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- ItemProbing Oxide Reduction and Phase Transformations at the Au-TiO2 Interface by Vibrational Spectroscopy(Bussum : Baltzer, 2017-8-17) Pougin, Anna; Lüken, Alexander; Klinkhammer, Christina; Hiltrop, Dennis; Kauer, Max; Tölle, Katharina; Havenith-Newen, Martina; Morgenstern, Karina; Grünert, Wolfgang; Muhler, Martin; Strunk, JenniferBy a combination of FT-NIR Raman spectroscopy, infrared spectroscopy of CO adsorption under ultrahigh vacuum conditions (UHV-IR) and Raman spectroscopy in the line scanning mode the formation of a reduced titania phase in a commercial Au/TiO2 catalyst and in freshly prepared Au/anatase catalysts was detected. The reduced phase, formed at the Au-TiO2 interface, can serve as nucleation point for the formation of stoichiometric rutile. TinO2n−1 Magnéli phases, structurally resembling the rutile phase, might be involved in this process. The formation of the reduced phase and the rutilization process is clearly linked to the presence of gold nanoparticles and it does not proceed under similar conditions with the pure titania sample. Phase transformations might be both thermally or light induced, however, the colloidal deposition synthesis of the Au/TiO2 catalysts is clearly ruled out as cause for the formation of the reduced phase.
- ItemNew Source of 3D Chitin Scaffolds: The Red Sea Demosponge Pseudoceratina arabica (Pseudoceratinidae, Verongiida)(Basel : MDPI, 2019) Shaala, Lamiaa A.; Asfour, Hani Z.; Youssef, Diaa T.A.; Żółtowska-Aksamitowska, Sonia; Wysokowski, Marcin; Tsurkan, Mikhail; Galli, Roberta; Meissner, Heike; Petrenko, Iaroslav; Tabachnick, Konstantin; Ivanenko, Viatcheslav N.; Bechmann, Nicole; Muzychka, Lyubov V.; Smolii, Oleg B.; Martinović, Rajko; Joseph, Yvonne; Jesionowski, Teofil; Ehrlich, HermannThe bioactive bromotyrosine-derived alkaloids and unique morphologically-defined fibrous skeleton of chitin origin have been found recently in marine demosponges of the order Verongiida. The sophisticated three-dimensional (3D) structure of skeletal chitinous scaffolds supported their use in biomedicine, tissue engineering as well as in diverse modern technologies. The goal of this study was the screening of new species of the order Verongiida to find another renewable source of naturally prefabricated 3D chitinous scaffolds. Special attention was paid to demosponge species, which could be farmed on large scale using marine aquaculture methods. In this study, the demosponge Pseudoceratina arabica collected in the coastal waters of the Egyptian Red Sea was examined as a potential source of chitin for the first time. Various bioanalytical tools including scanning electron microscopy (SEM), fluorescence microscopy, FTIR analysis, Calcofluor white staining, electrospray ionization mass spectrometry (ESI-MS), as well as a chitinase digestion assay were successfully used to confirm the discovery of a-chitin within the skeleton of P. arabica. The current finding should make an important contribution to the field of application of this verongiid sponge as a novel renewable source of biologically-active metabolites and chitin, which are important for development of the blue biotechnology especially in marine oriented biomedicine. © 2019 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
- ItemMicro-/nanostructured alumina as model surface to study topography effects on cell-surface interactions(Saarbrücke : Leibniz-Institut für Neue Materialien, 2011) Aktas, Cenk; Martinez Miró, Martina; Lee, Juseok; Brück, Stefan; Veith, Michael[no abstract available]
- ItemIndependent Geometrical Control of Spin and Charge Resistances in Curved Spintronics(Washington, DC : ACS Publ., 2019) Das, Kumar Sourav; Makarov, Denys; Gentile, Paola; Cuoco, Mario; Van Wees, Bart J.; Ortix, Carmine; Vera-Marun, Ivan J.Spintronic devices operating with pure spin currents represent a new paradigm in nanoelectronics, with a higher energy efficiency and lower dissipation as compared to charge currents. This technology, however, will be viable only if the amount of spin current diffusing in a nanochannel can be tuned on demand while guaranteeing electrical compatibility with other device elements, to which it should be integrated in high-density three-dimensional architectures. Here, we address these two crucial milestones and demonstrate that pure spin currents can effectively propagate in metallic nanochannels with a three-dimensional curved geometry. Remarkably, the geometric design of the nanochannels can be used to reach an independent tuning of spin transport and charge transport characteristics. These results laid the foundation for the design of efficient pure spin current-based electronics, which can be integrated in complex three-dimensional architectures. © 2019 American Chemical Society.
- ItemEngineering new limits to magnetostriction through metastability in iron-gallium alloys([London] : Nature Publishing Group UK, 2021) Meisenheimer, P.B.; Steinhardt, R.A.; Sung, S.H.; Williams, L.D.; Zhuang, S.; Nowakowski, M.E.; Novakov, S.; Torunbalci, M.M.; Prasad, B.; Zollner, C. J.; Wang, Z.; Dawley, N.M.; Schubert, J.; Hunter, A.H.; Manipatruni, S.; Nikonov, D.E.; Young, I.A.; Chen, L.Q.; Bokor, J.; Bhave, S.A.; Ramesh, R.; Hu, J.-M.; Kioupakis, E.; Hovden, R.; Schlom, D.G.; Heron, J.T.Magnetostrictive materials transduce magnetic and mechanical energies and when combined with piezoelectric elements, evoke magnetoelectric transduction for high-sensitivity magnetic field sensors and energy-efficient beyond-CMOS technologies. The dearth of ductile, rare-earth-free materials with high magnetostrictive coefficients motivates the discovery of superior materials. Fe1−xGax alloys are amongst the highest performing rare-earth-free magnetostrictive materials; however, magnetostriction becomes sharply suppressed beyond x = 19% due to the formation of a parasitic ordered intermetallic phase. Here, we harness epitaxy to extend the stability of the BCC Fe1−xGax alloy to gallium compositions as high as x = 30% and in so doing dramatically boost the magnetostriction by as much as 10x relative to the bulk and 2x larger than canonical rare-earth based magnetostrictors. A Fe1−xGax − [Pb(Mg1/3Nb2/3)O3]0.7−[PbTiO3]0.3 (PMN-PT) composite magnetoelectric shows robust 90° electrical switching of magnetic anisotropy and a converse magnetoelectric coefficient of 2.0 × 10−5 s m−1. When optimally scaled, this high coefficient implies stable switching at ~80 aJ per bit.
- ItemDiffusive Motion of Linear Microgel Assemblies in Solution(Basel : MDPI, 2016) Schürings, Marco-Philipp; Nevskyi, Oleksii; Eliasch, Kamill; Michel, Ann-Katrin; Liu, Bing; Pich, Andrij; Böker, Alexander; Von Plessen, Gero; Wöll, DominikDue to the ability of microgels to rapidly contract and expand in response to external stimuli, assemblies of interconnected microgels are promising for actuation applications, e.g., as contracting fibers for artificial muscles. Among the properties determining the suitability of microgel assemblies for actuation are mechanical parameters such as bending stiffness and mobility. Here, we study the properties of linear, one-dimensional chains of poly(N-vinylcaprolactam) microgels dispersed in water. They were fabricated by utilizing wrinkled surfaces as templates and UV-cross-linking the microgels. We image the shapes of the chains on surfaces and in solution using atomic force microscopy (AFM) and fluorescence microscopy, respectively. In solution, the chains are observed to execute translational and rotational diffusive motions. Evaluation of the motions yields translational and rotational diffusion coefficients and, from the translational diffusion coefficient, the chain mobility. The microgel chains show no perceptible bending, which yields a lower limit on their bending stiffness
- ItemA Mechanistic Perspective on Plastically Flexible Coordination Polymers(Weinheim : Wiley-VCH, 2019) Bhattacharya, Biswajit; Michalchuk, Adam A.L.; Silbernagl, Dorothee; Rautenberg, Max; Schmid, Thomas; Feiler, Torvid; Reimann, Klaus; Ghalgaoui, Ahmed; Sturm, Heinz; Paulus, Beate; Emmerling, FranziskaMechanical flexibility in single crystals of covalently bound materials is a fascinating and poorly understood phenomenon. We present here the first example of a plastically flexible one-dimensional (1D) coordination polymer. The compound [Zn(μ-Cl)2(3,5-dichloropyridine)2]n is flexible over two crystallographic faces. Remarkably, the single crystal remains intact when bent to 180°. A combination of microscopy, diffraction, and spectroscopic studies have been used to probe the structural response of the crystal lattice to mechanical bending. Deformation of the covalent polymer chains does not appear to be responsible for the observed macroscopic bending. Instead, our results suggest that mechanical bending occurs by displacement of the coordination polymer chains. Based on experimental and theoretical evidence, we propose a new model for mechanical flexibility in 1D coordination polymers. Moreover, our calculations propose a cause of the different mechanical properties of this compound and a structurally similar elastic material. © 2019 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.
- ItemElectron-to Hole Transport Change Induced by Solvent Vapor Annealing of Naphthalene Diimide Doped with Poly(3-Hexylthiophene)(Lausanne : Frontiers Media, 2021) Janus, Krzysztof; Danielewicz, Kinga; Chlebosz, Dorota; Goldeman, Waldemar; Kiersnowski, AdamHerein we report on fabrication and properties of organic field-effect transistors (OFETs) based on the spray-coated films of N,N′-dioctyl naphthalene diimide (NDIC8) doped with 2.4 wt% of poly (3-hexylthiophene) (P3HT). OFETs with the untreated NDIC8:P3HT films revealed electron conductivity [μe* = 5 × 10–4 cm2×(Vs)−1]. After the annealing in chloroform vapor the NDIC8:P3HT films revealed the hole transport only [μh* = 0.9 × 10–4 cm2×(Vs)−1]. Due to the chemical nature and energy levels, the hole transport was not expected for NDIC8-based system. Polarized optical- and scanning electron microscopies indicated that the solvent vapor annealing of the NDIC8:P3HT films caused a transition of their fine-grained morphology to the network of branched, dendritic crystallites. Grazing incidence wide-angle X-ray scattering studies indicated that the above transition was accompanied by a change in the crystal structure of NDIC8. The isotropic crystal structure of NDIC8 in the untreated film was identical to the known crystal structure of the bulk NDIC8. After the solvent annealing the crystal structure of NDIC8 changed to a not-yet-reported polymorph, that, unlike in the untreated film, was partially oriented with respect to the OFET substrate.
- ItemMembrane Functionalization in Pilot Scale: Roll‐to‐Roll Electron Beam System with Inline Contact Angle Determination(Weinheim : Wiley-VCH, 2021) Schulze, Agnes; Drößler, Lutz; Weiß, Steffen; Went, Marco; Abdul Latif, Amira; Breite, Daniel; Fischer, KristinaTo increase the permeation performance and antifouling properties of polymer membranes, a one-step reaction using electron irradiation was developed. This process combines the surface activation of the membrane polymer and the simultaneous permanent immobilization of hydrophilic molecules. This technology can be applied to various polymers, flat sheet/hollow fiber membranes and all pore ranges. The roll-to-roll system developed for this enables all process steps including inline analysis for quality control of the membrane surface in a continuously operated system. © 2021 The Authors. Chemie Ingenieur Technik published by Wiley-VCH GmbH
- ItemNonspherical Nanoparticle Shape Stability Is Affected by Complex Manufacturing Aspects: Its Implications for Drug Delivery and Targeting(Weinheim : Wiley-VCH, 2019) Haryadi, Bernard Manuel; Hafner, Daniel; Amin, Ihsan; Schubel, Rene; Jordan, Rainer; Winter, Gerhard; Engert, JuliaThe shape of nanoparticles is known recently as an important design parameter influencing considerably the fate of nanoparticles with and in biological systems. Several manufacturing techniques to generate nonspherical nanoparticles as well as studies on in vitro and in vivo effects thereof have been described. However, nonspherical nanoparticle shape stability in physiological-related conditions and the impact of formulation parameters on nonspherical nanoparticle resistance still need to be investigated. To address these issues, different nanoparticle fabrication methods using biodegradable polymers are explored to produce nonspherical nanoparticles via the prevailing film-stretching method. In addition, systematic comparisons to other nanoparticle systems prepared by different manufacturing techniques and less biodegradable materials (but still commonly utilized for drug delivery and targeting) are conducted. The study evinces that the strong interplay from multiple nanoparticle properties (i.e., internal structure, Young's modulus, surface roughness, liquefaction temperature [glass transition (Tg) or melting (Tm)], porosity, and surface hydrophobicity) is present. It is not possible to predict the nonsphericity longevity by merely one or two factor(s). The most influential features in preserving the nonsphericity of nanoparticles are existence of internal structure and low surface hydrophobicity (i.e., surface-free energy (SFE) > ≈55 mN m−1, material–water interfacial tension <6 mN m−1), especially if the nanoparticles are soft (<1 GPa), rough (Rrms > 10 nm), porous (>1 m2 g−1), and in possession of low bulk liquefaction temperature (<100 °C). Interestingly, low surface hydrophobicity of nanoparticles can be obtained indirectly by the significant presence of residual stabilizers. Therefore, it is strongly suggested that nonsphericity of particle systems is highly dependent on surface chemistry but cannot be appraised separately from other factors. These results and reviews allot valuable guidelines for the design and manufacturing of nonspherical nanoparticles having adequate shape stability, thereby appropriate with their usage purposes. Furthermore, they can assist in understanding and explaining the possible mechanisms of nonspherical nanoparticles effectivity loss and distinctive material behavior at the nanoscale. © 2019 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim