The design of new composite materials using extreme biomimetics is of crucial importance for bioinspired materials science. Further progress in research and application of these new materials is impossible without understanding the mechanisms of formation, as well as structural features at the molecular and nano‐level. It presents a challenge to obtain a holistic understanding of the mechanisms underlying the interaction of organic and inorganic phases under conditions of harsh chemical reactions for biopolymers. Yet, an understanding of these mechanisms can lead to the development of unusual—but functional—hybrid materials. In this work, a key way of designing centimeter‐scale macroporous 3D composites, using renewable marine biopolymer spongin and a model industrial solution that simulates the highly toxic copper‐containing waste generated in the production of printed circuit boards worldwide, is proposed. A new spongin–atacamite composite material is developed and its structure is confirmed using neutron diffraction, X‐ray diffraction, high‐resolution transmission electron microscopy/selected‐area electron diffraction, X‐ray photoelectron spectroscopy, near‐edge X‐ray absorption fine structure spectroscopy, and electron paramagnetic resonance spectroscopy. The formation mechanism for this material is also proposed. This study provides experimental evidence suggesting multifunctional applicability of the designed composite in the development of 3D constructed sensors, catalysts, and antibacterial filter systems.
The thermal expansion of carbon‐supported Pt nanoparticles with different particle size has been studied in‐situ via X‐ray diffraction at temperatures from 100 to 300 K. The thermal expansion coefficient (TEC) of investigated Pt/C nanoparticles is always superior to that of bulk Pt. When the grain size D decreases from 11 to 3 nm, the TEC nonlinearly increases by about 1.66 × 10−6 K−1 which corresponds to a variation of ∼20% from bulk Pt. The obtained experimental dependence of TEC for Pt/C nanoparticles has been interpreted using different theoretical approaches. A comparison of the considered models with the experimental data reveals the best agreement from the binding order–length–strength model with the size dependence of TEC experimentally found in carbon‐supported Pt nanoparticles.
Magnetic frustration, the competition among exchange interactions, often leads to novel magnetic ground states with unique physical properties which can hinge on details of interactions that are otherwise difficult to observe. Such states are particularly interesting when it is possible to tune the balance among the interactions to access multiple types of magnetic order. We present antlerite Cu 3 SO 4 (OH) 4 as a potential platform for tuning frustration. Contrary to previous reports, the low-temperature magnetic state of its three-leg zigzag ladders is a quasi-one-dimensional analog of the magnetic state recently proposed to exhibit spinon-magnon mixing in botallackite. Density functional theory calculations indicate that antlerite's magnetic ground state is exquisitely sensitive to fine details of the atomic positions, with each chain independently on the cusp of a phase transition, indicating an excellent potential for tunability.
Yb- and Ce-based delafossites were recently identified as effective spin-1/2 antiferromagnets on the triangular lattice. Several Yb-based systems, such as NaYbO2, NaYbS2, and NaYbSe2, exhibit no long-range order down to the lowest measured temperatures and therefore serve as putative candidates for the realization of a quantum spin liquid. However, their isostructural Ce-based counterpart KCeS2 exhibits magnetic order below T N = 400 mK, which was so far identified only in thermodynamic measurements. Here we reveal the magnetic structure of this long-range ordered phase using magnetic neutron diffraction. We show that it represents the so-called ‘stripe-yz’ type of antiferromagnetic order with spins lying approximately in the triangular-lattice planes orthogonal to the nearest-neighbor Ce–Ce bonds. No structural lattice distortions are revealed below T N, indicating that the triangular lattice of Ce3+ ions remains geometrically perfect down to the lowest temperatures. We propose an effective Hamiltonian for KCeS2, based on a fit to the results of ab initio calculations, and demonstrate that its magnetic ground state matches the experimental spin structure.
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