Successful design and application of nanoporous materials are essentially dependent on the molecular diffusion. Two mechanisms, i.e. surface barriers and intracrystalline diffusion, may dominate the mass transport. In the previous studies, these two mechanisms are difficult to determine with certainty by dual resistance model [1] (DRM). Here, we derive an expression of uptake rate relying solely on surface permeability, which provides a method to directly quantify the surface barriers. Subsequently, the effects of surface barriers and intracrystalline diffusion could be identified separately.

Die Tumorprogression wird von Veränderungen der Gewebemorphologie begleitet. In 2D-Zellkulturen wurden verschiedene Gewebezustände gefunden, z.B. flüssigar- tige, 'gejammete' sowie nematische Zustände, die mit den Zellformen zusammen- hingen. Obwohl man diese Resultate nicht einfach auf dreidimensionale Gewebe wie Tumore übertragen kann, legen sie nahe, den Zusammenhang von Zellformen, Gewebemorphologie und Aggregatzustand von 3D-Geweben zu untersuchen. Ich untersuche Zellbeweglichkeit in 3D-Sphäroiden, wobei ich einen krebsartigen (ma- lignen) und einen nicht-krebsartigen Zelltyp miteinander vergleiche. Ich analysiere sowohl das Gesamtverhalten des Gewebes durch Sphäroid-Fusionsexperimente als auch Einzel-Zell-Bewegungen, und zeige damit dass das maligne Gewebe durch aktive, bewegliche Zellen verflüssigt wird, wohingegen das epitheliale (gesunde) Gewebe sich eher verhält wie ein Festkörper. Eine komplette 3D-Segmentation der Proben zeigt, dass sich im flüssigen Gewebe mehr elongierte Zellen befinden, was Zellformen mit Zellmotilität verbindet. Ich finde somit zwei aktive Zustände in 3D- Geweben: einen amorphen, glas-artigen, der Züge von Zell-Jamming trägt; sowie einen ungeordneten, flüssigen Zustand. Darüber hinaus demonstriere ich einen en- gen Zusammenhang zwischen Zellformen und Kernformen in beiden Gewebearten. Zum ersten Mal kann damit eine Verbindung von Krebs-Grading in histologischen Schnitten mit der Physik des Jamming hergestellt werden, womit sich die Tür zu klinischen Anwendungen im diagnostischen Bereich öffnet.

The worldwide growing demand for clean energy leads to necessity for new energy generation methods. Nuclear power generators are an excellent solution for these demands. The feasibility of nuclear power production depends on the performance of structural materials under the harsh conditions in nuclear reactors such as high radiation flux and high temperature. The development of structural materials to withstand such conditions is a big challenge and crucial for advanced nuclear fission and fusion reactors. Several materials are developed, amongst them Oxide Dispersion Strengthened (ODS) steels also called Nanostructured Ferritic Alloys (NFA). NFA consist of Fe-Cr based ferritic/martensitic steels that contain highly dispersed nanometer-size Y-Ti-O nanoclusters, and are manufactured via powder metallurgy. The presence of nanoclusters leads to high temperature stability and radiation resistance. Despite many research activities using advanced analytical techniques such as Transmission Electron Microscopy and Atom Probe Tomography as well as theoretical calculations many properties of the nanoclusters, such as the detailed atomic structure and composition as well as their efficiency for trapping He, vacancies and self-interstitial atoms (SIA), are still not completely understood. In the first part of this thesis work, six different structural models for atomic clusters in bcc Fe which may contain O, Y, Ti, and vacancies (v) are investigated by Density Functional Theory (DFT) calculations. Results for clusters with identical numbers of constituents (O, Y, Ti, and v) are compared. The most important finding consists in the statement that the data on the stability or energetics of the relaxed clusters are comparable although their atomic configurations are often different. This contradicts the prevailing opinion in the related theoretical literature that favors the so-called structure-matching model, which is also investigated in this work. In all studied cases, the absolute value of the total binding energy per cluster constituent becomes lower if Y is partially replaced by Ti, i.e. the driving force for the growth of O-Y clusters is higher than that of O-Y-Ti clusters. This may be correlated with the experimental observation that the presence of Ti leads to a reduction of the size of the oxide clusters in NFA and to a higher dispersion. A further major result is the finding that cage-like (CL) clusters and clusters with an oxygen atom in the center (cage) have a similar total binding energy. If Ti is not present such clusters are slightly more stable than the corresponding CL clusters. The opposite holds for clusters with Ti. It is also shown that adding O atoms to CL cluster leads to structures with O in the center. Vacancies are an important for the stabilization of the cluster due to the very strong binding with O. We infer that the Ov pair may be the origin for cluster nucleation growth. Because of limited computational resources, the dimension of clusters investigated by DFT is still below or close to the limit of the experimental resolution of methods allowing for a simultaneous determination of atomic structure and composition of the clusters. These small clusters may be considered as nuclei for further structural evolution and growth during which a selection of the most favored cluster structures could occur. In the second part of the work four different cluster structures are used to investigate their ability to trap irradiation defects He, v and SIA. These defects are inserted on different positions inside and in the environment of the clusters, the total energy of the corresponding supercell is minimized by DFT, and the binding and incorporation energy of the three kinds of defects is determined. He in the center of a CL cluster is more stable than on interfacial vacant sites (IVS). In CL O-Y clusters, He on an IVS is more stable than in clusters with oxygen in the center, whereas there is no significant difference between the two kinds for clusters with Ti. Up to a distance of 1.5 times the iron lattice constant from the cluster center He is not stable on most of the octahedral and tetrahedral interstitial sites in the Fe matrix. Instead, He is shifted towards positions closer to the cluster. Relaxation occurs to known IVS as well as to previously unknown interfacial interstitial sites (IIS). Moreover, two or three He atoms are placed on sites found to be stable after adding a single He. The corresponding binding and incorporation energies obtained after relaxation are nearly equal to the sum of the values for the interaction with a single He atom. However, placing He dimers or trimers in the environment of a vacancy that belongs to the cluster may also lead to relatively low values of the incorporation energy. Also, He jump barriers between interfacial sites and the center of CL clusters are determined. In the CL O-Y cluster, the barriers are lower than in the CL O-Y-Ti cluster, i.e. trapping and release of He is easier in the former than in the latter. The main reason for the high He trapping efficiency is the low electron density in the empty regions of the oxide-like structure of the clusters. Vacancy and SIA interaction with the clusters is also attractive. The binding energy of a vacancy strongly depends on the site where the vacancy is inserted while in all the studied cases the SIA is annihilated at the cluster-iron interface. Present results clearly demonstrate that the oxide-based nanoclusters are strong traps for irradiation-induced defects, which is in agreement with experimental findings.

We numerically investigate crystalline order on negative Gaussian curvature capillary bridges. In agreement with the experimental results in [W. Irvine et al., Nature, Pleats in crystals on curved surfaces, 2010, 468, 947] we observe for decreasing integrated Gaussian curvature, a sequence of transitions, from no defects to isolated dislocations, pleats, scars and isolated sevenfold disclinations. We especially focus on the dependency of topological charge on the integrated Gaussian curvature, for which we observe, again in agreement with the experimental results, no net disclination for an integrated curvature down to −10, and an approximately linear behavior from there on until the disclinations match the integrated curvature of −12. In contrast to previous studies in which ground states for each geometry are searched for, we here show that the experimental results, which are likely to be in a metastable state, can be best resembled by mimicking the experimental settings and continuously changing the geometry. The obtained configurations are only low energy local minima. The results are computed using a phase field crystal approach on catenoid-like surfaces and are highly sensitive to the initialization.

Graphite is the strongest diamagnet of all known materials to date. Recent studies of the thickness dependence of the resistance of graphite have demonstrated the heterogeneity of the charge distribution in bulk graphite and prompted the study of its magnetic properties. The studies of the thickness dependence of the magnetic susceptibility of graphite, done in this work, showed that two-dimensional interfaces between the crystalline (Bernal or rhombohedral stacking order) blocks in graphite make a dominant contribution to its diamagnetic susceptibility. Previously proposed models of diamagnetism in graphite are not suitable for explaining its magnetic properties, and therefore new concepts should be considered. Additionally, the studies of the transport and magnetic properties of graphite and multilayer graphene indicated the existence of superconductivity at the interfaces in well-ordered graphite. The possibility of creating permanent circulating currents around artificial holes in highly oriented graphite was studied by highly sensitive magnetization measurements. The obtained results provide hints for the possible existence of superconducting regions inside the bulk highly ordered graphite. In the present thesis, a further thickness dependent phenomenon on the depinning line (DL) of the flux line lattice of the high-Tc superconductor Bi2Sr2CaCu2O8+δ was studied. This geometrical effect shifts to notably lower temperatures in micrometer ring, compared with bulk crystals and thin flakes. The shift is related to a decrease in the overall pinning potential as a result of size effects, caused by: a) the thickness of the sample being smaller than the pinning correlation length, and b) the increase in the effective London penetration depth of the vortices (Pearl vortices). The large shift of the DL to lower temperatures may significantly influence the suitability of such elements for device applications in microstrip antennas and THz emitters.

Die vorliegende Dissertation untersuchte die Kombination von DNA-Nanostrukturen, so- genannte DNA-Origami-Strukturen, mit Layer-by-Layer (LbL) Mikrotransportern zum Auf- bau eines verbesserten Medikamententrägersystems. Dies sollte die jeweiligen Vorteile der eigenständigen Systeme kombinieren um individuelle Nachteile, wie etwa die li- mitierte Stabilität der DNA-Origami-Strukturen unter physiologischen Bedingungen als auch die schrittweise Freisetzung transportierter Medikamente aus der durchlässigen Polymerschicht der LbL-Mikrotransporter, zu umgehen. Die Untersuchungen bestrebten somit die Oberflächenfunktionalisierung der LbL-Mikrotransporter, um den gerichteten Transport in spezifische Zielzellen zu ermöglichen. Im Weiteren sollte die simultane Aus- schüttung des Medikamentes durch geschützte, in die Polymerschicht integrierte, schalt- bare DNA-Origami-Strukturen erreicht werden. Dahingehend wurde zunächst die Verkapselung des Rinderserumproteins und Strept- avidins mittels eines angehangenen DNA-Stranges gezeigt. Dieser hybridisierte an die Komplementärsequenz im Inneren von DNA-Origami-Röhren und geschlossenen Käfi- gen mit rechteckigem Grundriss. Um die für den späteren Medikamententransport not- wendige Ablösung des Proteins aus der Struktur zu untersuchen, wurde das gebundene Protein durch externe Zugabe eines invasiven Stranges und einem einzelsträngigen Über- hang am Bindungsstrang nach der Technik des toehold-mediated strand displacements, dem Überhang-bedingten Strangaustausch, vom Bindungsstrang abgelöst. Die umfassende Un- tersuchung zeigte, dass die Wände geschlossener DNA-Origami-Käfige sowohl für einzel- strängige DNA als auch für Proteine teilweise permeabel waren. Im Gegensatz zu unge- schützten Strukturen, zeigten die in die LbL-Polymerschicht integrierten DNA-Origami- Strukturen in anschließenden Stabilitätsstudien eine deutliche Resistenz gegenüber phys- iologisch degradierenden Faktoren. Zum Ziel des Medikamententransports wurden die hybriden Transporter daraufhin umfassend im Zusammenspiel mit kultivierten Zellen untersucht, wobei sich eine gute Interaktionsrate bei vernachlässigbarer Toxizität des Sys- tems zeigte. Die weitere Verbesserung der biologischen Kompatibilität und Selektivität der Transporter wurde im letzten Schritt durch Oberflächenfunktionalisierung mittels einer Lipiddoppelschicht erreicht. Die zusätzliche Anbindung spezifischer Antikörper an diese Doppelschicht führte anschließend zu einer Verbesserung der Aufnahmerate bei Expres- sion des entsprechenden Rezeptors an der Zelloberfläche. Diese Arbeit zeigte somit die grundlegende Charakterisierung des hybriden Transport- systems aus DNA-Origami-Strukturen und LbL-Mikrotransportern, sowie dessen weitere Funktionalisierung und bildet daher die Grundlage für weiterführende Studien.

The presented thesis explores the magnetoelectric (ME) coupling in multiferroic thin film multilayers of BaTiO3 (BTO) and BiFeO3 (BFO). Multiferroics possess more than one ferroic order parameter, in this case ferroelectricity and anti-ferromagnetism. Cross-coupling between these otherwise separate order parameters promises great advantages in the fields of multistate memory, spintronics and even medical applications. The first major challenge in this field of study is the rarity of multiferroics. Second, most known multiferroics, both intrinsic and extrinsic in nature, possess very low ME coupling coefficients. In previous studies conducted by our group, BTO-BFO multilayers deposited by pulsed laser deposition (PLD) showed a ME coupling coefficient αME enhanced by one order of magnitude, when compared to single-layers of the intrinsic multiferroic BFO. However, the mechanism of ME coupling in such heterostructures is poorly understood until now. In this thesis, we used a selection of structural, chemical, electrical and magnetic measurements to maximize the αME-coefficient and shed light on the origin of this enhanced ME effect. The comparison of BTO-BFO multilayers over single-layers revealed not only enhanced ME-coupling, but also reduced mosaicity, roughness and leakage current density in multilayers. Following a parametric sample optimization, we achieved an atomically smooth interface roughness and vast improvements in the ferroelectric properties by introducing a shadow mask in the PLD process. We measured the highest αME-value so far of 480 Vcm-1Oe-1 for a multilayer with a double-layer thickness of only 4.6 nm, two orders of magnitude larger than the coefficient of 4 Vcm-1Oe-1 measured for BFO single-layers. The αME-coefficient in these multilayers stands in an inverse correlation with the double-layer thickness ddl. The influence of oxygen pressure during growth and BTO-BFO ratio on αME was shown to be neglible in comparison to that of ddl. From the characteristic dependencies of αME on magnetic bias field, temperature and ddl, we concluded the existence of an interface-driven coupling mechanism in BTO-BFO multilayers.:1 Introduction 2 Theory of Multiferroic Magnetoelectrics 2.1 Primary Ferroic Properties 2.2 Magnetoelectric Coupling 3 Materials 3.1 The General Structure of Perovskites ABX3 3.2 Strontium Titanate SrTiO3 3.3 Barium Titanate BaTiO3 3.4 Bismuth Ferrite BiFeO3 3.5 Heterostructures Based on BiFeO3 4 Experimental Section 4.1 Thin Film Fabrication 4.2 X–Ray Diffraction 4.3 Microscopic Techniques 4.4 Chemical Analysis Techniques 4.5 Ferroelectric Characterization 4.6 Magnetic Property Measurements 4.7 Measurement of the Magnetoelectric Coupling Coefficient 5 BaTiO3–BiFeO3 Heterostructures 5.1 General Properties of Single-Layers and Multilayers of BTO and BFO 5.2 PLD–Growth of BaTiO3–BiFeO3 Multilayers 5.3 Manipulation of Multilayer Properties through Design 5.4 Effectiveness of Eclipse–PLD 5.5 Enhanced ME Effect in BaTiO3–BiFeO3 Multilayers 6 Summary and Outlook A Magnetoelectric Measurement Setup B Magnetic Background Measurements C Polarized Neutron Reflectometry Literature Own and Contributed Work Acknowledgement Erratum

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This cumulative dissertation is a compilation of eight peer-reviewed, published scientific papers on the subject of two microscopic techniques of diffusion measurement, namely infrared (IR) microimaging and pulsed field gradient (PFG) NMR. The dissertation contains mainly five chapters. The first chapter introduces diffusion phenomena in general and concisely explains the importance and the current challenges of the investigation of molecular diffusion in nanoporous materials, which are the primary motivations behind the present work. To rise the challenges, it proposes an option of employing IR microimaging in parallel with PFG NMR in the measurement of the molecular diffusion. The second chapter describes the basic principles of the two diffusion measurement techniques and what they are capable of. Chapters 3 and 4 deliver convincing demonstrations of their applicability and potential in diffusion studies. Lastly, Chapter 5 concludes the present work by discussing complementary benefits of the two techniques, along with the novel application of the two-region model for assessing mass transfer in hierarchically porous materials.:Table of Contents CHAPTER 1. Introduction CHAPTER 2. Basics of diffusion measurement techniques 2.1. Introduction to infrared microscopy (IRM) 2.1.1. Working principle 2.1.2. Experimental setup 2.2. Introduction to pulsed field gradient nuclear magnetic resonance (PFG NMR) 2.2.1. Self-diffusion and propagator 2.2.2. Theory of PFG NMR CHAPTER 3. Applicability and potential of IRM • Publication 3.1. Anomaly in the chain length dependence of n-alkane diffusion in ZIF 4 metal-organic frameworks • Publication 3.2. Metal-organic framework Co-MOF-74-based host-guest composites for resistive gas sensing • Publication 3.3. Revealing the transient concentration of CO2 in a mixed-matrix membrane by IR microimaging and molecular modeling • Publication 3.4. IR microimaging of direction-dependent uptake in MFI-type crystals CHAPTER 4. Importance of PFG NMR in diffusion studies • Publication 4.1. NMR diffusometry with guest molecules in nanoporous materials • Publication 4.2. Structural characterisation of hierarchically porous silica monolith by NMR cryo-porometry and -diffusometry CHAPTER 5. Complementary benefits of IR microimaging and PFG NMR • Publication 5.1. Diffusion in nanopores: correlating experimental findings with 'first-principles' predictions • Publication 5.2. Diffusion analysis in pore hierarchies by the two-region model Bibliography Appendix A. Supporting information Appendix B. Author contributions

Jamming' ist ein faszinierender, nicht vollständig verstandener Prozess in der Physik der weichen Materie. Zelluläres Jamming' tritt auch in biologischem Gewebe auf und muss sich im Fall von Krebszellen im Tumorgewebe aufgrund der dichten Packung der Zellen über der dichtesten Kugelpackung anders verhalten als die bekannten 'Jamming' Systeme. In meiner Dissertation skizziere ich wesentliche Ergebnisse zum Verständnis dieses neuen physikalischen Phänomens. Meine Erkenntnisse tragen dazu bei die Dichotomie zwischen den Theorien der dichteinduzierten und der forminduzierten 'Zelljamming' aufzulösen. Die gewonnenen Erkenntnisse weisen auf die Möglichkeit hin Krebszellformen und deren Zellkernformen als Tumormarker für die Metastasierung zu verwenden. Ich fand ein kritisches Skalierungsverhalten für die Dynamik der Neuanordnung von Zellen in der Nähe des Jamming-Übergangs, abhängig von der Zellform der Nachbarschaft. Dies ist der bisher stärkste Beweis dafür, dass die Zellformen als Kontrollparameter für das 'Zelljamming' fungieren können. Die Zellanzahldichte beeinflusst ebenfalls das 'Jamming', ihr Einfluss kann jedoch als eine Verlangsamung der Eigengeschwindigkeit der Zellen beschrieben werden. Eine hohe Zellanzahldichte allein würde also nur die Viskosität des Gewebes erhöhen und es nicht verfestigen. Darüber hinaus habe ich gezeigt, dass es in dicht gepackten dreidimensionalen Zellsphäroiden sowie in Primärtumorstücken einen mit der Zellform verbundenen 'Jamming'-Übergang gibt. Ich verbinde das 'Unjamming' von Zellen mit dem Fortschreiten des Krebses, indem ich zeigte, dass die Herunterregulierung des Adhäsionsmoleküls E-Cadherin, die ein typischer Schritt während der Krebentwicklung ist, einen 'Unjamming'-Übergang verursacht. Bei diesem 'Unjamming'-Übergang kommt es zu einem ausgeprägten Verlust der Kohäsion und einem reduzierten Volumenanteil der Zellen, was zeigt, dass das 'Zelljamming' einen hohen Volumenanteil erfordert.