Flat panel displays (FPDs) are microfabricated devices that are often fabricated on specialized glass substrates known as display glass. The surface chemistry of the outer few nanometers of display glass can have an important influence on FPD performance and yield. Dsiplay glass surface characterization is difficult because (i) display glass surface composition varies significantly from its bulk composition; (ii) high-surface area forms of glass, such as fibers and powders, may not have the same surface composition as melt-formed planar surfaces, and (iii) the surface composition of display glass may be altered through exposure to chemical treatments commonly used during flat panel display production, including acids, bases, etchants, detergents, and plasmas. We have performed a detailed surface composition of Eagle XG®, a widely used commercial display glass substrate, using a range of surface analytical techniques including time-of-flight secondary ion mass spectrometry (ToF-SIMS), angle-resolved X-ray photoelectron spectroscopy (AR-XPS) and low energy ion scattering (LEIS). The information from these techniques has given us a detailed understanding of the elemental surface composition and surface hydroxylation of Eagle XG® at length scales ranging from ca. 10 nm from the surface to the outermost atomic layer. These analyses reveal that the surface composition of Eagle XG® varies significantly from its bulk composition, having generally lower concentrations of Al, B, Mg, Ca, and Sr, and higher concentrations of Si. Treatment with an industrial alkaline detergent results in significant recovery of aluminum concentration at the Eagle XG® surface, while treatment with hydrochloric and hydrofluoric acid result in further depletion of Al, B, Mg, Ca, and Sr at the sample surface.We used ToF-SIMS to quantify surface hydroxyls at the sample surface of this material. The SiOH+/Si+ peak area ratio was a useful metric of surface hydroxylation. We studied the effects of adventitious surface contamination on the measurements by analyzing samples dosed with perdeuterated triacontane, a model alkane, prior to analysis. Thick triacontane overlayers suppressed the SiOH+ signal, indicating that this approach gives inaccurately low estimates of surface hydroxylation for samples with high degrees of surface contamination, and accurate measurements are only possible for very-clean surfaces. The number of of hydroxyls on Eagle XG® surfaces varied as the surfaces were exposed to different chemical treatments. HF- and HCl- treated surfaces had the highest degree of hydroxylation, while detergent-treated surfaces had the lowest.

Doctor of Philosophy / Department of Chemical Engineering / Keith L. Hohn / To characterize surface properties by current techniques, metal oxides typically have to be pre-treated at high temperature to remove surface absorbents. Therefore, a new low temperature method which can provide information on the surface chemistry is desired. In this work, the surface properties of metal oxide samples were studied by tetrakis(dimethylamino)ethylene (TDE) chemiluminescence (CL). This chemiluminescent method was also employed in probing the properties of reversed microemulsions. It was found that the emission intensity vs. reaction time curve (I[subscript]t) of catalyzed TDE CL on MgO was affected by the distributions and types of surface hydroxyl groups. Isolated hydroxyls with lower coordination were found to have higher catalytic reactivity for the emission of TDE CL. Although hydrogen bonded hydroxyls also catalyze the TDE oxidation reaction, the influence on the light emission was negative. Because the properties of surface hydroxyls are associated with specific orientations of adjacent ions, information on surface hydroxyls can provide information about some general surface characteristics of a metal oxide. When characterizing surface hydroxyls on Al[subscript]2O[subscript]3 by TDE CL, it was found that the catalytic reactivity of isolated hydroxyl groups is strongly associated with the stretching frequency of isolated hydroxyl. The stretching frequency of an isolated hydroxyl group is related to the modification of the adjacent ions and the coordination of the isolated hydroxyl. The results showed that the blue-shifts in the stretching frequencies of isolated hydroxyls led to increases in the catalytic reactivity of Al[subscript]2O[subscript]3 surfaces for the emission of TDE CL. TDE CL was further applied in characterizing the surfaces of other metal oxides and chemically grafted Al[subscript]2O[subscript]3. The results indicated that the isolated hydroxyl groups with fewer adjacent ions likely have higher affinity for the binding of grafting agents. Higher emission intensities were obtained from catalyzed TDE CL on metal oxides featuring higher percentages of isolated hydroxyls. The determination of a surfactant’s critical micellar concentration was accomplished by measuring the decay rate of the emission of TDE CL in a reversed microemulsion system. In this study, the CMC values of non-ionic and ionic surfactants were measured in different non-polar solvents.

Permanent production and use of organic chemicals for many purposes has resulted in their introduction and accumulation in the environment. Depending on their physicochemical properties they can be transported by different ways from the source to very remote regions of the planet. Many organic chemicals are used in agriculture as pesticides for cultures protection or nutrient. Residues of these chemicals can always be found in fields, and under the effect of precipitations they leach and pass in streams and rivers. Pharmaceuticals and personal health care products and other house holding chemicals are continuously introduced in the environment through municipal wastewaters. These substances exhibit, in most of the cases, perturbation effects towards the living organisms, moreover the effect of many of them is not known yet. Despite their concentration in water is low, the exposure of organisms for long periods can lead to negative consequences, but these effects cannot be measured instantly. In order to reduce or avoid the pollution of water with chemicals many water treatment methods has been developed like adsorption of pollutants on adsorbents, membrane filtration, microbiological treatment, chemical oxidation with oxidizing agents and advanced oxidation processes. Most of the methods used in waste water treatment plants (WWTP) do not completely destroy the organic contaminants or they only separate the contaminants from water. Then they have to be deposed somewhere else remaining always a potential source of contamination. Advanced oxidation processes and in particular electrochemical advanced oxidation processes are methods developed later and are proven as more effective as they can completely oxidize the organic matter in water. The subject of this thesis is the use of electro-Fenton, an electrochemical advanced oxidation process for efficient destruction of organic pollutants in aqueous medium. In this method, organic pollutants are eliminated by H hydroxyl radicals (high oxidation power species) which are produced in situ through the Fenton's reagent (H2O2 + Fe2+) itself generated in the solution electrochemically and continuously. In this process, the electrode material is of fundamental importance in order to have an efficient process, so we have studied at large extent the influence of both cathode and anode material in this work. Firstly a systematic study on the oxidation capacity of the process of amoxicillin (AMX) as model pollutant with several anodes materials: BDD, Pt, DSA, PbO2 Carbon felt, Graphite and Carbon fibre was realised. In all cases a stainless steel electrode was used as cathode. The degradation of AMX was followed by HPLC analysis whereas the mineralization efficiency ot the process was measured by total organic carbon analyser (TOC). This revealed that BDD was the most efficient anode for AMX oxidation and DSA was the weakest one. Carbon felt showed a characteristic behaviour; it was very efficient on AMX oxidation but it could not transform AMX to CO2 and H2O. Afterwards four anodes were tested for their influence on electro-Fenton process efficiency namely Pt, BDD, DSA and Carbon felt, the cathode was always carbon felt. Sulfamethazine (SMT) was used as model pollutant. Apparent rate constants have given only moderate values of mineralization for currents lower than 100 mA. Here again the BDD anode was distinguished for its excellent mineralization capacity owing to the additional hydroxyl radicals and other oxidizing species introduced in the system. When electro-Fenton applied good degradation and mineralization results were obtained even with the DSA anode (...)

L'application d'ultrasons sur une tumeur, où des liposomes se sont accumulés, permet potentiellement de libérer le médicament mais aussi d'en favoriser l'absorption dans les cellules. La cavitation inertielle ultrasonore est le phénomène pressenti pour la libération sous ultrasons de médicament encapsulé dans de petits liposomes solides. Elle est très dépendante des conditions expérimentales et peut-être intense et imprévisible. L'objectif principal du travail réalisé dans le cadre de cette thèse est de contrôler et quantifier la cavitation inertielle, pour induire le largage de médicaments encapsulés dans des liposomes. Dans cette optique, une dose de cavitation inertielle (DC), basée sur le filtrage du bruit large bande émis lors de ce régime de cavitation, est mise au point in vitro pour suivre le largage de médicament encapsulé. Sous divers régimes d'ultrasons pulsés, la DC a été validée en dosant chimiquement les radicaux hydroxyles générés lors de l'implosion des bulles. Les tests menés sur diverses formulations de liposomes contenant de la doxorubicine (dox) ont montrés une haute corrélation entre le taux de largage de dox et la DC permettant de conclure que la cavitation inertielle est impliquée dans ce largage. Le rôle de la température sur la production de radicaux hydroxyles et la libération de dox a également été exploré. Les expériences réalisées ont permis de sélectionner les formulations les plus sensibles aux ultrasons pour les tester sur des rats implantés avec des tumeurs prostatiques. Après plusieurs expériences in vivo menées avec différents dispositifs ultrasonores et formulations de liposomes, le bénéfice du traitement combiné a pu être démontré. / The sonication of a tumor, where liposomes have been accumulated, allows potentially to release encapsulated drug and to promote its absorption in cells. Ultrasonic inertial cavitation is supposed to be implicated in the release of drug encapsulated in small solid liposomes under ultrasonic exposure. Inertial cavitation is strongly dependent on experimental conditions and can be very intense and unpredictable. The main objective of this thesis was to control and quantify inertial cavitation in order to induce drug release from liposomes. In this purpose, an inertial cavitation dose (CD), based on broadband noise emission associated with inertial cavitation, was defined to monitor in vitro encapsulated drug release. The CD was chemically validated with the dosing of hydroxyl radicals generated by bubbles collapses under various pulsed ultrasound exposures. A high correlation between doxorubicin (dox) release rate from liposomes and CD was de monstrated for all liposomes formulations tested and under different pulsed ultrasound exposures. The role of temperature on hydroxyl radical production and dox release was also investigated. The performed experiments allowed selecting the liposomes formulations that are the most sensible to ultrasound in order to test them on rats implanted with prostatic tumors. After several campaigns of in vivo experiments performed with various ultrasonic setups and liposomes formulations, the benefit of the combined treatment was demonstrated.

Le travail réalisé porte sur la caractérisation et la valorisation de la Biolignine™ de paille de blé extraite à l'échelle semi-industrielle par le procédé CIMV. La première partie est consacrée à l'étude structurale du produit et à la quantification de ses diverses fonctions hydroxyles et acides carboxyliques. Dans la seconde partie, la Biolignine™ a été utilisée, en tant que substituant du bisphénol-A, dans la synthèse de résine époxy. Les études de DSC et DLTMA ont démontré qu'après post-réticulation, les résines époxy Biolignine™-PEGDGE possèdent des caractéristiques thermomécaniques comparables à celles d'une résine époxy à base de bisphénol-A. Les résultats obtenus permettent désormais d'envisager la synthèse de résines époxy à base de Biolignine™ à plus grande échelle. / This thesis relates the structural characterization and the application of wheat straw BiolignineTM extracted at semi-industrial scale by the CIMV process. The first part is the structural study of the BiolignineTM and the quantification of its hydroxyl groups and carboxylic acids functions. In the second part, the BiolignineTM was used, as a substitute of bisphenol-A, in the synthesis of epoxy resins. DSC and DLTMA studies showed that after post-curing, epoxy resins of BiolignineTM-PEGDGE have thermomechanical properties similar to those of a bisphenol-A based epoxy resin. The results lead to the scope of BiolignineTM based epoxy resins synthesis at larger scale.

Numerous chemical species are important to the health of biological systems. Some species can be beneficial at low doses and harmful at high doses. Other species are highly reactive and trigger serious cell damage. Improved methods to detect the presence and activity of such species are needed. In this work, several biologically important species were studied using appropriate analytical techniques. Fluoride is an important species in human physiology. It strengthens teeth and gives protection against dental caries. However, elevated concentrations of fluoride in the body can lead to health problems such as dental and skeletal fluorosis. Reported fluoride sensors used fluorescence quenching methods in determining fluoride concentration. Our study explored synthesis and characterization of 1,8-bis(phenylthioureido) naphthalene (compound 1) as a fluoride sensing molecule. Compound 1 showed a remarkable 40 fold enhancement in fluorescence with 5 eq of fluoride addition. Compound 1 also showed possibility of visual colorimetric sensing with fluoride. Free radical mediated oxidations of biomolecules are responsible for different pathological conditions in the human body. Superoxide is generated in cells and tissues during oxidative burst. Moderately reactive superoxide is converted to peroxyl, alkoxyl and hydroxyl radicals by various enzymatic, chemical, and biochemical processes. Hydroxyl radical imparts rapid, non specific oxidative damage to biomolecules such as proteins and lipids. Superoxide also reacts with nitric oxide in cells to yield peroxynitrite, which is highly reactive and damages biomolecules. Both hydroxyl radical and peroxynitrite readily react with amino acids containing aromatic side chains. Low density lipoprotein (LDL) carries cholesterol in the human body. Elevated concentration of LDL is a potential risk factor for atherosclerosis. Previous research drew a strong correlation between oxidized low density lipoprotein (ox-LDL) and plaque formation in the arterial wall. More importantly, oxidative damage causes structural changes to the LDL protein (apo B-100) which might facilitate the uptake of LDL by macrophages. In this study LDL was exposed to various concentrations of hydroxyl radical peroxynitrite and hypochlorite. Thereafter oxidized amino acid residues in apo B-100 were mapped by LC-MS/MS methods. We found widely distributed oxidative modifications in the apo B-100 amino acid sequence.

Le radical hydroxyle (OH) représente le plus important oxydant dans la troposphère et le puits de la plus grande partie des composés à l’état de trace de l’atmosphère. Si les sources des radicaux hydroxyles sont aujourd’hui relativement bien connues, le terme ‘puits’ des OH, connu sous le terme de réactivité atmosphérique totale avec les radicaux OH (ou réactivité OH) (s-1), reste encore difficile à quantifier. En raison de la complexité des instruments nécessaires, peu de mesures de OH et de réactivité sont actuellement disponibles et la nouvelle méthode proposée par Sinha et al., (2008) représente une alternative prometteuse pour la quantification de la réactivité atmosphérique totale avec les radicaux hydroxyles. Cette méthode est appelée Méthode Comparative de Réactivité (CRM) et est basée sur la mesure rapide d’une molécule normalement absente de l’atmosphère (ici pyrrole, C4H5N) et qui réagit à un taux connu avec les radicaux hydroxyles produits artificiellement dans une petite cellule de réaction en verre. La comparaison des concentrations de pyrrole obtenues en présence/absence d’air ambiant, dans un champ de radicaux constant, permet de quantifier la réactivité de l’air ambiant. Cette thèse a eu pour objectif principal le développement et l’optimisation de cette méthode pour la mesure de réactivité en zone urbaine, fortement riche en monoxyde d’azote (NO), composé identifié comme produisant des artefacts de la mesure. De même, il fallait proposer une méthodologie pour intégrer toutes les corrections, inhérentes à la méthode, à appliquer aux valeurs brutes de réactivité. Une fois la méthode mise au point, le deuxième objectif de ces travaux était la caractérisation de la réactivité atmosphérique totale avec les radicaux OH à Paris, une des rares mégacités existantes en Europe et où aucune mesure de réactivité n’avait été rapportée auparavant. L’étude réalisée pendant la campagne d’hiver 2010 du projet européen MEGAPOLI a permis de caractériser le niveau de réactivité à Paris pendant deux régimes de masses d’air différentes, océanique / continental. Ainsi il a été possible de distinguer un niveau de réactivité purement local de Paris et Ile de France (impacté par le caractère « trafic » de cette ville européenne et étant comparable aux niveaux enregistrés à New York et Tokyo), et un niveau fort, importé, caractéristique d’un transport longue distance. De même, l’étude a révélé que pendant l’import continental, de forts pourcentages ont été enregistrés de réactivité manquante, définie comme la différence entre la valeur mesurée et une valeur théorique, calculée à partir des composés réagissant avec OH et mesurés pendant la campagne. La nature des espèces non-mesurées et contribuant à cette réactivité a été déterminée comme oxydée, issue des processus de « processing » des masses d’air sur le trajet long distance. Ce travail apporte dans un premier temps des informations uniques sur la méthode CRM pour la mesure de la réactivité OH (fonctionnement, traitement des données) et contribue par la suite à la caractérisation des niveaux de réactivité dans la région parisienne. / The hydroxyl radical (OH) represents the most important oxidant of the troposphere and the sink of most trace compounds in the atmosphere. If the sources of the OH radicals are nowadays relatively well constrained, the ‘sink’ term, also known as the total atmospheric reactivity with the OH radicals (or simply OH reactivity) (s-1), is still difficult to quantify. Due to the complexity of the used instruments, only few OH reactivity measurements are currently available. A new method proposed by Sinha et al. (2008) represents a promising alternative to the quantification of the total ambient OH reactivity. This method, also called the Comparative Reactivity Method (CRM), is based on the rapid measurement of a molecule normally not present in the ambient air (here, pyrrole, C4H5N) and which reacts at a known rate with OH radicals artificially generated into a glass reaction cell. Comparing the measured signals of pyrrole with and without ambient air within a constant OH field allows the quantification of the total OH reactivity of the ambient air. The main objective of this PhD work was the development and the improvement of this method for OH reactivity measurements in urban areas, which are abundant in nitrogen oxide (NO), a compound known to produce artifacts in the reactivity measurement. In the same time, it was necessary to propose a methodology to integrate all corrections (inherent to the method) to the raw reactivity data. Once the method adjusted, the second aim of this work was the characterization of the ambient OH reactivity in Paris, one of the few Megacities in Europe and where no other reactivity measurements were previously reported. The study conducted during the 2010 winter campaign of the MEGAPOLI European project allowed to quantify the OH reactivity level in Paris during two different air mass regimes, marine/continental. It was therefore possible to distinguish between a purely local OH reactivity level (about 20s-1) of Paris and Ile de France (impacted by the ‘traffic’ character of this European city and comparable to levels registered in New York and Tokyo) and a high (more than 100 s-1) , imported level characterized by a long distance transport. The study also revealed that during the continental import, high percentages (up to 75%) were registered of the missing OH reactivity, defined as the difference between the measured reactivity and a theoretical value obtained from the reactive compounds measured during the same campaign. The nature of the non-measured species contributing to this missing reactivity was determined as oxidized, issued of the air masses “processed” during the long distance transport. This work brings unique information on the CRM method and contributes to the characterization of the OH reactivity levels in the region of Paris.

Cette thèse a pour objet l’analyse de la cinétique de la conversion de l’acétaldéhyde, CH₃CHO, à des concentrations initiales inférieures ou égale à 5000 ppm dans un mélange de gaz à base d’azote et contenant jusqu’à 20% d’oxygène, à température ambiante. L’étude a été réalisée en utilisant trois réacteurs mettant en œuvre des décharges de qualités spatiales différentes. Il s’agit d’un réacteur (UV510) à décharge pré-ionisée (photo-déclenchée) par rayonnement UV produisant un plasma homogène, et de deux réacteurs à décharge à barrière diélectrique (DBD), de géométrie plane (plan-plan) et de géométrie cylindrique (tige-tube) alimentés par impulsion HT et produisant des plasmas non homogènes à faible (plan) ou forte (cylindre) filamentation ; un diagnostic d’imagerie rapide (ns) de la DBD de géométrie plane montre que le plasma peut être considéré quasi-homogène. En s’appuyant sur une modélisation 0D auto-cohérente de la décharge photo-déclenchée, l’étude de la cinétique du mélange N₂/CH₃CHO montre l’importance des états métastables de la molécule d’azote, triplet A³Σu⁺, et singlets (groupe a' ¹∑⁻u, a ¹∏g, et w ¹Δu) dans la dissociation de l’acétaldéhyde. Un coefficient minimum de 6.5×10⁻¹¹ cm³.s⁻¹ est estimé pour le quenching des singlets par l’acétaldéhyde. Le coefficient du triplet est estimé entre 4.2×10⁻¹¹ cm³.s⁻¹ et 6.5×10⁻¹¹ cm³.s⁻¹. Cette dissociation produit des radicaux (CH₃, CH₃CO, HCO, H, O) et des molécules (CH₄, CH₂CO, C₂H₄, C₂H₂, H₂, CO). Ainsi les sous-produits majoritaires mesurés à la fin de la post décharge temporelle sont le méthane, le dihydrogène, le monoxyde de carbone et l’éthane. Les minoritaires sont l’acétylène, l’éthène, l’acétone et l’acétonitrile. Dans les mélanges contenant de l’oxygène, l’importance de la dissociation de CH₃CHO par quenching des états métastables de N₂ diminue au profit des processus d’oxydation par le radical hydroxyle, OH, et l’oxygène atomique, O (³P). La mesure résolue en temps du radical OH dans la post-décharge du réacteur UV510 montre une très forte réactivité de ce radical avec les sous-produits de conversion de l’acétaldéhyde. Une densité maximum de OH égale à 3.5×10¹⁴ cm⁻³ a été mesurée pour 10 % d’oxygène et 5000 ppm d’acétaldéhyde. Le schéma cinétique adopté pour ces mélanges donne, par la modélisation auto-cohérente, une valeur de densité plus élevée. Toutefois, la conversion de l’acétaldéhyde dans N₂/O₂/CH₃CHO est bien expliquée par le modèle, de même que les concentrations produites de méthane et d’éthane. Enfin, la comparaison de l’efficacité énergétique des trois réacteurs étudiés montre que l’homogénéité de la décharge favorise, pour des milieux pauvres en oxygène (moins de 2 %), la conversion de l’acétaldéhyde. / The present study deals with the kinetics analysis of acetaldehyde (CH₃CHO) conversion in electrical discharges with different spatial qualities et at room temperature. Acetaldehyde concentrations up to 5000 ppm in nitrogen-based gas mixture containing up to 20% of oxygen have been investigated. Three different plasma reactors were used: an UV510 reactor producing a homogeneous plasma thanks to a pre-ionization by UV radiation (photo-triggered), a plane-to-plane and a rod-tube dielectric barrier discharges (DBDs) reactors, In both DBDs reactors discharges were driven by high voltage pulses allowing the production of weakly inhomogeneous plasma in the plane geometry and highly filamentary discharges in the cylindrical one. A high speed imaging diagnostic (ns range) of the plane-to-plane DBD shows that the plasma can be considered quasi-homogeneous. Based on a self-consistent 0D model, the kinetics study of the N₂/CH₃CHO mixture conversion in the photo-triggered discharge shows the importance of nitrogen molecule metastable states , i.e. the triplet A³Σu⁺ and the singlets group a' ¹∑⁻u, a ¹∏g, et w ¹Δu, in the acetaldehyde dissociation process. A minimum coefficient of 6.5×10⁻¹¹ cm³.s⁻¹ has been estimated for the quenching of N₂ singlets state by acetaldehyde. For the triplet states quenching the coefficient of has been evaluated between 4.2×10⁻¹¹ cm³.s⁻¹ and 6.5×10⁻¹¹ cm³.s⁻¹. This dissociation process produces radicals as CH₃, CH₃CO, HCO, H, O, and molecules like CH₄, CH₂CO, C₂H₄, C₂H₂, H₂, CO. Thus, the major by-products detected at the end of the post-discharge time are methane, hydrogen, carbon monoxide and ethane; smaller amounts of acetylene, ethene, acetone and acetonitrile were also detected. In containing oxygen mixtures, the importance of the CH3CHO dissociation processes due to N₂ metastable states quenching of decreases in favor of oxidation processes promoted by the hydroxyl radical, OH, and atomic oxygen, O (³P). Time-resolved measurements of the OH radical in the photo-triggered post-discharge show a very high reactivity of this radical with the by-products of acetaldehyde conversion. A maximum density of OH radical equal to 3.5×10¹⁴ cm⁻³ was measured for 10% oxygen and 5000 ppm of acetaldehyde. The kinetic scheme adopted in the self-consistent model for the same gas mixture gives a higher density value; by the way the model is in good agreement with the acetaldehyde conversion in N₂/O₂/CH₃CHO mixtures, as well as with the methane and ethane produced concentrations. Finally, the comparison of the three studied reactors energy efficiency shows that, for low oxygen content (less than 2%), the homogeneity of the discharge promotes the acetaldehyde conversion.

Après la découverte des rayonnements ionisants et leurs effets chimiques, il était important d’étudier et de comprendre les mécanismes de formations des radicaux libres et des produits moléculaires caractérisés par leurs courtes durées de vie. Ceci a encouragé les groupes de recherches à développer leurs outils pour qu’ils puissent réaliser ces études. De nos jours la radiolyse impulsionnelle se manifeste comme un outil fondamental permettant de sonder les effets chimiques ainsi que les mécanismes réactionnels dans le milieu étudié.Le laboratoire de Chimie Physique d’Orsay « LCP » est un laboratoire interdisciplinaire abritant la plateforme « ELYSE » qui est un centre de cinétiques rapides. Grâce au laser femtoseconde et à l’accélérateur d’électrons picoseconde, nous avons eu la possibilité, dans le domaine de la radiolyse, de remonter en temps, en étudiant les effets chimiques dans un milieu réactionnel, jusqu’à ~ 5 ps.Nous nous sommes intéressés par les réactions primaires induites par les rayonnements ionisants en solution et ELYSE représentait l’outil principal pour ces études. Les résultats obtenus concernent :- La détermination directe du rendement radiolytique du radical hydroxyle « HO• » en fonction du temps à l’échelle de la picoseconde ;- Etude de l’effet direct du rayonnement ionisant sur les solutions aqueuses concentrées ainsi que la vérification de la réaction de transfert d’électron ultrarapide entre le soluté et le trou positif « H2O•+ » issu lors de la radiolyse de l’eau ;- Etude à température ambiante de la réaction de transfert d’électron entre un électron solvaté (donneur d’électron) et un soluté organique (accepteur d’électron) en milieu visqueux ;- Etude à température ambiante de la solvatation de l’électron dans l’éthylène glycol et dans le propan-2-ol. / Following the discovery of ionizing radiations and their chemical effects, it was important to study and comprehend the formation mechanisms of short lived free radicals and molecular products. In order to perform such studies, researchers and research groups worked on developing tools allowing both formation and detection of those species at short time scales. Nowadays, pulse radiolysis imposed itself as a fundamental and efficient tool allowing scientists to probe chemical effects as well as reaction mechanisms in studied media.The laboratoire de Chimie Physique d’Orsay “LCP” is an interdisciplinary laboratory hosting the platform of fast kinetics known as “ELYSE”. Due to its femtosecond laser and its picosecond electron accelerator, we have the possibility to study chemical effects of ionizing radiations interaction with media at ultrashort times up to ~5 ps.Knowing that we are interested in primary reactions induced in aqueous media by ionizing radiations, ELYSE represents the essential tool in performing our studies. The obtained results concern:- First direct determination of hydroxyl radical “HO•” radiolytic yield as function of time at picosecond time scale ;- Direct effect of ionizing radiation in highly concentrated aqueous solutions as well as investigation of the ultrafast electron transfer reaction between solute molecules and positive holes “H2O•+” formed upon water radiolysis ;- Study at room temperature of electron transfer reaction between solvated electron (electron donor) and organic solutes (electron acceptors) en viscous medium ;- Study at room temperature of electron’s solvation dynamics in ethylene glycol and 2-propanol.

Inúmeros trabalhos da literatura científica mostram que a remoção parcial de lignina é útil para facilitar o processo de sacarificação enzimática de materiais lignocelulósicos. No entanto, a maioria dos processos de deslignificação aplica condições severas de reação e apresenta custos elevados de processo. Uma alternativa aos processos mais severos de deslignificação envolve a aplicação de sistemas biomiméticos. Estes sistemas demandam condições amenas de reação, compatíveis com a etapa de hidrólise enzimática, porém geralmente são mais lentos e menos eficientes do que os pré-tratamentos químicos e quimiotermomecânicos convencionais. Ponderando estes fatos, o objetivo desta tese foi estudar a aplicação de sistemas oxidativos e biomiméticos na deslignificação de materiais lignocelulósicos prévios a uma etapa de hidrólise enzimática da fração polissacarídica. A estratégia de trabalho consistiu em pré-tratar bagaço de cana (foram empregados 3 cultivares diferentes de cana no presente estudo) com um processo quimiotermomecânico (CTM) em condições amenas de reação (5,0% de Na2SO3 e 2,5% de NaOH) seguido de um tratamento biomimético oxidativo. Esta abordagem visou gerar um material parcialmente deslignificado que pudesse ter a recalcitrância significativamente diminuída pela aplicação de um processo biomimético. Um segundo pré-tratamento foi aplicado em condições mais severas de reação (10% de Na2SO3 e 5,0% de NaOH) e visou gerar um material de referência, com baixa recalcitrância. Os sistemas biomiméticos empregados tiveram origem nos processos naturais de biodegradação de madeira por fungos de decomposição branca e parda e envolveram a ação de: a) Manganês peroxidase, Lacase, ferro e Oxigênio; b) reação de Fenton mediada por quelantes. Estes sistemas foram suplementados ou não com ácidos graxos insaturados, visando gerar radicais organoperoxila no caso dos sistemas suplementados. As reações de Fenton mediadas por quelantes apresentaram emissão de quimiluminescência, o que permitiu otimizar o sistema reacional com base na máxima quimiluminescência obtida. A remoção de lignina obtida com o pré-tratamento CTM variou de acordo com a carga de sulfito alcalino empregada, sendo que para as severidades baixa e alta, a remoção de lignina atingiu 26% e 54%, respectivamente. Os sistemas biomiméticos aplicados no bagaço de cana, após pré-tratamento com sulfito alcalino na condição branda, produziram graus de deslignificação variáveis, sendo que as principais remoções de lignina foram obtidas com o tratamento de Fenton mediado por quelantes e com Oxigênio, atingindo remoções acumuladas de lignina de 44% e 62%, respectivamente. Em todos os casos avaliados, a remoção adicional de lignina promoveu maiores eficiências de conversão enzimática das frações polissacarídicas residuais. A maior conversão de celulose e hemicelulose (acima de 80%) foi obtida com o tratamento Fenton mediado por quelantes aplicado sobre um cultivar de cana de açúcar que apresentava elevado teor de ácidos hidroxicinâmicos, sugerindo uma ação eficiente destes sistemas para a remoção destes ácidos hidroxicinâmicos. / The current scientific literature shows that lignin removal can facilitates subsequent processes of enzymatic saccharification of lignocellulosic materials. However, most of the delignification processes use severe reaction conditions and present high process costs. One alternative for the severe delignification processes includes the use of biomimetic systems. These systems can be applied under mild reaction conditions, which are compatible with the enzymatic hydrolysis step. Nevertheless, biomimetic systems usually present low reaction rates and are less efficient than the more severe chemical and chemithermomechancial processes. Weighing these facts, the main subject of the current PhD thesis was to study oxidative-biomimetic systems suitable for delignification of lignocellulosic materials as a previous step to the enzymatic hydrolysis of the polysaccharide fraction. The experimental approach involved the pretreatment of sugar cane bagasse (three different sugar cane cultivars were evaluated) by a chemithermomechanical (CTM) process under mild reaction conditions (5% of Na2SO3 and 2.5% NaOH), followed by an oxidative-biomimetic system. This approach aimed to prepare a partially delignified material suitable to be treated by the subsequent biomimetic systems, providing significant changes in the material recalcitrance. A second pretreatment under more severe reaction conditions (10% Na2SO3 and 5% NaOH) was performed to prepare a reference material with low recalcitrance. The biomimetic systems used in the current work were based on natural wood decay processes involving white- and brown-rot fungi, and include the actions of: a) Manganese peroxidase, Laccase, Iron íons and Oxygen; b) Chelator Mediated Fenton reactions (CMF). This reaction systems used (or not) the presence of unsaturated fatty acids to induce formation of organoperoxyl radicals. The CMF reactions presented chemiluminescence, which enabled the reaction optimization with basis on maximal chemiluminescence. The lignin removal during the CTM pretreatment varied according to the alkaline-sulfite load used in the reaction. The delignification increased with increased alkaline-sulfite loads reaching 26% and 54% for the less severe and more severe reaction conditions, respectively. Biomimetic systems applied over the mild-pretreated sugar cane bagasse produced varied delignification levels, reaching maximal values for cumulative lignin removal of 44% and 62% for the CMF and Oxigen, respectively. In all cases, the supplementary removal of lignin resulted in more efficient enzymatic hydrolysis of the polysaccharide fraction. The highest cellulose and hemicellulose conversions (over 80%) was obtained with the CMF system applied on a sugar cane cultivar that contained high hydroxycinnamic acids contents, suggesting an efficient action of CMF systems for hydroxycinnamic acids removal.