INMdok (Leibniz Institute for New Materials)
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A New Family of Layered Metal-Organic Semiconductors: Cu/V-Organophosphonates
Get PDFHerein, we report the design and synthesis of a layered redox-active, antiferromagnetic metal organic semiconductor crystals with the chemical formula [Cu(H2O)2V(µ-O)(PPA)2] (where PPA is phenylphosphonate). The crystal structure of [Cu(H2O)2V(µ-O)(PPA)2] shows that the metal phosphonate layers are separated by phenyl groups of the phenyl phosphonate linker. Tauc plotting of diffuse reflectance spectra indicates that [Cu(H2O)2V(µ-O)(PPA)2] has an indirect band gap of 2.19 eV. Photoluminescence (PL) spectra indicate a complex landscape of energy states with PL peaks at 1.8 and 2.2 eV. [Cu(H2O)2V(µ-O)(PPA)2] has estimated hybrid ionic and electronic conductivity values between 0.13 and 0.6 S m−1. Temperature-dependent magnetization measurements show that [Cu(H2O)2V(µ-O)(PPA)2] exhibits short range antiferromagnetic order between Cu(II) and V(IV) ions. [Cu(H2O)2V(µ-O)(PPA)2] is also photoluminescent with photoluminescence quantum yield of 0.02%. [Cu(H2O)2V(µ-O)(PPA)2] shows high electrochemical, and thermal stability
Derivatization and design of transition metal oxides and sulfides for advanced and sustainable battery technology
No full textThis Ph.D. thesis focuses on developing electrochemical energy storage devices that outperform existing lithium-ion batteries. The research investigates the design and modification of metal oxides and sulfides to enhance the electrochemical performance of commercial battery electrodes and presents the challenges met. By employing specific design strategies and derivatization methods, novel materials with unique properties are synthesized, distinct from those found in commercial batteries. For each material studied, the thesis examines the relationship between its electrochemical performance and various other material properties to address existing limitations. In the case of self-standing fibers, the influence of mechanical flexibility on electrochemical properties is analyzed. Similarly, for the conversion-type materials, the detrimental shuttling effect or electrode etching is mitigated by applying a stable coating to protect the active component from degradation. In parallel. this thesis aims to use pH-neutral syntheses and low-temperature derivatization to reduce the effect of harsh components and high-energy procedures and presents the challenges that arise from this. Additionally, this work explores complementary approaches to enhance the interface between the electrode and electrolyte after modifying the electrode material through materials engineering. These strategies are thoroughly investigated and presented as potential solutions to improve the overall performance of energy storage devices.Diese Dissertation befasst sich mit der Entwicklung elektrochemischer Energiespeicher, die die Leistung bestehender Lithium-Ionen-Batterien übertreffen. Die Forschung untersucht das Design und die Modifikation von Metalloxiden und -sulfiden, um die elektrochemische Leistung kommerzieller Batterieelektroden zu verbessern, und stellt die damit verbundenen Herausforderungen dar. Durch den Einsatz spezifischer Designstrategien und Derivatisierungsmethoden werden neuartige Materialien mit einzigartigen Eigenschaften synthetisiert, die sich von denen in kommerziellen Batterien unterscheiden. Für jedes untersuchte Material wird die Beziehung zwischen seiner elektrochemischen Leistung und verschiedenen anderen Materialeigenschaften untersucht, um bestehende Einschränkungen zu beseitigen. Im Falle der selbsttragenden Fasern wird der Einfluss der mechanischen Flexibilität auf die elektrochemischen Eigenschaften analysiert. Bei den Konversionsmaterialien wird der nachteilige Shuttling-Effekt oder das Ätzen der Elektroden durch das Aufbringen einer stabilen Beschichtung zum Schutz der aktiven Komponente vor Degradation abgeschwächt. Die Arbeit zielt darauf ab, pH-neutrale Synthesen und Niedertemperatur-Derivatisierung zu verwenden, um die Auswirkungen von aggressiven Komponenten und energiereichen Verfahren zu verringern, und stellt die Herausforderungen dar, die sich daraus ergeben. Darüber hinaus werden in dieser Arbeit ergänzende Ansätze zur Verbesserung der Grenzfläche zwischen Elektrode und Elektrolyt nach Modifizierung des Elektrodenmaterials durch Werkstofftechnik untersucht. Diese Strategien werden eingehend untersucht und als mögliche Lösungen zur Verbesserung der Gesamtleistung der Energiespeicher vorgestellt
Secretion of Vimentin and its influence on cellular functionality
Get PDFThe cytoskeleton is a dynamic network of filaments comprising actin filaments, microtubules, and intermediate filaments in the cytoplasm of cells. Vimentin is an intermediate filament protein that plays a crucial role in adhesion, migration, and signalling. These functions of vimentin have broader implications on inflammation, wound healing, cell physiology, and immune response. Inside the cell, the vimentin network extends from the nucleus to the cell's periphery. However, vimentin gets out to the extracellular environment under the circumstances such as activation, stress, and senescence. However, the influence of such vimentin on general cellular functions and its characteristics is not well established. This thesis demonstrates that extracellular addition of vimentin enhances proliferation, adhesion and migration prominently in cancer cells (MCF-7), overexpressing insulin-like growth factor 1 (IGF1-R). Interestingly, in SARS-CoV-2 infection, the extracellular vimentin preincubation with the SARS-CoV-2 receptor binding domain protected the cancer (MCF-7) cell's monolayer integrity. Further investigation on the characteristics of extracellular vimentin found secretion of vimentin from the back of activated macrophages in the form of small fragments, enhancing phagocytosis and migration of activated macrophages. Collectively, this work demonstrates new insights into vimentin secretion and its implications on cellular functionality.Das Zytoskelett ist ein dynamisches Netz von Filamenten, das aus Aktinfilamenten, Mikrotubuli und Zwischenfilamenten im Zytoplasma von Zellen besteht. Vimentin ist ein Zwischenfilamentprotein, das eine entscheidende Rolle bei Adhäsion, Migration und Signalübertragung spielt. Diese Funktionen von Vimentin haben weitreichende Auswirkungen auf Entzündungen, Wundheilung, Zellphysiologie und Immunreaktion. Innerhalb der Zelle erstreckt sich das Vimentin-Netzwerk vom Zellkern bis zur Peripherie der Zelle. Unter bestimmten Umständen wie Aktivierung, Stress und Seneszenz gelangt Vimentin jedoch auch in die extrazelluläre Umgebung. Der Einfluss dieses Vimentins auf die allgemeinen Zellfunktionen und seine Eigenschaften ist jedoch nicht gut untersucht. Diese Arbeit zeigt, dass die extrazelluläre Zugabe von Vimentin die Proliferation, Adhäsion und Migration in Krebszellen (MCF-7), die den insulinähnlichen Wachstumsfaktor 1 (IGF1-R) überexprimieren, deutlich erhöht. Interessanterweise schützte das extrazelluläre Vimentin bei einer SARS-CoV-2-Infektion vor der Inkubation mit der SARS-CoV-2- Rezeptorbindungsdomäne die Integrität der Krebszellen (MCF-7) in der Monolage. Weitere Untersuchungen zu den Eigenschaften von extrazellulärem Vimentin ergaben, dass Vimentin von der Rückseite aktivierter Makrophagen in Form kleiner Fragmente abgesondert wird, was die Phagozytose und Migration aktivierter Makrophagen fördert. Insgesamt zeigen diese Arbeiten neue Erkenntnisse über die Vimentin-Sekretion und ihre Auswirkungen auf die zelluläre Funktionalit
An E-cadherin-actin clutch translates the mechanical force of cortical flow for cell-cell contact to inhibit epithelial cell locomotion
No full textAdherens junctions (AJs) allow cell contact to inhibit epithelial migration yet also permit epithelia to move as coherent sheets. How, then, do cells identify which contacts will inhibit locomotion? Here, we show that in human epithelial cells this arises from the orientation of cortical flows at AJs. When the leader cells from different migrating sheets make head-on contact with one another, they assemble AJs that couple together oppositely directed cortical flows. This applies a tensile signal to the actin-binding domain (ABD) of α-catenin, which provides a clutch to promote lateral adhesion growth and inhibit the lamellipodial activity necessary for migration. In contrast, AJs found between leader cells in the same migrating sheet have cortical flows aligned in the same direction, and no such mechanical inhibition takes place. Therefore, α-catenin mechanosensitivity in the clutch between E-cadherin and cortical F-actin allows cells to interpret the direction of motion via cortical flows and signal for contact to inhibit locomotion
Influence of structural depth of laser-patterned steel surfaces on the solid lubricity of carbon nanoparticle coatings
Get PDFCarbon nanoparticle coatings on laser-patterned stainless-steel surfaces present a solid lubrication system where the pattern’s recessions act as lubricant-retaining reservoirs. This study investigates the influence of the structural depth of line patterns coated with multi-walled carbon nanotubes (CNTs) and carbon onions (COs) on their respective potential to reduce friction and wear. Direct laser interference patterning (DLIP) with a pulse duration of 12 ps is used to create line patterns with three different structural depths at a periodicity of 3.5 µm on AISI 304 steel platelets. Subsequently, electrophoretic deposition (EPD) is applied to form homogeneous carbon nanoparticle coatings on the patterned platelets. Tribological ball-on-disc experiments are conducted on the as-described surfaces with an alumina counter body at a load of 100 mN. The results show that the shallower the coated structure, the lower its coefficient of friction (COF), regardless of the particle type. Thereby, with a minimum of just below 0.20, CNTs reach lower COF values than COs over most of the testing period. The resulting wear tracks are characterized by scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. During friction testing, the CNTs remain in contact, and the immediate proximity, whereas the CO coating is largely removed. Regardless of structural depth, no oxidation occurs on CNT-coated surfaces, whereas minor oxidation is detected on CO-coated wear tracks
Sacrificial ligand route to hybrid polythiophene-silver nanoparticles for sinter-free conductive inks
Get PDFWe report the synthesis of AgNP@PEDOT:PSS hybrid conductive particles with silver cores and polythiophene shells that can be used to formulate sinter-free inks for printing electronics. First, Ag nanocrystals capped with the weakly bound ligand aminohexanoic acid (ε-Ahx) are prepared. The ligand shell is exchanged by reacting the dispersion with the polymer ionomer mixture poly(3,4-ethylene dioxythiophene):polystyrene sulfonate (PEDOT:PSS). The particles are characterized by electron microscopy, dynamic light scattering, Z potential, and Raman spectroscopy, confirming the replacement of the ligands on the metal particle surface. The resulting dispersion is colloidally stable as confirmed by DLS. Inks with a solid content of the hybrid particles of 300 mg mL−1 were prepared and deposited on different substrates. The new particles are components for hybrid inks that become electrically conductive without any chemical or thermal post-deposition treatment. We show that silver-based hybrid inks can be deposited on different substrates and possess an average conductivity after 24 h of drying at room temperature of 1.726 × 106 S m−1 ± 0.326 × 106 S m−1, only one order of magnitude lower than elemental silver and within the same order of magnitude as their gold ink counterpart
Jamming and flocking in the restricted active Potts model
Get PDFWe study the active Potts model with either site occupancy restriction or on-site repulsion to explore jamming and kinetic arrest in a flocking model. The incorporation of such volume exclusion features leads to a surprisingly rich variety of self-organized spatial patterns. While bands and lanes of moving particles commonly occur without or under weak volume exclusion, strong volume exclusion along with low temperature, high activity, and large particle density facilitates jams due to motility-induced phase separation. Through several phase diagrams, we identify the phase boundaries separating the jammed and free-flowing phases and study the transition between these phases which provide us with both qualitative and quantitative predictions of how jamming might be delayed or dissolved. We further formulate and analyze a hydrodynamic theory for the restricted APM which predicts various features of the microscopic model
Heterogeneous Mean First Passage Time Scaling in Fractal Media
No full textThe mean first passage time~(MFPT) of random walks is a key quantity characterizing dynamic processes on disordered media. In a random fractal embedded in the Euclidean space, the MFPT is known to obey the power law scaling with the distance between a source and a target site with a universal exponent. We find that the scaling law for the MFPT is not determined solely by the distance between a source and a target but also by their locations. The role of a site in the first passage processes is quantified by the random walk centrality. It turns out that the site of highest random walk centrality, dubbed as a hub, intervenes in first passage processes. We show that the MFPT from a departure site to a target site is determined by a competition between direct paths and indirect paths detouring via the hub. Consequently, the MFPT displays a crossover scaling between a short distance regime, where direct paths are dominant, and a long distance regime, where indirect paths are dominant. The two regimes are characterized by power laws with different scaling exponents. The crossover scaling behavior is confirmed by extensive numerical calculations of the MFPTs on the critical percolation cluster in two dimensional square lattices
Is there more than one stickiness criterion?
Get PDFAdhesion between an elastic body and a smooth, rigid substrate can lead to large tensile stresses between them. However, most macroscopic objects are microscopically rough, which strongly suppresses adhesion. A fierce debate has unfolded recently as to whether local or global parameters determine the crossover between small and large adhesion. Here, we report simulations revealing that the dependence of the pull-off force Fn on the surface energy γ does not only have two regimes of high and low adhesion but up to four regimes. They are related to contacts, which at the moment of rupture consist of (i) the last individual Hertzian-shaped contact, in which is linear in γ, (ii) a last meso-scale, individual patches with super-linear scaling, (iii) many isolated contact patches with extremely strong scaling, and (iv) a dominating largest contact patch, for which the pull-off stress is no longer negligible compared to the maximum, microscopic pull-off stress. Regime (iii) can be seen as a transition domain. It is located near the point where the surface energy is half the elastic energy per unit area in conformal contact. A criterion for the transition between regimes (i) and (ii) appears difficult to grasp
Gelation Kinetics and Mechanical Properties of Thiol-Tetrazole Methylsulfone Hydrogels Designed for Cell Encapsulation
Get PDFHydrogel precursors that crosslink within minutes are essential for the development of cell encapsulation matrices and their implementation in automated systems. Such timescales allow sufficient mixing of cells and hydrogel precursors under low shear forces and the achievement of homogeneous networks and cell distributions in the 3D cell culture. The previous work showed that the thiol-tetrazole methylsulfone (TzMS) reaction crosslinks star-poly(ethylene glycol) (PEG) hydrogels within minutes at around physiological pH and can be accelerated or slowed down with small pH changes. The resulting hydrogels are cytocompatible and stable in cell culture conditions. Here, the gelation kinetics and mechanical properties of PEG-based hydrogels formed by thiol-TzMS crosslinking as a function of buffer, crosslinker structure and degree of TzMS functionality are reported. Crosslinkers of different architecture, length and chemical nature (PEG versus peptide) are tested, and degree of TzMS functionality is modified by inclusion of RGD cell-adhesive ligand, all at concentration ranges typically used in cell culture. These studies corroborate that thiol/PEG-4TzMS hydrogels show gelation times and stiffnesses that are suitable for 3D cell encapsulation and tunable through changes in hydrogel composition. The results of this study guide formulation of encapsulating hydrogels for manual and automated 3D cell culture