<p>U ovoj doktorskoj disertaciji ispitivani su elektroliti na bazi jonskih tečnosti pogodni za<br />primenu u litijum&nbsp; jonskim baterijama. Fizičko-hemijska svojstva binarnih sme&scaron;a<br />jonskih tečnosti sa dicijanamidnim i bis(trifluorometilsulfonil)imidnim anjonima i<br />molekulskih rastvarača ispitana su u celom opsegu molskih udela i na različitim<br />temperaturama. Na osnovu izmerenih gustina, viskoznosti i električne provodljivosti<br />izračunati su različiti fizičko hemijski parametri i diskutavne interakcije između komponenata sme&scaron;a. Ispitana je termička i elektrohemijska stabilnost odabranih<br />elektrolita. Dodatkom litijumove soli u odabrane binarne sme&scaron;e dobijeni su ternarni<br />sistemi koji su okarakterisani u zavisnoti od koncentracije litijumove soli. Odabrani<br />elektroliti upotrebljeni su za&nbsp; ispitivanje performansi litijum&nbsp; jonske ćelije sa anatas<br />TiO2&nbsp; nanotubularnim elektrodama.Cikličnom voltametrijom i galvanostatskim<br />cikliranjem su ispitane performanse ćelije u toku 150 ciklusa punjenja i pražnjenja. Na<br />osnovu ciklovoltametrijskih merenja izračunati su koeficijenti difuzije i energija aktivacije za difuziju.</p> / <p>In this doctoral dissertation, Ion liquid-based electrolytes were tested for use in&nbsp; lithium-ion batteries. The physicochemical properties of binary mixtures of ionic&nbsp; liquids with dicyanamide and bis (trifluoromethylsulfonyl) imide anions and&nbsp; molecular solvents were examined throughout the range of molar proportions and at different temperatures. Based on the measured densities, viscosity and electrical conductivity, various physical chemical parameters and discrete interactions between&nbsp; the components of the mixture are calculated. Thermal and electrochemical stability of selected electrolytes was examined. By addition of lithium salt to the selected binary mixtures, ternary systems were characterized which were characterized by the concentration of lithium salt. The selected electrolytes were used to test the performance of the lithium-ion cell with anatomic TiO2 nanotubular electrodes. Cyclic voltammetry and galvanostatic cycling tested the cell&#39;s performance during the 150 charge and discharge&nbsp; cycles. Based on cyclotoltametric&nbsp; measurements, the diffusion coefficients and activation energies for diffusion were calculated.</p>

Poli(p-fenileno de tereftalamida) (PPTA), usualmente chamado de aramida, é uma fibra polimérica de baixa densidade que possui alta rigidez e resistência à tração, assim como excelente estabilidade térmica e química. Essa fibra é utilizada como reforço em materiais compósitos utilizados nas indústrias aeroespacial e automobilística, em artefatos de proteção balística e de proteção ao corte. No entanto, sua aplicação como reforço em materiais compósitos está limitada por sua baixa afinidade interfacial com matrizes poliméricas, devido a sua superfície lisa e relativamente inerte. Para superar esta desvantagem, diversos tratamentos foram desenvolvidos para modificar a superfície da aramida. Contudo, realizar essa modificação sem diminuir a resistência mecânica da fibra é um grande desafio, assim como desenvolver um método industrialmente viável. Líquidos iônicos (LI) apresentam-se como uma alternativa promissora para a compatibilização da aramida com matrizes poliméricas, devido à possibilidade de ajuste de suas propriedades com a escolha de ânions e cátions específicos. Dessa forma, o objetivo deste estudo é investigar a influência de diferentes LI nas propriedades adesivas entre Kevlar e uma resina epoxídica. Para tanto, as fibras foram submetidas a soluções de etanol e LI imidazólicos (cloreto de 1-n-butil-3-metilimidazólio, cloreto de 1-carboximetil-3-metilimidazólio, metanossulfonato de 1-trietilenoglicol monometil éter-3-metilimidazólio e metanossulfonato de 1-n-butil-3-metilimidazólio) e analisadas por espectroscopia do infravermelho, análise termogravimétrica e microscopia eletrônica de varredura. A resistência mecânica das fibras foi investigada por teste de tração e a interface foi caracterizada em termos de molhabilidade e adesão pelos testes de ângulo de contato e pull-out. Os resultados mostraram um aumento na molhabilidade e na adesão nas fibras tratadas com cloreto de 1- n-butil-3-metilimidazólico, metanossulfonato de 1-trietilenoglicol monometil éter-3- metilimidazólio e metanossulfonato de 1-n-butil-3-metilimidazólio. Dois compósitos laminados foram fabricados com os tecidos comercial e tratado com metanossulfonato de 1- trietilenoglicol monometil éter-3-metilimidazólio. Suas propriedades mecânicas foram aferidas por ensaios de tração e short beam. O compósito feito com o tecido tratado apresentou maior resistência mecânica, módulo e tensão de cisalhamento interlaminar. / Poly(p-phenylene terephthalamide) (PPTA), known as aramid, is a low density polymeric fiber that has high rigidity and exceptional tensile strength, as well as excellent thermal and chemical stability. It is used as reinforcement in composite materials in the aerospace and automobile industry and in ballistic and stab-resistant articles. However, its inferior interfacial affinity towards polymeric matrices due to its smooth surface hampers its use in composite materials, preventing full achievement of its potential as reinforcement. To overcome this drawback, various treatments have been applied to modify the aramid surface. Nevertheless it is a great challenge to introduce this modification without diminishing the fiber mechanical properties and to develop an industrially feasible process. Ionic liquids (IL) might be an alternative as compatibilizer in polymeric matrices reinforced with aramid fibers because of their unique set of physical-chemical properties that can be finely tuned by their chemical structures. Hence, the objective of this study is to investigate the influence of different IL on the adhesive properties between Kevlar and epoxy resin. Kevlar fibers were submitted to solutions of ethanol and imidazolium IL (1-n-butyl-3-methylimidazolium chloride, 1- carboxymethyl-3-methylimidazolium chloride, 1-n-hexadecyl-3-methylimidazolium chloride, 1- triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate and 1-n-butyl-3- methylimidazolium methanesulfonate) and then analyzed by infrared spectroscopy, thermogravimetric analysis and scanning electron microscopy. The mechanical strength of the fibers was analyzed by tensile strength tests and the interface was characterized by contact angle measurements and pull-out tests. There was an increase in wettability and adhesion of the fibers treated with 1-n-butyl-3-methylimidazolium chloride, 1-triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate and 1-n-butyl-3- methylimidazolium methanesulfonate. Two laminated composites were manufactured with commercial and 1-triethyleneglycol monomethyl ether-3-methylimidazolium methanesulfonate treated fabrics and their mechanical properties were measured with tensile strength and short beam test. The composite made with treated fabrics presented higher mechanical resistance, modulus and interfacial shear strength.

<p>U&nbsp; ovoj&nbsp; doktorskoj&nbsp; disertaciji&nbsp; ispitivani&nbsp; su&nbsp; elektroliti&nbsp; na&nbsp; bazi binarnih&nbsp; sme&scaron;a&nbsp; imidazolijumovih&nbsp; jonskih&nbsp; tečnosti&nbsp; i&nbsp; laktona&nbsp; koji su&nbsp; pogodni&nbsp; za&nbsp; primenu&nbsp; u&nbsp; litijum-jonskim&nbsp; baterijama.&nbsp; Fizičkohemijska&nbsp; svojstva&nbsp; binarnih&nbsp; sme&scaron;a&nbsp; jonskih&nbsp; tečnosti&nbsp; na&nbsp; bazi imidazolijum katjona i <em>bis </em>(trifluorometilsulfonil)imidnog anjona i laktona ispitana su u celom opsegu molskih udela i na različitim temperaturama.&nbsp; Na&nbsp; osnovu&nbsp; izmerenih&nbsp; gustina,&nbsp; viskoznosti&nbsp; i električne&nbsp; provodljivosti&nbsp; izračunati&nbsp; su&nbsp; različiti&nbsp; fizičko-hemijski parametri i diskutovane&nbsp; interakcije između komponenata sme&scaron;a. Ispitana&nbsp; je&nbsp; termička&nbsp; i&nbsp; elektrohemijska&nbsp; stabilnost&nbsp; odabranih elektrolita.&nbsp; Na&nbsp; osnovu&nbsp; dobijenih&nbsp; rezultata,&nbsp; prvo&nbsp; je&nbsp; odabran odgovarajući&nbsp; lakton&nbsp; koji&nbsp; je&nbsp; kasnije&nbsp; kombinovan&nbsp; sa&nbsp; jonskim<br />tečnostima&nbsp; na&nbsp; bazi&nbsp; imidazola,&nbsp; koje&nbsp; se&nbsp; međusobno&nbsp; razlikuju&nbsp; u dužini&nbsp; bočnog&nbsp; niza&nbsp; katjona.&nbsp; Na&nbsp; osnovu&nbsp; fizičko-hemijskih svojstava&nbsp; na&nbsp; različitim&nbsp; temperaturama&nbsp; i&nbsp; pri&nbsp; različitim&nbsp; sastavima binarnih&nbsp; sme&scaron;a&nbsp; diskutovan&nbsp; je&nbsp; način&nbsp; organizacije&nbsp; njihovih<br />komponenata.&nbsp; U&nbsp; binarne&nbsp; sme&scaron;e&nbsp; koje&nbsp; su&nbsp; se&nbsp; pokazale&nbsp; kao najperspektivnije&nbsp; sa&nbsp; stanovi&scaron;ta&nbsp; električne&nbsp; provodljivosti, viskoznosti,&nbsp; elektrohemijske&nbsp; stabilnosti&nbsp; i&nbsp; (ne)zapaljivosti&nbsp; dodata je litijumova so. Tako dobijeni ternarni sistemi su okarakterisani<br />u zavisnosti od koncentracije litijumove soli. Odabrani elektroliti upotrebljeni su za ispitivanje performansi litijum-jonske ćelije sa elektrodama&nbsp; na&nbsp; bazi&nbsp; anatas&nbsp; TiO₂&nbsp; nanocevi.&nbsp; Cikličnom voltametrijom&nbsp; i&nbsp; galvanostatskim&nbsp; cikliranjem&nbsp; ispitane&nbsp; su<br />performanse ćelije u toku 350 ciklusa punjenja i pražnjenja. Na osnovu&nbsp;&nbsp; ciklovoltametrijskih&nbsp; merenja&nbsp; izračunati&nbsp; su&nbsp; koeficijenti difuzije jona Li^{&nbsp; +}i energija aktivacije za difuziju.&nbsp; Kombinacijom jonskih&nbsp; tečnosti&nbsp; i&nbsp; laktona&nbsp; moguće&nbsp; je&nbsp; dobiti&nbsp; elektrolite&nbsp; smanjene viskoznosti,&nbsp; povećane&nbsp; električne&nbsp; provodljivosti,&nbsp; povećane<br />termičke&nbsp; stabilnosti&nbsp; usled&nbsp; međusobnog&nbsp; stabilizacionog&nbsp; efekta laktona na imidazolijumove jonske tečnosti.</p> / <p>In&nbsp; this&nbsp; doctoral&nbsp; dissertation,&nbsp; binary&nbsp; mixtures&nbsp; based&nbsp; on&nbsp; imidazolium&nbsp; ionic&nbsp; liquids&nbsp; with&nbsp; lactones&nbsp; were&nbsp; tested&nbsp; for&nbsp; use&nbsp; in lithium-ion&nbsp; batteries.&nbsp; The&nbsp; physicochemical&nbsp; properties&nbsp; of&nbsp; binary&nbsp; mixtures&nbsp; of&nbsp; imidazolium&nbsp; based&nbsp; ionic&nbsp; liquids&nbsp; with&nbsp;<em> bis </em>(trifluoromethylsulfonyl)imide&nbsp; anions&nbsp; and&nbsp; lactones&nbsp; were&nbsp; examined&nbsp; throughout&nbsp; the&nbsp; whole&nbsp; composition&nbsp; range&nbsp; and&nbsp; at&nbsp; different temperatures. Based on the measured densities, viscosity&nbsp; and electrical conductivity, various physical chemical parameters&nbsp; and discrete interactions between the components of the mixture are&nbsp; calculated.&nbsp; Thermal&nbsp; and&nbsp; electrochemical&nbsp; stability&nbsp; of&nbsp; selected&nbsp; binary&nbsp; mixtures&nbsp; were&nbsp; examined.&nbsp; Based&nbsp; on&nbsp; obtained&nbsp; results&nbsp; was&nbsp; selected lactone&nbsp; which is later combined with imidazolium based&nbsp; ionic liquid,&nbsp; differing from each other in the length of the cation. Based&nbsp; on&nbsp; the&nbsp; physico-chemical&nbsp; properties&nbsp; at&nbsp; different&nbsp; temperatures and in the different compositions of binary mixtures, the way of organizing their components is discussed. Lithium salt&nbsp; is added to the binary mixtures that have been shown as the most perspective&nbsp; from&nbsp; the&nbsp; standpoint&nbsp; of&nbsp; electrical&nbsp; conductivity, viscosity,&nbsp; electrochemical&nbsp; stability&nbsp; and&nbsp; (non)flammability.&nbsp; The&nbsp; resulting&nbsp; ternary&nbsp; systems&nbsp; are&nbsp; characterized&nbsp; according&nbsp; to&nbsp; the concentration of lithium salt.&nbsp; The selected electrolytes were used to test the performance of the lithium-ion cell with anatase TiO₂ nanotubular&nbsp; electrodes.&nbsp; Cyclic&nbsp; voltammetry&nbsp; and&nbsp; galvanostatic&nbsp; cycling&nbsp; tested&nbsp; the&nbsp; cell&#39;s&nbsp; performance&nbsp; during&nbsp; the&nbsp; 350&nbsp; charge&nbsp; and discharge&nbsp; cycles.&nbsp; Based&nbsp; on&nbsp; cyclic&nbsp; voltammetric&nbsp; measurements, the&nbsp; Li ⁺ ion&nbsp; diffusion&nbsp; coefficients&nbsp; and&nbsp; activation&nbsp; energies&nbsp; for diffusion&nbsp; were&nbsp; calculated.&nbsp; Combination&nbsp; ionic&nbsp; liquid&nbsp; and&nbsp; lactone could&nbsp; be&nbsp; obtained&nbsp; electrolytes&nbsp; with&nbsp; lower&nbsp; viscosity,&nbsp; higher electrical&nbsp; conductivity,&nbsp; improved&nbsp; thermal&nbsp; stability&nbsp; due&nbsp; to stabilization effect of lactone on imidazolium based ionic liquids.</p>

Neste trabalho, estamos interessados na descrição da estabilidade isomérica de moléculas isoladas e em agregados, assim como em propriedades eletrônicas de agregados moleculares em fase gasosa e estruturas com ligação de hidrogênio em fase líquida. Na primeira investigação, estabilidade isomérica, estudamos a estabilidade relativa dos isômeros "C IND.2v", "C IND.3v" e "C IND.s" da molécula de "AlP IND.3" isolada. Analisamos tanto a estrutura conformacional, quanto a energética dos três isômeros e depois de submetermos as estruturas mais estáveis a cálculos sofisticados de química quântica, extrapolamos os resultados obtidos para as energias dos isômeros ao limite de base completa. Chegamos µa conclusão que o isômero "C IND.3v" é o menos estável dos três investigados, e que os isômeros "C IND.2v" e "C IND.s" apresentam-se como estados quase-degenerados com uma diferença de energia de 'DA ORDEM DE' 1,6 kcal/mol. Ainda pensando na estabilidade isomérica,investigamos os agregados HCN...HOH e "H IND.2"O...HCN, também em fase gasosa. Através de cálculos ab initio obtivemos a estrutura e energética dos dois agregados. Comparamos a energia dos dois agregados depois de obtermos, através de métodos altamente acurados de correlação eletrônica no limite de base completa, e obtivemos que o agregado "H IND.2"O...HCN é o mais estável por 'DA ORDEM DE'1,5 kcal/mol. Na segunda parte de nosso trabalho, investigamos as modificações sofridas em agregados moleculares quando estes são formados em diferentes ambientes, o gasoso e o líquido. Primeiro, analisamos as diferenças nos agregados de pirazina ("N IND.2" "C IND.4" "H IND.4") e água (1:1 e 1:2), através de comparação da estrutura e propriedades eletrônicas obtidas em fase gasosa através de otimização de geometria e em fase líquida, obtidos da simulação computacional Monte Carlo Metropolis. Para as estruturas 1:1 comparamos os resultados nos dois ambientes através da estrutura, energia e momento de dipolo. Para os agregados 1:2 comparamos adicionalmente as contribuições energéticas de muitos corpos e a cooperatividade nos dois ambientes. Todos os resultados nos mostram que os agregados em fase gasosa são cerca de 30% mais estáveis que os agregados do líquido, tanto para os agregados 1:1 quanto para os agregados 1:2. Ao ¯final do trabalho, analisamos as modificações sofridas no espectro eletrônico do formaldeído ("H IND.2"CO) quando este se encontra em ambiente aquoso. Analisamos especificamente o deslocamento da banda de energia referente à transição n- > "'pi'POT.*" deste espectro quando consideramos 1, 2 e 3 moléculas de água solvatando o formaldeído e também quando incluímos toda a primeira camada de solvatação, 18 moléculas de água, todas inclusas explicitamente no cálculo quântico. Adicionalmente, fizemos estimativas para a contribuição da dispersão de London e da relaxação da ligação C=O no deslocamento da banda n- > "'pi'POT.*" do formaldeído solvatado / In this work, we study the isomeric stability of isolated molecules and molecular clusters. We study the change of some electronic properties of molecular clusters in gas and liquid phases. The first application is the relative isomeric stability of isolated AlP3 in C2v, C3v and Cs symmetries. We analyze the conformational structure and the total energy of the three isomers using sophisticated quantum chemistry calculations and using CCSD(T)/cc-pVXZ (X = 2, 3, 4 and 5) level and extrapole to the infinite basis set limit. The locations of the two states on the potential energy hyper-surface are obtained and show that they represent well-defined and stable isomers. We also investigate the HCN...HOH and H2O...HCN clusters in gas phase, using ab initio calculations to obtain the optimized structure of these two molecular clusters. We present a systematic study of the stability of the H2O...HCN and HCN...HOH complexes calculating the binding energy of both systems using the aug-cc-pVXZ basis sets with X=2,3,4 and extending the results to the infinite limit. At the best theoretical level, CCSD(T), the H2O...HCN cluster is more stable than HCN...HOH by ~ 1.5 kcal/mol. In the second part of our work, we investigate the electronic modifications in molecular clusters due to the different environments of these clusters, the gas and the liquid phases. We analyze the pyrazine-water clusters (1:1 and 1:2) obtained in gas and liquid phases and compare the structure and electronic clusters properties. For the 1:1 pyrazine-water clusters we compare the structures, total energy and dipole moments. For the 1:2 pyrazine-water clusters we analyze the many-body contributions to the interaction energy and cooperativity. All results show that the gas phase clusters have interaction energies that are around 30% of the liquid clusters. Finally, we analyze the absorption electronic spectrum of formaldehyde in liquid water. We specifically analyze the shift of the n-pi* electronic transition. We consider 1, 2, 3 and 18 water molecules solvating the formaldehyde, all explicitaly included in the TD-DFT calculations. Additionally, we make estimates of the London dispersion contribution and C=O stretching effects in the shift of the n-pi* electronic transition of formaldehyde in water.

O sistema peróxi-oxalato consiste na reação entre ésteres oxálicos e peróxido de hidrogênio, na presença de um catalisador básico e/ou nucleofílico e de um composto fluorescente com baixo potencial de oxidação (ACT), resultando em uma emissão eficiente de quimiluminescência. O sistema é amplamente utilizado em diversas aplicações analíticas, entretanto, sua aplicação é limitada devido às dificuldades de sua adaptação em meios aquosos. Nesse trabalho foram realizados estudos cinéticos da reação peróxi-oxalato em uma mistura binária de 1,2-dimetóxietano/água (1/1) em tampão fosfato (pH 6, 7 e 8), utilizado-se os ésteres oxalato bis(2,4,6-triclorofenila) (TCPO), oxalato de bis(4- metilfenila) (BMePO) e oxalato de bis(4-nitrofenila) (BNPO). A partir da dependência da constante de velocidade de decaimento da intensidade de emissão (kobs) com a concentração de peróxido de hidrogênio e do tampão fosfato obteve-se evidências da ação do fosfato como catalisador básico específico na reação de TCPO. Porém, os resultados indicam também que na reação de BMePO o fosfato age principalmente como catalisador ácido. A reação peróxi-oxalato (TCPO, H2O2, ACT e imidazol) foi realizada também em meio de 80% de líquidos iônicos. Três líquidos iônicos contendo o cátion 1-butil- 3-metilimidazólio (bmim) com os contra-íons tetrafluroborato, hexafluorofosfato e hexafluoroantimonato foram utilizados obtendo-se valores de kobs maiores em bmimPF6, seguida do meio em bmimBF4e por fim em bmimSbF6. Os rendimentos quânticos determinados alcançaram valores de quase 20% em meio de bmimSbF6, além disso, foram obtidas evidências experimentais de que o mecanismo CIEEL esteja envolvido no passo de quimi-excitação da reação peróxi-oxalato nestes meios / The peroxyoxalate system consists in the reaction of oxalic esters with hydrogen peroxide in the presence of basic and/or nucleofilic catalysts and a fluorescent compound with low oxidation potential (ACT), resulting in efficient chemiluminescence emission. This system is widely utilized in various analytical applications; however, its use is limited due to the difficulties to adapt it to aqueous media. In this work, kinetic studies of the peroxyoxalate reaction were performed in phosphate buffered (pH 6, 7 and 8) binary 1,2-dimethoxyethane/water mixtures (1/1), using the oxalate esters bis(2,4,6-trichlorophenyl) oxalate (TCPO), bis(4- methylphenyl) oxalate (BMePO) and bis(4-nitrophenyl) oxalate (BNPO). Evidence for the action of the phosphate as a specific base catalyst in the reaction of TCPO was obtained from the dependence of the emission decay rate constant (kobs) on the hydrogen peroxide and phosphate buffer concentration. However, the results also indicate that phosphate acts mainly as an acid catalyst in the reaction of BMePO. The peroxyoxalate reaction (TCPO, H2O2, ACT and imidazole) was also performed in 80 % of ionic liquids. Three ionic liquids containing the cation 1-butyl- 3-methylimidazolium (bmim) with contra-ions tetrafluoroborate, hexafluorophosphate and hexafluoroantimonate were used obtaining higher rate constant values for bmimPF6, followed by bmimBF4 media and finally bmimSbF6. The quantum yields determined reached almost 20% in the medium bmimSbF6, additionally, experimental evidence was obtained for the occurrence of the CIEEL mechanism in the chemiexcitation step of the peroxyoxalate reaction in these media

Este trabalho consiste em estudar o comportamento eletroquímico de biomoléculas imobilizadas sobre o eletrodo de carbono vítreo, utilizando materiais biocompatíveis como meios imobilizadores para detecções em meios aquosos. Foram utilizados inicialmente compósitos de hidrogéis capazes de auxiliar a permanência da enzima sobre a superfície do eletrodo e beneficiar a transferência de carga entre a enzima e o eletrodo de trabalho. Para melhorar a resposta eletroquímica do biossensor, também foram estudados métodos que utilizam líquidos iônicos no processo de imobilização da enzima. Deste modo a eletroatividade da enzima foi inicialmente estudada por voltametria cíclica, a fim de evidenciar tal eletroatividade no meio totalmente iônico, como também avaliar o melhor método de imobilização, para futuras aplicações em detecções de analitos. Os líquidos iônicos utilizados são compostos por cátions alquil-imidazol com ânions de natureza orgânica ou inorgânica. Como se sabe os íons que compõem o líquido iônico podem distinguir sua funcionalidade, pois é o tamanho desses íons que influencia na maioria das suas propriedades físico-químicas, tais como hidrofobicidade e viscosidade. / The aim of this work is to study the electrochemical behavior of biomolecules immobilized on a glassy carbon electrode, using biocompatible materials as a way for immobilizing detection in aqueous media. Initially, hydrogels composite were used because they are able to assist the permanence of the enzyme on the electrode surface and they are benefit to the charge transfer between enzyme and electrode surface. To improve the electrochemical response of the biosensor, methods using ionic liquids in the process of immobilization of the enzyme were also studied. Thus the electroactivity of the enzyme was initially analyzed by cyclic voltammetry in order to show that the electroactivity remains in an entirely ionic media, as well as evaluating the best method of immobilization, for future applications in biosensors. The ionic liquids used are composed of imidazole-alkyl cations with anions of organic or inorganic nature. As it is well known, the ions in the ionic liquid can distinguish its functionality, due to the fact that it is the size of these ions that influences most on their physicochemical properties such as hydrophobicity and viscosity.

Les phénomènes électrocinétiques couplés au sein d'un nanocanal sont d'intérêt pour la conversion d'énergie et la production d'électricité reposant sur le mélange contrôlé d'eau douce et d'eau salée aussi appelée "énergie bleue". L'origine des phénomènes est lié à l'interaction avec des parois chargées et au transport d'ions au sein de ce qu'on nomme les couches de Debye. Ce travail vise à une meilleure compréhension de la physique et des phénomènes de transport dans ces couches dans le cadre de solutions confinées dans des nanocanaux.Une instrumentation spécifique a été développée pendant la thèse pour étudier les mécanismes qui gouvernent ces flux couplés. L'idée est de caractériser simultanément le transport de masse et le courant électrique au sein d'un nanocanal soumis à une différence de salinité de pression ou de tension électrique. Ce travail est divisé en trois parties.Dans la première partie, est décrite une cellule conçue pour la mesure et le contrôle de courant et tension électrique en présence de différence de pression ou de salinité au bornes d'un nanopores. L'utilisation de la cellule est illustrer dans le cas d'une membrane nanoporeuse de nafion.La seconde partie est focalisée sur une méthode simple de préparation d'un nanocanal directement connectable à un dispositif macroscopique. Le nanocanal, d'un micromètre de long, présente une géométrie conique, d'angle ajustable, et des extrémités équipées d'électrode déposées par pulvérisation cathodique.La troisième partie, concerne le développement d'une méthode pour la mesure directe de débit jusqu'à 10 pL/min s'écoulant au sein d'un nanocanal. Cette méthode combinée à une caractérisation électrique, pourra être utilisée, en présence de gradient de pression, de tension ou de salinité pour mesurer le débit et le courant électrique au sein d'un nanocanal de manière simultanée et indépendante. / Coupled electrokinetic phenomena within nanochannel are of interest for energy harvestingand production of electricity based on the controlled mixing of river water with sea water known as "blue energy". The origin of the phenomena is related to interaction with charged walls and transport of ions within the so called Debye layer. This work aims at a better understanding of the physics and transport phenomena in this layer associated with solution confined in nanochannel.A specific instrumentation has been developed during this thesis to study the mechanisms governing coupled nanofluics fluxes. The idea is to characterize simultaneously the mass transport within the nanochannel and the electrical current driven through the nanochannel by the application of either salinity difference , pressure difference or voltage difference across the channel. The thesis is divided into three parts.In the first part, a custom made flow cell and experimental conditions to control and measure various fluxes is presented. The capability of cell to measure current or voltage under applied pressure or salinity gradient is presented taking the benefit of commercial nanoporous Nafion membrane.The second part is focused on an easy way of preparation of nanochannel sample in the form of single chip, in which nanochannel is interfaced to micro and macroscopic world. A well-controlled, 1.4µm long nanochannel of conical geometry with a maximum aspect ratio of 10 is fabricated. The minimum apex size of nanochannel achieved here is 50 nm which is about 30 times less than the length of channel. The presence of electrode directly at the interface of nano to micro cavity allow to perform electrical characterization of nanochannel with high precision.The third part of the thesis is devoted to the development of a method for the direct measurement of flow rate as low as 10 pL/min across a single nanochannel. This measurement approach combined with electrical measurement, could be used, in presence of pressure, voltage or salinity gradient, to measure the flow rate and the electrical current across a single nanochannel simultaneously and independently.

L'étude de la dynamique interfaciale des liquides à l'échelle du nanomètre est cruciale pour la compréhension de nombreux phénomènes biologiques et industriels. Pour aborder cette question, nous étudions l'interaction en champ proche d'une sonde et de liquides peu visqueux. La thèse s'articule autour de deux grands axes : le premier s'intéresse à la déformation de l'interface liquide lorsqu'une pointe est approchée et à l'instabilité hydrodynamique du "jump-to-contact" qui en résulte. Le second, plus intrusif, décrit la réponse hydrodynamique d'un liquide soumis à l'oscillation d'un nanocylindre (R ~ 20-100 nm) partiellement immergé. Les mesures sont réalisées par microscope à force atomique (AFM), en mode modulation de fréquence (FM), qui permet de mesurer la force exercée sur la sonde ainsi que les composantes conservatives et dissipatives de l'interaction pointe-liquide. Une première série de mesure est réalisée sur différents liquides modèles avec un AFM couplé à une caméra rapide via un microscope optique inversé. Avant le mouillage de la sonde, les courbes de spectroscopie de force et FM mettent en évidence la déformation de l'interface liquide sur des échelles nanométriques, pour une grande gamme de tailles de sonde (de 10 nm à 30 µm). L'analyse des mesures expérimentales avec le modèle théorique récemment développé par René Ledesma-Alonso permet de déterminer la distance critique dmin en dessous de laquelle l'interface se déstabilise et mouille irréversiblement la pointe ("jump-to-contact"). Un excellent accord est trouvé entre le modèle théorique et les mesures FM. La deuxième série de mesure s'intéresse à l'immersion partielle de pointes AFM cylindriques. Les courbes de spectroscopie FM montrent qu'une certaine quantité de liquide, située dans la couche visqueuse, est entraînée par l'oscillation de la pointe. On mesure simultanément la friction exercée sur la pointe et la masse de liquide ajoutée au système, qui est directement reliée à l'extension du champ de vitesse. Un modèle analytique basé sur la résolution de l'équation de Stokes rend compte quantitativement de l'ensemble des résultats expérimentaux. La dernière série de mesure est réalisée avec des sondes cylindriques spécialement conçues pour l'étude de la dynamique de nanoménisques. Ces sondes comportent des défauts topographiques annulaires dont l'épaisseur varie entre 10 et 50 nm. Les mesures montrent une divergence du coefficient de friction aux petits angles de contact qui est bien reproduite par un modèle théorique basé sur l'approximation de lubrification. La localisation de la dissipation d'énergie au voisinage de la ligne de contact et les propriétés d'ancrage du ménisque sont également discutées. Les expériences originales développées dans cette thèse démontrent ainsi la capacité de l'AFM à étudier quantitativement les liquides à l'échelle nanométrique et ouvrent la voie à une étude systématique des processus de dissipation au sein de liquides confinés, et notamment au voisinage d'une ligne de contact en mouvement. / The study of the interfacial dynamics of liquids, down to the nanometer-scale, is of primary importance in many domains including biological and industrial phenomena. To address those questions, we study the near-field interaction between a probe and low viscous liquids. The present thesis focuses on two aspects. In the first one, we investigate the liquid interface deformation that occurs when a tip is approached and the resulting "jump-to-contact" hydrodynamic instability. The second part is more intrusive as it describes the hydrodynamic response of a liquid under the oscillation of a partly-immerse nanocylinder (R ~20-100 nm). Our measurements are performed with an Atomic Force Microscope (AFM) in the frequency modulation (FM) mode, which allows to measure the force exerted on the probe along with the conservative and dissipative components of the tip-liquid interaction. A first set of measurements is performed on several model liquids with an AFM coupled with a high-speed camera via an inverse optical microscope. Before the probe wetting, the force and FM spectroscopy curves highlight the liquid interface deformation on nanometer scales for a large range of probe size (from 10 nm to 30 µm). The fitting of our experimental measurements with the theoretical model recently developed by René Ledesma-Alonso, enables to determinate the critical distance dmin below which the interface is destabilized and irreversibly wets the tip (jump-to-contact). The theoretical model and the FM measurements were found to be in good agreement. The second set of measurements focuses on the partial immersion of cylindrical AFM tips. The FM spectroscopy curves show that a certain quantity of liquid, located in the viscous layer, is carried off with the tip oscillation. The friction exerted on the tip and the liquid mass added to the system, which is directly linked to the velocity-field extension, were measured simultaneously. An analytical model based on the Stokes equation quantitatively reproduces our experimental results. The last set of measurements is performed with cylindrical probes specially designed for the study of nanomeniscus dynamics. Those probes possess annular topographic defects, whose thickness varies between 10 nm and 50 nm. The measurements show that he measured friction coefficient surges as the contact angle is decreased. This behavior is well described by a developed theoretical model based on the lubrication approximation. Furthermore, the dissipation pattern in the vicinity of the contact line and the anchoring properties are also discussed. The original experiments developed in this thesis demonstrate thus that AFM is a relevant tool for the quantitative study of liquids at the nanoscale. This work paves the way for systematic studies of dissipation processes in confined liquids, and in particular in the vicinity of moving contact lines.

Uma reação relativamente simples vem auxiliando cada vez mais uma variedade de aplicações analíticas na determinação de diversos compostos. A reação peroxioxalato, que produz o fenômeno de quimiluminescência, pode identificar compostos como peróxido de hidrogênio e compostos orgânicos fluorescentes presentes em diferentes meios. O estudo dessa reação em líquidos iônicos utilizados como solvente se torna cada vez mais interessante, por se tratar de solventes verdes, beneficiando assim o meio ambiente. Neste projeto, foi estudado a reação de oxalato de bis(2,4,6-triclorofenila) (TCPO) com peróxido de hidrogênio, em 1,2-dimetoxietano (DME), carbonato de propileno (CP) e misturas binárias de líquido iônico e DME, catalisada por imidazol. Dois líquidos iônicos (LIs) foram utilizados, sendo eles o tetrafluoroborato de 1-butil-3-metilimidazólio (BuMeImBF4) e o tetrafluoroborato de 1-decil-3-metilimidazólio (DecMeImBF4). As misturas binárias foram preparadas com até 50% de sua composição constituída de LI, definindo assim diferentes condições experimentais no estudo da reação, podendo ser aproveitado em futuras aplicações analíticas. Estudos cinéticos mostraram que o imidazol age não somente como catalisador básico mas também nucleofílico, tanto nos solventes orgânicos puros quanto nos meios contendo LI. Nos solventes puros e nas misturas binárias destes com líquidos iónicos determinaram-se os valores das constantes de velocidade observadas (kobs) e os rendimentos quânticos singlete (&#934;S). Os valores de kobs se tornam maiores nas misturas contendo LI em sua composição, entretanto, os valores de &#934;S não sofrem alteração significativa, mostrando uma leve tendência de diminuição. A determinação dos parâmetros de polaridade e viscosidade das misturas binárias DME/LI mostra que ambos aumentam com o aumento da concentração do LI. A baixa sensibilidade dos rendimentos quânticos à composição dos meios DME/LI pode ser entendida por um efeito de composição da viscosidade e polaridade do meio. Enquanto o aumento da viscosidade deve aumentar a eficiência de quimiexcitação, o aumento da polaridade pode levar à diminuição do rendimento devido a separação dos íons radicais envolvidos no passo de quimiexcitação ocorrendo pelo mecanismo CIEEL (Chemically Initiated Electron Exchange Luminescence). De acordo com os estudos realizados, foi demonstrado que a reação peroxioxalato pode ser conduzida em meios contendo líquidos iônicos, favorecendo assim uma maior utilização destes solventes verdes. / A relatively simple chemical reaction has increasingly shown utility in a variety of analytical applications for the determination of various compounds. The peroxyoxalate reaction, which produces the chemiluminescence phenomenon, can be used to identify and quantify several compounds, such as hydrogen peroxide and fluorescent organic compounds in different reaction media. The study of this reaction in media containing ionic liquids is of increasing interest, because of its possible utilization as \"green\", environmental compatible, solvents in analytical assays. In this project, the kinetics of the imidazole catalyzed reaction of bis(2,4,6- trichlorophenyl) oxalate (TCPO) with hydrogen peroxide in 1,2-dimethoxyethane (DME), propylene carbonate (CP) and binary mixtures of ionic liquids and DME, is studied, using the two ionic liquids (LIs) 1-butyl-3-methylimidazolium tetrafluoroborate (BuMeImBF4) and 1- decyl-3-methylimidazolium tetrafluoroborate (DecMeImBF4). The binary mixtures were prepared with up to 50% of their composition consisting of LI, thus, defining different experimental conditions in the study of the reaction, which could be used in future analytical applications. Kinetic studies show that imidazole acts not only as base, but also studied as nucleophilic catalyst, in molecular solvents as well as in LI-containing media. In the binary mixtures studied, the values of the observed rate constants (kobs) and singlet quantum yields (&#934;S) were determined. The kobs values are higher in mixtures containing LIs in their composition, however, &#934;S values do not change significantly, showing only a slight tendency to decrease. The determination of the polarity and viscosity parameters of the binary DME / LI mixtures shows that both increase with increasing LI concentration. The low sensitivity of quantum yields to the composition of the DME / LI media can be understood by a combined medium effect of the viscosity and polarity. While increased viscosity should increase the efficiency of chemiexcitation, increased polarity may lead to decreased quantum yields due to separation of the radical ions involved in the chemiexcitation step occurring by the Chemically Initiated Electron Exchange Luminescence (CIEEL) mechanism. According to the studies, it has been demonstrated that the peroxyoxalate reaction can be conducted in media containing ionic liquids, indicating that analyical assays with the peroxyoxalate reaction migt be performed in these \"green\" solvents.

This paper presents an approach to modeling a binary mixture near a surf ace. The approach used is based on statistical mechanics. The Cluster Variation (CV) method is used to solve an Ising-like model with a cluster size of two (neighboring lattice points). The free energy of the system is expressed in terms of the probabilities of occurrences of particular clusters. The CV method is first developed for a homogeneous system which leads to a set of three non-linear partial differential equations. The surface boundary is then introduced and the CV method is developed for this system which leads to a set of seven non-linear partial differential equations for each layer. In the calculations, the Natural Iteration (NI) method is introduced as a method of solving these non-linear partial differential equations. The steps involved in implementing the NI method are outlined. The number of layers is chosen to be 32. Concentration profiles are calculated for the binary system using the NI method and the results are discussed.