Die Fachgruppe Festkörperchemie & Materialforschung startete im Jahr 2021 während der Corona-Pandämie eine Online-Vortragsreihe zur Förderung des wissenschaftlichen Austauschs durch ortsunabhängige Vorträge. Aufgrund des hohen Zuspruchs wird das Format auch nach Pandämie-Ende mit großem Erfolg weitergeführt. Die Teilnahme ist kostenlos, doch ist eine separate Registrierung für jedes Seminar erforderlich. Im Anschluss an jedes Online-Seminar gibt es die Gelegenheit zum persönlichen Austausch mit den Vortragenden.
Organisation: Dr. Sebastian Klemenz, Dr. Alexander Knebel, Ass.-Prof. Dr. Heidi Schwartz, Dr. Simon Steinberg
Prof. Dr. Thomas F. Fässler (Technische Universität München)
June 27, 2023 5:00pm (Berlin time)
Prof. Dr. Daniel C. Fredrickson (University of Wisconsin, Madison)
June 13, 2023 5:00pm (Berlin time)
Prof. Dr. Susan M. Kauzlarich (University of California, Davis)
June 6, 2023 5:00pm (Berlin time)
Ass.-Prof. Dr. Axel Gansmüller (Université de Lorraine)
April 4, 2023
6:00pm (Berlin time)
Registrierung
Shedding light on photoactive hybrid materials with solid state NMR
Nowadays, a way of developing novel medicinal compounds focuses on confinement of known active molecules inside nanoparticles. Additionally, the delivery of therapeutic agents can be controlled by photodissociation and photoisomerization processes of photoactive drugs and nanoparticles. Therefore hybrid materials emerge, exhibiting new properties related to nano-confinement. This work shows how the application of solid-state Nuclear Magnetic Resonance (SS-NMR) provides access to the structural and dynamical properties of the confined molecules, that govern the drug release and photophysical properties.
In a first example, a joint SS-NMR and Differential Scanning Calorimetry (DSC) characterization strategy will provide a picture of the distribution of curcumin inside very heterogeneous materials. As a consequence, we show that other factors than compartmentalization (in particular, polymorphism and molecular dynamics of host compounds) should also be considered to understand the release properties (1).
In a second example using a joint Pair Distribution Function (PDF) and SS-NMR study, the structure and the dynamics of a confined Metal Nitrosyl complex are characterized. Interestingly, temperature and hydration ranges are identified, for which the complex stays associated, although it is in a “liquid-like state”. Towards the limit of water absence, movement restrictions of the confined complexes are elucidated providing information on water modulated host / guest interactions that explain their exceptional crystallization properties in the confined environment (2,3).
The last example will show how low temperature photoinduced metastable states can be observed by NMR in crystalline Metal Nitrosyl complexes. In particular, different commutation properties within the same crystal are observed for two inequivalent cations, thus showing the possible effect of molecular environment on optical properties (4).
(1) Kim, S.; Stébé, M.-J.; Blin, J.-L.; Pasc, A.; J. Mater. Chem. B 2014, 2(45), 7910–7917.
(2) Deligey, F.; Bouguet-Bonnet, S.; Doudouh, A.; Marande, P.-L.; Schaniel, D.; Gansmüller, A.; J. Phys. Chem. C 2018.
(3) Bendeif, E.-E.; Gansmuller, A.; Hsieh, K.-Y.; Pillet, S.; Woike, T.; Zobel, M.; Neder, R. B.; Bouazaoui, M.; Hamzaoui, H. E.; Schaniel, D.; RSC Adv. 2015, 5(12), 8895–8902.
(4) Gansmüller, A.; Mikhailov, A. A.; Kostin, G. A.; Raya, J.; Palin, C.; Woike, T.; Schaniel, D.; Anal. Chem. 2022, 94(10), 4474–4483.
Prof. Dr. Hubert Huppertz (Universität Innsbruck)
March 21, 2023
6:00pm (Berlin time)
Registrierung
Von der Grundlagenforschung zur Anwendung: Synthese neuer Leuchtstoffe für LED´s
Seit mehreren Jahren beschäftigt sich ein Teil der Arbeitsgruppe Huppertz an der Universität Innsbruck mit der Synthese neuer Leuchtstoffe über Festkörpersynthesen, die sowohl unter Normaldruck als auch unter extremen Hochdruckbedingungen (bis 150.000 bar) durchgeführt werden. Der Vortrag gibt eine Einführung in die grundlegenden Arbeitstechniken gefolgt von der Darstellung aktueller Forschungsergebnisse der letzten Jahre aus den Gebieten der Alkalilithosilicate und Oxonitridosilicate, wie beispielsweise des neuen schmalbandigen Rotleuchtstoffes SrAl2Li2O2N2:Eu2+ (SALON)[1] und seiner ungeordneten Varianten SrAl2−xLi2+xO2+2xN2−2x (x = 0.12 und 0.66).[2]
[1] G. J. Hoerder, M. Seibald, D. Baumann, T. Schröder, S. Peschke, P. C. Schmid, T. Tyborski, P. Pust, I. Stoll, M. Bergler, C. Patzig, S. Reißaus, M. Krause, L. Berthold, T. Höche, D. Johrendt, H. Huppertz, Nat. Commun. 2019, 10, 1824.
[2] G. J. Hoerder, S. Peschke, K. Wurst, M. Seibald, D. Baumann, I. Stoll, H. Huppertz, Inorg. Chem. 2019, 58, 12146-12151.
Prof. Tyrel McQueen, PhD. (Johns Hopkins University)
February 28, 2023
6:00pm (Berlin time)
Quantum Materials
Chemistry is all about understanding and controlling the properties of matter -- Where are the electrons? How do particular arrangements of atoms and bonds result in the zoo of behaviors known in matter? What new properties can be created by arranging atoms in unnatural configurations? Today, there are about 50 million known chemical compounds. Where and how will the next billion be discovered, and what new properties will they have [1]?
In this talk, I will highlight the progress being made to address these questions, with a particular focus on quantum materials [2]. Quantum mechanics is essential to understand individual atoms. Yet, in many cases, it is not necessary to treat the entire system quantum mechanically – quantum mechanics need only be considered locally, while the collective properties of a large collection of atoms adopts behavior describable with classical models. But this is not true in all cases – in some compounds, so-called quantum materials, the observed behavior defies classical models and requires a full quantum mechanical description – that is, the quantum behavior is ‘writ large’ across macroscopic length scales. I will give examples of recent advances and discoveries of quantum materials that have implications ranging from sustainable energy to information technology, and also more recent connections to the rapidly growing area of quantum information science and engineering. I will provide a perspective on how tools of chemistry – especially those related to understanding bonding and the motion of nuclei and electrons – can be applied to make further advances in these areas.
[1] dx.doi.org/10.1021/acs.accounts.8b00382
[2] www.energyfrontier.us/content/what-are-quantum-materials
Jun.-Prof. Dr. Frederik Haase (Martin Luther Universität Halle Wittenberg)
February 14, 2023
6:00pm (Berlin time)
Designing frustrated assembly in reticular materials
The assembly of reticular or net-like materials is governed by solid-state chemistry, but unlike classical solid-state materials, reticular materials are composed of organic building blocks. The design of these organic molecules provides an extraordinary degree of control over the structure and properties of reticular materials. Rather than using this control to create new "well-behaved" and predictable structural outcomes, we introduce competing interactions and incompatible symmetries in the building blocks to induce frustration. The resulting structures from this frustrated assembly exhibit emergent structural features such as non-stoichiometry, distorted building blocks and motifs, and size-limited assembly. These effects can be seen in covalent organic frameworks (COFs), metal organic frameworks (MOFs) and hydrogen bonded frameworks (HOFs). Through the emergence of these structural features, we aim to introduce functionality into reticular materials that is not available in "well behaved" structures.
Prof. Dr. Martin Jansen (Max-Planck Institut für Festkörperforschung, Stuttgart)
May 24, 2022
5:00pm (Berlin time)
"Von Volumeninkrementen zu ML und KI, Konzepte der Festkörperchemie im Wandel der Zeit"
Dr. Günther Thiele (Freie Universität Berlin)
May 10, 2022
5:00pm (Berlin time)
The Magic of Vacancies: Solid Solutions of Chalcogenido Metalates
The increasing demand of new technologies from microelectronics to superconductors, batteries, and spintronics for every day-life application encourages the introduction of new materials with improved properties and performance. Alkali metal sulfido metalates are well-known materials with a wide range of applications. Here, a novel class of these compounds is introduced with the stoichiometry of A2[M3Ch4] where A is an alkali metal (Na or K), M is a 3d transition metal (Mn … Zn), and Ch is either S or Se. The 2-3-4 compounds represent defect-variant structures of K2[Fe4Se4] with two-dimensionally extended anionic substructure of [MIICh4]6–. The compound class can be tailored by means of elemental combinations, where all components can be replaced by, or mixed with, a multitude of similar elements. This variety of elemental composition – a solid solution behavior – is used to tune the properties and the performance. The compounds display high dielectric constants (1120 at 1 kHz) as high-k materials as well as extraordinary ionic conductivities (24.37 mS∙cm–1 for K2[Fe3S4] at 295 K) which enables potential usage as solid-state electrolytes. The advantages include intrinsically increased charge densities and lifetime cycles, whilst reducing safety hazards and construction costs in ubiquitous mobile lithium-ion batteries, as well as next-generation sodium-/potassium-ion batteries. The center-metal vacancies in the structures induce additional charge transferring channels which result in increased conductivities. Moreover, the obtained compounds indicate large spontaneous magnetic exchange bias fields (35 mT for K2[Fe3S4] at 20 K), for potential spintronic applications. This phenomenon is a consequence of the coexistence of spin glass and antiferromagnetic orderings due to the center-metal vacancies in the lattice. The findings introduce a novel candidate for technological applications and could demonstrate the critical role of center-metal vacancies as a main source in tuning the electronic and magnetic properties of these materials. Metal-like band structures of the compounds are predicted by quantum chemical calculations, indicating Mott insulating behaviors.
Ass.-Prof. Dr. Christina Birkel (Arizona State University / TU Darmstadt)
May 03, 2022
5:00pm (Berlin time)
Expanding the compositional and microstructural space of layered and 2D materials (MAX phases and MXenes)
We are facing many exciting challenges in materials chemistry and being able to produce high-quality and new materials plays a key role in unraveling the almost endless list of open research questions and developing new technologies. My group focuses on the synthesis of new layered compounds (MAX phases) and 2D materials (MXenes). MAX phases are ternary transition metal-based carbides and nitrides that crystallize in a layered structure with space group P63/mmc. They are unique compounds because they can be described as ceramic metals (they are electrically and thermally conductive) and metallic ceramics (showing high temperature and oxidation resistance). Chemical exfoliation of the MAX phases leads to a relatively young class of 2D materials, the so-called MXenes, which have left almost no potential area of application untouched and will benefit from a greater chemical diversity amongst their family members. Traditionally, MAX phases are prepared by high-temperature solid-state methods, oftentimes under pressure, and the formation of side phases (binary carbides/nitrides and intermetallics) is very common and a challenge in the materials chemistry community. In this talk, I will show wet chemical-based synthesis strategies to access MAX phases that lead to new compositions as well as novel microstructures of these types of materials. For example, we have recently prepared MAX phase Cr2GaC in the form of microwires, thick films and (hollow) microspheres. We study their (local) structure by X-ray and neutron diffraction and focus on their complex and unique transport properties.
Dr. Sabrina Disch (Universität zu Köln)
April 26, 2022
5:00pm (Berlin time)
Magnetic Nanoparticles – Intraparticle Magnetization and Interparticle Interactions
Magnetic nanoparticles find widespread attention with numerous applications, such as in nanomedicine or catalysis through the magnetic heating effect, in smart fluids, and active matter with self-propelling particles that can be manipulated with static and dynamic magnetic fields. Whereas the implementation of nanomagnetic properties into technological applications is progressing rapidly, fundamental questions remain challenging, such as the evolution of nanoscale magnetization and magnetization relaxation or the microscopic interaction between nanoscale magnetic units.
Our approach to such questions lies in the cross-scale investigation of structure and magnetization in nanostructured materials using a combination of X-ray and polarized neutron scattering. In this talk I will give insight into the nanoscale distribution of magnetic order and disorder within nanoparticles. Being intrinsic to nanomaterials, disorder effects crucially determine the magnetization properties of magnetic nanoparticles. I will further present our work on self-organization of nanoparticles into regular arrangements and the arising magnetic coupling phenomena.
T.T.-Prof. Dr.-Ing. Helge S. Stein (Karlsruher Institut für Technologie)
April 12, 2022
5:00pm (Berlin time)
Progress and prospects of autonomous materials science for energy storage
Materials science for secondary battery research is a complex and time intensive undertaking, that needs to be accelerated to meet todays and tomorrows demands for high performance and sustainable energy storage. Building upon first principles thinking we designed the platform of accelerated electrochemical energy storage research (PLACES/R) to fast track the electrode discovery process, electrolyte formulation optimization, interphase synthesis and characterization as well as batch cell manufacturing. We will share some of the design decisions, successes and failures in bootstrapping an entire 90 m2 laboratory that aims to go beyond the identification of performance trends and towards an A.I. guided materials acceleration platform in a single modular laboratory. We will demonstrate intention agnostic lab orchestration, instrument transferrable data management, high-throughput electrochemistry and automated cell manufacturing.
Prof. Dr. Wolfgang Bensch (Christian-Albrechts-Universität Kiel)
December 14, 2021
5:00pm (Berlin time)
Viele Semester Chemie – ein nicht nur wissenschaftlicher Rückblick
In dem Vortrag möchte ich auf wichtige Stationen meiner Karriere eingehen und über Begegnungen mit Personen und über Ereignisse berichten, die mich und meine wissenschaftlichen Arbeiten geprägt haben. Manchmal waren wir der Zeit weit voraus, manchmal war Durchhaltevermögen und Zähigkeit sehr wichtig. Um chemische Reaktionen unter realen Bedingungen verfolgen zu können, mussten wir in-situ-Techniken entwickeln. Unkenntnis hat letztlich zu langjährigen internationalen Kooperationen geführt und falsche Überlegungen machten den Weg frei für eine faszinierende Chemie.
Dr. Jannika Lauth (Leibniz-Universität Hannover)
November 30, 2021
5:00pm (Berlin time)
“Colloidal 2D Semiconductors: A Chemical Approach for Innovative Optoelectronics and Photonic Quantum Technologies"
Colloidal 2D semiconductors, so-called nanosheets and nanoplatelets, are only a few atom layers thick and exhibit promising optoelectronic properties that are chemically tunable between visible to infrared wavelengths. 2D semiconductors are strongly quantum-confined in their thickness dimension, resulting in the control, and fine-tuning of their narrow absorption and emission features. A key advantage of colloidal synthesis methods is the ability to grow not only ultrathin van der Waals structures but also intrinsically isotropic materials (e.g. cubic lead chalcogenides) into a strongly anisotropic crystal shape by the virtue of surface ligands and reaction conditions. I will touch on the synthetic tailoring of colloidal 2D semiconductors, on their integration into innovative optoelectronics (e.g. directed emission and polymer-encapsulation) and on their superior potential as single photon emitters for photonic quantum technologies.
Dr. Jörn Bruns (Universität Köln)
November 16, 2021
5:00pm (Berlin time)
“Chemistry under extreme conditions – from silicate analogue network structures to technetates”
Rude colleagues say that solid states chemists follow for their reactions only the principle "shake and bake". Of course, high temperatures help to overcome activation barriers. However, we all know that this is not enough. A multitude of other parameters play an essential role for efficient solid-state (chemical) reactions. I will present you how we use extremely strong oxidizing agents, such as sulfuric acid or its anhydride SO3, to synthesize silicate analogous materials such as borosulfates. In these, the charge compensating heteropolyanionic subunits are composed of vertex-linked (SO4)- and (BO4)-tetrahedra. In contrast to the immense structural diversity of silicates, the number of borosulfates is yet very limited and the extent of their properties is still unknown. In an effort to expand the knowledge on oxoanionic networks even further, we have also gone and tested our systems on rhenates, manganates and technetates. In this context, the handling of technetium and its compounds is another challenge. In addition to the acids, strong alkaline media can be a perfect medium for the synthesis of oxidic and oxoanionic materials. And when it comes to the respective counter cations, our research goes as far as the elements beryllium and uranium.
Using a wide array of analytical methods such as optical spectroscopy, magnetochemistry and photoelectron spectroscopy we try to investigate all samples as detailed as possible and corroborate our findings by quantum chemical calculations.
Herein, I will therefore present an overview of our investigations on borosulfates and oxometallates, the role of acidic and basic reaction conditions and the effects of the counter cations on the chemistry. It will turn out that “shake and bake” does not always hold true, and that there is more to solid state chemistry than meets the eye.
Jun.-Prof. Dr. Markus Suta (Heinrich-Heine-Universität Düsseldorf)
November 02, 2021
5:00pm (Berlin time)
"The principles of luminescence thermometry – An application also touching fundamental aspects of phosphors"
There is a growing demand on remote temperature sensing with spatial resolution at the micrometer scale and below. Ratiometric luminescence thermometry is a promising and non-invasive methodology for those length scales. Potential application areas range from in situ monitoring of temperature changes in chemical reactions, over in vivo bioimaging to investigation of fundamental thermodynamic phenomena at the nanoscale. A particularly simple way of luminescence thermometry employs an ensemble of non-interacting luminescent centers with two thermally coupled and radiatively emitting states from the same electron configuration. The luminescence intensity ratio then follows Boltzmann’s law. Trivalent lanthanoids with their narrow line 4fn-4fn luminescence doped into crystalline powders have emerged for this type of thermometry. The ultimate desire to design such thermometers for the application of interest requires, however, a careful understanding of both thermodynamic and kinetic concepts of their performance.
In this presentation, I will give a general overview over the foundations of this so-called Boltzmann-type thermometers. It will be demonstrated that every luminescent Boltzmann thermometer can be used for precise temperature measurements in only a small temperature window and what are strategies to overcome this obstacle. I will also show the relevance of excited state kinetics and how decisive the choice of the surrounding host compound for the lanthanoid ions is to control Boltzmann-type behavior of a luminescent thermometer. The interplay with energy transfer pathways will also be shortly highlighted. The presentation will conclude with a perspective on how seeking a better understanding of luminescent thermometers can also help understand the efficiency of phosphors quite generally.
Dr. Alexander Knebel (Friedrich-Schiller-Universität Jena)
October 19, 2021
5:00pm (Berlin time)
“Disruptive Membrane Technology based on MOF Materials: Towards Advanced CO2 Capture and Green Production”
To stop global warming and greenhouse gas emissions, metal-organic frameworks (MOFs) are highly potential candidates for the development of a disruptive membrane technology in key separation and purification applications. Membranes - as simple, physical barriers - are able to capture CO2 actively, e.g. by placing them in a waste gas stream. Additionally, membranes can reduce the energy consumption of separation and purification processes in comparison to conventional separations (e.g. distillation) by up to 80%, thus reducing CO2 passively. Therefore, our focus lies on materials engineering for the purpose of carbon capture and the green production: The preparation of MOF particles and thin films, development of neat MOF or mixed matrix polymer-filler membranes and their application in gas separation. We are bridging the gap from synthesis and shaping of materials. We realize novel material concepts by home-build technical equipment, characterize physical properties of MOFs and demonstrate unique separation mechanisms. We show the development of novel material concepts: Fundamentally, we investigate stimuli responsive, switchable MOFs that can control gas separation in-situ towards a multi-purpose “universal membrane”; Focusing on real-life applications, we develop ways towards high-performance materials. Here, we invented the first MOF-based liquids with permanent porosity and applied them for the green production of propylene.
Dr. Anna Isaeva (Universiteit van Amsterdam)
June 22, 2021
6:00-7:30pm (Berlin time)
"New Quantum Materials from Inorganic 2D Building Blocks: The Upswing of van der Waals Structures"
Layered compounds with van der Waals bonding are an attractive playground for materials design. The idea that promising compounds may be created by combining 2D layers with various functionalities (magnetic, electronic, optical, etc.) by stacking them in a periodic 3D crystal lattice is being actively explored by chemists, physicists and theorists alike. However, the whole is seldom a mere sum of the parts and the interlayer interactions in such materials are not as weak as they may seem at first. The layers often ‘see’ each other, and an interplay of their individual properties gives rise to novel phenomena. Thanks to the recent methodological and technological developments, materials science is now able to explore single van der Waals monolayers and discovers their unique magnetic, superconducting and transport properties originating from quantum effects. It is now also possible to trace how these properties evolve while transiting from 3D to 2D structures. These new possibilities attract many to the vibrant interdisciplinary research field on so called ‘van der Waals quantum materials’. While fully appreciating the prospects that layered materials hold for new chemistry and physics, one should not forget about the other side of the medal: the formation of competing polymorphs, or metastable, or poorly ordered phases with strong stacking disorder challenge the synthesis. I will give a brief overview of the nowadays most prominent van der Waals materials ‘beyond graphene’ (e.g. transition metal dichalcogenides, CrI3 and other magnetic 2D materials, 2D topological insulators and superconductors) and then focus on the family of (MnBi2Te4)(Bi2Te3)n, n = 0-3, layered compounds. They exhibit both magnetic and topological (quantized surface transport) properties that can be tuned by compositional and structural modifications.
Dr. Hana Bunzen (Universität Augsburg)
June 8, 2021
6:00-7:30pm (Berlin time)
“Metal-organic frameworks for drug delivery in cancer therapy”
Delivering therapeutic agents in a sufficient concentration to a target site is a major challenge in the treatment of many diseases including cancer treatment. Conventional ways of drug administration are often characterized by a limited effectiveness, poor biodistribution and lack of selectivity. Fortunately, this limitation could be overcome by using drug nanocarriers. In this context, metal-organic frameworks (MOFs) - porous coordination polymers – seem to be very promising. MOFs comprise two building components – metal ions (or clusters) and polydentate organic ligands. They are known as materials featuring a high internal surface area, which can be used to load various molecules including drugs. In our research we focus on the delivery of arsenic drugs. Arsenic compounds such as arsenic trioxide have been shown as promising drugs in cancer treatment but due their high intrinsic toxicity, their delivery in therapeutic concentrations is challenging. Here nanomedicine and nanoparticles as drug carriers show great potential. Moreover, by combining MOF nanoparticles with agents suitable for magnetic resonance imaging such as superparamagnetic Fe3O4 nanoparticles, we could prepare theranostics, i.e. materials suitable not only for drug delivery but also for diagnosis. Such materials are expected to play a significant role in the dawning era of personalized nanomedicine.
Dr. Viktor Hlukhyy (Technische Universität München)
May 25, 2021
6:00-7:30pm (Berlin time)
"Fe-, Co- and Ni- based polar intermetallic compounds: synthesis, structural peculiarities and properties"
Given the fact that the chemical composition and crystal structure of a compound define its properties, a thorough understanding of the factors that allow for the realization of a certain combination of elements is an essential point when designing new applicable materials. In the case of intermetallic compounds, however, the composition-structure-property relationships are often poorly understood. Complex structural chemistry of such polar intermetallics is caused by an interplay between covalent, metallic, and ionic interactions. The discovery of high-temperature superconductivity in iron-pnictides has sparked enormous interest in intermetallic compounds containing square-planar lattice arrangement of transition metal atoms, particularly in ThCr2Si2-type representatives. It is known that the superconducting properties are very sensitive to the structural parameters of d-metal layers, and as such the structural flexibility for chemical substitution in ThCr2Si2-type materials makes this family of intermetallic compounds interesting candidates for studying the structure-property relationship. In this talk, the synthesis, structural features, and magnetic properties of new polar intermetallic compounds based on iron, cobalt, and nickel, with square-planar layers and other 2D-, 1D- and 3D- arrangements of transition metal atoms will be discussed.
Dr. Bertold Rasche (Universität Köln)
April 27, 2021
6:00-7:30pm (Berlin time)
“Can Electrochemistry Help to Understand Superconductivity? – In-situ electrochemical X-ray diffraction of β-Fe1+xSe”
Systematic investigations of phase systems and transitions are the foundation of understanding complex physical phenomena such as superconductivity. One example in which the lack of such a systematic knowledge has led to contradictory results is β-Fe1+xSe. The superconductivity of this “simple” two-dimensional, layered structure has been reported to be heavily dependent on the composition and closely related structural transitions, defects and various superstructures with overall inconsistent results. The difficulties arise from the narrow phase width of β-Fe1+xSe (0.01 < x < 0.04), a small deviation from the 1:1 ratio and its manifold of neighbouring phases. We report the precise post-synthetic control of the composition of β-Fe1+xSe by electrochemistry with simultaneous tracking of the concomitant structural changes via in-situ synchrotron X-ray diffraction. Via an externally applied potential, electrochemistry allows us to confirm the phase width of 0.01 < x < 0.04. We identify the superconducting state below 8 K, which in contrast to earlier reports is independent of the composition. However, in a second set of in situ X-ray diffraction experiments, we demonstrate that β-Fe1+xSe forms a new phase in the presence of oxygen above a 100 °C, which has the same anti-PbO type structure but is not superconducting down to 1.8 K. This electrochemical approach takes experiments for two-dimensional materials beyond intercalation reactions, and exploits the exquisite control provided by electrochemistry.
Dr. Janine George (Université catholique de Louvain)
April 13, 2021
6:00-7:30pm (Berlin time)
„Data-driven materials discovery and chemical understanding“
Developments in density functional theory (DFT) calculations, their automation and easy access to materials data have enabled ab initio high-throughput searches for new materials for numerous applications. These studies open up exciting opportunities to find new materials in a much faster way than based on experimental work alone. However, performing density functional theory calculations for several thousand materials can still be very time consuming. The use of, for example, faster chemical heuristics and machine-learned interatomic potentials would allow to consider a much larger number of candidate materials. In addition to DFT based high-throughput searches, the seminar will discuss two possible ways to accelerate high-throughput searches. Using data analysis on the structures and coordination environments of 5000 oxides, we were able to investigate a chemical heuristic – the famous Pauling rules – regarding its usefulness for the fast prediction of stable materials. We have also investigated how machine-learned interatomic potentials can be used to accelerate the prediction of (dynamically) stable materials. The use of these potentials makes vibrational properties accessible in a much faster way than based on DFT. Our results based on a newly developed potential for silicon allotropes showed excellent agreement with DFT reference data (agreement of the frequencies within 0.1-0.2 THz). In addition, we have successfully used high-throughput calculations in the search for new candidate materials for spintronic applications and ferroelectrics.
Jun.-Prof. Dr. Sebastian Henke (TU Dortmund)
March 30, 2021
6:00-7:30pm (Berlin time)
„Stimuli-Responsiveness, Melting and Glass Formation of Metal-Organic Frameworks “
Metal-organic frameworks (MOFs) are an emerging family of porous solid-state materials exhibiting huge potential for various technological applications (gas storage/separation, catalysis, drug delivery, sensing, etc.). These compounds are composed of inorganic building units (typically d-block metal ions, metal-(oxo/hydroxo)-clusters) which are interconnected by multidentate organic linkers to generate two- or three-dimensional extended networks, exhibiting huge internal surface areas and pore volumes. In this talk, I present our recent efforts in different areas of MOF chemistry. Firstly, I introduce flexible MOFs, which undergo dramatic structural changes as a function of guest molecule adsorption/desorption, temperature or mechanical pressure. By chemical modification or exchange of the frameworks’ building units, the structural response of the MOF can be tunes systematically. Secondly, I demonstrate the preparation of liquid MOFs and their corresponding glasses. MOF glasses represent a new class of glassy materials and own intrinsic porosity, similar to their crystalline parent compounds. We revealed that MOF glasses are able to adsorb even relatively large hydrocarbon gas molecules, thus enabling kinetic gas separation (i.e. the separation of propylene from propane). Finally, I present a new concept for the design of porous framework materials that can be processed (i.e. drop casted, crystallized, etc.) from aqueous solution. Our materials design strategy is based on amphiphilic organic building blocks which reversibly assemble/disassemble to micellar porous frameworks, mediated by coordination to alkali ions in aqueous solution.
Prof. Dr. Oliver Clemens (Universität Stuttgart)
March 23, 2021
6:00-7:30pm (Berlin time)
“Anion Chemistry of Energy Materials – Batteries, Tunable Properties, and Electrocatalysts”
Without doubt, topochemical reactions play an important role for our current batteries, e.g., within oxide-based cathode materials or carbon-based anode materials for lithium-ion batteries. However, topochemistry of oxide materials is by no means restricted to small cations, and perovskite as well as perovskite-related materials possess a vivid insertion chemistry for anions, making them interesting compounds for a broad range applications related to their multitude of functional properties, among them magnetism and superconductivity. In this talk, the use of topochemical reactions with anions to develop and understand new energy materials with tailored and tunable properties will be highlighted. These reactions cover the preparation of oxyfluorides and oxyhydroxides for fluoride-ion batteries and electrocatalytic (SOFC and PCFC) applications. Special focus will be set on using topochemistry for the reversible on/off-switching of material properties. Last but not least, the impact of anion and vacancy ordering on the intrinsic properties will be given, with a special focus on barium ferrates and cobaltates with perovskite-related structure, for which novel compounds could be prepared and structurally characterized.
PD Dr. Harun Tüysüz (MPI für Kohlenforschung)
March 2, 2021
6:00-7:30pm (Berlin time)
“Tailor-made Nanostructured Materials for Energy Conversion Applications”
My particular research interest is the design of well-defined nanostructured materials and studying their structure-activity relationships for sustainable energy-related catalytic applications. The focus of the first part of the lecture will be design and development of Co, Ni and Fe based electrocatalysts for oxygen evaluation reactions. This will be followed by the presentation of solid-state inorganic halide perovskites and their implementation as functional photocatalysts for prototype reactions.
zuletzt geändert am: 27.07.2023 11:40 Uhr von C.Kniep
