Dissertations / Theses on the topic 'Photosensitized reactions'

L’atmosphère est un milieu complexe, loin d’être parfaitement homogène. Elle contient de nombreuses particules, sous formes solides ou liquides, dénommées aérosols. Ces particules peuvent affecter l’équilibre radiatif de la planète, la qualité de l’air dans les milieux urbains et changer la composition chimique de l’atmosphère malgré leur présence à des très faibles teneurs. Par ailleurs, au niveau du sol, la phase gazeuse atmosphérique peut interagir avec la végétation et le bâtiment, tout particulièrement en zone urbaine. Ce travail se situe donc dans le cadre général de l’étude des réactions photoinduites à l’interface air/solide afin de pouvoir comprendre et décrire leur rôle dans la pollution atmosphérique (principalement urbaine). Cette étude a comme objectif principal l’étude de l’influence du rayonnement solaire sur les cinétiques hétérogènes des réactions impliquant le dioxyde d’azote et des surfaces organiques (pyrene, fluoranthene, phénanthrène) pures et des surfaces organiques/inorganiques (pyrene/KNO3, pyrene/Fe2O3, pyrene/KNO3/Fe2O3) simulant le dépôt urbain. De telles réactions n’ont pas encore été étudiées. Ces travaux ont été menés expérimentalement à l’aide de réacteurs de type « tube à écoulement » couplé à un détecteur spécifique du gaz en trace étudié. Après avoir mis en évidence une capture photoinduite sur ces surfaces, nous avons montré que la capture de NO2 dépend de plusieurs paramètres tels que la concentration de NO2, l’humidité relative, le flux photonique avec l’identification des produits de réactions, en l’occurrence l’acide nitreux HNO2, le monoxyde d’azote, les ions nitrites et le 1‐nitropyrene. L’acide nitreux détecté est un élément favorisant les pics de pollution photochimique à l’ozone. Ainsi ce travail est une avancée importante dans ce champ de recherche
The atmosphere contains a wide variety of solid and liquid particles, named Aerosol. These particles can affect the radiatif balance, air quality in urban environment and can change the composition of the atmosphere. The atmospheric gas phase can react with the vegetation and the buildings containing the urban grime. This work is focused on the investigations of the heterogeneous chemistry between atmospheric gas phase and the urban grime. The aim of the present work is to study the effect of the irradiation on the heterogeneous kinetic of NO2 on pur organic films (pyrene, fluoranthene, phenanthrene) and on organic/inorganic films (pyrene/KNO3, pyrene/Fe2O3, pyrene/KNO3/Fe2O3) as a first attempt to simulate the complexity of the urban grime. A coated flow tube reactor coupled with a NOx analyzer is used to study this kinetic. This work demonstrates the effect of solar radiation on the heterogeneous reaction between gasphase NO2 and the urban grime. The uptake coefficient calculated is a function of the initial NO2 concentration, the relative humidity and the irradiation intensity. We identified after this reaction the formation of nitrous acid and nitric oxide, nitrite ions and 1‐nitropyrene.The nitrous acid is an important compound which dissociates to form the hydroxyl radical and can promote the ozone formation. The results discussed herein suggest that PAHcontaining urban grime on windows and buildings may be a key player in urban air pollution

Aquesta tesis estudia computacionalment els processos que expliquen les propietats fotoquímiques de certs compostos orgànics. Per això s’han fet servir mètodes ab initio multiconfiguracionals, CASSCF i CASPT2, amb els que es descriu la topografia de les superfícies d’energia potencial dels estats de més baixa energia i es localitzen els camins de reacció. S’ha estudiat primerament el mecanisme de fotoisomerització del azobenzè i el seu derivat, la fenilazopiridina. El mecanisme de reacció obtingut explica satisfactòriament perquè el rendiment quàntic de la isomerització depèn de l’excitació inicial i del grau de restricció de la rotació interna en aquests sistemes. També s’ha analitzat un protocol computacional per la reproducció de l’espectre d’absorció en solució de sistemes flexibles, fent servir com a exemple la fenilazopiridina. S’ha estudiat també la 9-fenilfenalenona. A diferencia del sistema del que deriva, la fenalenona que presenta un alt rendiment quàntic de sensitització de oxigen singlet, el rendiment quàntic de la 9-fenilfenalenona és molt baix. S’ha demostrat que aquest fet es deu a que en el segon compost la fotoexcitació produeix la formació d’un fotoproducte metaestable per ciclació que ràpidament reverteix al compost original. Aquest estudi ha suposat un repte pel mètodes computacionals que s’han fer servir per la seva gran mida. Per últim s’ha estudiat el dehidroescualè, un carotenoide que intervé en processos d’absorció d’energia lumínica d’organisme vegetals. L’estudi determina l’estructura dels estats excitats de baixa energia i la influència de la flexibilitat d’aquest compost en les energies d’aquests estats. Es demostra que l’aproximació de fer servir tan sols la conformació més simètrica proporciona bons resultats a nivell qualitatiu però que, si es busca la reproducció quantitativa de les observacions experimentals, s’ha de tenir en conta la flexibilitat molecular.
Esta tesis estudia computacionalmente los procesos que explican las propiedades fotoquímicas de ciertos compuestos orgánicos. Para ello se han usado métodos ab initio multiconfiguracionales, CASSCF y CASPT2, con los que se describe la topografía de las superficies de energía potencial de los estados de más baja energía y se localizan los caminos de reacción. Se ha estudiado primeramente el mecanismo de fotoisomerización del azobenzeno y su derivado, la fenilazopiridina. El mecanismo de reacción obtenido explica satisfactoriamente por qué el rendimiento cuántico de la isomerización depende de la excitación inicial y del grado de restricción de la rotación interna en estos sistemas. También se ha analizado un protocolo computacional para poder reproducir el espectro de absorción en disolución de sistemas flexibles, usando como ejemplo la fenilazopiridina. Se ha estudiado también la 9-fenilfenalenona. A diferencia del sistema del que deriva, la fenalenona, que presenta un alto rendimiento cuántico de sensitización de oxígeno singlete, el de la 9-fenilfenalenona es muy bajo. Se ha demostrado que eso se debe a que en el segundo la fotoexcitación produce la formación por ciclación de un fotoproducto metaestable que rápidamente revierte en el compuesto original. Este estudio ha supuesto un reto para los métodos computacionales empleados debido a su gran tamaño. Por último se ha estudiado el dehidroescualeno, un carotenoide que interviene en procesos de absorción de energía lumínica de organismos vegetales. El estudio determina la estructura de los estados excitados de baja energía y la influencia de la flexibilidad de este compuesto en las energías de estos estados. Se demuestra que la aproximación de utilizar sólo la conformación más simétrica proporciona buenos resultados a nivel cualitativo pero que, si se busca la reproducción cuantitativa de las observaciones experimentales, se debe tener en cuenta la flexibilidad molecular.
This thesis develops a computational work to study the processes that explain the photochemical properties of some organic compounds. Multiconfigurational ab initio methods, CASSCF and CASPT2 have been used to determine the topography of the potential energy surfaces of the low energy states and locate reaction paths. We have studied first the mechanism of photoisomerization of azobenzene and its derivative phenylazopyridine. The reaction mechanism obtained explains satisfactorily why the isomerization quantum yield depends on the initial excitation and on the degree of the restriction on the internal rotation of these systems. We have also analysed the performance of a computational protocol to reproduce the absorption spectrum of flexible systems in solution, using phenylazopyridine as target system. We have also studied 9-phenylphenalenone. Its parent system, phenalenone, shows a high quantum yield in the process of singlet oxygen sensitization, but the quantum yield of this phenyl derivate for the same process is very low. Our study shows that this difference is due to a side reaction induced by the initial photoexcitation, which produces a metastable photoproduct by cyclisation that turns back quickly to the initial reactant. This study has been a challenge for the computational methods used due to its big size. Finally, we have studied dehidrosqualene, a carotenoid involved in light harvesting processes in vegetables. Our study determines the structure of the low energy excited states and the influence of the flexibility of this compound in the energy of these states. We show that to use only the most symmetric conformation on this flexible compound to calculate the energy of the excited states, give results that qualitatively agree with the experimental observations but, if quantitative agreement is required, the molecular flexibility must be taken into account.

Photosensitizing molecules and/or metal complexes that interact with DNA via intercalation and groove binding have potential applications as molecular structural probes, as footprinting reagents and in photodynamic therapeutics. To this regard, small molecules that bind to DNA and the energetics involved in these interactions, acridine-based therapeutics, photosensitization, photodynamic therapy, phenothiazine-mediated photosensitization, DNA photocleavage reaction mechanisms and photosensitizing metal complexes are introduced in Chapter I. Next, in Chapter II, the synthesis of a photonuclease consisting of a 3,6-acridinediamine chromophore attached to four metal-coordinating imidazole rings is described. The DNA photocleavage yields, emission quantum yields, and thermal denaturation studies by this acridine-imadazole conjugate in the presence of 16 metal salts are also reported. In Chapter III is the synthesis of a bisacridine covalently tethered to a copper(II)-binding pyridine linker. Additionally, DNA photocleavage studies as well as DNA binding affinity and binding mode(s) of this bisacridine incorporating the copper(II)-binding pyridine linker are examined. The syntheses, characterization, DNA photocleavage studies, DNA thermal denaturation, and viscometric measurements of three new phenothiazinium photosensitizers are described in Chapters IV and V. Collectively, markedly enhanced DNA photocleavage yields are observed in the presence of metals (Chapters II-III) or in comparison to a parent molecule, Chapters II and IV. DNA melting isotherms show higher levels of duplex stabilization with the acridines, specifically in the presence of several metals (Chapter II-III) as well as with the phenothiazine-based ligands (Chapters IV-V). Moreover, different DNA binding modes were observed depending on metal complexation (Chapter III) and nucleic acid structure (Chapter IV). Finally, Chapter VI describes a small project implemented as a National Science Foundation pedagogical laboratory exercise in which a non-invasive procedure for DNA isolation from human cheek cells was utilized with the polymerase chain reaction to amplify alleles encoding a single nucleotide polymorphism involved in normal human color vision.

Différents systèmes polyoxométallates@M-colorants ont été réalisés dans cette thèse pour électrochimique dégagement d'hydrogène catalytique et génération photocourant.• Des films hybrides, basés sur des interactions électrostatiques entre une porphyrine tetracationique et des nanoparticules stabilisées par des POMs du type POM@Pt sur ITO, ont été formés par la méthode dite couche par couche et ont été utilisés pour la génération de H2 ou de photocourant. • Pour améliorer le transfert de charge entre les nanoparticules POM@M et le substrat, la réduction de l'oxyde de graphène a été réalisée pour former des systèmes hybrides rGO/POM@Pt. Le dégagement d'hydrogène a été mesuré.• Les copolymères polycationiques bis-porphyrine ont également été obtenus par électropolymérisation avec des espaceurs bis-pyridinium. Par réaction de métathèse, l’incorporation avec divers POM de type Keggin ou des nanoparticules du type POM@Ag ont ensuite été realise. Leurs performances photovoltaïques ont ensuite été étudiées.• Enfin des films hybrides PEDOT dopés avec des nanoparticules du type POM@M ont également été fabriqués. Les performances photovoltaïques ont été examinés montrant une forte amélioration sous illumination dans le domaine du visible. L’ensemble de ces matériaux hybrides ont montré des propriétés intéressantes pour des applications photovoltaïques et la conversion d'énergie
Polyoxometalates@M NPs-dyes molecular hybrid systems were realized in this thesis for electrochemical catalytic hydrogen evolution and photocurrent generation. • First, hybrid films, based on electrostatic interactions between the tetracationic porphyrin and POMs@Pt NPs composites on ITO slides, were formed by the so called Layer-by-Layer method for HER and photocurrent generation.• To improve the charge transfer between POMs@M NPs and the substrate, reduced graphene oxide was introduced to form rGO/POMs@Pt NPs hybrid systems. Hydrogen evolution was measured after dropping this composites onto the surface of glassy carbon electrodes.• Polycationic bis-porphyrin copolymers have been also obtained by an electropolymerization leading to the formation of new bis-porphyrin copolymers with pyridinium as spacers. Incorporation with various Keggin type POMs or POMs@Ag was then achieved, their photovoltaic performances were also studied.• POMs@M NPs doped PEDOT hybrids films have been also fabricated. The photovoltaic performances has been examined showing particularly strong enhancement under visible light. In conclusion, these polyoxometalates based hybrids materials have shown interesting properties for photovoltaic application and energy conversion

A detailed understanding of natural photosynthesis provides inspiration for the development of sustainable and renewable energy sources, i.e. a technology that is capable of converting solar energy directly into chemical fuels. This concept is called artificial photosynthesis. The work described in this thesis contains contributions to the development of artificial photosynthesis in two separate areas. The first one relates to light harvesting with a focus on the question of how electronic properties of photosensitizers can be tuned to allow for efficient photo-induced electron transfer processes. The study is based on a series of bis(tridentate)ruthenium(II) polypyridyl complexes, the geometric properties of which make them highly appealing for the construction of linear donor-photosensitizer-acceptor arrangements for efficient vectorial photo-induced electron transfer reactions. The chromophores possess remarkably long lived 3MLCT excited states and it is shown that their excited-state oxidation strength can be altered by variations of the ligand scaffold over a remarkably large range of 900 mV. The second area of relevance to natural and artificial photosynthesis that is discussed in this thesis relates to the coupled movement of protons and electrons. The delicate interplay between these two charged particles regulates thermodynamic and kinetic aspects in many key elementary steps of natural photosynthesis, and further studies are needed to fully understand this concept. The studies are based on redox active phenols with intramolecular hydrogen bonds to quinolines. The compounds thus bear a strong resemblance to the tyrosine/histidine couple in photosystem II, i.e. the water-plastoquinone oxidoreductase enzyme in photosynthesis. The design of the biomimetic models is such that the distance between the proton donor and acceptor is varied, enabling studies on the effect the proton transfer distance has on the rate of proton-coupled electron transfer reactions. The results of the studies have implications for the development of artificial photosynthesis, in particular in connection with redox leveling, charge accumulation, as well as electron and proton transfer. In addition to these two contributions, the excited-state dynamics of the intramolecular hydrogen-bonded phenols was investigated, thereby revealing design principles for technological applications based on excited-state intramolecular proton transfer and photoinduced tautomerization.

L'atmosphère est un milieu hautement hétérogène contenant de la matière condensée : les aérosols. Ceux-ci sont des composants importants de l'atmosphère car ils impactent le bilan radiatif planétaire mais aussi la qualité de l'air. En particulier les aérosols organiques secondaires (AOS), produits par la transformation chimique dans l'air de nombreux composés organiques, plus ou moins volatils, représentent une fraction conséquente dans le budget global des aérosols atmosphériques pour laquelle de nombreuses incertitudes persistent. En particulier, leurs voies de formation et de transformation dans la troposphère restent très mal décrites. C'est pourquoi, cette thèse décrit principalement l'étude de trois aspects de la croissance et du vieillissement (transformation) des aérosols : caractérisation de la croissance des AOS par des processus photosensibilisés ; investigations mécanistiques du vieillissement des AOS et de la photochimie des photosensibilisateurs ; analyse chimique des composés issus du vieillissement des AOS
Aerosols are important constituents of the atmosphere and secondary organic aerosols (SOA) represent a main fraction of the organic aerosols in the total budget. This thesis mainly reports the investigation of three aspects of the growth and aging of SOA: the photosensitized SOA growth ; the mechanistic investigation of SOA aging and of the photochemistry of photosensitizers ; the analysis of the chemical composition of aged SOA. The photosensitized growth and aging processes of SOA were investigated using an aerosol flow tube coupled with various aerosol and gas sensing instruments. For further analysis of the aerosol composition and a better understanding of the formation and growth of SOA in these experiments the aerosols produced in the dark and in the light were sampled on filters at the exit of the flow tube

La present tesi esta focalitzada tant en la síntesi de molècules orgàniques òpticament actives així com en la seva aplicació i caracterització en dispositius fotovoltaics, concretament per a les cel·les solars sensibilitzades amb colorant (DSSC en anglès). Les DSSC són cel·les foto-electroquímiques formades per colorant ancorat a un semiconductor (normalment TiO2) i en presencia d'un electròlit. En aquests dispositius, cada component té un efecte clau en la eficiència final de la cel·la, degut als processos de transferència electrònica que tenen lloc la interfície TiO2/colorant/electròlit. Aquests processos varen ser estudiat en gran detall utilitzant porfirines, perilens i D -  - A com a colorants, per poder així definir uns paràmetres amb els quals l'eficiència final del dispositiu es pugui correlacionar amb l'estructura molecular del colorant. Entendre aquesta relació entre l'estructura química i l'eficiència del dispositiu permet un millor diseny de futures molecules per a DSSC.
The present thesis focuses on the synthesis of organic chromophores as well as their use in optoelectronic devices, particulary in Dye Sensitized Solar Cells (DSSC). This kind of solar cell is based on a photoactive unit, a dye, anchored to a nanostructured metal-oxide semiconductor, usually TiO2, in a redox electrolyte media and sandwiched between two contact electrodes. In DSSC devices, each component (semiconductor, sensitizer and electrolyte) plays an important role in determining the final device efficiency, in a large part due to the charge transfer processes that take place at the TiO2/dye/electrolyte interface. Therefore, these charge transfer kinetics were studied using porphyrins, perylenes and donor -  - acceptor organic dyes in order to understand and establish a relationship between the molecular structure and the device performance. Improved understanding of this relationship is crucial for improved molecular design of future dyes for DSSC.

Le travail a porte sur l'etude des lesions induites par des processus de photosensibilisation sur les bases de l'adn dans des composes modeles. Dans un premier temps, les differents processus de photooxydation de la base thymine au niveau du nucleoside ont ete identifies. Il a ete ainsi observe que la benzophenone conduit a plus de degradation du groupement methyle que d'autres photosensibilsateurs. Ceci indique que la benzophenone possede des proprietes d'arrachament d'atome d'hydrogene conduisant a la formation du radical de la thymine centre sur le methyl. Cette meme etape initiale est a l'origine de la formation d'une lesion impliquant la thymine et la guanine dans le dinucleoside monophosphate. Le radical methyle de la thymine s'additionne en position 4 de la guanine et conduit, apres addition d'oxygene et rearrengement, a une liaison covalente stable entre les deux bases. Ces resultats offrent des prespectives nouvelles dans l'etudes des lesions induites dans l'adn par des processus radicalaires.

L'hypericine est un pigment naturel qui possede des proprietes phototoxiques exceptionnelles. Ces proprietes pourraient etre utilisees dans le traitement photochimiotherapeutique de certains cancers et dans la lutte anti-virale. L'utilisation de cette molecule necessite une bonne connaissance de l'ensemble de ses mecanismes d'action. L'etude photophysique de l'hypericine dans des milieux simples est une etape preliminaire. Le travail presente dans ce memoire s'inscrit dans cette demarche. Les proprietes spectroscopiques et photophysiques de l'hypericine y sont examinees. L'influence du milieu sur ces proprietes, les interactions avec l'oxygene et les transferts d'electrons photoinduits y sont etudies. La partie bibliographique comporte un rappel sur les processus de desactivation des etats excites et sur la photosensibilisation ainsi qu'une revue des travaux sur l'hypericine. La premiere partie presente les proprietes spectroscopiques et photophysiques de l'hypericine en solution dans des solvants organiques, dans l'eau et dans des dispersions de liposomes. La desactivation des etats excites de l'hypericine est tres sensible a l'environnement: liaisons hydrogene avec le solvant, auto-extinction dans les liposomes et agregation dans l'eau. La deuxieme partie concerne les proprietes photosensibilisantes de l'hypericine. La formation photosensibilisee de l'oxygene singulet et celle de l'anion radical superoxyde sont evaluees dans les differents milieux. La formation d'oxygene singulet est sensibilisee efficacement a partir du premier etat triplet et la geometrie de la molecule joue un role important sur la desactivation de cet etat. La capacite de l'hypericine a participer a des transferts d'electrons est ensuite examinee. L'etude electrochimique de l'hypericine a ete realisee sur des solutions dans le dmso et des dispersions de liposomes. Des transferts d'electrons photoinduits a partir de l'etat triplet de l'hypericine sont aussi mis en evidence en presence de donneurs et d'accepteurs d'electrons. Les potentiels redox de l'etat triplet sont evalues et permettent de discuter des voies de production de l'anion superoxyde et d'autres ions-radicaux. Ce travail permet de preciser les mecanismes photophysiques qui sont a l'origine de la phototoxicite de l'hypericine en milieu biologique

Sous l'influence conjuguee de la lumiere et de l'oxygene, une solution de polymere et de bleu de methylene subit plusieurs transformations. La photooxygenation conduit uniquement a des hydroperoxydes allergiques: interaction entre l'etat triplet du bleu de methylene et les groupes hydroperoxydes portes par les chaines macromoleculaires. Cinetique et mecanisme

Photosensitizing effects of xenobiotics are of increasing concern in public health since modern lifestyle often associates sunlight exposure with the presence of chemical substances in the skin. An important number of chemicals like perfumes, sunscreen components, or therapeutic agents have been reported as photosensitizers. In this context, a considerable effort has been made to design a model system for photosafety assessment. Indeed, screening for phototoxicity is necessary at the early phase of drug discovery process, even before introducing drugs and chemicals into clinical therapy, to prevent undesired photoreactions in humans. In the case of new pharmaceuticals, their phototoxic potential has to be tested when they absorb in the regions corresponding to the solar spectrum, that is, for wavelengths >290 nm. So, there is an obvious need for a screening strategy based on in vitro experiments. The goal of the present thesis was the photochemical study of different photoactive drugs to investigate the key molecular aspects responsible for their photosensitivity side effects. In a first stage, rosuvastatin was considered in chapter 3 as representative compound of the statin family. This lipid-lowering drug, also known as “superstatin”, contains a 2-vinylbiphenyl-like moiety and has been previously described to decompose under solar irradiation, yielding stable dihydrophenanthrene analogues. During photophysical characterization of rosuvastatin, only a long-lived transient at ca. 550 nm was observed and assigned to the primary photocyclization intermediate. Thus, the absence of detectable triplet-triplet absorption and the low yield of fluorescence ruled out the role of the parent drug as an efficient sensitizer. In this context, the attention was placed on the rosuvastatin main photoproduct (ppRSV). Indeed, the photobehavior of this dihydrophenanthrene-like compound presented the essential components needed for an efficient biomolecule photosensitizer i.e. (i) a high intersystem crossing quantum yield (ΦISC =0.8), (ii) a triplet excited state energy of ca. 67 kcal mol−1 , and (iii) a quantum yield of singlet oxygen formation (Φ∆) of 0.3. Furthermore, laser flash photolysis studies revealed a triplet-triplet energy transfer from the triplet excited state of ppRSV to thymidine, leading to the formation of cyclobutane thymidine dimers, an important type of DNA lesion. Finally, tryptophan was used as a probe to investigate the Type I and/or Type II character of ppRSV-mediated oxidation. In this way, both an electron transfer process giving rise to the tryptophanyl radical and a singlet oxygen mediated oxidation were observed. On the basis of the obtained results, rosuvastatin, through its major photoproduct ppRSV, should be considered as a potential sensitizer. Then, itraconazole (ITZ), a broad-spectrum antifungal agent, was chosen as main character of chapter 4. Its photochemical properties were investigated in connection with its reported skin photosensitivity disorders. Steady state photolysis, fluorescence and phosphorescence experiments were performed to understand ITZ photoreactivity in biological media. The drug is unstable under UVB irradiation, suffering a primary dehalogenation of the 2,4-dichlorophenyl moiety that occurs mainly at the ortho-position. In poorly H-donating solvents, as acetonitrile, the major photoproduct arises from intramolecular attack of the initially generated aryl radical to the triazole ring. In addition, reduced compounds resulting from homolytic cleavage of the C-Cl bond in ortho or para positions and subsequent Habstraction from the medium are obtained to a lesser extent. In good H-donating solvents, such as ethanol, the main photoproducts are formed by reductive dehalogenation. Furthermore, irradiation of a model dyad containing a tryptophan unit and the reactive 2,4-dichlorophenyl moiety of itraconazole leads to formation of a new covalent link between these two substructures revealing that homolysis of the C-Cl bond of ITZ can result in alkylation of reactive amino acid residues of proteins, leading to formation of covalent photoadducts. Therefore, it has been established that the key process in the photosensitization by itraconazole is cleavage of the carbon-halogen bond, which leads to aryl radicals and chlorine atoms. These highly reactive species might be responsible for extensive free radical-mediated biological damage, including lipid peroxidation or photobinding to proteins. In chapter 5, photobehavior of imatinib (IMT) was addressed. This is a promising tyrosine kinase inhibitor used in the treatment of some types of human cancer, which constitutes a successful example of rational drug design based on the optimization of the chemical structure to reach an improved pharmacological activity. Cutaneous reactions, such as increased photosensitivity or pseudoporphyria, are among the most common nonhematological IMT side effects; however, the molecular bases of these clinical observations have not been unveiled yet. Thus, to gain insight into the IMT photosensitizing properties, its photobehavior was studied together with that of its potentially photoactive anilino-pyrimidine and pyridyl-pyrimidine fragments. In this context, steady-state and time resolved fluorescence, as well as laser flash photolysis experiments were run, and the DNA photosensitization potential was investigated by means of single strand breaks detection using agarose gel electrophoresis. The obtained results revealed that the drug itself and its anilino-pyrimidine fragment are not DNA-photosensitizers. By contrast, the pyridyl-pyrimidine substructure displayed a marked photogenotoxic potential, which was associated with the generation of a long-lived triplet excited state. Interestingly, this reactive species was efficiently quenched by benzanilide, another molecular fragment of IMT. Clearly, integration of the photoactive pyridyl-pyrimidine moiety in a more complex structure strongly modifies its photobehavior, which in this case is fortunate as it leads to an improved toxicological profile. Thus, on the bases of the experimental results, direct in vivo photosensitization by IMT seems unlikely. Instead, the reported photosensitivity disorders could be related to indirect processes, such as the previously suggested impairment of melanogenesis or the accumulation of endogenous porphyrins. Finally, a possible source of errors in the TEMPO/EPR method for singlet oxygen detection was analyzed. For many biological and biomedical studies, it is essential to detect the production of 1O2 and to quantify its production yield. Among the available methods, detection of the characteristic 1270 nm phosphorescence of singlet oxygen by time-resolved near infrared (TRNIR) emission constitutes the most direct and unambiguous approach. An alternative indirect method is electron paramagnetic resonance (EPR) in combination with trapping. This is based on the detection of the TEMPO free radical formed after oxidation of TEMP (2,2,6,6- tetramethylpiperidine) by singlet oxygen. Although the TEMPO/EPR method has been largely employed, it can produce misleading data. This was demonstrated by the present study, where the quantum yields of singlet oxygen formation obtained by TRNIR emission and by the TEMPO/EPR method were compared for a set of well-known photosensitizers. The results revealed that the TEMPO/EPR method leads to significant overestimation of singlet oxygen yield when the singlet or triplet excited state of the photosensitizers were efficiently quenched by TEMP, acting as electron donor. In such case, generation of the TEMP+• radical cation, followed by deprotonation and reaction with molecular oxygen gives rise to a EPR detectable TEMPO signal that is not associated with singlet oxygen production. This knowledge is essential for an appropriate and error-free application of the TEMPO/EPR method in chemical, biological and medical studies.
Nardi, G. (2014). MECHANISTIC STUDIES ON THE PHOTOTOXICITY OF ROSUVASTATIN, ITRACONAZOLE AND IMATINIB [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/48535
TESIS

Les réserves de combustibles fossiles diminuent et leur utilisation illimitée depuis la révolution industrielle a généré de profonds changements du climat, notamment des cycles de la température atmosphérique. Stocker l'énergie solaire sous forme d'hydrogène produit par dissociation de l'eau est un moyen idéal pour combattre le réchauffement climatique. Les matériaux de la famille des «metal organic framework» (MOF) commencent à être utilisés comme photo-électrocatalyseurs, notamment pour la photo-dissociation de l'eau. Leur porosité extrêmement élevée et leur grande polyvalence, tant chimique que structurelle, les désignent comme des candidats potentiels pour faciliter l'absorption du rayonnement solaire et catalyser la dissociation de l'eau dans les cellules photoélectrochimiques. En contrôlant la composition chimique et le dopage du linker utilisé dans le MOF, il est possible d'ajuster l'énergie de la bande interdite, de favoriser la fonctionnalisation sur des substrats très variés ou encore d'ajuster leur résistance à la corrosion dans divers environnements chimiques. Ce sont donc des matériaux d'un grand intérêt pour la catalyse, l'électrocatalyse ou la photo-électro-catalyse. D'autre part, le TiO₂ nano-structuré, par exemple sous forme de tapis d’épaisseur micrométrique de nanotubes ou de nanofils, parfois appelé TNA, est un matériau bien adapté à la construction de photoanodes pour le dégagement d'oxygène en milieu aqueux. Il a déjà été largement étudié et décrit dans la littérature. Au cours de notre thèse, nous avons fabriqué des matériaux composites constitués de MOF de métaux de transition (Ni, Co, Fe) déposés sur TNA (TDNR et TNTA). Pour cela, nous avons utilisé une méthode électrochimique d'électrodéposition. Cela nous a permis de déposer des nanoparticules métalliques sur du TNA à potentiel fixe - 1,0 V puis de les transformer par réaction chimique avec des ligands organiques (BTC, BDC, et 2MZ) par voie thermo-thermique. Les matériaux obtenus présentent une activité électrocatalytique significative et une excellente durabilité photoélectrochimique. Ces matériaux composites ont été utilisés avec succès comme phase active dans des photo-électrodes pour la réaction de dégagement d'oxygène moléculaire (OER)
The fossil fuel reserves are dwindling and their unrestricted use has generated profound changes in Earth's surface temperature and climate. Storing solar energy in the form of hydrogen produced by dissociation of water is an ideal way to mitigate global warming. Materials from the “metal organic framework” (MOF) family are starting to be used as photo-electrocatalysts, especially for photo-dissociation of water. Their extremely high porosity and their great versatility, both chemical and structural, designate them as potential candidates to facilitate the absorption of solar radiation and catalyze the dissociation of water in photoelectrochemical cells. By controlling the chemical composition and doping of the linker used in the MOF, it is possible to adjust the band gap energy, to favor the functionalization on very varied substrates or even to adjust their resistance to corrosion in various chemical environments. They are therefore materials of great interest for catalysis, electrocatalysis or photo-electro-catalysis. On the other hand, nano-structured TiO₂, for example in the form of nanotube or nanowire mats, sometimes called TiO₂ nanoarray (TNA), is a material very suitable for the construction of photoanodes for the evolution of oxygen in aqueous medium. It has already been extensively studied and described in the literature. During our thesis, we manufactured composite materials made up of MOFs of transition metals (Ni, Co, Fe) deposited on TNA (network of nanotubes or nanowires). For this we used an electrochemical method of electrodeposition (cyclic voltammetry). This allowed us to deposit metallic nanoparticles on TNA with fixed potential - 1.0 V and then transform them by chemical reaction with organic ligands (1,3,5-benzenetricarboxylic acid, BTC, 1,4-benzenedicarboxylic acid, BDC and imidazole, 2MZ) by thermal-thermal route. The materials obtained exhibit significant electrocatalytic activity and excellent photoelectrochemical durability. These composite materials have been successfully used as an active phase in photo-electrodes for the oxygen release reaction (OER)

L'hypericine, pigment naturel dont la phototoxicite est remarquable, pourrait etre utilisee en phototherapie. La deprotonation a ph>10 se traduit par un effet bathochrome sur le spectre d'absorption. La complexation par un des cations des metaux (al, gd, tb, fe, cu) dans la region ou se situent les groupes carbonyle et hydroxyle s'accompagne, de maniere analogue, d'un deplacement de ce spectre vers le rouge. Nous avons determine les constantes de formation des complexes metalliques de l'hypericine du type (hyp-m) ou (hyp-m2). Les proprietes spectroscopiques et photophysiques des complexes metalliques de l'hypericine ont ete etudiees en liaison avec leurs proprietes phototoxiques. L'etude cinetique de l'oxydation du 1,3-diphenylisobenzofuranne montre que les complexes metalliques de l'hypericine photosensibilisent avec un bon rendement la formation d'oxygene singulet. L'irradiation d'une solution aeree d'hypericine, conduit aussi a la formation du radical anion superoxyde a partir de la reduction de l'oxygene par une semiquinone. Cette formation sensibilisee a ete demontree a l'aide de la reduction du cytochrome c. Les complexes metalliques de l'hypericine peuvent etre utilises comme agents phototherapeutiques

The increasing number of multidrug-resistant strains of bacteria call for alternatives to antibiotic therapy and, more generally, for the antimicrobial material as a component of prevention. Of particular interest is the photodynamic inactivation of bacteria and other pathogens caused by photogenerated singlet oxygen. This work is focused on the field of photoactive polymer nanofiber membranes and nanoparticles, generating singlet oxygen, suitable for medical applications. We prepared different types of photoactive modified polystyrene nanofiber membranes with encapsulated or externally bound porphyrin photosensitizers. These materials efficiently produce highly reactive and cytotoxic singlet oxygen capable of restricted diffusion into to the external environment. Our results demonstrate the crucial role of wettability for materials of this type with a short diffusion length of generated singlet oxygen, illustrate the effect of temperature and indicate their potential use as multifunctional materials. Due to their antimicrobial properties, these materials are suitable alternative to antibiotics and local antiseptics. With good breathability and short diffusion length of singlet oxygen good results can be expect in in vivo tests. From these nanofiber materials we also prepared photoactive extremely...

碩士
國立中山大學
材料與光電科學學系研究所
101
Modern science and technologies are continually developed to create products with respect to humanity and convenience in many aspects of life. However, due to advances of technologies, it has led to serious impact on the environment. Moreover, it also facilitated energy consumption that has been widely concerned. The purpose of this thesis is to investigate how to use LED light sources harden the unsaturated polyester, 2731-LC which is doped the photo-initiator, C47S2. Unsaturated polyester crosslinking reaction has been utilized in maintenance of sewer pipes. The conventional technique is to trigger off thermosetting crosslinking reaction of the unsaturated polyester using thermal heat exchange of hot water. The disadvantage of this technique is to require massive hot water and long reaction time. Hence, the technique consumes plenty of water and energy. To cooperate with Li-Ke-Tung Environmental Ltd., it is proposed that the lower energy consumption and shorter reaction time by investigating the feasibility of replacing conventional thermosetting crosslinking reaction of the unsaturated polyester with LED lighting. Moreover, to develop new techniques, photo-initiator was doped into the unsaturated polyester to investigate the crosslink reaction. Experiments were logically conducted to find a proper wavelength for the UV absorption, to be certain the reaction temperature which will not excess the phase-transition temperature of the polyester leading to broken bonding and to verify effect of irradiance to the hardness of the polyester that confirms the completion of the crosslink reaction. Moreover, variation of the hardness was also investigated by doping thermo-initiator, benzoyl peroxide (BPO) and the experimental curve of the hardness was fit using an exponential function. The hardening experiment of unsaturated polyester is divided into two topics, as follows: (1) Hardening reaction of the unsaturated polyester 2731-LC doped the photo-initiator C47S2 cured by various irradiation energies: This section is to investigate variation of the reaction time by increasing the levels of irradiance energy. (2) Hardening reaction of the unsaturated polyester 2731-LC doped the photo-initiator C47S2 and the thermal initiator BPO with various irradiance energies: The section is to investigate variation of the reaction time of the doped polyester. It is expected that the hardness of the unsaturated polyester can be achieved by shorter light curing period due to additional thermal crosslinking reaction from the doped thermo-initiator, BPO.