatment applications, thereby providing an ecologically promising and effective method for reducing water pollution.:Declaration of primary authorship iii Acknowledgments v Abstract vii Kurzfassung ix List of figures xvii List of tables xxiii Nomenclature xxv Chapter 1: Introduction 1 1.1 Motivation 1 1.2 Challenges 1 1.3 Aim of the thesis 2 1.4 Outline of the thesis 3 Chapter 2: Fundamentals 5 2.1 Pollutants in wastewater 5 2.2 Adsorption technique for wastewater treatment 6 2.2.1 Activated carbon 7 2.2.2 Zeolites 7 2.2.3 Polymers 8 2.3 Photocatalysis 11 2.3.1 History of TiO2 in photocatalysis 12 2.3.2 TiO2 crystalline phases 12 2.3.3 TiO2 photocatalytic mechanism under UV light irradiation 13 2.3.4 Parameters influencing the photocatalytic efficiency of TiO2 16 2.4 Development of visible light-responsive TiO2 photocatalysts 19 2.4.1 Non-metal doping 20 2.4.2 Metal doping 20 2.4.3 Dye sensitization 21 2.4.4 Coupled semiconductors 22 Chapter 3: Materials and experimental methods 23 3.1 Materials 23 3.2 Protocols 27 3.2.1 Preparation of Ag-TiO2 NPs 27 3.2.2 Preparation of Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 27 3.2.3 Preparation of PAMAM dendrimer-grafted Fe3O4/P(NIPAM-co-MAA) nanocomposites 28 3.3 Characterization methods 29 3.3.1 High Resolution Transmission Electron Microscopy (HRTEM) 30 3.3.2 Attenuated Total Reflectance-Fourier Transform Infrared (ATR-FTIR) spectroscopy 30 3.3.3 X-ray powder Diffraction (XRD) 30 3.3.4 UV-Vis Diffuse Reflectance Spectroscopy (UV-Vis DRS) 30 3.3.5 Fluorometer 31 3.3.6 Brunauer-Emmett-Teller (BET) surface area analysis 31 3.3.7 Vibrating Sample Magnetometer (VSM) 31 3.3.8 Thermal Gravimetric Analysis (TGA) 31 3.4 Photocatalytic activity measurements 31 3.4.1 Visible light photocatalytic activity of TiO2 P25 and Ag-TiO2 NPs 32 3.4.2 Visible light photocatalytic investigations of Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 33 3.5 Adsorption capacity measurements 34 3.5.1 Adsorption capacity of Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 34 3.5.2 Adsorption capacity of PAMAM dendrimer-grafted Fe3O4/ P(NIPAM-co-MAA) nanocomposites 35 3.6 Antibacterial activity tests 37 3.6.1 Ag-TiO2 NPs antibacterial activity investigations 38 3.6.2 Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites antibacterial activity investigations 38 Chapter 4: Ag-TiO2 NPs 41 4.1 Characterization of Ag-TiO2 NPs 42 4.2 Photocatalytic activity of Ag-TiO2 NPs 47 4.2.1 Assessment of the photocatalytic activity of Ag-TiO2 NPs 47 4.2.2 Reusability of Ag-TiO2 NPs 50 4.2.3 Photocatalytic mechanism of Ag-TiO2 NPs 51 4.3 Antibacterial properties of Ag-TiO2 NPs 53 4.4 Summary 54 Chapter 5: Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 57 5.1 Characterization of Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 58 5.2 Adsorption of dyes by Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 64 5.3 Degradation of antibiotics by Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 68 5.4 Reusability of Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 72 5.5 Antibacterial activity of Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 74 5.6 Adsorption and degradation of a mixture of pollutants by Fe3O4/P(NIPAM-co-MA A)/Ag-TiO2 nanocomposites 75 5.6.1 Adsorption and degradation of BF by Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 75 5.6.2 Adsorption and degradation of CIP by Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 78 5.6.3 Adsorption and degradation of a mixture of BF and CIP by Fe3O4/P(NIPAM-co-MAA)/Ag-TiO2 nanocomposites 80 5.7 Summary 86 Chapter 6: PAMAM dendrimer-grafted Fe3O4/P(NIPAM-co-MAA) nanocomposites 89 6.1 Characterization of PAMAM dendrimer-grafted Fe3O4/P(NIPAM-co-MAA) nanocomposites 89 6.2 Adsorption capacity of different nanocomposites towards dyes 95 6.2.1 Adsorption of positively charged dye BF by different nanocomposites 96 6.2.2 Adsorption of negatively charged dye MO by different nanocomposites 97 6.2.3 Adsorption of BF and MO by G51P0.8 and G51P0.5 nanocomposites 98 6.2.4 Adsorption kinetics and isotherm of G51P1 nanocomposites 101 6.3 Reusability 105 6.4 Summary 106 Chapter 7: Conclusions and outlook 109 7.1 Conclusions 109 7.2 Outlook 111 Appendix 113 A1 Calibration curves 113 A2 Assessment of the photocatalytic activity of Ag-TiO2 NPs 114 References 117 Scientific output 141 Curriculum vitae 143

Monodisperse titanium dioxide (TiO2) nanoparticles were synthesized by a novel freeze-drying process herein called lyophilization. The process of lyophilization is described in detail. The materials were characterized by scanning electron microscopy SEM) including energy dispersive x-ray spectroscopy (EDXS), high resolution transmission electron microscopy (HRTEM), x-ray diffraction (XRD), Raman spectroscopy and UV-Vis-IR spectrophotometry. The TiO2 nanoparticles have narrow size distribution, mono-disperse, strained with most of the characteristics showing presence of the four phases of TiO2 thus: anatase, brookite, rutile with each lyophilization process producing its own phase mostly controlled by pH and precursor concentration and anneal/calcining temperatures. With specific reference to HRTEM, Raman spectroscopy results and XRD, it was found that the Scherrer equation, the Williamson-Hall method and others of similar nature were not enough to explain the strain and the grain sizes of these particles. Therefore the Williamson-Hall method was revised to properly explain the new results. The obtained TiO2 nanoparticles were used in three applications: (1) gas sensing (2) degradation of organic water-borne pollutants using methylene blue as an indicator (3) anti-bacterial activity. / Physics / D. Phil. Physics)

The main challenge of water splitting technology is to develop stable, visible responsive photocatalysts that satisfy the thermodynamic requirements to achieve water redox reactions. This study investigates development of the semiconductors containing metals with s2d10 electronic configuration such as Sn2+ or Bi3+ which shifts the valence band position negatively. Efficient water splitting can, however, be only achieved by understanding the fundamental semiconductor properties of underlying processes. This work elucidates the semiconductor properties through two approaches: the first is to synthesize the materials of various stoichiometry in various forms (powders, thin film etc.) and the second is to perform a combined experimental-theoretical studies to determine the optoelectronic properties of the synthesized materials. The study includes the synthesis and characterization of a series of Bi3+ based semiconductors (Bi2Ti2O7, Bi12TiO20, and Bi4Ti3O12) to resolve inconsistencies in their optoelectronic properties. The crystal parameters and stoichiometry were confirmed by the Rietveld refinement and XRD measurements. These compounds showed a UV responsive absorption, high dielectric constants, and low electron and hole effective masses in one crystallographic reflecting their good charge separation and carrier diffusion properties. The approach showed to be accurate in determining the optoelectronic properties due to good agreement between experimental and theoretical values. The second study investigated the synthesis of SnNb2O6 and using flux assisted method which afforded control over the surface. Increasing the flux to reactant molar ratio resulted in a 2D platelets with anisotropic growth along bc plane as confirmed by XRD and SEM. The photocatalytic activity increased while increasing the flux to reactant ratio exceeding solid state synthesis. This method minimized the oxidation of the surface and formation of grain boundaries and enabled the synthesis of the compound at lower temperature. Next, the optoelectronic properties of α-SnWO4 structure were studied though a combination of experimental and theoretical approach. α-SnWO4 thin films were deposited by RF-sputtering. An interesting low band gap of ~ 1.95 eV was experimentally for direct band gap and 1.7 eV for indirect band gap, high dielectric constants and low electron effective masses in one crystallographic direction were obtained, exhibiting good charge separation and charge carrier transport of the charge carriers. The PEC performance was limited by the oxidation of Sn2+ in the material under applied potential. Finally, pyrochlore SnSb2O6 structure was synthesized utilizing soft hydrothermal method. The crystal structure was studied by Rietveld refinement and the position of Sn2+ was specified. The material showed interesting absorption edge around 700 which is promising for overall water splitting application.

Technologies based on alternative and sustainable energy sources present a vital solution in the present and for the future. These technologies are strongly driven by the increased global energy demand and need to reduce environmental issues created by fossil fuel. Solar energy is an abundant, clean and free-access resource, but it requires harvesting and storage for a sustainable future. Direct conversion and storage of solar energy using heterogeneous photocatalysts have been identified as parts of a promising paradigm for generating green fuels from sunlight and water. This thesis focused on developing semiconductor absorbers in a visible light region for photocatalytic hydrogen production reaction. In addition, theoretical studies are combined with experimental results for a deep understanding of the intrinsic optoelectronic properties of the obtained materials. The study presents a novel family of oxysulfide BiAgOS, produced by applying a full substitution strategy of Cu by Ag in BiCuOS. I was interested to address how the total substitution of Cu by Ag in a BiCuOS system affects its crystal structure, optical and electronic properties using experimental characterizations and theoretical calculations. Single-phase bismuth silver oxysulfide BiAgOS was prepared via a hydrothermal method. Rietveld refinement of the powder confirmed that BiAgOS is an isostructural BiCuOS. The diffraction peak positions of BiAgOS, relative to those of BiCuOS, were shifted toward lower angles, indicating an increase in the cell parameters. BiCuOS and BiAgOS were found to have indirect bandgaps of 1.1 and 1.5 eV, respectively. The difference in the bandgap results from the difference in the valence band compositions. The hybrid level of the S and Ag orbitals in BiAgOS is located at a more positive potential than that of S and Cu, leading to a widened bandgap. Both materials possess high dielectric constants and low electron and hole effective masses, making them interesting for photoconversion applications. BiAgOS has a potential for photocatalytic hydrogen evolution reaction in the presence of sacrificial reagents; however, it is inactive toward water oxidation. BiCuOS and BiAgOS can be considered interesting starting compositions for the development of new semiconductors for PV or Z-scheme photocatalytic applications. The second study investigates the synthesis and characterization of NaBiS2, this contains Bi3+, which belongs to the p-block electronic configuration Bi3+ 6s26p0, and NaLaS2, which contains La3+ with electronic configuration 6s05d0. Solid-state reactions from oxide precursor starting materials were applied for synthesis the materials. The sulfurization process was conducted by pressurizing a saturated vapor of CS2. The obtained black material of NaBiS2 has an indirect transition with high absorption coefficients in the visible region of the spectrum and the absorption edge is determined at 1.21 eV. However, NaBiS2 did not show photocatalytic activity toward hydrogen production. NaLaS2 is characterized by an indirect transition with a bandgap in the UV region at 3.15 eV and can drive the photocatalytic hydrogen evolution reaction in Na2S/Na2SO3 solution. Utilizing the solid solution NaLa1-xBixS2 strategy, the absorption properties and band edge position for photocatalytic hydrogen evolution reaction were optimized. The results indicated that the bismuth content is critical parameter for maintaining the photocatalytic activity. The incorporation of low Bi content up to 6% in NaLaS2 leads to extending the photon absorption from the UV to the visible region and enhancing the photocatalytic activity of hydrogen production. In contrast, all the solid solutions that have Bi content of more than 12% present absorption edges close to that of pure NaBiS2, and they are inactive for photocatalytic hydrogen production. Combining the experimental measurements with density functional theory calculations, such behavior can be explained by the degree of overlapping of Bi and La states on the conduction band minimum (CBM). Finally, self-assembly of Bi2S3 nanorods were grown on FG or FTO substrates. Bi2S3 thin films were prepared by sulfurization of Bi metal layer using the hydrothermal method. The results show that Bi2S3 has absorption up to 1.3 eV and has a moderate absorption coefficient in the visible region. The ultraviolet photoelectron spectroscopy and photoelectron spectroscopy in air results showed that the conduction band minimum of Bi2S3 is located slightly above the hydrogen redox potential. However, Pt/Bi2S3 did not evolve a detectable amount of hydrogen, suggesting the presence of surface states that can hinder the hydrogen reduction reaction.