Communications Materials最新文献

Two-dimensional (2D) aluminum nitride (AlN) represents a promising material with unique properties predicted by density functional theory (DFT), characterized by a honeycomb lattice where Al and N atoms exhibit threefold in-plane coordination. However, the synthesis of free-standing AlN nanosheets has been challenging due to the crystal configurations of the well-known bulk AlN, which presents a hexagonal wurtzite structure with a tetrahedral coordination, preventing its exfoliation to obtain nanosheets. Herein, we propose a facile method involving the preparation of layered-structured aluminum carbonitrides, Al₅C₃N, followed by exfoliation into AlN nanosheets, offering a potential route for producing 2D AlN. The Al₅C₃N precursor was chemically etched in hydrofluoric acid (HF), breaking the Al-C bonds and exposing the AlN nanosheets. The development of this synthesis method opens up opportunities towards the preparation of 2D AlN and the investigation of its unique properties for applications in sensors and microelectronics.

The integration of high-quality, ultrathin van der Waals (vdW) dielectrics with 2D semiconductors remains a critical bottleneck in the development of reliable, ultra-scaled field-effect transistors (FETs). Here, we report a comprehensive study of MoS₂-based FETs employing layered rhombohedral MnAl₂S₄ as the gate insulator, a previously unexplored vdW dielectric that can be isolated down to the monolayer limit. Devices fabricated in both top-gated (TG) and bottom-gated (BT) configurations exhibit excellent electrical performance, featuring low gate leakage, minimal hysteresis ( < 2 mV) under high electric fields up to 11 MV cm^-1 across a wide range of gate voltage sweep rates (0.001-10 Vs^-1). We observed a consistent counterclockwise hysteresis and an anomalous bias temperature instability (BTI), possibly caused by the diffusion of Mn interstitials and S vacancies formed inside the MnAl₂S₄ film during growth. Notably, we show that threshold voltage degradation at high temperatures was observed to be negligible, and hysteresis dynamics and very small BTI are reproducible over a long time, demonstrating the high reliability of our devices. In addition, the vdW interface between MnAl₂S₄ and MoS₂ in our device is of good quality and is expected to provide a small density of insulator defects, a promising gate dielectric for reliable 2D devices.

The integrity of structural materials is oftentimes defined by their resistance against catastrophic failure through dissipative plastic processes at the crack tip, commonly quantified by the J-integral concept. However, to date the experimental stress and strain fields necessary to quantify the J-integral associated with local crack propagation in its original integral form were inaccessible. Here, we present a multi-method nanoscale strain- and stress-mapping surrounding a growing crack tip in two identical miniaturized fracture specimens made from a nanocrystalline FeCrMnNiCo high-entropy alloy. The respective samples were tested in situ in a scanning electron microscope and a synchrotron X-ray nanodiffraction setup, with detailed analyzes of loading states during elastic loading, crack tip blunting and general yielding, corroborated by a detailed elastic-plastic finite element model. This complementary in situ methodology uniquely enabled a detailed quantification of the J-integral along different integration paths from experimental nanoscale stress and strain fields. We find that conventional linear-elastic and elastic-plastic models, typically used to interpret fracture phenomena, have limited applicability at micron to nanoscale distances from propagating cracks. This for the first time unravels a limit to the path-independence of the J-integral, which has significant implications in the development and assessment of modern damage-tolerant materials and microstructures.

The sustainability of vascular access for hemodialysis is limited by frequent interventions and the inability of synthetic grafts to self-heal. Tissue engineering offers a solution through biodegradable grafts that remodel into autologous tissue. Here we assess electrospun polycarbonate-bis urea (PC-BU) vascular scaffolds (6mm-inner-Ø), reinforced with 3D-printed polycaprolactone coils, in a goat model, and compared them to expanded polytetrafluoroethylene (ePTFE) controls. The tissue-engineered grafts were repeatedly cannulated starting two weeks after implantation and were evaluated using computed tomography and histological analyses. By 12 weeks, the PC-BU grafts remodel into autologous tissue while maintaining structural integrity, maintaining integrity without dilations, ruptures, or aneurysms. Cannulation does not interfere with scaffold degradation or neo-tissue formation. Although the patency rate is lower for the PC-BU grafts (50%) compared to ePTFE (100%), the engineered grafts exhibit a self-healing response not seen in ePTFE. These findings demonstrate the potential of PC-BU tissue-engineered grafts as healing, functional vascular access solutions for hemodialysis, supporting cannulation during tissue transformation.

Iron-based superconductors exhibit various magnetic and electronic phases that are highly sensitive to structural and chemical modifications. Elucidating the origins of these phases remains a central challenge. Here, using neutron and x-ray diffraction, we uncover a universal phase diagram that identifies disorder as a hidden tuning parameter governing these phase transitions. By analyzing nine hole-doped phase diagrams, we observe the emergence of a double-Q tetragonal magnetic phase in proximity to ideal FeAs₄ tetrahedral configurations, thereby demonstrating a strong link between bond-angle stabilization and magnetic transitions. Beyond stabilizing the double-Q phase, atomic disorder also influences charge doping and magnetic anisotropy. We further observe similar scaling behavior of the transition temperatures of the double-Q and the more prevalent orthorhombic single-Q magnetic phases, evidencing a unified origin of structural and magnetic properties linked to itinerant nesting instability. Our findings establish a comprehensive basis for understanding how chemical disorder, charge doping, and structural features collectively shape the magnetic and superconducting properties of iron-based superconductors.

A cell's ability to sense and respond to the mechanical properties of the extracellular matrix (ECM) is essential for maintaining tissue homeostasis, and its disruption contributes to diseases such as fibrosis, cardiovascular disorders, and cancer. Effective mechanical coupling between the plasma membrane, the underlying filamentous actin (F-actin) cytoskeleton, and integrin-based adhesion complexes (IACs) is required to link ECM mechanics to cell morphology, yet the underlying mechanisms remain incompletely understood. Here, we combine computational modeling and high-resolution imaging to show that integrin-ECM bonds determine F-actin cytoskeleton organization. On soft substrates, short-lived IACs bonds allow rapid actin retrograde flow and dense branching, restricting protrusion and limiting cell spreading. In contrast, stiff substrates or Mn²⁺-mediated integrin activation stabilize adhesions, promote filament alignment, and drive membrane protrusion for cell spreading. These cytoskeletal transitions arise from feedback between adhesion strength and the spatial positioning of the F-actin barbed ends relative to the leading-edge membrane. This positioning determines whether filaments polymerize into linear bundles or branch into dendritic networks, each generating distinct protrusive forces that regulate cell spreading. Collectively, our findings establish integrin-ECM bond stability as a key regulator of F-actin cytoskeleton organization and cell morphology.

Uranium dioxide (UO₂) is a complex material with significant relevance to nuclear energy, materials science, and fundamental research. Understanding its high-temperature behavior is crucial for developing new uranium-based materials and improving nuclear fuel efficiency in nuclear reactors. Here we study the evolution of uranium state during the oxidation of UO₂ in air at temperatures up to 550 °C using the in situ X-ray absorption spectroscopy in high energy resolution fluorescence detection mode at the U M₄ edge, combined with electronic structure calculations. Our data reveal a complex sequence of events occurring over minutes and hours at elevated temperatures, including changes in the electronic and local structure, 5 f electron occupancy, the formation of U cuboctahedral clusters, and the creation of U₄O₉ and U₃O₇ mixed U oxide phases. These findings highlight the fundamental role of clustering processes and pentavalent uranium in both the oxidation process and the stabilization of uranium materials.

The carnivorous Drosera species employ hair-like appendages called trichomes that secrete a deadly adhesive consisting of an acidic polysaccharide, sugars, organic acids, and water to capture prey insects. Here, we develop a sustainable alternative to chemical pesticides using hyaluronic acid in a sugar-based natural deep eutectic solvent to mimic the composition and trapping mechanism of the Drosera mucilage. We formulate trichome biomimetic adhesives that become sprayable with added water to lower their viscosity, which can then regain the required adhesiveness as water evaporates up to the equilibrium content. Using a custom indentation setup, we measure promising adhesion energies between 9.5-14.5 µJ over one week, along with the formation of elongated fibrils (>2.3 cm) for the best-performing sample. Additionally, the material shows no phytotoxicity for over two weeks and effectively immobilizes western flower thrips through multiple contact points with the material in Petri dish bioassays, highlighting its efficacy and trapping mechanism akin to natural trichomes.

Topological Insulators (TIs) present an interesting materials platform for nanoscale, high frequency devices because they support high mobility, low scattering electronic transport within confined surface states. However, a robust methodology to control the properties of surface plasmons in TIs has yet to be developed. Surface doping of TIs with molecules may provide tunable control of the two-dimensional plasmons in Bi₂Se₃, but exploration of such heterostructures is still at an early stage and usually confined to monolayers. We have grown heterostructures of Bi₂Se₃/C₆₀ with exceptional crystallinity. Electron energy loss spectroscopy (EELS) reveals significant hybridisation of π states at the interface, despite the expectation for only weak van der Waals interactions, including quenching of 2D plasmons. Momentum-resolved EELS measurements are used to probe the plasmon dispersion, with Density Functional Theory predictions providing an interpretation of results based on interfacial charge dipoles. This work provides growth methodology and characterization of highly crystalline TI/molecular interfaces that can be engineered for plasmonic applications in energy, communications and sensing.

Radiochromic crystals have many suitable features for dosimetry across a broad range of radiotherapy modalities, yet the study of these materials within the medical physics community has been limited. Here, we study three types of radiochromic pentacosa-10,12-diynoic acid-based formulations: two analogues of commercially available materials and one newly developed. Formulations coated on polyethylene are irradiated with photon (6 and 10 MV) and proton (74 MeV) beams (0-25 Gy) using custom fibre-optic setups that enable real-time transmission measurements at 1.5-2 cm depth to maintain dosimetric accuracy. The dose response to ionizing radiation is compared between the formulations and all formulations were characterized using a variety of analytical methods. The response of radiochromic crystals to ionizing radiation is complex and influenced by factors such as monomer composition and resulting macroscopic crystal morphology. By optimizing these parameters, it could be possible to develop dosimeters suitable for a variety of clinical applications.