Chemical short-range disorder in lithium oxide cathodes.

Ordered layered structures serve as essential components in lithium (Li)-ion cathodes1-3. However, on charging, the inherently delicate Li-deficient frameworks become vulnerable to lattice strain and structural and/or chemo-mechanical degradation, resulting in rapid capacity deterioration and thus short battery life2,4. Here we report an approach that addresses these issues using the integration of chemical short-range disorder (CSRD) into oxide cathodes, which involves the localized distribution of elements in a crystalline lattice over spatial dimensions, spanning a few nearest-neighbour spacings. This is guided by fundamental principles of structural chemistry and achieved through an improved ceramic synthesis process. To demonstrate its viability, we showcase how the introduction of CSRD substantially affects the crystal structure of layered Li cobalt oxide cathodes. This is manifested in the transition metal environment and its interactions with oxygen, effectively preventing detrimental sliding of crystal slabs and structural deterioration during Li removal. Meanwhile, it affects the electronic structure, leading to improved electronic conductivity. These attributes are highly beneficial for Li-ion storage capabilities, markedly improving cycle life and rate capability. Moreover, we find that CSRD can be introduced in additional layered oxide materials through improved chemical co-doping, further illustrating its potential to enhance structural and electrochemical stability. These findings open up new avenues for the design of oxide cathodes, offering insights into the effects of CSRD on the crystal and electronic structure of advanced functional materials.

High-Entropy Lithium Niobate Nanocubes for Photocatalytic Water Splitting under Visible Light.

The vast compositional space available in high-entropy oxide semiconductors offers unique opportunities for electronic band structure engineering in an unprecedented large room. In this work, with wide band gap semiconductor lithium niobate (LiNbO3) as a model system, we show that the substitutional addition of high-entropy metal cation mixtures within the Nb sublattice can lead to the formation of a single-phase solid solution featuring a substantially narrowed band gap and intense broadband visible light absorption. The resulting high-entropy LiNbO3 [denoted as Li(HE)O3] crystallizes as well-faceted nanocubes; atomic-resolution imaging and elemental mapping via transmission electron microscopy unveil a distinct local chemical complexity and lattice distortion, characteristics of high-entropy stabilized solid solution phases. Because of the presence of high-entropy stabilized Co2+ dopants that serve as active catalytic sites, Li(HE)O3 nanocubes can accomplish the visible light-driven photocatalytic water splitting in an aqueous solution containing methanol as a sacrificial electron donor without the need of any additional co-catalysts.

The mechanical, wear, antibacterial properties and biocompatibility of injectable restorative materials under wet challenge.

OBJECTIVES: To evaluate the mechanical, wear, antibacterial properties, and biocompatibility of injectable composite materials. METHODS: Two injectable composite resins (GU and BI), one flowable composite resin (FS), and one flowable compomer (DF), in A2 shade, were tested. Mechanical properties were tested via three-point bending test immediately after preparation and after 1-day, 7-day, 14-day, and 30-day water storage. Under water-PMMA slurry immersion, specimens were subjected to a 3-body wear test (10,000 cycles) against stainless steel balls, while the roughness, wear depth, and volume loss were recorded. After 1-day and 3-day MC3T3-E1 cell culture, cell viability was evaluated with CCK-8 test kits, while the cell morphology was observed under CLSM and SEM. Antibacterial properties on S. mutans were assessed via CFU counting, CLSM, and SEM observation. SPSS 26.0 was used for statistical analysis (α = 0.05). RESULTS: The mechanical properties were material-dependent and sensitive to water storage. Flexural strength ranked GU > FS > BI > DF at all testing levels. Three nanocomposites had better wear properties than DF. No significant difference on 1-day cell viability was found, but DF showed significantly lower cell proliferation than nanocomposites on 3-day assessment. GU and FS had more favourable cell adhesion and morphology. CFU counting revealed no significant difference, while FS presented a slightly thicker biofilm and BI showed relatively lower bacteria density. CONCLUSIONS: Injectable nanocomposites outperformed the compomer regarding mechanical properties, wear resistance, and biocompatibility. The tested materials presented comparable antibacterial behaviours. Flowable resin-based composites' performances are affected by multiple factors, and their compositions can be attributed. CLINICAL SIGNIFICANCE: A profound understanding of the mechanical, wear, and biological properties of the restorative material is imperative for the clinical success of dental restorations. The current study demonstrated superior properties of highly filled injectable composite resins, which imply their wider indications and better long-term clinical performances.

The chemical and optical stability evaluation of injectable restorative materials under wet challenge.

OBJECTIVES: To investigate and compare the chemical and optical stability of four restorative composite materials: two injectable resins, one flowable resin and one compomer. METHODS: Two injectable nano-filled composite resins: G-aenial Universal (GU) and Beautifil Injectable XSL (BI), a flowable composite resin: Filtek Supreme Flowable (FS) and a compomer: Dyract Flow (DF), in A2 shade were tested and compared. Water sorption and solubility were conducted according to ISO4049:2019 standard; ICP-OES and F-ion selective electrode were used to test the elemental release; Degree of conversion (DC) was obtained by using FTIR; water contact angle was obtained by static sessile drop method, and a spectrophotometer was used for optical properties (ΔE⁎, ΔL⁎ and TP). SPSS 28.0 was used for statistical analysis and the significant level was pre-set as α = 0.05. RESULTS: GU performed the best in water sorption and solubility, FS had the lowest elemental release, the best colour stability, and the highest DCIM and DC24-h. DF, the compomer had the lowest, and GU and BI, the injectable composites had the largest water contact angle, respectively. Correlations were found between water sorption and water solubility. CONCLUSIONS: The four composite restorative materials showed different chemical and optical behaviours. Overall, composite resins performed better than compomer, while additional laboratory and in vivo tests are necessary to obtain a more comprehensive comparison between injectable and flowable composite resins. Wsp and Wsl are influenced by many common factors, and the values are highly positively related. CLINICAL SIGNIFICANCE: A comprehensive understanding of materials is crucial before selecting materials for clinical practice. Composite resins rather than compomers are recommended because of their exceptional properties, which make them eligible for a wide range of clinical applications and an elongated lifespan.

Predominant P3-Type Solid-Solution Phase Transition Enables High-Stability O3-Type Na-Ion Cathodes.

Layered O3-type oxides are one of the most promising cathode materials for Na-ion batteries owing to their high capacity and straightforward synthesis. However, these materials often experience irreversible structure transitions at elevated cutoff voltages, resulting in compromised cycling stability and rate performance. To address such issues, understanding the interplay of the composition, structure, and properties is crucial. Here, we successfully introduced a P-type characteristic into the O3-type layered structure, achieving a P3-dominated solid-solution phase transition upon cycling. This modification facilitated a reversible transformation of the O3-P3-P3' structure with minimal and gradual volume changes. Consequently, the Na0.75Ni0.25Cu0.10Fe0.05Mn0.15Ti0.45O2 cathode exhibited a specific capacity of approximately 113 mAh/g, coupled with exceptional cycling performance (maintaining over 70% capacity retention after 900 cycles). These findings shed light on the composition-structure-property relationships of Na-ion layered oxides, offering valuable insights for the advancement of Na-ion batteries.

Bevel-edge epitaxy of ferroelectric rhombohedral boron nitride single crystal.

Within the family of two-dimensional dielectrics, rhombohedral boron nitride (rBN) is considerably promising owing to having not only the superior properties of hexagonal boron nitride1-4-including low permittivity and dissipation, strong electrical insulation, good chemical stability, high thermal conductivity and atomic flatness without dangling bonds-but also useful optical nonlinearity and interfacial ferroelectricity originating from the broken in-plane and out-of-plane centrosymmetry5-23. However, the preparation of large-sized single-crystal rBN layers remains a challenge24-26, owing to the requisite unprecedented growth controls to coordinate the lattice orientation of each layer and the sliding vector of every interface. Here we report a facile methodology using bevel-edge epitaxy to prepare centimetre-sized single-crystal rBN layers with exact interlayer ABC stacking on a vicinal nickel surface. We realized successful accurate fabrication over a single-crystal nickel substrate with bunched step edges of the terrace facet (100) at the bevel facet (110), which simultaneously guided the consistent boron-nitrogen bond orientation in each BN layer and the rhombohedral stacking of BN layers via nucleation near each bevel facet. The pure rhombohedral phase of the as-grown BN layers was verified, and consequently showed robust, homogeneous and switchable ferroelectricity with a high Curie temperature. Our work provides an effective route for accurate stacking-controlled growth of single-crystal two-dimensional layers and presents a foundation for applicable multifunctional devices based on stacked two-dimensional materials.

Evidence for multiferroicity in single-layer CuCrSe2.

Multiferroic materials, which simultaneously exhibit ferroelectricity and magnetism, have attracted substantial attention due to their fascinating physical properties and potential technological applications. With the trends towards device miniaturization, there is an increasing demand for the persistence of multiferroicity in single-layer materials at elevated temperatures. Here, we report high-temperature multiferroicity in single-layer CuCrSe2, which hosts room-temperature ferroelectricity and 120 K ferromagnetism. Notably, the ferromagnetic coupling in single-layer CuCrSe2 is enhanced by the ferroelectricity-induced orbital shift of Cr atoms, which is distinct from both types I and II multiferroicity. These findings are supported by a combination of second-harmonic generation, piezo-response force microscopy, scanning transmission electron microscopy, magnetic, and Hall measurements. Our research provides not only an exemplary platform for delving into intrinsic magnetoelectric interactions at the single-layer limit but also sheds light on potential development of electronic and spintronic devices utilizing two-dimensional multiferroics.

Superexchange-stabilized long-distance Cu sites in rock-salt-ordered double perovskite oxides for CO2 electromethanation.

Cu-oxide-based catalysts are promising for CO2 electroreduction (CO2RR) to CH4, but suffer from inevitable reduction (to metallic Cu) and uncontrollable structural collapse. Here we report Cu-based rock-salt-ordered double perovskite oxides with superexchange-stabilized long-distance Cu sites for efficient and stable CO2-to-CH4 conversion. For the proof-of-concept catalyst of Sr2CuWO6, its corner-linked CuO6 and WO6 octahedral motifs alternate in all three crystallographic dimensions, creating sufficiently long Cu-Cu distances (at least 5.4 Å) and introducing marked superexchange interaction mainly manifested by O-anion-mediated electron transfer (from Cu to W sites). In CO2RR, the Sr2CuWO6 exhibits significant improvements (up to 14.1 folds) in activity and selectivity for CH4, together with well boosted stability, relative to a physical-mixture counterpart of CuO/WO3. Moreover, the Sr2CuWO6 is the most effective Cu-based-perovskite catalyst for CO2 methanation, achieving a remarkable selectivity of 73.1% at 400 mA cm-2 for CH4. Our experiments and theoretical calculations highlight the long Cu-Cu distances promoting *CO hydrogenation and the superexchange interaction stabilizing Cu sites as responsible for the superb performance.

Designing lithium halide solid electrolytes.

All-solid-state lithium batteries have attracted widespread attention for next-generation energy storage, potentially providing enhanced safety and cycling stability. The performance of such batteries relies on solid electrolyte materials; hence many structures/phases are being investigated with increasing compositional complexity. Among the various solid electrolytes, lithium halides show promising ionic conductivity and cathode compatibility, however, there are no effective guidelines when moving toward complex compositions that go beyond ab-initio modeling. Here, we show that ionic potential, the ratio of charge number and ion radius, can effectively capture the key interactions within halide materials, making it possible to guide the design of the representative crystal structures. This is demonstrated by the preparation of a family of complex layered halides that combine an enhanced conductivity with a favorable isometric morphology, induced by the high configurational entropy. This work provides insights into the characteristics of complex halide phases and presents a methodology for designing solid materials.

Epitaxy of wafer-scale single-crystal MoS2 monolayer via buffer layer control.

Monolayer molybdenum disulfide (MoS2), an emergent two-dimensional (2D) semiconductor, holds great promise for transcending the fundamental limits of silicon electronics and continue the downscaling of field-effect transistors. To realize its full potential and high-end applications, controlled synthesis of wafer-scale monolayer MoS2 single crystals on general commercial substrates is highly desired yet challenging. Here, we demonstrate the successful epitaxial growth of 2-inch single-crystal MoS2 monolayers on industry-compatible substrates of c-plane sapphire by engineering the formation of a specific interfacial reconstructed layer through the S/MoO3 precursor ratio control. The unidirectional alignment and seamless stitching of MoS2 domains across the entire wafer are demonstrated through cross-dimensional characterizations ranging from atomic- to centimeter-scale. The epitaxial monolayer MoS2 single crystal shows good wafer-scale uniformity and state-of-the-art quality, as evidenced from the ~100% phonon circular dichroism, exciton valley polarization of ~70%, room-temperature mobility of ~140 cm2v-1s-1, and on/off ratio of ~109. Our work provides a simple strategy to produce wafer-scale single-crystal 2D semiconductors on commercial insulator substrates, paving the way towards the further extension of Moore's law and industrial applications of 2D electronic circuits.

Programmable Ferroelectricity in Hf0.5Zr0.5O2 Enabled by Oxygen Defect Engineering.

Ferroelectricity, especially the Si-compatible type recently observed in hafnia-based materials, is technologically useful for modern memory and logic applications, but it is challenging to differentiate intrinsic ferroelectric polarization from the polar phase and oxygen vacancy. Here, we report electrically controllable ferroelectricity in a Hf0.5Zr0.5O2-based heterostructure with Sr-doped LaMnO3, a mixed ionic-electronic conductor, as an electrode. Electrically reversible extraction and insertion of an oxygen vacancy into Hf0.5Zr0.5O2 are macroscopically characterized and atomically imaged in situ. Utilizing this reversible process, we achieved multilevel polarization states modulated by the electric field. Our study demonstrates the usefulness of the mixed conductor to repair, create, manipulate, and utilize advanced ferroelectric functionality. Furthermore, the programmed ferroelectric heterostructures with Si-compatible doped hafnia are desirable for the development of future ferroelectric electronics.

Enzymatically modified isoquercitrin and its protective effects against photoaging: In-vitro and clinical studies.

This research examines the anti-aging potential of the flavonoid derivative of isoquercitrin known as enzymatically modified isoquercitrin (EMIQ). Initial HPLC analyses showed that EMIQ used in the study contained 1-12 glucosides and 10.7% pentahydroxyflavonoids, promising potent antioxidant properties. In subsequent in-vitro studies with UVA-exposed human dermal fibroblasts (HDFa), EMIQ demonstrated protective properties by reducing collagen damage. It modulated both the TGFß/Smad pathway and the MMP1 pathway, contributing to collagen preservation. This protective effect was further confirmed using the T-Skin™ model, a reconstructed full-thickness human skin model, which illustrated that EMIQ could defend the physiological structures of both the epidermis and dermis against UV radiation. A 28-day clinical trial with 30 volunteers aged 31-55 years highlighted EMIQ's effectiveness. Participants using EMIQ-containing Essence displayed reduced facial trans-epidermal water loss and skin roughness, alongside improved skin elasticity. This study emphasizes EMIQ's potential as an anti-photoaging ingredient in cosmetics, warranting further research. The findings pave the way for developing innovative skincare products addressing photoaging effects.

Porphyromonas gingivalis can degrade dental zirconia.

OBJECTIVES: The aim of present study was to examine the effect of Porphyromonas gingivalis (P.g.) adhesion on dental zirconia by characterizing the physical and chemical properties. METHODS: Eighty polished-sintered zirconia discs were prepared and randomly distributed to 5 groups (n = 16): Zirconia cultured with - Group 1: broth containing P.g. for - 3 days; Group 2: 7 days; Group 3: broth (alone) for - 3 days; Group 4: 7 days; and Group 5: dry discs (negative control). After experimental period, broths were analyzed for pH and Zr release with inductively coupled plasma-optical emission spectroscopy (ICP-OES). The zirconia surface was evaluated by scanning electron microscope (SEM), atomic force microscopy (AFM), X-ray diffraction (XRD), water contact angle (WCA), and biaxial flexural strength (BFS). RESULTS: The mean pH with zirconia adhesion to P.g. group was significantly higher than the broth control (p < 0.05). As per ICP-OES, Zr ion/particulate release with P.g. adhesion to zirconia were significantly higher than the controls (p < 0.05). Post-experimental incubation, no defects were found on zirconia surfaces; tetragonal phase remained constant with no transformation to monoclinic phase but lower peak intensities were identified in experimental groups. WCA of zirconia surfaces with P.g. bacteria for 3 days (12.04° ± 2.05°) and 7 days (15.09° ± 2.95°) were significantly higher than zirconia surfaces immersed with broth (only) for 3 days (7.17° ± 1.09°) and 7 days (7.55° ± 0.65°), respectively (p < 0.05). BFS values of zirconia with P.g. for 3 days (632.57 ± 119.96 MPa) and 7 days (656.17 ± 100.29 MPa) were significantly lower than zirconia incubated in broth alone (765.01 ± 20.12 MPa) conditions (p < 0.05). SIGNIFICANCE: Under the conditions of present study, it can be concluded that P.g. adhesion on zirconia leads to structural alterations of dental zirconia further contributing to zirconia degradation.

Ferroelectricity in Epitaxial Perovskite Oxide Bi2WO6 Films with One-Unit-Cell Thickness.

Retaining ferroelectricity in ultrathin films or nanostructures is crucial for miniaturizing ferroelectric devices, but it is a challenging task due to intrinsic depolarization and size effects. In this study, we have shown that it is possible to stably maintain in-plane polarization in an extremely thin, one-unit-cell thick epitaxial Bi2WO6 film. The use of a perfectly lattice-matched NdGaO3 (110) substrate for the Bi2WO6 film minimizes strain and enhances stability. We attribute the residual polarization in this ultrathin film to the crystal stability of the Bi-O octahedral framework against structural distortions. Our findings suggest that ferroelectricity can surpass the critical thickness limit through proper strain engineering, and the Bi2WO6/NdGaO3 (110) system presents a potential platform for designing low-energy consumption, nonvolatile ferroelectric memories.

Comparative finite element analysis of posterior short segment fixation constructs with or without intermediate screws in the fractured vertebrae for the treatment of type a thoracolumbar fracture.

Six-screw short-segment posterior fixation for thoracolumbar fractures, which involves intermediate screws at the fractured vertebrae has been proposed to reduce the rates of kyphosis recurrence and implant failure. Yet, little is known about the mechanisms and biomechanical responses by which intermediate screws at the fracture vertebrae enhance fixation strength. The objective of this study was to investigate the biomechanical properties that are associated with the augmentation of intermediate screws in relation to the severity of type A thoracolumbar fracture using finite element analysis. Short-segment stabilization models with or without augmentation screws at fractured vertebrae were established based on finite element model of moderate compressive fractures, severe compressive fractures and burst fractures. The spinal stiffness, stresses at the implanted hardware, and axial displacement of the bony defect were measured and compared under mechanical loading conditions. All six-screw stabilization showed a decreased range of motion in extension, lateral bending, and axial rotation compared to the traditional four-screw fixation models. Burst thoracolumbar fracture benefited more from augmentation of intermediate screws at the fracture vertebrae. The stress of the rod in six-screw models increased while decreased that of pedicle screws. Our results suggested that patients with more unstable fractures might achieve greater benefits from augmentation of intermediate screws at the fracture vertebrae. Augmentation of intermediate screws at the fracture vertebrae is recommended for patients with higher wedge-shaped or burst fractures to reduce the risk of hardware failure and postoperative re-collapse of injured vertebrae.

Low power flexible monolayer MoS2 integrated circuits.

Monolayer molybdenum disulfide (ML-MoS2) is an emergent two-dimensional (2D) semiconductor holding potential for flexible integrated circuits (ICs). The most important demands for the application of such ML-MoS2 ICs are low power consumption and high performance. However, these are currently challenging to satisfy due to limitations in the material quality and device fabrication technology. In this work, we develop an ultra-thin high-κ dielectric/metal gate fabrication technique for the realization of thin film transistors based on high-quality wafer scale ML-MoS2 on both rigid and flexible substrates. The rigid devices can be operated in the deep-subthreshold regime with low power consumption and show negligible hysteresis, sharp subthreshold slope, high current density, and ultra-low leakage currents. Moreover, we realize fully functional large-scale flexible ICs operating at voltages below 1 V. Our process could represent a key step towards using energy-efficient flexible ML-MoS2 ICs in portable, wearable, and implantable electronics.

Scaling of MoS2 Transistors and Inverters to Sub-10 nm Channel Length with High Performance.

Two-dimensional (2D) semiconductors such as monolayer molybdenum disulfide (MoS2) are promising building blocks for ultrascaled field effect transistors (FETs), benefiting from their atomic thickness, dangling-bond-free flat surface, and excellent gate controllability. However, despite great prospects, the fabrication of 2D ultrashort channel FETs with high performance and uniformity remains a challenge. Here, we report a self-encapsulated heterostructure undercut technique for the fabrication of sub-10 nm channel length MoS2 FETs. The fabricated 9 nm channel MoS2 FETs exhibit superior performances compared with sub-15 nm channel length including the competitive on-state current density of 734/433 µA/µm at VDS = 2/1 V, record-low DIBL of ∼50 mV/V, and superior on/off ratio of 3 × 107 and low subthreshold swing of ∼100 mV/dec. Furthermore, the ultrashort channel MoS2 FETs fabricated by this new technique show excellent homogeneity. Thanks to this, we scale the monolayer inverter down to sub-10 nm channel length.

Magnetoelectric coupling in multiferroics probed by optical second harmonic generation.

Magnetoelectric coupling, as a fundamental physical nature and with the potential to add functionality to devices while also reducing energy consumption, has been challenging to be probed in freestanding membranes or two-dimensional materials due to their instability and fragility. In this paper, we report a magnetoelectric coupling probed by optical second harmonic generation with external magnetic field, and show the manipulation of the ferroelectric and antiferromagnetic orders by the magnetic and thermal fields in BiFeO3 films epitaxially grown on the substrates and in the freestanding ones. Here we define an optical magnetoelectric-coupling constant, denoting the ability of controlling light-induced nonlinear polarization by the magnetic field, and found the magnetoelectric-coupling was suppressed by strain releasing but remain robust against thermal fluctuation for freestanding BiFeO3.

Dynamic Observation of the Coulomb Explosion and Field Evaporation of a Few-Layer Graphene Nanoribbon.

The Coulomb explosion and field evaporation are frequently observed physical phenomena for a metallic tip under an external electric field, which can modify the structures of the tip and have broad applications, such as in the atomic-probe tomography and field ion microscopy. However, the mechanistic comprehending of how they change the structures of the tip and the differences between them are not clear. Here, dynamic observations of Coulomb explosions and field evaporations on the positively biased and charged few-layer graphene (FLG) nanoribbon inside a transmission electron microscope are reported. By combining the atomic-scale molecular dynamic simulations, it is shown that the FLG is split into several sheets under Coulomb explosion. It is also observed to break by emitting the carbon ions/segments under the field evaporation. It is further demonstrated that the split and breaking of FLG can be tuned by the shape of the nanoribbon. FLG ribbons with sharp tips have splitting and breaking occur in sequence. FLG with blunt tips break without a split. These results provide a fundamental understanding of Coulomb explosion and field evaporation in graphene nanomaterials and suggest potential methods to engineer graphene-based nanostructures.

Disorder-tuned conductivity in amorphous monolayer carbon.

Correlating atomic configurations-specifically, degree of disorder (DOD)-of an amorphous solid with properties is a long-standing riddle in materials science and condensed matter physics, owing to difficulties in determining precise atomic positions in 3D structures1-5. To this end, 2D systems provide insight to the puzzle by allowing straightforward imaging of all atoms6,7. Direct imaging of amorphous monolayer carbon (AMC) grown by laser-assisted depositions has resolved atomic configurations, supporting the modern crystallite view of vitreous solids over random network theory8. Nevertheless, a causal link between atomic-scale structures and macroscopic properties remains elusive. Here we report facile tuning of DOD and electrical conductivity in AMC films by varying growth temperatures. Specifically, the pyrolysis threshold temperature is the key to growing variable-range-hopping conductive AMC with medium-range order (MRO), whereas increasing the temperature by 25 °C results in AMC losing MRO and becoming electrically insulating, with an increase in sheet resistance of 109 times. Beyond visualizing highly distorted nanocrystallites embedded in a continuous random network, atomic-resolution electron microscopy shows the absence/presence of MRO and temperature-dependent densities of nanocrystallites, two order parameters proposed to fully describe DOD. Numerical calculations establish the conductivity diagram as a function of these two parameters, directly linking microstructures to electrical properties. Our work represents an important step towards understanding the structure-property relationship of amorphous materials at the fundamental level and paves the way to electronic devices using 2D amorphous materials.