Ce travail est consacré à l‟étude de la stabilité photochimique de nanocomposites polymère / argile en vue de leur insertion dans un système multicouche organique / inorganique pour l‟encapsulation des cellules solaires organiques. L‟objectif est d‟obtenir des films de nanocomposites polymère / argile flexibles, transparents, pouvant être mis en oeuvre par voie liquide, et photochimiquement stables. Dans une première partie, la caractérisation de nanocomposites à base d‟alcool polyvinylique (PVA) a montré leur aptitude à être insérés dans un système multicouche, notamment en ce qui concerne les propriétés barrière aux gaz. L‟étude du comportement photochimique du PVA basée sur l‟identification des produits de dégradation a permis de proposer un mécanisme de photooxydation du PVA et de déterminer les effets du photovieillissement sur les propriétés du film (rugosité, perméabilité, transparence). L‟insertion de nanocharges lamellaires (Montmorillonite, Laponite ou Hydroxydes Doubles Lamellaires) dans le PVA induit des effets différents (prodégradant ou stabilisant) en fonction de la nature de l‟argile (naturelle ou synthétique). Cependant, lors d‟irradiations en absence d‟oxygène, le PVA et les nanocomposites PVA / argile sont très stables. Enfin, l‟encapsulation alternant couche inorganique SiOx et couche organique PVA ou nanocomposite PVA / argile, permet d‟atteindre les niveaux de perméation requis pour les cellules solaires organiques pour des applications nomades. / This work was devoted to the study of the photochemical behavior of polymer / clay nanocomposites with the aim to use these nanocomposites in a multilayer organic / inorganic coating for organic solar cells encapsulation. The goal of this work was to obtain polymer / clay nanocomposite films that are flexible, transparent, which can be processed by solution, and that are photochemically stable. In the first part, the characterization of nanocomposites based on polyvinyl alcohol (PVA) has shown their ability to be inserted into a multilayer system, particularly for gas barrier properties. The study of the photochemical behavior of PVA with the identification of photodegradation products allows us to propose a photooxidation mechanism of PVA and to determine the effects of photoageing on the film properties (roughness, permeability, transparency). The insertion of lamellar nanofillers (Montmorillonite, Laponite or Layered Double Hydroxide) in PVA induces different effects (prodegradant or stabilising) depending on the nature of the clay (natural or synthetic). However, in absence of oxygen, the PVA and PVA / clay nanocomposites are very photostable. Finally, encapsulation alternating inorganic SiOx layer and PVA or PVA / clay nanocomposite layer permits to obtain the permeability levels required for organic solar cells in niche markets (consumer electronics).

La thérapie photodynamique (PDT) est une modalité de traitement des petites tumeurs localisées accessibles à la lumière. Son principe repose sur l'action conjuguée d'un photosensibilisant, de la lumière et de l'oxygène.<br />Une dosimétrie correcte est nécessaire pour assurer le traitement complet et des résultats reproductibles. Un élément clé de la dosimétrie à prendre en compte est le photoblanchiment, étant donné qu'il diminue la concentration du photosensibilisant au cours du traitement. Il est donc indispensable d'appréhender les mécanismes du photoblanchiment pour maîtriser au mieux le traitement.<br />Le rendement quantique de photoblanchiment de la m-THPBC en solution avec des protéines est de 5.7 x 10-4, les formes agrégées de photosensibilisants photoblanchissent plus lentement que les formes monomérisées. La m-THPBC se transforme sous l'effet de la lumière en m-THPC, ce rendement de phototransformation est influencé par l'état d'agrégation de la molécule. D'autres photoproduits tels que la m-THPBC di-hydroxylée et la m-THPC dihydroxylée ainsi que des dérivés dipyrines ont été observés. L'espèce responsable du photoblanchiment a été identifiée comme étant l'oxygène singulet. In vitro, la LD50 de la m-THPBC est 0.7 J cm-2. Le photoblanchiment est 3 à 5 fois plus sensible que celui de la m-THPC. L'étude de la localisation intra-cellulaire des photosensibilisants a montré une différence, la m-THPC s'accumulant dans le réticulum endoplasmique alors que la m-THPBC se localise dans les mitochondries. In vivo, la m-THPBC possède un photoblanchiment 4 à 10 fois plus élevé que la m-THPC, ainsi qu'une bonne accumulation tumorale. Ces résultats in vitro et in vivo sont particulièrement intéressants en terme de ratio thérapeutique, de sélectivité du traitement et de photosensibilité cutanée.

<p>Methylmercury is a bioaccumulative neurotoxin that severely endangers human health. Humans are exposed to methylmercury through consumption of contaminated aquatic fish. To date, effective strategies for preventing and remediating methylmercury contamination have remained elusive, mainly due to the lack of knowledge in regard to how methylmercury is generated and degraded in the aquatic environment. The goal of this dissertation was to study the mechanisms of two transformation processes that govern the fate of methylmercury in natural settings: microbial mercury methylation and methylmercury photodegradation. The role of mercury speciation (influenced by environmental conditions) in determining the reactivity of mercury in these biological and photochemical reactions was the focus of this research.</p><p>Methylmercury production in the aquatic environment is primarily mediated by anaerobic bacteria in surface sediments, particularly sulfate reducing bacteria (SRB). The efficiency of this process is dependent on the activity of the methylating bacteria and the availability of inorganic divalent mercury (Hg(II)). In sediment pore waters, Hg(II) associates with sulfides and dissolved organic matter (DOM) to form a continuum of chemical species that include dissolved molecules, polynuclear clusters, amorphous nanoparticles and after long term aging, bulk-scale crystalline particles. The methylation potential of these mercury species were examined using both pure cultures of SRB and sediment slurry microcosms. The results of these experiments indicated that the activity of SRB was largely determined by the supply of sulfate and labile carbon, which significantly influenced the net methylmercury production in sediment slurries. The availability of mercury for methylation decreased during aging. Dissolved Hg-sulfide (added as Hg(NO3)2 and Na2S) resulted in the highest methylmercury production. Although the methylation potential of humic-coated HgS nanoparticles decreased with an increase in the age of nanoparticle stock solutions, nano-HgS was substantially more available for microbial methylation relative to microparticulate HgS, possibly due to the smaller size, larger specific surface area and more disordered structure of the nanoparticles. Moreover, the methylation of mercury derived from nanoparticles cannot be explained by equilibrium speciation of mercury in the aqueous phase (<0.2 <em>f</em>Ým, the currently-accepted approach for assessing mercury bioavailability for methylation). Instead, the methylation potential of mercury sulfides appeared to correlate with the extent of dissolution and their reactivity in thiol ligand exchange. Additionally, partitioning of mercury to a diverse group of bulk-scale mineral particles and colloids (especially FeS) may be an important process controlling the mercury speciation and subsequent methylmercury production in natural sediments.</p><p>In surface waters, sunlight degradation is believed to be the predominant pathway for the decomposition of methylmercury. The mechanism of this process was investigated in a series of photodegradation experiments under natural sunlight and UV-A radiation, and in the presence of DOM and selective quenchers for photo-generated reactive intermediates. The results suggested that singlet oxygen generated from photosensitization of DOM drove the photodecomposition of methylmercury. The rate of methylmercury degradation depended on the type of methylmercury (CH3Hg+) binding ligand present in the water. CH3Hg -thiol (e.g., glutathione, mercaptoacetate, DOM) complexes were significantly more reactive in photodegradation compared to other methylmercury complexes (CH3HgCl or CH3HgOH), which may be because thiol-binding can effectively decrease the activation energy and thus enhance the reactivity of methylmercury molecules toward the Hg-C bond breaking process. These findings challenge the long-accepted view that water chemistry characteristics do not affect the kinetics of methylmercury sunlight degradation, and help explain recent field observation that methylmercury photodegradation occurred rapidly in freshwater lakes (where CH3Hg-DOM dominate methylmercury speciation) but relatively slowly in sea water (where CH3Hg-Cl control methylmercury speciation).</p><p>Overall, this dissertation has demonstrated that chemical speciation of inorganic mercury and methylmercury determines their availability for microbial methylation and sunlight degradation, respectively. The abundance of these available mercury species is influenced by a variety of environmental parameters (e.g., DOM). This dissertation work contributes mechanistic knowledge toward understanding the occurrence of methylmercury in the aquatic environment. This information will ultimately help construct quantitative models for accurately predicting and assessing the risks of mercury contamination.</p> / Dissertation

El objeto de la presente tesis es el desarrollo de metodologías analíticas rápidas para optimizar los procesos de degradación de colorantes orgánicos presentes en aguas residuales. Se ha llevado a cabo una revisión bibliográfica acerca de dichos procesos y las técnicas analíticas utilizadas para su monitorización y la identificación de posibles intermedios. Se han establecido nuevas metodologías analíticas basadas en herramientas quimiométricas tales como diseño de experimentos para optimizar procesos de fotodegradación con y sin catalizador. Se ha empleado resolución de curvas multivariante para la determinación simultánea de colorantes e intermedios durante estos procesos. Dado que la velocidad de degradación es el parámetro mas utilizado para evaluar la eficiencia de las fotodegradaciones se han evaluado todas las constantes involucradas en la degradación y/o la adsorción sobre el catalizador mediante HS-MCR-ALS. Se ha establecido una metodología analítica rápida para la determinación de colorantes basada en cromatografía de inyección secuencial (SIC). / The main aim of this thesis is the development of rapid analytical methodologies to optimize the photodegradation processes of organic azo dyes from industrial wastewater. A bibliographic review has been done concerning the most employed processes for dye removal and the analytical techniques used for the monitoring and the identification of intermediates. New analytical methodologies based on chemometric tools such as experimental designs have been established to optimize photodegradation processes with and without using heterogeneous catalysts. Multivariate curve resolution has been employed to determine simultaneously different dyes and intermediates along degradation processes. Since the degradation rate is the most employed parameter to evaluate the photodegradation efficiency all the kinetic constants involved in the degradation and/or the adsorption of the dye onto the catalyst have been evaluated by HS-MCR-ALS. Furthermore a rapid analytical methodology for dye determination based on sequential injection chromatography (SIC) has been established.

Organic light-emitting devices (OLEDs) have attracted significant attention because of their unique advantages for flat panel display applications. However, the relatively limited electroluminescence (EL) stability of blue emitting OLEDs continues to limit the commercialization of full color OLED displays. In most cases, the decrease in EL efficiency is also accompanied by a loss in blue color purity. Thus, the understanding of the degradation mechanisms of both the EL efficiency loss and color purity loss and the corresponding solutions to device degradation are required. In this thesis, electrical aging mechanism in anthracene-based OLEDs is investigated by using a number of techniques, including delayed EL measurements. The studies reveal that electrical aging is associated with an increasing concentration of an intermolecular species with a weak characteristic luminescence at around 535 nm. This species is capable of trapping charges, and thus plays a role as an electron-hole recombination center with prolonged electrical driving. Weak green luminescence from this species leads to an increased green/blue emission ratio, and causes the color purity loss in aged devices. The results also suggest that this species is also efficient in dissipating excitation energy non-radiatively, hence is capable of quenching singlet excitons in anthracene-based OLEDs, contributing to the observed efficiency loss with electrical aging. Moreover, the photo-stability of the organic/metal cathode interface in OLEDs is studied. Irradiating OLEDs by external illumination is found to result in a gradual increase in driving voltage and decrease in EL efficiency. This photo-induced degradation in device performance is found to be caused by changes at the organic/metal cathode interface that lead to a deterioration in electron injection. Evidence of photodegradation of the same interface, inherently, by device own EL, is also reported. The results uncover an important degradation mechanism in OLEDs and shed the light on a phenomenon that might limit the stability of other organic optoelectronic and photovoltaic devices.

Polyethylene (PE) is one of the most popular polymers used in daily life. However, saturated hydrocarbons cannot absorb the energy of light reaching to earth, so degradation process is rather slow which in return cause disposal problems. On the other hand, it was observed that in presence of oxygen and impurities in the polymer matrix, degradation can be rendered to shorter time intervals. This study covers investigation of effect of three different additives in UV induced oxidative degradation of polyethylene. In this work vanadium (III) acetylacetonate, serpentine and Cloisite 30B were used as additives both together and alone to follow photodegradation of polyethylene. Amount of vanadium (III) acetylacetonate was kept constant at 0.2 wt%, while serpentine and Cloisite 30B were used between 1 and 4 wt%. All compositions were prepared by using Brabender Torque Rheometer, and shaped as thin films by compression molding. Samples were irradiated by UV light up to 500 hours. Mechanical and spectroscopic measurements were carried out in certain time intervals to monitor the degradation. It can be concluded that all combinations of three additives showed the fastest degradation behavior compared to pure PE. In the absence of vanadium (III) acetylacetonate the degradation was slowed and fluctuations were observed in the residual percentage strain at break values. There was not a significant change in tensile strength of all samples. Carbonyl index values followed by FTIR were always in increasing manner. Thermal properties were also investigated by DSC Thermograms and they did not change significantly.

Organic light-emitting devices (OLEDs) have attracted significant attention because of their unique advantages for flat panel display applications. However, the relatively limited electroluminescence (EL) stability of blue emitting OLEDs continues to limit the commercialization of full color OLED displays. In most cases, the decrease in EL efficiency is also accompanied by a loss in blue color purity. Thus, the understanding of the degradation mechanisms of both the EL efficiency loss and color purity loss and the corresponding solutions to device degradation are required. In this thesis, electrical aging mechanism in anthracene-based OLEDs is investigated by using a number of techniques, including delayed EL measurements. The studies reveal that electrical aging is associated with an increasing concentration of an intermolecular species with a weak characteristic luminescence at around 535 nm. This species is capable of trapping charges, and thus plays a role as an electron-hole recombination center with prolonged electrical driving. Weak green luminescence from this species leads to an increased green/blue emission ratio, and causes the color purity loss in aged devices. The results also suggest that this species is also efficient in dissipating excitation energy non-radiatively, hence is capable of quenching singlet excitons in anthracene-based OLEDs, contributing to the observed efficiency loss with electrical aging. Moreover, the photo-stability of the organic/metal cathode interface in OLEDs is studied. Irradiating OLEDs by external illumination is found to result in a gradual increase in driving voltage and decrease in EL efficiency. This photo-induced degradation in device performance is found to be caused by changes at the organic/metal cathode interface that lead to a deterioration in electron injection. Evidence of photodegradation of the same interface, inherently, by device own EL, is also reported. The results uncover an important degradation mechanism in OLEDs and shed the light on a phenomenon that might limit the stability of other organic optoelectronic and photovoltaic devices.

La présence de résidus de médicaments a été évaluée dans des eaux superficielles et des effluents de huit stations d'épuration (quatre rejetant dans l'estuaire de Seine dans le cadre du projet Medseine financé par le GIP Seine- Aval, quatre dans le cadre du projet Toxstep financé par l'Anses (ex-Afsset). Une centaine de molécules a été systématiquement recherchée dans les deux types d'eaux en appliquant des méthodologies analytiques impliquant une extraction solide liquide suivie une analyse par LC-MS/MS. Un suivi saisonnier des rejets de médicaments a été effectué également. Des résidus de médicaments ont été systématiquement quantifiés dans les deux types d'eaux. Les concentrations mesurées dans des eaux de surface sont significatives pour certains composés : de 1 à 108 ng/L pour diclofénac, de 2 à 324 ng/L pour ibuprofène. Pour d'autres, les valeurs sont beaucoup plus faibles : de 2 à 13 ng/L pour sulfapyridine, de 1 à 5 ng/Lpour nordiazépam. Dans les effluents de STEP, les anti-inflammatoires, les β-bloquants, les macrolides et les fluoroquinolones sont plus souvent détectés. Leurs concentrations peuvent varier fortement : de 62 ng/L à 10 μg/L pour sotalol, de 39 ng/L à 8 μg/L pour aténolol et plus particulièrement de 32ng/L jusqu'à 127 μg/L pour paracétamol. Par ailleurs, la stabilité des résidus de médicaments vis à vis des rayonnements lumineux a été évaluée. Des irradiations UV (à 254 nm) pouvant potentiellement être utilisés en étape finaleavant rejet dans des zones particulièrement sensibles ont été appliquées (avec des doses allantjusqu'à 1500 J/m2. Par ailleurs, compte tenu du fait que les effluents sont ensuite majoritairement rejetés dans des eaux superficielles, ils sont soumis aux rayonnements solaires et cette exposition a également été évaluée. Le phénomène de photodégradation à 254 nm a été bien observé sur certains composés comme diclofénac, kétoprofène (> 90% dégradé), ciprofloxacine,norfloxacine (jusqu'à 75% dégradé). L'azithromycine, la clarithromycine, la carbamazépine et l'aténolol... sont des composés plus stables avec les rayonnements lumineux. En exposant sous lumière solaire simulée, le diclofénac, la kétoprofène, la ciprofloxacine et la norfloxacine sontaussi des composés sensibles (> 90% dégradé) après 24 h d'exposition (172,8 kJ/m2). La carbamazépine, la sulfaméthoxazole, l'aténolol, bisoprolol et métoprolol sont des composés plus stables observés.

Thesis (M.S.)--University of North Carolina Wilmington, 2008. / Title from PDF title page (October 20, 2008) Includes bibliographical references (p. 58-60)

Os contaminantes emergentes são considerados compostos onipresentes em águas, portanto investigar a degradação e comportamento dessas substâncias torna-se necessária, pois é reportado que estes compostos causam efeitos adversos em seres vivos. O composto 2-(tiocianometiltio) benzotiazol (TCMTB), considerado um contaminante emergente, é amplamente empregado na indústria do couro como biocida com a finalidade de inibir o desenvolvimento de microrganismos na pele. Sendo assim, o objetivo do presente trabalho foi estudar a degradação do contaminante emergente TCMTB, por meio das técnicas de fotólise direta com radiação UV, radiação solar e oxidação com ozônio. Experimentos de fotólise direta do TCMTB, em soluções aquosas com diferentes concentrações, em efluente do processo de remolho e efluente simulado do remolho, foram conduzidos em reator com lâmpada de vapor de mercúrio (250 W). O teste de hidrólise foi realizado protegido da luz, a temperatura ambiente com diferentes concentrações do TCMTB para observar o comportamento do contaminante na ausência de luz. O maior coeficiente de absorção molar foi medido e identificado em 220 e 280 nm como 20489 e 11317 M-1 cm-1, respectivamente, para pH 5,0. Os resultados experimentais da fotodegradação mostraram que TCMTB foi rapidamente degradado por fotólise direta em soluções aquosas em 30 min de tratamento fotolítico. Os resultados do estudo do pH, demonstraram que pH interfere no processo fotoquímico, uma vez que em condições alcalinas o composto é mais estável e a taxa de fotodegradação diminui. Os ensaios com o efluente do processo de remolho mostraram que a degradação do TCMTB tem comportamento semelhante às soluções aquosas. O efluente simulado do remolho mostrou que uma alta concentração do contaminante leva a um maior tempo de irradiação de luz para a degradação. A aplicação de luz natural evidenciou degradação mais lenta, mas ainda assim, foi possível observar degradação de até 96% para a concentração de 6 mg L-1 em 420 min. A utilização do oxidante ozônio como tratamento, alcançou 40% de remoção do contaminante em 30 min, assinalando a alta estabilidade do composto. Portanto, este trabalho aponta o potencial do uso de fotólise direta (luz v artificial), ou radiação solar (luz natural) para a degradação de contaminantes emergentes como o 2 (tiocianometiltio) benzotiazol (TCMTB). / Emerging contaminants are considered omnipresent compounds in water, thus investigate the degradation and behavior of these substances becomes necessary as it is reported that these compounds cause adverse effects on living beings. The 2- (thiocyanomethylthio) benzothiazole compound (TCMTB), considered an emerging contaminant, is widely used in the leather industry as a microbicide for the purpose of inhibiting the development of microorganisms in the skin and leather. In this context, the purpose of the present work was to study the degradation of the emerging contaminant TCMTB by direct photolysis with UV radiation, solar radiation and ozone. Experiments of direct photolysis of the TCMTB in aqueous solutions with different concentrations, in the effluent from the soaking process were conducted in a reactor with mercury vapor lamp (250 W). The hydrolysis test was performed protected from light at room temperature with different concentrations of TCMTB to observe the behavior of the contaminant in the absence of light. The highest molar absorption coefficient was measured and identified at 220 and 280 nm as 20489 and 11317 M-1 cm -1, respectively, at pH 5.0. The experimental results of photodegradation showed that TCMTB was rapidly degraded by direct photolysis in aqueous solutions in 30 min of photolytic treatment. The results of the pH study showed that pH interfered in the photochemical process, since under alkaline conditions the compound is more stable and the photodegradation rate decreases. Assays of the direct photolysis in effluent from the soaking process have shown that TCMTB degradation behaves similarly to aqueous solutions. The direct photolysis of the the simulated effluent from the soaking showed that a high concentration of the contaminant leads to a longer time of light irradiation for degradation. The application of natural light evidenced slower degradation, however, it was possible to observe degradation of up to 96% for the 6 mg L-1 concentration with 420 min. The use of the ozone oxidant as a treatment, achieved 40% removal of the contaminant for 30 min of treatment, indicating the high stability of the compound. Therefore, this work highlights the potential of the use of direct photolysis (artificial light), or solar radiation (natural light) for the vii degradation of emerging contaminants such as 2 (thiocyanomethylthio) benzothiazole (TCMTB).