Due to the combination of their electronic, optical and mechanical properties, graphene and other layered materials (GRMs) have great potential for applications such as flexible optoelectronics and energy storage. Given that GRMs can be dispersed in solvents, solution processing is a particularly interesting approach that allows large volume production with tailored properties according to the targeted applications. \par In this dissertation I investigate liquid phase exfoliation and formulation of GRMs-based inks for flexible (opto) electronics, energy and photocatalysis. First I develop a protocol for the characterization of graphene inks, based on the statistical analysis of their Raman spectra. Such a tool is essential because of the scattering of characteristics in liquid-phase exfoliated material. I then report two novel processing techniques. The first consists on the exfoliation of graphene in organic solvents by the means of $\alpha$-functionalized alkanes as stabilising agents, which allows yield by weight ($Y_W$) of $\sim 100\%$. The second is based on exfoliation of graphite by microfluidization, where the material is stabilised in aqueous solution, with concentrations up to 100g/L. Such inks are successfully deposited by blade coating, leading to films of conductivity $\sim$ 2$\cdot$10$^4$ S/m at 25$\mu$m. I then investigate the use of graphene inks in optoelectronics and energy applications: First, I investigate inkjet printed graphene as hole injection layer (HTL). The cells with graphene HTL show high long-term stability, retaining 85$\%$ of the initial fill factor after 900 hrs in damp heat conditions. I then demonstrate flexible displays with graphene-SWNTs as pixel electrode. A 4x4 inch$^2$ demonstrator is realised integrating the ink into 12,700 pixels. I investigate graphene/MoO$_3$ electrode for supercapacitors with a specific capacitance of 342 F/cm$^3$. The electrode shows high cyclic stability, preserving $\sim$96$\%$ of the initial capacitance after 10,000 cycles. I finally report the production of TiO$_2$/exfoliated graphite as efficient photocatalytic composite able to degrade $\sim$100$\%$ more model pollutant with respect to TiO$_2$.

Neste trabalho foram empregados os métodos hidro e solvotérmico para sintetizar três diferentes catalisadores à base de bismuto (Bi2WO6, BiOI e BiVO4), visando aplicação em fotocatálise heterogênea sob radiação visível. Foram investigadas as influências do tempo de síntese, da calcinação, da adição de polivinilpirolidona (PVP) e do tipo de solvente usado durante a síntese sobre a morfologia, cristalinidade, área superficial específica e band gap das amostras. Os catalisadores foram caracterizados por microscopia eletrônica de varredura (MEV), espectroscopia de refletância difusa (ERD), difração de Raios-X (DRX) e adsorção de N2. Para avaliar a atividade fotocatalítica das amostras sintetizadas foram realizados experimentos em um reator batelada agitado, com o catalisador em suspensão e uma lâmpada de LED como fonte de radiação visível. As moléculas testes escolhidas foram o corante rodamina B, para determinação das amostras com maior atividade e, posteriormente, o fármaco prednisolona, sendo então estudados a influência da concentração de catalisador e do pH inicial do meio reacional. Foram realizados, também, ensaios de toxicidade com o organismo Lactuca sativa – sementes de alface, para avaliar a toxicidade da prednisolona pura, da mistura água e catalisador de BiOI e das alíquotas provenientes da reação de degradação da prednisolona após diferentes tempos. As amostras de Bi2WO6 apresentaram boa cristalinidade e semelhanças morfológicas apesar dos diferentes tratamentos. As amostras de BiOI, por sua vez, apresentaram diferenças significativas de morfologia, de microesferas para microplacas, quando foi feita a mudança de solvente e a amostra de BiVO4 apresentou um formato de paralelepípedo. Nos testes fotocatalíticos com a rodamina B, o catalisador que se mostrou mais ativo foi o BiOI cuja síntese continha PVP e etilenoglicol (kap = 0,0207 min-1) e o BiVO4 foi o que apresentou a menor atividade (kap = 0,0013 min-1). Na degradação da prednisolona, a maior taxa de degradação foi obtida com 1 g L-1 de catalisador e no pH natural do fármaco, 6,8. Os ensaios de toxicidade revelaram que nem a prednisolona nem a mistura água e catalisador são tóxicas para as sementes de alface, as alíquotas provenientes da reação, porém, tiveram um aumento de sua toxicidade com o aumento do tempo de reação. / In this work, solvo and hydrothermal methods were applied to synthesize three types of bismuth catalysts (Bi2WO6, BiOI and BiVO4) aiming to the apply it in heterogeneous photocatalysis under visible light. Were investigated the influences of reaction time, calcination, addition of poly (vinyl pyrrolidone) (PVP) and the solvent type during synthesis on their morphology, crystallinity, surface area and band gap. The catalysts were characterized by scanning electron microscopy (SEM), diffuse reflectance spectroscopy (DRS), X-ray powder diffraction (XRD) and nitrogen adsorption/desorption. To evaluate photocatalytic activity of the synthesized samples, experiments were carried out in a stirred batch reactor, with the catalyst in suspension and a LED lamp as a source of visible light. The test molecules chosen were the rhodamine B dye for determination of the samples with higher activity and subsequently the drug prednisolone, and then was studied the effect of catalyst concentration and initial pH of the reaction medium. Toxicity tests were also perfomed with organism Lactuca sativa – lettuce seeds, to the toxicity of pure prednisolone, water and BiOI catalyst mixture and aliquots from prednisolone degradation after different reaction times. As a result, the Bi2WO6 samples presented good crystallinity and morphological similarities despite having undergone different treatments. The BiOI catalysts presented a significant difference in morphology, microspheres to microplates, when changed the solvent, while the BiVO4 sample presented a parallelepiped shape. In the photocatalytic tests with rhodamine B, the catalyst with the highest activity was BiOI, containing PVP and ethylene glycol (kap = 0.0207 min-1) in its synthesis, and the BiVO4 was the catalyst with the lowest activity (kap = 0.0013 min-1). In the prednisolone degradation, the highest degradation rate was obtained with 1 g L-1 of catalyst and natural pH of the drug, 6.8. The toxicity tests showed that neither prednisolone nor water and catalyst mixture are toxic to lettuce seeds, aliquots from reaction, however, had an increase in their toxicity with increasing reaction time.

The development of sustainable and green technologies powered by renewable energy sources is highly desired to address the growing global energy need and water scarcity problems. Heterogeneous photocatalysis emerged in the past decades as promising solar-powered technology for environmental remediation applications such as wastewater treatment. The photoactivity of the materials is believed to be governed by complex mechanisms, still it was shown that it may be critically dependent on the following material properties (i) ability and effectiveness to absorb incident photons, (ii) charge separation efficiency, (iii) charge utilization efficiency, (iv) morphology including the size and shape of the nanostructure and its distribution and (v) the crystal structure, phase composition and crystallinity ... etc. Hence, most strategies aiming to improve the performance of photocatalytic materials may focus on one or more of the aforementioned aspects. Beside developing new materials or modifying existing systems, the development of sustainable, easy-to-operate systems are highly desired for developing countries such as Africa where almost half of the population are affected by water scarcity of some sort. For this motivation the immobilization of powder catalyst could be one attractive solution. In this thesis three experimental systems are presented. In the first two the effect of material properties on the photoactivity whereas in the third chapter the immobilization of powder catalyst was investigated. The first experimental project aimed to study the effect of synthesis parameters of WO3 nanostructures on its morphology, phase composition, optical properties and ultimately on the photoactivity. Understanding the role of process parameters to gain control over the material properties is still a challenge but is of great interest in photocatalysis. Here, a hydrothermal synthesis method was employed to synthesize WO3 nanostructures with various morphologies, crystal phases and optical properties. The effect of the solution pH, the polymeric surface modulator and the added EtOH was investigated on the material properties and on the photocatalytic activities. It was found that the crystal structure and the morphology of WO3 was influenced by the solution pH in the first place. It was proposed that stabilization effects between the crystal phase and the morphology could also influence the crystallization process beside supersaturation. It was revealed that despite the highest surface area of W-2.01-P20E, reduced oxidation state did not promote high photo-response. Instead the photoactivity of WO3 was seen as the compromise of the material properties including the optical, structural properties and the oxidation state. In the second experimental project the effect of Ag co-catalysis was studied on TiO2- Cu2O heterostructure formation. Coupling a wide band gap (TiO2) and a narrow band gap (Cu2O) semiconductor could benefit from extended light absorption properties and additionally from enhanced charged separation. In this study a facile wet chemical synthesis method was coupled with a UV treatment step to fabricate TiO2-Ag-CuxO ternary hybrid nano-materials. The effect of the Ag loading (1-5%) and the synthesis sequence of the Ag deposition step was evaluated on the material properties as well as on the visible photocatalytic activity. It was revealed that both the amount and the order of the Ag-deposition altered the material properties considerably. Typically TiO2/CuxO/Ag (TCA) catalysts had better visible light absorption properties but reduced affinity to adsorb methyl orange (MO) to their surface. Whereas, TiO2/Ag/CuxO (TAC) catalysts in general had better dye adsorption properties relative to TCA and had more efficient decoloration properties under visible light. TOC and HPLC-MS analysis revealed that MO and possibly its degradation products were mainly mineralized and/or adsorbed to the surface of TAC catalyst with 5% nominal Ag content in the visible process generating limited amount of byproducts in the final solution. The third experimental project focused on the immobilization of the previously prepared powder TiO2-Cu2O nanostructure. In this work a fluorine-doped tin oxide (FTO) glass sheet was used as a substrate and the doctor-blade coating technique has been employed to make TiO2-Cu2O thin films. Although this technique has a widespread use in the fabrication of solar cells to the best of our knowledge this is the first report on supported TiO2-Cu2O photocatalytic systems prepared by this method. To optimize the performance of the TiO2- Cu2O thin film under visible light irradiation, the chemical composition of the doctor-blading paste and the temperature of the final thermal treatment step was studied. It was found that both the paste composition and the heat treatment step played an important role in the material properties. When the film contained ethyl cellulose the minimum temperature to remove organic additives was 350 °C. Whereas for the films containing only alpha terpineol 300 °C was sufficient. It was revealed that the higher temperature treatment resulted in more oxidized films which were also shown in their deeper colour. The most effective film under visible light irradiation was TC-0-300 which contained no cellulose and was treated at the lowest temperature.

Photocatalytic treatment has the potential to become a cost effective method of organic contaminant removal from water. Photocatalytic materials are semiconductors that enhance chemical reactions such as the breakdown of organic molecules in the presence of light. One of the most studied photocatalysts for water purification is titanium dioxide (TiO2). Variations in the composition of photocatalysts can affect the outcome of the experiments, the detection of the change in behaviour of the photocatalyst is of significant scientific interest. It requires minimisation of the impact of all other factors affecting the photocatalytic process, such as temperature, light intensity, wavelength and uniformity. Repeatability of the experiments is also affected by these factors. If their impact is not considered and addressed the outcome of multiple seemingly identical experiments with a single sample of the photocatalyst will produce different results. Light is one of the most important factors in a photocatalytic process. The undoped TiO2 has a sharp drop in its light absorbtion characteristics between UV and visible spectral regions. It is theregion of the spectrum where most efficient UV LEDs radiate. As the characteristics of the light produced by LEDs are temperature dependent, heat management is important in achieving light with stable characteristics and prolonged lifetime of the LEDs. One of the contributions of this thesis is a novel method of not only stabilisation of the LED radiation parameters, namely optical output power and wavelength, but also the independent control of these parameters. The importance of LED calibration is also a significant contribution as commercial LEDs have dierent radiation parameters between devices. Possibility of independent control of optical power and wavelength of the LEDs has allowed to demonstrate the importance of radiant flux (total spectral power) over the peak spectral flux (power of a single wavelength component) for TiO2 activation, which is another significant contribution of this work. Uniformity of the produced light is another factor that needs to be addressed when a light source for the photocatalytic experimentation is designed. Non-uniform light distribution in a photocatalytic reactor will result in bright spot formation that will affect the overall performance of the photocatalytic sample. This together with the temperature control of the photocatalyst and the water sample are key issues that need to be addressed for achieving ecient and repeatable experimentation outcomes. Photocatalytic reactors developed from simulation to the working prototypes and tested during the work described in this thesis address the problem of light distribution uniformity. They have been designed to remove as many sources of uncertainty usually present in photocatalytic reactors as possible, such as for example temperature stability of the liquid sample, dierent sizes or of the photocatalytic samples and same volume of the liquid sample. As such, these novel reactors together with LED light sources provide a contribution of having a potential of becoming a photocatalytic experimentation standard for achieving the repeatable and comparable results.

Os produtos farmacêuticos têm sido considerados como um problema ambiental devido à sua entrada contínua e persistência no ecossistema aquático, mesmo em baixas concentrações (µg L-1 e ng L-1). Muitos fármacos têm sido frequentemente determinados em Estações de Tratamento de Esgoto (ETEs), águas superficiais, subterrâneas e de abastecimento, devido à baixa eficiência dos sistemas convencionais de tratamento na eliminação destes compostos. O diclofenaco (DCF), é um Anti-Inflamatório Não Esteróide (AINE) comumente utilizado como analgésico, antiartrítico e antirreumático. Possui uma baixa biodegradabilidade e tem a capacidade de bioacumulação nos tecidos de seres vivos, podendo apresentar efeitos ecotóxicos. Como o DCF pode não ser eficientemente removido pelos tratamentos convencionais de água e esgoto, novos processos têm sido pesquisados para a sua remoção, entre eles os processos oxidativos avançados (POAs). O objetivo deste trabalho foi tratar o DCF sódico aquoso por fotocatálise heterogênea (TiO2/UV). Para isso foi realizado um planejamento fatorial 25 com a finalidade de se determinar os efeitos dos parâmetros reacionais -- dosagem e tipo de fotocatalisador, concentração inicial do fármaco, tipo de aceptor de elétrons e pH -- sobre o desempenho do tratamento. A variável-resposta observada foi a redução da área sob o espectro de absorção no UV. A condição ótima de tratamento foi: pH = 5; dosagem de TiO2 = 0,5 g L-1; concentração inicial de DCF = 20 mg L-1; aceptor de elétrons = oxigênio; e tipo de catalisador = P25 (Evonik). No estudo da cinética, a degradação do fármaco foi acompanhada por Cromatografia Líquida de Alta Eficiência (CLAE). Para a amostra tratada por fotocatálise heterogênea, a concentração de DCF foi reduzida a aproximadamente 40 µg L-1 em 30 min de irradiação e a degradação seguiu o modelo cinético de Langmuir-Hinshelwood (R2 = 0,95) com constante de velocidade k = (2,3 ± 0,070) × 103 µg L-1 min-1 e uma constante de adsorção K = (2,1 ± 0,17) × 10-4 L µg-1. No ensaio de fotólise a concentração foi reduzida a aproximadamente 70 µg L-1 em 12,5 min de tratamento e observou-se uma cinética de ordem zero (R2 = 0,96) com k = (2,7 ± 0,070) × 103 µg L-1 min-1. Foram identificados alguns intermediários de oxidação por cromatografia líquida acoplada a espectroscopia de massas (LC/MS-MS) e foram realizados ensaios ecotoxicológicos (Daphnia similis e Lactuca sativa) das amostras tratadas. Nenhum dos tratamentos (fotocatálise e fotólise) estudados gerou ecotoxidade nos organismos-teste. Indica-se a fotólise, nas condições deste trabalho, como mais eficiente para a degradação do diclofenaco. / Pharmaceuticals are considered an environmental problem due to their continuous input and persistence in aquatic ecosystems, even at low concentrations (µg L-1 e ng L-1). Many drugs are often detected in Sewage Treatment Plants (STPs), surface water, groundwater and drinking water due to the low efficiency of conventional treatment systems in removing those compounds. Diclofenac (DCF) is a nonsteroidal anti-inflammatory drug (NSAID) commonly used as an analgesic, antiarthritic and antirheumatic. It has low biodegradability and can bioaccumulate in the tissues of organisms, and may have ecotoxicological effects. Since DCF cannot be efficiently removed by conventional water and sewage treatments, new processes have been studied for its removal, including the advanced oxidation processes (AOPs). The aim of this study was to treat aqueous diclofenac by heterogeneous photocatalysis (TiO2/UV). For this purpose, a factorial design 25 was performed in order to determine the effects of the reaction parameters -- dosage and type of photocatalyst, initial concentration of the drug, type of electron acceptor and pH -- on the treatment performance. The response variable observed was the reduction in the area under the UV absorption spectrum. The optimal treatment condition was: pH = 5; TiO2 dosage = 0,5 g L-1; DCF initial concentration = 20 mg L-1; electron acceptor = oxygen; and type of catalyst = P25 (Evonik). In the kinetic study, the drug degradation was determined by High Performance Liquid Chromatography (HPLC). For the sample treated by heterogeneous photocatalysis, DCF initial concentration was reduced to approximately 40 µg L-1 in 30 min of irradiation, and the degradation followed the Langmuir-Hinshelwood kinetic model (R2 = 0,95) with rate constant k = (2,3 ± 0,070) × 103 µg L-1 min-1 and adsorption constant K = (2,1 ± 0,17) × 10-4 L µg -1. During photolysis, DCF initial concentration was reduced to approximately 70 µg L-1 in 12,5 min of treatment and followed a zero-order kinetics (R2 = 0,96) with k = (2,7 ± 0,070) × 103 µg L-1 min-1. Some oxidation intermediates were identified by liquid chromatography coupled to mass spectroscopy (LC/MS-MS) and ecotoxicological tests performed (Daphnia similis and Lactuca sativa) for the treated samples. None of the studied treatments (photocatalysis and photolysis) produced ecotoxicity to the test-organisms. Photolysis is preferable, within the present studied conditions, to degrade aqueous diclofenac.

Os produtos farmacêuticos têm sido considerados como um problema ambiental devido à sua entrada contínua e persistência no ecossistema aquático, mesmo em baixas concentrações (µg L-1 e ng L-1). Muitos fármacos têm sido frequentemente determinados em Estações de Tratamento de Esgoto (ETEs), águas superficiais, subterrâneas e de abastecimento, devido à baixa eficiência dos sistemas convencionais de tratamento na eliminação destes compostos. O diclofenaco (DCF), é um Anti-Inflamatório Não Esteróide (AINE) comumente utilizado como analgésico, antiartrítico e antirreumático. Possui uma baixa biodegradabilidade e tem a capacidade de bioacumulação nos tecidos de seres vivos, podendo apresentar efeitos ecotóxicos. Como o DCF pode não ser eficientemente removido pelos tratamentos convencionais de água e esgoto, novos processos têm sido pesquisados para a sua remoção, entre eles os processos oxidativos avançados (POAs). O objetivo deste trabalho foi tratar o DCF sódico aquoso por fotocatálise heterogênea (TiO2/UV). Para isso foi realizado um planejamento fatorial 25 com a finalidade de se determinar os efeitos dos parâmetros reacionais -- dosagem e tipo de fotocatalisador, concentração inicial do fármaco, tipo de aceptor de elétrons e pH -- sobre o desempenho do tratamento. A variável-resposta observada foi a redução da área sob o espectro de absorção no UV. A condição ótima de tratamento foi: pH = 5; dosagem de TiO2 = 0,5 g L-1; concentração inicial de DCF = 20 mg L-1; aceptor de elétrons = oxigênio; e tipo de catalisador = P25 (Evonik). No estudo da cinética, a degradação do fármaco foi acompanhada por Cromatografia Líquida de Alta Eficiência (CLAE). Para a amostra tratada por fotocatálise heterogênea, a concentração de DCF foi reduzida a aproximadamente 40 µg L-1 em 30 min de irradiação e a degradação seguiu o modelo cinético de Langmuir-Hinshelwood (R2 = 0,95) com constante de velocidade k = (2,3 ± 0,070) × 103 µg L-1 min-1 e uma constante de adsorção K = (2,1 ± 0,17) × 10-4 L µg-1. No ensaio de fotólise a concentração foi reduzida a aproximadamente 70 µg L-1 em 12,5 min de tratamento e observou-se uma cinética de ordem zero (R2 = 0,96) com k = (2,7 ± 0,070) × 103 µg L-1 min-1. Foram identificados alguns intermediários de oxidação por cromatografia líquida acoplada a espectroscopia de massas (LC/MS-MS) e foram realizados ensaios ecotoxicológicos (Daphnia similis e Lactuca sativa) das amostras tratadas. Nenhum dos tratamentos (fotocatálise e fotólise) estudados gerou ecotoxidade nos organismos-teste. Indica-se a fotólise, nas condições deste trabalho, como mais eficiente para a degradação do diclofenaco. / Pharmaceuticals are considered an environmental problem due to their continuous input and persistence in aquatic ecosystems, even at low concentrations (µg L-1 e ng L-1). Many drugs are often detected in Sewage Treatment Plants (STPs), surface water, groundwater and drinking water due to the low efficiency of conventional treatment systems in removing those compounds. Diclofenac (DCF) is a nonsteroidal anti-inflammatory drug (NSAID) commonly used as an analgesic, antiarthritic and antirheumatic. It has low biodegradability and can bioaccumulate in the tissues of organisms, and may have ecotoxicological effects. Since DCF cannot be efficiently removed by conventional water and sewage treatments, new processes have been studied for its removal, including the advanced oxidation processes (AOPs). The aim of this study was to treat aqueous diclofenac by heterogeneous photocatalysis (TiO2/UV). For this purpose, a factorial design 25 was performed in order to determine the effects of the reaction parameters -- dosage and type of photocatalyst, initial concentration of the drug, type of electron acceptor and pH -- on the treatment performance. The response variable observed was the reduction in the area under the UV absorption spectrum. The optimal treatment condition was: pH = 5; TiO2 dosage = 0,5 g L-1; DCF initial concentration = 20 mg L-1; electron acceptor = oxygen; and type of catalyst = P25 (Evonik). In the kinetic study, the drug degradation was determined by High Performance Liquid Chromatography (HPLC). For the sample treated by heterogeneous photocatalysis, DCF initial concentration was reduced to approximately 40 µg L-1 in 30 min of irradiation, and the degradation followed the Langmuir-Hinshelwood kinetic model (R2 = 0,95) with rate constant k = (2,3 ± 0,070) × 103 µg L-1 min-1 and adsorption constant K = (2,1 ± 0,17) × 10-4 L µg -1. During photolysis, DCF initial concentration was reduced to approximately 70 µg L-1 in 12,5 min of treatment and followed a zero-order kinetics (R2 = 0,96) with k = (2,7 ± 0,070) × 103 µg L-1 min-1. Some oxidation intermediates were identified by liquid chromatography coupled to mass spectroscopy (LC/MS-MS) and ecotoxicological tests performed (Daphnia similis and Lactuca sativa) for the treated samples. None of the studied treatments (photocatalysis and photolysis) produced ecotoxicity to the test-organisms. Photolysis is preferable, within the present studied conditions, to degrade aqueous diclofenac.

Water is a vital natural resource. To develop more sustainable water systems, we must focus efforts on the removal of persistent contaminants. Aqueous organic contaminants include azo dyes, halogenated organics (e.g. pesticides), and algal and bacterial metabolites. The latter are common to surface waters and freshwater aquaculture systems and can cause taste and odor problems. Two of the principal organoleptic compounds are geosmin and 2-methylisoborneol (MIB). Traditional oxidation treatment methods, utilizing chlorine, hydrogen peroxide, and potassium permanganate, have been employed with varying levels of efficacy for removal of these and other organic contaminants. Advanced Oxidation Processes (AOPs) have greater potential for the removal of persistent contaminants than traditional methods due to their higher pollutant removal rates, their ability to degrade a variety of organic material, and their ability to completely mineralize compounds [1]. An emerging AOP technology is the use of titania based photocatalysts for water treatment. Titanium dioxide (TiO2) is an effective, inexpensive, and stable photocatalyst used for the decomposition of aqueous organics. Titania is primarily activated by the ultraviolet portion of the spectrum due to its energy band gap of 3.0-3.2 eV (depending upon crystalline structure). Photocatalytic efficiency can be enhanced or tuned through the use of semiconductor dopants and the variance of titania crystal structure (i.e. anatase to rutile ratios). Metal oxides, like indium vanadate (InVO4), may enhance reaction rates through new interfacial reaction sites and electron scavenging, transport, and storage. InVO4 has been shown to have four sub-bandgap transitions, of which three are in the visible range [2]. In this work, the synthesis of InVO4-TiO2 composite semiconductors is examined to shift photo-initiation into the visible portion of the spectrum. Parametric studies of the visible spectrum photodegradation of methyl orange, an azo dye, and 2-chlorophenol provide a basis for analysis. Methyl orange was utilized to ascertain the effect of pure and mixed phase titania in the semiconductor composites. The TiO2 photodegradation of geosmin and MIB has been previously demonstrated in small-scale batch slurry reactions. Slurry systems require the downstream separation of catalyst from the liquid. Laboratory trials use centrifugation or micro-filtration. Alternatively, immobilization of the photocatalyst could allow scale-up of the process. Here, titania was immobilized on glass plate substrates using an ethanol spray technique. Finally, naturally tainted waters may contain a number of constituents in addition to the target compounds. In recirculating aquaculture systems, the water contains natural organic matter (NOM), ammonia, nitrite/ nitrate, and carbonate species. These constituents may block light penetration, block reaction sites, scavenge hydroxyl radicals, or affect the surface chemistry of the catalyst. Further, geosmin and MIB concentrations are extremely low, in the ppt range. Naturally tainted waters from MOTE Marine Laboratory Aquaculture Research Park are treated in the laboratory and in situ to demonstrate TiO2 degradation efficiency for trace concentration geosmin and MIB degradation in a complex water matrix.

No description available.

In this thesis, titanium dioxide (TiO2)-based thin film photocatalysts of different morphologies were synthesized and studied for their photoelectrocatalytic and photocatalytic properties. The superhydrophilicity of selected TiO2 films were also assessed. The work started with the synthesis of nanocrystalline TiO2 thin films with minimal porosity. A photoelectrocatalytic study was performed to evaluate the films?? photocurrent response in the presence of various organic compounds. At low concentrations, the amount of photocurrent generated was found to be influenced by the molecular structure of the organic compounds. As the concentration increased, the photocurrent response became dependent on the level of interaction of the organic compounds and their partially degraded intermediates with the TiO2 surface. Highly dispersed platinum (Pt) were added onto TiO2 films by a photo-deposition method, and their photocatalytic and photoelectrocatalytic activities were assessed using a novel thin-layer photo(electrochemical)-catalytic system. The system allowed the photocurrent data that originated from the photoelectrocatalysis process to be collected in the reaction cell, and the amount of organic compound being oxidized to be quantified. The Pt deposits were found to enhance photocatalysis by increasing the photogenerated charge-carriers separation, but conversely they retarded the photoelectrocatalysis process. The next part of the work covered the development of mesoporous TiO2 films via the evaporative-induced self-assembly procedure. The structural characteristics of the films were altered by controlling the relative humidity and temperature during the coating and thermal treatment processes. The effect of key structural parameters, such as film porosity, surface area and crystallinity, on the photoelectrocatalytic activity was investigated. These parameters were found to affect the photoelectrocatalysis because the performance of a catalyst in the photoelectrocatalysis application relies strongly on attributes such as the photocatalyst particles?? interconnectivity and the contact to the conducting substrate. The last part of this thesis demonstrated the effort undertaken to improve the UV-induced superhydrophilic effect of a TiO2 film. A multilayer structure of TiO2 nanoparticles was assembled to create a novel TiO2 film that required no UV-activation to induce a uniform water sheeting across its surface. The novel TiO2 thin film exhibited stable superhydrophilic wetting and anti-fogging behaviors after repetitive cycles of heat and wetting treatment, and this performance was affected by the porosity and surface hydroxyl (-OH) contents.

The current work investigates the photocatalytic reduction of selenium (Se) ions, selenate Se(VI) and selenite Se(IV), from two perspectives: Se ion removal from water and wastewater and the formation of nano-Se compounds. Se ion pollution has become an environmental issue in recent years, and hence there is an urgent need for an efficient removal technique. In addition, there is increasing interest in the formation of nano-size semiconductors for niche applications. Since Se is a semiconductor, its formation onto the semiconductor TiO2 could lead to the discovery of new composite materials. The current study has successfully elucidated the mechanism of Se ions reduction by photocatalysis. Factors such as the simultaneous adsorption of the Se ions (the electron scavenger in this case) and a suitable organic compound (the hole scavenger), and the chemical properties of the hole scavenger were crucial for effective and efficient Se ions photoreduction. Optimum conditions in relation to pH, concentrations and types of hole scavenger were reported and discussed. It was also found that stoichiometric adsorption ratio of formate and selenate resulted to optimum photoreduction rate. A modified Langmuir-Hinshelwood kinetic model that considered the simultaneous adsorption of both solutes was derived. The current investigation has also seen the successful formation Se deposits of different morphologies onto the TiO2 particles. Discrete Se particles of various sizes in the nano-size range as well as a Se film were deposited onto the TiO2 particles under different initial experimental conditions. The Se-TiO2 composite semiconductor was explored for the removal of cadmium Cd2+ ions, which resulted in the formation of CdSe-TiO2 systems. The photoreduction of Se ions using silver-modified TiO2 showed the enhanced reduction of Se ions to Se2- in the form of H2Se gas. It is suggested that the H2Se gas generated from the current photoreduction process could be used as a safer and cheaper technique in the formation of Se-compounds such copper selenide, cadmium selenide and zinc selenide. All these compounds were widely used in optical and semiconducting devices.