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Van der Waals heterobilayers of transition metal dichalcogenides with spin–valley coupling of carriers in different layers have emerged as a new platform for exploring spin/valleytronic applications. The interlayer coupling was predicted to exhibit subtle changes with the interlayer atomic registry. Manually stacked heterobilayers, however, are incommensurate with the inevitable interlayer twist and/or lattice mismatch, where the properties associated with atomic registry are difficult to access by optical means. Here, we unveil the distinct polarization properties of valley-specific interlayer excitons using epitaxially grown, commensurate WSe 2 /MoSe 2 heterobilayers with well-defined (AA and AB) atomic registry. We observe circularly polarized photoluminescence from interlayer excitons, but with a helicity opposite to the optical excitation. The negative circular polarization arises from the quantum interference imposed by interlayer atomic registry, giving rise to distinct polarization selection rules for interlayer excitons. Using selective excitation schemes, we demonstrate the optical addressability for interlayer excitons with different valley configurations and polarization helicities. The interlayer coupling in van der Waals heterostructures is sensitive to the interlayer atomic registry. Here, the authors investigate the polarisation properties of epitaxially grown, commensurate WSe 2 /MoSe 2 heterobilayers with well-defined atomic registry, and observe negative, circularly polarized photoluminescence from interlayer excitons.

Photocatalytic reduction of CO 2 is a promising approach to achieve solar-to-chemical energy conversion. However, traditional catalysts usually suffer from low efficiency, poor stability, and selectivity. Here we demonstrate that a large porous and stable metal-organic framework featuring dinuclear Eu(III) 2 clusters as connecting nodes and Ru(phen) 3 -derived ligands as linkers is constructed to catalyze visible-light-driven CO 2 reduction. Photo-excitation of the metalloligands initiates electron injection into the nodes to generate dinuclear {Eu(II)} 2 active sites, which can selectively reduce CO 2 to formate in a two-electron process with a remarkable rate of 321.9 μmol h −1  mmol MOF −1 . The electron transfer from Ru metalloligands to Eu(III) 2 catalytic centers are studied via transient absorption and theoretical calculations, shedding light on the photocatalytic mechanism. This work highlights opportunities in photo-generation of highly active lanthanide clusters stabilized in MOFs, which not only enables efficient photocatalysis but also facilitates mechanistic investigation of photo-driven charge separation processes. Solar-to-chemical CO 2 reduction provides a means to use light’s energy for CO 2 removal and upgrading to useful products, although this photochemical conversion is challenging. Here, authors construct a Europium-containing metal-organic framework that selectively converts CO 2 to formate with light.

Currently, the most active electrocatalysts for the conversion of CO₂ to CO are gold-based nanomaterials, whereas non–precious metal catalysts have shown low to modest activity. Here, we report a catalyst of dispersed single-atom iron sites that produces CO at an overpotential as low as 80 millivolts. Partial current density reaches 94 milliamperes per square centimeter at an overpotential of 340 millivolts. Operando x-ray absorption spectroscopy revealed the active sites to be discrete Fe3+ ions, coordinated to pyrrolic nitrogen (N) atoms of the N-doped carbon support, that maintain their +3 oxidation state during electrocatalysis, probably through electronic coupling to the conductive carbon support. Electrochemical data suggest that the Fe3+ sites derive their superior activity from faster CO₂ adsorption and weaker CO absorption than that of conventional Fe2+ sites.

Aim Spinal cord injury (SCI) involves multiple pathological processes. Ferroptosis has been shown to play a critical role in the injury process. We wanted to explore whether zinc can inhibit ferroptosis, reduce inflammation, and then exert a neuroprotective effect. Methods The Alice method was used to establish a spinal cord injury model. The Basso Mouse Scale (BMS), Nissl staining, hematoxylin‐eosin staining, and immunofluorescence analysis were used to investigate the protective effect of zinc on neurons on spinal cord neurons and the recovery of motor function. The regulation of the nuclear factor E2/heme oxygenase‐1 (NRF2/HO‐1) pathway was assessed, the levels of essential ferroptosis proteins were measured, and the changes in mitochondria were confirmed by transmission electron microscopy and 5,5′,6,6′‐tetrachloro‐1,1′,3,3′‐tetraethyl‐imidacarbocyanine iodide (JC‐1) staining. In vitro experiments using VSC4.1 (spinal cord anterior horn motor neuroma cell line), 4‐hydroxynonenal (4HNE), reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA), glutathione (GSH), lipid peroxides, and finally the levels of inflammatory factors were detected to assess the effect of zinc. Results Zinc reversed behavioral and structural changes after SCI. Zinc increased the expression of NRF2/HO‐1, thereby increasing the content of glutathione peroxidase 4 (GPX4), SOD, and GHS and reducing the levels of lipid peroxides, MDA, and ROS. Zinc also rescued injured mitochondria and effectively reduced spinal cord injury and the levels of inflammatory factors, and the NRF2 inhibitor Brusatol reversed the effects of zinc. Conclusion Zinc promoted the degradation of oxidative stress products and lipid peroxides through the NRF2/HO‐1 and GPX4 signaling pathways to inhibit ferroptosis in neurons. Mechanisms underlying the repair of spinal cord injury through inhibiting ferroptosis with zinc.

The constituent particles of matter can arrange themselves in various ways, giving rise to emergent phenomena that can be surprisingly rich and often cannot be understood by studying only the individual constituents. Discovering and understanding the emergence of such phenomena in quantum materials—especially those in which multiple degrees of freedom or energy scales are delicately balanced—is of fundamental interest to condensed-matter research 1 , 2 . Here we report on the surprising observation of emergent ferroelectricity in graphene-based moiré heterostructures. Ferroelectric materials show electrically switchable electric dipoles, which are usually formed by spatial separation between the average centres of positive and negative charge within the unit cell. On this basis, it is difficult to imagine graphene—a material composed of only carbon atoms—exhibiting ferroelectricity 3 . However, in this work we realize switchable ferroelectricity in Bernal-stacked bilayer graphene sandwiched between two hexagonal boron nitride layers. By introducing a moiré superlattice potential (via aligning bilayer graphene with the top and/or bottom boron nitride crystals), we observe prominent and robust hysteretic behaviour of the graphene resistance with an externally applied out-of-plane displacement field. Our systematic transport measurements reveal a rich and striking response as a function of displacement field and electron filling, and beyond the framework of conventional ferroelectrics. We further directly probe the ferroelectric polarization through a non-local monolayer graphene sensor. Our results suggest an unconventional, odd-parity electronic ordering in the bilayer graphene/boron nitride moiré system. This emergent moiré ferroelectricity may enable ultrafast, programmable and atomically thin carbon-based memory devices. Electronic ferroelectricity is observed in a graphene-based moiré heterostructure, which is explained using a spontaneous interlayer charge-transfer model driven by layer-specific on-site Coulomb repulsion.

Van der Waals interactions with transition metal dichalcogenides were shown to induce strong spin-orbit coupling (SOC) in graphene, offering great promises to combine large experimental flexibility of graphene with unique tuning capabilities of the SOC. Here, we probe SOC-driven band splitting and electron dynamics in graphene on WSe 2 by measuring ballistic transverse magnetic focusing. We found a clear splitting in the first focusing peak whose evolution in charge density and magnetic field is well reproduced by calculations using the SOC strength of ~ 13 meV, and no splitting in the second peak that indicates stronger Rashba SOC. Possible suppression of electron-electron scatterings was found in temperature dependence measurement. Further, we found that Shubnikov-de Haas oscillations exhibit a weaker band splitting, suggesting that it probes different electron dynamics, calling for a new theory. Our study demonstrates an interesting possibility to exploit ballistic electron motion pronounced in graphene for emerging spin-orbitronics. By combining graphene with transition metal dichalcogenides, such as WSe2, it is possible to induce a large spin-orbit interaction in the graphene layer. Here, Rao et al study the spin-orbit coupling in graphene/WSe2 heterostructures using the ballistic transport based technique, known transverse magnetic focusing.

Electrocatalytic nitrogen reduction reaction (NRR) represents a promising sustainable approach for NH3 synthesis. However, the poor NRR performance of electrocatalysts is a great challenge at this stage, mainly owing to their low activity and the competitive hydrogen evolution reaction (HER). Herein, 2D ferric covalent organic framework/MXene (COF‐Fe/MXene) nanosheets with controllable hydrophobic behaviors are successfully prepared via a multiple‐in‐one synthetic strategy. The boosting hydrophobicity of COF‐Fe/MXene can effectively repel water molecules to inhibit the HER for enhanced NRR performances. By virtue of the ultrathin nanostructure, well‐defined single Fe sites, nitrogen enrichment effect, and high hydrophobicity, the 1H,1H,2H,2H‐perfluorodecanethiol modified COF‐Fe/MXene hybrid shows a NH3 yield of 41.8 µg h−1 mgcat.−1 and a Faradaic efficiency of 43.1% at −0.5 V versus RHE in a 0.1 m Na2SO4 water solution, which are vastly superior to the known Fe‐based catalysts and even to the noble metal catalysts. This work provides a universal strategy to design and synthesis of non‐precious metal electrocatalysts for high‐efficiency N2 reduction to NH3. COF‐Fe/MXene nanosheets are designed and prepared for electrocatalytic N2 reduction to NH3. Especially, the controllable hydrophobic properties of electrocatalysts can remarkably improve the nitrogen reduction reaction performances via inhibiting the competitive hydrogen evolution reaction at ambient conditions. This work opens up a universal approach to construct non‐precious metal electrocatalysts for ambient N2 fixation.

Globally, the incidence rate for breast cancer ranks first. Treatment for early-stage breast cancer is highly cost effective. Five-year survival rate for stage 0–2 breast cancer exceeds 90%. Screening mammography has been acknowledged as the most reliable way to diagnose breast cancer at an early stage. Taiwan government has been urging women without any symptoms, aged between 45 and 69, to have a screening mammogram bi-yearly. This brings about a large workload for radiologists. In light of this, this paper presents a deep neural network (DNN)-based model as an efficient and reliable tool to assist radiologists with mammographic interpretation. For the first time in the literature, mammograms are completely classified into BI-RADS categories 0, 1, 2, 3, 4A, 4B, 4C and 5. The proposed model was trained using block-based images segmented from a mammogram dataset of our own. A block-based image was applied to the model as an input, and a BI-RADS category was predicted as an output. At the end of this paper, the outperformance of this work is demonstrated by an overall accuracy of 94.22%, an average sensitivity of 95.31%, an average specificity of 99.15% and an area under curve (AUC) of 0.9723. When applied to breast cancer screening for Asian women who are more likely to have dense breasts, this model is expected to give a higher accuracy than others in the literature, since it was trained using mammograms taken from Taiwanese women.