M.Tech. (Department of Chemistry, Faculty of Applied and Computer Sciences), Vaal University of Technology. / Phenol, 2-chlorophenol (2-CP) is used in the manufacture of several chemical compounds including other chlorophenols, dyes, dentifrice and pesticides. The usage of these chemicals results in the discharge of 2-CP that is harmful to most biota in the environment. Therefore there is need to remove or degrade 2-CP from the environment, especially in water. This research focused on the synthesis, characterization and application of Ag doped semiconductor (TiO2, ZnO, and ZnS) nanoparticles for the removal of 2-CP from water. Sol-gel and co-precipitation methods were used to synthesize the nanoparticles with different Ag contents (1%, 3% and 5%). Silver metal was used as a doping agent due to its antibacterial activity and ability to improve the photocatalytic activity of the semiconductors for 2-CPdegradation under UV irradiation. Characterization techniques such as X-ray diffraction (XRD), Fourier transform infrared (FTIR), Ultra-violet visible spectroscopy (UV-Vis) and photoluminescence spectra (PL) were used to characterize the structural, optical and physical properties of the nanoparticles, while Transmission electron microscopy (TEM) was used to characterize the surface of the nanoparticles. The XRD results confirmed the formation of anatase, wurtzite and blend phases of TiO2, ZnO and ZnS nanoparticles, respectively. The band gaps of the synthesized nanoparticles were 3.42 eV, 3.23 eV and 3.12 eV for TiO2, ZnO and ZnS nanoparticles respectively. The TEM images showed that all synthesized nanoparticles were uniform in shape. Photocatalytic degradation of 2-CP under UV irradiation confirmed that the semiconductor’s photocatalytic activities improved with the addition of Ag ions. The best removal percentage was obtained at doped Ag percentages of 5, 1 and 5 % using TiO2, ZnO and ZnS, respectively. In addition, the effects of various parameters affecting the photocatalytic degradation such as pH, initial concentrations of 2-CP and amount of catalyst (Ag doped TiO2, ZnO and ZnS, respectively) loading were examined and optimized. At the different initial concentrations of 2-CP, namely, 8, 20 and 50 ppm, the highest degradation efficiency was obtained at pH of 10.5 and 5 mg of catalyst dosage. However a decrease in initial concentration of 2-CP showed an increase in the photocatalytic efficiency. The degradation percentage of 2-CP obtained with Ag doped TiO2; ZnO and ZnS nanoparticles were 74.74, 57.8 and 45.49 %, respectively. Doping of these materials with Ag enhanced their photocatalytic activity; thus, they have the potential of degrading phenolic compounds, especially 2-chlorophenol, in water.

La photocatalyse est une technologie d’oxydation avancée qui peut être utilisée pour améliorer la qualité de l'air dans les environnements intérieurs et pourrait être mise en œuvre dans les milieux médicaux. Dans les hôpitaux, les salles d'opération sont très exigeantes en matière de qualité de l'air intérieur et nécessitent des systèmes qui minimisent les concentrations des polluants générés par les différentes activités. Dans ce travail, le devenir de deux polluants spécifiques des blocs opératoires, l’acrylonitrile (produit chimique trouvé dans la fumée chirurgicale) et l'isoflurane (gaz anesthésique) lorsqu'ils passent dans un dispositif de traitement d’air photocatalytique est étudié. Tout d'abord, une évaluation paramétrique de la dégradation de l'isoflurane et de l'acrylonitrile en étudiant l'influence de la vitesse de l'air, de l'intensité lumineuse, de la géométrie du média photocatalytique, de la concentration initiale en polluants, de la présence de co-polluants chimiques, de la présence de particules et l’humidité relative sur leur efficacité de dégradation est réalisée. En second lieu, l’innocuité de l’utilisation de ce procédé pour la dégradation de l’isoflurane et de l’acrylonitrile par l’identification des éventuels intermédiaires formés au cours de leur dégradation est étudiée. Les expériences sont menées dans un réacteur dynamique en boucle fermée conçu pour étudier les polluants à faibles concentrations. Enfin, pour mieux comprendre comment le changement de géométrie du média photocatalytique influence l'efficacité de la dégradation, des simulations avec ANSYS14.5 sont effectuées et discutées au regard des résultats expérimentaux. / Photocatalytic oxidation (PCO) is an advanced air cleaning technology that is used asa means to improve air quality in indoor environments and could potentially be used inthe operating rooms (OR). In hospitals, operating rooms (ORs) are very demanding interms of the indoor air quality (IAQ) and require systems that minimize the concentrations of pollutants. In this work, the fate of two OR pollutants acrylonitrile (chemical found insurgical smoke) and isoflurane (anesthetic gas) when they go through a PCO device was investigated. Firstly, a parametric evaluation on the degradation of isoflurane and acrylonitrile by studying the influence of air velocity, light intensity, the change in media geometry, initial pollutant concentration, presence of chemical co-pollutants, presence of particles (bioaerosols) and relative humidity on their degradation efficiencies is performed. Secondly the safety of the use of PCO for the degradation of isoflurane and acrylonitrile through the identification of possible intermediates formed during their degradation is evaluated. The experiments were conducted in a closed loop reactor which has been designed to study low concentration air pollutants and has also been recently modeled. Finally, to better understand how the change in media geometry influenced the degradation efficiency, simulations with ANSYS 14.5 were performed and discussed.

The purpose of this research was to investigate the kinetics and mechanisms of the photocatalytic degradation of organic substances in the presence of anions (bromide and chloride), using titanium dioxide as a photocatalyst. Tris(hydroxymethyl)aminomethane (Tris) and methanol were the organic substances used as probes. Photocatalytic degradation of the probes produces formaldehyde through reaction with hydroxyl radicals at the surface of the photocatalyst. The product was quantified using a modified Hantzsch reaction and UV-Vis spectroscopy at the fixed wavelength 368 nm. It was found that having bromide present in the reaction mixture resulted in an increase in the rate of formation of formaldehyde from Tris, while it resulted in a decrease from methanol. Bromide on the surface of the photocatalyst reacts with the hydroxyl radicals to form reactive halogen species (RHS). This study proposes that the RHS Br2•- oxidises the probe into a cation radical, which initialises the probe degradation and the subsequent formation of formaldehyde. Conversion from hydroxyl radicals to RHS leads to a greater selectivity in formaldehyde production. Increased selectivity of attack towards electron-rich centres can explain the observed results with the different probes in this study. A linear combination expression of the total production of formaldehyde was developed, through which the X-factor, a ratio of the production of formaldehyde by RHS relative to the production of formaldehyde by hydroxyl radicals, was calculated. However, no realistic values were obtained when calculating the X-factor for different anion concentrations, thus indicating that factors other than competition kinetics affect the degradation. No conclusions could be drawn regarding the effect of chloride on the formation of formaldehyde from Tris and methanol, as the results were ambiguous. / Syftet med denna studie var att undersöka mekanismer och kinetik bakom fotokatalytisk nedbrytning av organiska molekyler i närvaro av anjoner (bromid och klorid), där titandioxid användes som fotokatalysator. Tris(hydroxymetyl)aminometan (Tris) och metanol var de organiska substanserna som studerades. Den fotokatalytiska nedbrytningen av proberna resulterar i formaldehyd via reaktion med hydroxylradikaler på fotokatalysatorns yta. Produkten kan sedan kvantifieras genom en modifierad version av Hantzsch-reaktionen följt av UV-Vis spektroskopi vid en fixerad våglängd på 368 nm. Studien kom fram till att närvaron av bromid i reaktionslösningen resulterade i en ökad produktionshastighet av formaldehyd från Tris, medan det resulterade i en minskning från metanol. Bromid på ytan av fotokatalysatorn reagerar med hydroxylradikaler och bildar reaktiva halogena molekyler (RHS). Denna studie föreslår att RHS:en Br2•- oxiderar proben till en radikalkatjon, som initierar nedbrytningen av proben och efterföljande bildning av formaldehyd. Omvandling från hydroxylradikaler till RHS leder till högre selektivitet av bildning av formaldehyd. Ökad selektivitet av attacker mot elektronrika center kan förklara de observerade resultaten med de olika proberna i denna studie. Ett linjärkombinationsuttryck av den totala produktionen av formaldehyd utvecklades, från vilket X-faktorn, ett förhållande av produktionen av formaldehyd via RHS relativt till produktionen av formaldehyd via hydroxylradikaler, kunde beräknas. Inga realistiska värden erhölls dock vid beräkningen av X-faktorn för olika anjonskoncentrationer, vilket indikerar att andra faktorer än konkurrenskinetik påverkar nedbrytningen. Inga slutsatser kunde dras gällande klorids effekt på bildningen av formaldehyd från Tris och metanol, då resultaten var tvetydiga.

During the global pandemic of coronavirus, the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) outbreak, the world was desperately searching for simpler yet more effective solutions to stop the spread of coronavirus (COVID-19). Since no one was prepared for the fast spread of such a contagious virus, there was a shortage of proper protective solutions to stop the spread. Large quantities of alcohol-based disinfectant and hand sanitizers were used, but it led to global shortages. It is desired to have a water-based, easily applied, low-cost and long-lasting disinfectant that can prevent the spread of coronavirus on any surface, without the issue of skin allergies or skin-drying as often found while using alcohol. Inspired by nature, chitosan (CS), a natural biopolymer with well-known antimicrobial and film-forming properties, was tested in this study for the preparation of coatings spread onto various surfaces and the antiviral effect was evaluated. Zinc oxide (ZnO), a material generally recognized as safe (GRAS) by the US Food and Drug Administration (FDA), is a photocatalyst that was embedded in chitosan to enhance the antimicrobial and antiviral performance of the coatings. In order to apply water-based chitosan formulation on hydrophobic polypropylene (PP) surgical mask and polyethylene terephthalate (PET) surface, the plastics were treated with either oxygen plasma or corona plasma to improve the surface hydrophilicity. The corona plasma treatment decreased the water contact angle (WCA) of the surgical mask from approximately 125° to 101° and drastically reduced WCA of the PET film from approximately 100° to 29°. The PET film was coated with CS – ZnO nanocomposite, which contains 1% chitosan and 5 wt.% (w.r.t weight of chitosan) ZnO nanoparticles. The capability of photocatalytic degradation of CS – ZnO coating was demonstrated during the degradation of methylene blue dye molecules. Additionally, we evaluated the antiviral effect of the CS – ZnO nanocomposite coating on PET plastic films under typical room lighting conditions by measuring the inactivation of lentivirus. This approach utilizes the pseudotype system, which is a reliable tool to study under conventional biosafety conditions, particularly for certain pathogenic strains of coronaviruses (CoVs) which have a strong pathogenicity. / Under den globala coronapandemin, utbrottet av allvarligt akut respiratoriskt syndrom coronavirus 2 (SARS-CoV-2), sökte världen desperat efter enklare men ändå mer effektiva lösningar för att stoppa spridningen av coronaviruset (COVID-19). Eftersom ingen var förberedd på en så smittsam sjukdom uppstod en brist på lämpliga skyddsmetoder för att stoppa spridningen. Stora mängder alkoholbaserade desinfektionsmedel och handdesinfektionsmedel användes, vilket skapade en global brist. Det önskades en vattenbaserad, lättapplicerad, kostnadseffektiv och långvarig desinfektionsmedel som kunde förhindra spridningen av coronaviruset på vilken yta som helst, utan problem med allergiska reaktioner eller uttorkning av huden som ofta uppstår vid användning av alkohol. Med inspiration från naturen testades kitosan, en naturlig biopolymer med välkända antimikrobiella och film-formande egenskaper, för att göra beläggningar på olika ytor och testa deras antivirala effekt. Zinkoxid (ZnO), ett material som allmänt erkänns som säkert (GRAS) av US Food and Drug Administration (FDA), är en fotokatalysator och användes i kitosanbeläggningen för att förbättra den antimikrobiella och antivirala effekten. För att applicera den vattenbaserade kitosanformuleringen på hydrofoba ytor på en kirurgisk mask av polypropen (PP) och en plastfilm av polyetylentereftalat (PET), behandlades plasterna med antingen O2 eller corona plasma för att förbättra ytornas hydrofilicitet. Behandlingen av corona plasma minskade vattenkontaktvinkeln på den kirurgiska masken från cirka 125° till 101° och för PET-filmen från cirka 100° till 29°. PET-filmen belades med CS – ZnO nanokomposit, som innehåller 1% kitosan och 5 wt.% (med avseende på vikten av kitosan) ZnO nanopartiklar. Förmågan till fotokatalytisk nedbrytning av CS – ZnO-beläggningen demonstrerades genom att bryta ned metylenblå färgmolekyler. Dessutom utvärderades vi den antivirala effekten av CS – ZnO nanokompositbeläggningen på PET-filmer i normal rumsbelysning genom att mäta dess förmåga att inaktivera lentivirus. Denna metod använder pseudotypsystemet, vilket är ett tillförlitligt verktyg för att studera under konventionella biosäkerhetsförhållanden, särskilt för vissa patogena stammar av coronavirusen (CoVs) som har en hög patogenicitet.

京都大学 / 新制・課程博士 / 博士(人間・環境学) / 甲第24693号 / 人博第1066号 / 新制||人||250(附属図書館) / 2022||人博||1066(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 吉田 寿雄, 教授 田部 勢津久, 教授 中村 敏浩, 教授 寺村 謙太郎 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DFAM

The photocatalytic degradation of the wastewater dye pollutant methylene blue (MB) at ZnO nanostructured porous thin films, deposited by direct current reactive magnetron sputtering on Si substrates, was studied. It was observed that over 4 photocatalytic cycles (0.3 mg · l−1 MB solution, 540 minUV irradiation), the rate constant k of MB degradation decreased by ∼50%, varying in the range (1.54 ÷ 0.78) · 10–9 (mol·l−1·min−1). For a deeper analysis of the photodegradation mechanism, detailed information on the nanostructured ZnO surface morphology and local surface and subsurface chemistry (nonstoichiometry) were obtained by using scanning electron microscopy (SEM) and x-ray photoelectron spectroscopy (XPS) as complementary analytical methods. The SEM studies revealed that at the surface of the nanostructured ZnO thin films a coral reef structure containing polycrystalline coral dendrites is present, and that, after the photocatalytic experiments, the sizes of individual crystallites increased, varying in the range 43 ÷ 76 nm for the longer axis, and in the range 28 ÷ 58 nm for the shorter axis. In turn, the XPS studies showed a slight non-stoichiometry, mainly defined by the relative [O]/[Zn] concentration of ca. 1.4, whereas [C]/[Zn] was ca. 1.2, both before and after the photocatalytic experiments. This phenomenon was directly related to the presence of superficial ZnO lattice oxygen atoms that can participate in the oxidation of the adsorbed MB molecules, as well as to the presence of surface hydroxyl groups acting as hole-acceptors to produce OH· radicals, which can be responsible for the generation of superoxide ions. In addition, after experiments, the XPS measurements revealed the presence of carboxyl and carbonyl functional groups, ascribable to the oxidation by-products formed during the photodegradation of MB.

Les processus photocatalytiques à la surface d’oxydes métalliques semi-conducteurs font l’objet d’intensesrecherches au niveau mondial car ils constituent des alternatives efficaces, respectueuses de l’environnement etpeu coûteuses aux méthodes conventionnelles dans les domaines de la purification de l’eau et de l’air, et de laproduction « verte » d’hydrogène. Cependant, certaines limitations pour atteindre des efficacitésphotocatalytiques élevées ont été mises en évidence avec les matériaux semiconducteurs classiques du fait de larecombinaison rapide des porteurs de charge générés par illumination. Le développement de photocatalyseurs àbase d’héterostuctures obtenues par dépôt de métaux à la surface de matériaux semiconducteurs ou parassociation de deux semiconducteurs possédant des bandes d’énergie bien positionnées devrait permettre delimiter ces phénomènes de recombinaison via un transfert de charge vectoriel. Dans ce contexte, trois typesd’hétérostructures telles que des nanomatériaux à base d’hétérojonction semiconducteur n/semiconducteur n(SnO2/ZnO), metal/semiconducteur n (RuO2/TiO2 and RuO2/ZnO) et semiconducteur p/semiconducteur n(NiO/TiO2) ont été synthétisées avec succès par différentes voies liquides. Leur composition, leur texture, leurstructure et leur morphologie ont été caractérisées par spectroscopies FTIR et Raman, par diffraction des rayonsX, microscopie électronique en transmission (MET) et porosimétrie de sorption d’azote. Par ailleurs, unecombinaison judicieuse des données issues de mesures effectuées par spectroscopie UV-visible en réflexiondiffuse (DRS) et par spectroscopies de photoélectrons X (XPS) et UV (UPS) a permis de déterminer lediagramme d’énergie des bandes pour chaque système étudié. Les catalyseurs ainsi obtenus ont conduit à desefficacités photocatalytiques plus élevées qu’avec le dioxyde de titane P25 pour la dégradation de colorantsorganiques (bleu de méthylène, l’orangé de méthyle) et la production d’hydrogène. En particulier, lesnanocomposites RuO2/TiO2 et NiO/TiO2 contenant une quantité optimale de RuO2 (5 % en masse) et de NiO(1% en masse), respectivement, ont conduit aux efficacités photocatalytiques les plus importantes pour laproduction d’hydrogène. Ces excellentes performances photocatalytiques ont été interprétées en termesd’alignement adéquat des bandes d’énergies des matériaux associé à des propriétés texturales et structuralesfavorables. Ce concept de photocatalyseurs à base d’hétérojonctions semiconductrices d’activité élevée devrait àl’avenir trouver des débouchés industriels dans les domaines de l’élimination de l’environnement de composésorganiques indésirables et de la production « verte » d’hydrogène. / Photocatalytic processes over semiconducting oxide surfaces have attracted worldwide attention aspotentially efficient, environmentally friendly and low cost methods for water/air purification as well as forrenewable hydrogen production. However, some limitations to achieve high photocatalytic efficiencies havebeen found due to the fast recombination of the charge carriers. Development of heterostucture photocatalystsby depositing metals on the surface of semiconductors or by coupling two semiconductors with suitable bandedge position can reduce recombination phenomena by vectorial transfer of charge carriers. To draw newprospects in this domain, three different kinds of heterostructures such as n-type/n-type semiconductor(SnO2/ZnO), metal/n-type semiconductor (RuO2/TiO2 and RuO2/ZnO) and p-type/n-type semiconductor(NiO/TiO2) heterojunction nanomaterials were successfully prepared by solution process. Their composition,texture, structure and morphology were thoroughly characterized by FTIR, X-ray diffraction (XRD), Ramanspectroscopy, transmission electron microscopy (TEM) and N2 sorption measurements. On the other hand, asuitable combination of UV–visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy(XPS) and ultraviolet photoemission spectroscopy (UPS) data provided the energy band diagram for eachsystem. The as-prepared heterojunction photocatalysts showed higher photocatalytic efficiency than P25 TiO2for the degradation of organic dyes (i.e. methylene blue and methyl orange) and the production of hydrogen.Particularly, heterostructure RuO2/TiO2 and NiO/TiO2 nanocomposites with optimum loading of RuO2 (5 wt %)and NiO (1 wt %), respectively, yielded the highest photocatalytic activities for the production of hydrogen.These enhanced performances were rationalized in terms of suitable band alignment as evidenced by XPS/UPSmeasurements along with their good textural and structural properties. This concept of semiconductingheterojunction nanocatalysts with high photocatlytic activity should find industrial application in the future toremove undesirable organics from the environment and to produce renewable hydrogen.

Neste trabalho foram desenvolvidos e avaliados sistemas integrados de fotodegradação de material orgânico precedendo a determinação voltamétrica, em batch e em fluxo, de metais pesados em níveis de traço, em amostras de água e outras matrizes. Em particular, pela primeira vez, foi proposto, para a abertura das amostras, o método da degradação fotocatalítica mediada por TiO2 (Degussa P-25, via de regra 0,1% em peso) em suspensão. O quelato Cd(II)-EDTA atuou como sistema modelo nesta investigação baseada na recuperação do sinal voltamétrico do metal, inicialmente suprimido, através da parcial ou total destruição do ligante orgânico. Mostrou-se que a degradação fotocatalítica permite acelerar significativamente o processo, especialmente na presença de scavengers de elétrons, como O2 e a temperaturas acima da ambiente. Além disso, o maior aproveitamento da região próxima ao visível do espectro de emissão das lâmpadas, proporciona uma serie de vantagens práticas, como o uso de bobinas de PTFE, no lugar das de quartzo, para a exposição das amostras à radiação ou o emprego de lâmpadas de fluorescência no lugar das de vapor de mercúrio. Observou-se que a presença de partículas de TiO2 não afeta significativamente o sinal polarográfico (NPP) e voltamétrico (ASV) do Cd(II), apesar da deposição de certa quantidade deste óxido na superficie do eletrodo, ocasionando redução na sobretensão de H2 em meio ácido. Para metais com potencial redox menor que o Cd(II), a troca de eletrólito (em fluxo) representa uma elegante solução para contornar o problema. Já, fenômenos de adsorção do analito na superfície do TiO2, observado com Pb(II) mas não com Cd(II), puderam ser prevenidos no caso do Pb(II) com o uso de eletrólitos com pH<2. Examinou-se amplamente a operação em fluxo monosegmentado (MSFA), em sistemas integrados de injeção, fotodigestão, remoção de bolhas, desoxigenação, pré-concentração na superfície do EGPM e determinação, após eventual troca do eletrólito até níveis de Cd(II) da ordem de &#181;g L-1 e excessos de EDTA de até 1:500. Em particular, avaliou-se sistematicamente o uso de adaptadores FIA-EGPM. Estes estudos serviram de base para a idealização e a montagem de um sistema mecanizado prático e compacto, com operação de rotina controlado por software. Aplicações iniciais a alguns tipos de amostras ou matrizes reais (enriquecidas com padrão de Cd(II) e outros metais) que se seguiram ao aprofundado estudo do sistema modelo demonstraram a potencialidade da técnica, que passa a constituir atraente alternativa a ser considerada num leque de aplicações reais. / The present work aimed to develop and assess integrated devices for the photodegradation of organic matter prior to the voltammetric determination of trace heavy metals in water samples as well as in other matrixes, in batch and flowing systems. In particular, for the first time, for the sample digestion step a TiO2-mediated photocatalytic degradation method is proposed. This is based on the use of suspensions of Degussa P-25 TiO2, usually 0.1% w/w in the samples to be treated. The chelate Cd(II)-EDTA acted as a model system in investigations in which the voltammetric signal, suppressed at first, was recovered upon partial or total destruction of the organic ligand. Significant process enhancement speed is obtained with the photocatalytic degradation, especially in the presence of electron scavengers, such as dissolved O2, and at temperature above ambient values. In addition to this, thanks to this UV-TiO2-mediated method, it is possible not only to make use of a broader portion of the radiation but also to benefit from other advantages, such as the use of PTFE rather than quartz for the manufacture of the reactor coil and the utilisation of fluorescent lamps instead of mercury ones. It was observed that the presence of colloidal particles of TiO2 does not significantly affect the polarographic (NPP) nor the voltammetric (ASV) Cd(II) signal, even if a small amount is deposited onto the electrode surface. This causes the reduction of the H2 overvoltage in acidic medium. For metals with redox potential lower than cadmium\'s, the electrolyte exchange under flowing conditions represents an elegant way to overcome the problem. Phenomena of analyte adsorption on TiO2, observed for Pb(II) but not for Cd(II), were prevented in the case of Pb(II) bu operating at pH lower than 2. Monosegmented Flow Analysis systems (MSFA), integrating the injection, photodigestion, bubbles removal, degassing, preconcentration on the HMDE, determination and electrolyte exchange (as needed) steps, were thoroughly examined for Cd(II) levels of as little as few &#181;g L-1 in the presence of EDTA 1:500 (w/w). More notably, a number of FIA-MDE adaptors were systematically assessed. The investigations resulted in the design and construction of a practical and compact mechanised system, controlled by software, for routine analysis. Some applications on real samples or spiked real matrixes have shown the potentials of the technique which seems to represent an attractive alternative for a wider range of real applications.

Le développement de photocatalyseurs en couches minces supportées constitue un intérêt majeur autorisant une séparation efficace des produits de réaction, en dépit d’une réduction de leur surface spécifique par rapport à des nanopoudres du même matériau. La synthèse de revêtements de TiO2 par pulvérisation cathodique magnétron en condition réactive fait l’objet de recherches intensives. Cette technique permet de contrôler, à travers les paramètres d’élaboration, la structure et les propriétés physicochimiques et photocatalytiques des revêtements.Afin de s’affranchir de la contamination du catalyseur par le sodium du verre lors de traitements en température ou lors de recuits de couches déposées à l’ambiante, une barrière de diffusion en SiNx est intercalée et son épaisseur est fixée pour la suite de l’étude. Différentes couches de TiO2 ont été élaborées à haute pression dans un réacteur doté d’un système de contrôle en boucle fermée basé sur la spectroscopie d’émission optique. L’effet de la cristallisation in situ à différentes températures sur les différentes propriétés des revêtements TiO2 a été étudié et les propriétés de ces derniers ont été comparées à celles des échantillons synthétisés sur des substrats froids et recuits ex situ aux mêmes températures.Enfin, des premiers travaux portant sur l’influence de l’introduction de l’argent en différentes teneurs sur l’efficacité photocatalytique sous lumière visible des couches de TiO2 cristallisées in situ et ex situ sont présentés. / The development of supported photocatalysts thin films is of major interest allowing an efficient separation of the reaction products, in spite of their specific area reduction compared to nanometric scale powders. The synthesis of TiO2 coatings by reactive magnetron sputtering is the subject of intensive researches. This technique allows, trough the control of the deposition parameters, to manage the structure and the physicochemical and photocatalytic properties of the coatings. In order to hinder the sodium contamination of the catalyst from the glass substrate, either during in situ or ex situ heating of the coating, a SiNx diffusion barrier is intercalated with a fixed thickness. Different layers of TiO2 were prepared at high pressure in a reactor equipped with a closed-loop control system based on optical emission spectroscopy. The influence of the in situ crystallization at different temperatures on the properties of the TiO2 coatings was studied. These properties were compared with those of samples synthesized ex situ and at the same temperatures. Finally, first studies on the influence of silver enrichment at different contents on photocatalytic activity under visible light of TiO2 layers crystallized in situ and ex situ, are presented.

Photocatalytic processes over semiconducting oxide surfaces have attracted worldwide attention aspotentially efficient, environmentally friendly and low cost methods for water/air purification as well as forrenewable hydrogen production. However, some limitations to achieve high photocatalytic efficiencies havebeen found due to the fast recombination of the charge carriers. Development of heterostucture photocatalystsby depositing metals on the surface of semiconductors or by coupling two semiconductors with suitable bandedge position can reduce recombination phenomena by vectorial transfer of charge carriers. To draw newprospects in this domain, three different kinds of heterostructures such as n-type/n-type semiconductor(SnO2/ZnO), metal/n-type semiconductor (RuO2/TiO2 and RuO2/ZnO) and p-type/n-type semiconductor(NiO/TiO2) heterojunction nanomaterials were successfully prepared by solution process. Their composition,texture, structure and morphology were thoroughly characterized by FTIR, X-ray diffraction (XRD), Ramanspectroscopy, transmission electron microscopy (TEM) and N2 sorption measurements. On the other hand, asuitable combination of UV-visible diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy(XPS) and ultraviolet photoemission spectroscopy (UPS) data provided the energy band diagram for eachsystem. The as-prepared heterojunction photocatalysts showed higher photocatalytic efficiency than P25 TiO2for the degradation of organic dyes (i.e. methylene blue and methyl orange) and the production of hydrogen.Particularly, heterostructure RuO2/TiO2 and NiO/TiO2 nanocomposites with optimum loading of RuO2 (5 wt %)and NiO (1 wt %), respectively, yielded the highest photocatalytic activities for the production of hydrogen.These enhanced performances were rationalized in terms of suitable band alignment as evidenced by XPS/UPSmeasurements along with their good textural and structural properties. This concept of semiconductingheterojunction nanocatalysts with high photocatlytic activity should find industrial application in the future toremove undesirable organics from the environment and to produce renewable hydrogen.