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Short peptides are versatile molecules for the construction of supramolecular materials. Most reported peptide materials are hydrophobic, stiff, and show limited response to environmental conditions in the solid‐state. Herein, we describe a design strategy for minimalistic supramolecular metallo‐peptide nanofibers that, depending on their sequence, change stiffness, or reversibly assemble in the solid‐state, in response to changes in relative humidity (RH). We tested a series of histidine (H) containing dipeptides with varying hydrophobicity, XH, where X is G, A, L, Y (glycine, alanine, leucine, and tyrosine). The one‐dimensional fiber formation is supported by metal coordination and dynamic H‐bonds. Solvent conditions were identified where GH/Zn and AH/Zn formed gels that upon air‐drying gave rise to nanofibers. Upon exposure of the nanofiber networks to increasing RH, a reduction in stiffness was observed with GH/Zn fibers reversibly (dis‐)assembled at 60–70 % RH driven by a rebalancing of hydrogen bonding interactions between peptides and water. When these metallo‐peptide nanofibers were deposited on the surface of polyimide films and exposed to varying RH, peptide/water‐vapor interactions in the solid‐state mechanically transferred to the polymer film, leading to the rapid and reversible folding‐unfolding of the films, thus demonstrating RH‐responsive actuation. [ABSTRACT FROM AUTHOR]

Short peptides are versatile molecules for the construction of supramolecular materials. Most reported peptide materials are hydrophobic, stiff, and show limited response to environmental conditions in the solid‐state. Herein, we describe a design strategy for minimalistic supramolecular metallo‐peptide nanofibers that, depending on their sequence, change stiffness, or reversibly assemble in the solid‐state, in response to changes in relative humidity (RH). We tested a series of histidine (H) containing dipeptides with varying hydrophobicity, XH, where X is G, A, L, Y (glycine, alanine, leucine, and tyrosine). The one‐dimensional fiber formation is supported by metal coordination and dynamic H‐bonds. Solvent conditions were identified where GH/Zn and AH/Zn formed gels that upon air‐drying gave rise to nanofibers. Upon exposure of the nanofiber networks to increasing RH, a reduction in stiffness was observed with GH/Zn fibers reversibly (dis‐)assembled at 60–70 % RH driven by a rebalancing of hydrogen bonding interactions between peptides and water. When these metallo‐peptide nanofibers were deposited on the surface of polyimide films and exposed to varying RH, peptide/water‐vapor interactions in the solid‐state mechanically transferred to the polymer film, leading to the rapid and reversible folding‐unfolding of the films, thus demonstrating RH‐responsive actuation. [ABSTRACT FROM AUTHOR]

In-plane compressively strained α-Sn films have been theoretically predicted and experimentally proven to possess non-trivial electronic states of a 3D topological Dirac semimetal. The robustness of these states typically strongly depends on purity, homogeneity, and stability of the grown material itself. By developing a reliable fabrication process, we were able to grow pure strained α-Sn films on InSb(100), without heating the substrate during growth nor using any dopants. The α-Sn films were grown by molecular beam epitaxy, followed by experimental verification of the achieved chemical purity and structural properties of the film's surface. Local insight into the surface morphology was provided by scanning tunneling microscopy. We detected the existence of compressive strain using Mössbauer spectroscopy, and we observed a remarkable robustness of the grown samples against ambient conditions. The topological character of the samples was confirmed by angle-resolved photoemission spectroscopy, revealing the Dirac cone of the topological surface state. Scanning tunneling spectroscopy, moreover, allowed us to obtain an improved insight into the electronic structure of the 3D topological Dirac semimetal α-Sn above the Fermi level. [ABSTRACT FROM AUTHOR]

The physical properties of a nanoparticle change drastically when the particle size approaches the length scale of the relevant order parameter. Herein, we demonstrate the ferrimagnetic ground state of Cu2OSeO3 nanoparticles, which is otherwise a chiral magnet (including large-size skyrmionic spin texture) in its bulk form. Theoretical studies suggest that such a pure ferrimagnetic ground state in this material (with low Dzyaloshinskii–Moriya interaction to Heisenberg interaction ratio) is possible only in the presence of magneto-crystalline anisotropy energy when the confinement size approaches the skyrmion size (∼50 nm in bulk). These observations suggest the limit to realize an isolated single skyrmion. [ABSTRACT FROM AUTHOR]