Sub-micron plastic spheres dispersed in water form excellent models to study crystallization and melting transitions in SlowMo by video-microscopy or other optical methods. In a recent paper, the group of T. Palberg, Institute of Physics, JGU, has investigated the speed with which crystals form in melts of slightly unlike spheres. They find that the nucleation of crystals gets faster with increased undercooling. However, they also observe that nucleation is accelerated by small size-differences. Its speed increases continuously up to about 8% of so-called polydispersity. (Larger differences are not tolerated and nucleation speed is drastically reduced by the necessary sorting processes.) The origin of this counter-intuitive effect is a decreasing crystal melt surface tension. The scientists show that surface tension is intimately coupled to the difference in the degree of disorder between melt and solid (at least for systems with a hard core, like metal atoms or plastic spheres). If the spheres are all slightly different, the order in both melt and crystal are disturbed, but to a much larger degree in the crystal. As a consequence the difference in disorder and the surface tension decrease and nucleation becomes much easier. This may explain, why hard spheres of all equal size crystallize so reluctantly in computer simulations. It may further open an unexpected experimental access route to the long predicted Wigner glass.
More information can be found here (german).
New SFB on Spin Phenomena approved by DFG
At the meeting of the DFG senate, the new collaborative research centre (Sonderforschungsbereicht - SFB) on spin phenomena (Spin+X) was approved. This large scale project unites the 30 leading groups in spintronics and spin - related research from Physics, Chemistry and Engineering at Johannes Gutenberg University Mainz and the TU Kaiserslautern.
The project is initially funded with 12 Mio. Euros for 4 years and can be extended up to 12 years.
More information can be found here (german).
CINEMA supports a joint summer school organized by the Marie Curie Initial Training Network (ITN) "ACRITAS" and the Graduate School of Excellence "Materials Science in Mainz". The workshop was held at the Institute of Physical Chemistry at the Johannes Gutenberg University Mainz. Around forty participants followed exciting lectures and tutorials given by highly renowned scientists from all over the world.
Research structure concept of ELYSION enhances the strategic relevance of Mainz in the fields of electroconversion and electroactive materials.
Over the next four years, the Carl Zeiss Foundation will be providing support in the form of EUR 850,000 to the Advanced Lab for Electrochemistry and Electroorganic Synthesis (ELYSION), a unique collaborative research concept based at the Institute of Organic Chemistry and the Institute of Inorganic Chemistry and Analytical Chemistry at Johannes Gutenberg University Mainz (JGU). The use of electricity as a catalyst in chemical reactions is one of the most sustainable methods of synthesizing materials and chemical compounds. The accompanying development of electrolytic conversion techniques and new types of electrodes will make it possible to overcome the existing frontiers of this future-oriented approach.
More information can be found here.
Graphene-based compact nanohybrid films made by alternate deposition of electrochemically exfoliated graphene and mesoporous graphene-conducting polymer nanosheets are constructed for high-energy micro-supercapacitors. They are shown to have a landmark areal capacitance of 368 mF cm−2 and volumetric capacitance of 736 F cm−3.
Zhong-Shuai Wu, Khaled Parvez, Shuang Li, Sheng Yang, Zhaoyang Liu, Shaohua Liu, Xinliang Feng, Klaus Müllen: Alternating Stacked Graphene-Conducting Polymer Compact Films with Ultrahigh Areal and Volumetric Capacitances for High-Energy Micro-Supercapacitors. Advanced Materials (2015) doi: 10.1002/adma.201501643
A novel bilayer coating system for autonomous corrosion-triggered self-healing is demonstrated. The storage of the encapsulated monomer and the catalyst is separated in two different layers. The encapsulated catalyst is stored inside a metallic coating which ensures its activity even for an extended exposure time. The release from the capsules is triggered by corrosion and the correlated pH increase.
The Hai Tran, Ashokanand Vimalanandan, Georgi Genchev, Johannes Fickert, Katharina Landfester, Daniel Crespy, Michael Rohwerder: Regenerative Nano-Hybrid Coating Tailored for Autonomous Corrosion Protection. Advanced Materials (2015) doi: 10.1002/adma.201501044
After 3 years of fruitful cooperation of the Johannes Gutenberg University, the Technical University Kaiserslautern and Sensitec GmbH a final closure meeting was held in the presence of the Science Minister in Rhineland-Palatinate, Vera Reiß. The STeP Project was a new approach to transfer scientific know-how from universities directly into an industrial environment. The main focus was on developing tunnel magneto-resistance sensors as well as their possible applications.
“The STeP Project is a Europe-wide unique success of cooperation between Universities and industry.” Vera Reiss said “Within record time the project partners have built a bridge from basic research in the laboratories to industrial feasibility.”
The project was funded by the European Regional Development Fund (ERDF), the Ministry of Science and the Ministry of Economy of Rhineland-Palatine.
A press release (german) can be found here.
Skyrmions are candidates for future data storage and information processing
Small magnetic whirls may revolutionize future data storage and information processing if they can be moved rapidly and reliably in small structures. A team of scientists of Johannes Gutenberg University Mainz (JGU) and TU Berlin, together with colleagues from the Netherlands and Switzerland, has now been able to investigate the dynamics of these whirls experimentally. The skyrmions, as these tiny whirls are called after the British nuclear physicist Tony Skyrme, follow a complex trajectory and even continue to move after the external excitation is switched off. This effect will be especially important when one wants to move a skyrmion to a selected position as necessary in a future memory device. This research was published in the journal Nature Physics with a student of the Graduate School of Excellence Materials Science in Mainz (MAINZ) as the first author.
More information can be found here.
The project combines the superconducting quantum circuits with spin waves in ferromagnets to study single magnon creation and detection. Exploring spin wave dynamics in thin films by coupling to a superconducting qubit complements conventional measurement techniques based on photon, electron or neutron scattering methods, which require highly populated excitations. The work combines magnetic materials physics is with quantum resolved spectroscopy and coherence measurements on intrinsic dynamic states.
The MultiRev ERC Proof-of-Concept grant of M. Kläui builds on the ERC Starting Grant awarded earlier and implements ideas on magnetic sensing in devices that are compatible with industrial manufacturing. Developing sensors based on magnetic domain walls opens a whole new range of sensing applications that combine non-volatility and thus low power with versatility and reliability and this development will be carried out in conjunction with leading industrial partners.
The complete article can be found here (german).
Together with their cooperation partner Centre de Recherche Public – Gabriel Lippmann (Luxembourg) the group of Prof. Katja Heinze is awarded the Interregional Research Award 2014 (first prize, 35.000 €). In this multinational cooperation project (SURFAMINE) – funded by the Fonds National de la Recherche – novel intelligent foils for food packaging have been developed. Within the SURFAMINE project the teams have designed, synthesized and employed novel pigments for incorporation into a plasma-deposited layer suitable for food packaging. These intelligent foils detect spoiled food via a colorimetric signal of the embedded pigment upon its interaction with volatile amines formed by bacterial decomposition of amino acids.
Auszeichnung für hohe Leistungen auf dem Gebiet der Physik und herausragende Beiträge zu Nanomagnetismus und Spindynamik
In the area of functional ruthenium complexes our research was initially largely focused on fundamental questions concerning the manipulation of excited states in terms of relative energy, persistence and chemical stability, and the tuning of ground-state redox potentials to control electron-transfer reactions. We deepened our understanding by applying rather simple ligand-field arguments in the design of ligands and with the tremendous help of DFT calculations. The orthogonal chemical functionality (amine/carboxylic acid) furthermore predestines this metallo amino acid for incorporation into larger, highly complex architectures and into hierarchically ordered structures, as demonstrated in molecular peptide conjugates for photoinduced electron-transfer as well as energy-transfer reactions, in nanoscale hybrid architectures and bulk materials for light harvesting and light generation. This fundamental research has now made a step towards potential applications in dye-sensitized solar cells and light-emitting electrochemical cells.
A. Breivogel, C. Kreitner, K. Heinze: Redox and Photochemistry of Bis(terpyridine)ruthenium(II) Amino Acids and their Amide Conjugates – from Understanding to Applications. Eur. J. Inorg. Chem., 32, 5468-5490 (2014)
MPI-P scientist, Dr. Wurm, was presented with the gold medal for his excellent research in chemical science at the EuCheMS Chemistry Congress.
Dr. Frederik Wurm was awarded the Georg Manecke Prize for outstanding junior researchers in the field of polymer research.
The energy stored in the triplet states of organic molecules, capable of energy transfer via an emissive process (phosphorescence) or a nonemissive process (triplet-triplet transfer), is actively dissipated in the presence of molecular oxygen. The reason is that photoexcited singlet oxygen is highly reactive, so the photoactive molecules in the system are quickly oxidized. Oxidation leads to further loss of efficiency and various undesirable side effects. In this work we have developed a structurally diverse library of hyperbranched unsaturated poly(phosphoester)s that allow efficient scavenging of singlet oxygen, but do not react with molecular oxygen in the ground state, i.e., triplet state. The triplet-triplet annihilation photon upconversion was chosen as a highly oxygen-sensitive process as proof for a long-term protection against singlet oxygen quenching, with comparable efficiencies of the photon upconversion under ambient conditions as in an oxygen-free environment in several unsaturated polyphosphates. The experimental results are further correlated to NMR spectroscopy and theoretical calculations evidencing the importance of the phosphate center. These results open a technological window toward efficient solar cells but also for sustainable solar upconversion devices, harvesting a broad-band sunlight excitation spectrum.
Marsico, F., Turshatov, A., Pekoz, R., Avlasevich, Y., Wagner, M., Weber, K., Donadio, D., Landfester, K., Baluschev, S., Wurm, F. R.: Hyperbranched Uncaturated Polyphosphates as a Protective Mtrix for Long-Term Photon Upconversion in Air. Journal of the American Chemical Society 136 (31), 11057-11064, 2014. doi: 10.1021/ja5049412
Spin transport electronics (spintronics) is commonly considered as a promising candidate for future information technology, which motivates the search for new materials for optimum device performance. The key parameter for the magnitude of spin transport effects is the spin polarization, which ideally amounts to 100 % in so-called half-metals. In our recent publication in Nature Communications we demonstrate for the first time half-metallicity at room temperature for a Heusler compound. Investigating a thin film of the compound Co2MnSi by spin-resolved UV-photoemission spectroscopy, we were able to reveal by the in-situ analysis the high spin polarization. The LMU München physicochemists PD Dr. Jan Minar, Professor Jürgen Braun, and Professor Hubert Ebert, supported by Dr. Stanislav Chadov and Prof. Claudia Felser from the MPI-CPfS Dresden, provided the theoretical framework for this study.
Original publication: http://www.nature.com/ncomms/2014/140530/ncomms4974/full/ncomms4974.html
Selbstreinigende Oberflächen nutzt die Natur schon lange. Auf Lotusblättern sorgen Mikrostrukturen dafür, dass Wasser abperlt und Schmutz mitnimmt. Wesentlich schwieriger ist dieser Effekt bei öligen Substanzen erreichbar. Im Labor gelingen neuerdings Oberflächen, die zugleich wässrige und ölige Flüssigkeiten abweisen. Beschichtet man damit Membranen für Herz-Lungen-Maschinen, werden diese nicht mehr vom Blut verstopft.
Vollmer, D., Papadopoulos, P. and Butt, H.-J.: Wenn selbst Öl abperlt. Physik in unserer Zeit, 45, 228–233 (2014)
On-surface synthesis is a promising strategy for fabrication functional molecular devices directly on a support surface. An important step towards exploiting the potential of on-surface synthesis for molecular electronics is to extend the range of substrates to bulk insulators, as they provide electronic decoupling of the molecular structures from the underlying support. In this publication in Angewandte Chemie, Robert Lindner from the Kühnle group presents a novel strategy for the photochemical activation of a substrate-guided reaction of C60 molecules on calcite.
Lindner, R., Pahe, P., Kittelmann, M., Gourdon, A., Bechstein, R. and Kühnle, A.: Substrate Templating Guides the Photoinduced Reaction of C-60 on Calcite. Angew. Chem. Int. Ed., 53, 7952-7955 (2014)
In a collaborative research effort by the groups of Waldvogel and Heinze a novel molybdenum(V) complex has been designed and fully characterized. This complex displays a higher reactivity and selectivity in the dehydrogenative aryl-aryl coupling. Side reactions are drastically reduced. First mechanistic studies based on DFT calculations and EPR spectroscopic measurements were conducted in order to understand the enhanced reactivity pattern.
M. Schubert, J. Leppin, K. Wehming, D. Schollmeyer, K. Heinze, S. R. Waldvogel: Powerful Fluoroalkoxy-Molybdenum(V) Reagent for the Selective Oxidative Arene Coupling Reaction. Angew. Chem. 2014, 126, 2527-2530 (2014) DOI: 10.1002/ange.201309287. Angew. Chem. Int. Ed. 2014, 53, 2494-2497 (2014) DOI: 10.1002/anie.201309287
Powerful Fluoroalkoxy-Molybdenum(V) Reagent for the Selective Oxidative Arene Coupling Reaction
Official start of CINEMA as interdisciplinary research center funded by the federal state Rhineland-Palatinate. See press release (in German).
Mainz/Brussels. The European Research Council (ERC), an institution established by the EU Commission, announced on 26th September 2013 in Brussels that Professor Hans-Jürgen Butt and Professor Kurt Kremer, two directors at the Max Planck Institute for Polymer Research (MPI-P) in Mainz, will each be awarded an ERC Advanced Grant.
Gutenberg Research College approves the concept of CINEMA for an official start on 1.1.2014