Technische Universität Dresden: Qucosa
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    12475 research outputs found

    An experimental-analytical scale-linking study on the crack-bridging mechanisms in different types of SHCC in dependence on fiber orientation

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    A scale-linking, experimental study complemented by an analytical model was carried out to investigate the influence of fiber orientation on the crack-opening behavior of strain-hardening cement-based composites (SHCC). Three SHCC compositions were investigated with polyvinyl alcohol (PVA) and ultra-high molecular weight polyethylene (UHMWPE) fibers in combination with normal- and high-strength matrices. The micromechanical experiments with fiber inclinations of 0◦, 30◦, 45◦, and 60◦ involved fiber embedment in plain and fiber-reinforced specimens. The experimentally derived micromechanical parameters were input into an analytical crack-bridging model to assess the upscaling accuracy of the micromechanical results by comparing the predicted crack-bridging laws to the single-crack opening behavior of equivalent miniature SHCC specimens with controlled fiber orientation. This study yields new insights into the effect of fiber orientation on the crackbridging properties of different types of SHCC, assesses the link between micromechanical and composite scale properties, offers a solid experimental basis for refining the analytical models, and developing anisotropic materials models for SHCC in dependence on fiber orientation

    Balancing Performance and Energy for Lightweight Data Compression Algorithms

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    Energy consumption becomes more and more a critical design factor, whereby performance is still an important requirement. Thus, a balance between performance and energy has to be established. To tackle that issue for database systems, we proposed the concept of work-energy profiles. However, generating such profiles requires extensive benchmarking. To overcome that, we propose to approximate work-energy-profiles for complex operations based on the profiles of low-level operations in this paper. To show the feasibility of our approach, we use lightweight data compression algorithms as complex operations, since compression as well as decompression are heavily used in in-memory database systems, where data is always managed in a compressed representation. Furthermore, we evaluate our approach on a concrete hardware system

    Development of an in vitro blood flow model to evaluate antimicrobial coatings for blood-contacting devices

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    Pre-clinical evaluation of novel antimicrobial coatings for blood-contacting devices commonly relies on the performance of animal studies since alternative in vitro models do not adequately represent the interactions between blood, bacteria, and material surfaces as they occur in vivo. To reduce the need of these cost-intensive and controversial animal tests, this project was dedicated to the development of a new model setup that overcomes this limitation and allows in vitro evaluation under in vivo-like conditions. This newly developed model was intended to be directly applied to evaluate recently in-house developed antimicrobial coatings, so-called anchor polymers. Therefore, the project was divided into two parts. The first part of the project focused on the evaluation of the anchor polymer coatings concerning their applicability in blood-contacting devices. For this purpose, the PEGylated styrene-maleic acid copolymers were intensively studied using established laboratory tests. These examinations showed very promising results regarding adsorption and stability on relevant polymer substrates, antimicrobial efficacy, and biological safety of the coatings, thus revealing their great potential for future applications in medical devices. Moreover, this basic characterization was meant to allow a subsequent comparison of the new in vitro model with state-of-the-art in vitro tests. The second part of the thesis focused on the development of the realistic in vitro model. Here, a single-pass flow system realized the implementation of adjustable flow conditions. Furthermore, incubation with freshly drawn human blood provided a physiological nutrient environment and included the influence of an immune response. Staphylococcus aureus were chosen as representative microorganisms, as they are responsible for a majority of device-related blood stream infections. The resulting blood flow model was validated with one anti-adhesive and one contact-killing anchor polymer coating, confirming the model’s ability to differentiate the investigated surfaces. Inflammatory and coagulant blood activation correlated slightly with bacterial coverage, which in turn was strongly dependent on the investigated material surface. Incubation with varying flow conditions demonstrated the model’s capability to reflect the well-documented dependence of bacterial colonization and occurring flow conditions. In contrast to the state-of-the-art in vitro tests, the simultaneous incubation of test surface, bacteria and whole blood allowed the analysis of mutual interactions of the three parameters. Thus, the model represents an excellent method for pre-clinical evaluation of novel antimicrobial coatings for blood-contacting devices

    Hydration and ion pair formation in common aqueous La(III) salt solutions: a Raman scattering and DFT study

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    Raman spectra of aqueous lanthanum perchlorate, triflate (trifluorosulfonate), chloride and nitrate solutions were measured over a broad concentration (0.121–3.050 mol Lˉ¹) range at room temperature (23 °C). A very weak mode at 343 cmˉ¹ with a full width at half height at 49 cmˉ¹ in the isotropic spectrum suggests that the nona-aqua La(III) ion is thermodynamically stable in dilute perchlorate solutions (∼0.2 mol Lˉ¹) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The La³⁺ nona-hydrate was also detected in a 1.2 mol Lˉ¹ La(CF₃SO₃)₃(aq). In lanthanum chloride solutions chloro-complex formation was detected over the measured concentration range from 0.5–3.050 mol Lˉ¹. The chloro-complexes in LaCl₃(aq) are fairly weak and disappear with dilution. At a concentration <0.1 mol Lˉ¹ almost all complexes disappeared. In LaCl₃ solutions, with additional HCl, a series of chloro-complexes of the type [La(OH₂)₉₋nCln]⁺³⁻ⁿ (n = 1–3) were formed. The La(NO₃)₃(aq) spectra were compared with a spectrum of a 0.409 mol Lˉ¹ NaNO₃(aq) and it was concluded that in La(NO₃)₃(aq) over the concentration range from 0.121–1.844 mol Lˉ¹, nitrato-complexes, [La(OH₂)₉₋n-(NO₃)n]⁺³⁻ⁿ (n = 1, 2) were formed. These nitrato-complexes are quite weak and disappear with dilution <0.01 mol Lˉ¹. DFT geometry optimizations and frequency calculations are reported for a lanthanumnona-hydrate with a polarizable dielectric continuum in order to take the solvent into account. The bond distances and angles for the cluster geometry of [La(OH₂)₉]³⁺ with the polarizable dielectric continuum are in good agreement with data from recent structural experimental measurements and high quality simulations. The DFT frequency of the La–O stretching mode at 328.2 cmˉ¹, is only slightly smaller than the experimental one

    Dynamics of Rydberg atom lattices in the presence of noise and dissipation

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    The work presented in this dissertation concerns dynamics of Rydberg atom lattices in the presence of noise and dissipation. Rydberg atoms possess a number of exaggerated properties, such as a strong van der Waals interaction. The interplay of that interaction, coherent driving and decoherence leads to intriguing non-equilibrium phenomena. Here, we study the non-equilibrium physics of driven atom lattices in the presence of decoherence caused by either laser phase noise or strong decay. In the first case, we compare between global and local noise and explore their effect on the number of excitations and the full counting statistics. We find that both types of noise give rise to a characteristic distribution of the Rydberg excitation number. The main method employed is the Langevin equation but for the sake of efficiency in certain regimes, we use a Markovian master equation and Monte Carlo rate equations, respectively. In the second case, we consider dissipative systems with more general power-law interactions. We determine the phase diagram in the steady state and analyse its generation dynamics using Monte Carlo rate equations. In contrast to nearest-neighbour models, there is no transition to long-range-ordered phases for realistic interactions and resonant driving. Yet, for finite laser detunings, we show that Rydberg atom lattices can undergo a dissipative phase transition to a long-range-ordered antiferromagnetic phase. We identify the advantages of Monte Carlo rate equations over mean field predictions. Having studied the dynamics of Rydberg atom lattices, we study an application of the strong interactions in such systems for quantum information processing. We investigate the coherent exchange of a single photon between a superconducting microwave cavity and a lattice of strongly interacting Rydberg atoms in the presence of local electric field fluctuations plaguing the cavity surface. We show that despite the increased sensitivity of Rydberg states to electric fields, as compared to ground state atoms, the Rydberg dipole-dipole interaction can be used to protect the system against the dephasing induced by the local noise. Using 1/f1/f and laser phase noise models, we show that compared to the case with non-interacting atoms, our system exhibits longer coherence lifetimes and larger retrieval efficiency of the photon after storing into the atoms

    Incorporating Fresnel-Propagation into Electron Holographic Tomography: A possible way towards three-dimensional atomic resolution

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    Tomographic electron holography combines tomography, the reconstruction of three-dimensionally resolved data from multiple measurements with different specimen orientations, with electron holography, an interferometrical method for measuring the complex wave function inside a transmission electron microscope (TEM). Due to multiple scattering and free wave propagation conventional, ray projection based, tomography does perform badly when approaching atomic resolution. This is remedied by incorporating propagation effects into the projection while maintaining linearity in the object potential. Using the Rytov approach an approximation is derived, where the logarithm of the complex wave is linear in the potential. The ray projection becomes a convolution with a Fresnel propagation kernel, which is considerably more computationally expensive. A framework for such calculations has been implemented in Python. So has a multislice electron scattering algorithm, optimised for large fields of view and high numbers of atoms for simulations of scattering at nanoparticles. The Rytov approximation gives a remarkable increase in resolution and signal quality over the conventional approach in the tested system of a tungsten disulfide nanotube. The response to noise seems to be similar as in conventional tomography, so rather benign. This comes at the downside of much longer calculation time per iteration.Tomographische Elektronenholographie kombiniert Tomographie, die Rekonstruktion dreidimensional aufgelößter Daten aus einem Satz von mehreren Messungen bei verschiedenen Objektorientierungen, mit Elektronenholographie, eine interferrometrische Messung der komplexen Elektronenwelle im Transmissionselektronenmikroskop (TEM). Wegen Mehrfachstreuung und Propagationseffekten erzeugt konventionelle, auf einer Strahlprojektion basierende, Tomography ernste Probleme bei Hochauflösung hin zu atomarer Auflösung. Diese sollen durch ein Modell, welches Fresnel-Propagation beinhaltet, aber weiterhin linear im Potential des Objektes ist, vermindert werden. Mit dem Rytov-Ansatz wird eine Näherung abgeleitet, wobei der Logarithmus der komplexen Welle linear im Potential ist. Die Strahlen-Projektion ist dann eine Faltung mit dem Fresnel-Propagations-Faltungskernel welche rechentechnisch wesentlich aufwendiger ist. Ein Programm-Paket für solche Rechnungen wurde in Python implementiert. Weiterhin wurde ein Multislice Algorithmus für große Gesichtsfelder und Objekte mit vielen Atomen wie Nanopartikel optimiert. Die Rytov-Näherung verbessert sowohl die Auflösung als auch die Signalqualität immens gegenüber konventioneller Tomographie, zumindest in dem getesteten System eines Wolframdisulfid-Nanoröhrchens. Das Rauschverhalten scheint ähnlich der konventionallen Tomographie zu sein, also eher gutmütig. Im Gegenzug braucht die Tomographie basierend auf der Rytov-Näherung wesentlich mehr Rechenzeit pro Iteration

    Developing a Decision Making Approach for District Cooling Systems Design using Multi-objective Optimization

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    Energy consumption rates have been dramatically increasing on a global scale within the last few decades. A significant role in this increase is subjected by the recent high temperature levels especially at summer time which caused a rapid increase in the air conditioning demands. Such phenomena can be clearly observed in developing countries, especially those in hot climate regions, where people depend mainly on conventional air conditioning systems. These systems often show poor performance and thus negatively impact the environment which in turn contributes to global warming phenomena. In recent years, the demand for urban or district cooling technologies and networks has been increasing significantly as an alternative to conventional systems due to their higher efficiency and improved ecological impact. However, to obtain an efficient design for district cooling systems is a complex task that requires considering a wide range of cooling technologies, various network layout configuration possibilities, and several energy resources to be integrated. Thus, critical decisions have to be made regarding a variety of opportunities, options and technologies. The main objective of this thesis is to develop a tool to obtain preliminary design configurations and operation patterns for district cooling energy systems by performing roughly detailed optimizations and further, to introduce a decision-making approach to help decision makers in evaluating the economic aspects and environmental performance of urban cooling systems at an early design stage. Different aspects of the subject have been investigated in the literature by several researchers. A brief survey of the state of the art was carried out and revealed that mathematical programming models were the most common and successful technique for configuring and designing cooling systems for urban areas. As an outcome of the survey, multi objective optimization models were decided to be utilized to support the decision-making process. Hence, a multi objective optimization model has been developed to address the complicated issue of decision-making when designing a cooling system for an urban area or district. The model aims to optimize several elements of a cooling system such as: cooling network, cooling technologies, capacity and location of system equipment. In addition, various energy resources have been taken into consideration as well as different solar technologies such as: trough solar concentrators, vacuum solar collectors and PV panels. The model was developed based on the mixed integer linear programming method (MILP) and implemented using GAMS language. Two case studies were investigated using the developed model. The first case study consists of seven buildings representing a residential district while the second case study was a university campus district dominated by non-residential buildings. The study was carried out for several groups of scenarios investigating certain design parameters and operation conditions such as: Available area, production plant location, cold storage location constraints, piping prices, investment cost, constant and variable electricity tariffs, solar energy integration policy, waste heat availability, load shifting strategies, and the effect of outdoor temperature in hot regions on the district cooling system performance. The investigation consisted of three stages, with total annual cost and CO2 emissions being the first and second single objective optimization stages. The third stage was a multi objective optimization combining the earlier two single objectives. Later on, non-dominated solutions, i.e. Pareto solutions, were generated by obtaining several multi objective optimization scenarios based on the decision-makers’ preferences. Eventually, a decision-making approach was developed to help decision-makers in selecting a specific solution that best fits the designers’ or decision makers’ desires, based on the difference between the Utopia and Nadir values, i.e. total annual cost and CO2 emissions obtained at the single optimization stages.Die Energieverbrauchsraten haben in den letzten Jahrzehnten auf globaler Ebene dramatisch zugenommen. Diese Erhöhung ist zu einem großen Teil in den jüngst hohen Temperaturniveaus, vor allem in der Sommerzeit, begründet, die einen starken Anstieg der Nachfrage nach Klimaanlagen verursachen. Solche Ereignisse sind deutlich in Entwicklungsländern zu beobachten, vor allem in heißen Klimaregionen, wo Menschen vor allem konventionelle Klimaanlagensysteme benutzen. Diese Systeme verfügen meist über eine ineffiziente Leistungsfähigkeit und wirken sich somit negativ auf die Umwelt aus, was wiederum zur globalen Erwärmung beiträgt. In den letzten Jahren ist die Nachfrage nach Stadt- oder Fernkältetechnologien und -Netzwerken als Alternative zu konventionellen Systemen aufgrund ihrer höheren Effizienz und besseren ökologischen Verträglichkeit satrk gestiegen. Ein effizientes Design für Fernkühlsysteme zu erhalten, ist allerdings eine komplexe Aufgabe, die die Integration einer breite Palette von Kühltechnologien, verschiedener Konfigurationsmöglichkeiten von Netzwerk-Layouts und unterschiedlicher Energiequellen erfordert. Hierfür ist das Treffen kritischer Entscheidungen hinsichtlich einer Vielzahl von Möglichkeiten, Optionen und Technologien unabdingbar. Das Hauptziel dieser Arbeit ist es, ein Werkzeug zu entwickeln, das vorläufige Design-Konfigurationen und Betriebsmuster für Fernkälteenergiesysteme liefert, indem aureichend detaillierte Optimierungen durchgeführt werden. Zudem soll auch ein Ansatz zur Entscheidungsfindung vorgestellt werden, der Entscheidungsträger in einem frühen Planungsstadium bei der Bewertung städtischer Kühlungssysteme hinsichtlich der wirtschaftlichen Aspekte und Umweltleistung unterstützen soll. Unterschiedliche Aspekte dieser Problemstellung wurden in der Literatur von verschiedenen Forschern untersucht. Eine kurze Analyse des derzeitigen Stands der Technik ergab, dass mathematische Programmiermodelle die am weitesten verbreitete und erfolgreichste Methode für die Konfiguration und Gestaltung von Kühlsystemen für städtische Gebiete sind. Ein weiteres Ergebnis der Analyse war die Festlegung von Mehrzieloptimierungs-Modelles für die Unterstützung des Entscheidungsprozesses. Darauf basierend wurde im Rahmen der vorliegenden Arbeit ein Mehrzieloptimierungs-Modell für die Lösung des komplexen Entscheidungsfindungsprozesses bei der Gestaltung eines Kühlsystems für ein Stadtgebiet oder einen Bezirk entwickelt. Das Modell zielt darauf ab, mehrere Elemente des Kühlsystems zu optimieren, wie beispielsweise Kühlnetzwerke, Kühltechnologien sowie Kapazität und Lage der Systemtechnik. Zusätzlich werden verschiedene Energiequellen, auch solare wie Solarkonzentratoren, Vakuum-Solarkollektoren und PV-Module, berücksichtigt. Das Modell wurde auf Basis der gemischt-ganzzahlig linearen Optimierung (MILP) entwickelt und in GAMS Sprache implementiert. Zwei Fallstudien wurden mit dem entwickelten Modell untersucht. Die erste Fallstudie besteht aus sieben Gebäuden, die ein Wohnviertel darstellen, während die zweite Fallstudie einen Universitätscampus dominiert von Nichtwohngebäuden repräsentiert. Die Untersuchung wurde für mehrere Gruppen von Szenarien durchgeführt, wobei bestimmte Designparameter und Betriebsbedingungen überprüft werden, wie zum Beispiel die zur Verfügung stehende Fläche, Lage der Kühlanlage, örtliche Restriktionen der Kältespeicherung, Rohrpreise, Investitionskosten, konstante und variable Stromtarife, Strategie zur Einbindung der Solarenergie, Verfügbarkeit von Abwärme, Strategien der Lastenverschiebung, und die Wirkung der Außentemperatur in heißen Regionen auf die Leistung des Kühlsystems. Die Untersuchung bestand aus drei Stufen, wobei die jährlichen Gesamtkosten und die CO2-Emissionen die erste und zweite Einzelzieloptimierungsstufe darstellen. Die dritte Stufe war ein Pareto-Optimierung, die die beiden ersten Ziele kombiniert. Im Anschluss wurden nicht-dominante Lösungen, also Pareto-Lösungen, erzeugt, indem mehrere Pareto-Optimierungs-Szenarien basierend auf den Präferenzen der Entscheidungsträger abgebildet wurden. Schließlich wurde ein Ansatz zur Entscheidungsfindung entwickelt, um Entscheidungsträger bei der Auswahl einer bestimmten Lösung zu unterstützen, die am besten den Präferenzen des Planers oder des Entscheidungsträgers enstpricht, basierend auf der Differenz der Utopia und Nadir Werte, d.h. der jährlichen Gesamtkosten und CO2-Emissionen, die Ergebnis der einzelnen Optimierungsstufen sind

    Investigations on the parent compounds of Fe-chalcogenide superconductors

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    This work is focused on the parent compounds of the Fe-chalcogenide superconductors. For this purpose poly- and single-crystalline forms of tetragonal β-FexSe, Fe1+yTe, Fe1+yTe1-xSex and Fe(1+y)-xMxTe (M = Ni, Co) have been prepared. Second focal points of this study are the low-temperature structural phase transitions and physical property changes in tetragonal Fe1+yTe which are induced by composition, external pressure, and cationic substitution

    Development of new hybrid yarn construction from recycled carbon fibers (rCF) for high performance composites: Part-II: Influence of yarn parameters on tensile properties of composites

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    This article reports the successful manufacturing of hybrid yarns from virgin staple CF (40 or 60 mm) or recycled staple CF (rCF) by mixing with polyamide 6 (PA 6) fibers of defined length. The hybrid yarns are produced using an optimized process route of carding, drawing, and flyer machine. Furthermore, the influence of CF length, CF type (i.e. virgin or rCF), CF volume content, and twist of the yarn are also investigated regarding the tensile properties of unidirectionally laid (UD) thermoplastic composites. The results show that CF length, yarn twist, and CF content of composites play a big role on the tensile properties of thermoplastic composites. From the comparison of tensile strength of UD composites produced from 40 and 60mm virgin staple CF, it can be seen that the increase of yarn twist decreases the tensile strength. However, the effect of twist on the tensile properties of UD composites manufactured from 40mm virgin staple CF is insignificant. The tensile strength of UD thermoplastic composites manufactured from the hybrid yarn with 40 and 60mm virgin staple CF and rCF is found to be 771 ± 100, 838 ± β1, and 801 ± 53.4 MPa, respectively, in the case of 87 T/m containing 50 volume% CF

    From Single Colloidal Particles to Coupled Plasmonic Systems

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    By down-sizing noble metals to the nanoscale, striking new optical properties arise—investigated in the scientific field of plasmonics. The steady rise of developments, innovations, and interest in plasmonics is directly linked with the much broader field of (colloidal) nanotechnology and its breakthroughs. In order to harvest the full potential of colloidal plasmonics, optimizing the synthesis of colloidal nanoparticles, controlling the subsequent assembly of them into complex architectures, and fully understanding the emerging plasmonic properties is inevitable. Wet-chemical seed-mediated growth of colloidal building blocks and colloidal self-assembly offer the tool-sets to tackle the challenges of plasmonic applications. Due to the intrinsic properties of colloids and the resulting (coupled) assemblies, distinct differences are evident in comparison to top-down fabrication based plasmonics. Among these properties, this thesis focuses on the true three-dimensionality of colloids—in vast contrast, top-down processes always rely on stacking of layered architectures. Strong plasmonic coupling interactions are predominantly defined by the inter-particle distances and the geometry of the cross section area by which adjacent particles interact. Consequently, unique plasmonic features emerge from the three-dimensional structure of colloids and the possibility to tune the dielectric environment by surface functionalization. The objective of this work is to investigate and understand the plasmonics of coupled colloidal systems. Following this scope, the first part of this thesis introduces a new synthetic concept, which thereby aims to provide colloidal building blocks for plasmonic assemblies. The optical quality and spectral range can be boosted by applying silver nanoparticles instead of gold as plasmonic material. Herein, a general synthetic concept is introduced resulting in monodispersed and shape-pure silver nanoparticles in a highly controlled manner. By transferring the concept of living polymerization reactions to nanoparticle growth, secondary nucleation is successfully suppressed and the particle dimensions are freely tunable. Finally, chemical stability toward oxidation and functionalization reactions is obtained by covering silver particles with a sub-skin depth gold shell. The second part summarizes the plasmonic properties arising from coupled particle assemblies fabricated by colloidal self-assembly. Therefore, the complexity of the coupled systems was systematically increased to observe the transition from local to collective coupling interactions. Starting from metallic film-coupled gold nanorods, the presence of a highly sensitive magnetic mode and its impact on the magnetic permeability were investigated. Next, the transition from local to collective coupling was observed by stepwise increase of the number of particles in a linear gold nanoparticle chain revealing the formation of a plasmon band in quasi-infinite particle chains. Consequently, this work aims to advance the field of colloidal metasurfaces by optimizing the building blocks and by further comprehending the plasmonic coupling effects in colloidal assemblies.Durch das Herunterskalieren von (Edel-)Metallen in den Nanometerbereich entstehen neue optische Eigenschaften, die im Wissenschaftsfeld der Plasmonik untersucht werden. Die stetige Weiterentwicklung, Innovation, und das steigende Interesse an der Plasmonik ist direkt mit dem weiter gefassten Gebiet der (kolloidalen) Nanotechnologie verbunden. Um das Potenzial der kolloidalen Plasmonik voll ausschöpfen zu können, ist es unumgänglich, die Synthese kolloidaler Nanopartikel zu optimieren, deren anschließende Anordnung zu komplexen Architekturen gezielt zu steuern, und die entstehenden plasmonischen Effekte vollständig zu verstehen. Das nasschemische Keim-vermittelte Wachstum kolloidaler Bausteine und die kolloidale Selbstanordnung bieten die geeigneten Werkzeuge für plasmonische Anwendungen. Aufgrund der intrinsischen Eigenschaften kolloidaler Partikel und den daraus resultierenden optischen Eigenschaften ihrer Anordnungen, ergeben sich deutliche Unterschiede zur Plasmonik von Top-down Systemen. Im Gegensatz zu diesen Systemen, die immer aus geschichteten Architekturen bestehen, handelt es sich bei kolloidalen Systemen um echte dreidimensionale Objekte. Starke plasmonische Kopplungswechselwirkungen werden hauptsächlich durch die Abstände zwischen Partikeln und die Geometrie des Querschnitts definiert, über die benachbarte Partikel interagieren. Folglich ergeben sich aus der dreidimensionalen Struktur von kolloidalen Nanopartikeln und der Möglichkeit, diese mit verschiedenen dielektrischen Umgebung zu funktionalisieren, einzigartige plasmonische Effekte. Das übergeordnete Ziel dieser Arbeit besteht darin, die plasmonischen Effekte gekoppelter kolloidaler Systeme zu untersuchen und besser zu verstehen. Diesem Ziel folgend, wird im ersten Teil der Arbeit ein neues Synthesekonzept vorgestellt, das darauf abzielt geeignete kolloidale Bausteine für plasmonische Anordnungen zur Verfügung zu stellen. Verglichen mit Gold als Bausteinmaterial kann die optische Qualität und der Spektralbereich durch Nutzung der überlegenen plasmonischen Eigenschaften von Silbernanopartikeln gesteigert werden. Hier wurde ein allgemeines Synthesekonzept entwickelt, das auf kontrollierte Weise zu monodispersen und formreinen Silbernanopartikeln führt. Durch die Übertragung des Konzepts lebender Polymerisationsreaktionen auf das Nanopartikelwachstum, werden Nebenreaktionen (z.B. sekundäre Keimbildung) erfolgreich unterdrückt und die Partikelgröße wird dadurch genau einstellbar. Schließlich wurde durch die Überwachsung der Silberpartikel mit einer Goldschale unterhalb der Leitschichtdicke chemische Stabilität gegenüber Oxidations- und Funktionalisierungsreaktionen erhalten. Im zweiten Teil werden die plasmonischen Eigenschaften gekoppelter Partikelanordnungen untersucht. Dafür wurde die Komplexität der gekoppelten Systeme systematisch erhöht, um den Übergang von lokalen zu kollektiven Kopplungsinteraktionen zu beobachten. Ausgehend von Goldstäbchen, die mit einem Metallfilm gekoppelt sind, wurde eine hochempfindliche magnetische Mode nachgewiesen und deren Einfluss auf die magnetische Permeabilität untersucht. Desweiteren wurde der direkte Übergang von lokaler zu kollektiver Kopplung durch schrittweise Erhöhung der Anzahl der Partikel in einer linearen Goldnanopartikelkette beobachtet, was zur Bildung eines Plasmonenbandes für quasi-unendlich lange Partikelketten führt. Letztendlich ist das Ziel dieser Arbeit, kolloidale Metaoberflächen durch Optimierung der Bausteine und durch besseres Verständnis der plasmonischen Kopplungseffekte voranzubringen


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