Le travail suivant est consacré d'une part à l'emploi du calix[4]arène comme une plate-forme organisatrice de principes actifs pour la conception de nouvelles prodrogues. Ce concept a été développé avec des substances antibactériennes ou antivirales, choisies comme modèles. Les conjugués calixarène - anti-infectieux ainsi synthétisés sont amphiphiles et insolubles dans l'eau. Leur comportement interfacial a été étudié via l'interface eau-air, mime d'une interface hydrophile-hydrophobe physiologique, à l'aide de la technique des films monomoléculaires de Langmuir. Nos résultats indiquent que ces prodrogues étalées à l'interface eau-air peuvent libérer leurs principes actifs dans la sous-phase. La méthodologie développée pour ces études de réactivité interfaciale pourrait à l'avenir être appliquée à d'autres prodrogues à base de calix[4]arène. Un second projet a concerné le trifluoroacétate de tétra-p-(guanidinoéthyl)-calix[4]arène (CX1). Ce composé présente des propriétés antibactériennes à large spectre, couplées à une faible toxicité cellulaire. Nos travaux ont visé à mieux comprendre son mode d'action, lié à une perturbation des parois bactériennes, par une approche physico-chimique. La technique de Langmuir a donc été employée afin d'étudier les interactions entre le CX1 et des films monomoléculaires de phospholipides étalés à l'interface eau-air, utilisés comme modèles de membrane bactérienne. Nos résultats nous ont permis de proposer un mode d'organisation des membranes bactériennes sous l'influence du CX1. Nous avons ainsi apporté des précisions sur son mécanisme d'action qui pourraient être utiles dans le développement de nouveaux calixarènes antibactériens / This work begins with utilization of the calix[4]arene macrocycle as organizing platform of anti-infectious molecules shaped as prodrug. The concept has been explored using antibacterial (nalidixic acid) and antiviral (aciclovir, ganciclovir) molecules, chosen as models. The calixarene - anti-infectious conjugates synthesized have amphiphilic structure and are insoluble in aqueous media. Their interfacial behavior was studied via the air-water interface, considered as mimic of biological hydrophilic-hydrophobic interfaces, using Langmuir monolayers technique. Our results indicate that calixarene-based prodrugs spread at the air-water interface are able to release anti-infectious molecules into the subphase. The original methodology employed for interfacial reactivity studies could be applied to further calixarene-based prodrugs. A second project concerns the trifluoroacetate salt of tetra-p-(guanidinoethyl)-calix[4]arene (CX1). CX1 is antibacterial, active against various Gram-positive and Gram-negative bacteria, with low eukaryotic cell toxicity. The aim of our work was to get more insight in the mechanism of action of CX1, involving bacterial wall disruption, by a physico-chemical approach. The Langmuir monolayers technique was employed in order to study interactions between CX1 and phospholipid monolayers spread at the air-water interface, used as models of bacterial membranes. Our results led us to propose a particular reorganization mode of bacterial membranes upon interactions with CX1. This proposal gives more understanding in the mechanism of biological activity of CX1, and could be helpful in developing new antibacterial calixarene derivatives

<p></p><p></p><p>The unprecedented properties of 2D materials such as graphene and MoS2 have been researched extensively [1,2] for a range of applications including nanoscale electronic and optoelectronic devices [3–6]. Their unique physical and electronic properties promise them as the next generation materials for electrodes and other functional units in nanostructured devices. However, successful incorporation of 2D materials into devices entails development of high resolution patterning techniques that are applicable to 2D materials. Patterning at the sub-10 nm scale is particularly of great interest as the next technology nodes require patterning of (semi)conductors and insulators at 7 nm and 5 nm scales for nanoelectronics. It will also benefit organic photovoltaic cells as phase segregation of p/n-type semiconducting polymers on 2D electrodes at length scales smaller than the typical exciton diffusion length (10 nm)</p> <p>is expected to improve the charge separation efficiency [7].</p><br><p></p><p></p><p>Characterizing locally modulated properties of non-ovalently functionalized 2D materials requires high-resolution imaging techniques capable of extracting measurements of various physical/chemical properties. One such method is scanning probe microscopy (SPM) [18–21]. In Chapter 1, we present a brief review of SPM modalities, some of which are used to characterize interfacial properties, such as conductivity and local contact potential differences that can be modulated by amphiphilic assemblies [17, 22]. Atomic force microscopy (AFM) is one of main techniques that we use to determine topography. All imaging in this work were performed in attractive AC mode [23,24] in order to minimize disruption to the self-assembly of the amphiphiles by the scanning tip.</p><br><p></p><p></p><p>One challenge of using SAMs for locally modulated functionalization is that the proximity to the nonpolar interface can modify the behavior of the functionalities present on the surface in conjunction with the steric hindrance of 2D molecular assemblies. For instance, ionizable functional groups, one of the strongest local modulators of surface chemistry, undergo substantial pKa shifts (in some cases, > 5 units) at nonpolar interfaces, limiting their ability to ionize. In order to apply molecular assembly to create 2D chemical patterns, we needed to design alternative structures that can avoid such penalties against the intrinsic properties of functionalities present in the assemblies. Among amphiphiles, we observed that the chiral centers of phospholipids have the potential of elevating the terminal functional group in the head from the surface for improved accessibility. We refer to this type of assembly as a ’sitting’ phase. Chapter 2 describes sitting phase assembly of phospholipids; the projection of the terminal functionality allows it to maintain solution phase-like behavior while the dual alkyl tails provide additional stabilizing interactions with the substrates. Given the diversity of phospholipid architecture [25], the sitting phase assembly suggests the possibility of greatly diversifying the orthogonality of the chemical patterns, allowing highly precise control over surface functionalities.</p><br><p></p><p></p><p>While a variety of methods including drop-casting [26–28] and microcontact printing [29] have been used previously by others for noncovalent assembly of materials on the surface, they mostly address patterning scale in the sub-μm range. Here, we utilize Langmuir-Schaefer(LS) transfer, which has been historically used to transfer standing phase multilayers [30], and lying-down domains of PCDA at < 100 nm scales in the interest of molecular electronics [14, 31–33], as our sample preparation technique. LS transfer is remarkable in that the transferred molecules relinquish their pre-existing interactions in the standing phase at air-water interface to undergo ∼ 90◦ rotation and assemble into the striped phase on a substrate. This introduces the possibility of modulating local transfer rate across the substrate by manipulating local environment of the molecules. Thus, LS transfer has the potential to offer spatial control over the noncovalent chemical functionalization of the 2D substrate, essential in device applications.</p><br><p></p><p></p><p>In Chapter 3 and 4, We make comparative studies of various experimental factors such as surface pressure, temperature and molecular interactions that affect the efficiency of LS conversion. Considering the energetics of the transfer process, we predicted that the rate of transfer from the air-water interface to the substrate should be the highest from the regions around defects, which would be the energetically</p> <p>least stable regions of the Langmuir film [34, 35]. In Langmuir films, two phases of lipid assemblies—liquid expanded (LE) and liquid condensed (LC)—often coexist at the low surface pressures (< 10 mN/m) used for sample preparation. Hence, we hypothesized that the microscale structural heterogeneity of Langmuir films could be translated into microscale patterns in the transferred film on HOPG. We compare the transfer rates between LE and LC phases and investigate the impacts of physical conditions during LS transfer such as temperature, packing density, dipping rate and contact time to conclude that local destabilization of Langmuir films leads to increased transfer efficiency. (Chapter 3)</p><p><br></p><p></p><p>As in the case of lipid membranes that reorganize routinely based on the structure of the constituent molecules [36–38], the structure of Langmuir films is strongly dependent on the molecular structures of the constituent molecules [39–43]. Accordingly, we expected the molecular structures/interactions to provide additional control over the LS transfer process. In Chapter 4, we compare domain morphologies and the average coverages between three single chain amphiphiles and two phospholipids, each</p><p></p><p> </p><p>of which contain hydrogen bonding motifs of varying strengths. We show that by influencing the adsorption and diffusion rates, molecular architecture indeed influences LS conversion efficiency and subsequent assembly on the substrate. The presence of strong lateral interactions limits transfer and diffusion, forming vacancies in the transferred films with smaller domain sizes while weaker intermolecular interactions enabled high transfer efficiencies.</p><p></p><p><br></p><p></p>

Dans le domaine du photovoltaïque organique, il y a un effort continu pour améliorer l'efficacité des dispositifs. Afin d'atteindre cet objectif, il est nécessaire d'évaluer les caractéristiques qui influencent leur performance. Bien que les films minces de polymères conjugués (dérivés de polythiophène et polymères à faible bande interdite) aient été largementétudiés pour des applications dans des cellules photovoltaïques, peu d'études concernent l'influence de la nanostructuration des films dans de tels dispositifs. Dans ce contexte, l'objectif général de ce travail était d'analyser l'influence de la technique de dépôt de couches minces de dérivés de polythiophène dans des dispositifs photovoltaïques organiques. Le technique de dépôt de Langmuir-Schaefer (LS) a été comparée à celle de spin-coating, plus fréquente. Les films de polythiophène ont été caractérisés par des mesures de transport électrique (courant-tension, photoconductivité, voltampérométrie cyclique et spectroscopied'impédance), spectroscopies optique (UV-visible et fluorescence) et des techniquesmorphologiques (à force atomique et techniques de microscopie à angle de Brewster, etprofilométrie). A partir des mesures électriques à courant continu, il peut être observé que lesfilms LS sont plus conducteurs que ceux obtenus par spin-coating. D’un point de vuemorphologique, il s’avère que la technique de dépôt influence la performance du dispositifphotovoltaïque, en raison de l'organisation et de la nanostructuration fournies par la techniquede la LS. Une étude préliminaire a également été réalisée sur des films de polymères à faiblebande interdite à base de cyclopentadithiophène, réalisés par la technique de Langmuir-Blodgett. / In the area of organic photovoltaics, there is a continuous effort to improve the efficiency of the devices. In order to reach this goal, it is necessary to evaluate the characteristics that influence their performance. Although thin films of conjugated polymers (polythiophene derivatives and low bandgap polymers) have been widely investigated for applications in photovoltaic devices, few studies relate the influence of the nanostructuring of the films in such devices. In this context, the general objective of this work was to analyze the influence of deposition technique of thin films of polythiophene derivatives in organic photovoltaic devices. The Langmuir-Schaefer (LS) technique was compared to the more common spin-coating. The polythiophene films were characterized by electrical transport measurements (current vs. voltage, photoconductivity, cyclic voltammetry and impedance spectroscopy), optical spectroscopy (UV-visible and fluorescence) and morphologicaltechniques (atomic force and Brewster angle microscopies, and perfilometry). From the direct current electrical measurements, it could be observed that the LS films are more conducting than the spin-coating ones. From the morphologic point of view, the deposition technique revealed itself to influence on the photovoltaic device’s performance, due to the organization and nanostructuring provided by the LS technique. Preliminary studies were also undertaken on thin films made of low bandgap polymers based on cyclopentadithiophene by using the Langmuir-Blodgett technique. / Na área de fotovoltaicos orgânicos há um esforço contínuo no aumento da eficiência dos dispositivos. Para alcançar esse objetivo, é necessária a avaliação das características que influenciam seu desempenho. Embora filmes finos de polímeros conjugados (derivados do politiofeno e polímeros de baixo bandgap) tenham sido amplamente estudados para aplicação em dispositivos fotovoltaicos, são encontrados poucos estudos investigando a influência da nanoestruturação dos filmes nestes dispositivos. Dentro deste contexto, o objetivo geral deste trabalho foi analisar a influencia da técnica de deposição de filmes finos de derivados do politiofeno em um dispositivo fotovoltaico orgânico. Para isto utilizamos a técnica de Langmuir-Schaefer (LS) em comparação à técnica spin-coating comumente utilizada. Os filmes de politiofeno foram caracterizados por medidas de transporte elétrico (corrente vs. tensão, fotocondutividade, voltametria cíclica e espectroscopia de impedância), espectroscopia óptica (UV-visível e fluorescência) e técnicas morfológicas (microscopias de força atômica e de ângulo de Brewster, e perfilometria). Através das medidas elétricas em corrente contínua observou-se que os filmes LS apresentam maior condutividade elétrica quando comparados com filmes spin-coating. Do ponto de vista morfológico, a técnica de deposição utilizada mostrou ter influencia no desempenho do dispositivo fotovoltaico, devido à organização e nanoestruturação provida pela técnica LS. Estudos preliminares foram também realizados em filmes finos de polímeros de baixo bandgap baseados em ciclopentaditiofeno usando a técnica de Langmuir-Blodgett.

Dans un contexte de forte demande en carburants, la diversification des charges pétrolières et la sévérité des normes actuelles sur les carburants conduisent à des modifications des unités industrielles de raffinage en vue de leur optimisation. L’approche proposée dans cette thèse consiste à améliorer la description des cinétiques des réactions d’hydrotraitement des gazoles pour pouvoir prédire les effets de changements de conditions opératoires et de charge dans un simulateur du procédé industriel. La cinétique a été étudiée pour 7 charges de compositions initiales différentes sur catalyseur commercial CoMo/Al2O3 pour des températures comprises entre 320°C et 380°C à 45MPa de pression. La méthodologie adoptée a permis de balayer une gamme de soufre final allant de 5000 ppm jusqu’à quelques ppm correspondant à l’HDS ultra-profonde. Un réacteur parfaitement agité continu (Mahoney-Robinson) a été utilisé pour mesurer les vitesses de réaction. Des techniques analytiques (Sulf UV, CPG-SCD, CPG-NCD, HPLC) ont été mises au point pour quantifier les espèces soufrées, azotées et aromatiques présentes dans les gazoles. L’influence de H2, H2S, des familles de réactivité a pu ainsi être observée. Un modèle cinétique de forme Langmuir-Hinshelwood à deux sites (voies hydrogénante et désulfuration directe) pour l’HDS des espèces soufrées individuelles a été établi. Il intègre 188 paramètres cinétiques pour 33 composés et a donné des résultats satisfaisants. L’H2S est le composé le plus inhibiteur pour la voie DDS et les composés di- et tri-aromatiques pour la voie d’hydrogénation. Enfin, un modèle pour l’HDA et l’HDN des différentes familles identifiées est également proposé. / In the context of a growing demand for fuel, the diversity of feedstocks and the severity of the actual specifications have led to major modifications in the industrial refinery processes for their optimization. The approach of this thesis consists in improve the kinetic descriptions of the hydrotreatment reactions of gas oils to predict the effects of operating conditions and gas oil nature changes in an industrial process simulator. The kinetic has been studied for 7 gas oils with different initial compositions over a CoMo/Al2O3 commercial catalyst for 320-380°C range of temperature and 45MPa total pressure. The methodology used in this work has permitted to cover a total sulfur range from 5000ppm to few ppm corresponding to the deep HDS. A continuous stirred tank reactor (Mahoney-Robinson) has been used to measure the reactions rates. Analytic technics (Sulf UV, CPG-SCD, CPG-NCD, HPLC) have been set to quantify the sulfur, nitrogen and aromatic species present in the gas oils. The influence of H2, H2S, individual sulfur species or reactivity groups of sulfur species, groups of aromatic and nitrogen compounds have been observed. A bi sites kinetic model (hydrogenation and direct desulfurization pathways) for the HDS of the individual sulfur species resulting from a Langmuir-Hinshelwood mechanism has been established with 188 parameters for 33 compounds and has given satisfying results. The H2S is the most inhibiting compound for the direct desulfurization and the di- and tri-aromatics for the hydrogenation. At last, a model for the HDA and HDN of the different identified families is presented as well.

Les travaux présentés dans ce mémoire portent sur la synthèse et à l'étude physico-chimique et biologique de nouveaux tensioactifs fluorés pour la conception de vecteurs non-viraux ayant un intérêt dans le domaine de l'interférence ARN. Dans un premier temps, en se basant sur l'expérience du laboratoire et sur l'étude des vecteurs existants, nous avons proposé un design moléculaire pour la synthèse d'amphiphiles bicaténaires géminis et monocaténaires. La synthèse a été réalisée par des méthodes simples et offre de bons rendements. Les tensioactifs préparés comportent des chaines grasses fluorées pour leurs propriétés spécifiques et des motifs polyaminés ou oxyéthylènique comme partie polaire. Dans un deuxième temps, nous nous sommes intéressés aux propriétés physico-chimiques de ces familles de molécules. Les tensioactifs géminis sont insolubles dans l'eau et forment des monocouches de Langmuir stables à l'interface air/eau. L'étude de ces monocouches révèle que l'organisation à l'interface est fortement dépendante du bras espaceur entre les deux chaines grasses fluorées. Les molécules monocaténaires quant à elles sont solubles dans l'eau, montrent une forte activité de surface et forment spontanément des vésicules en solution. Nous avons ensuite étudié l'interaction entre les produits synthétisés et un petit monobrin d'ADN de 23 bases. Une interaction relativement forte a été mise en évidence pour la plupart des molécules et nous avons essayé de relier la structure de ces molécules aux propriétés physico-chimiques et biologiques observées. Enfin, des tests préliminaires de viabilité cellulaire ont été effectués sur des cellules issues de poumon humain et montrent une bonne viabilité cellulaire pour des concentrations d'utilisation clinique classiques et une bonne stabilité dans le temps. Ces travaux laissent entrevoir un bon potentiel de vectorisation pour ces tensioactifs fluorés mais cela nécessite encore des études complémentaires comme la caractérisation complète des complexes formés avec l'ADN ainsi que des tests de toxicité cellulaire avant le moindre essai de transfection. / The work presented in this paper focus on the synthesis and characterization of physico-chemical properties of original fluorocarbon surfactants for obtaining nanovectors models to determine the qualifications required for efficient transport of oligonucleotides in the field of RNA interference. Building on the extensive work reported in the literature and the laboratory expertise in the field of fluorinated amphiphiles, we are interested in the synthesis of two major families of compounds. One corresponds to compounds of Géminis type with two fluorocarbon chains, two polar head groups derived from carboxylic acids and an oxyethylene or polyamine spacer arm. The structure of these compounds is conducive to the formation of stable Langmuir films that used to study interactions with the oligonucleotide. The second family corresponds to monocatenar counterparts who spontaneously self-assembled in vesicles, that is to say 3D models nanovectors. The characterization of the behavior at the air / water interface or in solution of these different molecules in the presence and absence of oligonucleotide allowed us to establish a number of relationships between molecular structure, physicochemical properties and complexation of the oligonucleotide. Preliminary tests of cell viability were performed on cells from human lung and have shown good cell viability at conventional clinical used concentrations and good stability over time. These studies suggest good potential for vectorization of these fluorinated surfactants but that still requires further study as the full characterization of complexes formed with DNA as well as tests for toxicity before testing cell transfection.

Os plasmas frios tem sido largamente utilizados em processosde corrosao e deposicao de materiais em diversas areas tecnologicas. O entendimento dos mecanismos fisico-quimicos determinantes desses processos e sempre procurado para melhorar a qualidade e eficiencia dos mesmos. Esses mecanismos sao fortemente dependentes das propriedades dos plasmas utilizados, sendo portanto, sempre necessario proceder-se uma caracterizacao das propriedades macroscopicas e microscopicas com vistas a oferecer uma descricao mais clara do processo de interacao do plasma com a superficie material sob processo. Neste trabalho uma camara dupla foi especialmente construida para formacao simultanea de dois plasmas. Em uma delas - em pirex - foi produzido um plasma excitado por acoplamento indutivo de radio fraquencia (plasma fonte) de maneira a operar tanto no modo E quanto no modo H. Este plasma difunde-se para o interior de uma segunda camara, metalica, a qual possui imas permanentes distribuidos na superficie, dando origem a um plasma quiescente sob confinamento multidipolo magnetico (plasma alvo). Estudaremos os parametros basicos destes plasmas, como exemplo, potencial de plasma, temperatura e densidade de eletrons. O comportamento destes parametros com a pressao de trabalho, posicao da sonda no interior da camara e potencia eletrica sera investigado e interpretacoes serao apresentadas com base nos mecanismos de descarga RF. Tais parametros serao determinados atraves da tecnica de sonda de Langmuir autocompensada.Atraves de valores experimentaisdas variaveis eletricas da bobina de inducao (tensao, corrente e defasagem entre as mesmas) foi possivel determinar os parametros eletromagneticos (campo eletrico, campo magnetico, densidade de corrente, densidade de potencia e condutividade) da descarga utilizando-se o metodo sugerido por J.W. Denneman. Neste modelo a descarga e considerada um transformador cujo primario e a bobina de inducao (5 voltas) da descarga, e o secundario e o plasma produzido,o qual e equivalente a uma bobina de apenas uma volta. Posteriormente, foi feita uma analise espectral do plasma atraves de uma sonda magnetica (bobina de Rogowski).

Neste trabalho foi produzido um plasma através da focalização da radiação de um laser CO2-TEA pulsado sobre um alvo sólido de ferro, colocado no interior deuma câmara de vácuo. Apresentamos resultados experimentais referentes às medidas de temperatura de íons, temperatura de elétrons, densidade de elétrons e velocidade de expansão do plasma. Utilizou-se a técnica de sonda de Langmuir para medida da densidade e temperatura de elétrons. Um analisador eletrostático multi-grade foi especialmente construído para a medida da função de distribuição de energia de íons. A velocidade de expansão do plasma foi inferida a partir do tempo de vôo do plasma. É mostrado que os resultados experimentais são consistentes com um modelo de expansão livre de um plasma em vácuo.

No description available.

Electric propulsion for spacecraft has become increasingly commonplace in recent decades as designers take advantage of the significant propellant savings it can provide over traditional chemical propulsion. As electric propulsion systems are designed for very low thrust, the operational time required over the course of an entire mission is often quite long. The two most common types of electric thrusters both use hollow cathodes as electron emitters in the process of ionizing the propellant gas. These cathodes are one of the main life-limiting components of both ion and Hall thrusters designed to operate for tens of thousands of hours. Failure often occurs as a result of erosion by sputtering from high-energy ions generated in the plasma. The mechanism that is responsible for creating these high-energy ions is not well understood, and significant efforts have gone into characterizing the plasma produced by hollow cathodes. This work uses both a Langmuir probe and an emissive probe to characterize the variation of the plasma potential and density, the electron temperature, and the electron energy distribution function in the near plume region of a hollow cathode. The cathode used in this experiment is typical of one used in a 200-W class Hall thruster. Measurements were made to determine the variation of these parameters with radial position from the cathode orifice. Changes associated with varying the propellant and flow rate were also investigated. Results obtained from the cathode while running on both argon and xenon are shown. Two different methods for calculating the plasma density and electron temperature were used and are compared. The density and temperature were not strongly affected by reductions in the propellant flow rate. The electron energy distribution functions showed distinct shifts toward higher energies when the cathode was operated at lower flow rates. The plasma potential also displayed an abrupt change in magnitude near the cathode centerline. Significant increases in the magnitude of plasma potential oscillations at lower propellant flow rates were observed. Ions formed at the highest instantaneous plasma potentials may be responsible for the life-limiting erosion that is observed during long-duration operation of hollow cathodes.

Arsenic contamination in drinking water has been a cause of serious concerns across the United States as well as throughout the world. Over 70 million people in Eastern India, Bangladesh, Vietnam, Taiwan, and Northern China have been victims of arsenic poisoning. The USEPA has classified arsenic as a Class A carcinogen and recently reduced the Maximum Contaminant Level (MCL) in drinking water from 50ppb to 10ppb. The deadline for all the water utilities to meet this level is 23rd January 2006. To meet those drinking water standards, small water utilities need low cost and effective arsenic removal techniques. Natural zeolites such as Chabazite are excellent sorbents for several metallic and radioactive cations. Modifying the zeolite structure can effectively enhance the adsorption capacities of these zeolites for removal of heavy metals. The present work investigates the adsorption capacities of Cuprous and Ferrous treated Chabazite for removal of arsenic. This investigation is a part of a broader project directed at developing an effective pretreatment process that uses modified Chabazite in conjugation with Microfiltration (MF) or Ultrafiltration (UF) for removal of organic and inorganic contaminants. The goal of this research is to determine how well Cuprous and Ferrous treated Chabazite sorbs arsenic in its trivalent and pentavalent state. The other objectives of this research are to examine which modification of the chabazite has the higher removal efficiency of arsenic. This study will also compare arsenic adsorption on the modified zeolites in response to competitive adsorption of various anions present in natural source waters such as sulfates, hydroxides, and chlorides. The potential benefit of this study is to find the most effective treatment of for removal of arsenic species from aqueous solutions. This investigation may provide small water utilities, with a cost effective way for removal of arsenic and thus meet the recommended new regulatory maximum contaminant level (MCL).