Nanosystems Initiative Munich

About: Nanosystems Initiative Munich is a facility organization based out in Munich, Germany. It is known for research contribution in the topics: Quantum dot & Perovskite (structure). The organization has 323 authors who have published 549 publications receiving 24316 citations.

Spin Hall magnetoresistance in antiferromagnet/heavy-metal heterostructures

Abstract: We investigate the spin Hall magnetoresistance in thin-film bilayer heterostructures of the heavy metal Pt and the antiferromagnetic insulator NiO. While rotating an external magnetic field in the easy plane of NiO, we record the longitudinal and the transverse resistivity of the Pt layer and observe an amplitude modulation consistent with the spin Hall magnetoresistance. In comparison to Pt on collinear ferrimagnets, the modulation is phase shifted by ${90}^{\ensuremath{\circ}}$ and its amplitude strongly increases with the magnitude of the magnetic field. We explain the observed magnetic field dependence of the spin Hall magnetoresistance in a comprehensive model taking into account magnetic-field-induced modifications of the domain structure in antiferromagnets. With this generic model, we are further able to estimate the strength of the magnetoelastic coupling in antiferromagnets. Our detailed study shows that the spin Hall magnetoresistance is a versatile tool to investigate the magnetic spin structure as well as magnetoelastic effects, even in antiferromagnetic multidomain materials.

Tunable Water and CO2 Sorption Properties in Isostructural Azine-Based Covalent Organic Frameworks through Polarity Engineering

Abstract: The use of covalent organic frameworks (COFs) in environmental settings such as atmospheric water capture or CO2 separation under realistic pre- and post-combustion conditions is largely unexplored to date. Herein, we present two isostructural azine-linked COFs based on 1,3,5-triformyl benzene (AB-COF) and 1,3,5-triformylphloroglucinol (ATFG-COF) and hydrazine building units, respectively, whose sorption characteristics are precisely tunable by the rational design of the chemical nature of the pore walls. This effect is particularly pronounced for atmospheric water harvesting, which is explored for the first time using COFs as adsorbents. We demonstrate that the less polar AB-COF acts as a reversible water capture and release reservoir, featuring among the highest water vapor uptake capacity at low pressures reported to date (28 wt % at <0.3 p p0−1). Furthermore, we show tailored CO2 sorption characteristics of the COFs through polarity engineering, demonstrating high CO2 uptake at low pressures ( <1 bar)...

Ultrafast helicity control of surface currents in topological insulators with near-unity fidelity.

Abstract: Bulk contributions to transport measurements often inhibit the study of the surface states of topological insulators. Here, Kastl et al. demonstrate high-fidelity helicity-dependent photocurrents in the surface states of Bi2Se3, controlled via circularly polarized light with a picosecond time-resolution.

Why conclusions from platinum model surfaces do not necessarily lead to enhanced nanoparticle catalysts for the oxygen reduction reaction

Abstract: Experiments on model surfaces commonly help in identifying the structural sensitivity of catalytic reactions. Nevertheless, their conclusions do not frequently lead to devising superior "real-world" catalysts. For instance, this is true for single-crystal platinum electrodes and the oxygen reduction reaction (ORR), an important reaction for sustainable energy conversion. Pt(111) is substantially enhanced by steps, reaching a maximum at short terrace lengths of 3-4 atoms. Conversely, regular platinum nanoparticles with similar undercoordinated defects are less active than Pt(111) and their activity increases alongside the terrace-to-defect ratio. We show here that a model to design ORR active sites on extended surfaces can also be used to solve this apparent contradiction and provide accurate design rules for nanoparticles. Essentially, only surfaces and nanostructures with concave defects can surpass the activity of Pt(111), whereas convex defects are inactive. Importantly, only the latter are present in regular nanoparticles, which is why we design various concave nanoparticles with high activities.

Advances in Quantum-Confined Perovskite Nanocrystals for Optoelectronics

Abstract: Metal halide perovskites have emerged as a promising new class of layered semiconductor material for light-emitting and photovoltaic applications owing to their outstanding optical and optoelectronic properties. In nanocrystalline form, these layered perovskites exhibit extremely high photoluminescence quantum yields (PLQYs) and show quantum confinement effects analogous to conventional semiconductors when their dimensions are reduced to sizes comparable to their respective exciton Bohr radii. The reduction in size leads to strongly blueshifted photoluminescence and large exciton binding energies up to several hundreds of meV. This not only makes them interesting for optoelectronic devices, but also enables complex architectures based on cascaded energy transfer. Here, an overview of the current state-of-the-art of quantum confinement effects in perovskite nanocrystals is provided, with a focus on synthetic strategies and resulting optical properties, characterization methods, and emerging applications.