Tesis: "UV photons"

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Hunniford, C. A. "Ionization and fragmentation of biologically relevant molecules by low energy ions and UV photons". Thesis, Queen's University Belfast, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.437413.

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Champion, Jason. "Photoevaporation des disques protoplanétaires par les photons UV d’étoiles massives proches : observation de proplyds et modélisation". Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30392/document.

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Les disques protoplanétaires entourant les jeunes étoiles sont les embryons des systèmes planétaires. A différentes phases de leur évolution, ils peuvent subir d'importantes pertes de masse par photoévaporation : des photons énergétiques, issus de l'étoile centrale ou d'une étoile voisine, chauffe le disque qui perd en masse sous l'échappement des particules. Cependant, ce mécanisme et la physique sous-jacente n'ont que peu été contraints par les observations. Les objectifs de cette thèse sont d'étudier la photoévaporation dans le cas particulier où elle est due à des photons FUV, d'identifier les principaux paramètres physiques (densité, température) et processus (chauffage et refroidissement) impliqués, et d'estimer son impact sur l'évolution dynamique des disques. L'étude repose sur le couplage observations - modélisations des disques photoévaporés par les photons UV en provenance d'étoiles massives proches. Ces objets, appelés "proplyds", ont leur disque entouré d'une large enveloppe nourrie des flots de photoévaporation. A l'aide d'un modèle 1D d'une région de photodissociation, j'ai développé un modèle pour l'émission dans l'infrarouge lointain des proplyds. Ce modèle a été utilisé pour interpréter les observations, issues principalement de Herschel, pour quatre proplyds. Il apparait que les conditions physiques en surface de leur disque sont similaires: une densité de l'ordre de 10 6 par cm cube et une température d'environ 1000 K. Cette température est maintenue par un équilibre dynamique : si la surface se refroidit, la perte de masse diminue et l'enveloppe se réduit. L'atténuation UV produite par l'enveloppe diminue alors et le disque, recevant plus de photons UV, chauffe. La majorité du disque peut s'échapper sous forme de flots de photoévaporation avec des taux de perte de masse de quelques 10 -7 masse solaire par an ou plus, en accord avec les observations précédentes des traceurs du gaz ionisé. A la suite de ce travail, j'ai développé un modèle hydrodynamique 1D pour étudier l'évolution dynamique d'un disque en photoévaporation par un champ de rayonnement externe. [...]
Protoplanetary disks are found around young stars, and represent the embryonic stage of planetary systems. At different phases of their evolution, disks may undergo substantial mass-loss by photoevaporation: energetic photons from the central or a nearby star heat the disk, hence particles can escape the gravitational potential and the disk loses mass. However, this mechanism, and the underlying physics regulating photoevaporation, have not been well constrained by observations so far. The aims of this thesis are to study photoevaporation, in the specific case when it is driven by far-UV photons, to identify the main physical parameters (density, temperature) and processes (gas heating and cooling mechanisms) that are involved, and to estimate its impact on the disk dynamical evolution. The study relies on coupling observations and models of disks being photoevaporated by UV photons coming from neighbouring massive star(s). Those objects, also known as "proplyds", appear as disks surrounded by a large cometary shaped envelope fed by the photoevaporation flows. Using a 1D code of the photodissociation region, I developed a model for the far-IR emission of proplyds. This model was used to interpret observations, mainly obtained with the Herschel Space Observatory, of four proplyds. We found similar physical conditions at their disk surface: a density of the order of 10 6 cm and a temperature about 1000 K. We found that this temperature is maintained by a dynamical equilibrium: if the disk surface cools, its mass-loss rate declines and the surrounding envelope is reduced. Consequently, the attenuation of the UV radiation field by the envelope decreases and the disk surface, receiving more UV photons, heats up. Most of the disk is thus able to escape through photoevaporation flows leading to mass-loss rates of the order of 10 -7 solar mass per year or more, in good agreement with earlier spectroscopic observations of ionised gas tracers. Following this work, I developed a 1D hydrodynamical code to study the dynamical evolution of an externally illuminated protoplanetary disk. [...]

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Lavigne, Claire. "Étude théorique et expérimentale de la propagation du rayonnement UV dans la basse atmosphère". Rouen, 2001. http://www.theses.fr/2001ROUES042.

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Dans l'atmosphère, les sources ponctuelles sont entourées d'un halo dû à la diffusion par les particules et les molécules. Sous certaines conditions météorologiques, le champ de luminance provenant de ce halo peut devenir une part non négligeable du signal détecté par un instrument grand champ. Il apparaît donc nécessaire de le caractériser correctement. Dans ce cadre, nous avons développé un code de calcul basé sur une méthode Monte Carlo, permettant de modéliser la propagation du rayonnement UV issu d'une source ponctuelle. Une étude bibliographique sur les propriétés optiques et les statistiques de concentration des différentes espèces absorbant et diffusant dans le domaine spectral considéré a également été menée. Elle a permis de définir les données d'entrée du code. La validation du modèle mis au point a été effectuée par comparaison avec des expériences. En raison de la faiblesse des signaux à détecter, la technique de comptage de photons s'est avérée être la mieux adaptée. Afin de préparer la campagne de mesures de validation, un travail de caractérisation approfondi en laboratoire a été entrepris sur des photomultiplicateurs et un imageur à comptage de photons. Finalement, les résultats issus des expériences réalisées en extérieur et ceux provenant du code Monte Carlo ont été comparés et un très bon accord entre ces différentes données a pu être observé.

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Bouras, Karima. "Re-doped SnO2 oxides for efficient UV-Vis to infrared photon conversion : application to solar cells". Thesis, Strasbourg, 2016. http://www.theses.fr/2016STRAD011/document.

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Ce travail a porté sur la synthèse et caractérisations structurales, optiques et électriques des films d’oxyde d'étain (SnOx) dopés avec des éléments de terres rares (RE: Néodyme, Praséodyme ou Ytterbium). L’objectif est de démontrer la conversion de photons UV voire Visible en photons rouges via ces films RE :SnOx, tout en conservant leurs propriétés d’oxydes transparents conducteurs. Les films ont été produits par des méthodes chimiques (sol-gel, précipitation) ou physiques (pulvérisation cathodique). Grâce à des analyses fines, nous avons pu corréler les propriétés structurales et de composition des couches RE :SnOx avec leurs propriétés d’émission de photons. Nous avons pu établir les conditions optimales de conversion photonique dans des systèmes à une seule ou double terre rare. Les mécanismes régissant le transfert dans ces films ont été avancés. Enfin, nous avons appliqué ces couches minces RE :SnOx optimisés sur des cellules solaires en silicium et en CIGS et nous avons montré une amélioration des paramètres photovoltaïques du dispositif ainsi qu’un net gain dans la réponse spectrale de la cellule dans l’UV
Spectral conversion using lanthanide doped materials with excellent performances is a great challenging topic and of particular interest for photovoltaic. This work aims at functionalizing transparent conductive oxide materials with rare earth elements for photons conversion purpose without affecting transparency and transport properties of the TCO. The spectral conversion targeted in this thesis is of type “down”, in other words, we aim at converting high energy UV photons into low energy visible or NIR photons useful to solar cells. For this purpose we investigated the doping process of SnO2 as a host material with different rare earths such as Nd, Tb, Pr, and Yb. To understand the insertion process and the optical activation of the rare earth, RE-doped SnO2 nanoparticles (powders) have been synthesised by two chemical methods: co-precipitation and sol-gel. The results have shown an efficient insertion of the RE into the SnO2 structure with excellent emission properties. In view of application of RE-doped SnOx thin films to solar cells, studies concerning NIR emitting RE have been conducted (Nd, Yb, and co-doping with Yb and Nd) using sputtering. Several deposition parameters and post deposition treatments have been done in order to find the best chemical environment favourable to the RE emission. We have precisely identified the region of the UV light converted into NIR photons and proposed several energy transfer mechanisms occurring between the host SnOx and the REs. In case of co-doping, a second spectral conversion process has been identified; visible photons can be efficiently converted into NIR photons through energy transfer from Nd3+ to Yb3+ ions. Finally, application of these conversion layers to solar cells such as CIGS and Si based have shown an improvement of the cells characteristics, among others the Field factor, the cell efficiency and the increase of the spectral response of the cell in the UV region, thanks to the conversion of the UV photons into NIR photons. The good electrical properties of the RE-doped SnOx layers have been highlighted as well. We believe that these conversion layers will provide a step ahead towards better solar cells performances

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5

Torres, Díaz Daniela. "Non-thermal desorption from model molecular ices - towards quantitative astrochemical data". Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF068.

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Cette thèse présente une étude expérimentale de la désorption non thermique de solides moléculaires physisorbés appelés glaces. La désorption non thermique est cruciale pour expliquer les abondances moléculaires en phase gaz observées dans divers environnements astrophysiques. Ce travail vise à mieux identifier les mécanismes directs et indirects de désorption induite par les photons UV et X et en contraindre les efficacités. Il implique donc l'étude de la désorption induite par les électrons. Sous irradiation UV, des électrons de basse énergie sont créés au sein de la glace par ionisation en couche de valence des systèmes. Sous irradiation X, des électrons plus énergétiques sont créés par la relaxation Auger des systèmes suite à leur excitation ou ionisation en couches de cœur. L'approche expérimentale vise à mieux comprendre le rôle des électrons secondaires dans la désorption en comparant quantitativement les désorptions induites par photons et par électrons.Les glaces moléculaires ont été condensées à des températures cryogéniques (15-100K) sous ultra-vide. Elles ont été irradiées pour induire la désorption à l'aide de photons UV ou X au synchrotron SOLEIL sur le dispositif expérimental SPICES (MONARIS), ou d'électrons sur le dispositif SOMO (ISMO). Les espèces neutres désorbées ont été analysées et quantifiées en temps réel par spectrométrie de masse. Les résidus irradiés ont été ensuite analysés, notamment par désorption thermique et par spectroscopies vibrationnelles. L'effet de plusieurs paramètres, tels que la morphologie de la glace, son épaisseur, l'énergie d'irradiation et la dose, a été étudié. Une intéressante complémentarité est obtenue entre des expériences exploratoires et flexibles sous irradiation d'électrons au laboratoire et celles menées au synchrotron.Deux systèmes modèles ont été étudiés en détail : l'acétonitrile et l'ammoniac. Pour l'acétonitrile, des expériences de désorption induite par électrons simulant les Auger de l'azote et du carbone ont permis d'observer la désorption de la molécule intacte, ainsi que divers produits d'irradiation, dont le méthane et le cyanure d'hydrogène. Les voies de formation possibles pour chaque produit sont discutées. Pour l'ammoniac, les expériences ont inclus des irradiations UV (5-12eV), par électrons de basse énergie (2-20eV), par rayons X au seuil de l'azote et par électrons de haute énergie (Auger de l'azote). Les rendements de désorption quantitatifs ont été déterminés pour l'ammoniac et l'azote moléculaire, principal produit observé dans tous les cas. Ces études reposent sur trois approches pour comprendre la désorption non thermique : i) la détermination des profondeurs pertinentes pour la désorption, ii) l'extraction de rendements quantitatifs et iii) la discussion des modèles cinétiques de désorption. Ces éléments permettent d'établir des comparaisons quantitatives entre les efficacités de désorption induite par photons et par électrons en molécules par particule incidente et en molécules par énergie déposée.Cette étude fournit des contraintes expérimentales pour les processus de désorption non thermique qui pourront alimenter les modèles chimiques des environnements astrophysiques. La détermination des rendements de désorption à différentes énergies de photons permet de calculer des rendements astrophysiques moyens pour un champ de rayonnement donné. L'identification et la quantification des produits d'irradiation contribuent à la compréhension de l'enrichissement chimique de la phase gazeuse. L'obtention par ce travail de valeurs en fonction de l'épaisseur montre l'existence de différents régimes où la désorption est dépendante ou non de l'épaisseur. Ces régimes varient en fonction du type et de l'énergie d'irradiation et doivent être intégrés dans les modèles. Des questions ouvertes subsistent concernant les contributions des processus de surface et de volume, ainsi que la dépendance des paramètres déterminés vis-à-vis de la composition de la glace
This thesis presents an experimental investigation of non-thermal desorption from physisorbed molecular solids, also called ices. Non-thermal desorption processes are crucial in explaining the observed abundances of gaseous molecules in various astrophysical environments. This work aims to identify the direct and indirect desorption mechanisms and better constrain desorption efficiencies induced by UV and X-ray photons. Therefore, it also implies studying electron-induced desorption. Under UV irradiation, valence shell ionisation creates low-energy electrons in the ice. While under X-ray irradiation, more energetic electrons are produced by Auger relaxation of the systems following their core-shell excitation or ionisation. The experimental approach seeks to better understand the role of secondary electrons in desorption by quantitatively comparing photon- and electron-induced desorption yields.Molecular ices were grown at cryogenic temperatures (15-100 K) and under ultra-high vacuum conditions. The samples were irradiated to induce desorption with the monochromatic output of UV or X-ray synchrotron beamlines at the SOLEIL facility using the SPICES setup (MONARIS) or electrons in the SOMO setup (ISMO). The desorbing neutral species were analysed and quantified during irradiation using mass spectrometry. Various techniques were used to analyse the irradiated residues, including thermal desorption and vibrational spectroscopies. The effect of multiple parameters, such as ice morphology, thickness, irradiation energy, and dose, was studied. An interesting complementarity was obtained between the laboratory's exploratory and flexible electron irradiation experiments and those carried out at the synchrotron.Two model systems were studied in detail: acetonitrile and ammonia. For acetonitrile, electron-induced desorption experiments simulating nitrogen and carbon Auger electrons were performed. Desorption of the intact molecule was observed, as well as desorption of multiple irradiation products, including methane and hydrogen cyanide. The possible formation routes for each product are reviewed. For ammonia, experiments included UV (5-12 eV), low-energy electron (2-20 eV), X-ray (N 1s edge) and high-energy electron (nitrogen Auger) irradiation. Quantitative desorption yields were determined for ammonia and molecular nitrogen, the main product observed across all the irradiation conditions. These studies rely on three key aspects to understand non-thermal desorption: i) determining the desorption-relevant depths, ii) extracting quantitative yields, and iii) discussing kinetic models of desorption. These elements enable quantitative comparisons between photon- and electron-induced desorption efficiencies in terms of molecules per incident particle and molecules per deposited energy.This study provides experimental constraints for non-thermal desorption processes that can feed chemical models of astrophysical environments. The determination of desorption yields at different photon energies can be used to calculate average astrophysical yields according to the spectrum of a particular environment. Identifying and quantifying irradiation products is also essential for understanding gas-phase chemical enrichment. The thickness-dependent values obtained in this thesis show the existence of different regimes where desorption is dependent or independent of thickness. Said regimes depend on the irradiation type and energy considered and should be included in models. Open questions remain regarding the different contributions from surface and bulk processes and the dependence of the determined parameters on ice composition

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Helali, Sihem. "Application de la photocatalyse pour la dégradation des polluants chimiques et bactériologiques dans l'eau en utilisant des catalyseurs irradiés par des photons de lumière naturelle ou artificielle (UV‐A /UV‐B)". Phd thesis, Université Claude Bernard - Lyon I, 2012. http://tel.archives-ouvertes.fr/tel-00876027.

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La dégradation photocatalytique de deux amines, la méthylamine (MA) et la diméthylamine (DMA), a été étudiée en présence de TiO2 Degussa P25. Différents paramètres ont été étudiés: l'adsorption à l'obscurité et sous UV, la photolyse, les cinétiques de dégradation, l'effet du pH, l'effet de la nature et de l'intensité du flux photonique ainsi que les voies de dégradation de la MA et DMA.A l'obscurité, le taux de recouvrement des groupes OH est similaire pour la MA et DMA. Sous UV, ce taux devient deux fois plus élevé pour la MA. Les réactivités de MA et DMA sont directement corrélées à leur adsorption sous UV. Les atomes d'azote sont principalement décomposés en ammonium. Le nitrite a été également détecté, mais rapidement oxydé en nitrate. À pH basique, l'hydrolyse photo‐assisté et l'attaque de OH* sur l'atome N augmente. DMA est essentiellement transformé en MA. Les analyses du Carbone Organique Total (COT) montrent la présence de produits finaux contenant de l'azote difficilement minéralisables. Nous avons montré que, quelle que soit l'énergie des photons (UV‐A ou UV‐B), le rendement quantique reste constant et égal à 0,033.L'inactivation photocatalytique de E. coli en présence de la lumière solaire naturelle en absence (SODIS) et en présence de différents catalyseurs a été étudiée. L'effet de la température sur l'inactivation de E. coli a été aussi étudié. Les résultats ont montré que l'addition des différents types de catalyseurs accélère l'effet bactéricide du rayonnement solaire. Aucun phénomène de reviviscence bactérien n'a été observé après l'arrêt de l'exposition solaire durant au moins 72 heures. Seulement les ions ammonium et potassium ont été détectés au cours de l'inactivation de E. coli en accord avec la perforation de la membrane et l'oxydation des protéines.

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Helali, Sihem. "Application de la photocatalyse pour la dégradation des polluants chimiques et bactériologiques dans l’eau en utilisant des catalyseurs irradiés par des photons de lumière naturelle ou artificielle (UV‐A /UV‐B)". Thesis, Lyon 1, 2012. http://www.theses.fr/2012LYO10316/document.

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La dégradation photocatalytique de deux amines, la méthylamine (MA) et la diméthylamine (DMA), a été étudiée en présence de TiO2 Degussa P25. Différents paramètres ont été étudiés: l'adsorption à l’obscurité et sous UV, la photolyse, les cinétiques de dégradation, l'effet du pH, l'effet de la nature et de l'intensité du flux photonique ainsi que les voies de dégradation de la MA et DMA.A l’obscurité, le taux de recouvrement des groupes OH est similaire pour la MA et DMA. Sous UV, ce taux devient deux fois plus élevé pour la MA. Les réactivités de MA et DMA sont directement corrélées à leur adsorption sous UV. Les atomes d'azote sont principalement décomposés en ammonium. Le nitrite a été également détecté, mais rapidement oxydé en nitrate. À pH basique, l'hydrolyse photo‐assisté et l'attaque de OH• sur l’atome N augmente. DMA est essentiellement transformé en MA. Les analyses du Carbone Organique Total (COT) montrent la présence de produits finaux contenant de l’azote difficilement minéralisables. Nous avons montré que, quelle que soit l'énergie des photons (UV‐A ou UV‐B), le rendement quantique reste constant et égal à 0,033.L'inactivation photocatalytique de E. coli en présence de la lumière solaire naturelle en absence (SODIS) et en présence de différents catalyseurs a été étudiée. L'effet de la température sur l'inactivation de E. coli a été aussi étudié. Les résultats ont montré que l’addition des différents types de catalyseurs accélère l'effet bactéricide du rayonnement solaire. Aucun phénomène de reviviscence bactérien n’a été observé après l'arrêt de l'exposition solaire durant au moins 72 heures. Seulement les ions ammonium et potassium ont été détectés au cours de l'inactivation de E. coli en accord avec la perforation de la membrane et l’oxydation des protéines
The photocatalytic degradation of two amino‐compounds, methylamine (MA) and dimethylamine (DMA) was investigated in the presence of UV‐irradiated TiO2 aqueous suspensions. Different parameters were studied: adsorption under dark and UV conditions, photolysis, kinetics of degradation, effect of pH, effect of the nature and intensities of photonic flux and finally the chemical pathway MA and DMA degradation.While, the percentage of covered OH in the dark was equal for MA and DMA, it becomes twice higher for MA under UV. The reactivity of MA and DMA is directly correlated with the adsorption under UV. The nitrogen atoms were decomposed mainly to ammonium. Nitrite was also formed but was rapidly oxidized to nitrate. At basic pH, photo assisted hydrolysis and the attack of OH• on N‐atom increase. DMA is mainly transformed to MA. Total Organic Carbon (TOC) analysis show the presence of final slightly mineralised intermediate compounds containing nitrogen atom. We shown that, whatever the energy of photons (UV‐A or UV‐B), the same quantum yield equal to 0.033 was obtained.The photocatalytic inactivation of E. coli under natural solar irradiation in the absence (SODIS) as well in the presence of different concentrations of varied photocatalysts has also been investigated. The effect of temperature on E. coli inactivation was studied. Results show that the additions of any types of catalyst to the water accelerate the bactericidal action of solar irradiation and leads to a total disinfection. No bacterial regrowth was observed during the subsequent dark period. Ammonium and potassium ions were formed during E. coli inactivation in agreement with the membrane perforation and the oxidation of proteins

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Bouvier, Stéphane. "Conception et mise au point d'un amplificateur integre rapide, a transimpedance, a faible bruit. Applicaiton a la detection de photons uv". Université Louis Pasteur (Strasbourg) (1971-2008), 1993. http://www.theses.fr/1993STR13255.

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Le travail accompli dans cette these porte sur la conception et la realisation d'un amplificateur a transimpedance associe a un detecteur de photo-electrons fonctionnant sur le principe de multiplication par avalanche. Les caracteristiques requises pour cette architecture sont les suivantes: mesures de courant, temps de montee inferieur a 15 nanosecondes, impedance d'entree de l'ordre de 100 ohms, gain de 100 millivolts par microampere, consommation inferieure a 100 milliwatts par canal et mise en forme du signal permettant la suppression de queue du signal ainsi que la compression de la dynamique. L'architecture globale comporte un preamplificateur faible bruit, a gain eleve, assurant la conversion courant tension, un etage de mise en forme, un etage tampon permettant la sortie differentielle sur 50 ohms et la compression dynamique. Un prototype a 4 voies, realise en technologie cmos, a confirme la validite de l'ensemble des concepts et des calculs developpes (fonctions de transfert, modeles de bruit)

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Denneval, Charline. "Design, synthèse et évaluation de contrastophores bimodaux pour l'imagerie par absorption à deux photons et par tomographie par émission de positons". Thesis, Rouen, INSA, 2014. http://www.theses.fr/2014ISAM0012/document.

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L’objectif de ce travail a porté sur l’élaboration d’une sonde bimodale ADP–TEP (absorption à deux photons–tomographie par emission de positons) pour des applications en imagerie médicale.Dans un premier temps, le projet a consisté en le design, la synthèse et l’évaluation des propriétés photophysiques d’une nouvelle série de chromophores diaziniques A–p–D (A : groupement électro-attracteur, p : lien conjugué, D : groupement électro-donneur). Des études de relation structure-propriétés photophysiques impliquant des modulations sur chacune des sous-structures (groupements A et D, lien p-conjugué) ont été réalisées puis étudiées en UV et en fluorescence. Suite à l’obtention de ces premiers résultats, des mesures d’absorption à deux photons ont été effectuées sur ces fluorophores.Dans un second temps, les fluorophores ont été modifiés afin de greffer des parties hydrophiles. Des propriétés photophysiques encourageantes ont été obtenues et des premiers tests en imagerie bi-photonique ont été réalisés.L’insertion du fluor radiomarqué est envisagée via l’insertion d’un groupement –BF2. Pour cela des structures chélatantes, « mimes de BODIPY », incorporant une pyrimidine ou un triazole ont été élaborées. Des premiers essais ont été conduits mais n’ont pas permis l’obtention des composés borés correspondants
The purpose of this subject has been the synthesis of a bimodal probe using TPA–PET techniques for a potential application in biological imaging.In this context, we have synthesized a new range of A–π –D fluorophores incorporating diazine (p-deficient heterocycle) as electron-withdrawing moiety, N,N-dimethylaniline as electron-donating part and fluorene as p-conjugated linker. In order to increase the conjugation along the scaffold, ethynyl and/or triazole bridges have been introduced on both sides of the fluorene. The UV/Vis and photoluminescence properties have been measured. Further to those results two-photon absorption cross-section of our fluorophores (dTPA) has been obtained. Following these promising results, hydrophilic compounds using PEG groups have been prepared and photoluminescence properties have been carried out. In order to use the boron center as a site for radiofluorination, the synthesis of "BODIPY-like" probes has been considered. A new series of pyrimidine and triazole ligand have been synthesized but the corresponding boron complexes haven’t been obtained

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Tao, Zhi. "Photodétection dans une large gamme de longueur d’onde : phototransistor CdSe QDs/RGO sur des nanofils de ZnO dans la gamme UV-Vis, PbS QDs avec un transistor organique C60 de type N imprimé dans la gamme proche IR". Thesis, Rennes 1, 2019. http://www.theses.fr/2019REN1S087.

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La détection de lumière dans une large gamme de longueur d’onde allant de l’UV au proche infrarouge est réalisée avec une sensibilité importante en utilisant l’effet d’amplification amené par un transistor à effet de champ et la capacité de détection dans une grande gamme de longueur d’onde amenée par des nanoparticules de CdSe et de PbS de diamètres différents. Dans une première partie, un FET utilisant une couche active de nanofils de ZnO est fabriqué. La détection de lumière UV-Vis est assurée en enrobant ces nanofils par un mélange de nanoparticules de CdSe et d’oxyde de graphène. L’oxyde de graphène assure une bonne transition des électrons crées par la lumière dans le CdSe vers le ZnO. La photo-réponse obtenue, supérieure à 104 A/W à 350 nm, a été multipliée par un facteur 100 dans la gamme 200-500nm en utilisant l’oxyde de graphène. Dans une seconde partie, la détection de lumière infrarouge a été assurée par des nanoparticules de PbS incorporées dans un transistor organique de type N utilisant du C60 comme couche active. Les électrodes en argent de ce transistor et son isolant de grille en photorésine SU8 sont déposés par impression. Les nanoparticules sont déposées en solution à l’interface entre le semiconducteur et l’isolant de grille. Ce phototransistor incorporé dans un inverseur a montré l’apparition d’un signal de sortie de 2V dû à l’application d’une lumière de 1050 nm de longueur d’onde et de 250 µw/cm2 de puissance
Detection of light in large wavelength range, from the UV to NIR, is got with high sensitivity by using the amplification of a field effect transistor and the ability of light detection in large range by CdSe and PbS quantum dots with different diameters. In the first part, a FET with ZnO nanowires active layer is fabricated. The light detection in UV-Vis range is insured thanks to CdSe QDs/RGO (Reduced Graphene Oxide) fragments decorating the surface of the ZnO nanowires RGO insures good transfer of photo-electrons induced by the light into the CdSe QDs towards ZnO. The responsivity, higher than 104 A/W at 350 nm, has been improved by 100 in 200-500 nm range by using RGO. In the second part, IR light detection has been insured by using PbS QDs embedded in N-type Organic FET using C60 film as active layer. Silver electrodes of this transistor and its SU8 photoresist gate insulator have been printed. QDs have been deposited in solution at the interface between the semiconducting layer and the gate insulator. This phototransistor has been used in an inverter. The output voltage of the inverter change by 2V under lighting with 1050 nm wavelength and 250 µW/cm2 power

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11

Fourcade, Paul. "Pompage séquentiel dans les lasers collisionnels x-uv. Etude d'un laser à fer neonoïde bi-impulsionnel a 25,5 nm en vue de la réalisation d'un double passage dans le milieu amplificateur. Application : photoionisation double dans le xénon, par absorption de photons lasers x-uv a 58 ev". Paris 13, 2001. http://www.theses.fr/2001PA132010.

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L'objectif ultime du travail expose dans cette thèse est la réalisation de lasers x collisionnels de grande qualité optique, pompes par une série d'impulsions laser de durée 100 ps, et comportant une cavité résonante. Des lasers x a demi-cavité, pompes par des impulsions de 600 ps, fonctionnent depuis plusieurs années et offrent des performances très supérieures a celles des lasers simple passage, plus courants. Cependant, les impulsions plus courtes, typiquement de 100 ps, donnent lieu a des gains plus élevés, mais la durée de vie des inversions de population est alors trop courte pour qu'une demi-cavité soit efficace. On envisage alors de régénérer le gain à l'aide d'une série d'impulsions successives et de synchroniser le passage du laser x dans la cavité avec le chauffage du plasma par les impulsions de pompe. Dans le travail actuel, nous avons caractérisé les émissions laser x produites par deux impulsions séparées temporellement de 800 ps, du point de vue de leurs intensités et de leurs caractéristiques géométriques (réfraction et divergence). Nous avons montre qu'il existe une valeur optimale de la préimpulsion permettant d'égaliser les intensités des deux impulsions laser x. Ce travail permet de préparer le terrain à l'installation ultérieure de cavités. Nous avons défini, grâce à des simulations numériques, la dimension optimale de la cavité en fonction de l'hydrodynamique du plasma et de la géométrie de l'expérience. Le développement des lasers x ne peut se concevoir sans le développement de leurs applications : nous présentons une première expérience de photoionisation multiphotonique utilisant un laser a 21. 2 nm pompe par une impulsion de 600 ps. Enfin, la course vers les courtes longueurs d'onde est aussi un moteur puissant des recherches sur les lasers x. Grace à une collaboration avec une équipe japonaise, nous avons pu tenter d'obtenir des émissions laser dans la fenêtre de l'eau, grâce au laser Gekko XII de l'université d'Osaka.

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12

Cossuet, Thomas. "Problématique de la polarité dans les nanofils de ZnO localisés, et hétérostructures reliées pour l’opto-électronique". Thesis, Université Grenoble Alpes (ComUE), 2018. http://www.theses.fr/2018GREAI086/document.

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Le développement d’architectures nanostructurées originales composées de matériaux abondants et non-toxiques fait l’objet d’un fort intérêt de la communauté scientifique pour la fabrication de dispositifs fonctionnels efficaces et à bas coût suivant des méthodes d’élaborations faciles à mettre en œuvre. Les réseaux de nanofils de ZnO élaborés par dépôt en bain chimique sont, à ce titre, extrêmement prometteurs. L’étude des propriétés de ces réseaux de nanofils et leur intégration efficace au sein de dispositifs nécessitent toutefois un contrôle avancé de leurs propriétés structurales et physiques, notamment en terme de polarité, à l’aide de techniques de lithographies avancées.Le dépôt en bain chimique des nanofils de ZnO est d’abord effectué sur des monocristaux de ZnO de polarité O et Zn préparés par lithographie assistée par faisceau d’électrons. Par cette approche de croissance localisée, un effet significatif de la polarité des nanofils de ZnO est mis en évidence sur le mécanisme de croissance des nanofils, ainsi que sur leurs propriétés électriques et optiques. La possibilité de former des nanofils de ZnO sur des monocristaux de ZnO semipolaires nous a de plus permis d’affiner la compréhension de leurs mécanismes de croissance sur les couches d’amorces polycristallines de ZnO. Par la suite, le dépôt des nanofils de ZnO en bain chimique est développé sur des couches d’amorces polycristallines de ZnO préparés à l’aide de la lithographie assistée par nano-impression. Suivant cette approche, des réseaux de nanofils de ZnO localisés sont formées sur de grandes surfaces, ce qui permet d’envisager leur intégration future au sein de dispositifs fonctionnels.Les nanofils de ZnO sont ensuite combinés avec des coquilles semiconductrices de type p par des méthodes de dépôt chimique en phase liquide ou en phase vapeur afin de fabriquer des hétérostructures cœurs-coquilles originales. Le dépôt de couches successives par adsorption et réaction (SILAR) d’une coquille absorbante de SnS de phase cubique est optimisé sur des nanofils de ZnO recouverts d’une fine couche protectrice de TiO2, ouvrant la voie à la fabrication de cellules solaires à absorbeur extrêmement mince. Enfin, un photo-détecteur UV autoalimenté prometteur, présentant d’excellentes performances en termes de réponse spectrale et de temps de réponse, est réalisé par le dépôt chimique en phase vapeur d’une coquille de CuCrO2 sur les nanofils de ZnO
Over the past decade, the development of novel nanostructured architectures has raised increasing interest within the scientific community in order to meet the demand for low-cost and efficient functional devices composed of abundant and non-toxic materials. A promising path is to use ZnO nanowires grown by chemical bath deposition as building blocks for these next generation functional devices. However, the precise control of the ZnO nanowires structural uniformity and the investigation of their physical properties, particularly in terms of polarity, remain key technological challenges for their efficient integration into functional devices.During this PhD, the chemical bath deposition of ZnO nanowires is combined with electron beam lithography prepared ZnO single crystal substrates of O- and Zn-polarity following the selective area growth approach. The significant effects of polarity on the growth mechanism of ZnO nanowires, as well as on their electrical and optical properties, are highlighted by precisely investigating the resulting well-ordered O- and Zn-polar ZnO nanowire arrays. An alternative nano-imprint lithography technique is subsequently used to grow well-ordered ZnO nanowire arrays over large areas on various polycrystalline ZnO seed layers, thus paving the way for their future integration into devices. We also demonstrate the possibility to form ZnO nanowires by chemical bath deposition on original semipolar ZnO single crystal substrates. These findings allowed a comprehensive understanding of the nucleation and growth mechanisms of ZnO nanowires on polycrystalline ZnO seed layers.In a device perspective, the ZnO nanowires are subsequently combined with p type semiconducting shells by liquid and vapor chemical deposition techniques to form original core-shell heterostructures. The formation of a cubic phase SnS absorbing shell is optimized by the successive ionic layer adsorption and reaction (SILAR) process on ZnO nanowire arrays coated with a thin protective TiO2 shell, which pave the way for their integration into extremely thin absorber solar cells. A self-powered UV photo-detector with fast response and state of the art performances is also achieved by the chemical vapor deposition of a CuCrO2 shell on ZnO nanowire arrays

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13

Reynal, François. "Etude des processus non-linéaires dans les atomes complexes en interaction avec un champ XUV intense et bref". Phd thesis, Université Sciences et Technologies - Bordeaux I, 2012. http://tel.archives-ouvertes.fr/tel-00748138.

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Etude th'eorique de l'interaction entre un atome à deux ou trois électrons actifs et un champ laser de fort éclairement (10^13 à 10^15 W.cm−2) et de durée d'impulsion ultra-brève (femto à attoseconde) dans le domaine spectral XUV. Notre approche est basée sur la résolution de l' équation de Schrödinger dépendante du temps (ESDT). Nous utilisons une méthode spec- trale pour résoudre l'ESDT avec des fonctions d'onde construites sur des B- splines. Nous étudions particulièrement la double ionisation à deux photons (TPDI) de l'hélium dans l'état fondamental ainsi que dans l' état excité 1s2s. Plusieurs modèles sont d'eveloppés pour traiter le cas des impulsions ultra- brèves. Enﬁn nous abordons la TPDI du Lithium, système à trois électrons actifs. Nous comparons la double ionisation à deux photons dans le régime séquentiel pour Li et He(1s2s) ; le régime direct est également abordé

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14

Chan, Matthew Yunho. "Visualization, Characterization, and Analysis of Gold Nanoparticles Fate and Transport in Aqueous Porous Media Environment with Advanced Photonics Technique". Diss., Virginia Tech, 2017. http://hdl.handle.net/10919/85437.

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Increased proliferation of nanotechnology has led to concerns regarding its implication to the water environment. Gold nanoparticles (AuNP) were used as a model nanomaterial to investigate the fate and dynamics of nanoparticles in the complex water environment. A column study was performed to examine the fate and transport of gold nanoparticles with two different coatings in porous media. The resulting data suggested that gold nanoparticles aggregate significantly in the porespace of the column interior, a finding that is not predicted by traditional colloidal filtration theory or Derjaguin-Landau-Verwey-Overbeek (DLVO) theory. Surface-enhanced Raman spectroscopy (SERS) was developed as a new technique to investigate AuNP aggregation in water with varying salt levels. The SERS technique proved valuable as an analytical technique, elucidating information about aggregation as well as AuNP surface interactions with dissolved halides in water. A thorough investigation examining Aunt aggregation with monovalent and divalent salts utilizing SERS, ultraviolet-visible light (UV-Vis) spectroscopy, and dynamic light scattering (DLS) was conducted. Each technique provided data describing different aspects of the dynamic behavior of AuNPs in complex water environments. Results suggest that in addition to attractive and repulsive interactions described by DLVO theory, chemical interactions between the AuNP surface and dissolved halides were also a significant driving force for aggregation and other transformative behaviors of AuNPs in water. The SERS technique developed in this work was shown to be a viable tool to help unveil the vastly complex dynamics of nanomaterial in the water environment.
Ph. D.

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15

Greuters, Jako. "UV laser micromachining of photonics materials". Thesis, University of Hull, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.431044.

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16

Álvarez, Ruiz Jesús. "Photon induced fluorescence studies of molecules using synchrotron radiation". Licentiate thesis, KTH, Physics, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-1567.

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This Licentiate thesis presents research accomplished at theSection of Atomic and Molecular Physics at the Royal Instituteof Technology in Stockholm using photon induced fluorescencespectroscopy (PIFS) during the last two years.

The main results presented are summarized:

- Neutral photodissociation in CO was observed aftersynchrotron photon excitation in the range 19-26 eV bycollecting dispersed fluorescence from excited neutral C atoms.Follow-up ab initio calculations point out CO Rydberg seriesconverging to the CO+ C and D states as precursors.

- The branching ratio between N2 + (B-X)(v=1,v=2) and (v=0,v=1)transitions in the 20-46 eV energy range reveals strongnon-Franck-Condon effects. Ab initio calculations indicate thatthe autoionization of certain superexcited states areresponsible for some of the structures present in the branchingratio curve, confirming the important role of non-Rydbergdoubly excited resonant states (NRDERS) in de-excitationprocesses above the ionization potential.

- Photon induced neutral dissociation processes in NO arereported. Neither Rydberg series nor other molecular states inNO known so far can account for the collected data. From abinitio calculations more information regarding the NO precursorstates and the mechanism behind the observed neutraldissociation were obtained.

- The details of a new experimental set-up for gas phasefluorescence measurements using synchrotron radiation aredescribed. It is able to perform simultaneous measurements ofdispersed and total fluorescence in the visible range. Thefirst results obtained with this set-up are presented,concerning fluorescence after excitation of the N2 molecules inthe N 1s edge.

These four studies conform the set of papers enclosed in theLicentiate thesis.

Finally a pre-study to further apply PIFS to speciespreviously excited by microwave discharge is included as futureplans.

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17

Talla, Kharouna. "Development of MgZnO-grown MOCVD for UV Photonic applications". Thesis, Nelson Mandela Metropolitan University, 2011. http://hdl.handle.net/10948/d1012585.

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MgxZn1-xO has emerged as a material of great technological importance. Having a direct energy band gap that is tunable throughout much of the ultraviolet (UV) region of the spectrum from the near-UV (~370 nm) to the deep-UV (~176 nm), this compound is of interest for a variety of optoelectronic devices operating in this part of the electromagnetic spectrum. MgxZn1-xO offers advantages over the more mature compound semiconductor AlGaN which stem mainly from the unusually high exciton binding energy (60 meV in ZnO). In this study the growth of ZnO and MgxZn1-xO thin films using metal organic chemical vapour deposition (MOCVD) is systematically investigated. The films are mainly grown on c-Al2O3 and Si (100) and characterized using various techniques, such as photoluminescence (PL), x-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and auger electron spectroscopy (AES). The optical and the structural properties are essentially inspected in order to improve their quality. In this thesis the optimisation of ZnO grown using oxygen gas as a new oxidant in our reactor is investigated. The growth temperature and VI/II ratio are varied in order to find optimum parameters giving high quality layers. The effects of Si (100), Si (111), c- and r-sapphire, glass, GaAs and ZnO substrates on the optical, structural and morphological properties of ZnO thin films grown with tert-butanol (TBOH) is examined. Similar morphologies are observed for all substrates, with the films comprising hexagonal columns having cone shaped ends. The photoluminescence spectra are similar, but the various transitions have different relative intensities. It is clear that the different substrates influence neither the orientation of the films, nor the surface morphology, significantly. The photoluminescence hints at larger stacking fault densities in films grown on silicon and glass, however, as evidenced by stronger basal plane stacking fault-related luminescence at ~3.319 eV in the relevant low temperature photoluminescence spectra. The morphology changes with Mg incorporation, from hexagonal columnar structures to cubic faceted columns. From PL, the full with at half maximum is found to gradually increase with Mg content due to alloy broadening. The deep level emission (DLE) is observed to shift with Mg content. By changing the Mg content, the band gap of MgxZn1-xO film is tuned by ~450 meV, which provides an excellent opportunity for band gap engineering for optoelectronic applications. The c-lattice constant of ZnO (5.205 Å) decreases by only 0.6% when the Mg content reaches x=0.39. The introduction of Mg into ZnO is shown to increase the relative PL intensity of stacking fault-related transitions (at 3.314 eV for ZnO). This becomes the dominant near band edge emission. Using TEM a thin Mg rich layer is observed at the interface between the film and the Si or Al2O3. Temperature dependent PL measurements on layers with low Mg concentration (x=0.05 and 0.1) show that the main bound exciton peak exhibits an “s-shaped” temperature dependence, characteristic of localization in a disordered alloy. The origin of the PL line broadening of MgxZn1-xO (x≤0.04) is also analyzed with respect to alloy broadening, taking into account a random cation distribution and alloy clustering. The influence of various MOCVD growth parameters such as growth temperature and VI/II ratio is studied. Varying the temperature from 280 ˚C to 580 ˚C reveals strong morphological changes and optical degradation of the films. Low (<280 ˚C) and high (>580 ˚C) growth temperatures reduce the Mg incorporation. High VI/II ratios also decrease the Mg incorporation, as evidenced by the red-shift of the donor bound exciton (D°X) line. This is ascribed to a stronger premature reaction between (MeCp)2Mg and the oxidant or a preferential heterogeneous interaction between the Mg and oxygen species on the growth front. For both oxidizing agents (O2 and TBOH), the growth at 420 ˚C and a VI-II ratio of 60 on c-Al2O3 gave optimal quality layers in terms of their optical and structural quality. A comparison of films grown using TBOH and O2 gas as oxidizing agent shows no major difference in terms of Mg incorporation. The effect of annealing, the inclusion of a buffer layer and the influence of growth rate on the properties MgxZn1-xO thin films are also reported.

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18

Kahn, Kevin. "Two-dimensional wide band gap semiconductors for deep UV photonics". Thesis, Imperial College London, 2016. http://hdl.handle.net/10044/1/48013.

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Light emitters and detectors in the deep ultraviolet range (DUV) are of great current interest, with applications in water purification, solar-blind photodetectors and communication, biohazard detection, and phosphor-assisted white light emitters. However, DUV optoelectronics based on solid-state heterostructures suffer from low internal and external quantum efficiencies, due to issues relating to their fundamental material properties. These limitations motivate the exploration of new classes of materials for these applications. The recent emergence of two-dimensional (2D) materials has opened up new possibilities in this area, however 2D materials also bring new experimental challenges: particularly the deposition and characterisation of atomic layers, as well as scientific challenges, especially understanding how interactions between the 2D layer and the substrates and/or the environment may affect the properties of the 2D layer. In this thesis, the optical properties of promising materials for deep UV photonics are assessed using a combination of techniques, and the mathematical links between the resulting data are demonstrated. The first part of this work discusses the optical and structural properties of gallium nitride and its alloys, which are the foundation of current optoelectronics, and addresses the optical processes of freestanding and supported 2D hexagonal boron nitride (h-BN) as a potential candidate for high-efficiency deep UV optoelectronic devices. The objectives are to (i) confirm the validity of the models on well-known materials, (ii) determine whether h-BN is a good candidate for deep UV optoelectronics and (iii) whether and how interactions between 2D h-BN with substrates must be taken into consideration. The second part discusses the optical properties of barium zirconate titanate with changes in composition and dimensionality. The objectives are (i) to apply models developed for the nitrides to extract the bulk properties of these oxides, and (ii) to determine whether they are good candidates for deep UV optoelectronics in their 2D form.

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19

Li, Tong. "Influence of stress on photo-degradation of polymers". Thesis, University of Newcastle Upon Tyne, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.283648.

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20

Sedhain, Ashok. "Optical properties of ALN and deep UV photonic structures studied by photoluminescence". Diss., Kansas State University, 2011. http://hdl.handle.net/2097/8522.

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Doctor of Philosophy
Department of Physics
Jingyu Lin
Time-resolved deep ultraviolet (DUV) Photoluminescence (PL) spectroscopy system has been employed to systematically monitor crystalline quality, identify the defects and impurities, and investigate the light emission mechanism in III-nitride semiconducting materials and photonic structures. A time correlated single photon counting system and streak camera with corresponding time resolutions of 20 and 2 ps, respectively, were utilized to study the carrier excitation and recombination dynamics. A closed cycle He-flow cryogenic system was employed for temperature dependent measurements. This system is able to handle sample temperatures in a wide range (from 10 to 900 K). Structural, electrical, and morphological properties of the material were monitored by x-ray diffraction (XRD), Hall-effect measurement, and atomic force microscopy (AFM), respectively. Most of the samples studied here were synthesized in our laboratory by metal organic chemical vapor deposition (MOCVD). Some samples were bulk AlN synthesized by our collaborators, which were also employed as substrates for homoepilayer growth. High quality AlN epilayers with (0002) XRD linewidth as narrow as 50 arcsec and screw type dislocation density as low as 5x10[superscript]6 cm[superscript]-2 were grown on sapphire substrates. Free exciton transitions related to all valence bands (A, B, and C) were observed in AlN directly by PL, which allowed the evaluation of crystal field (Δ[subscript]CF) and spin-orbit (Δ[subscript]SO) splitting parameters exerimentally. Large negative Δ[subscript]CF and, consequently, the difficulties of light extraction from AlN and Al-rich AlGaN based emitters due to their unique optical polarization properties have been further confirmed with these new experimental data. Due to the ionic nature of III-nitrides, exciton-LO phonon Frohlich interaction is strong in these materials, which is manifested by the appearance of phonon replicas accompanying the excitonic emission lines in their PL spectra. The strength of the exciton-phonon interactions in AlN has been investigated by measuring the Huang-Rhys factor. It compares the intensity of the zero phonon (exciton emission) line relative to its phonon replica. AlN bulk single crystals, being promising native substrate for growing nitride based high quality device structures with much lower dislocation densities (<10[superscript]4 cm[superscript]-2), are also expected to be transparent in visible to UV region. However, available bulk AlN crystals always appear with an undesirable yellow or dark color. The mechanism of such undesired coloration has been investigated. MOCVD was utilized to deposit ~0.5 μm thick AlN layer on top of bulk crystal. The band gap of strain free AlN homoepilayers was 6.100 eV, which is ~30 meV lower compared to hetero-epitaxial layers on sapphire possessing compressive strain. Impurity incorporation was much lower in non-polar m-plane growth mode and the detected PL signal at 10 K was about an order of magnitude higher from a-plane homo-epilayers compared to that from polar c-plane epilayers. The feasibility of using Be as an alternate p-type dopant in AlN has been studied. Preliminary studies indicate that the Be acceptor level in AlN is ~330 meV, which is about 200 meV shallower than the Mg level in AlN. Understanding the optical and electronic properties of native point defects is the key to achieving good quality material and improving overall device performance. A more complete picture of optical transitions in AlN and GaN has been reported, which supplements the understanding of impurity transitions in AlGaN alloys described in previous reports.

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21

Beaton, Christa. "Photo-protection mechanisms of UV stabilizers on milled wood lignin". Thesis, McGill University, 2000. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=32897.

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This study focuses on understanding the photochemical reactions that occur between ultraviolet stabilizers and lignin during irradiation in order to further comprehend the photo-protection mechanisms of these stabilizers during brightness reversion. The stabilizers chosen for study included a variety of ultraviolet absorbers (UVAs), in addition to a hindered nitroxide free radical (4-hydroxy-TEMPO). Irradiated samples were analyzed using quantitative 31P NMR, in addition to a technique known as 'Derivatization Followed by Reductive Cleavage'.
Benzophenone-based UVAs have been shown to be actively involved in photochemical reactions with lignin during irradiation, while benzotriazole-based UVAs are comparatively photostable under identical irradiation techniques. All additive combinations were found to inhibit the formation of carboxylic acids and photochemical condensation reactions in lignin; however, the joint application of 2,4-DHB and 4-hydroxy-TEMPO demonstrated synergistic inhibition of these reactions.
All additive combinations were shown to impede the formation of catechol structures and to retard the cleavage of lignin beta-arylether groups during irradiation. The combined use of Tinuvin 1130 and 4-hydroxy-TEMPO provided the most efficient inhibition of these reactions. These results provide insight into the excellent photoyellowing inhibition provided by this additive combination when applied onto mechanical pulps.

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22

Mahjoub, Ahmed. "PROCESSUS ÉNANTIOSÉLÉCTIFS DANS DES COMPLEXES À LIAISONS HYDROGÈNE". Phd thesis, Université Paris Sud - Paris XI, 2009. http://tel.archives-ouvertes.fr/tel-00459590.

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La chiralité joue un rôle très important dans la chimie du vivant. En effet, la plupart des molécules biologiques sont chirales. La discrimination chirale met en jeu des interactions spécifiques à travers la formation de paires de contact diastéréoisomères en phase condensée. Le sujet de ce travail de thèse est d'étudier ces interactions énantiosélectives à l'échelle moléculaire, en étudiant en phase gazeuse des complexes chiraux formés en jet supersonique. Le principe de l'expérience repose sur la complexation d'une forme énantiomère pure d'un chromophore avec les deux énantiomères d'un solvant chiral. Les diastéréoisomères ainsi formés possèdent deux structures différentes. Cette différence de structure se manifeste par deux signatures spectroscopiques différentes. La combinaison de la spectroscopie laser (électronique et vibrationnelle) et des calculs théoriques permet d'étudier les interactions responsables de la discrimination chirale. Ce travail de thèse consiste en l'étude de la discrimination chirale de deux énantiomères du Méthyl-lactate, en utilisant trois chromophores chiraux différents : le (±)-cis-1-amino-indan-2-ol ; le Méthyl-mandélate et le S(-) 1,2,3,4-tetrahydro-3-isoquinoléine méthanol. Ces trois systèmes nous ont permis d'étudier le rôle dans la discrimination chirale de trois facteurs importants qui sont : la formation des multiples liaisons hydrogène, les forces dispersives et l'isomérie conformationnelle.

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23

Walden, Sarah L. "Nonlinear optical properties of ZnO and ZnO-Au composite nanostructures for nanoscale UV emission". Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/114126/9/Sarah_Walden_Thesis.pdf.

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This thesis investigates the nonlinear optical properties of ZnO and ZnO-Au composite nanostructures. For applications such as photodynamic therapy, it is desirable to use nanoparticles to generate localised UV emission while illuminating them with visible or infrared light. This is possible using nonlinear optical processes such as two photon absorption. Nonlinear optical processes however, are extremely weak, so this work investigates the potential of increasing the efficiency of two photon absorption in ZnO nanoparticles by coupling them to metal nanoparticles. Using new experimental methods, the two photon absorption and resulting UV emission from the nanoparticles are measured.

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24

Nebioglu, Ahmet. "NETWORK FORMATION AND THERMO-MECHANICAL PROPERTIES OF PHOTO-CURING HYBRID COATINGS". University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1145166725.

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25

Orzekowsky-Schroeder, Regina Bernadette [Verfasser]. "Two-photon microscopy and UV laser nanosurgery of murine small intestine in vivo / Regina Bernadette Orzekowsky-Schroeder". Lübeck : Zentrale Hochschulbibliothek Lübeck, 2014. http://d-nb.info/1046713248/34.

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26

Shim, Dong Eun. "UV nanoimprinting using a polymer mold and its application to 3-D photonic crystal fabrication". Diss., Restricted to subscribing institutions, 2009. http://proquest.umi.com/pqdweb?did=1970611211&sid=54&Fmt=2&clientId=1564&RQT=309&VName=PQD.

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27

Bakry, A. H. A. "Tunable UV laser-induced photo-fragmentation of selected alkali halides in molecular beams". Thesis, Swansea University, 1994. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.636022.

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This thesis is concerned with two sensitive and selective methods for detecting low concentrations of molecules and reactive atoms. The methods are described in detail, and in particular emphasis is given to the design, construction and operation of systems to implement Resonance Ionization Spectroscopy (RIS) and Laser Induced Fluorescence (LIF) for detecting photodissociated alkali atoms and alkali halide molecules. Alkali halide molecules are often treated as model cases by both theoreticians and experimenters because of their unique properties which distinguish them from other molecules such as the avoided crossing of their lowest two excited potential curves with the ground state potential curve. Molecular beams of sodium iodide, lithium iodide, and caesium iodide, representative for alkali halides, were used as a rich source to study the dissociation and the detection of these molecules. In the RIS experiments, a pulsed tunable UV laser was used to photodissociate NaI, LiI and CsI. Na, Li, and Cs atoms were detected by two-step RIS. This is the first time that RIS on alkali halides has been performed in a molecular beam. The photodissociation of NaI was studied as a function of the UV-wavelength. The result has shown that the dissociation cross section for NaI at the first UV maximum (325nm) is of the same magnitude as the absorption cross section determined by Davidovits et al, 1967. A variety of different experiments were conducted to establish the sensitivity of the technique, and detection limits of 5x10⁶ Na-atoms cm^-3, 10^6 Li-atoms cm^-3 and 3x10⁶ Cs-atoms cm^-3 were measured. To detect NaI molecules, a molecular beam of NaI was used to demonstrate the technique of LIF. However, no spectrally resolved molecular LIF was observed; explanations for the failure are provided, and in this context factors that affect the detection sensitivity of RIS and LIF are discussed.

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28

Khadeeva, Liya. "Photo-isomerization and photo-induced NO release in ruthenium nitrosyl compounds". Thesis, Rennes 1, 2016. http://www.theses.fr/2016REN1S067/document.

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Ce travail de thèse est centré sur l'étude expérimentale de deux types de transformations photo-induites observées dans différents complexes métalliques (Fe, Ru, ...) à ligand nitrosyle: (i) la photo-isomérisation au cours de laquelle le ligand NO passe d'un état lié par l'azote (M-NO, état stable GS) à un état lié par l'oxygène (M-ON, état métastable MSI). C'est un processus réversible et un second état métastable, 'side-on' MSII est observable au cours du processus inverse, MSI --> 'side-on' MSII --> GS; (ii) la libération photo-induite du radical NO°. La photo-isomérisation a été étudiée dans le système [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O (sur monocristal) par la diffraction des RX, l'absorption visible statique et l'absorption UV-Vis résolue en temps. Nous avons pu mettre en évidence un processus d'absorption de photons (473 nm) en deux étapes, suivre la dynamique des transformations directes et inverses par l'évolution des paramètres de maille et des l'absorption optique visible, caractériser structuralement l'état 'side-on' MSII. La nature de l'état intermédiaire, MSII, lors du processus direct semble être différente de l'état 'side-on' mais la très faible population de cet intermédiaire n'a pas permis de trancher définitivement. Le rôle de la molécule d'eau dans la maille du complexe [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O a été testé par diffraction des RX sur les échantillons hydratées, déshydratées et réhydratées. L'effet de déshydratation sur l'évolution des paramètres de maille et sur la génération d'espèces MSII au cours de la photo-commutation inverse, MSI --> MSII --> GS, est présenté. La libération photo-induite du radical NO° a été étudiée dans une solution d'acétonitrile du complexe trans-(Cl,Cl)[Ru^{II}(FT)Cl_2(NO)]PF_6 par spectroscopies d'absorption UV-Vis et Mi-IR, statiques et résolues en temps. En observant la dynamique ultra-rapide de la photo-transformation, nous avons mis en évidence un processus d'absorption de photons (406 nm) en deux étapes. La nature de l'état intermédiaire est discuté par rapport à de récents calculs théoriques et au processus de photo-isomérisation
This Ph. D. thesis is focused on the experimental study of two photo-induced processes observed in various [ML_5NO] complexes, where M=Fe, Ru, ..., L=CN, Cl, ... : (i) photo-isomerization, where the system goes from N-bound state (M-NO, stable GS state) to O-bound state (M-ON, metastable MSI state) and a second metastable state, 'side-on' MSII is observed during the inverse photo-transformation, MSI --> 'side-on' MSII --> GS; (ii) photo-induced release of NO° radical. The photo-isomerization is investigated in single crystals of [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O compound by means of X-Ray diffraction, steady state visible and time-resolved UV-visible absorption spectroscopies. During these experiments we observed the evidence of a two-step photon absorption process (473 nm), we followed the dynamics of direct and inverse photo-switching by the evolution of lattice parameters and absorption in the visible range and we caracterised the structure of 'side-on' MSII state. The nature of MSII in the direct photo-switching, GS --> MSI, seems to be different from the 'side-on' configuration, however, we do not have a direct access to this state due to its low population. The role of water molecule in the unit cell of [Ru(py)_4Cl(NO)](PF_6)_2.1/2H_2O complex was tested by X-Ray diffraction studies on hydrated, dehydrated and rehydrated samples. The effect of sample dehydration on the unit cell parameters evolution and MSII species generation during the MSI --> MSII --> GS inverse photo-switching is presented. The photo-induced NO° release in trans-(Cl,Cl)[Ru^{II}(FT)Cl_2(NO)]PF_6 system in acetonitrile solution is studied by the UV-visible and mid-IR absorption spectroscopies, both steady state and time-resolved. By observing the ultra-fast dynamics of photo-transformation we evidenced a two-step photon absorption process (406 nm). The nature of intermediate state is discussed within the recent theoretical calculations and the photo-isomerization process

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29

Araujo, Leandro Goulart de. "Photo-oxidative degradation of bisphenol A by H2O2/UV: process study and kinetic modelling". Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/3/3137/tde-17072018-111837/.

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Bisphenol A (BPA) is widely used in the production of plastics, epoxy resins and polycarbonates. It is a toxic, endocrine disruptor compound. Different studies have shown the presence of BPA in several environmental systems, classifying it as a worldwide persistent pollutant which may act synergistically with other pollutants. In this context, advanced oxidation processes (AOP) have received great attention due to their ability to degrade pollutants with such characteristics, through their transformation into less hazardous compounds or even their mineralization. Although there are investigations on the use of AOPs for BPA degradation, systematic studies on the effects of process variables, coupled with the statistical interpretation of the results are virtually non-existent. Furthermore, to the best of our knowledge, a rigorous kinetic model has not yet been proposed for the degradation of this pollutant by the H2O2/UV process. The objective of this work was to evaluate BPA degradation by the H2O2/UV process, investigating the effects of the initial H2O2 concentration and the specific rate of photons emission (EP,0) by means of a Doehlert experimental design, combined with the response surface methodology. The experiments were performed in a photochemical tubular reactor equipped with a 254-nm UV lamp, for [H2O2]0 and EP,0 in the ranges 1.6-9.6 mmol L-1 and 0.87 × 1018-3.6 × 1018 photons L-1 s-1, respectively. Total BPA degradation was achieved after 60 min of irradiation in all experiments. The best conditions were [H2O2]0 = 7.6 mmol L-1 and EP,0 = 3.6 × 1018 photons L-1 s-1, for which the best performance was obtained regarding the BPA degradation rate, BPA degradation after 15 min, and the second highest TOC removal after 180 min. However, in most experiments less than 75% TOC removal was observed, with 95% mineralization obtained only for the superior [H2O2]0 and EP,0. A mathematical model was developed, considering the reactor characteristics and the radiation field, based on the line source with parallel emission (LSPP) approach, in combination with the radiative transfer equation (RTE), mass balances, and a detailed kinetic model of the H2O2/UV process. The steady-state approximation was applied for all radical species. In the estimation of unknown kinetic constants, the non-linear least squares method was employed. The model was able to satisfactorily fit experimental BPA and H2O2 concentrations as a function of time. This work shows that the H2O2/UV process is a good alternative for BPA removal from aqueous streams, with total degradation of the target compound and adequate percent mineralization under optimal operating conditions. Such conditions may serve as first guidelines for pilot-plant and industrial processes operation. In addition, simulations using the proposed kinetic model may provide useful information for the design and scale-up of pre- or post-treatment of effluents containing this pollutant.
O bisfenol A (BPA) é amplamente utilizado na fabricação de plásticos, resinas epóxi e policarbonatos. Trata-se de um composto tóxico e um desregulador endócrino. Diferentes estudos evidenciam a presença do BPA em diversos compartimentos ambientais em todo planeta, identificando-o como um poluente persistente e resistente à degradação biológica, que apresenta efeitos sinergéticos com outros poluentes. Nesse contexto, os processos oxidativos avançados (POA) têm recebido atenção devido a sua capacidade em degradar poluentes com tais características, transformando-os em compostos menos perigosos ou até mesmo mineralizando-os totalmente. Apesar de haver trabalhos na literatura acerca da utilização de POA para degradação de BPA, estudos sistemáticos dos efeitos de variáveis de processo junto com a interpretação estatística dos resultados são virtualmente inexistentes. Além disso, até onde se sabe um modelo cinético rigoroso ainda não foi proposto para a degradação desse poluente por meio do processo H2O2/UV. Este trabalho teve por objetivo avaliar a degradação do BPA pelo processo H2O2/UV, investigando os efeitos da concentração inicial de H2O2 e da taxa específica de emissão de fótons (EP,0) por meio de um projeto experimental Doehlert, combinado com a análise de superfície de resposta. Os experimentos foram realizados em um reator tubular fotoquímico equipado com uma lâmpada UV de 254 nm, para [H2O2]0 e EP,0 entre 1,6-9,6 mmol L-1 e 0,87 × 1018 - 3,6 × 1018 fótons L-1 s-1, respectivamente. Todos os experimentos sob H2O2/UV resultaram em total degradação do BPA após 60 min de irradiação. Nesse caso, as melhores condições foram [H2O2]0 = 7,6 mmol L-1 e EP,0 = 3,6 × 1018 fótons L-1 s-1, para as quais se obteve o melhor desempenho quanto à taxa de degradação de BPA e à remoção após 15 min, e a segunda maior remoção de COT após 180 min. Entretanto, na maioria dos experimentos menos de 75% de remoção de COT foram observados, com 95% de mineralização obtida apenas para os maiores [H2O2]0 e EP,0. Elaborou-se um modelo matemático que considera as características do reator utilizado e o campo de radiação, baseado no modelo de fonte linear de emissão em planos paralelos (LSPP), combinado à equação de transferência radiativa (RTE), aos balanços materiais e a um modelo cinético detalhado do processo H2O2/UV. Foi empregada a aproximação de estado estacionário para todas as espécies radicalares. Na estimativa das constantes cinéticas desconhecidas, utilizou-se o método de mínimos quadrados não linear. Esse modelo foi capaz de ajustar satisfatoriamente as concentrações experimentais de BPA e de H2O2 em função do tempo. Este trabalho mostra que o processo H2O2/UV constitui uma alternativa conveniente para a degradação de BPA em matrizes aquosas, com total degradação do composto alvo e porcentagem de mineralização adequada nas condições ótimas de operação. Tais condições podem servir como diretrizes iniciais de processamento em escalas piloto e industrial. Por sua vez, simulações empregando o modelo matemático proposto permitem gerar informações úteis para projeto e aumento de escala de processos de pré- ou pós-tratamento de efluentes contendo esse poluente.

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30

Belbakra, Zakaria. "Investigation and characterization of polythiol (meth)acrylate based resins for UV-curing applications". Thesis, Mulhouse, 2013. http://www.theses.fr/2013MULH6193.

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L’objectif de cette thèse est de développer des matériaux polymérisés par rayonnement ultra-violet possédant une bonne balance des propriétés thermomécaniques entre résistance à la température, rigidité (strength) et résistance à l’impact. Une direction vers cet objectif est l’utilisation de résines (meth)acrylate modifiées avec des thiols polyfonctionnels. Cependant, les thiol-ene en général sont sujets à un problème de polymérisation prématurée incontrôlée même à l’abri de la lumière. Ce problème doit être traité puisque celui-ci conditionne le succès des thiol-ene dans le domaine des photopolymères. La première partie de cette thèse concerne l’élaboration de résine (meth)acrylate modifiée par l’incorporation d’un polythiol, le pentaerythritol tetrakismercaptopropionate (PETMP), à différents ratio. Les propriétés thermomécaniques et photochimiques de ces résines sont à l’étude. La seconde partie traite du problème de polymérisation prématurée incontrôlée des thiol-ene. Une étude de stabilité thermique aboutissant à des résultats très encourageant est proposée. Finalement, la dernière partie porte sur la caractérisation des réseaux photo-réticulés par pyrolyse-GC/MS. La compréhension de la constitution des réseaux tridimensionnels devraient apportés des avancées dans l’élaboration de nouveaux matériaux. Une nouvelle méthode de caractérisation utilisant la pyrolyse-GC/MS directe à multi-étapes est développée. Enfin, des résultats sur l’application de la méthode sur des matériaux à base de (meth)acrylate difonctionnel photopolymérisés ainsi qu’une tentative de caractérisation de matériaux à base de polythiol/(meth)acrylates photopolymérisés sont reportés puis discutés
This thesis fall within an approach aiming to develop UV-processed materials having a good thermo-mechanical properties balance between strength, temperature resistance and impact resistance. A direction toward this objective is the use of photocurable (meth)acrylate resins modified with polyfunctional thiols. Indeed, thiol-ene chemistry is known to have poor sensitivity toward oxygen inhibition, to improve the dimensional stability and toughness properties of photocured materials. However, thiol-ene resins are subjected to premature uncontrolled dark polymerization, an issue that has to be solved for their success in the photopolymers area. The first part of this work is focused on the thermo-mechanical and the photopolymerization properties investigation of a pentaerythritol tetrakismercaptopropionate (PETMP) modified (meth)acrylate based resin by looking at different ratio of polythiol/(meth)acrylate. The second part is dedicated to the understanding of the thermal instability of such systems and to the solving of this issue. Finally, a special interest is brought to the characterization of photopolymeric networks by pyrolysis-GC/MS. The lake of deep understanding and view about how the cured networks are really constituted due to the difficulty to analyze insoluble cured polymers, prevents improvements in the formulation of high performance materials. Further information on cured networks constitution could bring useful information for the elaboration of new materials. A new characterization method based on direct multi-step pyrolysis-GC/MS is developed and an attempt on the characterization of polythiol (meth)acrylate material by Py-GC/MS is reported and discussed

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31

Guzel, Aylin. "Photo-oxidative Degradation Of Abs Copolymer". Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/12610895/index.pdf.

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ABSTRACT PHOTO-OXIDATIVE DEGRADATION OF ABS COPOLYMER Gü
zel, Aylin M.S., Department of Polymer Science and Technology Supervisor: Prof. Dr. Teoman Tinç
er Co-Supervisor: Prof. Dr. Cevdet Kaynak September 2009, 55 pages Acrylonitrile-butadiene-styrene (ABS) polymer is one of the most popular copolymer having an elastomeric butadiene phase dispersed in rigid amorphous styrene and semi-crystalline acrylonitrile. Due to double bonds in the polybutadiene phase, ABS copolymers are very sensitive to photo-oxidative degradation. Photo-oxidation of butadiene rubber phase results in the formation of chromorphores and these chromorphores act as initiators in photo-oxidative degradation and after a while ABS starts yellowing. In this work, the relationship between the UV light and the yellowing of ABS samples was also investigated with respect to time. In this study, pure, light stabilized and commercial ABS samples were aged under UV light. As the UV light intensity increased from 800 to 2800 &
#61549
W/cm2, yellowing of the samples were increased for pure ABS. This increase in yellowing of the samples was about 27 times higher compared to lower energy. In this study, UV stabilizers IRGANOX 1076 (sterically hindered phenolic antioxidant), IRGAFOS 168 (hydrolycally stable phosphite stabilizer) and TINUVIN P (hydroxyphenol benzotriazole) were used alone or in combination with each other. Pure ABS samples, commercial ABS samples and UV stabilized ABS samples were aged under the same UV light. UV aging degradation was followed by measuring the yellowness of the samples at certain time intervals. Yellowness of the samples was followed by using Coloreye XTH Spectrometer. Degradation in ABS, however, was followed by using FTIR with an increase in the peak area of carbonyl groups in the ABS matrix. Both color analysis and the FTIR analysis showed that combination of the IRGANOX 1076 and IRGAFOS 168 stabilizers gave the best stabilization. This revealed that combination of phenol and phosphate containing stabilizer is the most useful combination to prevent photo-oxidative degradation of ABS copolymer. Additionally, vegetable oil was applied to the surface of a new set of ABS samples and these samples were aged for 700 h. Yellowing tendency of these samples was compared with the yellowing tendency of ABS samples that are directly aged for 500 h. It was clearly observed that samples with oil smeared had more resistance to UV radiation with respect to others. This shows that oil acts protective layer to the UV light and oxygen and slow down the photo-oxidative degradation. Lastly some commercial ABS samples were compared to each other with respect to their yellowing tendency. Commercial ABS samples coded as K, L, A, B, C and D were aged under UV light at about 500 h. Sample A showed the best resistance against the yellowing among the other commercial ABS samples.

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32

Espid, Ehsan. "UV-LED photo-activated metal oxide semiconductors for gas sensing application : fabrication and performance evaluation". Thesis, University of British Columbia, 2015. http://hdl.handle.net/2429/55057.

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The idea of functionalizing chemical gas sensors at room temperature as well as making them smaller and more efficient has initiated important progresses in the last few years among scientists worldwide. Ultraviolet Light Emitting Diode (UV-LED) technology has shown its capability to fulfill the gap between laboratorial and industrial production of room temperature gas sensors. In this research, a review on the performances, preparation techniques, and most influential factors of several photo-activated metal oxide semiconductor gas sensors under UV-LED irradiation was conducted. Further, a comparative study on the development of sensitive gas sensors using ZnO and In₂O₃ semiconductors for NO₂ gas detection was performed. The results indicated that the sensitivity of In₂O₃ to NO₂ is approximately two times greater than that of ZnO for all the experimented irradiances. The highest sensitivities with complete recovery for the ZnO and In₂O₃ based sensors were obtained at 1.2 mW/cm² and 2.8 mW/cm² irradiances, respectively. In general, the In₂O₃ sensors required a higher UV irradiance compared to ZnO sensors, to prevent permanent adsorption of target gas molecules on the surface. To further increase the sensitivity and reduce the response time, n-type semiconductor oxides of ZnO and In₂O₃ were coupled using co-precipitation method, to obtain nano-crystalline composite sensing materials. The composition, structure and optical properties of the prepared samples were characterized by EDS, XRD, SEM, XPS and UV-Vis analyses. The composite materials showed higher sensitivity towards NO₂ with a 200s decrease in response time compared to pristine samples. A favorable composition ratio of [In]:[Zn] was determined to be 1:2 for the nano-composite particles, with 2.21 sensitivity as the highest sensing performance to 5 ppm NO₂. The high sensitivity of this combination is attributed to the morphology and composite porous structure, as well as lower band-gap of the target composite. The irradiance of 1.7 mW/cm² provided the highest sensitivity, short response time and a complete recovery for the ZnO/In₂O₃ composite structures, within the experimented range. It’s believed that, ZnO favors the flow of charge carriers and increases the surface area, while In₂O₃ acts as active light absorption centers and enhances chemisorption ability in the composite.
Applied Science, Faculty of
Chemical and Biological Engineering, Department of
Graduate

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33

Pradana, Arfat [Verfasser]. "UV nanoimprint lithography for fabrication of 1-D photonic crystal slabs and their application in OLEDs / Arfat Pradana". Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/1058586599/34.

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34

Simões, Anderson Sávio de Medeiros. "Estudo da degradação de microcontaminantes em efluentes por radiação ultravioleta e processo oxidativo foto Fenton". Universidade Federal da Paraíba, 2013. http://tede.biblioteca.ufpb.br:8080/handle/tede/7099.

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Made available in DSpace on 2015-05-14T13:21:23Z (GMT). No. of bitstreams: 1 ArquivoTotalAnderson.pdf: 4410851 bytes, checksum: e572d62f98ca693cf1cab482619214a6 (MD5) Previous issue date: 2013-04-04
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
The occurrence and identification of organic microcontaminants has attracted the interest of many researchers for the development and improvement in processes for the removal of these contaminants from effluents. In general, degradation of microcontaminants by conventional methods is very difficult, because of the low concentrations that they are found. Thus, the photo Fenton process and Ultraviolet Radiation (UV) has been a promising alternative for the removal of such water contamination. This study aims to perform the investigation of degradation, in effluent, of atrazine (ATZ) using the photo Fenton process and degradation of the pharmaceuticals propranolol (PRO) and metronidazole (MET) using UV radiation. In the ATZ (0,1 mg L-1) degradation study, UV-A photo Fenton process was used (H2O2= 5,0 mg L-1 e Fe2+ = 5,0 mg L-1), achieving a microcontaminant degradation of about 62 %, and the UV-C photo-Fenton process (H2O2 = 5,0 mg L-1 e Fe2+ = 5,0 mg L-1), reached about 98% of ATZ degradation. The analysis of organic matter removal during the photo Fenton treatment showed no significant change in the studied parameters. In the UV photolysis degradation study of the pharmaceuticals solutions (100 mg L-1) a degradation of 35% (PRO) and 50% (MET) was obtained after 8 hours of treatment, whereas using solar radiation a degradation of 36% (PRO) and 16% (MET) were obtained. From the kinetic constants and half-lives calculated, it was found that direct photolysis using solar radiation was so effective as the system using UV-C radiation to promote photodegradation of PRO, and for the MET results showed that the pharmaceutical has a higher degradation rate when the UV-C radiation was employed.
O surgimento e a identificação dos microcontaminantes orgânicos têm atraído o interesse de inúmeros pesquisadores para o desenvolvimento e melhoria nos processos de degradação desses contaminantes de efluentes. Em geral, a degradação de microcontaminantes por processos convencionais é bastante dificultada, em razão das baixas concentrações que eles são encontrados. Desta forma, o processo foto Fenton e a Radiação Ultravioleta (UV) têm sido uma alternativa promissora na eliminação deste tipo de contaminação da água. O presente trabalho teve como objetivo realizar o estudo da degradação, em efluentes, da atrazina (ATZ) utilizando o processo foto Fenton e da degradação dos fármacos propranolol (PRO) e metronidazol (MET) utilizando radiação UV. No estudo da degradação da ATZ (0,1 mg L-1) foi utilizado o processo foto Fenton UV-A (H2O2 = 5,0 mg L-1 e Fe2+ = 5,0 mg L-1), sendo obtida uma degradação do microcontaminante de cerca de 62%, e o processo foto Fenton UV-C (H2O2 = 5,0 mg L-1 e Fe2+ = 1,0 mg L-1), obtendo 98 % de degradação da ATZ. A análise da remoção da matéria orgânica durante o tratamento foto Fenton mostrou que não houve alteração significativa nos parâmetros estudados. No estudo da degradação por fotólise UV das soluções dos fármacos (100 mg L-1), foram obtidas taxas de degradação de 35% (PRO) e 50% (MET), após 8 horas de tratamento, enquanto que no processo utilizando a luz solar foram obtidos taxas de degradação de 36% (PRO) e 16% (MET). A partir das contantes cinéticas e das meias-vidas obtidas, foi verificado que a fotólise direta utilizando a radiação solar é tão eficaz quanto o sistema utilizando radiação UV-C para promover a fotodegradação do PRO, e para o MET, os resultados mostraram que o fármaco apresenta uma maior taxa de degradação quando a radiação UV-C foi utilizada. Palavras-chave: Microcontaminantes; Radiação UV; foto Fenton O surgimento e a identificação dos microcontaminantes orgânicos têm atraídoo interesse de inúmeros pesquisadores para o desenvolvimento e melhoria nosprocessos de degradação desses contaminantes de efluentes. Em geral, adegradação de microcontaminantes por processos convencionais é bastantedificultada, em razão das baixas concentrações que eles são encontrados. Destaforma, o processo foto Fenton e a Radiação Ultravioleta (UV) têm sido umaalternativa promissora na eliminação deste tipo de contaminação da água. Opresente trabalho teve como objetivo realizar o estudo da degradação, em efluentes,da atrazina (ATZ) utilizando o processo foto Fenton e da degradação dos fármacospropranolol (PRO) e metronidazol (MET) utilizando radiação UV. No estudo dadegradação da ATZ (0,1 mg L-1) foi utilizado o processo foto Fenton UV-A (H2O2 =5,0 mg L-1 e Fe2+ = 5,0 mg L-1), sendo obtida uma degradação do microcontaminantede cerca de 62%, e o processo foto Fenton UV-C (H2O2 = 5,0 mg L-1 e Fe2+ = 1,0 mgL-1), obtendo 98 % de degradação da ATZ. A análise da remoção da matériaorgânica durante o tratamento foto Fenton mostrou que não houve alteraçãosignificativa nos parâmetros estudados. No estudo da degradação por fotólise UVdas soluções dos fármacos (100 mg L-1), foram obtidas taxas de degradação de 35%(PRO) e 50% (MET), após 8 horas de tratamento, enquanto que no processoutilizando a luz solar foram obtidos taxas de degradação de 36% (PRO) e 16%(MET). A partir das contantes cinéticas e das meias-vidas obtidas, foi verificado quea fotólise direta utilizando a radiação solar é tão eficaz quanto o sistema utilizandoradiação UV-C para promover a fotodegradação do PRO, e para o MET, osresultados mostraram que o fármaco apresenta uma maior taxa de degradaçãoquando a radiação UV-C foi utilizada.

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35

Stiefel, Constanze [Verfasser] y Wolfgang [Akademischer Betreuer] Schwack. "Investigations on (photo) reactions of cosmetic UV filters towards skin proteins / Constanze Stiefel. Betreuer: Wolfgang Schwack". Hohenheim : Kommunikations-, Informations- und Medienzentrum der Universität Hohenheim, 2015. http://d-nb.info/1068856564/34.

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Mallampati, Bhargav. "Development of High Gain Ultraviolet Photo Detectors Based on Zinc Oxide Nanowires". Thesis, University of North Texas, 2014. https://digital.library.unt.edu/ark:/67531/metadc500106/.

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Semiconductor nanowires acts as an emerging class of materials with great potential for applications in future electronic devices. Small size, large surface to volume ratio and high carrier mobility of nanowires make them potentially useful for electronic applications with high integration density. In this thesis, the focus was on the growth of high quality ZnO nanowires, fabrication of field effect transistors and UV- photodetectros based on them. Intrinsic nanowire parameters such as carrier concentration, field effect mobility and resistivity were measured by configuring nanowires as field effect transistors. The main contribution of this thesis is the development of a high gain UV photodetector. A single ZnO nanowire functioning as a UV photodetector showed promising results with an extremely high spectral responsivity of 120 kA/W at wavelength of 370 nm. This corresponds to high photoconductive gain of 2150. To the best of our knowledge, this is the highest responsivity and gain reported so far, the previous values being responsivity=40 kA/W and gain=450. The enhanced photoconductive behavior is attributed to the presence of surface states that acts as hole traps which increase the life time of photogenerated electrons raising the photocurrent. This work provides the evidence of such solid states and preliminary results to modify the surface of ZnO nanowire is also produced.

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37

Mattei, Ryan M. "Investigation of Photonic Annealing on the Atomic Layer Deposition Metal-Oxides Incorporated in Polymer Tunnel Diodes". The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1574691625451168.

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38

Martins, Alysson Stefan. "Estudo e otimização da degradação dos herbicidas hexazinona e diuron utilizando processos oxidativos avançados (POA): H2O2/UV e foto-Fenton". Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/75/75135/tde-23042013-112727/.

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Agrotóxicos são frequentemente relatados na literatura em contaminações de ambientes aquáticos, sendo provenientes do lixiviamento de solos, do descarte inadequado de embalagens agrícolas, dentre outros. Nesse contexto, os processos oxidativos avançados (POA) têm sido estudados como alternativa para o tratamento desses compostos em meio aquoso. Os POA consistem na oxidação de compostos orgânicos pela formação de radicais livres com alto poder oxidante. Diante desses aspectos, o presente trabalho teve como proposta o estudo da degradação dos herbicidas hexazinona e diuron, aliada ao planejamento experimental do tipo composto central, a fim de otimizar o processo de degradação. Para tanto, realizaram-se as degradações através dos processos H2O2/UV e foto-Fenton em concentrações iniciais próximas a 7 e 20 mg L-1 para a hexazinona e diuron, respectivamente. Os experimentos foram conduzidos em um reator fotoquímico (200 mL a 25 °C) com aplicação de irradiação UV, proveniente de uma lâmpada de Hg (degradação H2O2/UV) e de luz negra (degradação foto-Fenton). No processo via H2O2/UV foram avaliadas a concentração de H2O2 (0,65 a 13,34 mmol L-1) e pH (2,77 a 11,23), e para o processo foto-Feton avaliou-se a concentração de H2O2 (0,09 a 29,1 mmol L-1) e Fe (II) (0,01 a 0,92 mmol L-1). Como variável independente, utilizou-se a remoção de Carbono Orgânico Total (COT) nos dois casos. A eficiência na degradação dos herbicidas foi determinada através das técnicas de Espectroscopia UV-Vis, Cromatografia Líquida de Alta Eficiência (HPLC/UV), remoção de Carbono Orgânico Total e Cromatografia de Íons. A análise dos modelos matemáticos, obtidos a partir dos planejamentos, possibilitou a avaliação da influência das variáveis, determinando as melhores condições. No processo H2O2/UV observou-se que a influência da variável H2O2 é maior comparada ao pH. A melhor condição de degradação apresentou concentrações de H2O2 iguais a 7 mmol L-1 e valores de pH de 2,8. Como resultado, obteve-se 96 % de remoção do COT e a não detecção de ambos os herbicidas após 2 minutos de reação. No processo foto-Fenton, a realização de três planejamentos foi necessária para a otimização do sistema. Primeiro e segundo planejamentos indicaram a melhor condição, enquanto que o terceiro planejamento revelou que concentrações elevadas de H2O2 e Fe2+ não garantem maior eficiência. As condições ideais encontradas foram iguais a 0,291 mmol L-1 para o Fe2+ e 2,91 mmol L-1 para o H2O2, obtendo-se 76 % de remoção do COT e não detecção dos herbicidas nos primeiros minutos de degradação. Em ambas as degradações não foi possível observar diferenças em relação a cinética de degradação para os herbicidas. A degradação via H2O2/UV mostrou melhor desempenho, pois apresentou maior taxa de mineralização além de não necessitar o emprego do íon Fe(II).
Pesticides are often reported in the literature on aquatic environments contamination, being a result of soil leaching, improper disposal of agricultural packages, among others. In this context, advanced oxidation processes (AOP) have been studied as an alternative to treat these compounds in aqueous medium. The AOP consist in the oxidation of organic compounds through the formation of free radicals with a high oxidizing power. Considering these aspects, the present work aimed to study degradation of the herbicides diuron and hexazinone, coupled with an experimental setup as central compost, in order to optimize the degradation process. For this purpose, the degradation was carried out by H2O2/UV and photo-Fenton processes at initial concentrations close to 7 and 20 mg L-1 to hexazinone and diuron, respectively. The experiments were conducted in a photochemical reactor (200 mL at 25 ° C) with application of UV irradiation from Hg lamp (H2O2/UV degradation) and black-light (photo-Fenton degradation). In the H2O2/UV process, the concentrations of H2O2 (0.65 to 13.34 mmol L-1) and pH (2.77 to 11.23) were evaluated, and in the photo-Fenton process, the concentrations of H2O2 (0.09 to 29.1 mmol L-1) and Fe (II) (0.01 to 0.92 mmol L-1) were analyzed. In both processes, the removal of Total Organic Carbon (TOC) was used as an independent variable. The efficiency of the herbicide degradation was determined by UV/Vis spectroscopy, high performance liquid chromatography (HPLC/UV), removal of the Total Organic Carbon and ion chromatography. The analysis of the mathematical models obtained from the experimental setup allowed the evaluation of the variables influence ,determining the best conditions. The H2O2/UV process showed that the influence of the H2O2 is higher compared to that of the pH. The best degradation condition presented H2O2 concentrations of 7 mmol L-1 and a pH value of 2.8. As a result, 96% TOC removal was observed, and none of the herbicides were detected after 2 minutes of reaction. In the photo-Fenton process, the conduction of three setups was necessary to confirm the best condition. The first and second setups indicated the best condition, while the third one showed that high concentrations of H2O2 and Fe2+ do not guarantee a greater degradation efficiency. Ideal conditions were equal to 0.291 mmol L-1 for Fe2+ and 2.91 mmol L-1 for H2O2, where 76% of TOC removal was obtained and also no herbicides detection was seen in the early minutes of degradation. In both processes, it was not possible to observe differences in the degradation kinetics of the herbicides. The H2O2/UV degradation showed better performance because of a greater mineralization rate besides not requiring the ion Fe (II) use.

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Gnau, Jennifer Leigh. "Evaluating the Role of UV Exposure and Recovery Regimes in PAH Photo-Induced Toxicity to Daphina Magna". Thesis, University of North Texas, 2017. https://digital.library.unt.edu/ark:/67531/metadc1011884/.

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Polyaromatic hydrocarbons (PAHs) are contaminants synthesized through incomplete combustion of carbon based substances. PAHs are known to be photodynamic and toxicity increases exponentially when in contact with ultraviolet radiation (UV). The effect of UV absent recovery periods and potential for latent toxicity during photo-induced toxicity are previously unknown and are not included within the toxicity model. Results of equal interval tests further support the current reciprocity model as a good indicator of PAH photo-induced toxicity. Interval test results also indicate a possible presence of time-dependent toxicity and recovery thresholds and should be included into toxicity risk assessments. Moreover, results of latent effects assays show that latent mortality is a significant response to PAH photo-induced toxicity and should be included into toxicity risk assessments. The present research demonstrates that UV exposure time rate is a significant driving force of PAH photo-induced toxicity.

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40

Bagherzadeh, Kasiri Masoud. "Contribution à l'étude de dégradation des colorants organiques par le procède d'oxydation avancée UV/Fe-ZSM5/H2O2". Thesis, Mulhouse, 2009. http://www.theses.fr/2009MULH3051.

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L’utilisation de colorants synthétiques se développe depuis de nombreuses années dans des différentes industries. Les procèdes les plus couramment utilises pour le traitement des eaux usées colorées sont les traitements biologiques mais ils ont leurs limites. Les techniques d’oxydation chimique traditionnelle quant a elles conduisent à la coupure de la molécule au niveau du chromophore ne peuvent pas minéraliser totalement des colorants alors que la dépollution complète de ces effluents l’exigerait. Le procède photo-fenton homogène est une technique de traitement qui peut dégrader les effluents colores efficacement. Mais il y a quelques inconvénients majeurs qui limitent l’application industrielle de cette technologie. L’objectif de ce travail de recherche était d’étudier la décoloration et la dégradation des solutions des colorants: acide orange 7 acide orange 8 acide rouge i4 acide rouge 73 et acide bleu 74 par le procède d’oxydation avancée: photo-Fenton heterogene. Dans ce procède la zeolite fe-zsm5 a été utilisée comme un catalyseur heterogene. L’application de ce système nous a permis d une part de diminuer la quantité de boue formée au cours du traitement ainsi que la consommation d’énergie électrique engendrée par l’utilisation d’UV estimée à l aide de la méthode figures-of-merit et d’autre par d’étendre l’application du procède type photo-fenton aux ph plus élevés. La modélisation des procèdes étudies a été faite par deux méthodes à la méthodologie de surface de réponse (RSM) et les réseaux neuronaux artificiels (ANNS) - afin d optimiser la performance de système et également d'évaluer les effets simples et combines des différentes variables sur l’efficacité du traitement
Large amounts of dyes are annually produced and applied in different industries. The biological methods are widely used for treatment of coloured ef fluents, but they have some limitations. Traditional chemical oxidations that destroy the chromophore of the molecule could not also result the complete mineralisation of the dyes. Homogeneous photo-fenton is a promising technique for treatment of the effluents but there are still some drawbacks that limit the industrial applications of this method. The aim of this work was to study the decolourisation and the degradation of coloured solution containing acid orange 7 acid orange 8 acid red I4 acid red 73 or acid blue 74 by an advanced oxidation process: heterogeneous Photo-fenton. In this study zeolite fe-zsm5 was used as a heterogeneous catalyst. Application of this system not only allowed us to diminish the quantity of sludge formed during the process but also reduced the consummation of electrical energy process keeps its high efficiency even at neutral phs. The modelling of the process was done by two methods - response surface methodology (RSM) and artificial Neural networks (ANNS) in order to optimise the performance of the system and to evaluate the simple and the combined effects of different variables on the process efficiency

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41

Wosinski, Lech. "Technology for photonic components in silica/silicon material structure". Doctoral thesis, KTH, Microelectronics and Information Technology, IMIT, 2003. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-3556.

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The main objectives of this thesis were to develop a lowtemperature PECVD process suitable for optoelectronicintegration, and to optimize silica glass composition forUV-induced modifications of a refractive index in PECVDfabricated planar devices. The most important achievement isthe successful development of a low temperature silicadeposition, which for the first time makes it is possible tofabricate good quality low loss integrated components whilekeeping the temperature below 250oC during the entirefabrication process. Two strong absorption peaks thatappear at1.5 mm communication window due to N-H and Si-H bonds have beencompletely eliminated by process optimization. This openspossibilities for monolithic integration with other,temperature sensitive devices, such as semiconductor lasers anddetectors, or polymer-based structures on the common siliconplatform. PECVD technology for low loss amorphous silicon inapplication to SiO2/Si based photonic crystal structures hasbeen also optimized to remove hydrogen incorporated during thedeposition process, responsible for the porosity of thedeposited material and creation of similar to silica absorptionbands.

Change of the refractive index of germanium doped silicaunder UV irradiation is commonly used for fabrication of UVinduced fiber Bragg gratings. Here we describe our achievementsin fabrication of fiber Bragg gratings and their application todistributed sensor systems. Recently we have built up a laserlab for UV treatment in application to planar technology. Wehave demonstrated the high photosensitivity of PECVD depositedGe-doped glasses (not thermally annealed) even without hydrogenloading, leading to a record transmission suppression of 47dBin a Bragg grating photoinduced in a straight buried channelwaveguide. We have also used a UV induced refractive indexchange to introduce other device modifications or functions,such as phase shift, wavelength trimming and control ofpolarization birefringence.The developed low temperature technology and the UVprocessing form a unique technology platform for development ofnovel integrated functional devices for optical communicationsystems.

A substantial part of the thesis has been devoted tostudying different plasma deposition parameters and theirinfluence on the optical characteristics of fabricatedwaveguides to find the processing window giving the besttrade-off between the deposition rate,chamber temperatureduring the process, optical losses and presence of absorptionbands within the interesting wavelength range. The optimalconditions identified in this study are low pressure (300-400mTorr), high dilution of silane in nitrous oxide and high totalflow (2000 sccm), low frequency (380 KHz) RF source and high RFpower levels (800-1000 W).

The thesis provides better understanding of the plasmareactions during the deposition process. RF Power is the keyparameter for increasing the rate of surface processes so as toaccommodate each atomic layer in the lowest energy statepossible. All the process conditions which favor a moreenergetic ion bombardment (i.e. low pressure, low frequency andhigh power) improve the quality of the material, making it moredense and similar to thermal oxide, but after a certain pointthe positive trend with increasing power saturates. As theenergy of the incoming ion increases, a competing effect setsin at the surface: ion induced damage and resputtering.

Finally, the developed technologies were applied for thefabrication of some test and new concept devices for opticalcommunication systems including multimode interference (MMI)-based couplers/splitters, state-of-the-art arrayed waveguidegrating-based multi/ demultiplexers, the first Bragg gratingassisted MMI-based add-drop multiplexer, as well as moreresearch oriented devices such as a Mach-Zehnder switch basedon silica poling and a Photonic Crystal-based coupler.

Keywords:silica-on-silicon technology, PECVD, plasmadeposition, photonic integrated circuits, planar waveguidedevices, UV Bragg gratings, photosensitivity, arrayed waveguidegratings, multimode interference couplers, add-dropmultiplexers.

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42

Wang, Xiaoning. "Photocatalytic degradation of p-hydroxyphenylacetic acid (p-HPA) and Acetaminophen (ACTP) using bismuth catalyst BiOClxIy and Fe(III)-EDDS/UV/H2O2-Na2S2O8". Thesis, Université Clermont Auvergne‎ (2017-2020), 2018. http://www.theses.fr/2018CLFAC051.

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Au cours des dernières décennies, les produits pharmaceutiques sont devenus une nouvelle préoccupation environnementale. Les produits pharmaceutiques ont été largement détectés dans les eaux souterraines, les eaux de surface et même dans l'eau de boisson, avec une concentration allant du ng au µg L-1 dans les effluents d'eaux usées. Les stations d’épuration ne peuvent pas éliminer complètement tous les produits pharmaceutiques en raison de leur faible concentration dans l’eau et de leur résistance à la dégradation biologique. Dans les procédés d’oxydation avancée (AOP), les méthodes les plus fréquemment utilisées incluent les réactions homogènes telles que le procédé de Fenton, de type Fenton ou le procédé Photo-Fenton.Dans ce travail, un nouveau catalyseur composite BiOCl0,75I0,25 a été synthétisé par méthode de précipitation sous pression ambiante et à basse température, suivie d'une série de caractérisations. De plus, les capacités d'adsorption et de dégradation photocatalytique du catalyseur dans l'eau ont été testées sous une lumière solaire simulée en utilisant deux polluants chimiques (Acétaminophène, acide p-hydroxyphénylacétique)
In recent decades, pharmaceuticals and personal care products (PPCPs) have emerged as a new environmental concern. Pharmaceuticals have been widely detected in ground water, surface water and even drinking water with a concentration ranging from ng to µg L-1 in wastewater effluents. Sewage treatment plants (STPs) cannot remove completely all pharmaceuticals due to their low concentration in water and resistance to biological degradation. In AOPs, the most frequently used methods include homogeneous reaction such as Fenton, Fenton like or Photo-Fenton process. In this work, composite catalyst BiOCl0.75I0.25 was synthesized by precipitation method under ambient pressure and low temperature followed with a series of characterization. Moreover, the adsorption and photocatalytic degradation abilities of new bismuth catalyst in water are tested under simulated solar light using Acetaminophen, p-hydroxyphenylacetic acid and as chemical pollutant

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Mabiala, Floyd Lionel. "Photo-physical properties of lead-tin binary Perovskite thin films". University of Western Cape, 2021. http://hdl.handle.net/11394/8002.

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>Magister Scientiae - MSc
Organic-inorganic lead-based perovskite has exhibited great performance in the past few years. However, the lead (Pb) embedded in those compounds is a significant drawback to further progress, due to its environmental toxicity. As an alternative, tin (Sn) based-perovskites have demonstrated promising results in terms of electrical and optical properties for photovoltaic devices, but the oxidation of tin ion- from stannous ion (Sn2+) to stannic ion (Sn4+) presents a problem in terms of performance and stability when exposed to ambient conditions. A more feasible approach may be in a Pb-Sn binary metal perovskite in pursuit of efficient, stable perovskite solar cells (PSCs) with reduced Pb-content, as compared to pure Pb- or Sn-based PSCs. Here, we report on the deposition of a Pb-Sn binary perovskite by sequential chemical vapor deposition.

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44

Güere, Carlos Dante Gamarra. "Estudo da degradação do metil parabeno utilizando processos Fenton, foto-Fenton e eletro-Fenton". Universidade de São Paulo, 2014. http://www.teses.usp.br/teses/disponiveis/75/75134/tde-21112014-160153/.

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Os disruptores endócrinos são frequentemente relatados na literatura como contaminantes de ambientes aquáticos. Por isso, os processos oxidativos avançados (POAs) têm sido estudados como alternativa para o tratamento em meio aquoso. Os POAs consistem na oxidação de compostos orgânicos por radicais hidroxilas com alto poder oxidante. Diante desses aspectos, o presente trabalho tem como principal objetivo o estudo da degradação do metil parabeno (MeP) por processos Fenton, utilizando planejamento experimental e a análise dos modelos matemáticos, possibilitando a avaliação da influência das variáveis e determinando as melhores condições. As degradações de 300 mL de 100 mg L-1 de MeP com o processo Fenton foram realizadas em um reator de vidro onde as concentrações ótimas foram: 16 mg L-1 de Fe2+, 62 mg L-1 de H2O2, pH = 3, agitação constante e 30°C chegando a 100% de degradação em 20 minutos. Para o foto-Fenton, as degradações foram de 500 mL de 100 mg L-1 de MeP em um reator com lâmpada de mercúrio de 4 W , utilizando-se uma concentração de 4 mg L-1 de Fe2+ e 52 mg L-1 de H2O2, pH = 3, 30°C e agitação constante chegando a 100% de degradação em 16 minutos. Finalmente a degradação de 300 mL de 100 mg L-1 de MeP por eletro- Fenton foi realizada em um reator, com 4 mg L-1 de Fe2+, com densidade de corrente (j = 25 mA cm-2) para a produção de H2O2 com eletrodos ADE(cátodo), platina(ânodo), 0,05 mol L-1 de Na2SO4 como eletrólito suporte, pH = 3, sob agitação constante e 30°C chegando a 100% de degradação em 11 minutos. A eficiência da degradação de MeP foi monitorada por espectroscopia UV-VIS e cromatografia liquida de alta eficiência (CLAE) e, a mineralização, pelo monitoramento do carbono orgânico total (COT).
Endocrine disruptors are frequently reported in the literature as contaminants of aquatic environments. Therefore, the advanced oxidation processes (AOPs) have been studied as an alternative to aqueous media treatments. AOPs involve the oxidation of organic compounds by hydroxyl radicals with high oxidation power. Considering these aspects, the aim of the present work is to study the methyl paraben (MeP) degradation by Fenton processes using experimental design and analysis of mathematical models, allowing the evaluation of the influence of variables and determining the best conditions. The degradation of 300 mL of 100 mg L-1 of MeP with Fenton process was performed in a glass reactor where the optimal concentrations were 16 mg L-1 of Fe2+, 62 mg L-1 of H2O2, pH = 3, constant stirring and T = 30°C, reaching 100 % degradation in 20 minutes . For the photo-Fenton degradations were 500 mL of 100 mg L-1 of MeP in a reactor with a mercury lamp with 4 W, using concentration of 4 mg L-1 of Fe2+, 52 mg L-1 of H2O2, pH = 3 , T = 30°C and constant stirring, reaching 100 % biodegradation in 16 minutes. Finally, the degradation of 300 mL of 100 mg L-1 of MeP by electro-Fenton was carried out in a reactor with 4 mg L-1 of Fe2+ with current density (j = 25 mA cm-2) for the production of H2O2 with ADE electrodes (cathode), platinum (anode), 0.05 mol L-1 Na2SO4 as supporting electrolyte, pH = 3, T = 30°C and constant stirring, to reaching 100 % degradation in 11 minutes. The degradation efficiency of MeP was monitored by UV- VIS spectroscopy and liquid chromatography (HPLC) and mineralization, by monitoring the total organic carbon (TOC).

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Mizdrak, Jasminka. "Human lens chemistry: UV filters and age-related nuclear cataract". Australia : Macquarie University, 2007. http://hdl.handle.net/1959.14/16855.

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"A thesis submitted in partial fulfillment of the requirements for the award of the degree of Doctor of Philosophy".
Thesis (PhD) -- Macquarie University, Division of Environmental and Life Sciences, Dept. of Chemistry and Biomolecular Sciences, 2007.
Bibliography: p. 243-277.
Introduction -- A convenient synthesis of 30HKG -- Facile synthesis of the UV filter compounds 30HKyn and AHBG -- Synthesis, identification and quantification of novel human lens metabolites -- Modification of bovine lens protein with UV filters and related metabolites -- Effect of UV light on UV filter-treated lens proteins -- Conclusions and future directions.
The kynurenine-based UV filters are unstable under physiological conditions and undergo side chain deamination, resulting in α,β-unsaturated carbonyl compounds. These compounds can react with free or protein bound nucleophiles in the lens via Michael addition. The key sites of the UV filters kynurenine (Kyn) and 3-hydroxykynurenine (3OHKyn) modification in human lenses include cysteine (Cys), and to a lesser extent, lysine (Lys) and histidine (His) residues. Recent in vivo studies have revealed that 3-hydroxykynurenine-O-β-D-glucoside (3OHKG) binds to Cys residues of lens crystallins in older normal human lenses. As a result of this binding, human lens proteins become progressively modified by UV filters in an age-dependent manner, contributing to changes that occur with the development of age-related nuclear (ARN) cataract. Upon exposure to UV light, free UV filters are poor photosensitisers, however the role of protein-bound species is less clear. It has been recently demonstrated that Kyn, when bound to lens proteins, becomes more susceptible to photo-oxidation by UV light. Therefore, the investigation of 3OHKG binding to lens proteins, and the effect of UV light on proteins modified with 3OHKG and 3OHKyn, were major aims of this study. As a result of the role of these compounds as UV filters and their possible involvement in ARN cataract formation, it is crucial to understand the nature, concentration and modes of action of the UV filters and their metabolites present in the human lenses. Therefore, an additional aim was to investigate human lenses for the presence of novel kynurenine-based human lens metabolites and examine their reactivity.--As 3OHKG is not commercially available, to conduct protein binding studies, an initial aim of this study was to synthesise 3OHKG (Chapter 2). Through the expansion and optimisation of a literature procedure, 3OHKG was successfully synthesised using commercially available and inexpensive reagents, and applying green chemistry principles, where toxic and corrosive reagents were replaced with benign reagents and solvent-free and microwave chemistry was used. A detailed investigation of different reaction conditions was also conducted, resulting in either the improvement of reaction yields or reaction time compared to the literature method. Applying the same synthetic strategy, and using key precursors from the synthesis of 3OHKG, the UV filters 3OHKyn and 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid-O-β-D-glucoside (AHBG), were also successfully synthesised (Chapter 3).
Chapter 4 describes the investigation of both normal and cataractous human lenses in an attempt to identify novel human lens metabolites derived from deaminated Kyn and 3OHKyn (Chapter 4, Part A). Initially, 4-(2-aminophenyl)-4-oxobutanoic acid (AHA), glutathionyl-kynurenine (GSH-Kyn), kynurenine yellow (Kyn yellow), 4-(2-amino-3-hydroxyphenyl)-4-oxobutanoic acid (AHB), glutathionyl-3-hydroxykynurenine (GSH-3OHKyn) and 3-hydroxykynurenine yellow (3OHKyn yellow) were synthesised and human lenses were examined for their presence. AHA and AHB were synthesised from similar precursors to those used in the synthesis of 3OHKG, while the GSH adducts and yellow compounds were synthesised from Kyn and 3OHKyn via base induced deamination. Following isolation and structural elucidation, AHA, AHB and GSH-Kyn were confirmed as novel human lens metabolites. They were quantified in low pmol/mg lens (dry mass) levels in normal and cataractous lenses of all ages, while GSH-3OHKyn, Kyn yellow and 3OHKyn yellow were not detected. In contrast to AHA, the lens metabolites AHB, GSH-Kyn and GSH-3OHKyn were found to be unstable at physiological pH. The spectral properties of these compounds suggest that they may act as UV filters. --Chapter 4 (Part B) also describes the identification and characterisation of a novel human lens UV filter, cysteinyl-3-hydroxykynurenine -O-β-D-glucoside (Cys-3OHKG). An authentic standard was synthesised via Michael addition of cysteine to deaminated 3OHKG. Cys-3OHKG was detected in low pmol/mg lens (dry mass) levels in normal lenses only after the 5th decade of life and was absent in cataractous lenses. Cys-3OHKG showed rapid decomposition at physiological pH.
Chapter 5 describes the identification and quantification of amino acids involved in covalent binding of 3OHKG to lens proteins. Model studies with bovine lens proteins and 3OHKG at pH 7.2 and 9.5 were undertaken. The amino acid adducts were identified via total synthesis and spectral analysis, and subsequently quantified upon acid hydrolysis of the modified lens proteins. Under both pH conditions, 3OHKG was found to react with lens proteins predominantly via Cys residues with low levels of binding also detected at Lys residues. Comparative studies with Kyn (pH 9.5) and 3OHKyn (pH 7.2 and 9.5) resulted in modified lens proteins at Cys residues, with only minor modification at Lys residues at pH 9.5. The extent of modification was found to be significantly higher at pH 9.5 in all cases. His adducts were not identified. 3OHKG-, Kyn- and 3OHKyn-modified lens proteins were found to be coloured and fluorescent, resembling those of aged and ARN cataractous lenses. In contrast, AHB and AHA, which can not form α,β-unsaturated carbonyl compounds, resulted in non-covalent modification of lens proteins. AHB may contribute to lens colouration and fluorescence as further reactions of this material yielded species that have similar characteristics to those identified from 3OHKyn modification. These species are postulated to arise via auto-oxidation of the o-aminophenol moiety present in both 3OHKyn and AHB.--In Chapter 6, the potential roles of 3OHKG and 3OHKyn, and the related species AHA and AHB, in generating reactive oxygen species and protein damage following illumination with UV light was examined. The UV filter compounds were examined in both their free and protein-bound forms. Kyn-modified proteins were used as a positive control. Exposure of these compounds to UV light (λ 305-385 nm) has been shown to generate H2O2 and protein-bound peroxides in a time-dependent manner, with shorter wavelengths generating more peroxides. The yields of peroxides were observed to be highly dependent on the nature of the UV filter compound and whether these species were free or protein bound, with much higher levels being detected with the bound species. Thus, protein-bound 3OHKyn yielded higher levels of peroxide than 3OHKG, with these levels, in turn, higher than for the free UV filter compounds. AHB-treated lens proteins resulted in formation of low but statistically significant levels of peroxides, while AHA-treated lens proteins resulted in insignificant peroxide formation. The consequences of these photochemical reactions have been examined by quantifying protein-bound tyrosine oxidation products (3,4-dihydroxyphenylalanine [DOPA], di-tyrosine [di-Tyr]) and protein cross-linking. 3OHKG-modified proteins gave elevated levels of di-Tyr, but not DOPA, whereas 3OHKyn-modified protein gave the inverse. DOPA formation was observed to be independent of illumination and most likely arose via o-aminophenol auto-oxidation. AHB- and AHA-treated lens proteins resulted in statistically insignificant di-Tyr formation, while a light independent increase in DOPA was observed for both samples. Both reducible (disulfide) and non-reducible cross-links were detected in modified proteins following illumination. These linkages were present at lower levels in modified, but non-illuminated proteins, and absent from unmodified protein samples.
This work has provided an optimised synthetic procedure for 3OHKG and other lens metabolites (Chapters 2 and 3). Four novel lens metabolites have been identified and quantified in normal and cataractous human lenses (Chapter 4). Subsequent experiments, described in Chapter 5, identified the major covalent binding sites of 3OHKG to lens proteins, while AHA and AHB showed non-covalent binding. Further work described in Chapter 6 showed that protein-bound 3OHKG, Kyn and 3OHKyn were better photosensitisers of oxidative damage than in their unbound state. Together, this research has provided strong evidence that post-translational modifications of lens proteins by kynurenine-based metabolites and their interaction with UV light appear, at least in part, responsible for the age-dependent colouration of human lenses and an elevated level of oxidative stress in older lenses. These processes may contribute to the progression of ARN cataract.
Mode of access: World Wide Web.
xxxix, 308 p. ill. (some col.)

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46

Nghiem, Mai Phuong. "Mécanismes physico-chimiques des modifications de contaminants moléculaires sous irradiation UV-V sur satellites". Toulouse, ISAE, 2010. http://www.theses.fr/2010ESAE0004.

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En environnement spatial, la contamination moléculaire des surfaces des satellites constitue un problème majeur par la modification de leurs propriétés optiques ou thermo-optiques. En présence de rayonnements UV, les dégradations peuvent être aggravées par la fixation photochimique de contaminants. Le travail présenté dans cette thèse concerne donc les modifications physico-chimiques des contaminants moléculaires sous l’irradiation UV-V (ultraviolet du vide : 100 – 200 nm) entraînant cette fixation. Dans le but de comprendre les mécanismes de ces modifications, nous avons effectué des expériences de contamination et d'irradiation avec des contaminants purs. La formation de produits sous irradiation a été caractérisée de façon massique in situ (dépôt et ATG sur microbalance à quartz) et ex situ par des méthodes morphologiques (MEB), optiques (spectrométrie UV-Visible-PIR et IR) et chimiques (Chromatographie Phase Gazeuse couplée Spectrométrie de Masse). Différentes conditions de dépôt ont été étudiées (croissance d'un dépôt irradié, irradiation d'un dépôt épais) et une étude paramétrique sur les conditions d'irradiation a été menée. Nous avons ainsi pu mettre en évidence la modification et la fixation des contaminants et proposer des mécanismes de modification physico-chimiques des contaminants sous l’effet des UV-V. Des radicaux libres sont formés sous irradiation UV-V des contaminants. Leur addition forme des molécules de volatilités variées dont les petites expliquent la photolyse observée, tandis que les grosses molécules expliquent la fixation de contaminants dégradant les surfaces des satellites.

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47

Skelte, Gabrielle. "Enhancing colour development of photochromic prints on textile : Physical stabilisation during UV-radiation exposure". Thesis, Högskolan i Borås, Akademin för textil, teknik och ekonomi, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:hb:diva-12373.

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Textile UV-radiation sensors has lately been introduced to the field of smart textiles. Inkjet printing has been used as means of application due to the effective and resource efficient process. UV-LED radiation curing has been used in combination with inkjet printing in favour of low energy requirements, solvent free solution and reduced risk of clogging in the print heads. The problems arising when exposing photochromic prints to UV-radiations are that oxygen inhibition during the curing and photo-oxidation in the print reduces the prints ability to develop colour. It is the oxygen in the air in combination with UV-radiation that gives the photo-oxidating behavior. The aim of the study is to with the aid of physical protection reduce the effect of oxygen inhibition and photo-oxidation in the prints. Three types of physical treatments were used, wax coating, protein based impregnation and starch based impregnation. Treatments were applied before curing as well as after curing and the colour development after activation during 1 min of UV-radiation was measured with a spectrophotometer. Multiple activations were also tested to see how the treatments affected the fatigue behaviour of the prints over time. The aim was to have as high colour development as possible reflecting reduced oxygen inhibition and photo-oxidation. Results showed significantly higher colour development for samples treated with wax and whey powder before curing, but reduced colour development for amylose impregnation. Over time whey powder before curing showed highest colour development due to highest initial colour development. Lowest fatigue was seen for washed samples containing the chemical stabiliser HALS, showing an increased colour development. In reference to earlier studies the protective properties of wax and whey powder is due to their oxygen barrier properties protecting the print. The tested treatments have shown that it is possible to reduce the effect of photo-oxidation during curing leading to prints giving higher colour development. This gives a great stand point when improving existing and future application of photochromic prints on textiles.

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48

Labriola, Vanessa Feltrin. "LEDs-UV como fontes luminosas alternativas para processos oxidativos avançados: inativação de nitrofurantoína pelo processo foto-Fenton". Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/75/75135/tde-17052017-154027/.

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O objetivo desta pesquisa foi estudar a degradação,pelo processo foto-Fenton, de um poluente-modelo (um antibiótico da classe dos nitrufuranos:a nitrofurantoína), utilizando-seLEDs-UV no lugar das lâmpadas tradicionalmente utilizadas, ou seja, das lâmpadas fluorescentes negras.Foram comparadas duas câmaras de irradiação, cada uma com um tipo de fonte, em termos de: porcentagem de remoção, ecotoxicidade (Lactuca sativa), atividade antimicrobiana (Escherichia coli), custos de capital (equipamentos), de operação (consumo energético) e das fontes luminosas, além do espaço ocupado. Os experimentos de degradação foramrealizados e otimizados via planejamento experimental, utilizando-se a Metodologia de Superfície de Resposta, obtendo-se as concentrações ótimas denitrofurantoína, de íons férricoe de peróxido de nitrogênio para cada caso.As câmaras estudadas apresentaram desempenhos semelhantes na remoção de nitrofurantoína (mais de 95% em 15 min), além de não ter havido a geração de produtos ecotóxicos (Lactuca sativa) e de ter sido alcançada a inativação biológica (Escherichia coli) do fármaco.A câmara de irradiação com LEDs é compacta, custa duas vezes menos que a outra e é quatro vezes mais eficiente em termos de consumo elétrico. A única desvantagem encontrada foi o custo dos LEDs-UV. Levando-se em conta o número de LEDs e de lâmpadas fluorescentes negras nas câmaras, o custo é trinta vezes maior. No entanto, o custo adicional dos LEDs-UV em relação às lâmpadas fluorescentes negras é facilmente compensado pela economia realizada nos custos de capital (aquisição do equipamento) e de operação (consumo energético).Em suma, pelo menos no caso da degradação da nitrofurantoína pelo processo foto-Fenton, os LEDs-UV mostraram-se substitutos vantajosos das lâmpadas fluorescentes negras, tradicionalmente utilizadas.
The goal of this research was to study the degradation, by the photo-Fenton process, of a model-pollutant (an antibiotic fromthe nitrofurans group: nitrofurantoin), using UV-LEDs instead of the lamps traditionally used, i.e. black fluorescent lamps. Two irradiation chambers were compared, each one of them with a type of light source, regarding: removal percentage, ecotoxicity (Lactuca sativa), antimicrobial activity (Escherichia coli), capital costs (equipment), operating costs (energy consumption), and light sources costs, as well as the space the chambers occupy.The degradation experiments were performed and optimized by experimental design, using the Response Surface Methodology, and obtaining the optimum concentrations of nitrofurantoin, ferric ions, and hydrogen peroxide, for each of the chambers. The studied chambers showed similar performances regarding nitrofurantoin removal (more than 95% in 15 min), besides the generation of no ecotoxic products (Lactuca sativa) and the biological inactivation (Escherichia coli) of the drug. The irradiation chamber with UV-LEDs is compact,cheaper (it is half of the price of the other one), and it is four times more efficient in terms of electric consumption. The sole disadvantage found was the cost of the UV-LEDs. Taking into consideration the number of LEDs and black fluorescent lamps used in the chambers, thiscost is 30 times greater. However, the additional cost of the UV-LEDsin comparison to black fluorescent lamps is easily compensated by the savings in capital costs (equipment acquisition) and operating costs (electric consumption). In summary, at least regarding the nitrofurantoin degradation by the photo-Fenton process, the UV-LEDs proved to beworthwhile alternatives for black fluorescent lamps, which are traditionally used.

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49

Shanwan, Anwar. "Développement d’un pilote de fabrication automatisée de photo-composites semi-ouvrés (pré-imprégnés)". Thesis, Mulhouse, 2014. http://www.theses.fr/2014MULH6931/document.

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Les véhicules de demain, (2020), devront diminuer leurs émissions globales de CO2 de 30% selon les directives européennes. Une solution qui apparait aujourd’hui comme inévitable est la substitution des métaux présents dans les châssis de véhicules par des matériaux composites plus légers et tout aussi performants. Pour généraliser cette approche à tout le secteur automobile, un temps court de fabrication des pièces est exigé pour satisfaire les cadences de production allant jusqu’à 1000 véhicules par jour. La production automatisée et robotisée de ces matériaux, basée sur la technologie de photo-polymérisation au moyen de rayonnements UV, répond à ces exigences. Le procédé de fabrication élaboré se décompose en deux phases : une phase de fabrication automatisée de pré-imprégnés (prépregs), produits semi-finis, et une phase de mise en forme et d’obtention du produit final (composite UV). La première étape consiste en l’imprégnation d’un renfort fibreux sec par une résine liquide photo-polymérisable, puis l’irradiation de celle-ci par des rayonnements UV, de manière à ce que la résine ne soit pas totalement polymérisée. On obtient alors un prépreg collant. La seconde étape de fabrication impose que les pré-imprégnés soient conditionnés parfaitement sous forme de bobines pour qu’ils soient intégrés dans un dispositif robotisé de dépose. D’où la nécessité de concevoir et de réaliser une machine automatisée de production des pré-imprégnés (objet de cette thèse). Cette machine a nécessité une automatisation se caractérisant par l'utilisation d'outils d'instrumentation et de pilotage modernes (servomoteurs Brushless, IHM, capteurs, …). Les essais réalisés sur cette machine ont permis de réaliser des premiers prépregs, dont les résultats ont conduit à des pistes de réflexion pour approfondir l'automatisation de la machine en vue d'améliorer le procédé de fabrication de ces prépregs
The overall CO2 emission of the future vehicles, (2020), must be reduced by 30%, according to European directives. A solution that seems inevitable nowadays is the substitution of metals present in the vehicle chassis by lighter and equally efficient composite-materials. To generalize this approach throughout the automotive sector, a short manufacturing time of these materials is required to meet the high required production rates, of up to 1000 vehicles per day. The automated and robotic production of these materials, depending on the photo polymerization technology by UV radiation, meets these requirements. The developed automated manufacturing process consists of two phases: the phase of automated manufacturing of semi-finished composite (prepreg), and the phase of shaping and obtaining the final composite (UV composite). The first phase depends on the impregnation of fibrous reinforcement with a photo-polymerizable and liquid resin, then, on the partial irradiation of impregnated reinforcement with UV rays, in such a way that the resin is not completely cured. Thereby, a tacky prepreg is obtained. The second phase of automated manufacturing process requires that the prepregs must be perfectly reeled up in a form of coils, so that they can be incorporated in a robotic lay-up placement head. Hence, the need to design and produce a machine of automated prepreg production (subject of this thesis) is absolutely necessary. This machine requires automation, characterized by the use of modern instrumentations and control tools (Brushless Servo, Human–computer interface HCI, sensors...). The tests performed by this machine have enabled the production of the first prepregs, of which the results led to further approaches to develop the automation of this machine in order to improve the prepregs manufacturing process

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50

Coralli, Irene. "Analysis of chemical degradation of caffeine in aqueous solution using an advanced oxidation process: Fenton's reagent and UV radiation". Master's thesis, Alma Mater Studiorum - Università di Bologna, 2019. http://amslaurea.unibo.it/17964/.

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The present study is aimed to analyse the degradation of caffeine in water employing an advanced oxidation process, the photo-Fenton reaction (H2O2/Fe2+/UV). Different concentrations of H2O2 and Fe2+ are used to evaluate the effects of the two reagents on the quality of the water after the reaction and on the kinetics of degradation. The quality of the water is estimated in terms of conductivity, turbidity, colour and aromaticity. These quantities were found to be not dependent on H2O2 concentrations, whereas the Fe2+ concentration affects them in a proportional way. Compared to the limits of European Directives, the resulting conductivity is acceptable. Turbidity and colour exceed the limits, and the observed influence of the catalyst suggests that they are due to iron species, not to reaction products. Finally, the method employed to evaluate the aromaticity, based on absorbance at 254 nm, does not seem to be reliable. The kinetics of degradation are elaborated through measurements of the absorbance at 272 nm as a function of time. The dependence of the reaction rate on H2O2 concentration observed here is small, but even the lowest concentration employed is 16 times larger than that of caffeine. When the H2O2 concentration is kept constant, a nearly direct proportionality results between reaction rates and Fe2+ doses. Further analyses have shown that caffeine can also be degraded only under UV-visible irradiation (no reagents), but the reaction would need a very long time (6% in 45 minutes). With the addition of Fe2+ (without H2O2) the reaction rate was found somewhat higher, while with the addition of only H2O2 (without Fe2+) the photo-degradation rate was found to be 2/3 of that measured using both reagents. Therefore, the Fe2+ catalyst contributes to the degradation, but dissociation of the perossidic O-O bond of H2O2 to give OH• radicals can also be directly caused by UV irradiation.

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Tesis sobre el tema "UV photons"

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