6 Materialchemie
Filtern
Erscheinungsjahr
- 2021 (19) (entfernen)
Dokumenttyp
- Vortrag (12)
- Posterpräsentation (6)
- Forschungsdatensatz (1)
Sprache
- Englisch (15)
- Deutsch (3)
- Mehrsprachig (1)
Referierte Publikation
- nein (19) (entfernen)
Schlagworte
- Mechanochemistry (5)
- Flexible crystals (4)
- High-throughput computations (4)
- Data analysis (3)
- MOFs (3)
- Machine learning (3)
- Oxygen Reduction Reaction (3)
- PGM-free catalyst (3)
- Polymorphism (3)
- Waveguide (3)
Organisationseinheit der BAM
- 6.0 Abteilungsleitung und andere (19) (entfernen)
Eingeladener Vortrag
- nein (12)
The stability of materials is a very important property for materials discovery. In recent years, we have explored several approaches for advancing the prediction of the stability of crystals (e.g., classical chemical heuristics and machine-learned interatomic potentials). For example, we have assessed a famous chemical heuristic – the Pauling rules – regarding their usefulness for structure prediction. They are only of limited predictive power, i.e. the rules 2 to 5 only work for 13 % of all tested oxides. Furthermore, we have shown that machine-learned interatomic potentials can be used to predict phonon properties of a range of silicon allotropes accurately and, therefore, they can also be used to assess the dynamic stability of materials. To do so, we have developed new schemes to build reference databases for machine learned interatomic potentials.
Ein drastisch hoher Polyethylene Massenanteil wurde bei der Analytik der Umweltproben im Vergleich zu weiteren Polymeren festgestellt. Zu einem Überbefund des Polyethylene können strukturell verwandte Verbindungen wie z.B. Fette durch Signalüberlagerung führen. Mithilfe von beschleunigter Lösemittelextraktion soll die störende Komponente entfernt werden.
Mechanochemistry has emerged as one of the most interesting synthetic protocols to produce new materials. The development of mechanochemistry as a synthetic method is supported by excellent research by many groups worldwide in a wide range of applications. The potential of mechanochemistry is also reflected in the inclusion in IUPAC’s 10 chemical innovations that will change our world’.[1] Solvent-free methodologies lead to unique chemical processes during synthesis with the consequent formation of martials with new properties.2 In this contribution, we will discuss our recent results investigating the formation of (polymorphic) cocrystals, coordination polymers, metal oxides and metal nanoparticles.[3-8] We introduced different setups enabling in situ investigation of mechanochemical reactions using synchrotron XRD combined with Raman spectroscopy and thermography.
Mechanochemistry is increasingly used for synthesizing soft matter materials including metal organic compounds and cocrystals.1 The ever-increasing interest in this method is contrasted by a limited mechanistic understanding of the mechanochemical reactivity and selectivity. Time-resolved in situ investigations of milling reactions provide direct insights in the underlying mechanisms.2-4 We recently introduced different setups enabling in situ investigation of mechanochemical reactions using synchrotron XRD combined with Raman spectroscopy and thermography. The presented setup allows the detection of crystalline, amorphous, eutectic, and liquid intermediates. Furthermore, the chemical composition of the reaction mixture was found to be directly correlated with changes in the temperature profile of the reaction. The resulting deeper kinetic and thermodynamic understanding of milling processes is the key for future optimization of mechanochemical syntheses. In this contribution, we will discuss our recent results investigating the formation of (polymorphic) cocrystals and coordination polymers.2,3,5 Our results indicate that in situ investigation of milling reactions offer a new approach to tune and optimize mechanochemical syntheses.
Based on the nature of the deformation, molecular crystals can be defined as being plastically (irreversible) or elastically (reversible)bendable. The mechanical response of crystals is thereby directly related to they structure.The structural elements required for a specific mechanical behavior are known, so that compounds with these properties can be synthesized by applying the rules of crystal engineering.
Kristalle sind in der Regel spröde und neigen dazu, bei mechanischer Belastung zu brechen. Dieses Verhalten schränkt ihre Anwendungsmöglichkeiten stark ein. Durch die Entdeckung von mechanischer Flexibilität in Kristallen wurde dieses Problem gelöst. Je nach Art der Verformung können Kristalle in plastisch (irreversibel) oder elastisch (reversibel) biegbar unterteilt werden. Die Verbindung 4-Brom-6-[(6-chlorpyridin-2-ylimino)methyl]phenol (BCMPMP) ist ein vielversprechender Kandidat für die Anwendung als flexibler Waveguide. BCMPMP hat zwei verschiedene Polymorphe mit unterschiedlichen optischen und mechanischen Eigenschaften. Die spröden Kristalle der Form I zeigen eine sehr schwache Emission bei 605 nm (λex = 425 nm; Photolumineszenz-Quantenausbeute Φ = 0,4 %). Im Gegensatz dazu zeigt die plastische Form II eine starke Emission bei 585 nm (λex = 425 nm; Φ = 8,7 %). Aufgrund der mechanischen Flexibilität wurde die Eignung der Form II als Waveguide untersucht.
Crystalline molecular materials are usually brittle and are prone to break upon external mechanical force. This fragility poses challenges for their application in next-generation technologies, including sensors, synthetic tissues, and advanced opto-electronics. The recent discovery of mechanical flexibility in single crystals of molecular materials has solved this problem and enable the design of smart flexible device technologies. Mechanical flexibility of organic crystals can be tuned by altering the weak interactions in the crystal structure, for examples through polymorphism. Here we report 4-bromo-6-[(6-chlorolpyridin-2-ylimino)methyl]phenol (BCMPMP) as a promising candidate for future waveguide technologies. It turns out that BCMPMP has two different polymorphs with distinct optical and mechanical properties. Form I shows brittle behavior under mechanical stress and exhibits very weak emission at 605 nm (λex = 425 nm) together with a low fluorescence quantum yield (Φ = 0.4 %).In contrast, Form II has a large plastic (irreversible bending) regime and a bright emission at 585 nm (λex = 425 nm; Φ = 8.7 %). Making use of favorable mechanical fexiblity and optical properties, form II was explored as a bendable optical waveguide. Light was successfully propagated through a straight-shaped and mechanically deformed BCMPMP crystal. Depending on the light source, active or passive waveguiding could be achieved. So BCMPMP can also be used as a flexible wavelength filter.