Freiburg im Breisgau, Univ., Diss., 2004.

Stuttgart, Univ., Diss., 2006.

Nanoelectronics is an essential technology for down-scaling beyond the limit of silicon-based electronics. Single-Wall Carbon Nanotubes (SWNT) are semiconducting components that exhibit a large variety of properties that make them usable for sensing, telecommunication, or computational tasks. Due to their high surface to volume ratio, carbon nanotubes are strongly affected by molecular adsorptions, and almost all properties depend on surface adsorption. SWNT with smaller diameters (0.7-0.9nm) show a stronger sensitivity to surface effects. An optimized synthesis route was developed to produce these nanotubes directly. They were produced with a clean surface, high quality, and large lengths of 2 μ m. The results complement previous studies on larger diameters (0.9-1.4nm). They allow performing statistically significant assumptions for a perfect nanotube, which is selected from a subset of nanotubes with good emission intensity, and high mechanical durability. The adsorption of molecules on the surface of carbon nanotubes influences the motion and binding strength of chargeseparated states in this system. To gain insight into the adsorption processes on the surface with a minimum of concurrent overlapping effects, a microscopic setup, and a measurement technique were developed. The system was estimated to exhibit excellent properties like long exciton diffusion lengths (>350nm), and big exciton sizes (8.5(5)nm), which was substantiated by a simulation. We studied the adsorption processes at the surface of Single-Wall Carbon Nanotubes for molecules in the gas phase, solvent molecules, and surfactant molecules. The experiments were all carried out on suspended individualized carbon nanotubes on a silicon wafer substrate. The experiments in the gas-phase showed that the excitonic emission energy and intensity experiences a rapid blue shift during observation. This shift was associated with the spontaneous desorption of large clusters of gaseous molecules caused by laser heat up. The measurement of this desorption was essential for creating a reference to an initially clean surface and allows us to perform a comparison with previous measurements on this topic. Furthermore, the adsorption of hydrogen on the nanotube surface at high temperatures was investigated. It was found that a new emission mode arises slightly red-shifted to the excitonic emission in these systems. The new signal is almost equally strong as the main excitonic peak and was associated with the brightening of dark excitons at sp3-defects through a K-phonon assisted pathway. The finding is useful for the direct synthesis of spintronic devices as these systems are known to act as single-photon emitters. The suspended nanotubes were further studied to estimate the effect of solvent adsorption on the excitonic states during nanotube dispersion for each nanotube individually. A significant quantum yield loss is observable for hexane and acetonitrile, while the emission intensity was found to be the strongest in toluene. The reference to a clean surface allowed us to estimate the exact influence of the dielectric environment of adsorbing solvents on the excitonic emission energy. Solvent adsorption was found to lead to an energy shift that is almost twice as high as suggested in previous studies. The amount of this energy shift, however, was comparably similar for all solvents, which suggests that the influence of the distinct dielectric constant in the outer environment less significantly influences the energy shift than previously thought. An interesting phenomenon was found when using acetonitrile as a solvent, which leads to greatly enhanced emission properties. The emission is more than twice as high as in the same air-suspended nanotubes, which suggests a process that depends on the laser intensity. In this study, it was reasonably explained how an energy down-conversion is possible through the coupling of the excitonic states with solvent vibrations. The strength of this coupling, however, also suggests adsorptions to the inside of the tubular nanotube structure leading to a coupled vibration of linear acetonitrile molecules that are adsorbed to the inner surface. The findings are important for the field of nanofluidics and provide an excellent system for efficient energy down-conversion in the transmission window of biological tissue. Having separated the pure effect of solvent adsorption allowed us to study the undisturbed molecular adsorption of polymers in these systems. The addition of polyfluorene polymer leads to a slow but stepwise intensity increase. The intensity increase is overlapping with a concurrent process that leads to an intensity decrease. Unfortunately, observing the stepwise process has a low spacial resolution of only 100-250nm, which is in the range of the exciton diffusion length in these systems and hinders detailed analysis. The two competing and overlapping processes processes are considered to originate from slow π-stacking and fast side-chain binding. Insights into this process are essential for selecting suitably formed polymers. However, the findings also emphasize the importance of solvent selection during nanotube dispersion since solvent effects were proven to be far more critical on the quantum yield in these systems. These measurements can shed light on the ongoing debate on polymers adsorption during nanotube individualization and allow us to direct the discussion more towards the selection of suitable solvents. This work provides fundamental insights into the adsorption of various molecules on the surface of individually observed suspended Single-Wall Carbon Nanotubes. It allows observing the adsorption of individual molecules below the optical limit in the solid, liquid, and gas phases. Nanotubes are able to act as sensing material for detecting changes in their direct surrounding. These fundamental findings are also crucial for increasing the quantum yield of solvent-dispersed nanotubes. They can provide better light-harvesting systems for microscopy in biological tissue and set the base for a more efficient telecommunication infrastructure with nano-scale spintronics devices and lasing components. The newly discovered solvent alignment in the nanotube surrounding can potentially also be used for supercapacitors that are needed for caching the calculation results in computational devices that use polymer wrapped nanotubes as transistors. Although fundamental, these studies develop a strategy to enlighten this room that is barely only visible at the bottom of the nano-scale. / Nanoelektronik ist eine wichtige Technologie um das Größen-Limit gegenwärtiger Silizium-basierter Technologie zu überwinden. Einwandige Kohlenstoffnanoröhren sind halbleitende Moleküle, die eine Reihe von Eigenschaften dafür zur Verfügung stellen. Sie sind einsetzbar als Sensoren, in der Fernmeldetechnik und für elektronische Rechenoperationen. Aufgrund ihres hohen Verhältnisses von Oberfläche zu Volumen werden nahezu alle Eigenschaften von Kohlenstoffnanoröhren stark von Adsorption beeinflusst. Einwandige Kohlenstoffnanoröhren mit kleineren Durchmessern (0.7-0.9nm) zeigen einen stärkeren Einfluss auf Phänomene, die an der Oberfläche auftreten. Um speziell diese Nanoröhren genauer zu untersuchen wurde eine Synthese Strategie entwickelt, die Nanoröhren mit hoher Qualität und Länge herstellen kann und dabei eine saubere Oberfläche gewährleisten ohne ihre Emissions-Stärke durch Bündelung zu verlieren. Die erhaltenen Ergebnisse unterstützen Studien aus der Literatur, die zumeist an Röhren mit größeren Durchmessern durchgeführt wurden. Die Größe des Datensatzes erlaubt es, Nanoröhren mit perfekten Emissions-Eigenschaften und großer mechanischer Stabilität auszuwählen. Adsorptionen beeinflussen die Bewegung und Bindungs-Stärke der Excitonen, da sie ein Coulomb Potential an der Außenseite der Röhre ausbilden. Um die Adsorptionsprozess an der Oberfläche mit minimalen konkurrierenden Effekten zu untersuchen, wurde ein spezielles mikroskopisches Setup gewählt und eine Messmethode entwickelt um dieses System zu untersuchen. Das System wurde mit Hilfe von Bildern und Spektren charakterisiert. Über eine Simulation wurde außerdem gezeigt dass die untersuchten Nanoröhren große Diffusionslängen (>350nm) und Exciton Größen (<8.5nm) besitzen müssen. Der Adsorptions Prozess an Kohlenstoffnanoröhren wurde sowohl mit Molekülen in der Gas-Phase untersucht, also auch in Lösungsmitteln und mit Feststoffen. Alle Experimente wurde dabei an frei hängenden Röhren durchgeführt, die auf einem Silizium Wafer Substrat aufgebracht wurden. Die Experimente in der Gas Phase zeigten, dass die excitonische Emissions-Energie eine instantane und schnelle Blauverschiebung erfährt wenn die Nanoröhren mit einem Laser angeregt werden. Diese Verschiebung wurde auf die Desorption von Oberflächenverunreinigungen zurückgeführt, die an Luft inhärent die Messung beeinflussen. Durch die Annahme, nach der Untersuchung eine reine Oberfläche zu erhalten, konnte die Referenz der Vakkum-Emission erstellt werden, was es ermöglicht, den Einfluss der dielektrischen Umgebung genauer zu bestimmen. In einem weitern Experiment wurde die Adsorption von Wasserstoff getestet. In diesen Systemen bildet sich durch die Ausbildung von sp 3 -Defekten eine neue Emissionsbande aus. Solche Emissionen werden derzeit für die Anwendung als Einzelphotonenemitter diskutiert. Die hier vorgestellte Methode erlaubt die direkte Synthese solcher Systeme im CVD Ofen. Die frei hängenden Nanoröhren wurden weiter analysiert um den Effekt des Lösungsmittels auf die Emission detailiert zu untersuchen. Es wurde gezeigt, dass in Hexan und Acetonitril ein signifikant hoher Quantenausbeute-Verlust zu beobachten ist. Toluol hingegen zeigte sich hier am Besten. Die Energie-Verschiebungen waren insignifikant unterschiedlich zwischen den Lösungsmitteln. Ein Spezialfall war bei Acetonitril zu beobachten, in dem sich über den Zeitraum von 24h eine starke Emission herausbildet, die auf eine Kopplung mit Lösungsmittel-Schwingungen zurückgeführt wird. Die Stärke dieser Emission erlaubt die Vermutung, dass es sich um eine gekoppelte Schwingung von linear orientiertem Acetonitril in der Nanoröhre handelt. Eine solch starke Emission könnte zu Anwendungen in Zell-Gewebe führen, da weder Anregung noch Emission sich im Fenster der Blut- und Wasserabsorption befindet. Durch die eindeutige Identifizierung von Lösungsmitteleffekten auf die Dispergierung von Kohlenstoffnanoröhren war es möglich, den Prozess der Anlagerung von Polyfluorene Polymeren direkt zu beobachten. Das Hinzufügen von Polymer zur Lösung führt zu einem schrittweisen reversiblen Anstieg der Emissions Intensität. Dieser Anstieg wird von einem gleichzeitigen irreversiblen schrittweisen Abfall der Emissionsintensität begleitet. Leider ist das System nur geeignet, Adsorptionen bis maximal 100nm Länge aufzulösen. Eine detaillierte Analyse ist daher schwer. Trotzdem wird vermutet, dass es sich bei dem langsamen Prozess um das Ausbilden von π -Stapeln handelt, wobei der schnelle Prozess mit der nicht-kovalenten Bindung der Polymer-Seitenketten an die Oberfläche assoziiert wird. Obwohl über die eigentliche Bindung des Polymers nur Vermutungen angestellt werden können, so wirft die Untersuchung doch einen Fokus auf die Wahl des Lösungsmittels, da diese Entscheidung einen viel größeren Effekt verursacht, als die Bindung des Polymers selbst. Diese Arbeit stellt fundamentale Betrachtungen zur Adsorption von verschiedenen Molekülen an Kohlenstoffnanoröhren auf. Die Betrachtungen wurden mit festen, flüssigen und gasförmigen Molekülen durchgeführt. Die Ergebnisse zeigen, dass Nanoröhren geeignet sind, als Molekül-Sensoren verwendet zu werden, da sie stark auf Änderungen in ihrer Umgebung reagieren können. Weiterhin wurden Lösungsmittel und Eigenschaften aufgezeigt, die die Quanteneffizienz signifikant beeinflussen. Eine Anwendung in der biologischen Mikroskopie ist denkbar, genauso wie für eine effizientere und sicherere Fernmeldeinfrastruktur. Weiterhin wurden Wege aufgezeigt, Super-Kondensatoren auf Nanorohr-Basis zu bauen, die als Anwendung in einem Kohlenstoffnanorohr-basierenden Computer von Interesse sein könnten. Obwohl die Erkenntnisse fundamental sind, zeigen diese Studien, dass es mit bestimmten Tricks möglich ist, den Raum am unteren Ende der Nanometerskala zu erforschen und zu entdecken.

Dans le contexte des écoulements micro- et nano-fluidiques, ce travail porte sur l'étude des interactions à l'interface entre des flux de gaz rares et des surfaces métalliques via une approche de modélisation multi-physique et multi-échelle. Elle se concentre tout particulièrement sur l'interaction entre l'argon et une surface d'or. Pour ce faire la modélisation a été effectuée en deux étapes, une première partie utilisant la mécanique quantique à l'échelle atomique et une deuxième partie de dynamique moléculaire à l'échelle nanométrique. La première partie est consacrée à l'obtention de potentiels d'interaction entre un atome d'argon et les atomes d'or de la surface par des méthodes de calculs théoriques basés sur la DFT comportant des effets à longues distances. Deux approches, donnant des résultats comparables, ont été utilisées : la première est liée à la description périodique de la surface d'or par un modèle basé sur la description des électrons par des ondes planes alors que la seconde permet de récupérer séparément les parties répulsives et attractives de l'interaction d'un atome d'argon avec un petit cluster d'or. Ces potentiels d'interactions ont été décomposés en potentiels de paires Ar-Au utilisables par des simulations de dynamique moléculaire. Ces simulations ont consisté en la projection d'atomes d'argon sur des surfaces d'or ‘parfaites' dites lisses ou des surfaces rugueuses plus représentatives de la technologie actuelle. L'analyse statistique des vitesses réfléchies permet de déterminer le coefficient d'accommodation tangentiel de l'argon sur des surfaces d'or. Ce coefficient est la traduction du phénomène de glissement qui peut ainsi être modélisé dans une description plus macroscopique de l'écoulement d'un gaz dans une micro-conduite. L'approche multi-physique utilisée dans ce travail a permis la détermination numérique de coefficients d'accommodations tangentiels très précis et comparables à l'expérience pour le couple argon-or, et doit pouvoir être appliquée à d'autres couples / In the context of micro- and nano-flows, this work concentrates on the study of interactions at the interface of noble gas and metal surfaces by a multi-physics and multiscale model. Particularly, the interaction of an argon atom with a gold surface is the focus of the study. The work has been made in two steps: the first one occurred at the atomic scale in which Quantum Mechanics is employed and the second one at the nanoscale with the use of Molecular Dynamics.The first part of the work was devoted to the determination of interaction potentials between an argon atom and gold atoms from the surface by DFT calculation methods comporting long range effects. Two approaches, leading similar results, have been used: the first one is linked to a periodic description of the gold surface where electrons are defined by plane waves, the second one gives independently repulsive and attractive parts of the interaction of an argon atom with a small gold cluster. Those interaction potentials are then decomposed in pair potentials suitable for Molecular Dynamics simulations. These last ones consisted in multiple times projecting argon atoms on smooth or rough gold surfaces (which are more representative of the roughness of actual technologies). The statistical analysis of the reflected velocities yielded the tangential momentum accommodation (TMAC) coefficient of argon on gold surfaces. This coefficient is the transcription of slip phenomena which occur at the interface, and it can then be used in nano-flow simulations. The multi-physics approach of the thesis gives accurate TMAC values which are comparable to experiments. The accounted method could then be applied to other noble gas metal surface couples

Les nanotubes de carbone (CNT) suscitent un vif intérêt en raison de leurs propriétés intrinsèques remarquables. Cependant, les méthodes de synthèse permettant une production de CNT en grande quantité conduisent à des échantillons le plus souvent impurs, hétérogènes et enchevêtrés, ce qui limite fortement leur développement technologique à grande échelle. Ce travail de thèse se situe en amont des enjeux d'application des CNT et vise à mettre en oeuvre des traitements chimiques efficaces permettant d'améliorer la qualité des échantillons tout en préservant les propriétés des CNT. Nous nous sommes tout d'abord intéressés à l'élimination sélective des impuretés métalliques dans les échantillons par un traitement sous flux de dichore. Un procédé d'intercalation-dispersion-désassemblage a ensuite été appliqué aux échantillons purifiés. Une dernière étape de mise en forme a conduit à un matériau présentant une surface accessible augmentée. La caractérisation poussée des échantillons à l'issue de chaque traitement et à l'aide de techniques variées et complémentaires a permis leur description complète. Nous avons porté une attention particulière à l'analyse des surfaces qui a été menée par volumétrie d'adsorption. Cette technique, particulièrement sensible aux modifications de surfaces liées aux traitements chimiques sur les échantillons de CNT, a permis de caractériser l'évolution des différentes fractions de surface des échantillons en fonction des traitements mis en oeuvre. A l'aide d'une modélisation des mesures de physisorption de krypton il a été possible de quantifier macroscopiquement l'état de désassemblage des faisceaux dans le matériau mis en forme / Due to their superior chemical and physical properties, Carbon NanoTubes (CNTs) and, in particular, Single Walled Carbon Nanotubes (SWNTs) are recognized to have a huge potential in many fields of applications. Nevertheless large scale production of high quality CNT samples is still challenging. The presence of metallic particles and the gathering of CNTs into bundles in as-produced samples constitute strong obstructions for their technological development. In this work, we develop effective chemical treatments to increase the sample purity and reduce the bundle size without damaging the CNT structure. To remove metal-related impurities, we used an alternative purification process which consists in heating the as-produced CNT samples under a chlorine atmosphere. The obtained purified samples were then processed with an intercalation-dispersion-debundling procedure. The dispersed and ramified SWNTs are afterward self-assembled at an air/solvent interface. The obtained assembled SWNTs show an improved adsorption capacity and increased accessible surfaces compared to those of the as-produced SWNTs. The precise characterization of samples by means of complementary techniques after each treatment constitutes an important part of this work. In particular, surface analyses were carried out by adsorption volumetry, which is particularly sensitive to surface modifications related to chemical treatments. By means of the modeling of krypton adsorption measurements, we quantify the debundling state - at a macroscopic scale - of the processed CNT samples

Many methods have been proposed for efficient storage of molecular hydrogen for fuel cell applications. However, despite intense research efforts, so far, the industrial parameters of 6.5% mass ratio and 62 kg/m3 volume density are still questionable though the results are obtained by either experimentally or via theoretical simulations on reversible model systems. Carbon-based materials, have always been regarded as the most attractive physisorption substrates for the storage of hydrogen. Theoretical and experimental studies on various model carbon systems, however, failed to reach the elusive goal. In this work, it is shown that insufficiently accurate carbon - hydrogen diatomic interaction potentials, together with the neglect and incomplete treatment of the quantum effects in previous theoretical investigations, led to misleading conclusions for the absorption capacities of different carbon materials. A proper account of the contribution of quantum effects to the free energy and the equilibrium constant for hydrogen adsorption suggest that the industry specifications can be approached in a graphite-based physisorption system. The theoretical prediction can be realised by optimising the topology, the cavity shape and the accessible surface of the carbon structures.

Dans le contexte des écoulements micro- et nano-fluidiques, ce travail porte sur l'étude des interactions à l'interface entre des flux de gaz rares et des surfaces métalliques via une approche de modélisation multi-physique et multi-échelle. Elle se concentre tout particulièrement sur l'interaction entre l'argon et une surface d'or. Pour ce faire la modélisation a été effectuée en deux étapes, une première partie utilisant la mécanique quantique à l'échelle atomique et une deuxième partie de dynamique moléculaire à l'échelle nanométrique. La première partie est consacrée à l'obtention de potentiels d'interaction entre un atome d'argon et les atomes d'or de la surface par des méthodes de calculs théoriques basés sur la DFT comportant des effets à longues distances. Deux approches, donnant des résultats comparables, ont été utilisées : la première est liée à la description périodique de la surface d'or par un modèle basé sur la description des électrons par des ondes planes alors que la seconde permet de récupérer séparément les parties répulsives et attractives de l'interaction d'un atome d'argon avec un petit cluster d'or. Ces potentiels d'interactions ont été décomposés en potentiels de paires Ar-Au utilisables par des simulations de dynamique moléculaire. Ces simulations ont consisté en la projection d'atomes d'argon sur des surfaces d'or ‘parfaites' dites lisses ou des surfaces rugueuses plus représentatives de la technologie actuelle. L'analyse statistique des vitesses réfléchies permet de déterminer le coefficient d'accommodation tangentiel de l'argon sur des surfaces d'or. Ce coefficient est la traduction du phénomène de glissement qui peut ainsi être modélisé dans une description plus macroscopique de l'écoulement d'un gaz dans une micro-conduite. L'approche multi-physique utilisée dans ce travail a permis la détermination numérique de coefficients d'accommodations tangentiels très précis et comparables à l'expérience pour le couple argon-or, et doit pouvoir être appliquée à d'autres couples / In the context of micro- and nano-flows, this work concentrates on the study of interactions at the interface of noble gas and metal surfaces by a multi-physics and multiscale model. Particularly, the interaction of an argon atom with a gold surface is the focus of the study. The work has been made in two steps: the first one occurred at the atomic scale in which Quantum Mechanics is employed and the second one at the nanoscale with the use of Molecular Dynamics.The first part of the work was devoted to the determination of interaction potentials between an argon atom and gold atoms from the surface by DFT calculation methods comporting long range effects. Two approaches, leading similar results, have been used: the first one is linked to a periodic description of the gold surface where electrons are defined by plane waves, the second one gives independently repulsive and attractive parts of the interaction of an argon atom with a small gold cluster. Those interaction potentials are then decomposed in pair potentials suitable for Molecular Dynamics simulations. These last ones consisted in multiple times projecting argon atoms on smooth or rough gold surfaces (which are more representative of the roughness of actual technologies). The statistical analysis of the reflected velocities yielded the tangential momentum accommodation (TMAC) coefficient of argon on gold surfaces. This coefficient is the transcription of slip phenomena which occur at the interface, and it can then be used in nano-flow simulations. The multi-physics approach of the thesis gives accurate TMAC values which are comparable to experiments. The accounted method could then be applied to other noble gas metal surface couples

Many methods have been proposed for efficient storage of molecular hydrogen for fuel cell applications. However, despite intense research efforts, so far, the industrial parameters of 6.5% mass ratio and 62 kg/m3 volume density are still questionable though the results are obtained by either experimentally or via theoretical simulations on reversible model systems. Carbon-based materials, have always been regarded as the most attractive physisorption substrates for the storage of hydrogen. Theoretical and experimental studies on various model carbon systems, however, failed to reach the elusive goal. In this work, it is shown that insufficiently accurate carbon - hydrogen diatomic interaction potentials, together with the neglect and incomplete treatment of the quantum effects in previous theoretical investigations, led to misleading conclusions for the absorption capacities of different carbon materials. A proper account of the contribution of quantum effects to the free energy and the equilibrium constant for hydrogen adsorption suggest that the industry specifications can be approached in a graphite-based physisorption system. The theoretical prediction can be realised by optimising the topology, the cavity shape and the accessible surface of the carbon structures.

Metal-organic materials (MOMs) assembled from metal-based building blocks and organic linkers have attracted much interest due to their large pore dimensions and their enormous structural diversity. In comparison to their inorganic counterparts (zeolites), these crystalline materials can be easily modified to tailor pore dimensions and functionality for specifically targeted properties. The work presented herein encompasses the development of a synthetic 2-step process for the construction of novel families of MOMs or 'platforms' and allow us exquisite design and control over the resulting network topologies. Examples of cationic mesoporous structures were initially exploited, containing carboxylate based centers connected by metal-pyridine bonds. The inherently cationic nets allowed for subsequent anion exchange which can be regarded as an elegant and easy postsynthetic modification strategy. The incorporation of different functionalities inside the channels of the networks was then demonstrated as useful in terms of carbon dioxide capture. The scope of the 2-step process was then expanded to construction of the first trinodal MOM platform involving triangular, tetrahedral and trigonal prismatic building units: tp-PMBB-1-asc. Examples of reticular chemistry are shown which enable the formation of large and functionalized nanocages with retention of the underlying network topology. Gas adsorption studies indicate relatively high uptakes of carbon dioxide and hydrogen which, together with the use of inexpensive ligands, provide an excellent cost/performance ratio of these materials. Moreover, very high stability in organic solvents and especially in water are addressed which is a particularly challenging, but industrially relevant target in the field of Metal-Organic Materials. The 2-step approach was also used to synthesize a new and versatile class of metal-organic materials with augmented lonsdaleite-e (lon-e-a) topology. This family of lon-e nets is built by pillaring of hexagonal 2-dimensional kagomé (kag) lattices that are in turn pillared by a trigonal prismatic Primary Molecular Building Block (tp-PMBB-1). These MOMs represent the first examples of axial-to-axial-pillared undulating kag layers and they are readily fine-tuned because the bdc2- moieties can be varied at their 5-position without changing the overall structure. This lon-e platform possesses functionalized hexagonal channels since the kag lattices are necessarily eclipsed. The effect of the substituent at the 5-positions of the bdc2- linkers upon gas adsorption, particularly the heats of adsorption of carbon dioxide and methane, were studied. If linear dicarboxylates were instead utilized, we were able to synthesize a new and versatile class of metal-organic materials that exhibits 4,6-connected fsb topology. These networks are constructed from simple and inexpensive building units and since interpenetration is precluded, afford very high void volumes. They therefore represent ideal targets to generate a novel family of frameworks, because of the ready availability functionalized and expanded ligand derivatives. They also allow for systematic fine tuning and could ultimately provide a roadmap to ultra-high surface areas from simple building blocks.

Die vorliegende Arbeit stellt Ergebnisse von Monte-Carlo-Simulationen zur Adsorption und Selbstorganisation amphiphiler Moleküle an Feststoffoberflächen vor. Ziel der Arbeit ist die Untersuchung des Zusammenhanges zwischen Moleküleigenschaften und thermodynamischen Bedingungen für die Bildung von adsorbierten Aggregaten. Im Rahmen eines coarse grainined-Gittermodells wird die Adsorption von Modelltensiden auf ebenen Oberflächen beschrieben. Es werden hydrophile, hydrophobe und chemisch heterogene Modelloberflächen berücksichtigt. Die Resultate der Simulationen stehen im Einklang mit experimentellen Untersuchungen und liefern Interpretationshilfen für die beobachteten Strukturen. Für den Einsatz von Tensidmischungen bei der Kalziumfluorit-Flotation konnte gezeigt werden, dass die Wirkung des Co-Sammler-Tensids auf einer Adsolubilisation im Adsorptionsfilm beruht.