Materials Horizons最新文献

Upper gastrointestinal bleeding (UGIB) is bleeding in the upper part of the gastrointestinal tract with an acidic and dynamic environment that limits the application of conventional hemostatic materials. This study focuses on the development of N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride/phytic acid (HTCC/PA, HP) powders with fast hemostatic capability and strong acid resistance, for potential applications in managing UGIB. Upon contact with liquids within 5 seconds, HP powders rapidly transform into hydrogels, forming ionic networks through electrostatic interactions. The ionic crosslinking process facilitates the HP powders with high blood absorption (3.4 times of self-weight), sufficient tissue adhesion (5.2 and 6.1 kPa on porcine skin and stomach, respectively), and hemostasis (within 15 seconds for in vitro clotting). Interestingly, the PA imparts the HP powders with strong acid resistance (69.8% mass remaining after 10 days of incubation at pH 1) and on-demand removable sealing while HTCC contributes to fast hemostasis and good wet adhesion. Moreover, the HP powders show good biocompatibility and promote wound healing. Therefore, these characteristics highlight the promising clinical potential of HP powders for effectively managing UGIB.

Upconversion circularly polarized luminescence (UC-CPL) exhibits promising potential for application for anti-counterfeiting and displays. Upconversion nanoparticles (UCNPs), NaYF₄:Yb,Tm, with uniform morphology and high crystallinity, were prepared via a simple solvothermal method. These UCNPs were embedded into cholesteric liquid crystal polymer network (CLCN) films. The UC-CPL performance of these films was investigated using left- and right-handed circular polarizers. After calibration, the |gcallum| values (up to 0.33) were obtained for the free-standing CLCN-UCNPs films, while a |gcallum| value of 0.43 was achieved for the CLCN-UCNPs-coated PET film. Moreover, a combined system comprising a PMMA-UCNPs layer and a CLCN layer yielded an ultra-large |gcallum| value of up to 1.73. Flexible and colourful patterned CLCN films were fabricated using photomasks, offering potential applications in anti-counterfeiting. This study not only successfully prepared UC-CPL-active materials based on CLCNs and UCNPs, but also demonstrated the chiral filtering effect of CLCN films in upconversion luminescent materials.

The development of flexible electronics has increased the demand for wearable pressure sensors that can be used to monitor various biomedical signals. In this context, pressure sensors based on zinc oxide (ZnO) have great potential since, besides the biocompatibility and biodegradability of this metal oxide, it also has piezoelectric properties. The common feature of these sensors is the alignment of the ZnO nanostructures in the strain direction. This alignment is achieved through a three-stage procedure: deposition of a ZnO nanoparticle layer (seed layer) followed by its patterning and the subsequent growth of nanostructures from the seed layer nanoparticles. Herein, a process compatible with industrial scale for depositing seed layers by flexographic printing is proposed, allowing seed layers to be deposited and patterned swiftly and efficiently in a single step on flexible indium tin oxide coated polyethylene terephthalate substrates, significantly decreasing the time and cost required to produce pressure sensors. The growth conditions of ZnO nanorods on these substrates were also studied to analyze their influence on the morphological and structural characteristics of the nanostructures. Nanorods with length of (0.27 ± 0.04) μm and density of (296 ± 6) nanorods per μm² were obtained in microwave-assisted hydrothermal syntheses carried out at 100 °C for 30 min, with a 1 M zinc acetate seed layer and using an equimolar growth solution of zinc nitrate and hexamethylenetetramine. These conditions were used to produce ZnO-based pressure sensors with two patterns (one square and 16 individual squares). Although the single square sensors displayed a higher average output voltage ((12 ± 5) V for an impact pressure of 150 kPa), their response was considerably more variable than the patterned sensors (with 16 squares), which displayed an average output voltage of (8 ± 2) V under an applied pressure of 150 kPa and sensitivity values of (0.06 ± 0.01) V kPa^-1, demonstrating their potential for wearables and portable electronics.

To alleviate the shuttle effect in lithium-sulfur (Li-S) batteries, the electrocatalytic conversion of polysulfides serves as a vital strategy. However, achieving a synergy that combines robust adsorption with high catalytic activity continues to pose significant challenges. Herein, a simple solid-state sintering method is employed to transform vanadium-niobium carbide MXene (VNbCT_x) into a heterogeneous structure of V₅S₈-Nb₂O₅@VNbCT_x MXene (denoted as V₅S₈-Nb₂O₅@MX). The Nb₂O₅ component immobilizes lithium polysulfides (LiPSs) at the electrode through its strong chemical affinity, while the V₅S₈ fraction serves as an outstanding electrochemical catalyst, enhancing the reaction kinetics of sulfur precipitation. Furthermore, the VNbCT_x MXene precursor scaffold is preserved through the conversion and uniformly distributed throughout the composite, exhibiting excellent electrical conductivity. Thanks to the synergistic "capture-adsorption-catalysis" action on LiPSs, the V₅S₈-Nb₂O₅@MX composite effectively restrains the shuttle effect. The as-prepared Li-S battery demonstrates a significant increase in specific capacity, reaching 1508 mA h g^-1 at 0.1C and maintaining a capacity decay of approximately 0.027% per cycle after 500 cycles at 1C and 766.1 mA h g^-1 at 5C. Even under a high sulfur loading of 5.75 mg cm^-2, the battery can maintain a specific capacity of 596.6 mA h g^-1 and exhibit significant cycling stability after 100 cycles. DFT calculations indicate that the V₅S₈-Nb₂O₅@MX heterostructure exhibits a higher binding energy of 5.34 eV and a lower decomposition barrier energy of 0.68 eV, presenting potential advantages in accelerating the conversion reactions of LiPSs. Our research offers a straightforward approach for designing metal oxide-sulfide heterostructured catalysts that deliver superior performance and enhance the electrocatalytic conversion of LiPSs, clearing the path for high performance Li-S batteries.

Investigation of brain neural circuits is essential for deciphering the diagnostics and therapeutics of neurodegenerative diseases. The main concerns with traditional rigid metal electrodes include intrinsic mechanical mismatch between sensing electrodes and tissues, unavoidable foreign body responses, and inadequate spatiotemporal resolution, resulting in a deficiency of sensing performance. All-hydrogel neural electrodes with multi-electrode arrays (MEAs) suggest a viable way to modulate the trade-off between tissue-mechanical compliance and excellent spatiotemporal recording capacity, but still face the issues of insufficient conductivity and unstable interlayer bonding. Herein, we constructed a four-layer all-hydrogel neural electrode, by sandwiching a conductive hydrogel layer within two encapsulation hydrogel layers, with a shielding hydrogel layer located on top. We introduce a dual-strategy treatment to induce controllable phase separation in poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hydrogel, which achieved ultra-high conductivity (up to 4176 S cm^-1) comparable to that of metals and precise spatial resolution (∼15 μm) suitable for single neuron recording. In addition, the utilization of polyphenol chemistry mediated adaptive adhesion endowed this neural electrode with flexible and stable interlayer bonding among conductive-encapsulation-shielding layers and the tissue-electrode interface. Consequently, the all-hydrogel neural electrode exhibited a tenfold higher signal-to-noise ratio than a commercial silver electrode, realized the recording of weak neural activity signals within single and multiple neurons in epileptic rats, and applied man-made stimulation to the cerebral cortex of rats during seizures. This work provides a useful tool to understand the development, function and treatment of neurodegenerative diseases.

Noncentrosymmetric (NCS) compounds are particularly important for modern optoelectronic technology, yet their rational structural design remains a great challenge. Herein, assisted by the idea of bottom-up reticular chemistry, seven new NCS selenites, AM₃[SeO₃]₂[Se₂O₅]₃ (A = K⁺/Rb⁺/Cs⁺; M = Al³⁺/Ga³⁺/In³⁺), have been successfully designed and synthesized by assembling main-group metal octahedral units and SeO₃ units, to construct honeycomb layers with regular channels to accommodate a variety of cations, and using planar hexagonal shapes to orientate the groups within the network. Based on this strategy, the overall symmetry of the solid-state compounds was effectively controlled, and by modifying locally connected atoms or groups, without disrupting the overall prototypical framework, a series of iso-reticular analogues have been obtained, which greatly increases the probability of NCS structures. Three of these compounds, CsM₃[SeO₃]₂[Se₂O₅]₃ were characterized experimentally and theoretically. The results show that they all have moderate second harmonic generation (SHG) responses, which are as large as that of commercial KH₂PO₄, and wide band gaps. Our study confirms the feasibility of reticular chemistry-assisted strategy in designing nonlinear optical materials with stable frameworks and good performance.

Light-based processing of thermosets has gained increasing attention because of its broad application field including its use in digital light processing (DLP) 3D printing. This technique offers efficient design and fabrication of complex structures but typically results in non-recyclable thermoset-based products. To address this issue, we describe here a photocurable, dynamic β-amino ester (BAE) based cross-linker that is not only suitable for DLP printing but can also be chemically degraded via transesterification upon the addition of 2-hydroxyethyl methacrylate (HEMA) as a decross-linker. This conceptually new protocol allows for efficient depolymerization with the direct restoration of curable monomers in a single step without the addition of external catalysts or solvents. By implementing this protocol, we have established a chemical recycling loop for multiple cycles of photo-cross-linking and restoration of cross-linkers, facilitating repeatable DLP 3D printing without generating any waste. The recycled materials exhibit full recovery of thermal properties and Young's modulus while maintaining 75% of their tensile strength for at least three cycles. Simultaneously, the presence of BAE moieties enables the (re)processability of these materials through compression molding.

Self-assembled lamellar nano- and microfilaments formed by select types of bent-core molecules are prime examples of the interplay between molecular conformation and morphological chirality. Here, we demonstrate how the strategic placement of chiral centers at C-1 and/or C-3 in the terminal alkyloxy side chains, largely based on a priori calculations of molecular conformation, leads to the predictable formation of increasingly complex nano- and microfilament morphologies. Adding to the previously described diversity of twisted and writhed filament types, we here demonstrate and explain the formation and coexistence of flat nanoribbons, nanocylinders, or nano- as well as microfilaments where the morphology spontaneously changes along the filament long axis. For some these more exotic types of filament morphology, helical multilayer filaments suddenly unwind to form flat nanoribbons that also twist again under preservation (not perversion) of the helical twist sense. Moreover, the morphologies formed by this series of molecules now allows us to demonstrate the complete transformation from flat multilayer ribbons over microfilaments and helical-wrapped nanocylinders to helical nanofilaments depending on the number and position of chiral centers in the aliphatic side chains.

CrI₃ offers an intriguing platform for exploring fundamental physics and the innovative design of spintronics devices in two-dimensional (2D) magnets, and moreover has been instrumental in the study of topological physics. However, the 2D CrI₃ monolayer and bilayers have long been thought to be topologically trivial. Here we uncover a hidden facet of the band topology of 2D CrI₃ by showing that both the CrI₃ monolayer and bilayers are second-order topological insulators (SOTIs) with a nonzero second Stiefel-Whitney number w₂ = 1. Furthermore, the topologically nontrivial nature can be explicitly confirmed via the emergence of floating edge states and in-gap corner states. Remarkably, in contrast to most known magnetic topological states, we put forward that the SOTIs in 2D CrI₃ monolayer and bilayers are highly robust against magnetic transitions, which remain intact under both ferromagnetic and antiferromagnetic configurations. These interesting predictions not only provide a comprehensive understanding of the band topology of 2D CrI₃ but also offer a favorable platform to realize magnetic SOTIs for spintronics applications.

Cr³⁺-activated garnet phosphors with broadband near-infrared (NIR) emission have attracted considerable interest due to their high quantum efficiency (QE) and thermal stability for widespread advanced applications. Nevertheless, how to achieve energy-saving broadband NIR phosphors that possess anti-thermal quenching (anti-TQ) without compromising the high QE has yet to be fully addressed. Herein, we report on site reconstruction within the garnet lattice by strategically positioning Sc and Ga atoms into octahedral B sites with a mole ratio of 1 : 1 to produce Gd₃ScGa₄O₁₂. A reduction in crystal field strength (CFS) is thus induced, leading to a redshift of Cr³⁺ broadband NIR emission. The inherent rigidity of the structure and the weak electron-phonon coupling (EPC) effect lay the groundwork for a thermally robust broadband NIR phosphor. The combination of bandgap engineering, finely optimizing the ⁴T₂ excited state population, and precise control over the doping concentration contributes a high-performance broadband NIR emission (IQE = 82.75%) with unprecedented anti-TQ such that the NIR emission of Cr³⁺ even increases to 198% of its room-temperature intensity at 543 K. A prototype broadband NIR pc-LED is encapsulated to deliver an NIR output power of 125.20 mW@900 mA and a wall-plug efficiency (WPE) of 6.88%@30 mA, enabling night vision, noninvasive imaging, and non-destructive detection applications.