Dissertations / Theses: 'ZnO photocatalysis'

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Ramirez, Canon Anyela M. "Nanostructured ZnO films for water treatment by photocatalysis." Thesis, University of Bath, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687342.

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The development of nanostructured materials for environmental applications has received considerable attention in recent years. The properties of nanoparticles or nanostructured materials, such as large surface areas or high aspect ratios, translate into large improvements in the performance of existing devices and in the discovery of novel applications. On the other hand, photocatalysis is an attractive technology for the elimination of organic pollutants in water due to its simplicity, ease of implementation and reasonable cost compared to other advanced oxidation processes. A key disadvantage of many photocatalysts is their use in powder form which makes their recovery from treated water costly. In addition, incomplete removal can lead to accumulation over time with adverse effects to the environment. As a result significant effort has been placed in immobilizing photocatalytic materials on different substrates. The immobilization of photocatalyst results in a decrease in photocatalytic performance mainly due to reduction of surface area; therefore, research is now focusing on developing nanostructured materials which combine the attributes of nanotechnology and photocatalysis. In the present thesis, a systematic study of the relationship between properties of supported ZnO nanostructures and their photocatalytic activity was performed. Analysis was carried out by producing ZnO nanostructured films via anodization. The effects of voltage, temperature, reaction time and type of electrolyte on the morphology of ZnO nanostructures was studied. Results show that the type of electrolyte and its concentration determine the morphology and size of the nanostructures. Voltage, time and temperature affect the distribution and density of the nanostructures along the surface and affect the crystal size of the ZnO. The band gaps of the films were in the range of 3.27 and 3.50 eV. Although ZnO is a hydrophilic material, some of the films displayed hydrophobic and super-hydrophobic behaviour. The results obtained in this study and some data already published in the literature were correlated to the synthesis parameters, and were used to devise design guidelines to obtain ZnO films with specific nanostructures and macroscopic properties by controlling the anodization parameters. The photocatalytic activity of the ZnO nanostructured films (ZnO-NFs) were studied using three different photocatalytic reactors, (i) a thermo-stated batch reactor, (ii) a recirculating flat plate reactor, and (iii) a recirculating tubular annular reactor. Phenol and methyl orange (MO) were used as a model compounds. It was found that crystal size does not affect the photocatalytic performance of the films while morphology has an important impact on the degradation of phenol. The stability of the ZnO nanostructures was tested under different levels of oxygen, degradation of phenol occurred even at anoxic conditions following the Mars-van Krevelen mechanism. The formation of new nanostructures produced during the photocatalytic reaction was studied and a mechanism of formation was proposed. The study of the photocatalytic performance in the flat plate reactor showed that there was a mass transfer limitation in the process. ZnO nanostructures showed higher photocatalytic activity and morphology stability in the tubular annular reactor. Degradation of MO and phenol was produced in darkness by the nanostructures supported in Zn foil. It was also demonstrated that oxygen plasma post-treatment enhances the photocatalytic activity of the ZnO-NF by 36% while making the photocatalyst more stable for the photocatalytic degradation of phenol compared to those treated with heat. An electrical current was applied to the photocatalyst in the tubular annular reactor, which improved the degradation of phenol and participated in the formation of nanostructures in the Zn wire surface.

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PERIASAMY, VAIRAVANATHAN PONRAJESH. "BILAYER FILM CATALYSIS OF ZnO-CdO AND A COMPARISON WITH ZnO FILM CATALYSIS." Miami University / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=miami1196312783.

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Kwiatkowski, Maciej. "ZnO(core)/TiO2(shell) composites : influence of TiO2 microstructure, N-doping and decoration with Au nanoparticles on photocatalytic and photoelectrochemical activity." Thesis, Bourgogne Franche-Comté, 2017. http://www.theses.fr/2017UBFCK046/document.

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Le but de la thèse est d'étudier l'influence de la microstructure des composites ZnO/TiO2 sur leurs propriétés dans la dégradation photocatalytique des polluants organiques et dans l'oxydation de l'eau photoassistée. Pour réaliser cette étude, nous avons choisi la conception basée sur des nano bâtonnets ZnO supportés sur une électrode de verre recouverte d'ITO (Indium Tin Oxide). Les nano bâtonnets de ZnO ont ensuite été recouverts d'une couche de TiO2 dans différentes conditions. La composition et la microstructure des composites ZnO(cœur)/TiO2(coquille) ont été modifiées dans le but d'élucider comment ces paramètres influencent leur activité photocatalytique. La couche TiO2 de morphologie différente (discontinue ou compacte) a été élaborée. Nous avons montré que le composite contenant la couche de TiO2 discontinue possède une activité plus élevée dans la dégradation de MB et dans l'oxydation de H2O sous 400 nm. Cette photoactivité améliorée a été attribuée à une meilleure accessibilité pour les réactifs de l'interface ZnO/TiO2 à travers la couche de TiO2. Aussi nous avons pu améliorer l'activité des composites sous la lumière visible. Dans ce but, les composites constitués de nano bâtonnets de ZnO supportés sur ITO ont été recouverts de TiO2 dopé à l'azote et décorés de nanoparticules d'or. Il a été trouvé que même une faible charge d'or (0,37% at.) permet une augmentation de 60% de la vitesse de décoloration photocatalytique du MB sous la lumière visible par rapport à l'échantillon sans or en raison de l'effet plasmonique. Un dopage simultané à l'azote et à l'or a permis également de multiplier par trois le photocourant dans l'oxydation photoassistée de l'eau
The aim of the thesis is to study the influence of microstructure of ZnO/TiO2 composites on their properties in photocatalytic degradation of organic pollutants, and in photoassisted water oxidation. To realize such study we chose the design based on ZnO nanorods supported on ITO (Indium Tin Oxide)-coated glass electrode. The ZnO nanorods were then covered with a layer of TiO2 under different conditions. The composition and microstructure of the obtained ZnO(core)/TiO2(shell) composites were modified in the aim to elucidate how these parameters influence their photocatalytic activity. The results of studies lead to elaboration of two most distinctive variants of sol-gel procedure that allow to deposit TiO2 layers of controlled thicknesses and different morphology (rugged or compact). The composite containing the rugged TiO2 layer was shown to possess significantly higher activity in MB degradation and in photoassisted H2O oxidation under 400 nm. This improved photoactivity was attributed to a higher porosity and better accessibility of ZnO/TiO2 interface region through the rugged TiO2 layer by the reagents. The effort was also made to enhance the visible light activity of the composites. To this aim the composites consisting of ITO-supported ZnO nanorods covered with nitrogen-doped titanium dioxide and decorated with Au nanoparticles. It was found that even a low Au loading (0.37% at.) resulted in 60% enhancement of photocatalytic decolorization of MB under visible light with respect to the Au-free sample owing to plasmonic effects. A simultaneous N-doping and Au decoration allowed also to multiply by three the photocurrent in photoassited water oxidation

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Donat, Florian. "Microréacteurs photocatalytiques utilisant des oxydes métalliques semi-conducteurs sensibilisés par des Quantum Dots CuInS2/ZnS." Thesis, Université de Lorraine, 2017. http://www.theses.fr/2017LORR0085/document.

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La pollution actuelle des effluents hospitaliers par des médicaments, nécessite le développement de nouvelles techniques de traitement, la photocatalyse étant l’une des plus efficaces pour remédier à ce type de pollution. Cependant, les oxydes métalliques utilisés pour la photocatalyse (TiO2, ZnO, …) ne sont activables que sous irradiation UV. L’association de ces oxydes à des Quantum Dots (QDs), crée une hétérojonction qui étend la zone d’activation du photocatalyseur vers les rayonnements visibles et diminue les recombinaisons des porteurs de charges. La première partie de ce travail décrit le développement d’un photocatalyseur activable sous irradiation solaire pour la dégradation du colorant Orange II. Nous avons d’abord caractérisé l’hétérojonction créée entre ZnO et les QDs CuInS2/ZnS (ZCIS) puis étudié leur efficacité photocatalytique, en regardant notamment leurs capacités à générer des espèces réactives de l’oxygène. Dans la seconde partie, nous avons évalué la photodégradation d’un agent anticancéreux, l’Ifosfamide, présent dans les effluents hospitaliers. Pour cela, des réacteurs fermés agités et des microréacteurs ont été utilisés. Dans les deux cas, l’Ifosfamide, ainsi que ses intermédiaires de dégradation, sont photodégradés efficacement par le catalyseur ZnO/ZCIS sous une irradiation solaire de faible intensité (5 mW/cm2). Dans le cas des microréacteurs, le dépôt du catalyseur dans le microcanal a été optimisé et sa stabilité évaluée. Les résultats montrent que le catalyseur ZnO/ZCIS est réutilisable cinq fois sans perte d’activité, témoignant d’une bonne recyclabilité, ce qui en fait un bon candidat pour des applications photocatalytiques
The pollution of hospital effluents by pharmaceutical drugs, requires the development of new treatment techniques. Among these processes, photocatalysis is one of the most efficient one and allows the remediation of this kind of pollution. However, metal oxides used for photocatalysis (TiO2, ZnO, …) can only be activated by UV light. The association of these oxides with quantum dots (QDs) creates an heterojunction, which not only allows to extend the activation spectrum of the photocatalyst to the visible region but also decreases the charge carriers recombinations. The first part of this work describes the development of a catalyst responding to solar light irradiation for the degradation of the Orange II dye. First, we characterized the heterojunction created between ZnO and the CuInS2/ZnS (ZCIS) QDs and evaluated their photocatalytic efficiency. This work was undertaken by evaluating the capacity of the ZnO/ZCIS catalyst to produce reactive oxygen species (ROS). In the second part, we studied the photodegradation of the antineoplastic agent Ifosfamide commonly found in hospital effluents. For this purpose, closed and agitated reactors but also microreactors were used. In both cases, Ifosfamide, and the compounds originating from its degradation, can be fully photodegraded under simulated light of weak intensity (5 mW/cm2) using the ZnO/ZCIS catalyst. In the case of microreactors, the deposition of the catalyst was optimized and its stability evaluated. Results obtained demonstrate that the ZnO/ZCIS catalyst can be reused, at least five times, without significant loss in activity, thus demonstrating its ability to be used in real photocatalytic applications

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Herring, Natalie. "Formation Mechanisms and Photocatalytic Properties of ZnO-Based Nanomaterials." VCU Scholars Compass, 2013. http://scholarscompass.vcu.edu/etd/494.

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Zinc Oxide (ZnO) is one of the most extensively studied semiconductors because of its unique properties, namely, its wide band gap (3.37 eV) and high excitation binding energy (60 meV). These properties make ZnO a promising material for uses in a broad range of applications including sensors, catalysis and optoelectronic devices. The presented research covers a broad spectrum of these interesting nanomaterials, from their synthesis and characterization to their use as photocatalyts. A new synthetic approach for producing morphology controlled ZnO nanostructures was developed using microwave irradiation (MWI). The rapid decomposition of zinc acetate in the presence of a mixture of oleic acid (OAC) and oleylamine (OAM) results in the formation of hexagonal ZnO nanopyramids and ZnO rods of varying aspect ratios. The factors that influence the morphology of these ZnO nanostructures were investigated. Using ligand exchange, the ZnO nanostructures can be dispersed in aqueous medium, thus allowing their use as photocatalysts for the degradation of malachite green dye in water. Photocatalytic activity is studied as a function of morphology; and, the ZnO nanorods show enhanced photocatalytic activity for the degradation of the dye compared to hexagonal ZnO nanopyramids. After demonstrating the catalytic activity of these ZnO nanostructures, various ways to enhance photocatalytic activity were studied by modification of this MWI method. Photocatalytic activity is enhanced through band gap modulation and the reduction of electron-hole recombination. Several approaches were studied, which included the incorporation of Au nanoparticles, N-doping of ZnO, supporting ZnO nanostructures on reduced graphene oxide (RGO), and supporting N-doped ZnO on N-doped RGO. ZnO-based nanostructures were studied systematically through the entire process from synthesis and characterization to their use as photocatalysis. This allows for a thorough understanding of the parameters that impact these processes and their unique photocatalytic properties.

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Moussa, Hatem. "Influence de l’association de quantum dots ZnO avec des ions Cu²+ sur leur (photo)toxicité. Nouveaux matériaux ZnO/rGO pour la photocatalyse solaire." Thesis, Université de Lorraine, 2016. http://www.theses.fr/2016LORR0036/document.

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Ces dernières années, les énormes progrès réalisés en nanotechnologie ainsi qu’en science des matériaux ont conduit à la préparation de nombreuses nouvelles nanoparticules sans réellement connaître l’ensemble des propriétés associées à leurs dimensions. La première partie de notre travail vise à évaluer les risques et les problèmes associés aux nanomatériaux, en termes de toxicité, en utilisant des nanoparticules de ZnO. Nous avons tout d’abord étudié la capacité de ces nanoparticules à générer des espèces réactives d’oxygènes (EROs) sous irradiation UV en utilisant trois types des quantum dots (QDs) comme modèles, ZnO, ZnO dopé avec des ions Cu2+ et ZnO avec des ions Cu2+ adsorbés à sa surface. Les trois types des QDs ont montré une forte capacité à générer des EROs mais ceux modifiés par les ions Cu2+ en périphérie sont les plus producteurs. Ces QDs inhibent également le plus fortement la croissance de la bactérie E. coli. La toxicité n’est cependant pas dépendante des EROs photo-produits ni du zinc (+2) libéré par les QDs et montre qu’un mécanisme plus complexe doit être considéré. Dans une second partie, nous avons tenté d’améliorer l’activité photocatalytique de nanobâtonnets de ZnO en les associant à de l’oxyde de graphène réduit (rGO). Des nanocomposites ZnO/rGO ont été préparés par voie solvothermale et utilisés pour la phototodégradation du colorant Orange II comme modèle de polluant. Les résultats obtenus montrent que le photocatalyseur ZnO/rGO est très efficace sous irradiation solaire ou visible et qu’il est peu sensible à des variations de pH ou à la présence de perturbateurs dans le milieu. Finalement, le photocatalyseur est très stable et peut être réutilisé plus de dix fois sans perte notable d’activité
In recent years, tremendous advances in nanotechnology and materials science have led to the synthesis of many new nanoparticles without really knowing all the properties associated with their dimensions. The first part of our work aims to evaluate the risks and problems associated with nanomaterials, in terms of toxicity, using ZnO nanoparticles. We first studied the ability of these nanoparticles to produce reactive oxygen species (ROS) under UV irradiation using three ZnO-based quantum dots (QDs) as models, ZnO, ZnO doped with Cu2+ ions and ZnO with chimisorbed Cu2+ ions at their periphery. The three QDs have a strong capacity of generating ROS but those modified with Cu2+ at their surface were found the be the highest producers. These dots were also found to inhibit more markedly the growth of the E. coli bacteria. The toxicity does neither depend on the amount of photo-generated ROS nor on the amount of Zn(+2) leaked by the QDs, thus indicating that a more complex mechanism should be considered. In a second part, we tried to improve the photocatalytic efficiency of ZnO nanorods by associating these nanomaterials with reduced graphene oxide (rGO). ZnO/rGO composites were prepared by a solvothermal method and applied for the photodegradation of Orange II used as model pollutant. Results obtained demonstrate that the ZnO/rGO photocatalyst is highly efficient under solar and under visible light irradiation and weakly sensitive to pH changes and to the presence of perturbators in the reaction medium. Finally, the photocatalyst is stable and can be reused up to ten times without significant loss of catalytic activity

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Kwiatkowski, Maciej. "ZnO(core)/TiO2(shell) composites: influence of TiO2 microstructure, N-doping and decoration with Au nanoparticles on photocatalytic and photoelectrochemical activity." Doctoral thesis, Bourgogne Franche-Comté, 2017. https://depotuw.ceon.pl/handle/item/2244.

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Efficient use of renewable energies is one of the most difficult technological challenges facing humanity. Among all renewable energy sources, the sunlight is considered as the most abundant and accessible one. To convert it into usable and controllable form, the modern technology relies on generation of electron-hole pairs in semiconductors upon light absorption. The obtained separated charge carriers possess extra energy brought by the converted sunlight which can be further utilized in various ways. Currently, the most common approach consists in its direct transformation into electricity in p-n junctions. Alternatively, the electrons and holes can be used to perform chemical reactions. The electrons can be transferred to reduce various organic compounds or inorganic species, while simultaneously the holes can play the role of oxidizer by subtracting the electrons from the other substances. Through these reactions it would be possible to accumulate the solar energy in chemical species allowing thus to alleviate the intermittence of the sunlight. Unfortunately, the existing materials do not easily cross the laboratory level to realize this approach on industrial scale. That is why the development of new semiconductor photocatalysts, which harvest and convert efficiently the visible part of solar spectrum, is of paramount importance. For many years the most often studied photocatalytic materials have been ZnO and TiO2. However, it has been recently shown that composites based on ZnO and TiO2 possess even more promising properties than many other semiconductors in various photocatalytic applications. Despite many works reporting high photoactivity of these composites in different applications, the detailed information about the structure–properties correlation is lacking. In order to fill this gap we decided to focus our attention to study the influence of microstructure of ZnO/TiO2 composites on their properties in photocatalytic degradation of organic pollutants, and in application in half-reaction of ‘solar fuel’ generation, namely photoassisted water electro-oxidation. To realize such study the composites should satisfy the requirements of a high surface area and good electric conductivity. We chose therefore the design based on ZnO nanorods supported on ITO (Indium Tin Oxide)-coated glass electrode. The ZnO nanorods (NRs) were then covered with a layer of TiO2 under different deposition conditions. The composition and microstructure of the obtained ZnO(core)/TiO2(shell) composites were modified in the aim to elucidate how these parameters influence their photocatalytic activity. Consequently, the efforts were made to impart visible light activity to the elaborated ZnO/TiO2 composites by modifying titanium dioxide layers with nitrogen and decoration with Au nanoparticles. The thesis consists of three parts: Bibliography, Experimental and Results and Discussion. First part of the present PhD thesis, Bibliography, is dedicated to the analysis of literature concerning fundamental properties of semiconductor materials, solid/electrolyte interface as well as principles of photocatalysis and photoelectrochemical water oxidation. Also, the photocatalytic properties of ZnO and TiO2, and those of their composites are reviewed in this section. Furthermore, methods for improvement visible-light absorption are also described, i.e. N-doping and surface plasmonic effects due to the noble metal nanoparticles (Au NPs) deposited on semiconductors. The second part, Experimental, covers the preparation procedures and characterization techniques used in the work. First, the details are given for electrochemical seeding of ITO support, hydrothermal growth of ZnO nanorods, sol-gel deposition of TiO2 (and N-doped TiO2), and photodeposition of Au NPs. Second, the characterization techniques used in realization of this project are described: SEM (Scanning Electron Microscopy), HAADF-STEM and HR-TEM (High Angle Annular Dark Field Scanning Electron Transmission Microscopy and High Resolution Transmission Electron Microscopy), XRD (X-ray Diffraction Analysis), XPS (X-ray Photoelectron Spectroscopy), EDS ‘or EDX’ (Energy Dispersive Spectroscopy) analyses connected with electron microscopy techniques, UV-vis Spectroscopy and DRS (Diffuse Reflectance UV-vis Spectroscopy, TGA-DSC (Thermogravimetry Differential Scanning Calorimetry Analysis), TOC (Total Organic Carbon) analysis, RT-PL (Room Temperature Photoluminescence Spectroscopy), electrochemical techniques including: LSV (Linear Sweep Voltammetry), CV (Cyclic Voltammetry), chronoamperometry, chronopotentiometry, as well as the set-ups elaborated by the author for the purpose of photocatalytic and photoelectrochemical measurements. The main results of the PhD thesis are presented in the third part, Results and Discussion, consisting of four chapters. In the first chapter (Chapter 4.1), the results of the studies on electrochemical seeding of ITO-electrode in Zn(CH3COO)2 solution are presented. The length and width of ZnO nanorods grown by hydrothermal method from Zn(NO3)2 aqueous solution on Zn/ZnO-seeded ITO substrate were shown to depend strongly on initial Zn2+ concentration and the synthesis duration. The arrays of well-separated ZnO ‘obelisk-like’ nanorods of width varied from 100 nm at tips to ~ 300 nm at bottom and average length of 1.9 µm were prepared under optimized conditions, and used as starting point for further fabrication of (core)ZnO/TiO2(shell) composites. In the second chapter (Chapter 4.2), a simple and low-cost sol-gel method was developed in order to form TiO2 thin layers on ZnO nanorods by hydrolysis of titanium(IV) butoxide. The results of studies lead to elaboration of two most distinctive variants of sol-gel procedure that allow to deposit TiO2 layers of controlled thicknesses and different morphology (rugged or compact). The rugged TiO2 layers were obtained after 6 hours of one step sol-gel synthesis followed by calcination of the sample at 450 oC, ensuring formation of anatase-TiO2, whereas the uniform coating of 25 nm – 40 nm thickness was obtained via three successive 30 min-synthesis with the intermediate calcination of the sample after each deposition cycle. The composite containing the rugged TiO2 layer was shown to possess significantly higher activity in model pollutant (methylene blue, MB) degradation and in photoassisted H2O electro-oxidation under 400 nm monochromatic light irradiation. This improved photoactivity was correlated with the composite microstructure and attributed to a higher porosity and better accessibility of ZnO/TiO2 interface region through the rugged TiO2 layer by the reagents. The TiO2 (shell) layers of similar morphology were also prepared by atomic layer (ALD) and chemical vapor deposition (CVD) techniques and it was shown that the composites fabricated by us with the use of simple sol-gel procedure yield comparable (or even higher) photoactivity. Finally, it was confirmed by total organic carbon (TOC) analysis that the ZnO/TiO2 composites elaborated in this work are also active in decomposition of the pollutants in a dumb hill leachate solution (waste water) under 400 nm monochromatic irradiation. In Chapter 4.3 it is shown that the ZnO/TiO2 interface plays a key role in enhancement of photodecomposition of MB under 400 nm illumination. The increase of photocatalytic activity was attributed to the shift of absorption edge of ZnO/TiO2 towards visible light in comparison to that of the ZnO(core)-etched TiO2. Further enhancement of photocatalytic activity of ZnO/TiO2 was achieved through its additional calcination at 450 °C for 3 h. This simple treatment brings 40% increase in the rate of MB decomposition and a two-fold rise of the photocurrent in H2O oxidation. Measurements of open circuit potential (VOC) showed that the improved properties of additionally calcined ZnO/TiO2 composites stem from the decrease of electron-hole recombination rate. STEM (Scanning Transmission Electron Microscopy) studies showed that the additional calcination resulted in formation of voids at the ZnO/TiO2 interface. EDX (Energy Dispersive X-ray) analysis and XPS (X-ray Photoelectron Spectroscopy) results proved that formation of voids is accompanied by the outward diffusion of Zn ions into TiO2 layer and allowed to conclude about the existence of the Kirkendall effect at ZnO/TiO2 interface. Occurrence of this effect observed for the first time at unusually moderate temperature (450 °C) was shown and attributed to a highly defective nature of the surface layer of the ZnO nanorods. In the last chapter (Chapter 4.4), the composites consisting of ITO-supported ZnO nanorods covered with nitrogen-doped titanium dioxide, TiO2(N), shell were decorated with gold nanoparticles (Au NPs) in order to improve their photocatalytic activity under visible light. The photocatalytic properties of ZnO/TiO2/Au and ZnO/TiO2(N)/Au ternary composites were studied under illumination with Xe lamp equipped with a 400 nm cut-off filter. It was found that low Au NPs loading (0.37% at.) resulted in 60% enhancement of photocatalytic decolorization of MB under visible light with respect to the Au-free sample owing to plasmonic effects. Also, a simultaneous N-doping and Au NPs-decoration allows to multiply by three the photocurrent in photoelectrochemical water oxidation at the potential of 0.8 V vs. Ag/AgCl. It was also demonstrated that the Au-decorated composites possess a strong electrocatalytic activity in reduction O2 to active oxygen species (via formation of O2⦁– radicals) under a small negative bias (–0.25 V vs. Ag/AgCl) in dark. Illumination of the polarized sample with visible light was shown to enhance this process resulting in rapid decomposition a model pollutant (MB) even in the presence of Na2SO4. This approach allows to completely overcome a problem of inhibition of the photocatalytic process by dissolved inorganic salts on non-polarized catalysts, thus meeting the aim of promising material for photoelectrocatalytic remediation of waste water, often containing a significant amount of inorganic ions.

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Rogé, Vincent. "Etude, fabrication et caractérisation de nanostructures catalytiques de type ZnO/SnO2 intégrées à des membranes modèles pour la dépollution de l'eau." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAF046/document.

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La dépollution de l'eau est un des enjeux majeurs du XXIème siècle. Si différentes techniques de retraitement existent déjà, nous investiguons une nouvelle méthode associant les propriétés des membranes filtrantes à celles des matériaux photocatalytiques. Ainsi, nous avons étudié la croissance et l'activité photocatalytique de structures de type noyau/coquille de ZnO/SnO2 intégrées dans des membranes méso-poreuses (alumine poreuse) et macro-poreuses (fibres de verre). L'activité photocatalytique de ces matériaux a été évaluée sur des polluants modèles tels que le bleu de méthylène ou l'acide salicylique, mais aussi sur des polluants organiques identifiés dans les eaux de la rivière luxembourgeoise Alzette. L'impact environnemental des matériaux développés a été déterminé grâce a des analyses de cytotoxicité sur des cellules colorectales de type Caco-2, ainsi que sur des bactéries marines de type Vibrio Fischeri
Water treatment is one of the main challenge to overcome on the XXIst century. If many different techniques already exist, we investigate a new process associating the properties of porous membranes and photocatalytic materials. Thus, we studied the growth and photoactivity of core/shell structures of ZnO/SnO2 integrated into mesoporous (AAO) and macro-porous (glass fiber) membranes . The photocatalytic activity of these materials has been evaluated on organic pollutants like methylene blue or salicylic acid, but also on molecules found in the Luxembourgish Alzette river. The environmental impact of the synthesized structures has been determined with cytotoxic analyses on Caco-2 cells and Vibrio Fischeri bacteria

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Habba, Yamina Ghozlane. "Étude des nanostructures de ZnO pour leur application dans l'environnement : détection de gaz et dépollution de l'eau." Thesis, Paris Est, 2017. http://www.theses.fr/2017PESC1094/document.

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L’oxyde de zinc (ZnO) est un semi-conducteur II-VI remarquable et très prometteur dans le développement des nouveaux matériaux pour l’énergie renouvelable et pour l’environnement. ZnO est l’un des rares matériaux multifonctionnels. Grâce à ses nombreuses propriétés physiques, chimiques et optoélectroniques très intéressantes, lui confèrent d’être un matériau utilisé dans différents domaines d’applications telles que les cellules solaires, les diodes électroluminescentes, les capteurs de gaz, la dépollution de l’eau et de l’air par effet photocatalytique, etc.Dans cette thèse, nous nous sommes intéressés tout d’abords à optimiser l’élaboration de nanofils de ZnO (ZnO NWs) par méthode hydrothermale. Un procédé à deux étapes a été optimisé qui nous a permis d’obtenir des nanofils de ZnO ayant des excellentes propriétés morphologiques et structurales, avec une très bonne reproductibilité. Une nouvelle méthode d’élaboration, dite Electrospinning, a été mise au point. Ce procédé nous permet d’obtenir des micro- et nanofibres contenant des nanocristallites de ZnO. La combinaison des deux méthodes de synthèse nous a permis d’obtenir des nanostructures hiérarchiques de ZnO (NWs/NFs) possédant une surface effective beaucoup plus importante que la nanostructure classique (ZnO NWs).Deux applications ont été développées dans cette thèse. Dans un premier temps, des tests de détection de trois gaz réducteurs ont été réalisés sur les deux types de nanostructures de ZnO. Par la suite, une étude de purification de l’eau par effet photocatalytique a été réalisée sur un réseau de nanofils de ZnO sous irradiation UV pour les trois colorants (MB, MO et AR14). Afin d'améliorer la performance de la photocatalyse, deux nouvelles méthodes ont été développées. La première consiste à mettre en place un système microfluidique en utilisant des microréacteurs contenant des nanofils de ZnO comme photocatalyseur permettant ainsi à raccourcir considérablement le temps de dépollution. La seconde méthode est basée sur un procédé de dopage de ZnO permettant ainsi d’améliorer l'efficacité de la photocatalyse
Zinc oxide (ZnO) is a remarkable and very promising wide-gap II-VI semiconductor in the development of new materials for renewable energy and for the environment. Thanks to its many interesting physical, chemical and optoelectronic properties, this multifunctional material is used in many application fields such as solar cells, light emitting diodes, gas sensors, and water & air purification by photocatalytic effect, etc.In this thesis, we were interested in optimizing the synthesis of ZnO nanowires (ZnO NWs) by hydrothermal method. A two-step process has been optimized allowing us to obtain ZnO NWs having excellent morphological and structural properties, with very good reproducibility. A new synthesis method “Electrospinning” has been developed and the micro- & nanofibers containing ZnO nanocristallites can be obtained by this process. The combination of the two synthesis methods results a hierarchical nanostructure of ZnO (NWs/NFs) with an effective surface much larger than the classical one (ZnO NWs).Two applications have been developed in this thesis. Firstly, three reducing gases sensing tests have been carried out on the two types of ZnO nanostructures. Then, a photocatalytic water purification study has been carried out on a ZnO nanowire array under UV irradiation for the three dyes (MB, MO and AR14). In order to improve the photocatalysis performance, two new methods have been developed. The first is to set up a microfluidic system using microreactors containing ZnO NWs as a photocatalyst, thus the depollution time has been considerably shortened. The second method is based on the ZnO doping in order to improve the photocatalysis efficiency

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Espindola, Juliana da Silveira. "Produção fotocatalítica de hidrogênio a partir de soluções de etanol em água." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2010. http://hdl.handle.net/10183/26038.

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O presente trabalho tem o objetivo de investigar a obtenção de hidrogênio a partir de soluções de etanol em água, por fotocatálise, usando-se catalisadores a base de óxido de zinco (ZnO). Nestes estudos foram empregados cinco catalisadores ZnO, sendo um comercial e os demais preparados através de diferentes metodologias encontradas na literatura. Os catalisadores foram caracterizados por área BET, DRX e FRX, e a investigação preliminar da atividade destes catalisadores foi feita através de ensaios de degradação fotocatalítica de rodamina B em reator slurry em batelada, onde foram avaliadas a taxa de reação e a remoção de corante. Os ensaios para a produção fotocatalítica de hidrogênio foram realizados em um reator de quartzo, operado em batelada com catalisador em suspensão e atmosfera inerte de nitrogênio. A solução foi irradiada por uma série de seis lâmpadas compactas de luz negra. Ao longo dos testes, amostras das fases líquida e gasosa foram coletadas e analisadas para identificação do consumo de etanol e produção de hidrogênio usando-se, respectivamente, Carbono Orgânico Total (TOC) e Cromatografia Gasosa (GC). Resultados preliminares mostraram que os catalisadores ZnO comercial e sintetizado (ZnO Merck e ZnO-B) apresentam atividade fotocatalítica e desempenho similares aos do TiO2 para a degradação da rodamina B. Contudo, estes mesmos catalisadores mostraram-se pouco ativos para a produção fotocatalítica de hidrogênio, com desempenho bastante inferior ao do TiO2 nas mesmas condições. Foi possível observar que o maior rendimento em hidrogênio ocorre para baixas concentrações de catalisador (0,05 gL[elevado a potência menos]1) e elevadas concentrações de etanol, sendo pouco dependente do pH.
This work aims to investigate the hydrogen production from ethanol-water solutions through photocatalysis, using zinc oxide catalysts (ZnO). Five ZnO catalysts were employed in this work; one was a commercial catalyst, while the others were prepared according to different methodologies reported in the literature. The catalysts were characterized by BET, XRD and XRF, and the preliminary investigation of their activity was done by photocatalytic degradation of rhodamine B, through the evaluation of the reaction rate and dye removal. Tests for photocatalytic hydrogen production were carried out in a quartz slurry batch reactor under nitrogen, irradiated by a set of six compact UV light bulbs. During the tests, gas and liquid samples were collected and analyzed in order to identify the consumption of ethanol and hydrogen production using, respectively, Total Organic Carbon (TOC) and Gas Chromatograph (GC). Preliminary results showed that the synthesized and commercial ZnO catalysts (ZnO-B and ZnO Merck) present photocatalytic activity and performance similar to TiO2 for the rhodamine B degradation. However, the ZnO catalysts presented lower performance when compared with TiO2 for hydrogen production, under the same conditions. It was observed that the highest hydrogen yield occurs for low concentrations of catalyst (0.05 gL1) and high concentrations of ethanol, being less dependent on pH.

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Santos, Patrícia Barros. "Estudo da fotodegradação no visível do corante Reactive Black 5 por catalisadores plasmônicos híbridos Ag∕ZnO e Cu∕ZnO." Universidade Federal de Juiz de Fora (UFJF), 2016. https://repositorio.ufjf.br/jspui/handle/ufjf/4408.

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CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
O presente trabalho consistiu na síntese e caracterização de catalisadores plasmônicos nanoestruturados híbridos metal∕semicondutor, para aplicação na fotodegradação do corante têxtil Reactive Black 5 (RB5), utilizando irradiação no visível. Foram sintetizadas nanopartículas de óxido de zinco, cobre (CuNPs) e prata (AgNPs), bem como catalisadores plasmônicos híbridos do tipo Cu∕ZnO e Ag∕ZnO que foram submetidos a diversas técnicas de caracterização como, espectroscopia Raman, UV-VIS, DRX de policristais, MEV e MET. Os processos de fotodegradação foram realizados em um reator labmade, no qual a solução de corante (1×10-5mol L-1) foi irradiada utilizando lâmpada fluorescente (11W) e∕ou incandescente (100W) como fontes de irradiação no visível. A fotodegradação do corante RB5 foi monitorada através de espectroscopia eletrônica no UV-VIS, espectroscopia vibracional Raman ressonante (RR) e intensificada por superfície (SERS), sendo possível observar mudanças relacionadas ao processo de fotodegradação. A espectroscopia no UV-VIS mostrou a queda na intensidade da banda de absorção do grupo cromóforo com o tempo de irradiação; por outro lado, RR e SERS permitiram observar a formação de espécies fluorescentes e mudanças no perfil espectral vibracional. Não ocorreu a fotólise do corante por nenhuma das duas fontes de irradiação utilizadas. AgNPs não promoveram a fotodegradação do RB5, porém nanopartículas de ZnO degradaram cerca de 66% das moléculas de corante, sob irradiação no visível (lâmpada incandescente). Fotocatalisadores plasmônicos do tipo Ag∕ZnO foram utilizados nos processos de degradação do RB5 utilizando ambas as fontes de irradiação no visível, sendo adicionados ao meio do corante de formas diferentes. Quando utilizado diretamente em suspensão e sob irradiação da lâmpada fluorescente o percentual de fotodegradação foi de 97%. Já com a adição do catalisador no estado sólido à solução de corante e sob irradiação da lâmpada fluorescente 72% das moléculas de RB5 foram degradadas. Esse último resultado pode ser comparado ao obtido utilizando ZnO como catalisador, e mostra um ganho de 22% na eficiência catalítica no visível na presença do material plasmônico AgNP/ZnO.
The present work consisted in the synthesis and characterization of plasmonic nanostructured hybrids metal∕semiconductor catalysts, for application on photodegradation of the Reactive Black 5 (RB5) textile dye using visible irradiation. Nanoparticles consisting of zinc oxide, copper (CuNPs) and silver (AgNPs) were synthesized, as well as plasmonics catalysts of Cu∕ZnO and Ag∕ZnO types. The materials underwent several characterizations using techniques such as Raman Spectroscopy, UV-VIS, polycrystal DRX, SEM and TEM. Photodegradation processes were carried out in a labmade reactor, in which a dye solution (1×10-5mol L-1) was irradiated using fluorescent (11W) and∕or glowing (100W) lamp bulb as sources of radiation in the visible range. The photodegradation of the RB5 dye was monitored through electronic spectroscopy UV-VIS, and vibrational spectroscopies resonant Raman (RR) and surface enhanced Raman spectroscopy (SERS). UV-VIS allowed observing changes related to the photodegradation process, as a drop in intensity of the absorption band of the chromophoric group. RR and SERS techniques results presented the formation of fluorescent species and changes in the vibrational spectral profile. The photolysis of the dye didn’t occur under any of the sources of irradiation used. AgNPs didn’t promote the photodegradation of the RB5, but nanoparticles of ZnO degraded about 66% of the dye molecules, under the visible radiation (incandescent lamp). Plasmonics photocatalysts Ag∕ZnO were used in the processes of degradation of the RB5 using both sources of irradiation in the visible range, but it was added to the dye solution in different ways. When used directly in suspension and under fluorescent lamp irradiation the photodegradation percentage was 97%. With the addition of the catalyst in the solid state to the dye solution and under fluorescent lamp irradiation 72% of the RB5 molecules were degraded. This last result can be compared to that achieved using ZnO as catalyst and shows a 22% gain in catalytic efficiency under visible light in the presence of the plasmonic material AgNP/ZnO.

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Machado, Tiele Caprioli. "Degradação fotocatalítica de rosuvastatina em solução aquosa empregando ZnO em suspensão : cinética, subprodutos e toxicidade." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2011. http://hdl.handle.net/10183/36407.

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No presente trabalho se estuda a degradação fotocatalítica de rosuvastatina, fármaco usado para redução dos níveis de colesterol no sangue, empregando-se ZnO como catalisador. Os experimentos foram realizados em um reator batelada de vidro com controle de temperatura, sob radiação UV. Avaliou-se a influência das principais variáveis operacionais na velocidade da reação, como concentração de catalisador, pH inicial da solução e concentração inicial de rosuvastatina. Ensaios preliminares de fotólise e adsorção foram realizados a fim de verificar seus efeitos na degradação do fármaco. A avaliação dos produtos de degradação foi realizada por cromatografia líquida acoplada à espectrometria de massas. Também foram feitos testes de toxicidade aguda com Daphnia magna. Além disso, foi estudada a atividade fotocatalítica de outros três catalisadores ZnO sintetizados. Os resultados experimentais mostraram que a degradação fotocatalítica de rosuvastatina é um processo majoritariamente fotocatalisado e que, com 1h de reação, na presença de ZnO comercial, 75% do fármaco é degradado, seguindo uma cinética de pseudoprimeira ordem. Para o caso de fotocatálise empregando ZnO comercial, os subprodutos mostraram-se mais tóxicos e mais refratários que o contaminante inicial. Além disso, o TiO2 apresentou menor toxicidade aguda do que o ZnO e a Daphnia magna mostrou alta sensibilidade a estes subprodutos. Todos os catalisadores, utilizados neste trabalho, apresentaram atividade fotocatalítica, sendo que os catalisadores sintetizados (ZnO-I, II e III) apresentaram um desempenho menor que o ZnO comercial na reação de degradação da rosuvastatina. Observou-se que a atividade fotocatalítica do ZnO é fortemente influenciada pela metodologia de preparação do catalisador, dado que o percentual de degradação da rosuvastatina diferiu entre os catalisadores, sendo o ZnO-I o catalisador que apresentou melhor desempenho entre os sintetizados, com degradação da estatina de 46%, resultado similar ao obtido para o catalisador TiO2 comercial.
The photocatalytic degradation of Rosuvastatin, a drug used to reduce blood cholesterol levels, employing ZnO as catalyst was studied in this work. The experiments were carried out in a UV irradiated batch reactor, equipped with temperature control. The effect of catalyst concentration, initial pH and initial Rosuvastatin concentration were evaluated. Photolysis and adsorption tests were conducted to verify their effects on drug degradation. The evaluation of the degradation products was performed by nano-ultra performance liquid chromatography tandem mass spectrometry. Acute toxicity tests with Daphnia magna were also carried out. Additionally, we studied the photocatalytic activity of three other ZnO catalysts prepared in our lab. The experimental results showed that rosuvastatin degradation is mainly a photocatalytic process which follows a pseudo-first order kinetics and, when using commercial ZnO, presents 75% degradation after a 1h reaction time. When employing commercial ZnO, these products also proved to be more toxic and resistant than rosuvastatin. Furthermore, TiO2 showed lower acute toxicity than ZnO catalyst and Daphnia magna was found to be very sensitivity to these byproducts. All catalysts used in this study demonstrated photocatalytic activity and the prepared catalysts (ZnO-I, II e III) were less efficient than the commercial one in the rosuvastatin degradation reaction. ZnO photocatalytic activity was affected by the catalyst's preparation method. The ZnO-I presented the best performance among the synthesized catalysts, presenting 46% of statin degradation. The same result was obtained for the TiO2 catalyst.

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Guerra, Wilson Nunes de Almeida. "Descoloração e Mineralização de Corantes Reativos por Processo Fotocatalítico Utilizando ZnO e Radiação UV." Universidade do Estado do Rio de Janeiro, 2009. http://www.bdtd.uerj.br/tde_busca/arquivo.php?codArquivo=9144.

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Fundação de Amparo à Pesquisa do Estado do Rio de Janeiro
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Conselho Nacional de Desenvolvimento Científico e Tecnológico
As indústrias consomem volumes elevados de água e outras substâncias químicas na síntese dos seus produtos e geram grande quantidade de rejeitos. Entre os mais importantes poluentes encontrados nos efluentes dessas indústrias estão os corantes sintéticos que representam um problema, pois não são facilmente destruídos por tratamentos convencionais. A fotocatálise heterogênea tem sido considerada como uma alternativa efetiva no tratamento de efluentes contendo esses corantes. Neste trabalho, estudou-se a cinética de descoloração e o grau de mineralização dos corantes sintéticos reativos Yellow 145, Black 5, Red 4 e Blue 21 através da fotocatálise utilizando ZnO puro e impregnado com íons Fe2+ e Co2+. Testes preliminares foram realizados para otimizar a concentração dos corantes e a massa mínima de catalisador a ser utilizado nos experimentos fotocatalíticos. Além da fotocatálise, experimentos individuais de fotólise e adsorção também foram realizados, porém se mostraram poucos eficientes. Através da espectrofotometria UV-Vis, verificou-se o total descoramento individual dos corantes em aproximadamente 30 minutos de irradiação com ZnO. O grau de mineralização de cada corante foi determinado através de análise de carbono orgânico total (COT), atingindo-se cerca de 70 a 80% de mineralização após 240 minutos de tratamento fotocatalítico. Foram comparadas, ainda, as eficiências de cada fotocatalisador ZnO, Fe/ZnO e Co/ZnO na mineralização de uma solução contendo a mistura dos quatro corantes já mencionados após 240 minutos de reação. A eficiência na mineralização da mistura dos corantes seguiu a seguinte ordem: Co/ZnO (32%), ZnO (78%) e Fe/ZnO (87%). A reação de degradação fotocatalítica do corante Black 5 seguiu uma cinética de primeira ordem, enquanto que os corantes Yellow 145, Red 4 e Blue 21 seguiram uma cinética de ordem zero.
Industries consume a huge amount of water and other chemical substances in the synthesis of their products and generate an elevated quantity of waste. Among the most important pollutants found in textile wastewaters are the synthetic dyes, that are not destroyed by conventional treatments. Alternatively, the heterogeneous photocatalysis is considered an affective treatment for wastewaters containing strong coloration. In this work, it was studied the decoloration kinetics and the degree of mineralization of four reactive dyes (Yellow 145, Black 5, Red 4 and Blue 21) in presence of UV irradiation and pure ZnO or impregnated ZnO with ions Fe2+ and Co2+ as photocatalysts. Preliminary tests indicated the optimal initial dyes concentration and the minimum amount of catalyst to be used in the photocatalytic experiments. In addition to the photocatalitic tests, individual experiments of photolysis and adsorption were also conducted, but they were not efficient. Results from UV-VIS spectrophotometry revealead the total color removal after 30 minutes of photocatalytic treatment with ZnO. Mineralization determined by total organic carbon (TOC) analyses showed that photocatalytic treatments were quite efficient achieving up to 80% of mineralization after 240 minutes of irradiation with ZnO. The efficiency of each photocatalyst ZnO, Fe/ZnO and Co/ZnO in the mineralization of a solution containing the four dyes mixture was also compared. After 240 minutes of irradiation, the mineralization of the dyes mixture presented the following order: Co/ZnO (32%), ZnO (78,8%) and Fe/ZnO (87,26%). The photocatalytic degradation of Black 5 dye followed a first order kinetic, while Yellow 145, Red 4 and Blue 21 dyes decoloration followed a zero order model

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Zhang, Yangyang. "Modeling and Design of Photocatalytic reactors for Air Purification." Scholar Commons, 2013. http://scholarcommons.usf.edu/etd/4621.

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Photocatalysis is a promising technique for the remediation of indoor air pollution. Photocatalysis utilizes semiconductor photocatalysts (such as TiO2 or ZnO) and appropriate light to produce strong oxidizing agents (OH*) that are able to break down organic compounds and inactivate bacteria and viruses. The overall goal of the research is to develop an efficient photocatalytic reactor based on mass transfer for indoor air purification. This study has focused on the enhancement of the effectiveness of the photocatalytic process by the introduction of artificial roughness on the reactor catalyst surface. The major effect of artificial roughness elements on the catalytic surface is to create local wall turbulence and enhance the convective mass transfer of the contaminants to the catalyst surface and thus lead to an increase in the effectiveness of photocatalysis. Air flow properties in a model photoreactor channel with various roughness patterns on the interior wall surface were theoretically investigated. The optimum shapes, sizes, and arrangements of roughness were determined for the maximum enhancement of turbulence intensity in the channel. The possible order of photocatalytic reactor performance for various roughness patterns was also determined. In order to verify the theoretical analysis results, experimental studies were carried out. A plate type photocatalytic reactor was designed and fabricated on the basis of the theoretical results. It was determined that the photocatalytic reactor performance is greatly improved with various rough catalyst surfaces. The experimental results verified the theoretical results. The relationship between the overall reaction rate constant (k) of the reactor and the magnitude of the turbulence intensity was found out. An empirical correlation expression was also proposed. This is the first study of the effect mass transfer in a rough catalytic surface for photocatalytic reactor. Photocatalyst development has also been studied. Zinc oxide (ZnO) and iron doped zinc oxide (ZnO/Fe) nanowires were synthesized on glass substrates through a conventional hydrothermal method. The photocatalytic activities under ultraviolet (UV) light and white light irradiation were separately investigated. The ZnO/Fe nanowires exhibited an enhanced photocatalytic activity as compared to ZnO nanowires regardless of the type of contaminants and light sources.

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Franco, Marcela Andrea Espina de. "Degradação fotocatalítica de nicotina em solução aquosa empregando ZnO, TiO2 e catalisadores não convencionais em suspensão." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/98129.

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O presente trabalho estuda a degradação fotocatalítica da nicotina em solução aquosa, um alcaloide altamente tóxico que tem sido detectado em efluentes, águas subterrâneas e água mineral. Os experimentos foram realizados em um reator batelada sob irradiação ultravioleta, tendo sido avaliadas três principais variáveis: concentração inicial do contaminante, concentração de catalisador e pH inicial da solução. Foram realizados dois planejamentos de experimentos para os catalisadores comerciais ZnO e TiO2, com o objetivo de encontrar a melhor condição para promover a degradação da nicotina em água. Outros catalisadores, preparados a partir de resíduos industriais e laboratoriais, foram testados nas condições otimizadas. O método analítico empregado para quantificar a nicotina nas amostras foi a cromatografia líquida de alta eficiência, o que permitiu registrar a formação de intermediários e subprodutos de reação. Os resultados experimentais demostraram que a degradação da nicotina por fotocatálise heterogênea é um processo bastante eficiente. Em ambos os planejamentos, o pH foi a variável que exerceu o maior efeito sobre a degradação, sendo este fortemente positivo. Já a concentração inicial de nicotina exerceu efeito negativo sobre a resposta e a concentração de catalisador em suspensão exibiu um ponto ótimo, que correspondeu a 0,91 g.L-1 para o ZnO, e 1,20 g.L-1 para o TiO2. Ensaios foram realizados nas condições otimizadas encontradas, onde cerca de 98% da molécula foi degradada utilizando ZnO em suspensão e 88% empregando TiO2, em uma hora de reação. A degradação fotocatalítica da nicotina demonstrou seguir uma cinética de pseudoprimeira ordem dentro do tempo de reação de 60 minutos, para os dois catalisadores comerciais. Entre os catalisadores não convencionais que foram testados, aquele que demonstrou o maior percentual de degradação foi obtido a partir de resíduo de uma indústria petroquímica, cerca de 43%.
The present work studies the photocatalytic degradation of nicotine in aqueous solution. This alkaloid is highly toxic and it has been detected in wastewater, groundwater and mineral water. The experiments were performed in a batch reactor under ultraviolet radiation. Three main variables of process were evaluated: initial concentration of pollutant, catalyst concentration and initial pH of the solution. Two experimental designs were performed for commercial catalysts ZnO and TiO2. The purpose was to find the best condition to promote the nicotine degradation in water. Other catalysts prepared from industrial and laboratory waste were tested under the optimized conditions. Analytical method used to quantify nicotine and its degradation products in all samples was high performance liquid chromatography. Experimental results showed that nicotine degradation by heterogeneous photocatalysis is a very efficient process. In both designs, initial pH was the most significant variable which has a strong positive effect. Initial nicotine concentration showed a negative effect, and catalyst concentration exhibited an optimal value for both commercial catalysts: 0,91 g.L-1 using ZnO, and 1,20 g.L-1 with TiO2. At the best conditions, about 98% of the molecule was degraded using ZnO and 88% with TiO2. Photocatalytic nicotine degradation followed a pseudo first order kinetic until 60 minutes of reaction for both commercial catalysts. Among the non-conventional catalysts tested, the one prepared from a petrochemical industry residue exhibited the highest photocatalytic degradation, about 43%.

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Bagnara, Mônica. "Investigação dos efeitos das variáveis de síntese na atividade fotocatalítica de nanobastões de ZnO e sua aplicação na degradação de compostos orgânicos voláteis." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2016. http://hdl.handle.net/10183/140611.

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A crescente urbanização e modernização leva a população a passar cada vez mais tempo em ambientes fechados e com climatização artificial. Estes ambientes são propícios para o desenvolvimento de contaminantes, como compostos orgânicos voláteis e microrganismos, os quais estão diretamente relacionados a problemas de saúde. Neste trabalho, propõe-se o uso de fotocatálise heterogênea para remoção de poluentes orgânicos presentes no ar. O semicondutor escolhido como fotocatalisador para este trabalho foi o óxido de zinco, que possui uma grande capacidade de absorção de luz UV. Inicialmente um estudo sistemático das condições de síntese de microestruturas de ZnO imobilizadas sobre diferentes substratos foi realizado com base em um planejamento de experimentos composto central circunscrito. Foram avaliadas as razões molares dos reagentes NaOH e D-frutose em relação à quantidade de Zn2+ presente no meio reacional, o tempo e a temperatura de síntese. A variável de resposta do sistema foi a porcentagem de degradação de rodamina B sob irradiação de luz ultravioleta por uma hora. Este corante é comumente usado como molécula alvo em ensaios de degradação fotocatalítica servindo de padrão para avaliação da eficiência do catalisador. Os materiais utilizados como substratos para o crescimento das microestruturas foram vidro, cobre e zinco. Os testes realizados permitiram concluir que, dentre os materiais estudados, substrato de zinco é o mais promissor, apresentando uma porcentagem de degradação máxima de 80%. Em relação às condições de síntese, os gráficos de contorno permitem identificar uma região de máxima resposta para o substrato zinco. As variáveis mais significativas do modelo estudado foram a quantidade de NaOH e a temperatura de síntese. Para a segunda etapa desta pesquisa, dois compostos facilmente encontrados em ambientes fechados – limoneno e acetona – foram utilizados como moléculas alvo de compostos orgânicos voláteis. Foram utilizados três reatores com configurações diferentes e três fotocatalisadores para o estudo de degradação fotocatalítica – TiO2 P25, ZnO Merck e nanobastões de ZnO sintetizados em laboratório. Os resultados indicam que o TiO2 apresenta uma maior facilidade de degradação de limoneno do que ZnO, totalizando uma remoção de 70% e 45%, respectivamente. O oposto acontece para acetona, onde ZnO apresentou uma degradação total de 61% e TiO2 48%. Nanobastões de ZnO foram responsáveis pela remoção de menos de 10% de limoneno. Estes resultados indicam a relação da atividade fotocatalítica com a interação entre estrutura do fotocatalisador/molécula alvo.
The increasing urbanization and modernization have led people to spend more and more time indoors and with artificial air conditioning. Such environments are conducive to the development of contaminants, such as volatile organic compounds and microorganisms, which are directly related to health issues. In this work, we propose the use of heterogeneous photocatalysis for organic pollutants removal in air. The semiconductor chosen as photocatalyst for this study was zinc oxide, a material with great UV light absorption capacity. Initially a systematic study of the ZnO microstructures synthesis conditions immobilized on different substrates was performed. In order to do so, a circumscribed central composite design of experiments was developed for each substrate. The reactants molar ratio – NaOH/Zn and Zn/Fructose –, time and temperature of synthesis were evaluated. The response variable was rhodamine B (RhB) degradation percentage using UV light for one hour. This dye is commonly used as a target molecule, been referred as standard test to evaluate the photocatalyst efficiency. The materials used as substrates for microstructures growth were glass, copper and zinc. The experiments shoed that, among the studied materials, zinc substrate is the most promising, with a maximum (RhB) degradation of 80%. Regarding the synthesis condition, the contour plots allow the identification of a maximum response region for the zinc substrate. The most significant variables from the studied model were the molar ratio NaOH/Zn and synthesis temperature. For the following step in this work, two compounds easily found indoors – limonene and acetone – were used as target molecules of volatile organic compounds (VOCs). Three reactors with different configurations, and three photocatalysts – TiO2 P25, ZnO Merck and synthesized ZnO nanorods – were used for the study of photocatalytic degradation. The results indicate that TiO2 has a greater ease of limonene degradation than ZnO, with a total removal of 70% e 45%, respectively. The opposite happens to acetone, where ZnO showed an overall degradation of 61 e 48%, respectively. ZnO nanorods were responsible for less than 10% of limonene removal. This results indicate a relation between photocatalytic activity and photocatalyst structure/target molecule.

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Gao, Lan. "A Dual Approach For Water Purification Based On Solar Energy." Thesis, Université Gustave Eiffel, 2022. https://these.univ-paris-est.fr/intranet/2022/TH2022UEFL2002.

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Dans le contexte de la réduction de la ressource en eau potable à échelle mondiale, un intérêt croissant est porté au développement de technologies efficaces de purification de l'eau. Dans les travaux de cette thèse de doctorat, nous avons exploré le potentiel des micro- et nanotechnologies afin de proposer et évaluer deux méthodes de purification de l'eau, toutes deux entièrement autonomes en énergie et n'utilisant que l'énergie solaire pour leur mise en œuvre. La première méthode consiste en la génération de vapeur d'eau de façon accélérée grâce à la mise en œuvre d'une méta-mousse que nous avons conçus, dont nous avons modélisé et simulé le fonctionnement, puis optimisé pour la rendre la plus efficace en terme de quantité de vapeur générée par unité de temps et par unité de surface. En exploitant le silicium noir nanostructuré et en y rajoutant une micro-structuration bidimensionnelle contrôlée, unesérie de méta-mousses ont été réalisées et évaluées et les résultats ont montré une efficacité de conversion de 89% et une vitesse d'évaporation de 1,34 kg/(h·m2), ce qui représente une performance au-delà de l'état de l'art et proche de la limite théorique. La deuxième méthode est basée sur la photocatalyse. Elle se veut complémentaire de la première car elle permet de purifier les polluants résiduels volatils qui persistent après la mise en œuvre de la première méthode basée sur l'évaporation (et la condensation). Pour répondre aux exigences du traitement de l'eau à grande échelle, il y a deux points importants : L'un est la durabilité incluant la stabilité chimique du matériau photocatalyseur, en particulier dans des conditions extrêmes de pH de l'eau. L'autre est la facilité de synthèse de tels photocatalyseurs avec unenano-structure spécifiques. Sur la base de l'expérience du laboratoire en matière de croissance de nanofils (NWs) de ZnO, connu pour ses excellentes propriétés photocatalytiques, notre principale contribution dans cette thèse a consisté à le rendre plus durable et robuste aux environnements chimiques agressifs. A cet effet, nous avons proposé et évalué une combinaison de ZnO et de TiO 2 , tous deux ayant de hautes performances de dépollution. Cette combinaison a pour objectif de tirer profit des avantages respectifs des deux matériaux: la très bonne robustesse chimique du TiO 2 d'une part et la possibilité de synthétiser du ZnO sous forme de nanofils, donc avec une très grande surface spécifique. Il nous a semblé donc avantageux d'effectuer un revêtement de TiO 2 d'une épaisseur nanométrique sur des nanofils de ZnO (NW) après qu'un réseau homogène de ZnO NW ait été synthétisé. Cet assemblage original du tandem TiO 2 /ZnO nanostructuré a été caractérisé puis nous avons évalué sa durabilité et sa fonctionnalité de purification de l'eau. Notre solution s'est avérée efficace aussi bien dans dessolutions aqueuses fortement acides et fortement basiques. De plus, l'expérience de purification photocatalytique de l'eau des colorants organiques a été démontrée avec succès. Les résultats engrangés dans cette thèse offrent la perspective de valorisation en vue de la réalisation de systèmes de purification d'eau complètement autonomes et à bas coût
In the context of increasing global water scarcity, many efforts have been devoted to developing efficient water purification technologies. In this thesis work, two eco-friendly and promising approaches water purification approaches, surface-enhanced solar steam generation and photocatalysis, are studied to come out with a nano-enabled, fully self-consistent device that operates solely based on sunlight for delivering high-quality water.Surface-enhanced solar steam generation can be applied to purify insoluble and soluble water pollutants. It requires proper active photothermal material surface and optimized porosity to achieve high evaporation efficiency by localizing the heat at the water-air interface during solar steam generation. Herein, Taking the advantage of the characteristics of silicon that can be tailored to the target shape in the nanofabrication process and the high absorptivity of the black silicon, we report a bilayer black absorber sheet consisting of black silicon and commercial foam, being capable of providing superior performance in photothermal conversion, thermal insulation, and water imbibition simultaneously. The porosity of the foam is theoretically optimized by numerical modeling. Subsequent scanning electron microscopy and Fourier-transform infrared spectroscopy characterization and validated experiments revealed that the solar steam generation efficiency was increased to above 88% with the evaporation rate of 1.34 kg/(h·m2) under 1 sun illumination, a pioneering value compared with the state-of-the-art. In addition to insoluble and soluble water pollutants, there are some volatile organic water pollutants that cannot be eliminated by enhanced steam generation. Therefore, the photocatalysis water purification method is also studied, which proved to be effective in degrading organic water pollutants. To meet the requirement of large-scale water treatment, there are two important points: One is the lifetime and chemical stability of the photocatalyst material, especially in complex and harsh aqueous conditions. The other is the ease of synthesis of such photocatalysts with specific nano-morphology. In this thesis work, ZnO and TiO2 these two common photocatalysts are selected due to their high performance in degradation by producing the oxidative free radical after being illuminated by UV light. This involves the combination of both TiO2 and ZnO in a two-step si mple synthesis method. It appears advantageous to exploit the conformal deposition of atomic layer deposition (ALD) to achieve nanometer-thick TiO2 coating on ZnO nanowires (NWs) after a homogeneous ZnO NW array successfully grown using hydrothermal synthesis method with a high aspect ratio, which is firmly anchored to a substrate and exhibit a large specific surface area. After being characterized by energy-dispersive X-ray analysis via high resolution- scanning electron microscopy measurements, the high chemical stability of the ALD TiO2 coating has been investigated in detail and proven to be effective under both strong acid and strong alkaline aqueous solutions. In addition, the photocatalysis for water purification experiments with organic dyes shows that via this simple two-step synthesis method. Finally, it’s proved that the produced ZnO/TiO2 tandem does indeed exhibit improved chemical stability in a harsh environment while allowing efficient photodegradation

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Sugunan, Abhilash. "Photochemical and Photoelectric Applications of II-VI Semiconductor Nanomaterials." Licentiate thesis, KTH, Functional Materials, FNM, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-12808.

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In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated two different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdTe nanotetrapods synthesized by solution-based thermal decomposition of organo-metallic precursors. In both the cases our main focus has been optimizing material synthesis for improving potential applications based on photon-electron interactions.

We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. The synthesis is based on epitaxial growth of ZnO seed-layer on a substrate in a chemical bath consisting of an aqueous solution of zinc nitrate and hexamethylenetetramine (HMT). We have suggested an additional role played by HMT during the synthesis of ZnO nanowire arrays. We have also extended this synthesis method to fabricate hierarchical nanostructures of nanofibers of poly-L-lactide acting as a substrate for the radially oriented growth of ZnO nanowires. The combination of high surface area of the nanofibrous substrate with the flexibility of the PLLA-ZnO hierarchical nanostructure enabled the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system that could effectively decompose single and combination of known organic pollutants in water, as well as render common waterborne bacteria nonviable.

We have studied another chemical synthesis that is commonly used for size controlled synthesis of colloidal quantum dots, which was modified to obtain anisotropic nanocrystals mainly for CdE (E=S, Se, Te) compositions. In this work we demonstrate by use of oleic acid (instead of alkylphosphonic acids) it is possible to synthesize CdTe and CdSe nanotetrapods at much lower temperatures (~180 ºC) than what is commonly reported in the literature, with significantly different formation mechanism in the low-temperature reaction.

Finally, we have performed preliminary photoconduction measurements with CdTe nanotetrapods using gold ‘nanogap’ electrodes fabricated in-house, and obtain up to 100 times enhancement in current levels in the I–V measurements under illumination with a white light source.

QC20100607

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Souza, Bruno Leandro Cortez de. "Estudo da fotocatálise heterogênea utilizando luz solar e ZnO como pré-tratamento de percolado de aterro sanitário." Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/97/97137/tde-14092016-174925/.

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O grande impacto ambiental causado pelo chorume proveniente de aterros sanitários impulsiona as pesquisas para o seu tratamento, com o objetivo de se obter a máxima degradação possível dos seus contaminantes recalcitrantes e tóxicos, diminuindo-se assim a sua toxicidade. O desenvolvimento de uma tecnologia eficiente e econômica para o tratamento é indispensável devido ao grande volume gerado e à legislação ambiental cada vez mais restritiva. Desta forma, os Processos Oxidativos Avançados (POAs) são avaliados como uma estratégia para o pré-tratamento, com um alto poder de degradação não seletivo e relação custo-benefício vantajosa. Dos diversos tipos de POAs existentes, aqueles que utilizam semicondutores para a fotocatálise heterogênea e luz solar como fonte de irradiação são os de maior interesse, devido a sua relativa eficiência, estabilidade fotoquímica, natureza não tóxica e baixo custo. Este estudo consistiu em avaliar o nível de degradação do chorume proveniente do aterro sanitário de Cachoeira Paulista - SP, utilizando como catalisador o ZnO irradiado pela luz solar, que possui um vasto espectro de fotoativação aliado ao seu baixo custo. As variáveis de entrada em dois níveis, foram o pH, o tempo de reação, a espessura da camada de ZnO impregnada sobre uma placa metálica e a concentração do efluente. Como variável resposta os valores de concentração expressa em Carbono Orgânico Total (COT) foi a mais adequada. O planejamento de experimentos utilizado foi o fatorial 23 com duplicata no ponto central. Na etapa delineatória, reduções de 28 % de COT foram alcançadas. A utilização da fotocatálise heterogênea utilizando ZnO fotoirradiado com luz solar se mostrou promissora para ser utilizada como um pré-tratamento do chorume.
The major environmental impact of leachate from landfills drives research to treat it, and aims to obtain the maximum degradation of their recalcitrant and toxic contaminants. The development of an efficient and economical treatment technology is indispensable due to the large volume generated and the increasingly restrictive environmental legislation. Thus, Advanced Oxidation Processes (AOPs) are evaluated as a strategy to pre-treatment with a high power non-selective degradation and advantageous cost-benefit ratio. From various types of POAs, those which use the heterogeneous photocatalytic semiconductor and solar light as the source of irradiation are the most interesting, because of its relative efficiency, photochemical stability, low cost and non-toxic nature. This study have assessed the level of degradation of the leachate from the landfill of Cachoeira Paulista - SP, using ZnO irradiated by sunlight as catalyst, which has a wide spectrum of photoactivation combined with its low cost. The input variables on two levels, were pH, reaction time, the thickness of the ZnO layer impregnated on a metal plate and concentration of the effluent. The most appropriate output variable was concentration, expressed in means of Total Organic Carbon (TOC). For the photocatalytic process, a factorial design (23) was used for the design of experiments. In final stage, reductions of 28% TOC were achieved. The use of heterogeneous photocatalysis using solar photoirradiated ZnO seems to be a great alternative as a pre-treatment of leachate.

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Davis, Rafael. "Otimização da degradação da tetraciclina utilizando a fotocatálise heterogênea com ZnO como catalisador." Universidade Estadual do Oeste do Parana, 2013. http://tede.unioeste.br:8080/tede/handle/tede/1845.

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The aim of this work was to determine the optimal conditions for the degradation of the TC, using the heterogeneous phtocatalysis with ZnO catalyst. Preliminary experiments were conducted to evaluate to efficiency of heterogeneous photocatalysis in the degradation of TC. The degradation was carried out using standard solutions of TC 30 mg L 1. The photocatalytic experiments by using a set of high-pressure mercury lamps as artificial UV irradiation source were performed in laboratory scale. As reactor operational parameters to be optimized by a 33 full factorial experimental design: hydrogen peroxide and zinc oxide as well as the initial solution pH were chosen as variables, keeping constant a reaction time of 60 min. The concentration of TC was determined by UV-Vis spectrophotometry and HPLC. Mineralization and toxicity of the treated solution by photocatalytic process were evaluated based on the total organic carbon (TOC) and antibacterial activity. Second-degree models for the degradation of TC were proposed to model the photocatalytic experiments to obtain optimum values of the reactor operating parameters. Second-degree models were also validated by ANOVA. Predicted yields showed good validation with experimental yields. The hydrogen peroxide did not influence significantly the range studied by factorial experimental design. Was necessary to perform photocatalytic experiments at lower concentrations for hydrogen peroxide. The values of the optimized reactor operational parameters were 6, 2 g L-1 and 175 mg L-1 for initial pH, oxide zinc and hydrogen peroxide concentrations, respectively, for photocatalyses heterogeneous process. Based on this optimized experimental conditions, almost 100% of TC degraded. The TOC and antibacterial activity were determined of treated solutions in optimal conditions. Only 46% of the TOC was mineralized, the remainder as intermediate molecules not presented antibacterial activity, not providing risk to the environment.
O objetivo deste trabalho é determinar as condições ótimas para a degradação da TC, utilizando a fotocatálise heterogênea com o óxido de zinco (ZnO) como catalisador. Foram realizados experimentos preliminares para avaliar a eficiência da fotocatálise heterogênea na degradação da TC. A degradação da TC foi realizada a partir de soluções padrão com a concentração de 30 mg L-1 de TC. Os experimentos foram realizados em reatores de escala laboratorial utilizando fonte de irradiação UV artificial (lâmpada de vapor de mercúrio 125 W). Os parâmetros operacionais do reator: pH inicial, concentrações de ZnO e H2O2, foram otimizados baseados na redução da concentração da TC, a partir de um planejamento fatorial 33 completo com o tempo de irradiação constante em 60 minutos. A concentração da TC foi acompanhada por espectrofotometria UV-Vis e cromatografia líquida de alta eficiência (CLAE). A mineralização da TC e a possível toxicidade do composto degradado pelo processo fotocatalítico foram avaliadas baseadas no carbono orgânico total e na análise de atividade antibacteriana. Para auxiliar na obtenção das condições ótimas dos parâmetros operacionais do reator no processo fotocatalítico as respostas experimentais para a concentração da TC foram ajustados por um modelo previsto de segunda ordem, o qual apresentou uma boa modelagem dos dados, validado pela ANOVA. Como no PEC o H2O2 não influenciou significativamente devido a faixa estudada estar acima do necessário, foi verificado a influência de cada POR em concentrações menores das estudadas no planejamento, para o H2O2 a concentração mínima foi de 100 mg L-1. Os valores ótimos operacionais do reator na degradação da TC utilizando a fotocatálise heterogênea foram: pH 6, [ZnO] 2 g L-1 e [H2O2] 175 mg L-1. Nessas condições, a degradação total da tetraciclina foi alcançada após um período de 60 minutos de reação. Com a solução degradada nessas condições, foi determinado o carbono orgânico total (COT) e realizada uma análise para verificar a atividade antibacteriana onde concluiu que embora apenas 46% do COT tenha sido mineralizado, o restante na forma de moléculas intermediárias da reação, não oferece riscos biológicos aos ecossistemas, pois não apresenta atividade antibacteriana.

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Samanamud, Gisella Rossana Lamas. "Estudo da aplicação de ZnO fotoirradiado com luz solar no tratamento de efluentes de laticínios." Universidade de São Paulo, 2011. http://www.teses.usp.br/teses/disponiveis/97/97136/tde-27082013-101339/.

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Os produtos lácteos são tidos como os alimentos mais perfeitos para o homem devido ao seu alto valor nutritivo. Entretanto, esses produtos vêm refletidos na elevada carga orgânica de efluente gerado. Os Processos Oxidativos Avançados (POA) são métodos químicos baseados na geração de radicais hidroxilas, que promovem a oxidação de compostos orgânicos. O uso de semicondutores no tratamento de efluentes tem sido de grande interesse devido à sua alta eficiência, estabilidade fotoquímica, natureza não-tóxica e baixo custo, especialmente quando a luz do sol é usada como fonte de irradiação. O uso de Óxido de Zinco (ZnO), por exemplo, além de mais econômico, absorve uma fração maior de espectro UV e tem melhor desempenho em pH neutro. Este estudo consistiu em avaliar a aplicação e eficiência da fotocatálise heterogênea (POA) solar com ZnO em termos de percentual de degradação de Carga Orgânica Total (COT) para um posterior tratamento biológico aerado visando melhorar as condições de despejo do efluente de modo a preservar o ecossistema e economia dos recursos naturais. O sistema POA consistiu de um volume fixo de efluente de 3L, de uma chapa metálica 800 x 250 mm revestida com uma formulação de tinta contendo ZnO, um reservatório de vidro, uma bomba centrífuga e aberto para absorção de radiações UV solar. Os resultados foram obtidos e analisados a partir do método de planejamento de experimentos em termos de percentual de degradação de COT. O melhor resultado apresentou um percentual de degradação de COT de 31,5% onde os níves das variáveis estudadas ocorreram em pH 8,0 em chapa de ZnO com espessura de 100 micrômetros (?m), utilizando o efluente in natura e o tempo total de reação de 3 h (180min). O efluente tratado pelo POA solar com ZnO foi submetido ao tratamento biológico aerado. O pH ótimo e a concentração de lodo foram de 6,0 e 5,0 mg/L, respectivamente. O percentual de degradação de COT para os tratamentos combinados foi de 75,1 % para o efluente de laticínios utilizado neste estudo. Isto sugere que o tratamento por POA utilizando ZnO seguido de um Tratamento Biológico Aerado seria uma alternativa promissora no tratamento de efluentes de laticínios.
Dairy products are the most perfect type of food for men due to its high nutritive value reflected on its high organic load of wastewater generated. The Advanced Oxidation Processes (AOP) are chemical methods based on the generation of hydroxyls radicals that promote the oxidation of organic compounds. The use of semiconductors in wastewater treatment has been of great interest owing to its high efficiency, photochemical stability, non-toxic nature and lower costs, especially when sunlight is used as source of irradiation. The use of Zinc Oxide (ZnO), for instance, besides being more economic, it also absorbs a greater range of UV spectrum and it has a better performance on neutral pH. This study consisted in evaluating the application and efficiency of solar photocatalytic oxidation (AOP) with ZnO in percentage terms of removal of Total Organic Carbon (TOC) prior to an aerobic biological treatment aiming to improve the conditions of the disposal of this wastewater in order to conserve the water environment and saving natural resources. The AOP system consisted of a working volume of 3 L, a sheet metal 800 x 250 mm covered with a paint formula containing ZnO, a glass vessel, a pump and an open system in order to collect solar UV radiation. The results were obtained and analyzed from design of experiments in terms of percentage of removal of TOC. The maximum percentage was found to be 31.5 % of removal of TOC and at pH 8.0, thickness of the sheet containing ZnO of 100 micrometers (?m), wastewater in natura and total time of reaction of 3 h (180 min). The solar AOP with ZnO treated wastewater was subjected to an aerobic biological treatment. The optimum pH and sludge loading were of 6.0 and 5.0 mg/L, respectively. The combination of both treatments resulted in 75.1 % of removal of TOC from the dairy wastewater used in this study. This suggests that the AOP using ZnO followed by an aerobic biological treatment would be a promising alternative for the treatment of dairy wastewater.

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Lamiel, Garcia Josep Oriol. "Desenvolupament de models per nanopartícules de TiO2 i ZnO en fotocatàlisis." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/462882.

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En aquesta tesi s’han realitzat càlculs DFT per tal d’estudiar els sistemes TiO2 i ZnO i poder analitzar-ne les característiques de l’estructura electrònica, geometria i estabilitat energètica principalment. Primerament s’ha estudiat el funcionament de diferents metodologies computacionals per veure quina d’elles es la optima per realitzar aquests estudis. Aquesta metodologia ha estat provada i posteriorment utilitzada per els càlculs realitzats sobre el TiO2 i ZnO. Motivats per l’interès en l’estructura electrònica del òxid de titani amb intenció de poder augmentar-ne la seva activitat fotocatalítica. Hem realitzat diferents estudis sobre l’efecte de les vacants d’oxigen i el dòping amb fluor en el band gap del material. Observant com en tots dos casos apareixen estats electrònics nous al band gap del material. També s’ha estudiat el perfil energètic de la difusió de fluor en el sinus del material i l’efecte de l’adsorció de fluor en l’estabilitat de les superfícies de TiO2. Observant com la difusió es á energèticament favorable en certes direccions i que l’adsorció de fluor, apart de generar nous estats electrònics, també canvia l’estabilitat de les diferents superfícies. Fent que les nanopartícules presentin formes diferents i una millor activitat fotocatalítica. Hem extret similars conclusions en el cas de l’adsorció d’ àcid trifluoroacetic, ja que també afavoreix l’increment de la superfície mes reactiva per el TiO2 en la fase anatasa. L’estabilitat relativa i l’evolució de les propietats electròniques de les nanopartícules de TiO2 també ha estat font d’estudi. Observant com per mides inferiors a 125 unitats de TiO2 les nanopartícules no cristal·lines resulten mes estables. Però pera mides superiors, les nanopartícules cristal·lines son mes estables i les seves propietats electròniques convergeixen cap a les del sòlid. Analitzant els nostres resultats hem pogut predir que nanopartícules amb mides compreses entre 18 i 23 nm ja haurien de mostrar propietats i electròniques molt similars a les del sòlid bulk. De forma similar també s’ha estudiat el perfil d’estabilitats relatives de nanopartícules d’òxid de zinc, permetent-nos crear així una imatge del perfil d’estabilitat que presenten cinc famílies de nanopartícules amb diferent forma derivades de les fases mes estables per aquest material. L’estudi s’ha realitzat per un rang de nanopartícules que va des dels pocs àtoms fins a nanocristalls amb mes de 1000, Reportant-ne així les variacions d’estabilitat en front a la mida de partícula. Aquests estudis presentats en aquesta tesi poden ser útils de cara a millorar el coneixement d’aquests materials tan prometedors i poder trobar diferents estratègies per tal de millorar-ne la seva activitat fotocatalítica.
In this thesis DFT based methods have been used in order to study TiO2 and ZnO systems, by analysing their electronic structure, geometrical features and energetic stability. A systematic study of the performance of the different computational methodologies has been carried on in order to find a suitable methodology able to describe the electronic features of these semiconductors. This is a key point because the electronic structure is directly related with its photocatalytic activity. One of its more interesting properties from an energetic and technologic point of view. Once the more suitable methodology to describe TiO2 electronic features was found, we tested it with a set of metal oxides, including ZnO. Obtaining also good results. Interested in the electronic structure of TiO2, and with the aim to improve the description of its photocatalytic activity. We performed several studies about the effect of oxygen vacancies,and fluor doping,on the band gap of the different TiO2 bulk polymorphs. Observing in both cases the new electronics states that lay in the band gap. For the oxygen vacancies the new states where found to be close to the conduction band,meanwhile for the fluordoping they were found to be near the valence band. This last case is very interesting because it can increase the photocatalytical activity of this material by shifting to the visible the type of wavelength absorbed by TiO2. Continuing with the study of the interaction between fluor and titanium oxide, we investigated the diffusion paths of fluor trough the TiO2 lattice and how the adsorption of fluor and trifluoroacetic acid adsorption can affect the electronic structure of the and specially the stability of the different surfaces. Finding how the fluor adsorption have similar effects to doping generating electronic states in the band gap while at same time change the order of stability between the (101) and (001) surfaces. Becoming the second one, which seem to be more active, more stable and subsequently more exposed. The same effect on the surface stability was found for the fluoroacetic acid adsorption. We also studied the stability and electronic structure of TiO2 nanostructures sampling a range that goes from a few atoms to more than 1000. Analysing the data obtained we found that the electronic properties depend on the shape significantly for the smaller nanoclusters but not for the larger nanoparticles. Where the size has a stronger effect on the electronic structure. It was also observed the non-crystalline nanoparticles to be more stable than the crystalline ones up to a size approximately 125 TiO2 units. This is an important point to predict the different properties expected for particles of a certain size. Also from the results obtained for the larger crystalline nanoparticles we observed how the electronic properties evolve the bulk ones as the size increases. From this data we could extrapolate that probably nanoparticles with sizes between 18 and 23 nm could present bulk-like electronic structure and subsequently photoactivity. A study in collaboration with experimental co-workers was done in order to explain theoretically the different activity presented by ZnO nanoparticles of different shape. These nanoparticles exposed different proportions of polar and non-polar surfaces. After analysing electronic structure and energetic stability of the different surfaces we found that in this case the higher activity was not closely related with the different electronic features. In the case of these large ZnO nanoparticles the activity was more related about the presence of a larger amount of polar surface exposed. This surface seem to stabilize the holes generated in the process of light adsorption. One last study is included in this thesis. The study about the relative stability of different ZnO nanostructures and its evolution with size. Five families of nanostructures where studied. In a range that goes from few ZnO units to more than 1000. The type of nanostructures studied are. Nano-cages, Multi-layered nano-cages, Sodalite bulk cuts, BCT bulk cuts and Wurtzite bulk cuts. Finding the nano-cages and multi-layered nano- cages especially stable for smaller sizes. When the diameter of the nanoparticles reach the region around 2.6 nm both types of nanocages, sodalite bulk cuts and BCT bulk cuts present very similar stability creating a transition zone. As the size of the particles increases,the BCT bulk cuts become the most stable nanoparticles up to sizes about 4.7 nm where the Wurtzite nanoparticle become the most stable. All these studies presented in this thesis are useful to increase the knowledge about these very promising materials and allow to develop different strategies to improve their photocatalyticactivity.

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Santos, Yane Honorato. "Síntese e caracterização de nanocristais de ZnO suportados e não suportados em diatomita e aplicação fotocatalítica." Universidade Federal de Sergipe, 2017. https://ri.ufs.br/handle/riufs/6076.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Currently there are many studies involving Nanocrystals (NC) incorporated into different types of matrices, including, matrices with porous surface. However, little information is known about the incorporation of NC in Diatomite matrix, and there is a lack of studies on the use of this material. In this context, zinc oxide (ZnO) semiconductor nanoparticles were prepared using two sol-gel methods, microwave and autoclave, at 100 ºC and 180 ºC, respectively. The nanocrystals of ZnO obtained by microwaves were incorporated into a matrix of diatomite (DE) in natura and modified. The modifiers used were APTES (3- aminopropyltriethoxysilane) and MPTS (3-Mercaptopropyltrimetoxysilane) for the study. The material DE/ ZnO, in which ZnO was synthesized with mercaptoethanol (ZnO: ME), was applied for the degradation of Methylene Blue (AM) dye, while ZnO, synthesized with diethyleneglycol (ZnO: DEG), was used for degradation of Rhodamine 6G dye (R6G) by photocatalysis. The results of UV-vis and FTIR spectra show that synthesis carried out by heating under adsorption method is more efficient for the incorporation of ZnO in Diatomite matrix. The FTIR spectra showed that the use of modifiers had no significant influence on the structure. According to the UV-Vis spectra, the DE / ZnO material was successful for application to AM photocatalysis and follows a pseudo-first order kinetics. The ZnO:DEG material used for degradation of R6G obtained higher efficiency due to the wide absorption in the UV-Vis of the photocatalyst material.
Atualmente existem diversos estudos envolvendo Nanocristais (NC) incorporados em matrizes de diferentes tipos, incluindo matrizes com uma superfície porosa. Entretanto, pouco se conhece sobre a incorporação de NC em matriz de Diatomita, além de ser limitado a presença de estudos sobre aplicação desse material. Neste contexto, foram preparadas nanopartículas semicondutoras de óxido de Zinco (ZnO) utilizando dois métodos sol-gel, por micro-ondas e autoclave, numa temperatura de 100 ºC e 180 ºC, respectivamente. Os nanocristais de ZnO obtidos por micro-ondas foram incorporados em matriz de Diatomita (DE) in natura e modificada. Foram utilizados os modificadores APTES (3-Aminopropiltrietoxissilano) e MPTS (3- Mercaptopropiltrimetoxissilano) para o estudo. O material de DE/ZnO, no qual o ZnO foi sintetizado com mercaptoetanol (ZnO:ME), foi aplicado para a degradação do corante Azul de Metileno (AM), enquanto o ZnO, sintetizado com dietilenoglicol (ZnO:DEG), não incorporado foi utilizado para degradação do corante Rodamina 6G (R6G) por fotocatálise. Os resultados de UV-Vis e FTIR mostram que a síntese realizada pelo método de adsorção sob aquecimento é mais eficiente para a incorporação de ZnO na matriz de Diatomita. Os espectros de FTIR mostraram que a utilização de modificadores não exerceu influência significativa na estrutura da DE. Segundo os espectros de UV-Vis, o material de DE/ZnO foi bem-sucedido para aplicação em fotocatálise de AM e segue uma cinética de pseudo-primeira ordem. O material de ZnO:DEG utilizado para degradação de R6G obteve maior eficiência devido a ampla absorção no UV-Vis do material fotocatalisador.

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Sugunan, Abhilash. "Fabrication and Photoelectrochemical Applications of II-VI Semiconductor Nanomaterials." Doctoral thesis, KTH, Funktionella material, FNM, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-95410.

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In this work we investigated fabrication of semiconductor nanomaterials and evaluated their potential for photo-chemical and photovoltaic applications. We investigated different II-VI semiconductor nanomaterial systems; (i) ZnO oriented nanowire arrays non-epitaxially grown from a substrate; and (ii) colloidal CdE (E=Te,Se,S) quantum structures synthesized by solution-based thermal decomposition of organo-metallic precursors. We have studied the synthesis of vertically aligned ZnO nanowire arrays (NWA), by a wet chemical process on various substrates. We have extended this method wherein nanofibers of poly-L-lactide act as a substrate for the radially oriented growth of ZnO nanowires. By combining the large surface area and the flexibility of the PLLA-ZnO hierarchical nanostructure we have shown the proof-of-principle demonstration of a ‘continuous-flow’ water treatment system to decompose known organic pollutants in water, as well as render common waterborne bacteria non-viable. We have studied synthesis of colloidal quantum dots (QD), and show size, morphology and composition tailored nanocrystals for CdE (E=S, Se, Te) compositions. We have studied the influence of crystal growth habits of the nanocrtsyals on the final morphology. Furthermore we have synthesized core-shell, CdSe-CdS QDs with spherical and tetrahedral morphologies by varying the reaction conditions. We show that these core-shell quantum dots show quasi-type II characteristics, and demonstrate with I-V measurements, the spatial localization of the charge carriers in these hetero-nanocrystals. For this purpose, we developed hybrid materials consisting of the core-shell quantum dots with electron acceptors (ZnO nanowires) and hole acceptors (polymeric P3HT nanofibers). In addition we have also compared the synthesis reaction when carried out with conventional heating and microwave-mediated heating. We find that the reaction is enhanced, and the yield is qualitatively better when using microwave induced heating.
QC 20120525

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Roos, Andreine Aline. "Degradação fotocatalítica do princípio ativo sulfametoxazol utilizando como catalisadores o compósito de acetato de celulose/TiO2 e zinco recoberto com ZnO." Universidade Estadual do Oeste do Parana, 2013. http://tede.unioeste.br:8080/tede/handle/tede/1910.

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Made available in DSpace on 2017-07-10T18:08:20Z (GMT). No. of bitstreams: 1 Andreine Aline Roos.pdf: 2960540 bytes, checksum: 99bd1c80529add7a7c94dc586e17b240 (MD5) Previous issue date: 2013-02-22
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
Environmental contamination is a serious problem in today's society and for years aroused the interest of researchers. The pollutants with pharmacological activity are worrying the scientific community by increasing detection of these aquatic environments at concentrations ranging from µ L-1 to ng L-1, which are resistant to conventional treatments used in sewage treatment plants. Thus, it becomes necessary to investigate more effective treatments to minimize environmental contamination. The Advanced Oxidation Processes have attracted interest as promising treatments for removal of organic pollutants, among which stands out the heterogeneous photocatalysis whose the main drawback is the difficulty of separating the catalyst from solution degraded. To try to solve the problem, this work proposes the use of cellulose acetate/TiO2 composite and zinc metal plate coated with ZnO as catalysts for photodegradation of sulfamethoxazole. The composite was prepared by phase inversion of a solution of cellulose acetate and titanium tert-butyl orthotitanate that resulted in a composite with around 4% (in mass %) if TiO2.This composite proved not to be efficient in the degradation of sulfametoxazol in the presence of hydrogen peroxide under both, sunlight or artificial radiation. For this reason the continuity of the work occurred only with zinc plate coated with ZnO obtained by hydrothermal method. The 22 factorial experimental design, with triplicate on central point showed that the model was valid, and that the process was favored with increasing amounts of H2O2 at acidic pH. The equilibrium time for the photodegradation of sulfametoxazol using a plate Zn/ZnO was 120 minutes with removal of 95%, under artificial radiation, obeying the rate law of peudo-first order. The COD and nitrate concentration indicated that there was a small mineralization of the pollutant, despite the high removal, showing that there was probably the formation of intermediate species. Furthermore, the Zn/ZnO showed a catalytic efficiency almost unchanged up to 10 repetitions of photodegradation. However, at the end of the process the zinc concentration in the sample was above the allowed degraded by environmental agencies, necessitating the use of a post-treatment for removal of zinc or use of sulfametoxazol solution with pH closer to neutrality to avoid dissolution of the metal catalyst.
A contaminação ambiental é um grave problema da sociedade atual e há anos desperta o interesse dos pesquisadores. Os poluentes com atividade farmacológica vêm preocupando a comunidade científica pela crescente detecção dos mesmos em ambientes aquáticos, em concentrações que variam de µg L-1 a ng L-1, os quais são resistentes aos tratamentos convencionais empregados nas estações de tratamento de esgoto. Dessa forma, torna-se necessário a investigação de tratamentos mais eficientes para minimizar a contaminação ambiental. Os Processos Oxidativos Avançados vêm despertando interesse como tratamentos promissores para remoção de poluentes orgânicos, dentre os quais destaca-se a fotocatálise heterogênea, cujo principal empecilho é a dificuldade de separação do catalisador da solução degradada. Para tentar solucionar o problema, o trabalho propõe a utilização de catalisadores diferenciados como, compósito acetato de celulose/TiO2 e uma placa de zinco metálico recoberto com ZnO para a fotodegradação do princípio ativo sulfametoxazol. Contudo, o compósito acetato de celulose/ TiO2 não apresentou a eficiência similar ao TiO2 como era esperado, e assim optou-se por prosseguir os estudos de fotocatálise heterogênea utilizando a placa de zinco recoberta com ZnO como catalisador. O planejamento experimental fatorial, 22 com triplicata no ponto central, mostrou que o modelo utilizado foi válido, e que o processo é favorecido com quantidades maiores de H2O2 em pH ácido. O tempo de equilíbrio para a fotodegradação do sulfametoxazol utilizando a placa de Zn recoberta com ZnO foi de 120 minutos com remoções de 95%, sob radiação artificial, seguindo uma lei de velocidade de pseudo-primeira ordem. A determinação de DQO e da concentração de nitrato indicaram que houve uma pequena mineralização do poluente, apesar da elevada remoção, mostrando que provavelmente houve a formação de espécies intermediárias. Além disso, a placa de zinco recoberta com ZnO apresentou uma eficiência catalítica praticamente inalterada em até 10 repetições de fotodegradação. No entanto, ao final do processo a concentração de zinco na amostra degradada estava acima da permitida pelos órgãos ambientais, sendo necessário a utilização de um pós-tratamento para a remoção do zinco ou a utilização de solução de sulfametoxazol com pH mais próximo da neutralidade para evitar a dissolução do metal do catalisador.

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Modesto, Junior Olayr. "Caracterização e aplicação fotocatalítica de compósitos óxidos TiO2/CuO, TiO2/ZnO E TiO2/ZrO2 sintetizados pelos processos Sol-gel e Poliol. /." Bauru, 2018. http://hdl.handle.net/11449/158268.

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Orientador: Dayse Iara dos Santos
Resumo: O desenvolvimento de materiais cerâmicos é um campo de pesquisa cujos resultados são extremamente promissores para aplicações tecnológicas. Particularmente, no caso dos materiais nanoestruturados baseados no óxido titânio, observa-se grande potencial de aplicação em dispositivos optoeletrônicos, bem como, para processos de fotocatálise, visto que apresenta um bandgap direto de 3,2 eV. Além disso, o aperfeiçoamento das propriedades ópticas, por meio da interação entre óxidos de diferentes bandas eletrônicas, têm sido estudado por muitos autores. Por esta razão, compósitos nanoestruturados formados de dois ou mais óxidos, cujas propriedades são distintas quando isolados, têm sido sintetizados juntos e caracterizados a fim de avaliar possíveis interações sinérgicas. Neste trabalho, foram preparados e caracterizados os compósitos TiO2/CuO, TiO2/ZnO e TiO2/ZrO2. As sínteses foram realizadas pelo método Sol-gel original e pelo método Poliol modificado, e ambos os processos se mostraram propícios para a obtenção de nanocompósitos e óxidos nanoparticulados. O método Poliol produziu compósitos formados de partículas micrométricas de dióxido de titânio revestidas do segundo óxido, enquanto o processo Sol-gel resultou em material constituído de agregados de nanocristais com alta mesoporosidade. Por meio da difração de raios X dos pós tratados gradualmente até 1000 °C observou-se que a formação e cristalização dos óxidos ocorrem em temperatura mais alta quando o material é resultante do ... (Resumo completo, clicar acesso eletrônico abaixo)
Abstract: The development of ceramic materials is a field of research whose results are extremely promising for technological applications. Particularly, in the case of nanostructured materials based on titanium oxide, there is a great potential for application in optoelectronic devices, as well as for photocatalysis processes, since it has a direct bandgap of 3.2 eV. In addition, the improvement of the optical properties through the interaction between oxides of different electronic bands has been studied by many authors. For this reason, nanostructured composites formed of two or more oxides, whose properties are distinct when isolated, have been synthesized together and characterized in order to evaluate possible synergistic interactions. In this work the TiO2 / CuO, TiO2 / ZnO and TiO2 / ZrO2 composites were prepared and characterized. The syntheses were carried out using the original Sol-gel method and the modified Polyol method, and both processes proved to be suitable for nanocomposites and nanoparticulate oxides. The polyol method produced composites formed of micrometric titanium dioxide particles coated with the second oxide, while the sol-gel process resulted in material composed of nanocrystalline aggregates with high mesoporosity. By X-ray diffraction of the powders gradually treated to 1000 °C it was observed that the formation and crystallization of the oxides occur at a higher temperature when the material is produced by the Sol-gel process. With the observation of the ... (Complete abstract click electronic access below)
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Andrade, George Ricardo Santana. "Híbridos de ZnO auto-organizado na forma de estrelas e nanopartículas metálicas (Ag, Au) : síntese controlada e avaliação fotocatalítica e antibacteriana." Universidade Federal de Sergipe, 2016. https://ri.ufs.br/handle/riufs/3464.

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Conselho Nacional de Pesquisa e Desenvolvimento Científico e Tecnológico - CNPq
Zinc oxide (ZnO) microparticles with a star-shaped morphology have been synthesized by a novel and simple room-temperature method and decorated with gold (GNP) and silver (SNP) nanoparticles for enhanced photocatalysis and bactericide applications. The presence of thiourea during the precipitation of ZnO in alkaline conditions allowed the control of morphological features (e.g. average size and shape) and the surface functionalization with thiocyanate ions (SCN-). TEM images of the sample prepared at pH 12 suggest that the particles grow according to the oriented attachment mechanism. The emission spectra of these particles showed an interesting feature: the emission band position can be tunable by changing the excitation wavelength. SNPs and GNPs were prepared onto ZnO surface by a photoreduction method and it was found that their sizes can be easily controlled by changing the ZnO/AgNO3 or ZnO/HAuCl4 ratios. The presence of SCN- on the semiconductor surface prevents uncontrollable growth of Ag nanoparticles into different morphologies and high degrees of polydispersity. XRD, SEM, TEM, FTIR, UV-vis-NIR and PL were employed for characterizing the structure, morphology and optical properties of asobtained pure and hybrid nanostructures. Finally, the hybrid ZnO/Ag particles show plasmon-enhanced performance for applications in photocatalysis and antibacterial activity than the pure ZnO counterpart. In this work, it was studied the photodegradation of an aqueous methylene blue solution under UV-A irradiation and antibacterial activity toward 4 bacterial strains, including Gram-positive bacteria Staphylococcus aureus (ATCC 43300, ATCC 25923 and ATCC 33591) and Gram-negative bacteria Pseudomonas aeruginosa (ATCC 27853).
Neste trabalho, micropartículas de óxido de zinco (ZnO) com morfologia de estrela foram preparadas à temperatura ambiente por um método novo e simples e decoradas com nanopartículas de ouro (AuNPs) e prata (AgNPs). A presença de tioureia durante a precipitação do ZnO em meio alcalino permitiu o controle do tamanho e forma e a funcionalização da superfície com íons tiocianato (SCN-). Uma série de imagens de MET da amostra preparada em pH 12 sugere que as partículas crescem de acordo com o mecanismo conhecido como “coalescência orientada”. O espectro de emissão destas partículas mostrou uma característica interessante: a posição da banda de emissão pode ser ajustável alterando o comprimento de onda de excitação. AuNPs e AgNPs foram sintetizadas in situ na superfície do ZnO pelo método da fotorredução, sendo que a simples mudança nas proporções ZnO/AgNO3 ou ZnO/HAuCl4 é capaz de controlar os diâmetros médios das partículas. A presença dos íons SCN- na superfície do semicondutor impede o crescimento incontrolável de nanopartículas de Ag em diferentes morfologias e elevados graus de polidispersidade. DRX, MEV, MET, FTIR, UV-vis-NIR e PL foram utilizados para a caracterização da estrutura, morfologia e as propriedades ópticas de nanoestruturas puras e híbridos. Finalmente, as nanoestruturas híbridas ZnO/Ag apresentaram performance superior para aplicações em fotocatálise e atividade bactericida quando comparadas com o ZnO puro. Neste trabalho, foi estudada a fotodegradação de uma solução aquosa de azul de metileno sob irradiação UVA e a atividade bactericida foi testada para 4 estirpes bacterianas, incluindo as bactérias Gram-positivas Staphylococcus aureus (ATCC 43300, ATCC 25923 e ATCC 33591) e Gram-negativas Pseudomonas aeruginosa (ATCC 27853).

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Rosset, Aurelie. "Synthèse et caractérisation de nanoparticules catalytiques pour une application en photocatalyse solaire." Thesis, Perpignan, 2017. http://www.theses.fr/2017PERP0014/document.

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Cette thèse s’inscrit dans le développement et l’optimisation d’un panel de catalyseurs dopés ou non dopés pour le traitement des eaux usées par un Procédé d’Oxydation Avancée (POA), la photocatalyse hétérogène solaire. Ce procédé de traitement tertiaire pour la dépollution de molécules organiques biorécalcitrantes est limité par l’absorption des catalyseurs dans le domaine de l’UV ne représentant que 5 % du spectre solaire reçu à la surface de la Terre. L’objectif de ce travail est de comparer les efficacités photocatalytiques sous rayonnement UV, visible et solaire dans le but d’améliorer les efficacités dans le domaine de l’UV, de développer un catalyseur exploitant efficacement le rayonnement visible et de définir les paramètres clés régissant les réponses photocatalytiques. Dans cette optique, une étude a été menée sur les catalyseurs de ZnO dopés ou non dopés. L’ensemble des catalyseurs à base de ZnO ont été synthétisé par un seul et même procédé, le sol-gel couplé à un séchage en conditions supercritiques. Les caractérisations structurales, morphologiques, chimiques, optiques et optoélectroniques ont été réalisées en vue de définir leurs paramètres physico-chimiques pour maitriser les conditions de synthèses des catalyseurs. Elles ont également montré que le ZnO dopé décale sa bande d’absorption vers le domaine du visible. Les expérimentations photocatalytiques ont été conduites à l’aide d’un banc de mesure photocatalytique dans le domaine de l’UV, du visible et du solaire. Une attention particulière est portée sur un polluant modèle, le pyriméthanil. En parallèle, ces expérimentations ont été couplées à un modèle cinétique. Les nanoparticules de Zn1-xMxO (M : Ca, Al, Li, V, In, Co, P…) présentent des réponses photocatalytiques prometteuses dans le domaine du visible. Une corrélation a également été mise en évidence entre les propriétés physico-chimiques des catalyseurs et l’efficacité à produire des radicaux. Par ailleurs, une étude plus approfondie a été menée sur le Zn0,90Ca0,10O. Cette étude révèle la présence de défauts structuraux jouant un rôle essentiel sur les réponses photocatalytiques
This thesis is part of the development and optimization of a doped and undoped panel of catalysts for the treatment of waste water based on an Advanced Oxidation Process (AOP), solar heterogeneous photocatalysis. This tertiary process for bio-recalcitrant organic molecules clean up is limited by the catalysts absorption in the UV range which represent only 5 % of the solar spectrum received on the earth surface. The aim is to compare photocatalytic efficiency under UV, visible and solar irradiation in order to improve efficiency in the UV range, to develop a catalyst which operates effectively under visible irradiation and to define key parameters governing the photocatalytic activities. In this context, a study is performed on doped or undoped ZnO based catalysts. All of ZnO based catalysts are synthesized by the same process, the sol-gel process under supercritical drying conditions. Structural, morphological, chemical, optical and optoelectronical characterizations is carried out to define their physico-chemical parameters in order to control the synthesis conditions of these catalysts. Doped ZnO also showed an absorption edge shift toward the visible range. Photocatalytic experiments are carried out with a photocatalysis optical bench in the UV, visible and solar range. Particular attention is paid on a model pollutant, pyrimethanil. In parallel, these experiments are coupled to a kinetic model. Nanoparticles of Zn1-xMxO (M : Ca, Al, Li, V, In, Co, P…) showed encouraging photocatalytic activities in the visible range. A correlation is showed between the physico-chemical properties of the catalysts and the radicals production efficiency. Furthermore, an extensive study is done on Zn0,90Ca0,10O. This study reveals the presence of structural defects playing a main role on the photocatalytic activities

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Ali, Arshid Mahmood. "Characterisation of semi-conductor zinc oxide (ZnO) thin films as photocatalysts." Thesis, University of Auckland, 2011. http://hdl.handle.net/2292/7203.

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The objective of this project was to study the suitability of nanostructured ZnO thin films as efficient photocatalysts and to characterise any issues that may be involved in the scale-up of photocatalytic systems based on these types of immobilised nanostructure ZnO thin films. In particular, this study involved fabricating and then evaluating the effectiveness of a range of nanostructured zinc oxide (ZnO) thin films with different structures and chemistries (i.e. undoped and doped) as photocatalysts, and thereafter to systematically relate: the initial and reacted surface morphology; photocatalytic activity in terms of reaction rate; reaction intermediates and products; and liquid phase and solid phase reaction mechanisms under both limited and rich oxygen conditions at two different UV irradiation wavelengths (254nm and 340nm). These nanostructured thin films (i.e. undoped ZnO; nitrogen doped ZnO - N:ZnO; cobalt doped ZnO - Co:ZnO) were produced using an innovative combination of magnetron sputtered surfaces and hydrothermal solution deposition that allows the morphology, porosity and thickness to be controlled by varying the composition and processing conditions. SEM, UV-Vis, HPLC, LC-MS, AAS and XRD were used to study the changes in thin film morphology, Methylene Blue (MB) degradation and its reaction intermediates, the presence of Zn metal in the reaction fluid, if any, and crystallinity before and after the photocatalytic reaction respectively. Undoped ZnO thin films: Results showed a clear relationship between surface morphology (and the related thin film preparation method) and photocatalytic activity for the ZnO thin film supported catalysts: the tallest, most aligned structure had the highest photocatalytic activity, whilst the smallest, least aligned structure had the lowest. Thus, the MB degradation rate was the fastest for the ZnO thin film (S2-MS) with a uniform arrayed structure. Adding oxygen made the films more stable: in oxygen-limited conditions, SEM and atomic absorption spectroscopy indicated zinc leaching had occurred. Furthermore, with additional oxygen the zinc leaching was minimised under the same reaction conditions. It is thought that this additional oxygen is either minimising the release of, or replacing lost ZnO lattice oxygens, indicating that this ZnO photocatalytic oxidation could be occurring via a Mars van Krevelen type redox mechanism. There was also a significant difference in MB degradation rates, as well as reaction intermediate formation and destruction rates, correlated to the morphologies and crystallinity at both UV wavelengths, with the highest reaction rates at 340nm. Reaction analysis indicates that there is a competition between two different photocatalytic mechanisms: conventional photocatalysed radical oxidation and lattice oxygen-driven oxidation. The dominant reaction mechanism depends on the thin film morphology, crystallinity, availability of oxidant and the wavelength of the incident UV. The surface-photocatalysed radical formation was predominant for more aligned, highly crystalline, morphologies, where there was plentiful oxygen and UV irradiation at 340nm. Lattice oxygen photodegradation was predominant for the less aligned, more amorphous morphologies and UV irradiation at 254nm. Doped (Co:ZnO) thin films: Results showed that cobalt dopant increases the photo-stability of the corresponding undoped thin films under oxygen-limited conditions - increasing with the increased dopant concentration. This increased stability of Co:ZnO nanostructure thin films comes with a price, however: the photocatalytic activity and concomitant degradation of MB and its azo dyes reaction intermediates is in general lowered, compared to the undoped ZnO thin films. At higher dopant concentrations, under oxygen-rich conditions and with UV irradiation at 254nm and 340nm, the MB degradation most likely occurs via a conventional photocatalytic reaction mechanism and/or via charge transfer of the MB into Azure B (AB) with the absence of Mars van Krevelen type mechanism (because of the increased lattice stability). At lower dopant concentrations under oxygen-limited conditions with UV irradiation at 254nm and 340nm, the Mars van Krevelen type reaction mechanism is probably the main mechanism propagating the oxidation of MB. Overall, the undoped morphologies were more photocatalytically active compared to the doped morphologies. In general, this work has shown that several different solid and liquid phase photocatalytic reaction mechanisms govern the photocatalytic degradation of azo dyes such as MB on nanostructured ZnO thin films, and that surface morphology, crystallinity, lack or presence of oxygen, and the dopant concentration are the key parameters governing the overall photocatalytic activity and the activation of these different solid and liquid photocatalytic reaction mechanisms.

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Migas, Jeremiah. "A PHOTOCATALYTIC INVESTIGATION OF CORE-SHELL AND HIERARCHICAL Zn-Ti-O/ZnO HETEROSTRUCTURES PRODUCED BY HYBRID HYDROTHERMAL GROWTH AND SPUTTERING TECHNIQUES." OpenSIUC, 2012. https://opensiuc.lib.siu.edu/theses/824.

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With an increasing demand for alternative clean energy solutions, much effort is being invested in the progression of nanoscale semiconductor materials in hopes of better harnessing solar energy. ZnO and TiO2 remain the most prominent photocatalytically active materials. This thesis reports on a comparison between nanoscale core-shell and hierarchical Zn-Ti-O/ZnO heterostructures. After a seed layer thickness optimization, hydrothermally grown ZnO nanorods were coated with mixed concentrations of Ti and Zn within an oxygen rich sputtering environment at two distinct temperature zones. Core-shell structures resulted from low temperature (23°C) depositions while hierarchical branch structures grew at high temperature (800°C). Excluding deposition temperature and the strategic variation of Zn and Ti gun power, every fabrication process remained identical between the two resultant heterostructure groups. Amongst the variety of samples produced, one from each heterostructure group proved notably similar in structural dimension, composition, and crystallization, yet demonstrated distinct differences in photoluminescence and dye degradation via UV-visible light spectroscopy. While photoluminescence results indicated core-shell heterostructure more photocatalytically promising, hierarchical heterostructure prevailed as the more powerful photocatalyst. Increased surface area due to hierarchical branching in conjunction with enhanced light exposure was believed responsible for the improved photocatalytic effectiveness.

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Meier, Anne J. "Photocatalytic Carbon Dioxide Conversion to Fuel for Earth and Mars." Scholar Commons, 2018. https://scholarcommons.usf.edu/etd/7696.

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As far as we know, we only have one planet to live on, with a delicate atmospheric system providing us safety and life. Global CO2 emissions continue to plague the environment of Earth, primarily due to the processing of fossil fuels, deforestation, and industrialization. There are several avenues of pursuing CO2 reutilization, each having their own benefits and limitations. Direct and indirect thermochemical approaches of CO2 conversion boast of efficient CO2 conversion rates but have limitations associated with the use of renewable hydrogen and high temperatures of operation. The work in this dissertation investigates low temperature photocatalytic CO2 conversion, a simple principle, which provides opportunity for fuel production while harvesting solar energy. Large scale implementation of this process has been plagued by limitations such as fast electron/hole recombination rates, poor quantum efficiency, product selectivity, catalyst stability, and the band gap energy (Eg) being too large to harvest solar light. Our long term goals and applications look to utilize sustainable fuel generation in-situ on Mars for human exploration. We must use available Mars resources to generate fuel to save launch and resource costs from Earth, utilizing the Sun, Mars atmospheric CO2 (95%), and H2O that can be harvested from subsurface ice. Visible light activated catalysts are needed for applications of CO2 conversion on Earth and Mars due to the intensity and abundance of visible light available in the solar spectrums. The dissertation presents the development of photocatalysts for CO2 reduction in the presence of H2O under visible light irradiation. Detailed chemical analysis and characterization were performed on the photocatalysts for improved understanding of material design, including optical and elemental properties, charge transport, stability, catalytic function and scalability. Induced defects and impurities were implemented to understand Eg tunability. Introducing defects through impurities reduced the electron confinement effects in some cases, increasing the photocatalytic activity. Three material regimes were synthesized, tuned, and tested for catalytic function. The first was a series of (ZnO)1-x(AlN)x, materials that had not been synthesized previously, nor ever demonstrated in CO2 and H2O under solar irradiation. The Zn:Al materials were derived from layered double hydroxides. The second material set was (ZnO)1-x(GaN)x, also derived from layered double hydroxides. To the best of our knowledge, these Zn:Ga materials were demonstrated for the first time in CO2 reduction to CO under visible light without the use of any noble metal co-catalysts or dopants. The third set of materials were MoS2 nanoflowers synthesized via chemical vapor deposition that, to our pleasant surprise, produced thinly stacked sheets in the form of nanoflowers that contained large edge-site exposure, which was vastly different from the morphology of commercially purchased MoS2. The preliminary results from this work have demonstrated that tunable band gap energy is achievable. The (ZnO)1-x(AlN)x Eg ranged from 2.84 to 3.25 eV. The Zn:Al solid solution materials were tuned by increasing nitridation time, and varying the cationic ratio. Increasing the cationic ratio in this study more than tripled CO production under solar light irradiation compared to lower cationic ratios. The (ZnO)1-x(GaN)x, materials had a Eg range from 2.33 eV to 2.59 eV. The Eg was also easily tunable from varying nitriding time and cationic ratio. The highest CO production rate was the Zn:Ga cationic ratio of 3:1 at 20 min of nitriding time at 100 °C, which produced 1.06 µmol-g-1-h-1. This production was higher than both of our controlled TiO2 experiments, and other reported pure TiO2 solar photoreaction experiments. The results indicate a delicate balance of nitridation and Zn:M3+ ratio should be selected, along with precursor material cation ratios in order to obtain the desired final product and crystal structure. The controlled introduction of imperfections or crystal defects through MoS2 synthesis variations also revealed the tuning ability of flake edge morphology, nanoflower diameter, stacked-sheet thickness, optical Eg and catalytic activity. The nanoflower Eg ranged from 1.38 to 1.83 eV, and the production rates of CO nearly doubled when post treating the nanoflowers in a reduction step. These developments support tunable gas phase photocatalytic activity and can be enhanced further for further photocatalytic reactions, optoelectronics and field emitter applications. The photoreactor studies indicated that careful tuning of the parent material is imperative to understand before adding a co-catalyst or doping process, as the edge site morphology, crystal phase stability, and strain-induced defects impact the photocatalytic performance.

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32

Naszályi, Nagy Lívia. "Preparation and characterization of functional nanostructured thin layers composed of silica, ZnO and core/shell silica/ZnO particles." Montpellier 2, 2008. http://www.theses.fr/2008MON20050.

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SANUSI, IBRAHIM J. "Synthesis, Characterization, and Analysis of TiO2/ZnO Composites Thin Films Photocatalysts for Ethanol Vapor Oxidation." Miami University / OhioLINK, 2021. http://rave.ohiolink.edu/etdc/view?acc_num=miami1626637854831713.

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34

Han, Zhitao. "Intégration de nanofils de ZnO dans des dispositifs microfluidiques pour lesétudes photocatalytiques et photovoltaïques." Paris 6, 2013. http://www.theses.fr/2013PA066424.

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This thesis work aimed at integration of ZnO nanowires into microfluidic devices for photocatalytic and photovoltaic studies. Firstly, the hydrothermal growth method has been improved by preparing high-quality ZnO seed layer based on a sol-gel process and a spin-coating technique. Then, the ZnO seed layer could be patterned by standard lithography methods and well-aligned ZnO nanowire arrays could be grown in patterned areas without fusion at the foot of nanowires. Secondly, large-area ZnO nanowires have been integrated into microfluidic reactors as immobilized catalyst, allowing stable and high-efficient photocatalysis. Thirdly, the integrated ZnO nanowires could also be used for dye-sensitized solar cell (DSSC) studies, showing clear dependence on ZnO nanowire growth conditions but less effect on the flow-rate of microfluidic electrolyte. Finally, as a subset of ZnO nanowires with ultrahigh aspect ratio, ZnO nanofibers doped with noble metal palladium (Pd) have been synthesized via electrospinning technique and subsequent thermal treatment. The enhancement effect of Pd doping on the photocatalytic activity of ZnO nanofibers has been demonstrated by photodegradation of organic dye methylene blue
Ce travail de thèse vise à intégrer des nanofils de ZnO dans des dispositifs microfluidiques pour les études photocatalytiques et photovoltaïques. Tout d'abord, la méthode de croissance hydrothermale a été améliorée par dépôt direct d’une couche germe de ZnO de haute qualitéun en utilisant un procédé sol-gel et une technique de revêtement par centrifugation. Ensuite, cette couche de ZnO semencée a été lithographiée pour définir des zones de croissance. Comme résultats, les matrices de nanofils de ZnO bien alignées ont été obtenues sans fusion au pied des nanofils. Deuxièmement, des nanofils de ZnO à grande surface ont été intégrés dans les réacteurs microfluidiques, permettant une photocatalyse stable et à haut rendement. Troisièmement, les nanofils de ZnO intégrés ont été utilisés pour des essais sur les cellulaires solaires à colorant (DSSC), montrant une dépendance claire sur les conditions de croissance de nanofils de ZnO, mais peu d’effet sur le débit d'électrolyte microfluidique. Enfin, la synthèse hydrothermale a été appliquée pour obtenir des nanofibres de ZnO par électrofilage avec ou sans dopage de palladium. En comparant aux nanofibres de ZnO purs, les nanofibres de ZnO dopées de Pb ont montré une efficacité de photodégradation du bleu de méthylène améliorée

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35

Hermes, Natanael Augusto. "Oxidação fotocatalítica do glicerol sobre catalisadores de ZnO." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2014. http://hdl.handle.net/10183/109159.

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A oxidação fotocatalítica do glicerol (OFG) é uma possível alternativa para aproveitamento do excedente de glicerol proveniente do processo de produção do biodiesel, porém são poucos os registros desta reação na literatura. Neste trabalho, primeiramente foram testadas amostras comerciais de ZnO e TiO2, com o objetivo de identificar e quantificar os principais produtos de oxidação para cada semicondutor. Também foram realizados testes para determinação da influência dos parâmetros reacionais sobre a conversão e seletividade para gliceraldeído (GAD) e dihidroxiacetona (DHA), variando-se as condições experimentais tanto isoladamente quanto simultaneamente, através planejamento de experimentos. Por fim, foram sintetizadas amostras de ZnO visando-se obter uma amostra com melhores resultados em termos de conversão e seletividade para GAD e DHA que a amostra comercial. Os testes fotocatalíticos foram conduzidos em reator batelada (slurry) sob radiação ultravioleta, usando soluções aquosas de glicerol. Os produtos de oxidação foram analisados por cromatografia líquida de alta eficiência (CLAE). Os catalisadores sintetizados foram caracterizados por MEV, área BET, DRX, espalhamento de raios X a baixo ângulo e medidas de Potencial Zeta. Os resultados mostraram que ZnO e TiO2 diferem significativamente quanto à seletividade. O ZnO apresentou maior seletividade para produtos de maior valor agregado, como o gliceraldeído (GAD) e a dihidroxiacetona (DHA), indicando maior contribuição da fotocatálise indireta. O TiO2 apresentou seletividade maior para produtos resultantes da quebra da molécula de glicerol, como o formaldeído e o glicolaldeído, o que indica maior contribuição da fotocatálise direta. Nos testes da influência dos parâmetros reacionais para o ZnO, determinou-se que a conversão é afetada principalmente pelo pH inicial e concentração de catalisador e que a seletividade é afetada principalmente pela temperatura de reação e pH inicial. Em relação às amostras de ZnO sintetizadas em laboratório, nenhuma foi mais fotoativa que a amostra comercial, porém a amostra ZnO-B foi a mais fotoativa dentre as sintetizadas e foi mais seletiva ao GAD do que o ZnO comercial. Pôde-se determinar que o potencial zeta foi a característica mais influente na fotoatividade destes catalisadores, sendo que quanto mais positivo este valor, mais fotoativo o catalisador. Finalmente, em relação às amostras de ZnO com diferentes proporções de planos polares, a amostra com baixa proporção foi cerca de 2 vezes mais fotoativa que a amostra com alta proporção destes planos, o que se opõe aos resultados encontrados na literatura sobre fotoatividade relacionada a planos cristalinos.
The photocatalytic oxidation of glycerol emerges as a potential alternative to contribute to the utilization of glycerol surplus from biodiesel production. However, there are few reports about this reaction in the literature. In this work, as a first approach, commercial samples of ZnO and TiO2 were tested in order to identify the main products for each semiconductor. Next, the influence of the reaction parameters on the conversion and selectivity to glyceraldehyde (GAD) and dihydroxyacetone (DHA) was studied through a design of experiments, using ZnO as catalyst. Finally, additional ZnO samples were synthesized as an attempt to obtain a catalyst with conversion and/or selectivity higher than the commercial sample. The photocatalytic tests were carried out in a batch reactor (slurry) under ultraviolet radiation, using aqueous solution of glycerol. The oxidation products were analysed by liquid chromatography (HPLC). The synthesized catalysts were characterized by SEM, BET surface area, XRD, SAXS and Zeta Potential measurements. The results showed that ZnO and TiO2 differ significantly in selectivity. ZnO was more selective to products with higher commercial value (GAD and DHA), indicating greater contribution from indirect photocatalysis. On the other hand, TiO2 showed higher selectivity to products from the cleavage of the glycerol molecule, such as formaldehyde and glycolaldehyde, which indicates greater contribution from direct photocatalysis. In reference to the tests about the influence of the reaction conditions using ZnO, it was found that conversion was affected mainly by the initial pH and catalyst concentration, whereas selectivity was affected mainly by the temperature and initial pH. Regarding the synthesized ZnO catalysts, none of them reached conversion higher than the commercial sample, yet the sample ZnO-B showed the highest selectivity to GAD, even higher than the commercial sample. It was also determined that the zeta potential was the most influential characteristic on the catalyst activity. Finally, regarding the ZnO catalysts with different proportions of polar planes, the sample with low proportion of polar planes was about 2 times more active than the sample with high proportion of polar planes, which contradicts the records found in the literature about this specific topic.

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36

Топоровська, Л. Р., А. М. Грицак, and Б. І. Турко. "Вплив іонного травлення на фотокаталітичні властивості мікроструктур ZnO." Thesis, Сумський державний університет, 2017. http://essuir.sumdu.edu.ua/handle/123456789/63784.

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За аналогією до роботи, у котрій досліджували фотокаталітичні властивості порошку ZnO, для підвищення фотокаталітичної активності мікроструктур ZnO з різною морфологією поверхні (гранулоподібні, мікроголки та мікрооктаподи), синтезованих на кремнієвих підкладках, використано метод короткочасного (1,5 хв) іонного травлення. Тестування фотокаталітичних властивостей вихідних та оброблених іонним травленням матеріалів виконано з використанням модельної реакції фотокаталітичної деградації водного розчину барвника - метилоранжу.

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37

Chauviré, Timothée. "Développement de systèmes photochimiques à base de Quantum Dots hydrosolubles de type coeur CdSe et coeur-coquille CdSe/ZnS." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENV039/document.

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L'utilisation de nanoparticules semi-conductrices colloïdales, appelées quantum dots, est nouvelle pour des applications en photocatalyse redox. Ces nano-objets possèdent une forte absorption dans le visible modulable avec leur taille. De plus, la présence d'une couche de ligands peut rendre ces nanostructures éco-compatibles. Dans ce manuscrit de thèse, une étude de la photocatalyse redox avec des nanoparticules cœur CdSe et cœur-coquille CdSe/ZnS a été réalisée dans le visible en solvant aqueux. Les quantum-dots hydrosolubles sont tout d'abord fonctionnalisés par des ligands de type acide aminé. Trois systèmes photochimiques ont ensuite été testés avec les substrats suivants : dérivés d'acides aminés, vanilline et 8oxodG. L'activité photochimique des nanoparticules semi-conductrices a pu être démontrée et évaluée par la détection de produits de réaction. Le mécanisme de transfert de charge photoinduit a par ailleurs été élucidé par des techniques spectroscopiques durant l'irradiation
The use of colloidal semiconductor nanoparticles, called quantum dots, is recent in redox photocatalysis. Those nanostructures exhibit strong and size depending visible absorption properties. The ligand shell on the nanoparticle surface can be furthermore managed to realize green applications. Thus the study of redox photocatalysis with core CdSe nanoparticles and core-shell CdSe/ZnS was carried out with visible light in aqueous solvent. Firstly, we synthetized hydrophilic quantum-dots stabilized by amino acids ligands. Secondly, we perform three different studies of photocatalytic systems with the following substrates : modified amino acids, vanillin and 8oxodG. The nanoparticle's photochemical activity was first demonstrated and evaluated by the detection of photochemical products. The photoinduced charge transfer mechanism was elucidated during irradiation by spectroscopic techniques

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Lai, Hung-Chun. "Photocatalytic water splitting by utilising oxide semiconductor materials." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:96aa9405-133e-4e27-9bb1-cf49e05aba4e.

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This thesis reports the study of metal oxide semiconductors for the application of photoelectrochemical water splitting with a particular emphasis on both anion and cation-doped zinc oxides. A study of the mechanisms of visible light absorption in both anion and cation-doped ZnO semiconductors, the potentials of metal oxide materials modified by impurities as one of the ideal photocatalysts in harvesting solar light has been explored. X-ray photoelectron spectroscopy (XPS) and UV-Vis spectroscopes have been performed to establish the electronic structures of anion and cation-doped ZnO. Aluminium impurities in ZnO thin films reveal the relationship between the bandgap broadening and the so-called Burstein Moss effect. Both cadmium and sulphur dopants were incorporated in ZnO either as powders by the solid state synthesis or as thin films by spray pyrolysis technique. Cadmium and sulphur dopants demonstrate effective electronic bandgap reduction and an increasing absorption of visible light. Furthermore, the incorporation of cadmium and sulphur in ZnO were prepared as photoanodes and evaluated in a custom-built photoelectrochemical workstation for the measurement of photon energy conversion efficiencies.

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39

Chang, Jan Hau, and 張展豪. "Application of ZnO Nanowires in Photocatalysis." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/87821589117472917129.

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博士
國立清華大學
材料科學工程學系
102
This thesis aims to investigate approaches to enhance the photocatalytic activity of substrate-supported ZnO nanowires (NWs). The employed NWs are grown on various substrates by thermal evaporation and have similar surface area. The NW photocatalytic activity is evaluated by degrading 50 uM rhodamine B with the use of UV light. These results in the first part of thesis reveal that the photocatalytic activity can be enhanced by using a conductive substrate and NWs with less defects. In the second part of thesis, the degradation kinetics has also been analyzed and indicates a combined zeroth-order and first-order reaction with a threshold concentration of 10 uM. The degradation constants of as-grown ZnO NWs are 0.58 uMmin-1 (zeroth-order) and 0.028 min-1 (first-order) and outperform reported values obtained from similar NWs. In the third part of thesis is for an investigation of the photocatalytic activity of substrate-supported ZnO nanowires with Ag modification and induced bending. By degrading a 50 uM rhodamine B solution, it is found that the zeroth-order kinetic constant of Ag modified bent NWs is 1.4 and 2.2 times as high as that of Ag modified unbent NWs and unmodified as-grown NWs, respectively. The improvement due to bending is related to the piezoelectric property of ZnO that facilitates charge separation. This work demonstrates the usefulness of piezoelectricity for photocatalysis. In the last part of the thesis, the photocatalytic activity of hydrogenated ZnO NWs is studied. Also, by degrading a 50 uM rhodamine B solution, it is found that the zeroth-order constant of hydrogenated ZnO NWs is around 2.5 times as high as that of as-grown ZnO NWs and the advantage of a low density of oxygen vacancies in ZnO NWs is apparent. Consequently, hydrogenated ZnO NWs enhance the photocatalytic activity significantly.

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40

Gu, Wen-Jing, and 古玟靜. "Synthesis of C3N4-WO3/ZnO Photocatalysis By Using Sol-Gel method For Photocatalytic degradation." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/58659887228917644102.

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碩士
國立中興大學
化學工程學系所
103
In this experiment, ZnO photocatalyst were prepared by a sol-gel method, using [zinc nitrate hexahydrate,(Zn(NO3)2‧6H2O)] as starting material. and try to add C3N4 and WO3 were modified photocatalyst, The compound semiconductor Photocatalyst can be prepared via the procedures of mixing, hydrolysis and condensation reaction. Experiment focuses on the photocatalytic activity with different calcination temperature, calcination time and compound semiconductor photocatalyst modified, and by photocatalytic experiment of methyl orange, further confirmed photocatalyst prepared under different experimental conditions on the degradation of methyl orange the effect of the impact. Experiment samples were analyzed with SEM, XRD, BET. The results found that the addition of 3% C3N4 and 3% WO3 in ZnO calcined to 500℃ four hours compound semiconductor photocatalyst in all aspects of performance are all the best, its photocatalytic experiment of methyl orange, the degradation efficiency to 82%, the first-order reaction rate constant for 3.148x10-2 min-1.

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41

張永祥. "Application of ZnO Nanowires with Copper Oxide Modification in Photocatalysis." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/49158013657311892544.

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42

Chen, Chien Hua, and 陳建華. "Application of ZnO Nanowires Modified with Silver Nanoparticles in Photocatalysis." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/86420945872697452814.

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碩士
國立清華大學
材料科學工程學系
104
ZnO is a suitable photocatalytic material from non-toxic, biocompatibility, low-cost, and strong photo-induced electron-hole pairs. However, ZnO has the limitation of absorbing visible light and fast recombination rate of electron-hole pairs. In this work, ZnO nanowires were modified with Ag nanoparticles. Owing to the improvement of the Ag/ZnO absorption ability, the photocatalytic performance could be enhanced. Moreover, the superior photocatalytic performance of the Ag/ZnO can be ascribed to the heterostructure which lowers the recombination rate of photo-excited electron-hole pairs. Compared to the traditional Si substrate, we took paper as substrates and grow ZnO nanowires by low-cost solution method to lower the price and applied in the industry. The scanning electron microscopy indicates the morphologies and structures of nanowires and nanoparticles, the ZnO nanowires modified with the best concentration of Ag nanoparticles showed the best photocatalytic performance under the condition of 2-min photoreduction with 5×10^(-2) M silver nitrate. The Ag nanoparticles formed nanoclusters or thin film on the top of ZnO nanowires, which lowers the photocatalytic performance, under the condition of 2.5-min photoreduction with 5×10^(-2) M silver nitrate or after 6-min photoreduction with 1×10^(-3) M silver nitrate. The energy dispersive spectrometer presents that there are no impurities inside the material. The photoluminescence spectra show that the decreasing of Ag/ZnO, especially the Ag/ZnO photoreduced with 5×10^(-2) M silver nitrate, compares to the as-grown ZnO, revealing that the recombination of electron-hole pairs is more likely reduced by high concentration and uniform distribution of Ag nanoparticles. The photocatalytic performance of the ZnO or Ag/ZnO nanowires on paper substrate with 1.5 cm by 1.5 cm surface area was evaluated by degrading a 10 µM rhodamine B solution under the illumination of ultraviolet light. The best first-order kinetic constant of the Ag/ZnO nanowires is 0.218 min^(-1). It is 1.93 times as high as as-grow ZnO nanowires (0.0113 min^(-1)). It showed a high-efficiency photocatalytic material by a simple photoreduction method successfully. The ZnO nanowires on paper substrate also showed a good response of the gas sensor, which has been utilized to sense 1 ppm NO gas under UV light and background ambient gas and showing response up to 89%. However, the ZnO nanowires modified with Ag nanoparticles were not able to be a good gas sensor device. Because the paper sucked up silver nitrate under the photoreduction, the Ag formed a continuous thin film on the paper. This Ag thin film lowers the resistance of the gas sensor material dramatically and diverts the electric current from the proper response region.

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43

Hsu, Peng-Yueh, and 徐鵬岳. "Phorate degradation by TiO2 and ZnO photocatalysis: parameter and reaction pathway investigations." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/q373m5.

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碩士
靜宜大學
應用化學研究所
97
The photocatalytic degradation of phorate in aqueous suspensions was examined with the use of titanium dioxide (TiO2) or zinc oxide (ZnO) as a photocatalyst. Under the UV irradiation, the best condition that photodegradation using TiO2 as catalyst about 99% of phorate was degraded for 60 min. When photodegration using ZnO as catalyst, About 99% of phorate was degraded for 90 min. The photodegradation of phorate followed pseudo-first-order kinetics and parameters such as pH of the system, TiO2 or ZnO dosage, and presence of anions were found to influence the reaction rate. To obtain a better understanding of the mechanistic details of this TiO2-assisted photodegradation of phorate with UV irradiation, the intermediates of the processes were separated, identified, and characterized by the solid-phase microextraction (SPME) and gas chromatography/mass spectrometry (GC/MS) techniques. The probable photodegradation pathways were proposed and discussed. To the best of our knowledge, this is the first time that reports the degradation pathways of phorate. We also use Ion chromatograph measured the ionic by-products produced (PO43- and SO42-) during photocatalysis, the increase of sulfate and phosphate concentrations was determined organic compounds can be mineralized. The electrical energy consumption per order of magnitude for photocatalytic degradation of phorate was also calculated and showed that a moderated efficiency (EEO = 96 kWh/(m3 order)) was obtained in TiO2/UV process.

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44

Chang, Cheng-Wei, and 張正偉. "Synthesis and characterization of ZnO nanowires/Ag microplates heterostructures and their enhanced photocatalysis performance." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/54012138217187266747.

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碩士
國立清華大學
材料科學工程學系
100
Ag/ZnO heterostructures are versatile materials capable of transferring interfacial charge transfer and suppressing electron-hole pairs recombination. Recently, great efforts have been made to prepare Ag/ZnO heterostructures with various morphologies such as clusters (particles-to-particles) and dendrites (wires-to-wires). We herein report a novel heterostructure of ZnO nanowire arrays growing on single crystalline polygonal Ag microplates which provides the merits of the antireflection layer for ZnO nanowire arrays and the 2D electrons transportation layer for Ag microplates. The Ag/ZnO heterostructure was fabricated by utilizing the rivalrous polyol reduction method and aqueous solution method. The experimental results showed that the edge length of single crystalline Ag microplates can reach up to 5 μm, and the Ag microplates are highly oriented with {111} facets as the basal planes. Arrays of single crystalline ZnO NWs were vertically assembled along <0001> direction attaching on the {111} facets of Ag microplates. It was confirmed by scanning electron microscope (SEM), transmittance electron microscope (TEM) and X–ray photoemission spectrum (XPS), revealing the direct contact and the charge transfer between Ag microplates and ZnO nanowires. Meanwhile, contacts of Ag/ZnO heterostructure form the charge separation, so enhance the photocatalytic activity by using the representative target pollutant–Methyl blue (MB). It shows the positive results of the heterostructure enhance the activities of MB photodegradation at the pseudo first order kinetic constant of 6.60×10-3 min-1 by means of employing micrograms of photocatalysts.

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45

Chiang, Mao Yuan, and 江茂源. "Application of ZnO Nanowires Co-modified with Cuprous Oxide and Silver Nanoparticles in Photocatalysis." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/84032626095424338896.

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碩士
國立清華大學
材料科學工程學系
103
In this work, we report on the enhanced photocatalytic activity of ZnO nanowires (NWs) modified with cuprous oxide and silver nanoparticles (NPs). ZnO NWs were first grown on fluorine-doped tin oxide substrates by thermal evaporation without catalysts. They were then modified with cuprous oxide or silver NPs, or both, by photoreduction. The NP modified NWs show better photocatalytic performance than as-grown NWs. Furthermore, ZnO NWs co-modified with cuprous oxide and silver NPs have the best photocatalytic efficiency. From the scanning electron microscopy and transmission electron microscopy images, the morphologies and the structures of the NPs are confirmed. The ultraviolet emissions of modified ZnO NWs decrease in the photoluminescence spectra, revealing that the recombination of electron-hole pairs is reduced. The absorption spectra show that modified ZnO NWs have higher absorption in both visible and ultraviolet regions, which is due to the narrow band gap of cuprous oxide NPs and the plasmonic effect of silver NPs. The photocatalytic activities of the NWs were evaluated by degrading a 50 µM rhodamine B solution under the illumination of a 100 W halogen lamp. The zeroth-order kinetic constant of the co-modified ZnO NWs is 0.32 µM/min, which is 3.2 times as high as that of as-grown ZnO NWs. The co-modified NW sample has also been tested under direct sunlight illumination. A kinetic constant of 0.73 µM/min and a degradation efficiency of 95% in 80 min have been obtained.

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Cheng, Hao-Ching, and 鄭皓璟. "Synthesis and characterizations of low-dimensional ZnO/WS2 nanocomposites for efficient visible-light-response photocatalysis." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/8ku68j.

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碩士
國立中山大學
材料與光電科學學系研究所
107
Two-dimensional transition metal dichalcogenides (2D TMDs) have attracted much attention in the field of visible-light responsive photocatalysis due to their superior properties. In this work, we develop the synthesis of 2D WS2 nanosheets decorated with ZnO nanoparticles by using a facile two-step method consisting of liquid phase exfoliation technique followed by in-situ chemical solution method to prepare 0D/2D ZnO/WS2 nanocomposites. The as-prepared nanocomposites were characterized via X-ray diffraction, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, Raman spectroscopy, X-ray photoelectron spectroscopy, absorption spectrometer and photoluminescence. The photocatalytic performance of the prepared nanocomposits were examined by studying the degradation of methylene blue (MB) dye under visible-light irradiation. We found that within 25 min 85% of MB dye was photodegrated by the optimized hybrid nanomaterial. The reaction rate of pollutant degradation is about 4 times and 9 times higher than those of pristine WS2 nanosheets and P25 photocatalysts, respectively. The enhanced photocatalytic activity of the nanocomposite photocatalysts can be attributed to a few advantageous features from the synergetic effects. Most importantly, the ZnO/WS2 heterojunction facilitates the separation of photogenerated carriers, leading to the enhancement of photocatalytic efficiency. Furthermore, the possible photocatalytic mechanism has been tested and discussed in detail on the basis of scavenger experiments. Altogether, the present work provides feasible way for the facile fabrication of nanoscale 0D/2D TMD heterostructure with great potential for photocatalytic applications.

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Sio-LeLin and 林修樂. "Deposition of Ag Nanoparticles on ZnO Nanorod Arrays for Applications in Photocatalysis and Surface Enhanced Raman Scattering." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/89645979383729732543.

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碩士
國立成功大學
化學工程學系碩博士班
100
This thesis concerns the deposition of Ag nonoparticles on ZnO nanorod arrays and their applications in photocatalysis and surface enhanced Raman scattering (SERS). Firstly, ZnO nanorod arrays were synthesized by the sol-gel formation of ZnO nanoparticle seed layers and the followed hydrothermal method. After heat treatment in hydrogen or air, Ag nanoparticles were deposited on ZnO nanorod arrays by photo-reduction method. The size of Ag nanoparticles as well as the surface morphology, structure, composition, and optical property of ZnO nanorod arrays before and after the deposition of Ag nanoparticles were characterized by SEM, XRD, EDS, and UV/VIS/NIR spectrophotometer. As compared to the samples with heat treatment in air or without heat treatment, the ZnO nanorod arrays after heat treatment in hydrogen allowed Ag nanoparticles to be deposited more uniformly, densely, and numerously. Also, they exhibited the higher efficiency for the visible light-driven photocatalytic degradation of R6G dyes (Rhodamine 6G) and the better SERS effect. For the photocatalytic degradation of R6G dyes, the effect of the amount of Ag nanoparticles, initial dye concentration, and temperature on the efficiency were also investigated. For the analytical application of SERS, the detection limit of R6G dyes could be lowered to below 10-9 M.

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Segundo, Iran Gomes da Rocha. "Avaliação das capacidades fotocatalítica, superhidrofóbica e autolimpante de misturas betuminosas funcionalizadas com TiO2 e ZnO." Master's thesis, 2018. http://hdl.handle.net/1822/71058.

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Dissertação de mestrado integrado em Engenharia Civil
Atualmente, existe uma preocupação crescente acerca do esgotamento dos recursos naturais e do dano ao meio ambiente. A engenharia rodoviária em geral e particularmente o domínio dos pavimentos rodoviários pode contribuir de forma significativa para a mitigação destes problemas. A integração de nano/micromateriais nas misturas asfálticas que constituem as camadas superficiais dos pavimentos dotará essas superfícies de novas capacidades (funcionalização) particularmente em termos ambientais e em termos de segurança viária: (i) fotocatalíticas: capazes de fotodegradarem poluentes com o intuito de limparem o meio ambiente; (ii) superhidrofóbicas: melhor resistência à água e uma maior segurança rodoviária em períodos de chuva e de baixas temperaturas; (iii) autolimpantes: evitar problemas de derrapagem, facilitar a drenabilidade da água e dificultar o fenômeno da colmatação dos poros. Com o objetivo de dotar as superfícies dos pavimentos com estas novas capacidades funcionais, misturas asfálticas do tipo AC 6 e AC 14 foram funcionalizadas a partir da aspersão superficial dos semicondutores nano-TiO2 e/ou micro-ZnO. Previamente, a fim de avaliar o impacto químico e morfológico da aplicação dos semicondutores, foram realizados ensaios de Microscopia de Força Atômica (AFM) e Espectroscopia de Infravermelho Transformada de Fourier (FTIR) nos ligantes asfálticos usados para compor as misturas. A seguir, para verificar as novas capacidades, foram realizados ensaios de Ângulo de Contato e de Avaliação Fotocatalítica. Por fim, a melhor solução foi avaliada mecanicamente pela resistência à tração após o condicionamento por água para avaliar o impacto dos semicondutores. Os resultados indicam que houve um maior impacto superficial e químico pela técnica de aspersão da solução aquosa contendo ZnO. A combinação de TiO2 com ZnO promoveu propriedades fotocatalíticas, superhidrofóbicas e auto-limpantes, proporcionando a ambas as misturas asfálticas essas novas capacidades. Ademais a aspersão não causou impacto mecânico. Com o desenvolvimento dessas camadas, prevêem-se grandes benefícios para o ambiente e para a segurança rodoviária.
Presently, there is a growing concern about the depletion of natural resources and environmental damage. The road engineering in general and road pavements can contribute significantly to mitigate these problems. The integration of micro/nanoparticles in asphalt mixtures that compose the top layer of the pavements will provide their surfaces with new capabilities (functionalization) particularly in environmental and safety related terms: (i) photocatalytic: able to photodegrade pollutants for the purpose of cleaning the environment; (ii) superhydrophobic: better water resistance and better road safety in periods of rains and low temperatures; (iii) self-cleaning: avoid slipping problems, facilitate the water drainability and prevent the pore clogging phenomenon. In order to provide the new functional capabilities to the surface of the pavements, asphalt mixtures AC 6 and AC 14 were functionalized with superficial spraying of semiconductors nano-TiO2 and/or micro-ZnO. First, in order to evaluate the chemical and morphological impacts of the application of the semiconductors, tests of Atomic Force Microscopy (AFM) and Fourier Transform Infrared Spectroscopy (FTIR) onto the asphalt binder that compose the mixtures were carried out. Next, in order to verify the new capabilities, tests of Water Contact Angle and Photocatalytic Evaluation were carried out. Finally, the best solution was mechanically evaluated through Indirect Tensile Strength after immersion to analyze the impact of semiconductors. The results show that there was a higher superficial and chemical impact onto the bitumen by the spray technique of the ZnO aqueous solution. The combination of TiO2 and ZnO promoted photocatalytic, superhydrophobic and self-cleaning properties, providing the asphalt mixtures these new capabilities. Besides the spraying technique did not cause mechanical impact. With the development of these layers, benefits to the environment and road safety are foreseen.

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Lin, Ruo-Chi, and 林若琪. "ZnO/Ni/C Magnetic Photocatalysts: Synthesis, Characterization and Photocatalytic Performance." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/07065570981689939462.

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碩士
淡江大學
化學工程與材料工程學系碩士班
103
ZnO/Ni/C magnetic photocatalytic particles were prepared using a hydrothermal technique. The aqueous solutions, having the molar ratios of Zn(CH3COO)2‧2H2O：Ni(NO3)2‧6H2O：C3H4OH(COOH)3 = 6：1：4 and the molar concentration of the total metallic ions (Zn2+ and Ni2+) = 0.1 M, were prepared. The pH of the solution was adjusted using 2 M NH4OH(aq). The solutions were then hydrothermally treated at 180 ℃ for 2 h. After centrifugally filtering and freeze-drying, the dried solid precursors were obtained and then thermally analyzed to investigate their thermal behavior, followed by calcining the solid precursors in N2 atmosphere at different temperatures. The calcined specimens were characterized using x-ray diffractometer (XRD), fourier transform infrared spectroscope (FTIR), scanning electron microscope (SEM) and photoluminescence spectroscope (PL). The photocatalytic performance of the prepared ZnO/Ni/C particles was evaluated by monitoring the ability to photocatalytically decompose the methylene blue in water under the irradiation of 365 nm UV light. Effects of pH values of the aqueous solution and calcination temperatures on the degree of crystallinity of ZnO and the weight ratio of ZnO to Ni in the ZnO/Ni/C magnetic photocatalytic particles were studied. The results indicated that the ZnO/Ni/C magnetic photocatalytic particles prepared by calcining the solid precursor obtained from the solution of pH = 4 (without NH4OH additions) in the nitrogen atmosphere at 600 ℃ possessed the best photocatalytic ability to decompose methylene, having a specific reaction rate, based on the mass of the photocatalyst used, 0.017 m3/(kg．s).

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Wang, Ci, and 王琦. "Photocatalytic Degradation of Binary Dye Solutions by Coupled ZnO/SnO2 Photocatalysts." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/12754014785727060755.

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碩士
長庚大學
化工與材料工程學系
99
This study evaluated the photocatalytic activity of ZnO/SnO2 coupled photocatalysts synthesized by a rotating packed bed (RPB) in degrading binary dye mixtures. Zn(OH)2/Sn(OH)4 was synthesized by ZnSO4 of 0.1 m, SnCl4 of 0.05 m and NaOH of 0.4 m in the RPB, with the rotating speed of 600 rpm and the liquid flow rate of 500 ml/min. Coupled ZnO/SnO2 photocatalysts were formed by calcining these precursors at 600 C for 10 hr. The optimal pH, ZnO/SnO2 dosage, dye concentration, and UV wavelength were investigated. The experimental results for degradation of single dye demonstrated that 98.7% decolorization and 24.5% mineralization of RhB were achieved at pH 6 and UV 254nm, with a ZnO/SnO2 dosage of 0.5 g/L and an initial RhB concentration of 5 ppm, as measured after 240 min. Additionally, 100% decolorization and 20% mineralization of MB were removed at pH 10 and UV 254nm, with a ZnO/SnO2 dosage of 0.75 g/L and an initial MB concentration of 5 ppm, as measured after 240 min. The experimental results for degradation of binary dye mixture revealed that 99.6% decolorization of MB, 96.9% decolorization of RhB and 19.6% mineralization were achieved for a weight ratio of MB to RhB of 10:5 at pH 10 and UV 254nm, with a ZnO/SnO2 dosage of 0.75 g/L, as measured after 240 min. However, for a weight ratio of MB to RhB of 5:10, 99.3% decolorization of MB, 88.6% decolorization of RhB and 20.9% mineralization were obtained after 240 min under the same operating conditions.

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