Physics

High Resolution Image Download MS PowerPoint Slide Phase-pure synthesis has been a major challenge for transition-metal oxynitrides due to their sensitivity to synthesis conditions and limited understanding of their underlying thermodynamics. Beta-phase tantalum oxynitride (β-TaON), a promising candidate for (photo)catalytic applications, is particularly difficult to reproducibly synthesize as a single-phase material at equilibrium. In this study, we developed and experimentally validated a thermodynamic model to identify optimal conditions for the single-phase synthesis of β-TaON via ammonolysis reactions. Gibbs free energies of reactant, product, and byproduct phases were predicted as a function of temperature using first-principles calculations with the quasi-harmonic approximation (QHA), as well as implemented from available thermodynamic databases. Utilizing these Gibbs energies, the calculation of phase diagrams (CALPHAD) approach was employed to develop a thermodynamic model for assessing the phase equilibria associated with the ammonolysis reactions, enabling prediction of temperature-dependent synthesis windows for β-TaON. Experimental syntheses were carried out across a range of temperatures and gas conditions, validating model predictions and iteratively refining the model accuracy through an integrated feedback loop. Co-flown gases beyond ammonia and water were also shown to be influential on β-TaON phase purity and reaction kinetics. A three-dimensional (3D) phase diagram predicted on the axes of parameters that can be controlled during practical synthesis quantitatively reveals a narrow, phase-pure synthesis window for β-TaON.

In this work, the pyrene-based linker 1,3,6,8-tetrakis( p -benzoic acid)pyrene (H 4 TBAPy) is used for the synthesis of rare-earth (RE) metal–organic frameworks (MOFs) featuring chain-based secondary building units with Y(III) and the series of 15 lanthanoids, yielding two different MOFs. One named RE-CU-05 with Y(III) and Gd(III) to Lu(III) and the second named RE-CU-06 with La(III) to Eu(III). Synchrotron X-ray diffraction measurements were used to determine the local structure of the nine RE-CU-05 analogues through pair distribution function (PDF) analysis, while electron diffraction (ED) and Rietveld refinement were used for structure solution of the six RE-CU-06 analogues. RE-CU-05 and RE-CU-06 were studied for the selective photooxidation of the sulfur mustard simulant 2-chloroethyl ethyl sulfide to 2-chloroethyl ethyl sulfoxide, achieving over 98% conversion in 10 min (La-CU-06) or 15 min (Tb-, Tm- and Yb-CU-05), with half-lives of 3.4 and 4.6 min for La-CU-06 and Tb-CU-05, respectively. These half-lives are competitive with those reported for other pyrene-based MOFs with much larger BET areas such as RE-CU-10 and Zr-NU-1000 under the same reaction conditions. The outstanding performance of RE-CU-05 and RE-CU-06 is attributed to the balance between chromophore density, pyrene-core spacing and orientation, surface area, and pore accessibility, which enables efficient light utilization and fast mass-transfer processes, highlighting the potential of chain-based MOFs as efficient photocatalysts.

Single-phase white phosphors are highly desirable for achieving stable white light-emitting diodes (w-LEDs). In this work, a series of Ce 3+ -, Tb 3+ -, and Sm 3+ -doped as well as codoped Ca 3 LuAl 3 B 4 O 15 (CLAB) phosphors were successfully synthesized, and white light was achieved by tuning relative doping concentrations. The phase structure, morphology, and optical properties were systematically investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence spectroscopy. Energy transfer from the parity-allowed Ce 3+ ions to the parity-forbidden Tb 3+ and Sm 3+ ions was confirmed through spectral analysis and comparison. Under 342 nm excitation, the optimized CLAB:1%Ce 3+,2.5%Sm 3+,10%Tb 3+ phosphor exhibits warm-white-light emission originating from three activators. In addition, the phosphor retains 71% and 42% of its initial emission intensity at 450 and 600 K, respectively, demonstrating the good thermal stability of the phosphor. By combining the optimized CLAB:1%Ce 3+,2.5%Sm 3+,10%Tb 3+ phosphor with a commercial 340 nm ultraviolet (UV) chip, a warm w-LED was fabricated, exhibiting CIE chromaticity coordinates of (0.3631, 0.3625), a correlated color temperature (CCT) of 4419 K, and a color rendering index (CRI) of 93. This study offers a newly designed single-phase white phosphor for high-quality warm w-LEDs.

To address harmful volatile emissions from formaldehyde-based adhesives and the high energy consumption of thermosetting adhesive curing, this study proposes a water-based, environmentally friendly adhesive inspired by natural liquid-liquid phase separation. A synergistic combination of silicone-acrylic (SA) emulsion, cationic polyamidoamine-epichlorohydrin (PAE), and plant-derived tannic acid (TA) was used to construct a phase-separated cross-linked network through multiple dynamic interactions. This bioinspired design enables low-temperature rapid curing, eliminating traditional high-temperature processes. The adhesive exhibits outstanding performance: cold-pressed plywood achieves a wet shear strength of 2.58 MPa, retaining 1.24 MPa after 72 h of continuous boiling, demonstrating reliable durability in extreme humid and hot environments and helping to reduce material waste and degradation-related losses. It also exhibits broad substrate applicability with bond strengths of 23.5 MPa for wood and 12.95 MPa for metals. Moreover, it can be processed into self-supporting films with high toughness (elongation of >350%) and high strength (tensile strength of >16.5 MPa). This work presents a strategy for high-performance, low-environmental-impact adhesives, which is promising for green composite manufacturing and clean production.

of the utility of Raman spectroscopy (RS) in capturing a snapshot of the biochemical changes that modulate the GBA and identify vibrational bands that are evidence of metabolites present in a murine model of ulcerative colitis. Acute colitis was induced in mice by administering dextran sulfate sodium (DSS) in drinking water. RS measurements identified 21 significant peaks in the serum, 21 in the cecum, and 22 in the thalamus region of the brain; these peaks were associated with broad metabolite classes and showed strong correlation to disease activity in colitis mice relative to healthy mice. Our findings showed that the thalamus has the most metabolite changes in the DSS-colitis model rather than the hypothalamus, which is known to be crucial in GBA communication. We identified six biochemical species, including unsaturated fatty acids, lipids, triglycerides, proteins/amide III, tryptophan, and threonine, that were common between the serum, cecum, and thalamus and may serve as early biomarkers of inflammatory response that drive gut-brain communication. Further, a Pearson's correlation analysis highlighted that neurotransmitters in the thalamus had moderate-to-strong correlations to serum amino acids and lipids/fatty acids in the gut. This fundamental study provides a snapshot of the early biochemical changes that enable crosstalk between the gut and brain in ulcerative colitis that can be translated to other disorders of the gut or brain in the future.

Anion exchange membrane (AEM) water electrolysis is a promising strategy for green hydrogen production, which enables the use of non-precious-metal catalysts. However, the activity and stability of oxygen evolution reaction (OER) catalysts are far from meeting the requirements of AEM water electrolysis at high current density. Herein, we report a high-entropy antiperovskite InN(NiCoFeCrV) 3 on nickel foam (denoted as InN(NiCoFeCrV) 3 @NF) as a structurally integrated electrode for boosting the OER process. The high-entropy-driven elemental synergy effectively promotes the reconstruction dynamics and creates more active sites. The leaching of Cr/V triggers surface reconstruction to generate oxyhydroxides as the real active phases. Subsequently, the Mott–Schottky heterojunctions are established at the interface of oxyhydroxides and InN(NiCoFeCrV) 3, which creates a built-in electric field and offers a fast charge transfer path. Moreover, the high-entropy effect modulates the electronic structure and optimizes the OER process. The combined high conductivity and structural stability of InN(NiCoFeCrV) 3 enable efficient and durable water oxidation at high current densities. The InN(NiCoFeCrV) 3 @NF electrode exhibits an ultralow overpotential of 279 mV at 100 mA cm –2 . The integrated AEM electrolyzer with InN(NiCoFeCrV) 3 @NF shows an ultralow cell voltage of 1.70 V to achieve a high current density of 500 mA cm –2 with outstanding stability for over 400 h. This work not only reports a strategy to design highly active and stable OER electrocatalysts for AEM electrolyzers but also provides insights into the charge transfer mechanism of antiperovskites.

High-density nanocrystalline transparent ceramics of cubic alumina (γ-Al2O3) were fabricated using nanocrystalline γ-Al2O3 powder as the starting material under a temperature–pressure condition of 4.2 GPa and 300 °C. Subsequently, the optical transmission and shock-induced luminescence performance of the as-fabricated transparent ceramics, serving as optical window materials, were characterized under varying shock pressures via plate impact experiments on a two-stage light gas gun. The experimental results show that, in contrast to the optical signal attenuation observed in single-crystal sapphire under shock loading, the γ-Al2O3 nanocrystalline transparent ceramic windows still maintain good optical transparency for 1550 nm wavelength laser within the shock pressure range of approximately 36–96 GPa. Meanwhile, at similar shock pressures, the absolute radiance of the intrinsic shock-induced luminescence from the nanocrystalline γ-Al2O3 transparent ceramics is an order of magnitude lower than that of c-cut single-crystal sapphire. This demonstrates that the nanocrystalline alumina window material possesses superior shock optical transparency and weaker shock-induced luminescence compared to single-crystal sapphire.

The internal structural conditions of large-scale stone carvings are difficult to assess using conventional nondestructive testing techniques because of their large size, complex geometry, and long service history. In this work, the 3D internal structure of the stone carvings at Mingshan Temple was investigated using cosmic ray muon imaging. Muon flux data acquired from multiple observation points and directions were used to derive path-integrated density distributions. A 3D density inversion model incorporating geometric constraints was then developed, and an iterative reconstruction algorithm with an adaptive-relaxation factor was applied to image the cavity roof structure and the overlying mountain body. A refined 3D model, constructed by integrating unmanned aerial vehicle-derived digital elevation data with interior point-cloud measurements of the grotto, was introduced as a geometric prior to improve reconstruction stability under complex structural conditions. The results reveal a distinct low-density anomaly on the southern side of the roof slab of cave 8, consistent with the gullies observed on site, demonstrating the effectiveness of the proposed approach. These results indicate that cosmic ray muon imaging provides a promising nondestructive tool for internal structural investigation and risk assessment of large-scale stone cultural heritage.

Halide perovskites’ remarkable optoelectronic properties stem from their metal halide octahedra. This connection underscores the promise of systematically extracting the physical rules encoded in octahedral motifs to steer the discovery of optoelectronic materials. Here, we develop an octahedral motif-centric, data-driven framework that couples interpretable machine learning with high-throughput first-principles calculations to accelerate the discovery of optoelectronic semiconductors. We construct motif-based descriptors to train a gradient boosting regression tree model for thermodynamic stability evaluation, achieving a low mean absolute error of 83 meV per atom on datasets comprising ~104 materials. Leveraging the model to accelerate materials discovery, we identify 19 unexplored thermodynamically stable semiconductors with favorable optoelectronic properties. Among them Ca2GaCoO5 was successfully synthesized and experimentally verified to exhibit a strong visible light photoresponse. These results support the effectiveness of the machine learning framework for octahedra-containing semiconductors and suggest its potential for extension to other motif-based materials families. Metal-halide octahedra underpin the strong optoelectronic properties of halide perovskites, but general design rules remain difficult. Yang et al. develop an octahedral motif-based model coupled with first principles screening to discover 19 new semiconductors and validate one experimentally.

Alternating twisted multilayer graphene presents a compelling multiband system, with a coexistence of Dirac bands and flat bands, for exploring superconductivity. However, the roles of flat bands and Dirac bands played in determining the superconductivity remain elusive. Here, we focus on the alternating twisted quadralayer graphene to reveal unconventional superconducting behaviors. We disentangle Dirac bands and flat bands, revealing a Coulomb interaction-induced band broadening effect. We further quantify the electric-field-dependent evolution of the critical temperature and coherence length, and estimate the flat-band Fermi velocity and superfluid stiffness via critical current measurements. Our results demonstrate an electric-field–tunable coupling strength within the superconducting phase, revealing unconventional properties with vanishing Fermi velocity and large superfluid stiffness. Combined with our theoretical analysis, these observations support a picture in which displacement-field-driven hybridization between flat and Dirac-like bands enhances the quantum-metric contribution to superconductivity, offering new insight into multiband flat-band superconductivity in moiré systems. The authors study flat-band superconductivity in alternating twisted quadra-layer graphene by transport, finding an electric-field-tunable coupling strength within the superconducting phase, vanishing Fermi velocity and large superfluid stiffness. They attribute these phenomena to quantum metric contributions, mediated by hybridization of Dirac bands and flat bands.

Engineering artificial systems by twisting van der Waals materials provides an excellent platform for exploring emergent quantum phenomena. Recent advances in fabrication enable studies of interfacial superconductivity in twisted cuprates. In our work, we fabricate superconducting quantum interference devices (SQUID) that utilize the twisted interface of Bi2Sr2CaCu2O8+δ, a high-Tc cuprate superconductor. By measuring the magnetic field modulation of differential resistance, we find a π phase difference between the two Josephson junction arms of the SQUID reflecting chiral time-reversal symmetry-broken superconducting order – a crucial aspect inaccessible to single Josephson junction. Our observations also indicate co-tunneling of the Cooper pairs. Additionally, these SQUIDs are well-suited for use as state-of-the-art flux sensors near 77 K. Stabilizing superconducting orders using twisted interfaces and probing them via quantum interference opens avenues for understanding unconventional superconductors. Our architecture can probe charge transport and superconducting order symmetry at interfaces in other systems, demonstrating broad applicability beyond cuprates. The authors study superconducting quantum interference devices (SQUIDs) constructed from twisted thin flakes of the cuprate superconductor Bi2Sr2CaCu2O8+δ. They find a π phase difference between the two Josephson junction arms of the SQUID reflecting chiral superconducting order of opposite chirality in the two arms.

Abstract Semilocal density functionals such as the Perdew-Burke-Ernzerhof (PBE) functional substantially underestimate experimental band gaps. Hybrid functionals address this band gap problem by admixing a fraction of Fock exchange to semilocal exchange. The optimal mixing parameter depends on the specific material and can be identified as the inverse dielectric constant (dielectric-dependent hybrid functional, DDH). Here, we show that dielectric constants obtained using the r 2 SCAN meta-GGA functional are significantly more accurate than dielectric constants obtained using the semilocal PBE functional. We propose the DD-r 2 SCANH functional, a dielectric-dependent hybrid functional based on r 2 SCAN. DD-r 2 SCANH can outperform the standard PBE-based DDH in terms of band gaps and other electronic structure properties. Particularly marked improvements are obtained for narrow-gap semiconductors such as Ge and InAs, where PBE wrongly predicts a metallic phase, but r 2 SCAN opens a band gap.

Scalable production of high-quality 2D nanosheets remains challenging because existing top-down and bottom-up methods typically face a trade-off between material quality, yield, and cost. Here, we report the seconds-scale (~12 s) production of high-quality 2D crystals via polycyclic aromatic hydrocarbon radical anion (PAH•-)-mediated organoalkali intercalation. The tunable reduction potential and electron-transfer capability of PAH•- enable ultrafast alkali-ion intercalation within seconds in the stable potential of layered hosts. For graphite, sodium naphthalenide (Na-Naph) forms a stage-1 graphite intercalation compound in only 1 s, and subsequent hydrolysis-driven exfoliation in 11 s yields graphene with >88% yield and >50% single-layer ratio, with a negligible increase in defect density (ID/IG ratio from ~0.10 to ~0.11). This strategy is further extended to the exfoliation of few-layer (3-5 layers) transition-metal sulfides, selenides, and tellurides while preserving their intrinsic crystal phases. This work establishes a practical, high-yield route for rapid intercalation-driven exfoliation, offering a scalable platform for manufacturing high-quality 2D crystals. The scalable and cost-effective production of high-quality 2D nanosheets remains challenging. Here the authors report the seconds-scale production of high-quality 2D crystals (graphene and transition metal dichalcogenides) via polycyclic aromatic hydrocarbon radical anion (PAH•-)-mediated organoalkali intercalation and subsequent hydrolysis-driven exfoliation.

The development of dynamically responsive soft porous crystals (SPCs) is crucial for advanced gas separation due to their stimuli-triggered structural transitions. Herein, we report a 3D covalent organic framework (FCOF-XJ) constructed from flexible tetrahedral (F-3D-Td) and rigid tetrahedral (3D-Td) building blocks, exhibiting unique temperature-dependent selective adsorption of xenon (Xe). FCOF-XJ features thermoresponsive -O-C-C-C-O- single bonds that enable temperature-dependent conformational switching. The adaptive pore structure of FCOF-XJ enables an Xe-triggered gate-opening effect, with 4 times increase of Xe adsorption and a high Xe/Kr selectivity (36.9 at 298 K, 1 bar) among porous organic materials, surpassing most of metal-organic frameworks (MOFs). Breakthrough experiments reveal a defined high-purity Xe recovery window from Xe/Kr mixtures under non-ideal dynamic conditions, enabled by thermoresponsive pore-gating dynamics. This work establishes a flexible COF platform for thermoresponsive and Xe-selective capture based on guest-triggered framework gating. ‘Dynamically responsive soft porous crystals are crucial for advanced gas separation due to their stimuli-triggered structural transitions. Here the authors report a novel 3D covalent organic framework constructed from flexible tetrahedral and rigid tetrahedral building blocks, exhibiting unique temperature-dependent selective adsorption of xenon.’

Voltage-controlled ion insertion provides a powerful strategy for the analog tuning of material properties, enabling adaptive devices such as neuromorphic transistors and smart displays. Among tunable materials, mixed ionic-electronic conducting oxides undergoing topotactic phase transitions are particularly compelling due to their dramatic property changes between fully oxidized and fully reduced states. However, intermediate oxidation states remain largely underexplored because of significant control limitations. In this work, we investigate the topotactic phase transition in strontium ferrite (SrFeO3-δ) thin films by progressively and precisely modulating and quantifying oxygen non-stoichiometry via solid-state electrochemical pumping. This fine-tuning approach unveils the co-existence of multiple stable phases in equilibrium configurations across a broad range of oxidation states. A crystallographic mixing model that captures the structural–electronic coupling underlying this phenomenon is proposed, complemented by a defect chemistry framework that quantitatively describes the oxidation mechanism under applied voltage. These findings highlight the critical role of intermediate states in governing functional properties and open new pathways for designing advanced ionotronic oxygen-responsive devices. The authors demonstrate voltage control of oxygen in strontium ferrite, revealing stable intermediate phases that enable durable analog electronic states beyond simple on/off switching.

Energetic electrons in Earth's inner radiation belt pose significant hazards to spacecraft systems, with the strongest radiation in low-Earth orbit (LEO) mostly confined to the South Atlantic Anomaly (SAA) region. Once considered stable, the inner belt is now understood to exhibit significant variability. Using data from the low-Earth-orbit Macau Science Satellite-1 mission, we report transient distortions of the SAA radiation environments, observationally characterized by enhanced fluxes of energetic electrons outside the traditional SAA radiation region, appearing either attached to or detached from its boundary. We show that these distortions can be explained by large-scale electric-field perturbations that adiabatically alter the electron mirror heights, which can be further modulated by ultra-low-frequency waves. Test-particle simulations successfully reproduce the observational features and provide crucial constraints on properties of the associated electric fields. These findings reveal a distinct manifestation of inner-belt variability, extending the electron radiation risks beyond the expected boundaries of the SAA radiation environments.