Highlight Publications 2017

Fabrication of defined polydopamine nanostructures by DNA origami-templated polymerization
Yu Tokura, Sean Harvey, Chaojian Chen, Yuzhou Wu, David Y.W. Ng, Tanja Weil
Fabrication of defined polydopamine nanostructures by DNA origami-templated polymerization
A versatile, bottom-up approach allows the controlled fabrication of polydopamine (PD) nanostructures on DNA origami. PD is a biosynthetic polymer that has been investigated as an adhesive and promising surface coating material. DNA origami decorated with multiple horseradish peroxidase-mimicking DNAzyme motifs was used to control the shape and size of PD formation with nanometer resolution. These fabricated PD nanostructures can serve as “supramolecular glue” for controlling DNA origami conformations. Facile liberation of the PD nanostructures from the DNA origami templates has been achieved in acidic medium. This presented DNA origami-controlled polymerization of a highly crosslinked polymer provides a unique access towards anisotropic PD architectures with distinct shapes that were retained even in the absence of the DNA origami template.
© Wiley VCH (2017)
Nanofabrication of Precise Polydopamine Architectures
Directing Intracellular Supramolecular Assembly with N-heteroaromatic Quaterthiophene Analogues
David Y.W. Ng, Roman Vill, Yuzhou Wu, Kaloian Koynov, Yu Tokura, Weina Liu, Susanne Sihler, Andreas Kreyes, Sandra Ritz, Holger Barth, Ulrich Ziener, Tanja Weil
Directing Intracellular Supramolecular Assembly with N-heteroaromatic Quaterthiophene Analogues
Self-assembly in situ, where synthetic molecules are programmed to organize in a complex environment can be a unique strategy to influence cellular functions. Here we present oligothiophene analogues that target, locate and dynamically self-report their supramolecular behavior within the confinement of a cell. Through the recognition of their chemical structure, we show that the cell provides different pathways for self-assembly that are traced with fluorescence microscopy. Their molecular organization emits in distinct fluorescent bands and the control each form is achieved by time, temperature as well as the use of the intracellular transport inhibitor, bafilomycin A1. We show the importance of both intrinsic and extrinsic factors for self-organization and the potential of such a platform toward developing synthetic functional components within living cells.
© David Ng / MPI-P (2017)
Overview of cellular pathways and its influence on self-organization of the oligothiophene analogues
Biological fabrication of cellulose fibers with tailored properties
Filipe Natalio, Regina Fuchs, Sidney R. Cohen, Gregory Leitus, Gerhard Fritz-Popovski, Oskar Paris, Michael Kappl, Hans-Jürgen Butt
Biological fabrication of cellulose fibers with tailored properties
Filipe Natalio from the Weizmann Institute of Science Israel, together with colleagues from the MPI-P and from Leoben, Austria, developed a method for biofabrication of functional cotton. Cotton ovules, were incubated in media containing glucose molecules (the molecular building blocks of cellulose fibers) that were specifically modified. Dye molecules or molecular magnets linked to glucose were taken up by the ovules and metabolized into cellulose fibers that became colored or exhibiting magnetic response. This new concept of material farming opens perspectives for plant based biofabrication of functional materials without genetic modifications.
© Filipe Natalio (2017)
Optical microscopy image of cotton fibers containing a fluorescent dye. Dye molecules were integrated into fibers via the metabolic pathways of cotton ovules, incubating them with specifically designed glucose molecules containing the dye.
Processing of ferroelectric polymers for microelectronics: from morphological analysis to functional devices
Hamed Sharifi, Jasper Michels, Kamal Asadi
Processing of ferroelectric polymers for microelectronics: from morphological analysis to functional devices
Organic memory devices are of great interest for flexible and cost-effective thin-film applications, such as RFID tags. However, a low cost production is only guaranteed if processing occurs under ambient, and therefore “humid”, conditions. It is known that solutions containing the fluorinated polyethylenes used for such applications, demix upon ingress of ambient water vapor into the coated film. This “vapor-induced phase separation” causes porous dry layers, desirable in case of, for instance, membrane technology, but to be avoided in thin-film electronics. Via an amalgamation of morphological mapping, device physics and modeling of demixing dynamics, we demonstrate how the hygroscopicity of the solvent crucially determines dry film morphology. For a sufficiently low solvent hygroscopicity, a >90% yield of functioning memory devices has been obtained at ambient conditions.
© RSC (2017)
A combination of morphological analysis and numerical simulation of solution phase behavior elucidates the relation between ambient humidity, solvent hygroscopicity and thin-film memory device performance.
Thermal conductivity and air-mediated losses in periodic porous silicon membranes at high temperatures
B. Graczykowski, A. El Sachat, J. S. Reparaz, M. Sledzinska, M. R. Wagner, E. Chavez-Angel, Y. Wu, S. Volz, F. Alzina & C. M. Sotomayor Torres
Thermal conductivity and air-mediated losses in periodic porous silicon membranes at high temperatures
Heat conduction in silicon can be effectively engineered by means of sub-micrometre porous free- standing membranes. Tunable thermal properties make these structures good candidates for integrated heat management units. In this work we use the two-laser Raman thermometry to study heat dissipation in periodic porous membranes at high temperatures via lattice conduction and air-mediated losses. We find the reduction of the thermal conductivity and its temperature dependence correlated with the structure feature size. On the basis of two-phonon Raman spectra, we attribute this behaviour to diffuse phonon-boundary scattering. Furthermore, we quantify the heat dissipation via natural air-mediated cooling, which can be tuned by engineering the porosity.
© Bartlomiej Graczykowski / MPI-P (2017)
Schematics of the two-laser Raman thermometry experiment performed on periodic porous Si membarnes.
Direct observation of mode-specific phonon-band gap coupling in methylammonium lead halide perovskites
Heejae Kim, Johannes Hunger, Enrique Cánovas, Melike Karakus, Zoltán Mics, Maksim Grechko, Dmitry Turchinovich, Sapun H. Parekh & Mischa Bonn
Direct observation of mode-specific phonon-band gap coupling in methylammonium lead halide perovskites
Methylammonium lead iodide perovskite is well-known not only for its remarkable rise of the power conversion efficiency in photovoltaic applications, but also for its peculiar photo-physical properties. We have investigated one of the intriguing peculiarities: the positive temperature dependence of the optical band gap. By the time-resolved THz/optical spectroscopy, we were able to observe a blue shift of the absorption onset after ~1 THz vibrational mode was excited. Theoretical modelling approaches assisted us to identify the specific phonon mode from the experimental results. We showed that the particular vibration, which governs the angle between lead and iodide ionic bonds, contributes to the unusual temperature dependent light absorption of this perovskite.
© Heejae Kim / MPI-P (2017)
Figure Caption: Selective excitation of the ~ 1 THz phonon mode, which corresponds to the Pb-I-Pb angle, induces the transient increase of the optical band gap.
 
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