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Complex correlated states emerging from many-body interactions between quasiparticles (electrons, excitons and phonons) are at the core of condensed matter physics and material science. In low-dimensional materials, quantum confinement affects the electronic, and subsequently, optical properties for these correlated states. Here, by combining photoluminescence, optical reflection measurements and ab initio theoretical calculations, we demonstrate an unconventional excitonic state and its bound phonon sideband in layered silicon diphosphide (SiP2), where the bound electron–hole pair is composed of electrons confined within one-dimensional phosphorus–phosphorus chains and holes extended in two-dimensional SiP2 layers. The excitonic state and emergent phonon sideband show linear dichroism and large energy redshifts with increasing temperature. Our ab initio many-body calculations confirm that the observed phonon sideband results from the correlated interaction between excitons and optical phonons. With these results, we propose layered SiP2 as a platform for the study of excitonic physics and many-particle effects.

In the synovial joint, mechanical force creates an important signal that influences chondrocyte behavior. The conversion of mechanical signals into biochemical cues relies on different elements in mechanotransduction pathways and culminates in changes in chondrocyte phenotype and extracellular matrix composition/structure. Recently, several mechanosensors, the first responders to mechanical force, have been discovered. However, we still have limited knowledge about the downstream molecules that enact alterations in the gene expression profile during mechanotransduction signaling. Recently, estrogen receptor α (ERα) has been shown to modulate the chondrocyte response to mechanical loading through a ligand-independent mechanism, in line with previous research showing that ERα exerts important mechanotransduction effects on other cell types, such as osteoblasts. In consideration of these recent discoveries, the goal of this review is to position ERα into the mechanotransduction pathways known to date. Specifically, we first summarize our most recent understanding of the mechanotransduction pathways in chondrocytes on the basis of three categories of actors, namely mechanosensors, mechanotransducers, and mechanoimpactors. Then, the specific roles played by ERα in mediating the chondrocyte response to mechanical loading are discussed, and the potential interactions of ERα with other molecules in mechanotransduction pathways are explored. Finally, we propose several future research directions that may advance our understanding of the roles played by ERα in mediating biomechanical cues under physiological and pathological conditions.

Two-dimensional (2D) magnets have been the recent research focus due to their potential to meet requirements of continuous miniaturization of spintronic devices. However, very few intrinsic 2D ferromagnetic materials, in particular room-temperature magnets, have been demonstrated because of spin fluctuations and disturbed superexchange caused by the dimensional reduction. Herein, a synchronous ultrasonic exfoliation and doping method is proposed to fabricate ferromagnetic 2D black phosphorus (BP) through the adsorption of phthalocyanine cobalt (CoPc). The electron transfer from BP to CoPc is confirmed by X-ray photoelectron spectroscopy, which is believed to be responsible for the ferromagnetic ground state in as-doped BP (Co-BP) with a saturation magnetization of 0.18 emu g−1. The density functional theory calculations well-support the charge transfer and the origin of ferromagnetism in Co-BP. In addition, the electron transfer results in the restricted activity of lone pair electrons, which might improve the antioxidant capacity of BP. Our study shed light on room-temperature ferromagnetism in 2D materials.

Ammonia (NH3) is pivotal to the fertilizer industry and one of the most commonly produced chemicals1. The direct use of atmospheric nitrogen (N2) had been challenging, owing to its large bond energy (945 kilojoules per mole)2,3, until the development of the Haber–Bosch process. Subsequently, many strategies have been explored to reduce the activation barrier of the N≡N bond and make the process more efficient. These include using alkali and alkaline earth metal oxides as promoters to boost the performance of traditional iron- and ruthenium-based catalysts4–6 via electron transfer from the promoters to the antibonding bonds of N2 through transition metals7,8. An electride support further lowers the activation barrier because its low work function and high electron density enhance electron transfer to transition metals9,10. This strategy has facilitated ammonia synthesis from N2 dissociation11 and enabled catalytic operation under mild conditions; however, it requires the use of ruthenium, which is expensive. Alternatively, it has been shown that nitrides containing surface nitrogen vacancies can activate N2 (refs. 12–15). Here we report that nickel-loaded lanthanum nitride (LaN) enables stable and highly efficient ammonia synthesis, owing to a dual-site mechanism that avoids commonly encountered scaling relations. Kinetic and isotope-labelling experiments, as well as density functional theory calculations, confirm that nitrogen vacancies are generated on LaN with low formation energy, and efficiently bind and activate N2. In addition, the nickel metal loaded onto the nitride dissociates H2. The use of distinct sites for activating the two reactants, and the synergy between them, results in the nickel-loaded LaN catalyst exhibiting an activity that far exceeds that of more conventional cobalt- and nickel-based catalysts, and that is comparable to that of ruthenium-based catalysts. Our results illustrate the potential of using vacancy sites in reaction cycles, and introduce a design concept for catalysts for ammonia synthesis, using naturally abundant elements. Ammonia is synthesized using a dual-site approach, whereby nitrogen vacancies on LaN activate N2, which then reacts with hydrogen atoms produced over the Ni metal to give ammonia.

Electrides are unique in the sense that they contain localized anionic electrons in the interstitial regions. Yet they exist with a diversity of chemical compositions, especially under extreme conditions, implying generalized underlying principles for their existence. What is rarely observed is the combination of electride state and superconductivity within the same material, but such behavior would open up a new category of superconductors. Here, we report a hexagonal Nb5Ir3 phase of Mn5Si3-type structure that falls into this category and extends the electride concept into intermetallics. The confined electrons in the one-dimensional cavities are reflected by the characteristic channel bands in the electronic structure. Filling these free spaces with foreign oxygen atoms serves to engineer the band topology and increase the superconducting transition temperature to 10.5 K in Nb5Ir3O. Specific heat analysis indicates the appearance of low-lying phonons and two-gap s-wave superconductivity. Strong electron–phonon coupling is revealed to be the pairing glue with an anomalously large ratio between the superconducting gap Δ 0 and T c, 2Δ 0/k B T c = 6.12. The general rule governing the formation of electrides concerns the structural stability against the cation filling/extraction in the channel site. Coexistence of electride behavior and superconductivity is observed in a hexagonal phase of a Nb5Ir3 intermetallic with tunable electronic properties by introducing foreign atoms. A team led by Yaoqing Zhang and Hideo Hosono from Japan Science and Technology Agency and Tokyo Institute of Technology report a new hexagonal phase in the phase diagram of Nb–Ir binary intermetallics with interesting interplay of superconductivity and electride state. The electride state is formed by electrons detaching from the atoms but localizing in a one-dimensional channel space. This electride becomes a superconductor below a transition temperature of about 9.4 K, which could be enhanced to 10.5 K upon filling interstitial cavities with foreign oxygens. The results suggest a general rule governing the formation of electrides and form the basis for novel stable functional electrides.

The excitonic insulator is a long conjectured correlated electron phase of narrow-gap semiconductors and semimetals, driven by weakly screened electron–hole interactions. Having been proposed more than 50 years ago, conclusive experimental evidence for its existence remains elusive. Ta2NiSe5 is a narrow-gap semiconductor with a small one-electron bandgap EG of TC=326 K, a putative excitonic insulator is stabilized. Here we report an optical excitation gap Eop ∼0.16 eV below TC comparable to the estimated exciton binding energy EB. Specific heat measurements show the entropy associated with the transition being consistent with a primarily electronic origin. To further explore this physics, we map the TC–EG phase diagram tuning EG via chemical and physical pressure. The dome-like behaviour around EG∼0 combined with our transport, thermodynamic and optical results are fully consistent with an excitonic insulator phase in Ta2NiSe5.

Electrically pumped ultraviolet random lasing was achieved in metal-insulator-semiconductor (MIS) diodes based on ZnO films at room temperature. The ZnO films were grown by plasma assisted molecular beam epitaxy. Two different kinds of insulator layers, SiO x (0

In this paper, 3D flower-like Au-ZnO microstructures with controlled morphology and dimensions were synthesized by a facile one-step aqueous solution route at room temperature, and the photocatalytic properties of these structures were investigated. The as-prepared flower-like Au-ZnO structures with a diameter of about 3 μm consisted of many ZnO nanosheets which interacted with each other. These nanosheets, which were successfully decorated by Au NPs, showed an average thickness of 10 nm and a single-crystalline structure with {2-1-10} planar surfaces. The growth process of Au-ZnO structures and the effects of trisodium citrate on the nucleation and growth of ZnO were investigated. The formation of Au NPs in this experiment was discussed too. The Au-ZnO structures showed higher photocatalytic activity than that of pure ZnO.

The Na-doped p-type ZnO thin films were prepared by DC reactive magnetron sputtering. Two types of substrates were used for separate testing purposes: silicon wafers for crystallinity measurements and glass slides for electrical and optical transmittance measurements. The lowest room-temperature resistivity under the optimal condition was 59.9 Ω cm, with a Hall mobility of 0.406 cm2 V−1s−1 and a carrier concentration of 2.57 × 1017 cm−3. The Na-doped ZnO thin films possessed a good crystallinity with c-axis orientation and a high transmittance (∼85%) in the visible region. The effects of the substrate temperature on the crystallinity and the electrical properties were discussed.