Este trabalho tem por objetivo o desenvolvimento de métodos numéricos eficientes, tanto no domínio do tempo quanto na freqüência, para a modelagem da propagação de ondas em estruturas que apresentem combinações de meios convencionais e/ou metamateriais, particularmente os metamateriais onde tanto a permissividade quanto a permeabilidade são simultaneamente negativos. Em alguns casos à simulação de tais estruturas representa um grande desafio em virtude da grande demanda computacional requerida. Uma forma eficiente de se contornar este problema é a utilização de técnicas de divisão de operador, com destaque para a técnica implícita das direções alternadas (ADI), já amplamente explorada nos domínios do tempo e da freqüência, e mais recentemente a técnica localmente unidimensional (LOD). A técnica LOD é utilizada com destaque neste trabalho, onde pela primeira vez esta foi empregada em um método de propagação de feixe de ângulo largo em diferenças finitas no domínio da freqüência, o qual foi denominado por LOD FD-BPM. O passo seguinte foi estender sua aplicação para o domínio do tempo, sendo a primeira abordagem empregada em um método de propagação de onda em diferenças finitas no domínio do tempo, denominado por LOD TD-WPM. Em seguida, a técnica LOD foi aplicada ao método FDTD resultando em um formalismo implícito, denominado LOD-FDTD, o qual apresenta uma maior eficiência computacional do que o tradicional ADI-FDTD. Estas abordagens apresentaram uma excelente eficiência computacional em virtude da possibilidade de utilização de passos de tempos maiores do que o permitido pela condição de estabilidade de Courant-Friedrich-Levy (CFL), além de serem incondicionalmente estáveis como conseqüência da aplicação do esquema de Crank-Nicolson (CN). A restrição do método LOD-FDTD, referente à sua precisão de apenas primeira ordem no tempo, foi contornada com o uso do esquema de divisão de operadores conhecido como Strang splitting (SS), resultando no método de segunda ordem no tempo LOD-FDTD-SS. Os métodos FDTD, ADI-FDTD, LOD-FDTD e LOD-FDTD-SS foram também implementados com base no modelo de Drude com perdas, possibilitando, assim, uma modelagem adequada de meios metamateriais. Outra contribuição importante deste trabalho foi à implementação da condição de contorno split PML no formalismo LOD-FDTD para a simulação de problemas eletromagnéticos abertos. / This work focuses on developing efficient numerical methods, both in time and frequency domains, for modeling wave propagation in structures that present conventional media and/or metamaterial media combinations, particularly the metamaterials where both permeability and permittivity are simultaneously negative. In some cases, the simulation of such structures represent a great challenge, due to the great computational requirements. An efficient way of solving this problem is the usage of operator splitting techniques, specifically the alternate direction implicit (ADI) technique, already explored both in time and frequency domains, and recently the locally one-dimensional (LOD) . This work dedicates special attention to the LOD technique, where, for the first time, this one was applied in a finite difference frequency domain wide-angle propagation method, which was denominated LOD FD-BPM. The next step was to extend its application to the time domain, the first approach was used in a finite difference time domain wave propagation method, denominated LOD TD-WPM. Next, the LOD technique was applied to the FDTD method, resulting in an implicit formalism, denominated LOD-FDTD, which presents a better computational efficiency than the traditional ADI-FDTD. These approaches present an excellent computational efficiency, due to the possibility of using greater time steps than those permitted by the Courant-Friedrich-Levy (CFL) stability condition, being unconditionally stable as a consequence of applying the Crank-Nicolson (CN) scheme as well. The LOD-FDTD method restriction, referring to its first order accuracy in time, was circumvented by using the operator division scheme known as Strang splitting (SS), resulting in a second order time method LOD-FDTD-SS. The FDTD, ADI-FDTD, LOD-FDTD and LOD-FDTD-SS methods were also implemented with a lossy Drude model, making, this way, possible an adequate metamaterial media modeling. Another important contribution of this work was the implementation of the split PML contour condition in the LOD-FDTD formalism for the simulation of open electromagnetic problems.

Au cours de la dernière décennie, l’usage intensif des herbicides en agriculture a provoqué plusieurs crises sanitaires et environnementales. La recherche de nouveaux herbicides bio-inspirés est donc devenue une urgence, en particulier afin de réduire les risques de pollution. Les porphyrines, naturellement présentes dans les végétaux, sont des molécules photosensibles. En présence d’oxygène, leur photo-activation conduit à la production d’Espèces Réactives de l’Oxygène capables d’induire la mort cellulaire. Ce principe utilisé en thérapie photodynamique peut être transféré aux plantes, par exemple à l’aide de porphyrines chargées. Nous avons étudié les propriétés physicochimiques (absorption UV-Visible, émission de fluorescence, photo-stabilité et production d’EROs) ainsi que les effets sur des cellules de tabac TBY-2 d’une série de porphyrines chargées. Pour étudier les mécanismes d’action des porphyrines en tant qu’herbicides, ces molécules doivent être tracées et localisées dans la plante. Dans ce but, nous avons synthétisé des porphyrines liées de manière covalente à un marqueur fluorescent par plusieurs bras espaceurs ; ces derniers ont été choisis grâce à une étude en modélisation moléculaire de leur flexibilité conformationnelle. Les propriétés photo-physiques de ces nouvelles dyades ont été étudiées expérimentalement et théoriquement. / Over the past decade, intensive use of herbicide in agriculture has caused several sanitary and environmental problems. Finding new bio-inspired herbicides preventing pollution has appeared crucial. Naturally present in plants, porphyrins are photosensitive. In the presence of oxygen, their photo-activation leads to production of Reactive Oxygen Species, which induce cell death. Already used in Photodynamic Therapy, this effect can be used to plant. In that purpose, a series of charged porphyrins (commercial and synthesized) were selected, and their physicochemical properties (e.g. UV-Vis absorption, fluorescence emission, photostability, ROS production) as well as their effects on TBY-2 (Tobacco Bright Yellow) cells were evaluated. Second, localizing molecules in plants is mandatory to understand mechanisms of the herbicide action. In this context, porphyrins were covalently grafted to a fluorescent marker, by a series of spacers that were chosen according to a preliminary molecular modeling evaluation of their conformational flexibility. The new dyads obtained were thoroughly studied both theoretically and experimentally for their photophysical properties.

Les travaux théoriques réalisés dans le cadre de la thèse nous ont permis d’étudier en détail, sur la base de méthodes DFT, TD-DFT et ab initio les propriétés structurales, électroniques et spectroscopiques de deux classes de molécules, les composés carbonyles hydrures des métaux de transition de la 1re et 3me rangée (Mn, Re) et les complexes cyclométalants phenyl pyridine de l’iridium. L’accent a été mis plus particulièrement sur les effets de couplage spin-orbite sur les spectres d’absorption électronique de ces molécules. La quantification de ces effets a permis de montrer que seuls les spectres électroniques des complexes possédant un centre métallique de la 3me rangée des métaux de transition (Re, Ir) étaient modifiés par la correction spin-orbite en perturbation. Le caractère des états, MC ou MLCT, la proximité des états singulets et triplets sont les facteurs qui influencent fortement l’interaction spinorbite entre états excités. Un effet remarquable observé pour le complexe du rhenium est le décalage important du spectre d’absorption vers le rouge du à l’éclatement de l’état triplet le plus bas. Dans ce cas l’effet de couplage spinorbite doit être pris en compte pour obtenir un spectre plus proche de l’expérience. Un effet spin-orbite déjà observé sur d’autres systèmes est l’augmentation de de la densité d’états par éclatement des états triplets et la diminuation des force d’oscillateur qui se répartissent sur ces états pour aboutir à des spectres d’absorption électronique plus étendus et moins intenses. L’étude menée sur les complexes d’iridium pour lesquels les spectres expérimentaux sont particulièrement mal résolus, montre un accord remarquable entre ceux-ci est les spectres d’absorption théoriques TD-DFT. Cependant les effets de fonctionnelle peuvent jouer un rôle important sur la qualité des spectres. Pour ces molécules les calculs ab initio n’ont pu aboutir au-delà du niveau CASSCF. Les états excités sont très délocalisés dans ces molécules et il est difficile de décrire au même niveau d’approximation les différents types d’états MLCT, LLCT, MC, LMCT... Dans la plupart des cas les fonctionnelles B3LYP et PW91 donnent des résultats satisfaisants pour les complexes d’iridium. Les éclatements spin-orbite des états électroniques triplets peuvent être supérieurs à 1500 cm-1 dans les complexes possédant un centre métallique de la 3me rangée des métaux de transition. / The theoretical work of the thesis have allowed us to study in detail, on the basis of DFT methods, TD-DFT and ab initio structural, electronic and spectroscopic properties of two classes of molecules, carbonyl compounds, hydrides transition metals of the 1st and 3rd row (Mn, Re) and complex cyclométalants phenyl pyridine iridium. The focus was specifically on the effects of spin-orbit coupling on the electronic absorption spectra of these molecules. The quantification of these effects showed that only electronic spectra of the complexes with a metal center of the 3rd row transition metals (Re, Ir) were modified by correcting spin-orbit perturbation. The character states, MC or MLCT, the proximity of singlet and triplet states are the factors that strongly influence the spin-orbit interaction between excited states. A remarkable effect observed for the rhenium complex is the large shift of the absorption spectrum to the red of the bursting of the lowest triplet state. In this case the effect of spin-orbit coupling must be taken into account to get closer to the experience spectrum. A spin-orbit effects already observed on other systems is to increase the density of states per burst and triplet states as decreasing the oscillator strength which fall on these statements lead to absorption spectra electronic broader and less intense. The study of the iridium complexes for which experimental spectra are particularly poorly resolved, shows a remarkable agreement between them is the theoretical absorption spectra of TDDFT. However, the functional effects can play an important role in the quality of the spectra. For these molecules ab initio calculations do not reach beyond the CASSCF level. The excited states are delocalized in these molecules and it is difficult to describe the same level of approximation the different types of states MLCT, LLCT, MC, LMCT ... In mostcases the functional B3LYP and PW91 give satisfactory results for the iridium complexes. The spin-orbit explosions electronic triplet states may be higher than 1500 cm-1 in complex with metal center 3rd row transition metals.

Les emballages alimentaires existent depuis la nuit des temps, depuis que l'homme transporte des aliments solides ou liquides. Comme tous les matériaux destinés à entrer au contact des aliments, le bois peut être une source de contaminations chimiques et/ou biologiques, il est donc soumis au règlement (CE) 1935/2004 du parlement européen. Cependant en France, la réglementation spécifique « bois » date de novembre 1945. Elle définit les espèces autorisées pour le contact alimentaire. Il existe également une note d'information « bois » de l'agence sanitaires française « DGCCRF » qui détaillent quelques phénomènes de migration entre le bois et l'aliment mais elles sont très peu développées. L'objectif de cette thèse est d'étudier les différents facteurs qui influencent la migration des composés organiques du bois après un contact alimentaire afin de développer une méthodologie d'analyse simple applicable par les industriels de l'emballage. A l'échelle locale, ce projet innovant apporte une réponse auprès des autorités sanitaires françaises et auprès de la filière française emballages bois et palettes. Et fournira des éléments nécessaires pour la mise à jour de la fiche « matériau bois n°2012-93 » et permettront aux industries agroalimentaires d'avoir à disposition une méthode d'analyse de référence. / Food packaging has existed for millennia; ever since man wished to transport solid or liquid foods that were gathered previously. As in the case most materials, wood could be a source of contamination by chemical or biological products. To date, there are no studies available that assess the migration potential of wood components in to food. Food in contact with materials, like wood, is subject to the European Regulation (EC) 1935/2004. In contrast to other materials, there is no specific directive for wooden food contact packaging. In France, the only specific regulation concerning "wood" dates from November 1945 and is very underdeveloped. This thesis aims to study various factors that influence the migration of organic compounds from wood to food when in direct or indirect contact with one another. The final outcome will be a simple methodology that can be applied to industrial packaging. At the national level, this innovative project is in response to the needs of both the French health authorities and the French wood packaging industry. And provide the information necessary to update the information contained in "wood material No. 2012-93” which will, in turn, give the food industry an analytical method and a point of reference.

L'objectif de ce travail de thèse est l'élaboration d'une photodiode organique (OPD) destinée à être intégrée dans un biocapteur. Ce travail s'inscrit dans le cadre plus général de l'étude et de l'amélioration de composants organiques impliqués dans des microsystèmes de détection visant à surveiller la pollution de l'eau. Le besoin d'évaluation et de suivi de la qualité de l'eau suscite un grand intérêt pour des systèmes de détection portables de polluants ayant une réponse rapide et de faible coût. Le principe de la mesure repose sur la détection des variations de fluorescence de micro-algues en présence de substances toxiques. Excitées grâce à une diode électroluminescente (LED) bleue, les algues vont émettre un signal de fluorescence dont l'intensité, modifiée en présence de polluant (Diuron), est détectée par l'OPD optimisée. Le signal de fluorescence à détecter étant très faible, l'OPD idéale doit avoir un faible courant d'obscurité et une grande sensibilité. Cela passe par un choix judicieux des matériaux semi-conducteurs organiques (OSC) entrant dans l'élaboration de la couche active du composant. Pour accompagner le choix des matériaux, il est intéressant d'explorer leurs propriétés physico-chimiques tout en essayant de rationaliser les mécanismes mis en jeu au sein de ces matériaux lorsqu'ils sont utilisés dans l'élaboration d'OPD (phénomènes d'absorption de photons, mécanismes de transport de charges, et pertes associées aux recombinaisons de charges). Cette thèse s'articule autour de deux axes. Le premier axe consiste en une étude théorique qui vise à comprendre et à maitriser l'échange des charges à l'échelle nanométrique par des caractérisations optiques et des calculs de chimie quantique basés sur des méthodes DFT et TD-DFT. L'étude sur un système modèle (le P3HT) a permis d'établir un protocole de calcul très prometteur pour l'étude des propriétés de matériau d'intérêt, en particulier le PTB7. Le second axe est un volet à caractère expérimental. L'élaboration, la caractérisation et l'optimisation d'OPD à base de PTB7 : PC60BM a permis de concevoir un biocapteur algal apte à détecter le Diuron à des concentrations de l'ordre du nanomolaire. / The aim of this thesis is to develop an organic photodiode (OPD) designed to be integrated into a biosensor. It is part of the broader framework of studying and improving organic components involved into devices devoted to water pollution monitoring. The need for such portable, fast-response, low-cost microsystems is of great interest. The measurement is based on the fluorescence detection of micro-algae under toxic substances exposure. The excited algae, under a blue light emitting diode (LED), will emit a fluorescence signal whose intensity, modified because of pollutant exposure (Diuron), is detected by the OPD. Since the fluorescence signal is very weak, the ideal OPD must have a low dark current and a high sensitivity. To achieve this performance, a judicious choice of organic semiconductor materials (OSC) used for the OPD is required. In addition, it is interesting to investigate their physico-chemical properties by rationalizing the mechanisms involved in the active layer (photon absorption phenomena, charge transport mechanisms, and losses associated with charge recombinations). This thesis is based on two axes. The first one consists in a theoretical study of the charge exchanges at a nanoscale. This have been done by both optical characterizations and quantum chemistry calculations based on DFT and TD-DFT methods. Calculations were performed on a model system (P3HT) thus providing the basis for a very promising computational protocol for studying the properties of materials of interest, for instance PTB7. The second axis concerns the experimental study of the OPD based on PTB7:PC60BM. We have developed, characterized and optimized an OPD guarantying the detection of algal fluorescence without and with Diuron at about nanomolar concentrations.

L’évaluation du risque liée à l’utilisation des pesticides pour les invertébrés du sol est aujourd’hui réalisée à l’aide de l’espèce modèle E. fetida via l’utilisation de tests ecotoxicologiques standardisés (ISO et OCDE) sur la mortalité ou la reproduction. Ces deux points mériteraient d’être révisés puisque (i) l’espèce modèle est rarement présente dans les agroécosystèmes où les pesticides sont majoritairement utilisés, (ii) les tests réalisés sont peu réalistes et leur analyse statistique de type ad hoc ne permet aucune extrapolation dans le temps ou à des niveaux d’organisation supérieurs. Ainsi, une nouvelle espèce modèle a été proposée: Aporrectodea caliginosa. De plus, dans l’objectif d’analyser les effets ecotoxicologiques des pesticides sur cette espèce, un modèle bioénergétique a été proposé et calibré. Ensuite, les effets écotoxicologiques de deux formulations commerciales de pesticide, couramment utilisées en Europe, ont été évalués sur l’ensemble du cycle de vie (mortalité, comportement, reproduction, croissance). Les données de croissance ont été analysées à l’aide du modèle bioénergétique couplé à un modèle toxicocinétique. Ces analyses ont apporté une compréhension mécanistique des effets et ont permis l’estimation de valeurs seuils (les concentrations sans effet, CSE), indépendantes du temps d’exposition. Enfin, dans un objectif d’évaluation intégrée de l’usage des pesticides, il a été mis en évidence que la présence des vers de terre atténuait les effets des pesticides sur les communautés microbiennes des sols, responsables de la dégradation de la matière organique. L’ensemble des résultats pourra être utilisé, au-delà de la thèse, pour calibrer un modèle de dynamique des populations spatialisé de type individu centré (IBM). Ce type de modèle pourra être utilisé en évaluation du risque, pratiquée par les industriels et les agences d’évaluation. / Pesticide risk assessment for soil invertebrates is currently performed using the earthworm model species Eisenia fetida through the use of standardized ecotoxicological tests (ISO and OECD) on mortality or reproduction. These two points should be revised since (i) the model species is rarely found in agroecosystems where pesticides are used, (ii) the tests performed are unrealistic and their statistical analysis does not allow any extrapolation in time or at higher organizational levels (population). Thus, after a thorough reading of the literature, a new model species has been proposed: Aporrectodea caliginosa. In addition, in order to analyze the ecotoxicological effects of pesticides on this species, an energy-based model has been calibrated. Then, the ecotoxicological impacts of two commercial pesticide formulations, commonly used in Europe, were assessed on the entire life cycle (mortality, behavior, reproduction, growth). The growth data were analyzed with the energy-based model coupled with a toxicokinetic model. These analyzes provided a mechanistic understanding of the effects and the estimation of non-time-dependent threshold values (The no effect concentrations, NEC). Finally, for the purpose of an integrated pesticide risk assessment, it has been demonstrated that earthworms mitigate pesticide effects on soil microbial activity, involved in the soil organic matter degradation. All of the results are intended to be used, beyond the thesis, for the calibration of a spatialized population dynamics model with an Individual-based model approach (IBM). This model could be use in risk assessment, as performed by industrials and risk-assessment agencies.

Sökhundar är ett viktigt verktyg som används av polis och tullverksamhet, men deras detektionsmetodik är inte helt känd. En substans doftprofil är en viktig aspekt i sökhundars detektion, men de är svåra att forska på kemiskt då det finns en diskrepans mellan koncentration och bidrag till doftprofilen. Målet med den här forskningen var att öka förståelsen för sökhundars detektionsmetodik i relation till adsorberade föreningar på damm, samt hur marijuanas doftprofil skiljer sig från doftprofilen av damm som kontaminerats med marijuana. Citron och lime utnyttjades som modellsystem och bitar av deras skal analyserades även direkt. Terpener och terpenoider var de främsta komponenterna av intresse. Forskningen hade ett tvåfaldigt tillvägagångssätt och inkluderade termisk desorption gaskromatografi masspektrometri (TD-GC/MS) samt sökhundsanalys i form av urvalsövningar. Kontorsdamm och köpt standarddamm i storleken av luftburna partiklar (PM) med en aerodynamisk diameter av cirka 10 µm kontaminerades med marijuana, citron, lime och en cannabis-terpenmix i exsickatorer i 1, 3, samt 7 dagar. En sekundär kontaminering med marijuana utfördes också, där dammprovet som kontaminerats med marijuana i 1 dag användes för att vidare kontaminera nya damm- och PM-prover, och dammprov togs även i förvaringsskåp för packade illegala droger. Från TD-GC/MS analysen av laborativ kontaminering av marijuana detekterades totalt 25 föreningar av intresse i dammprovet, och 57 i PM-provet. Från TD-GC/MS analysen av citron framkom det att fler monoterpener (C10H18) än sesquiterpener (C15H24) detekterades i direktanalysen av citronskal, och det motsatta i analysen av de kontaminerade damm och PM-proverna. Utgående från detta är det troligt att doftprofilerna från ren marijuana samt marijuana kontaminerad på damm eller PM också skiljer sig åt. Sökhundarna markerade dock på båda proverna som kontaminerats med marijuana under 1 dag med stor säkerhet, och vissa markerade även på prover med kortare kontamineringstid och proverna från förvaringsskåpet. Inga eller få föreningar av intresse detekterades med TD-GC/MS i vissa av de prover som hundarna markerade på, vilket exemplifierar att hundarna har en högre sensitivitet vilket försvårar forskningen kring doftprofiler som hundarna kan detektera. Användningen av sökhundsanalys på dammprover som tagits från platser av intresse kan vara en möjlig metod för att detektera marijuana, och eventuellt även andra illegala substanser. / Detection dogs are an important tool utilized by police forces and customs, but their method of detection is not fully known. The odor profile of a substance is of major importance during dog detection, but they are difficult to research chemically due to the disconnection between concentration and contribution to the odor profile. The purpose of this research was to increase the knowledge regarding the mechanism of detection dogs in relation to adsorbed components on dust, as well as of how the odor profile of marijuana differs to that of dust contaminated with marijuana. Lemon and lime were utilized as model systems and pieces of peel were analyzed directly. Terpenes and terpenoids were the main compounds of interest. The research consisted of a dual approach, utilizing both thermal desorption gas chromatography mass spectrometry (TD-GC/MS), and detection dog analysis in the form of selection exercises. Office dust and bought particulate matter (PM)-like standard dust with an aerodynamic diameter of about 10 µm was contaminated with marijuana, lemon, lime, and a cannabis terpene mix in desiccators for 1, 3, and 7 days. A secondary marijuana contamination was also conducted, where the 1-day dust sample contaminated with marijuana was used to contaminate new dust and PM samples, and dust samples were also taken in storage units of packaged illicit drugs. From the laboratory contaminated samples with marijuana, a total of 25 compounds of interest were detected by TD-GC/MS from the dust samples, and 57 from the PM samples. From the direct TD-GC/MS analysis of lemon peel, it was evident that more monoterpenes (C10H18) than sesquiterpenes (C15H24) were detected, and the contrary was found for the lemon contaminated dust and PM samples. This entails that the odor profiles of marijuana as is and adsorbed on dust or PM is also likely to differ. Still, the detection dogs were able to detect the dust and PM samples which had been co-stored with marijuana for 1 day, and some also alerted to a few of the secondary contaminated marijuana samples as well as the samples from marijuana storages. None or only a few compounds of interest were detected by TD-GC/MS in some of the samples the detection dogs alerted to, which highlights the higher sensitivity of detection dogs, and thus the difficulty of chemically researching odor profiles the dogs can detect. All in all, detection dog analysis of dust collected at scenes of interest may be a viable method to detect marijuana, and perhaps other illicit drugs.

Depuis la fin des années 80 et l'avènement de la femto-chimie nous pouvons sonder la dynamique nucléaire à l’œuvre au cours de réactions chimiques à l'échelle de la femtoseconde. Plus récemment, la production d'impulsions lasers attosecondes isolées permet d'atteindre une résolution temporelle plus grande encore. Par elle, il devient possible de sonder la dynamique d'origine purement électronique induite par photo-excitation, et notamment photo-ionisation. Dans ce contexte, avec le développement des techniques de spectroscopie résolue en temps, il est important de disposer d'approches théoriques fiables aidant à l'appréhension de résultats toujours plus nombreux dans ce domaine. La tâche et néanmoins rendue difficile par le caractère profondément multi-électronique des processus en jeu. Traiter de tels effets précisément requiert une grande puissance de calcul, ce qui a limité les études disponibles aujourd'hui à de petits systèmes. Au cours de cette thèse, j'ai tenté d'expliquer les résultats d'une expérience de type "pompe-sonde" (UVX-IR) sur molécule de Caféine menée par une équipe de collaborateurs à l'Institut lumière matière. J'ai utilisé pour cela une méthode basée sur la théorie de la fonctionnelle de la densité dépendante du temps, la TD-DFTB dont le coût numérique réduit par rapport à cette dernière permet des calculs sur de gros systèmes en temps raisonnable. J'y présente une étude du paysage énergétique de la Caféine ainsi que le résultat de 2 approches distinctes pour simuler l'ionisation de ce composé. La première, l'approximation de l'ionisation soudaine cosiste à retirer "à la main" un électron à l'une des orbitales Kohn-Sham occupées du système neutre et ne tient pas compte du champ laser. La seconde à recours à un potentiel imaginaire (ou CAP - Complex Absorbing Potential) pour simuler la perte d'electrons, et tiens explicitement compte du champ laser / Since the advent of femtochemistry, at the end of 1980's, we are able to probe the nuclear dynamics underlying chemical reactions down to the scale of a femtosecond. More recently, the production of isolated attosecond pulses allows to reach an even bigger temporal resolution. It is now possible to probe the ultrafast electronic dynamics following a photo-excitation. In this context, with the developpement of time-resolved spectroscopy techniques, it is important to have reliable theorectical approaches in order to apprehend the increasing number of results in this field. This task is made difficult by the intrinsic multi-electronic nature processes at play. The precise treatment of such effects requires a considerable computing power, and have thus limited the availables studies to relatively small systems. In this thesis, I tried to explain the outcome of a "pump-probe" (XUV-IR) experiment on Caffeine molecule realized by our collaborators at the Insitut Lumière Matière. To do so, I used a method based on density functional theory, the TD-DFTB, which lower numerical cost with respect to TD-DFT allows calculation on bigger compounds. I present in the document a study of the energetical landscape of Caffeine, and 2 approaches to simulate ionization. The first one, the so called sudden-ionization approximation consist to retrieve "by hand" an electron from the occupied Kohn-Sham orbitals of the neutral system without taking the laser field into account. The other one is based on the introduction of a complex absorbing potential (CAP) to account for electron loss and take explicitely the laser field into account.

O câncer de pele se apresenta como um sério problema de saúde pública mundial, sendo incidente nos cinco continentes. As ações relacionadas à prevenção dessa doença envolvem, entre outras coisas, a utilização de protetores solares e a educação em saúde. Em virtude do aumento do número de indivíduos com câncer de pele a cada ano, é de grande valor estudos de entendimento e desenvolvimento de filtros solares melhores e mais seguros. Os produtos utilizados com a finalidade de proteger a pele dos raios solares ultravioletas (UV) possuem em sua composição filtros solares, que podem ter ação física, refletindo e dissipando a radiação UV; ou ação química, absorvendo a radiação UV. Os filtros químicos podem apresentar absorção em UVB (290-320 nm), UVA (320-400 nm) ou em ambas as faixas, sendo considerados de amplo espectro. . Dentre as várias classes de compostos com perfil de filtro solar UVB, os cinamatos destacam-se por apresentarem boa eficácia e excelente custo-benefício. A aplicação de cálculos teóricos tornou-se indispensável no planejamento de fármacos e nos estudos de mecanismo de ação de moléculas bioativas, visto a diminuição de tempo e custos em pesquisa e desenvolvimento. O desenvolvimento de métodos quânticos robustos, como o TD-DFT, permitiu a simulação de propriedades experimentais in silico, tais como espectros de RMN e UV. Diante deste panorama, aplicamos tal método na simulação de espectros UV para os cinamatos com perfil de filtros solares. Realizou-se uma busca do melhor funcional para simulação dos espectros, na qual se determinou que os funcionais B3LYP e B3P86 apresentaram melhores resultados quando comparados ao espectro experimental do composto p-metoxicinamato de etilexila determinado em metanol. Foram simulados os espectros de UV para sete compostos derivados do ácido cinâmico, os quais apresentaram λ máximo próximo a 310 nm, como descrito na literatura. Observou-se que a energia média para que ocorra a principal transição eletrônica, de HOMO para LUMO, é de 3,95 eV. O método mostrou-se adequado para a determinação de espectros UV para a classe dos cinamatos e pode ser utilizado na busca de novos compostos dessa classe a serem empregados como filtros solares. / Skin cancer presents itself as a very serious world public health problem, being incident all over the five continents. Using sunscreen and receiving health education, among other factors, are related to prevent the disease. The number of people with skin cancer increases every year, therefore, studies for better knowledge and development for better and safer sunscreens are crucial. Products used with the intention to protect the skin from ultraviolet sunrays (UV) are partially composed by sunscreen, which may lead to two different reactions, a physical reaction, that reflects and ceases the UV radiation; or a chemical reaction, that absorbs the UV radiation. Chemical filters may present absorption in UVB (290-320 nm), UVA (320 400 nm) or in both, which is considered as broad spectrum. Among the various types of compound forms with sunscreen UVB profile, cinnamates stand out for presenting good efficiency and excellent cost-benefit. The application of theoretical calculations became essential for drug design and bioactive molecules action mechanism studies, considering time saving and costs in research and development. The development of robust quantum method, such as TD-DFT allowed the simulation of experimental properties in silico, like RMN and UV spectra. Given this overview, this method was applied to simulate UV spectra of cinnamates with sunscreen profile. A search was done to define the best functional to simulate all spectrum, where the functionals B3LYP and B3P86 showed the best results when compared to experimental spectra of the compound ethylhexyl methoxycinnamate determined in methanol. An UV spectrum simulation for seven compounds derived from cinnamic acid showed maximum wavelength around to 310 nm, as described in the literature. It was observed that the average energy for the main electronic transition, HOMO to LUMO, is 3,95 eV. The method proved to be adequate for the determination of UV spectra for cinnamate class and it can be used as a tool on the search for new compounds from this class to be used as sunscreen.

Neste trabalho estudamos o espectro de absorção da clorofila d, incluindo os efeitos do solvente metanol, utilizando a Teoria do Funcional da Densidade Dependente do Tempo em combinação com o método s-QM/MM. Diferentes abordagens para a descrição do meio solvente, que vão desde o modelo contínuo polarizável até a inclusão de moléculas explícitas do solvente, são utilizadas. Observamos que a inclusão do solvente desloca o espectro, em relação ao calculado em vácuo, para o vermelho. A inclusão de 20 moléculas explícitas de metanol e 880 representadas como as cargas pontuais do seus átomos para a descrição do meio solvente foi a que melhor concordou com os valores experimentais. Mediante cálculos de mecânica quântica obtivemos para o complexo composto por a molécula de clorofila d e apenas uma de metanol explícita um deslocamento do átomo de magnésio da clorofila d em relação ao anel de 0,31 Å. Mediante a analise da função de distribuição radial de pares obtida da simulação clássica comprovamos que esse átomo de magnésio é penta-coordenado. Além disso, é usada uma estrutura simplificada da clorofila d baseado na localização dos orbitais moleculares participantes das transições eletrônicas com o objetivo de diminuir o custo computacional dos cálculos de mecânica quântica. Os espectros calculados para a clorofila d não apresentaram diferenças significativas com os calculados para a simplificação proposta. Como complementação o espectro Raman da clorofila d isolada é calculado mediante DFT e alguns dos modos normais são caracterizados. / In this work we study the absorption spectrum of chlorophyll d, including the effects of the solvent methanol, using the Time Dependent Density Functional Theory in combination with the method s-QM/MM. Different approaches for the description of the solvent medium, ranging from the polarizable continuum model to the inclusion of explicit solvent molecules, are used. We note that the inclusion of solvent shifts the spectrum, relative to that calculated in vacuum, to the red side of the spectrum. The inclusion of 20 explicit molecules of methanol and 880 represented as point charges of their atoms for the description of the solvent medium was the one that best agreed with the experimental values. By quantum mechanics calculations we obtained for the complex composed of the molecule of chlorophyll d and only one explicit methanol molecule a displacement of the magnesium atom of chlorophyll d in relation to the ring of 0,31 Å. By means of the analysis of the radial distribution function obtained from the classic simulation we can see that this atom of magnesium is penta-coordinated. In addition, a simplified structure of chlorophyll d is used based on the location of the molecular orbitals involved in the electronic transitions in order to reduce the computational cost of quantum mechanics calculations. The spectra calculated for chlorophyll d did not show significant differences with those calculated for the proposed simplification. As a complement the Raman spectrum of isolated chlorophyll d is calculated by DFT and some of the normal modes are characterized.