Dissertations / Theses on the topic 'Salt and ion transport'

[Truncated abstract] This study describes the results of a four and a half year investigation examining local regulation of ion transport through pumping epithelial cells. The study focussed on the standard isolated toad skin preparation, made famous by Hans Ussing. Originally, the objective was to perform some simple manipulations on the isolated toad skin, a standard and well-tested epithelial layer, which, according to the literature, was a well-behaved and stable preparation. The purpose of doing these toad skin experiments was to gain familiarity with the experimental techniques, such as measuring the open-circuit voltage (Voc) and the short-circuit current (Isc) across an epithelium. In the process, the experimental information that was obtained was to assist in the development and refinement of a mathematical model of a single pumping epithelial cell . . . Finally, it should be emphasised the toad skin was a convenient tissue model for exploring more general issues such as: (i) how pumping epithelial cells may adjust to changes in the extracellular environment by locally regulating their membrane conductances; (2) how the topology of a cell can influence its function (i.e. the topology can determine whether a cell is optimised for salt transport or water transport). (3) how different cells, with different functions, may be positioned in apposition in a pumping epithelial tissue so that gradients generated by one cell type can be utilised by another. From a broader perspective, it is likely that such issues are also applicable to other pumping epithelia, and ultimately, may assist in understanding how these epithelia function.

[EN] Abstract Introduction Salinity and drought are the most important environmental stress conditions reducing crop yields worldwide and limiting the distribution of wild plants in nature. Soil salinity, especially secondary salinity caused by anthropogenic practices, such as prolonged irrigation, lead to substantial agricultural yield losses, especially in arid and semiarid regions. Drought, caused by reduced water content in the soil, occurs due to disorders in nature's water cycle, chiefly when evapotranspiration exceeds precipitation in a certain area, to the point where soil water reserves can no longer support plant growth. Drought and salt stress trigger the activation of a series of basic stress mechanisms that includes among others, the control of ion transport, exclusion and compartmentalization, as well as the accumulation of compatible solutes ('osmolytes'), and the activation of antioxidant systems. These mechanisms are conserved in all plants, stress tolerant and sensitive alike, and don't necessarily confer tolerance. To decipher those mechanisms and have a better understanding on the contribution of different stress responses to the stress tolerance of a given species, we have carried out comparative studies on the responses to drought and salinity in a number of genetically related taxa with different tolerance potentials. Methodology The experimental approach was mostly based on i) establishing the relative tolerance to water and salt stress in the studied species from their distribution in nature (in the case of wild species) and through the relative inhibition of growth in the presence of stress, and ii) correlating changes in the levels of biochemical 'stress markers' associated to specific response pathways (ion transport, osmolyte accumulation¿) upon stress treatments, with the already established relative tolerance to stress. This strategy proved to be appropriate to distinguish mere general responses to stress from those mechanisms relevant for stress tolerance of the investigated species and cultivars. The work also sheds light on other aspects affected by salt stress, specifically regarding germination and reproductive success or anatomical changes in salt-stressed plants. The expression patterns of the gene NHX1, encoding a vacuolar Na+/H+ antiporter were also studied in the Plantago taxa, as a first step in the full characterisation of this ion transporter, that appears to play an important role in the mechanisms of salt tolerance in this genus. Conclusion The results obtained in this work contribute to a better understanding of general stress tolerance mechanisms in plants, and provides clear insights into the mechanisms conferring tolerance, specifically, to drought and salt stress in some wild species and crops. This work also shed more light on the highly efficient responses to stress in halophytes, plants that could be viewed as nature's answer to the aforementioned adverse environmental conditions via evolution and adaptation. Halophytes can therefore be considered as a suitable source - underutilized at present, in our opinion - of knowledge, genetic resources and biotechnological tools for the needed improvement of stress tolerance in crops.
[ES] Resumen Introducción La salinidad y la sequía son las condiciones de estrés ambiental más importantes, que reducen los rendimientos de los cultivos en todo el mundo y que limitan la distribución de las plantas silvestres en la naturaleza. La salinidad del suelo, especialmente la salinización secundaria causada por prácticas antropogénicas, como la irrigación prolongada, conducen a pérdidas importantes de rendimiento agrícola, especialmente en las regiones áridas y semiáridas. La sequía, provocada por la reducción de contenido de agua en el suelo, se produce debido a alteraciones en el ciclo del agua en la naturaleza, principalmente cuando la evapotranspiración excede la precipitación en un área determinada, hasta el punto que las reservas de agua del suelo ya no pueden soportar el crecimiento de la planta. La sequía y el estrés salino desencadenan la activación de una serie de mecanismos básicos de respuesta, que incluyen entre otros el control del transporte, la exclusión y la compartimentación de iones, así como la acumulación de solutos compatibles ('osmolitos'), y la activación de sistemas antioxidantes. Estos mecanismos están conservados en todas las plantas, tolerantes y sensibles a estrés por igual, y no confieren necesariamente tolerancia. Para descifrar estos mecanismos y conseguir una mejor comprensión de la contribución de diferentes respuestas a estrés a la tolerancia al estrés en una especie dada, hemos llevado a cabo estudios comparativos sobre las respuestas a la sequía y la salinidad, en un número de taxones relacionados genéticamente con diferentes potenciales de tolerancia. Metodología El enfoque experimental se basó principalmente en i) establecer la tolerancia relativa al estrés hídrico y al estrés salino en las especies estudiadas, a partir de su distribución en la naturaleza (en el caso de especies silvestres) y atendiendo a la inhibición relativa de su crecimiento en presencia de estrés, y ii) correlacionar cambios en los niveles de 'marcadores bioquímicos de estrés' asociados a vías específicas de respuesta (transporte de iones, acumulación de osmolitos ...) inducidos por los tratamientos de estrés, con la tolerancia relativa a estrés de las plantas, previamente establecido. Esta estrategia ha resultado ser apropiada para distinguir meras respuestas generales a estrés de los mecanismos relevantes para la tolerancia a estrés de las especies y cultivares investigados. El trabajo también arroja luz sobre otros aspectos afectados por el estrés salino, específicamente en relación con la germinación y el éxito reproductivo, o cambios anatómicos en las plantas tratadas con sal. También se estudiaron los patrones de expresión del gen NHX1, que codifica un antiportador vacuolar Na+/H+, en las especies de Plantago, como un primer paso en la caracterización completa de este transportador de iones, que parece desempeñar un papel importante en los mecanismos de tolerancia a sal en este género. Conclusión Los resultados obtenidos en este trabajo contribuyen a una mejor comprensión de los mecanismos generales de tolerancia al estrés en plantas, y proporcionan ideas claras sobre los mecanismos que confieren tolerancia, en concreto, a la sequía y al estrés salino, en algunas especies silvestres y cultivadas. Este trabajo también arroja más luz sobre las respuestas a estrés altamente eficientes en halófitas, plantas que podrían ser vistas como la respuesta de la naturaleza a las condiciones ambientales adversas antes mencionadas, a través de la evolución y la adaptación. Por lo tanto, las halófitas pueden ser consideradas como una fuente adecuada - infrautilizada en la actualidad, en nuestra opinión - de conocimiento, recursos genéticos y herramientas biotecnológicas para la necesaria mejora de la tolerancia al estrés en plantas cultivadas.
[CA] Resum Introducció La salinitat i la sequera són les condicions d'estrès ambiental més importants, que redueixen els rendiments dels cultius a tot el món i que limiten la distribució de les plantes silvestres en la naturalesa. La salinitat del sòl, especialment la salinització secundària causada per pràctiques antropogèniques, com la irrigació perllongada, condueixen a pèrdues importants de rendiment agrícola, especialment en les regions àrides i semiàrides. La sequera, provocada per la reducció de contingut d'aigua en el sòl, es produeix a causa d'alteracions en el cicle de l'aigua en la naturalesa, principalment quan la evapotranspiració excedeix la precipitació en un àrea determinada, fins al punt que les reserves d'aigua del sòl ja no poden suportar el creixement de la planta. La sequera i l'estrès salí desencadenen l'activació d'una sèrie de mecanismes bàsics de resposta, que inclouen entre uns altres el control del transport, l'exclusió i la compartimentació d'ions, així com l'acumulació de soluts compatibles ('osmolits'), i l'activació de sistemes antioxidants. Aquests mecanismes estan conservats en totes les plantes, tolerants i sensibles a estrès per igual, i no confereixen necessàriament tolerància. Per a desxifrar aquests mecanismes i aconseguir una millor comprensió de la contribució de diferents respostes a estrès a la tolerància a l'estrès en una espècie donada, hem dut a terme estudis comparatius sobre les respostes a la sequera i la salinitat, en un nombre de taxons relacionats genèticament amb diferents potencials de tolerància. Metodologia L'enfocament experimental es va basar principalment en i) establir la tolerància relativa a l'estrès hídric i a l'estrès salí en les espècies estudiades, a partir de la seua distribució en la naturalesa (en el cas d'espècies silvestres) i atenent a la inhibició relativa de el seu creixement en presència d'estrès, i ii) correlacionar canvis en els nivells de 'marcadors bioquímics d'estrès' associats a vies específiques de resposta (transport d'ions, acumulació d'osmolits ...) induïts pels tractaments d'estrès, amb la tolerància relativa a estrès de les plantes, prèviament establert. Aquesta estratègia ha resultat ser apropiada per a distingir meres respostes generals a estrès dels mecanismes rellevants per a la tolerància a estrès de les espècies i conreus investigats. El treball també llança llum sobre altres aspectes afectats per l'estrès salí, específicament en relació amb la germinació i l'èxit reproductiu, o canvis anatòmics en les plantes tractades amb sal. També es van estudiar els patrons d'expressió del gen NHX1, que codifica un anti-portador vacuolar Na+/H+, en les espècies de Plantago, com un primer pas en la caracterització completa d'aquest transportador d'ions, que sembla exercir un paper important en els mecanismes de tolerància a sal en aquest gènere. Conclusió Els resultats obtinguts en aquest treball contribueixen a una millor comprensió dels mecanismes generals de tolerància a l'estrès en plantes, i proporcionen idees clares sobre els mecanismes que confereixen tolerància, en concret, a la sequera i a l'estrès salí, en algunes espècies silvestres i conreades. Aquest treball també llança més llum sobre les respostes a estrès altament eficients en halòfites, plantes que podrien ser vistes com la resposta de la naturalesa a les condicions ambientals adverses abans esmentades, a través de l'evolució i l'adaptació. Per tant, les halòfites poden ser considerades com una font adequada - infrautilitzada en l'actualitat, en la nostra opinió - de coneixement, recursos genètics i eines biotecnològiques per a la necessària millora de la tolerància a l'estrès en plantes conreades.
Al Hassan, M. (2016). Comparative analyses of plant responses to drought and salt stress in related taxa: A useful approach to study stress tolerance mechanisms [Tesis doctoral no publicada]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/61985
TESIS

La plupart des batteries Li-ion aujourd’hui utilisent des électrolytes à base de LiPF6 un sel de lithium connu pour son instabilité chimique au-delà de 60°C car il se dégrade en libérant PF5 et LiF. En présence de traces d’eau il génère en plus des composés oxyfluorophosphorés et du HF qui peut être dommageable à la fois pour les performances et pour le vieillissement de l’accumulateur. Plusieurs sels sont candidats au remplacement de LiPF6, notamment ceux basés sur les anions fluorosulfonylamidures et les anions de Hückel. Ce travail concerne l’étude des propriétés physico-chimiques et de transport des électrolytes à base de 4,5-dicyano-2- (trifluoromethyl)imidazolide de lithium (LiTDI) et bis(fluorosulfonyl)amidure de lithium (LiFSI) pour une utilisation au sein d’accumulateurs de type Li-ion. Dans ce travail il a d’abord été montré que LiTDI n’est que faiblement dissocié dans les mélanges de carbonates d’alkyles utilisés dans les batteries Li-ion tels que le binaire (EC/DMC) ce qui limite sa conductivité. Pour pouvoir remédier à cet inconvénient, une étude des phénomènes de solvatation et d’associations ioniques a été menée et a conduit à proposer un mélange ternaire de solvants (EC/GBL/MP) dans lequel LiTDI est plus dissocié. Le mélange ternaire proposé améliore à la fois les propriétés de transport et les caractéristiques thermiques de l’électrolyte sans compromettre le domaine de stabilité chimique et électrochimique. Enfin, le nouvel électrolyte EC/GBL/MP contenant LiTDI, a été testé en accumulateurs dans les conditions opératoires usuelles (régime C/10 et température ambiante) et sévères (régime 10C et des températures allant de -20 °C à 60 °C). Le problème de corrosion de l’aluminium de LiFSI a aussi été pris en compte. Un électrolyte prometteur à base d’un mélange LiTDI/LiFSI montrant de meilleures performances que chaque sel utilisé séparément dans EC/DMC a été présenté. Les conclusions de cette thèse prouvent que LiTDI ou LiFSI peuvent être utilisés comme sels de lithium dans les électrolytes pour accumulateurs Li-ion
Most of the Li-ion batteries used in electrical devices contain a solution of LiPF6 in alkylcarbonate solvents with the risk of releasing PF5 at elevated temperatures and HF in the presence of water. Several salts are candidates for the replacement of LiPF6, including those based on fluorosulfonylamides and Hückel anions. This work concerns the study of physicochemical and transport properties of lithium 4,5-dicyano-2- (trifluoromethyl)imidazolide (LiTDI) and lithium bis(fluorosulfonyl)amide (LiFSI) based electrolytes and their use in Li-ion battery. First it was revealed that LiTDI is only weakly dissociated in alkylcarbonate mixtures used in Li-ion batteries such as EC/DMC limiting its conductivity. To overcome this disadvantage, a study of the solvation phenomena and of ionic association within the electrolytes was conducted. This study led to a ternary mixture of solvents (EC/GBL/MP) in which LiTDI is more dissociated. This new solvent mixture improves both the transport properties and the thermal stability of the LiTDI based electrolyte without compromising its chemical and electrochemical stability. Finally, the new LiTDI in EC/GBL/MP electrolyte was tested in NMC/graphite batteries under normal (C/10 rate and room temperature) and severe (10C rate and temperatures varying from - 20 ° C to 60 °C) operating conditions. The aluminium corrosion problem encountered by LiFSI based electrolytes was taken into account and a LiTDI/LiFSI salt mixture based electrolyte showing promising results was presented. The findings of this thesis show that LiTDI or LiFSI can be used as lithium salts in electrolytes for Li-ion batteries

La symbiose ectomycorhizienne, répandue dans les forêts tempérées et boréales, se base sur des échanges nutritionnels entre la plante hôte et des champignons du sol. Ce mutualisme améliore la nutrition minérale et en eau de plantes ligneuses à travers des mécanismes encore méconnus. Ce manuscrit de thèse présente l’ensemble des systèmes de transport membranaire du champignon ectomycorhizien Hebeloma cylindrosporum identifié à partir du génome séquencé, avec un accent sur les gènes dont l’expression est induite en symbiose avec son hôte naturel, le pin maritime (Pinus pinaster). Ces données aideront à focaliser les futures recherches sur les gènes qui sont induits par la symbiose. Le champignon H. cylindrosporum améliore la nutrition potassique de son hôte en situation de carence. Cette étude est axée sur trois canaux ioniques qui peuvent être impliqués dans le transfert de K+ vers la plante. Ces canaux appartiennent à la famille TOK (Tandem-pore Outward-rectifying K+), spécifique de champignons et ont été caractérisés par plusieurs approches expérimentales. Des analyses in silico ont déterminé que ces trois canaux appartiennent à deux sous-familles et ont été nommés HcTOK1, HcTOK2.1 et HcTOK2.2. Leurs propriétés fonctionnelles ont été caractérisées par expression hétérologue pour une analyse en voltage-clamp à deux électrodes et complémentation de levures. La localisation a été étudiée par hybridation in situ en mycorhizes et par fusions gène-eGFP exprimés chez la levure et chez H. cylindrosporum. Le rôle physiologique des canaux HcTOK a été testé en culture pure et en symbiose avec P. pinaster grâces à des lignées transgéniques surexprimant ces gènes. En plus, les effets de la mycorhization par H. cylindrosporum et la nutrition potassique ont été testés chez P. pinaster cultivé en conditions de stress salin. Dans un premier temps, la tolérance du champignon au stress salin a été vérifiée en culture pure, ainsi que l’élément toxique de ce stress. Ensuite, le champignon a été cultivé en deux conditions de nutrition potassique et quatre de salinité pour connaître son homéostasie du K+ et analyser l’expression de ses systèmes de transport. Finalement, des plantules de P. pinaster ont été cultivées inoculées ou non en deux conditions de K+ et quatre de stress salin. En résumé, l’analyse de trois canaux HcTOK ont permis de démontrer les spécificités pour les sous-familles TOK1 et TOK2 et ont suggéré que HcTOK2.2 est probablement un élément clé pour le transfert du K+ via la plante en mycorhize. H. cylindrosporum semble jouer un rôle dans la tolérance à la salinité du pin maritime en diminuant le transfert du Na+ vers la plante et améliorant la nutrition potassique
The ectomycorrhizal symbiosis, widespread in temperate and boreal ecosystems, is based in nutritional exchanges between the host plant and soil-borne fungi. This mutualism improves plant mineral and water nutrition of woody plants through mechanisms that are still largely unknown. This manuscript presents the whole set of membrane transport systems of the ectomycorrhizal fungus Hebeloma cylindrosporum identified from the sequenced genome, with an emphasis on the genes that are up-regulated in symbiosis with its natural host, the maritime pine (Pinus pinaster). These data will help to focalize future research on symbiosis-induced genes. The fungus H. cylindrosporum enhances the potassium (K+) nutrition of P. pinaster under starvation. This study has focused on three ion channels that could transfer the K+ to the plant. These channels belong to the fungal-specific TOK (Tandem-pore Outward-rectifying K+) family and have been characterized using several approaches. In silico analyses have positioned them in two subfamilies, giving them the names HcTOK1, HcTOK2.1 and HcTOK2.2. Their functional activity has been characterized by heterologous expression for two-electrode voltage-clamp measurements and yeast complementation. Localization has been studied by in situ hybridization in mycorrhiza and by expression of gene-eGFP constructs in yeast and H. cylindrosporum. The physiological role of these channels has been tested in pure culture and symbiosis with transgenic fungal lines overexpressing the HcTOK channels. Furthermore, the effects of H. cylindrosporum and K+ nutrition have been tested in P. pinaster seedlings subjected to salt stress. First, the tolerance to salinity of the fungus was analysed in pure culture with different compounds to identify the most toxic component. Second, the fungus was cultured in different NaCl and K+ conditions to know whether it kept the homeostasis and to check the expression of K+ transport systems. Finally, P. pinaster seedlings were cultured inoculated or not in two different K+ nutrition and four salinity conditions. Altogether, analysis of the three HcTOK channels revealed specificities of the TOK1- and TOK2-type and suggested that HcTOK2.2 might be a main player for the K+ transfer from the fungus towards the plant. H. cylindrosporum seems to play a role in the tolerance to salt stress of the maritime pine by reducing the Na+ transfer to the plant and improving K+ nutrition

Ce projet de thèse porte sur la recherche de nouveaux électrolytes et additifs dans le but d’améliorer la cyclabilité d’une électrode négative composite de formule Si0.32Ni0.14Sn0.17Al0.04C0.35 et d’obtenir une interface électrode|électrolyte stable. En effet, comme la plupart des matériaux à base de silicium, ce composite de grande capacité (plus de 600 mA.h.g-1) souffre actuellement d’une faible durée de vie provenant essentiellement des expansions volumiques qu’il subit lors de sa lithiation et de sa SEI défaillante. Deux types d'électrolytes ont été évalués : (i) un mélange de carbonates d’alkyles EC/PC/3DMC auquel a été ajouté un sel de lithium (LiPF6, LiTFSI, LiFSI ou LiDFOB) ainsi que des additifs aidant à la formation de la SEI tels que le carbonate de vinylène (VC) ou le carbonate de fluoroéthylène (FEC), (ii) des liquides ioniques (LI) contenant un cation ammonium quaternaire (N1114+), imidazolium (EMI+) ou pyrrolidinium (PYR+), associé à un anion à charge délocalisée comme le bis(trifluorométhanesulfonyl)amidure (TFSI-) ou le bis(fluorosulfonyl)amidure (FSI-). L’analyse du diagramme d’ionicité de Walden a permis de mettre en évidence la bonne dissociation de LiFSI et LiPF6 dans EC/PC/3DMC assurant ainsi des conductivités ioniques supérieures à 12 mS.cm-1. Bien que possédant des propriétés de transport a priori moins intéressantes dans ce mélange ternaire que les autres sels, LiDFOB forme en réduction une SEI permettant au composite de fournir les meilleures performances en cyclage sans additif avec 560 mA.h.g-1 pour un rendement coulombique de 98,4%. L’ajout d’additif est cependant nécessaire pour atteindre les objectifs fixés par le projet en termes de rendement coulombique (>99,5%). Dans ce cas, l’ajout de 2%VC+10%FEC au mélange ternaire est le plus intéressant avec LiPF6. Le matériau fourni ainsi des capacités de 550 mA.h.g-1 durant une centaine de cycles à un régime de C/5 avec un rendement coulombique de 99,8%. En milieu LI, les performances optimales sont atteintes avec le [EMI][FSI] et 1 mol.L-1 de LiFSI. Le composite atteint alors une capacité de 635 mA.h.g-1 durant 100 cycles à un régime de C/5 avec un rendement coulombique très proche de 100%, tout en s’affranchissant de l’ajout d’additifs. Malgré une viscosité bien plus élevée que celles des mélanges de carbonates d’alkyles, cette formulation permet de générer une SEI plus stable dont la nature, principalement minérale, est issue majoritairement des produits de réduction de FSI-
This study focuses on new electrolytes and additives in order to improve the cyclability of a Si0.32Ni0.14Sn0.17Al0.04C0.35 negative composite electrode (Si-Sn) and to obtain a stable electrolyte|electrolyte interface. Indeed, like most silicon-based materials, this high-capacity Si-Sn composite (over 600 mA.hg-1) currently suffers from a short cycle life due to volume expansion during charge-discharge processes leading to the degradation of the SEI. To improve the quality of the interface, two kinds of electrolytes were evaluated: (i) mixtures of alkyl carbonates EC/PC/3DMC in which a lithium salt (LiPF6, LiTFSI, LiFSI or LiDFOB) and additives like SEI builder (vinylene carbonate (VC) or fluoroethylene carbonate (FEC)) were added, (ii) ionic liquids (IL) based on quaternary ammonium (N1114+), imidazolium (EMI+) or pyrrolidinium (PYR+) cation, associated with delocalized charge anions such as bis(trifluoromethanesulfonyl)imide (TFSI-) or bis(fluorosulfonyl)imide (FSI-). The Walden diagram confirms the efficient dissociation of LiFSI and LiPF6 in EC/PC/3DM ensuring ionic conductivities as high as 12 mS.cm-1. Although possessing limited transport properties in such a ternary mixture compared to other salts, LiDFOB forms, without additional additives, an high quality SEI allowing the composite to provide the best performances in half cells (560 mA.hg-1 and 98.4% coulombic efficiency). The use of additive is however necessary to reach the objectives fixed by the ANR research project in terms of coulombic efficiency (>99.5%). In this case, the addition of 2%VC+10%FEC to the ternary mixture is the most interesting composition with LiPF6 as lithium salt. So, the Si-Sn nanocomposite material reaches 550 mA.h.g-1 during 100 cycles at C/5 with 99.8% efficiency. In IL, the best performances are achieved in [EMI][FSI]/LiFSI (1 mol.L-1). The performances of the Si-Sn composite reaches 635 mA.h.g-1 for 100 cycles at C/5 with coulombic efficiency close to 100%, without additives. This electrolyte formulation generates a stable SEI which the mainly mineral composition, is predominantly derived from the reduction products of FSI-

During the sequestration of CO2 into down-hole rock formations, salt precipitation may occur due to the drying of the formation brine if the injected CO2 is dry. This can negatively affect the performance of injection wells and can even lead to well clogging, which is a serious risk for such operations. Further, the salt deposition can alter the flow of the CO2 in the formation altering the storage capacity. Therefore, it is very important to explore the effect on CCS (Carbon Capture and Storage) process of drying out and salt precipitation during CO2 injection. This study is focused on CCS in fractured aquifers, which has received less attention than their un-fractured counterparts and particularly, the flow impairment associated with salt precipitation during the injection of dry CO2. When CO2 is injected into a conductive fracture network, the brine will rapidly be displaced from the fractures near the point of injection and the subsequent mass transfer between the matrix and the fracture; orthogonal to the flow direction in the fracture, is the major target of the project. The dry-out that occurs due to the evaporation of water from the brine filled region of the matrix into the under-saturated CO2 filling the fracture can cause deposition of salt in the matrix or the fracture, locally reducing permeability. This thesis reports on an investigation of the evaporative drying kinetics and salt precipitation using a combination of gravimetric and X-ray µ-CT techniques to measure the water and brine saturation, salt precipitation and distribution of salt deposition in two rocks; a sandstone, Bentheimer and a carbonate, Ketton. Based on the experimental results for de-ionised water, two main regimes occur during the dry-out process: a capillarity driven regime which seems to be dominant for most of the dry-out process in the experiments, during which evaporation happens only at the surface of the fracture, followed by a diffusion limited regime after the liquid bridge to the surface breaks and pores near the surface become dry for the first time. In pure water, this results in an almost constant evaporation flux in the first regime followed by a mass loss that is linear when plotted against the square root of time. The experiments with brine were initially similar with an evaporative flux almost constant with time. However, a short time into the process the evaporative flux started to decrease approximately linearly with the square root of time, following the deposition of salt at the surface of the fracture. At the end of gravimetric dry-out tests, µ-CT images were obtained showing that salt was mainly precipitated at the surface of the sample; however, relatively small amount of salt was observed precipitated in the interior of the sample. The pore structure of the precipitated salt at the end of the dry-out tests maintained connectivity between the surface of the deposit and the rock matrix. Dynamic µ-CT imaging of Bentheimer during brine drying showed that during the early stage of evaporation, salt was continuously deposited at the surface of the matrix. During this stage in the evaporation of brine, advection dominates the transport of dissolved salt, indicated by a large Peclet number, and this resulted in an increased salt concentration very local to the site of evaporation. The ongoing formation of an efflorescence therefore, is evidence for the continuity of the liquid connections to the outside of the sample, despite the evaporation becoming linear against the square root of time. Unfortunately, the liquid bridges to the surface were too small to be seen directly in the µ-CT imaging. The volume of precipitated salt increased with time and this resulted in a change in the pore structure at the surface of the sample structure, consequently reducing the brine-drying rate. However, as the salt deposition and therefore the location of the evaporation continued to be at the exposed surface, vapour diffusion cannot account for the mass lost by evaporation becoming linear in the square root time as is usually stated. Some other mechanism must account for the observed behaviour and we speculate that the surface area for evaporation was reduced by the appearance of dry patched on the surface. At a very late stage of evaporation, it was observed that no further salt precipitated at the surface of the sample; and subsequently, salt precipitation progressed with time towards the interior of the sample core with small amount of salt. At this stage the liquid connection to the surface must finally have broken and a true diffusion controlled process occurred. In the limited sample size used in this study, this mechanism accounted for only a small fraction of the total salt deposited. From permeability measurements before and after the complete drying of the samples, it was demonstrated that the permeability of Bentheimer was reduced by 81 % from 2.2 D to 0.41 D by the salt deposition. However, Lattice Boltzmann simulations of single phase permeability in the segmented µ-CT images, showed a reduction by 54% from 2.27 D to 1.28 D at 6 µm scanned voxel resolution and 54% from 2.7D to 1.48D at 15um scanned voxel resolution. From these results, it can be concluded that salt precipitation during the injection of CO2 into a fractured porous medial result in a significant reduction in formation permeability, but connectivity between the matrix and the fracture is maintained.

Includes abstract.
Includes bibliographical references.
South African cities have unique spatial design challenges which can be attributed to our historical and politically charged urban planning practices. Our cities are characterised by modernist town planning principles which have fragmented communities through spatial barriers such as highways, train lines and fences while current development perpetuates urban sprawl. Due to these circumstances many contemporary urban design policies promote densification strategies through transit orientated approaches.In my thesis project, I propose to redesign Salt River Train Station into a multi modal transport interchange. I argue that this multimodal interchange can have an urban developmental and regenerative effect that can address some of the challenges faced in our urban landscape. This design report will attempt to document the processes and explorative methods that I have incorporated during this design process.

Breeding and selection for salt tolerance has been limited because of the large heterogeneity of natural saline soils and the lack of efficient criteria for measuring salt tolerance. Regulation of salt balances in leaves is an important aspect of salt tolerance. This work analyses the relationship between leaf ion concentrations and salt tolerance with the aim of using these traits as indicators of salt tolerance. This is done both in solution culture (hydroponics) and field trials (sprinkler irrigation with saline water). Varieties were found to differ in the amounts of ions accumulated in their leaves. However, these differences did not relate directly with their level of salt tolerance. The lack of correlation was partly due to difficulties in estimating salt tolerance in the field. Also, the Triple Line Sprinkler system (TLS) used in the field experiments posed several problems, the most important ones being related to direct ion absorption by the leaves. The high concentrations of CaC12 (in addition to NaCl) used in the irrigation water added a further complication. In hydroponic experiments, a minimum of 2 mol in-' Ce' was enough to prevent an indiscriminate entry of Na' and to ameliorate the growth inhibition of plants growing at 200 mol in-' NaCl. Higher Caý' concentrations (50 mol in-' CaCl2) reduced even more the concentrations of Na' in leaves without significantly affecting growth. At these high levels of CaCl2 any toxic effect was probably caused by high Clconcentrations.

The ion-polymer and ion-ion interactions in polymer electrolytes based on high molecular weight, amorphous methoxy-linked PEO (PMEO) and lithium salts have been investigated by conductivity measurement, magic-angle spinning NMR (mas NMR) and pulsed field gradient NMR (pfgNMR) techniques. In the very dilute salt concentration region, ion pairing effects are dominant in these polymer electrolytes. Ion association is found to increase with temperature and salt concentration. Ion transport for these electrolytes is controlled both by segmental motion of the polymer and activation process, in which the former is important for the dilute concentration samples while the latter is important for the concentrated samples. The mass transport process in polymer electrolytes based on a zinc salt has been investigated by steady state dc polarisation and Hittorf techniques. Zinc ion constituents in these electrolytes are mobile with a limiting current fraction of about 0.2 at 80°C, and the transference number measured by the Hittorf method is less than 0.1. The main species in these electrolytes are proposed to be neutral mobile triples. The electrode-electrolyte interfaces in polymer electrolytes based on calcium and magnesium salts have been studied. Dc polarisation experiments for these polymer electrolytes were carried out using two electrode cells with the metal anode and mercury film amalgam cathode. The results of dc polarisation experiments suggest that calcium species are mobile in high molecular weight electrolytes, while magnesium species are immobile. The influence of the molecular weight of the polymer on the dynamics of cation constituents has been studied based on the experimental results of dc polarisation and pfg NMR, and on the theoretical analyses of the reptation theory and the Rouse model. It is found that the transport of the gravity centre of the polymer will influence the ion transport in polymer electrolytes based on PEO in a manner described by the Rouse model when the molecular weight of PEO is less than 3200.

Regulation of transmembrane ion transport is a vital aspect in the maintenance of a healthy organism. To understand how this highly selective process occurs, how it can become impaired and how impairment may be treated, model compounds are useful tools. Several systems are presently being explored but one of the most widely applicable combines a rigid macrocycle, capable of size-based ion recognition, with membrane spanning substituents that allow the target ions to transverse a phospholipid bilayer. The calixarene class of macrocycles is ideally suited to this task. Previous work had shown that oxacalix[3]arenes could act as models for the filters in natural transmembrane ion channels. Nitrogen-containing analogues of these calixarenes, azacalix[3]arenes, were investigated with a view to constructing a chloride transporting system. Synthetic difficulties encountered when introducing lower rim substitutents precluded the use of azacalix[3]arenes and attention turned to 4-t-butylcalix[n]arenes. 4-t-Butylcalix[4]- and [6]arenes were derivatised with a commercial, membrane disrupting surfactant, Triton X-IOO®, forming compounds designed to form lipid bilayer-spanning, channel-like structures. The ion transporting ability of these, and other bilayer-spanning O-substituted calixarene derivatives, was determined by planar bilayer electrophysiological methods. Results showed that this modular approach to artificial ion channel construction was successful; calixarene derivatives formed transmembrane channels that allowed sodium ions to pass through but not the larger potassium ions.

Organic electronics and printed electronics have been attracting more and more research interest in the past decades. Polymers constitute an important class of materials within the field organic electronics due to their unique physical and chemical properties. One great benefit of the polymers is their solution processability, which provides us the possibility to utilize conventional printing techniques to fabricate devices on flexible substrates. This thesis focuses on utilizing and controlling the ion transport in polyelectrolytes in electronic devices for different applications. A polyelectrolyte is a polymer in which the polymeric backbone includes ionic sites compensated by counter ions. Firstly, we have used a specific property of the polyelectrolyte: its electric polarization is strongly dependent on the humidity level. The ions are screened by water molecules; this improves the mobility and dissociation of ions. A polyelectrolyte-based capacitor is thus ideal to sense humidity. Such a capacitor is integrated into an LC resonant circuit possessing a specific resonant frequency. The wirelessly detected resonant frequencies of the sensing circuit indicate the corresponding humidity levels. With the appropriate choice of materials, the complete sensing circuit (resistor, capacitor, capacitor-like sensor head) can be screen-printed on an antenna manufactured using a roll-to-roll dry phase patterning technique. Secondly, we have modified the polarization characteristics of ions in a polyelectrolyte layer by trapping the ions in molecular macrocycles dispersed in a polymer overlayer. The resulting remanent polarization is read out as a hysteresis loop in the capacitance-voltage characteristic of a capacitor. The strategy is further implemented in an electrolyte-gated organic transistor to control its threshold voltage by applying defined programming voltages. Although the lifetime of the “remanent” polarization is rather short, the concept might be further improved to fit those of memory applications. Finally, we take use of the ionic selectivity of a polyelectrolyte to stabilize the operation of a water-gated organic field-effect transistor. The polyanionic membrane is added onto the semiconductor channel to prevent small anions of the aqueous electrolyte to penetrate into the p-channel semiconductor. Moreover, the polyelectrolyte layer protects the semiconductor and thus strongly stabilizes the shelf lifetime of those transistors. This improved version of the water-gated organic transistor is a candidate for developing transistor-based sensors working in, for instance, biological media.

Mobilities of positive and negative atomic ions in helium have been determined using both two- and three-temperature theories. These calculations require that an interaction potential be supplied which corresponds to the molecular ion HeX⁺ or HeX-, where X⁺ or X- is the ion of interest. The interaction potential must have the correct separation behaviour to spectroscopic states of the particles involved including ¹S He. Molecular orbital and valence bond methods have been employed to calculate interaction potentials for use in mobility calculations. A drift-tube mass spectrometer has been used for the experimental determination of ion mobilities in helium. These, and other experimental mobility data, have been compared to the calculated mobilities. The development of computer programs for mobility calculations, experimental control, data acquisition, and data analysis are described. An important feature of the ion mobility program used in this work is its ability to accept a tabulated interaction potential. This enables the result of an ab-initio calculation to be used directly in a mobility calculation. The differences between experimental measurements of the mobilities of ions of the same mass are explained in terms of differences in the ion neutral interaction potential. The mobilities of F-, O⁺, Q⁺*, B⁺, N⁺, F⁺ and Li⁺ ions in helium are calculated using the mobility program with ab-initio interaction potentials. Where two or more molecular states can arise from the spectroscopic states of helium and the ion involved, the ion mobility is determined from an average of the results of mobility calculations for each of the possible molecular states. An accurate measurement of the mobility of N⁺ in helium from 35 Td to 140 Td has been made which agrees with an earlier mobility measurement. The rate constant for the reaction of positive helium ions, obtained from this work and subsequently measured independently, disagrees with previous work. Valence bond calculations are reported for a series of diatomic molecules and ions; the principal valence structures found correspond to those expected on the basis of traditional bonding theories. The further application of the methods used and developed in this work is discussed.

This dissertation focuses on the synthesis and electrochemical testing of new electrolyte salts for rechargeable multivalent ion batteries. In chapters 2 and 3 the synthesis of Mg and Ca hexafluoropnictogenate salts as well as the electrochemical behaviour of Mg(PF6)2 is presented. Pure samples of Mg(EF6)2 (E = P, As, and Sb) can be synthesized using Mg metal and NOPF6/NOSbF6 in CH3CN or via a ammonium salt deprotonation route using Me3NHAsF6 and Bu2Mg. The NOPF6 method was extended to the Ca variant, but isolation of a pure Ca(PF6)2 material required the presence of a crown ether. Electrochemical and microscopy measurements of THF-CH3CN solutions of Mg(PF6)2 show that the electrolyte good electrochemical stability and can facilitate the plating/stripping of Mg. Further, this electrolyte system can be cycled in a full cell using the Chevrel phase Mo6S8 cathode. The electrochemical stability of the AsF6− and SbF6− salts is lower than that of the PF6− salt and electrolyte decomposition is observed when cycling on Mg electrodes. In chapter 4 the development of a series of Mg aluminates [Mg(AlOR4)2] using a general synthetic platform based on Mg(AlH4)2 and various alcohols is presented. Preliminary electrochemical studies performed on these aluminate salts in dimethoxyethane identify the phenoxy and perfluoro-tert-butoxy derivatives as promising electrolyte systems. Electrochemical cycling of these electrolytes using gold and Mg electrodes show that systems containing chloride, brought through to the product from the starting material in the form of NaCl, exhibit lower plating/stripping overpotentials and higher Coulombic efficiencies than systems from which chloride had been removed. Further, these two electrolytes can be used in Mg full cells containing the Chevrel phase cathode. Solid-state 23Na NMR analysis as well as DFT calculations show that chloride-containing electrolytes facilitate the co-insertion of Na into the cathode material. In chapter 5 the hydroboration of pyridines and CO2 in the presence of pinacolborane is presented. An optimized system employing NH4BPh4 and HBpin is developed and a mechanism of pyridine hydroboration is proposed based on multinuclear NMR spectroscopy. The catalytic reaction was found to be catalyzed by a boronium salt, which was structurally characterized in the solid-state by single crystal X-ray diffraction. This new catalytic method is shown to be tolerant to a number of functional groups in the 3-position on pyridine as well as quinoline, and CO2, producing the hydroboration products in good yields.

Pendant l’électro-élaboration de l’aluminium par le procédé Hall-Héroult en milieu de cryolite fondue, il y a production parasite de sodium qui imprègne le carbone du bloc cathodique, suivi de près par l’électrolyte. Ceci provoque le gonflement du carbone et conduit à la limitation de la durée de vie de la cellule d’électrolyse. Dans l’objectif d’élucider les mécanismes d’interaction entre le sodium et le carbone, nous avons mené une étude de cinétique électrochimique en milieu NaF pur fondu à 1025°C. L’utilisation de diverses techniques électrochimiques (voltampérométrie, chronopotentiométrie et coulométrie) a mis en évidence l’existence d’une interaction complexe entre le sodium et le carbone. En effet, le métal alcalin est distribué entre deux types de sites correspondant à deux activités différentes. La forme la moins fortement liée au carbone correspond au sodium piégé dans la micro-porosité, alors que la forme plus stable est attribuée au sodium inséré entre les plans de graphène. Nous avons aussi montré l’existence d’un transfert lent et irréversible des espèces piégées vers les sites normaux d’insertion. De plus, en raison de l’évaporation du sodium à partir de l’interface, le produit Na-C subit une décomposition. Le transport du métal alcalin dans le réseau hôte est limité par une transition de phase du premier ordre. En tenant compte de toutes ces observations expérimentales, nous avons proposé un mécanisme réactionnel, construit le modèle mathématique associé et résolu le système d’équations différentielles, ainsi obtenu, en utilisant la méthode des différences finies. Les résultats obtenus montrent un bon accord entre les courbes théoriques et les résultats expérimentaux et permettent l’estimation des différents paramètres cinétiques des processus d’interaction Na-C. Enfin, nous avons montré que la pénétration du sodium provoque un changement de la tension interfaciale NaF-C et induit la progression du bain fondu par capillarité à partir d’une fraction molaire minimale en sodium (XNa=1,4. 10-2)
One of the most important factors causing the failure of carbon cathode, during aluminum electrolysis by Hall-Héroult process, is the uptake of sodium which leads to a macroscopic swelling of cathode. To understand the fundamental mechanism of sodium-carbon interaction, we carried our electrochemical kinetic study in a pure molten NaF electrolyte at 1025°C. We proved the occurrence of a complex interaction between sodium and carbon. Indeed, sodium is showed to be distributed between two kinds of sites in the host material : normal sites in the Van der Wals gap between the carbon’s plans and traps which are located at microporosity and dislocations. We also showed the occurrence of a slow and irreversible transfer of sodium from traps to normal intercalation sites. Moreover, sodium transport in carbon matrix is found to be limited by a first order phase transition. Taking into account all these experimental observations, we suggested a complete mechanism scheme and developed a mathematical model which allowed the recovery, with a good accuracy of the experimental results

Ab initio calculations of potential energy surfaces have been applied to a range of chemical problems. Specifically these methods have been applied to the Diels-Alder reaction between butadiene and acetylene. The structure of the reactants, the Cs transition state, and the products have been calculated. The transition state geometry and energy is analysed in terms of orbital interactions and distortion energy relative to the separated reactants. The increase in energy of the filled π-orbital of acetylene not involved in bonding changes is the major contributor to the activation energy for the Diels-Alder reaction of butadiene with acetylene being greater than that found between butadiene and ethylene. Comparisons with a series of other related Diels-Alder reactions are discussed. The calculation of interaction potentials of a series of open shell ions with helium has been combined with moment method calculations to determine the ion transport properties of systems that involve anisotropy. First the theory of the moment methods used to calculate the transport properties of ions in dilute gases is reviewed. The theory for spherically symmetric ions in a spherically symmetric gas is briefly discussed, followed by a review of the recent specialisation of the theory for diatomic ions in diatomic gases to atomic ions in a diatomic gas. The theory of spherically symmetric systems is then applied to open shell ions that have orbital angular momenta greater than zero. Any theoretical treatment of the ion transport properties of such ions must recognise that more than one collision channel is available to the collision partners. Two classical models are developed that involve non-adiabatic transitions between these collision channels during a collision and between collisions. The models are used to study the mobilities of the following ions: C⁺ (² P), C+* (⁴P), N⁺(³ P), O⁺ (48), O⁺* (± P), Si⁺(²P), Si⁺* (⁴P). A summary and discussion is given. The theory of atomic ions in diatomic gases is then applied to the Li⁺ — N₂ and the Li⁺ — CO systems. Ab initio calculations of the rigid rotor potential energy surfaces for these systems are followed by calculations of the transport cross sections and transport coefficients. Comparisons of the transport coefficients derived from existing potential energy surfaces show that the potential energy surfaces calculated in this work are significantly better, and as good as can be derived from comparison of the theoretical and experimental ion transport results.

A systematic study of structure-property relations has been carried out on a range of polymers, both with and without mesogenic moieties. These materials have been characterised using various thermal techniques, including DSC and DMTA. These polymers have been complexed with LiClO₄ and the effects of the salt on thermal characteristics have been investigated. In addition, AC impedance spectroscopy has been employed to determine the temperature dependence of the conductivity of these complexes. Results suggest that polymers with mesogenic side groups have the potential to exhibit a conduction mechanism which is independent of both the glass transition temperature of the complex as determined by DSC and the corresponding structural relaxation detected using DMTA. It is found that the glass transition temperature of these materials is determined primarily by the side groups, and not by the polymer backbone. A model is thereby proposed in which ionic motion is decoupled from Tg, but still dependent on the local viscosity of the ionic environment. Appreciable conductivity is therefore observed below the glass transition temperature of the complex, thus resulting in dimensionally stable polymeric complexes with possible applications as solid state electrolytes in batteries.

The performance of an inductively coupled plasma mass spectrometer, ICP-MS, depends on the instrument's ability to transport sample ions through the vacuum interface and focus the ions into a well-defined beam that will eventually reach the mass analyzer. In this study two main experiments were performed on the Perkin Elmer NexION 300S, a commercial ICP-MS. First, planar laser-induced fluorescence images were taken of the ion beam in a working instrument downstream from a unique quadrupole ion deflector. The images showed the ability of the instrument design to focus the ions in the ion beam. Second, laser-induced fluorescence was used to characterize ion flow through the vacuum interface. The interface is unique to the NexION ICP-MS in that there are three extraction cones. The effect of a three-cone interface on ideal skimming is discussed.

Ion channels are pore-forming proteins that regulate the flow of ions across biological cell membranes. Ion channels are fundamental in generating and regulating the electrical activity of cells in the nervous system and the contraction of muscolar cells. Solid-state nanopores are nanometer-scale pores located in electrically insulating membranes. They can be adopted as detectors of specific molecules in electrolytic solutions. Permeation of ions from one electrolytic solution to another, through a protein channel or a synthetic pore is a process of considerable importance and realistic analysis of the main dependencies of ion current on the geometrical and compositional characteristics of these structures are highly required. The project described by this thesis is an effort to improve the understanding of ion channels by devising methods for computer simulation that can predict channel conductance from channel structure. This project describes theory, algorithms and implementation techniques used to develop a novel 3-D numerical simulator of ion channels and synthetic nanopores based on the Brownian Dynamics technique. This numerical simulator could represent a valid tool for the study of protein ion channel and synthetic nanopores, allowing to investigate at the atomic-level the complex electrostatic interactions that determine channel conductance and ion selectivity. Moreover it will provide insights on how parameters like temperature, applied voltage, and pore shape could influence ion translocation dynamics. Furthermore it will help making predictions of conductance of given channel structures and it will add information like electrostatic potential or ionic concentrations throughout the simulation domain helping the understanding of ion flow through membrane pores.

Thesis (Ph. D.)--Joint Program in Physical Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences; and the Woods Hole Oceanographic Institution), February 2000.
"February 2000."
Includes bibliographical references (leaves 163-171).
The variability of salt transport determines the variation of the length of the salinity intrusion and the large-scale density gradient in an estuary. This thesis contains three studies that address salt transport and the salt balance. The variation of salt transport with the depth, the along-channel salinity gradient, and the amplitude of the tidal velocity is investigated with analytic and numerical models. The results indicate that salt transport increases dramatically during stratified periods when vertical mixing is weak. Analysis of salt transport from observations in the Hudson Estuary show that stratified periods with elevated estuarine salt transport occur in five-day intervals once a month during apogean neap tides. Oscillatory salt transport, which is hypothesized to be primarily caused by lateral exchange and mixing of salt, appears to play a more minor role in the salt balance of the estuary. The salt balance of the estuary adjusts very little to the spring-neap modulation of salt transport but adjusts rapidly to pulses of freshwater flow. A simple model is used to investigate the process and time scales of adjustment of the salt balance by connecting variations of salt transport to the variations of freshwater flow and vertical mixing. The results show the length of the salinity intrusion adjust via advection to rapid and large increases in freshwater flow. The salinity intrusion adjusts more rapidly to the spring-neap cycle of tidal mixing the higher the freshwater flow.
by Melissa Marie Bowen.
Ph.D.

I present photonics applications of PbS quantum-dot-doped (QD-doped) glasses. The dissertation consists of two major parts: bulk material applications (Cr:forsterite laser modelocking, bleaching dynamics, optical gain, and photoluminescence) and the fabrication of QD-doped ion-exchanged waveguides.When this work began, these PbS QD-doped glasses were the state-of-the-art in QD glasses due to their narrow size distribution. Modelocking of a Cr:forsterite laser using this glass as a saturable absorber had been demonstrated, with little understanding of the dynamics. This work began by studying the dynamics of the saturable absorber to explain the ps-pulse width.In the bulk measurements, I functioned as secondary researcher. In the laser modelocking and bleaching measurements, my contribution was laser cavity alignment, sample preparation, collecting autocorrelation traces, and aiding in the setup and data collection for the bleaching measurements. On this work, I coauthored one refereed journal article in Applied Physics Letters [1] and one refereed conference paper [2], for which I am third and second author, respectively.For the gain measurements, I aided in the setup and data collection, whereas I set-up and took most of the luminescence data. The gain measurements resulted in one second-author refereed journal article in Applied Physics Letters [3] and I presented the luminescence results at CLEO2000 [4].I took the lead role in the waveguide fabrication and characterization and authored refereed journal articles in Applied Physics Letters [5], Journal of Applied Physics [6], and Journal of the Optical Society of America B [7]. I also presented an invited talk at Photonics West [8] and presented at CLEO2004 [9]. Additionally, I have been a coauthor of presentations at the Nanotechnology Symposium (2006), American Ceramic Society [10], and Photonics Europe (2006) [11]. A book chapter in The Photonics Handbook, 2nd edition [12] also discusses this work.The next step is to focus on reducing the waveguide losses. This requires new, circular wafers with better surface quality and glass homogeneity. I suggest using silver-film ion exchange followed by a field-assisted burial to eliminate the surface interaction.

Thesis (Ph. D.)--University of Maryland, College Park, 2003.
Thesis research directed by: Chemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.

Many organic electronic and bioelectronics devices rely on mixed (electronic and ionic) transport within a single organic layer. Although electronic transport in these materials is relatively well understood, a fundamental understanding of ion transport is missing. I developed a simple analytical model that describes ion transport in a planar junction between an electrolyte and a conducting polymer film. The model leads to predictions of the temporal evolution of drift length of ions and current. These predictions are validated by numerical simulations and by using realistic parameters, I show that the analytical model can be used to obtain the ion mobility in the film. Furthermore, I developed an experimental method which allows the application of the analytical model and leads to a straightforward estimation of the ion drift mobilities in conducting polymers. PEDOT:PSS was found to support efficient transport of common ions, consistent with extensive swelling of the film in water. Crosslinking the film decreased its swelling and the ion mobility. Understanding the high correlation of hydration and ionic conductivity enables us to engineer materials with high and defined ion mobilities. As an example tuning of ion mobility by adjusting the relative ratio of the hydroscopic phase to PEDOT:TOS is presented. Finally I performed electrochemical impedance spectroscopy during a moving front experiment, in order to give a physical interpretation of the impedance spectra at a conducting polymer/electrolyte junction.