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Hybrid Dielectric Films of Inkjet-Printable Core-Shell Nanoparticles
2021, Buchheit, Roman, Kuttich, Björn, González-García, Lola, Kraus, Tobias
A new type of hybrid core-shell nanoparticle dielectric that is suitable for inkjet printing is introduced. Gold cores (dcore ≈ 4.5 nm diameter) are covalently grafted with thiol-terminated polystyrene (Mn = 11000 Da and Mn = 5000 Da) and used as inks to spin-coat and inkjet-print dielectric films. The dielectric layers have metal volume fractions of 5 to 21 vol% with either random or face-centered-cubic structures depending on the polymer length and grafting density. Films with 21 vol% metal have dielectric constants of 50@1 Hz. Structural and electrical characterization using transmission electron microscopy, small-angle X-ray scattering, and impedance spectroscopy indicates that classical random capacitor-resistor network models partially describe this hybrid material but fail at high metal fractions, where the covalently attached shell prevents percolation and ensures high dielectric constants without the risk of dielectric breakdown. A comparison of disordered to ordered films indicates that the network structure affects dielectric properties less than the metal content. The applicability of the new dielectric material is demonstrated by formulating inkjet inks and printing devices. An inkjet-printed capacitor with an area of 0.79 mm2 and a 17 nm thick dielectric had a capacitance of 2.2±0.1 nF@1 kHz .
Colloidal Analysis of Particles Extracted from Microalloyed Steels
2021, Hegetschweiler, Andreas, Jochem, Aljosha-Rakim, Zimmermann, Anna, Walter, Johannes, Staudt, Thorsten, Kraus, Tobias
Different colloidal particle characterization methods are examined for their suitability to determine the particle size distribution of particles extracted from steels. Microalloyed steels are dissolved to extract niobium and titanium carbonitride particles that are important for the mechanical properties of these steels. Such particles have sizes ranging from several nanometers to hundreds of nanometers depending on the precipitation stage during the thermomechanically controlled rolling process. The size distribution of the particles is analyzed by dynamic light scattering (DLS), analytical ultracentrifugation (AUC), and hollow fiber flow field-flow fractionation (HF5) and compared to data obtained for reference particles as well as data from electron microscopy, the standard sizing technique used in metallurgy today. AUC and HF5 provide high-quality size distributions, average over large particle numbers that enables statistical analysis, and yield useful insights for alloy design; however, DLS fails due to a lack of resolution. Important aspects in the conversion and comparison of size distributions obtained for broadly distributed particle systems with different measurement principles and the role of surfactants used in sample preparation are discussed.
3D Printed Tubular Scaffolds with Massively Tailorable Mechanical Behavior
2022, Pickering, Edmund, Paxton, Naomi C., Bo, Arixin, O’Connell, Bridget, King, Mitchell, Woodruff, Maria A.
Melt electrowriting (MEW) is a promising additive manufacturing technique for tissue scaffold biofabrication. Successful application of MEW scaffolds requires strictly controlled mechanical behavior. This requires scaffold geometry be optimized to match native tissue properties while simultaneously supporting cell attachment and proliferation. The objective of this work is to investigate how geometric properties can be exploited to massively tailor the mechanical behavior of tubular crosshatch scaffolds. An experimentally validated finite element (FE) model is developed and 441 scaffold geometries are investigated under tension, compression, bending, and radial loading. A range of pore areas (4–150 mm2) and pore angles (11°–134°) are investigated. It is found that scaffold mechanical behavior is massively tunable through the control of these simple geometric parameters. Across the ranges investigated, scaffold stiffness varies by a factor of 294× for tension, 204× for compression, 231× for bending, and 124× for radial loading. Further, it is discussed how these geometric parameters can be simultaneously tuned for different biomimetic material applications. This work provides critical insights into scaffold design to achieve biomimetic mechanical behavior and provides an important tool in the development of biomimetic tissue engineered constructs.
A Highly Active Cobalt Catalyst for the General and Selective Hydrogenation of Aromatic Heterocycles
2023, Bauer, Christof, Müller, Felix, Keskin, Sercan, Zobel, Mirijam, Kempe, Rhett
Nanostructured earth abundant metal catalysts that mediate important chemical reactions with high efficiency and selectivity are of great interest. This study introduces a synthesis protocol for nanostructured earth abundant metal catalysts. Three components, an inexpensive metal precursor, an easy to synthesize N/C precursor, and a porous support material undergo pyrolysis to give the catalyst material in a simple, single synthesis step. By applying this catalyst synthesis, a highly active cobalt catalyst for the general and selective hydrogenation of aromatic heterocycles could be generated. The reaction is important with regard to organic synthesis and hydrogen storage. The mild reaction conditions observed for quinolines permit the selective hydrogenation of numerous classes of N-, O- and S-heterocyclic compounds such as: quinoxalines, pyridines, pyrroles, indoles, isoquinoline, aciridine amine, phenanthroline, benzofuranes, and benzothiophenes.
Nanoscale Faceting and Ligand Shell Structure Dominate the Self-Assembly of Nonpolar Nanoparticles into Superlattices
2022, Bo, Arixin, Liu, Yawei, Kuttich, Björn, Kraus, Tobias, Widmer-Cooper, Asaph, de Jonge, Niels
Self-assembly of nanoscale structures at liquid–solid interfaces occurs in a broad range of industrial processes and is found in various phenomena in nature. Conventional theory assumes spherical particles and homogeneous surfaces, but that model is oversimplified, and nanoscale in situ observations are needed for a more complete understanding. Liquid-phase scanning transmission electron microscopy (LP-STEM) is used to examine the interactions that direct the self-assembly of superlattices formed by gold nanoparticles (AuNPs) in nonpolar liquids. Varying the molecular coating of the substrate modulates short-range attraction and leads to switching between a range of different geometric structures, including hexagonal close-packed (hcp), simple hexagonal (sh), dodecahedral quasi-crystal (dqc), and body-centered cubic (bcc) lattices, as well as random distributions. Langevin dynamics simulations explain the experimental results in terms of the interplay between nanoparticle faceting, ligand shell structure, and substrate–NP interactions.
Synthesis of 3,4-Dihydro-2H-Pyrroles from Ketones, Aldehydes, and Nitro Alkanes via Hydrogenative Cyclization
2022, Klausfelder, Barbara, Blach, Patricia, de Jonge, Niels, Kempe, Rhett
Syntheses of N-heterocyclic compounds that permit a flexible introduction of various substitution patterns by using inexpensive and diversely available starting materials are highly desirable. Easy to handle and reusable catalysts based on earth-abundant metals are especially attractive for these syntheses. We report here on the synthesis of 3,4-dihydro-2H-pyrroles via the hydrogenation and cyclization of nitro ketones. The latter are easily accessible from three components: a ketone, an aldehyde and a nitroalkane. Our reaction has a broad scope and 23 of the 33 products synthesized are compounds which have not yet been reported. The key to the general hydrogenation/cyclization reaction is a highly active, selective and reusable nickel catalyst, which was identified from a library of 24 earth-abundant metal catalysts.
Silicon-Nanotube-Mediated Intracellular Delivery Enables Ex Vivo Gene Editing
2020, Chen, Yaping, Aslanoglou, Stella, Murayama, Takahide, Gervinskas, Gediminas, Fitzgerald, Laura I., Sriram, Sharath, Tian, Jie, Johnston, Angus P.R., Morikawa, Yasuhiro, Suu, Koukou, Elnathan, Roey, Voelcker, Nicolas H.
Engineered nano–bio cellular interfaces driven by vertical nanostructured materials are set to spur transformative progress in modulating cellular processes and interrogations. In particular, the intracellular delivery—a core concept in fundamental and translational biomedical research—holds great promise for developing novel cell therapies based on gene modification. This study demonstrates the development of a mechanotransfection platform comprising vertically aligned silicon nanotube (VA-SiNT) arrays for ex vivo gene editing. The internal hollow structure of SiNTs allows effective loading of various biomolecule cargoes; and SiNTs mediate delivery of those cargoes into GPE86 mouse embryonic fibroblasts without compromising their viability. Focused ion beam scanning electron microscopy (FIB-SEM) and confocal microscopy results demonstrate localized membrane invaginations and accumulation of caveolin-1 at the cell–NT interface, suggesting the presence of endocytic pits. Small-molecule inhibition of endocytosis suggests that active endocytic process plays a role in the intracellular delivery of cargo from SiNTs. SiNT-mediated siRNA intracellular delivery shows the capacity to reduce expression levels of F-actin binding protein (Triobp) and alter the cellular morphology of GPE86. Finally, the successful delivery of Cas9 ribonucleoprotein (RNP) to specifically target mouse Hprt gene is achieved. This NT-enhanced molecular delivery platform has strong potential to support gene editing technologies. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim