Chirality-Induced Memristor of Chiral Nanostructured Half-Metallic Fe3O4 Films.

Spintronic memristors, which combine the nonvolatile characteristics of memristors with the scalability of a spin-transfer torque device, are expected to play a crucial role in advancing quantitative information processing. This field commonly relies on magnetic tunnel junctions, domain wall motion, and spin waves. Here, the discovery of chirality-induced memristor behavior in chiral nanostructured Fe3O4 films (CNFFs) is reported. These CNFFs are grown on fluorine tin oxide (FTO) substrates using enantiomeric glutamic acid (Glu) as symmetry-breaking agents and consist of arrays of oriented twisted nanofibers. At 100 K, the L-CNFF exhibits memristor behavior as a pinched hysteresis loop in the I-V curve, while the D-CNFF exhibits semiconductor behavior with constant electrical resistance. The intrinsic spin polarization of half-metallic Fe3O4 and the chirality-induced spin selectivity (CISS) are speculated to contribute to the memristor in one handedness of the chiral structure. These findings present a novel spinristor that combines the functions of a memristor and a spin-filter based on chiral structures, which may promote the development of spintronic devices.

Chiral mesostructured NiFe2O4 films with chirality induced spin selectivity.

Chiral mesostructured NiFe2O4 films (CMNFFs) were synthesized using L-/D-tyrosine as symmetry-breaking and structure-directing agents through a hydrothermal method. For the first time, chirality induced spin selectivity was directly observed in these ferrimagnetic materials using chirality-dependent magnetic-tip conducting atomic force microscopy (mc-AFM).

Ionic Liquids as Promisingly Multi-Functional Participants for Electrocatalyst of Water Splitting: A Review.

Ionic liquids (ILs), as one of the most concerned functional materials in recent decades, have opened up active perspectives for electrocatalysis. In catalyst preparation, ILs act as characteristic active components besides media and templates. Compared with catalysts obtained using ordinary reagents, IL-derived catalysts have a special structure and catalytic performance due to the influence of IL's special physicochemical properties and structures. This review mainly describes the use of ILs as modifiers and reaction reagents to prepare electrocatalysts for water splitting. The designability of ILs provides opportunities for the ingenious composition of cations or anions. ILs containing heteroatoms (N, O, S, P, etc.) and transition metal anion (FeCl4-, NiCl3-, etc.) can be used to directly prepare metal phosphides, sulfides, carbides and nitrides, and so forth. The special physicochemical properties and supramolecular structures of ILs can provide growth conditions for catalysts that are different from the normal media environment, inducing special structure and high performance. ILs as heteroatom sources are safe, green and easy to operate compared with traditional heteroatom sources. The strategy for using ILs as reagents is expected to realize 100% atomic transformation of reactants, in line with the concept of green chemistry. This review reflects the discovered work with the best findings from the literature. It will offer readers a deeper understanding on the development of IL-derived electrocatalysts and inspire them to ingeniously design high-performance electrocatalysts for water splitting.

Deep Eutectic Solvent-Mediated Electrocatalysts for Water Splitting.

As green, safe, and cheap solvents, deep eutectic solvents (DESs) provide tremendous opportunities to open up attractive perspectives for electrocatalysis. In this review, the achievement of DESs in the preparation of catalysts for electrolytic water splitting is described in detail according to their roles combined with our own work. DESs are generally employed as green media, templates, and electrolytes. A large number of hydrogen bonds in DESs result in supramolecular structures which have the ability to shape the morphologies of nanomaterials and then tune their performance. DESs can also serve as reactive reagents of metal electrocatalysts through directly participating in synthesis. Compared with conventional heteroatom sources, they have the advantages of high safety and designability. The "all-in-one" transformation strategy is expected to realize 100% atomic transformation of reactants. The aim of this review is to offer readers a deeper understanding on preparing DES-mediated electrocatalysts with higher performance for water splitting.

Synchronous quantitative analysis of chiral mesostructured inorganic crystals by 3D electron diffraction tomography.

Chiral mesostructures exhibit distinctive twisting and helical hierarchical stacking ranging from atomic to micrometre scales with fascinating structural-chiral anisotropy properties. However, the detailed determination of their multilevel chirality remains challenging due to the limited information from spectroscopy, diffraction techniques, scanning electron microscopy and the two-dimensional projections in transmission electron microscopy. Herein, we report a general approach to determine chiral hierarchical mesostructures based on three-dimensional electron diffraction tomography (3D EDT), by which the structure can be solved synchronously according to the quantitative measurement of diffraction spot deformations and their arrangement in reciprocal space. This method was verified on two samples-chiral mesostructured nickel molybdate and chiral mesostructured tin dioxide-revealing hierarchical chiral structures that cannot be determined by conventional techniques. This approach provides more precise and comprehensive identification of the hierarchical mesostructures, which is expected to advance our understanding of structural-chiral anisotropy at the fundamental level.

Spin Selectivity of Chiral Mesostructured Iron Oxides with Different Magnetisms.

Spin selectivity physically depends on either magnetic materials with strong internal magnetic fields or symmetry-breaking materials with large spin-orbit coupling (SOC). However, the spin selectivity of symmetry-breaking magnetic materials is not understood. Herein, the spin selectivity of iron oxides with different magnetisms arising from varying spin alignment is investigated. Chiral mesostructured films of Fe3 O4 (CMFFs), γ-Fe2 O3 (CMγFs), and α-Fe2 O3 (CMαFs), which share the same mesostructure, are prepared by a controllable calcination process of chiral mesostructured FeOOH films (CMOFs) grown on the substrate via an amino acid-induced hydrothermal route. CMFFs and CMγFs with ferrimagnetism exhibit magnetic field-dependent and simultaneously chirality-independent magnetic circular dichroism (MCD) signals, while CMαFs with antiferromagnetism exhibit chirality-dependent, magnetic field-independent MCD signals. It is speculated that the competitive effect between the spin alignment-induced and chirality-induced effective magnetic fields determines the energy splitting of opposite spins in the materials with different magnetisms.

Resistance-Chiral Anisotropy of Chiral Mesostructured Half-metallic Fe3 O4 Films.

Half-metallic materials are theoretically predicted to be metallic and insulating, which have not been confirmed experimentally, and the predictions are still in doubt. We report the resistance-chiral anisotropy (R-ChA), i.e., chirality-dependent electrical conductivity, in chiral mesostructured Fe3 O4 films (CMFFs) grown on the substrates via a hydrothermal method using amino acids as symmetry-breaking agents. Two levels of chirality exist in the CMFFs: primary distortion of the crystal lattice forms twisted nanoflakes, and secondary helical stacking of nanoflakes forms fan-shaped nanoplates. At temperatures below 30 K, the CMFFs exhibited metallic conductivity and insulation for one handedness and the other, respectively. The chirality-dependent effective magnetic fields were speculated to stabilize the opposite spin in the antipodal chiral frame, which led to the free transport of electrons in one handedness of the chiral structure and immobility for the other handedness.

Chiral Mesostructured NiO Films with Spin Polarisation.

Spin polarisation is found in the centrosymmetric nonferromagnetic crystals, chiral mesostructured NiO films (CMNFs), fabricated through the symmetry-breaking effect of a chiral molecule. Two levels of chirality were identified: primary nanoflakes with atomically twisted crystal lattices and secondary helical stacking of the nanoflakes. Spin polarisation of the CMNFs was confirmed by chirality-dependent magnetic-tip conducting atomic force microscopy (mc-AFM) and magnetic field-independent magnetic circular dichroism (MCD). Electron transfer in the symmetry-breaking electric field was speculated to create chirality-dependent effective magnetic fields. The asymmetric spin-orbit coupling (SOC) generated by effective magnetic fields selectively modifies the opposite spin motion in the antipodal CMNFs. Our findings provide fundamental insights for directional spin control in unprecedented functional inorganic materials.