Realizing altermagnetism in two-dimensional metal-organic framework semiconductors with electric-field-controlled anisotropic spin current.

Altermagnets exhibit momentum-dependent spin-splitting in a collinear antiferromagnetic order due to their peculiar crystallographic and magnetic symmetry, resulting in the creation of spin currents with light elements. Here, we report two two-dimensional (2D) metal-organic framework (MOF) semiconductors, M(pyz)2 (M = Ca and Sr, pyz = pyrazine), which exhibit both altermagnetism and topological nodal point and line by using first-principles calculations and group theory. The altermagnetic 2D MOFs exhibit unconventional spin-splitting and macroscopic zero magnetization caused by 4-fold rotation in crystalline real space and 2-fold rotation in spin space, leading to the generation and control of anisotropic spin currents when an in-plane electric field ( E ) is applied. In particular, pure spin current with the spin Hall effect occurs when E is applied along the angular bisector of the two spin arrangements. Our work indicates the existence of altermagnetic MOF systems and a universal approach to generate electric-field-controlled spin currents for potential applications in antiferromagnetic spintronics.

Solid-State Electrocatalysis in Heteroatom-Doped Alloy Anode Enables Ultrafast Charge Lithium-Ion Batteries.

Electrocatalysis is generally confined to dynamic liquid-solid and gas-solid interfaces and is rarely applicable in solid-state reactions. Here, we report a paradigm shift strategy to exploit electrocatalysis to accelerate solid-state reactions in the context of lithium-ion batteries (LIBs). We employ heteroatom doping, specifically boron for silicon and sulfur for phosphorus, to catalyze electrochemical Li-alloying reactions in solid-state electrode materials. The preferential cleavage of polar dopant-host chemical bonds upon lithiation triggers chemical bond breaking of the host material. This solid-state catalysis, distinct from liquid and gas phases, requires a critical doping concentration for optimal performance. Beyond a critical concentration of ∼1 atom %, boron and sulfur doping drastically reduces activation energies and accelerates redox kinetics during lithiation/delithiation processes, leading to markedly enhanced rate performance in boron-doped silicon and sulfur-doped black/red phosphorus anode. Notably, a sulfur-doped black phosphorus anode coupled with a lithium cobalt oxide cathode achieves an ultrafast-charging battery, recharging 80% energy of a battery in 302 Wh kg-1 in 9 min, surpassing the thus far reported LIBs.

Interfacial Charge-Transfer Excitonic Insulator in a Two-Dimensional Organic-Inorganic Superlattice.

Excitonic insulators are long-sought-after quantum materials predicted to spontaneously open a gap by the Bose condensation of bound electron-hole pairs, namely, excitons, in their ground state. Since the theoretical conjecture, extensive efforts have been devoted to pursuing excitonic insulator platforms for exploring macroscopic quantum phenomena in real materials. Reliable evidence of excitonic character has been obtained in layered chalcogenides as promising candidates. However, owing to the interference of intrinsic lattice instabilities, it is still debatable whether those features, such as the charge density wave and gap opening, are primarily driven by the excitonic effect or by the lattice transition. Herein, we develop an intercalation chemistry strategy for obtaining a novel charge-transfer excitonic insulator in organic-inorganic superlattice interfaces that serves as an ideal platform to decouple the excitonic effect from the lattice effect. In this system, we observe a narrow excitonic gap, formation of a charge density wave without periodic lattice distortion, and metal-insulator transition, providing visualized evidence of exciton condensation occurring in thermal equilibrium. Our findings identify self-assembly intercalation chemistry as a new strategy for developing novel excitonic insulators.

Reticular Ratchets for Directing Electrochemiluminescence.

Electrochemiluminescence (ECL) involves charge transfer between electrochemical redox intermediates to produce an excited state for light emission. Ensuring precise control of charge transfer is essential for decoding ECL fundamentals, yet guidelines on how to achieve this for conventional emitters remain unexplored. Molecular ratchets offer a potential solution, as they enable the directional transfer of energy or chemicals while impeding the reverse movement. Herein, we designed 10 pairs of imine-based covalent organic frameworks as reticular ratchets to delicately manipulate the intrareticular charge transfer for directing ECL transduction from electric and chemical energies. Aligning the donor and acceptor (D-A) directions with the imine dipole effectively facilitates charge migration, whereas reversing the D-A direction impedes it. Notably, the ratchet effect of charge transfer directionality intensified with increasing D-A contrast, resulting in a remarkable 680-fold improvement in the ECL efficiency. Furthermore, dipole-controlled exciton binding energy, electron/hole decay kinetics, and femtosecond transient absorption spectra identified the electron transfer tendency from the N-end toward the C-end of reticular ratchets during ECL transduction. An exponential correlation between the ECL efficiency and the dipole difference was discovered. Our work provides a general approach to manipulate charge transfer and design next-generation electrochemical devices.

Asymmetric Potential Model of Two-Dimensional Imine Covalent Organic Frameworks with Enhanced Quantum Efficiency for Photocatalytic Water Splitting.

Two-dimensional (2D) covalent organic frameworks (COFs) assembled using building blocks have been widely employed in photocatalysis due to their customizable optoelectronic characteristics and porous structure, which facilitate charge carrier and mass movement. Nevertheless, the development of COF photocatalysts encounters a continuous obstacle in enhancing the efficiency of photocatalysis, impeded by a limited comprehension of the orbital interaction between molecular fragments and linkers. In this study, we present a model that examines the interaction between molecular fragments in an imine-based COF at the frontier molecular orbital level, enabling us to comprehend the impact of manipulating linkers on light adsorption, exciton efficiency, and catalytic activity. Our findings demonstrate that altering the connecting orientation of 14 R-C=N-R imine linkers in 2D COFs can enhance solar-to-hydrogen (STH) efficiency under visible light from 2.76% to 4.24%. This research has the potential to provide a valuable model for refining photocatalysts with enhanced photocatalytic performance.

A Volcano Correlation between Catalytic Activity for Sulfur Reduction Reaction and Fe Atom Count in Metal Center.

Sulfur reduction reaction (SRR) facilitates up to 16 electrons, which endows lithium-sulfur (Li-S) batteries with a high energy density that is twice that of typical Li-ion batteries. However, its sluggish reaction kinetics render batteries with only a low capacity and cycling life, thus remaining the main challenge to practical Li-S batteries, which require efficient electrocatalysts of balanced atom utilization and site-specific requirements toward highly efficient SRR, calling for an in-depth understanding of the atomic structural sensitivity for the catalytic active sites. Herein, we manipulated the number of Fe atoms in iron assemblies, ranging from single Fe atom to diatomic and triatomic Fe atom groupings, all embedded within a carbon matrix. This led to the revelation of a "volcano peak" correlation between SRR catalytic activity and the count of Fe atoms at the active sites. Utilizing operando X-ray absorption and X-ray diffraction spectroscopies, we observed that polysulfide adsorption-desorption and electrochemical conversion kinetics varied up and down with the incremental addition of even a single iron atom to the catalyst's metal center. Our results demonstrate that the metal center with exactly two iron atoms represents the optimal configuration, maximizing atom utility and adeptly handling the conversion of varied intermediate sulfur species, rendering the Li-S battery with a high areal capacity of 23.8 mAh cm-2 at a high sulfur loading of 21.8 mg cm-2. Our results illuminate the pivotal balance between atom utilization and site-specific requirements for optimal electrocatalytic performance in SRR and diverse electrocatalytic reactions.

High-Throughput Screening of Sulfur Reduction Reaction Catalysts Utilizing Electronic Fingerprint Similarity.

The catalytic performance is determined by the electronic structure near the Fermi level. This study presents an effective and simple screening descriptor, i.e., the one-dimensional density of states (1D-DOS) fingerprint similarity, to identify potential catalysts for the sulfur reduction reaction (SRR) in lithium-sulfur batteries. The Δ1D-DOS in relation to the benchmark W2CS2 was calculated. This method effectively distinguishes and identifies 30 potential candidates for the SRR from 420 types of MXenes. Further analysis of the Gibbs free energy profiles reveals that MXene candidates exhibit promising thermodynamic properties for SRR, with the protocol achieving an accuracy rate exceeding 93%. Based on the crystal orbital Hamilton population (COHP) and differential charge analysis, it is confirmed that the Δ1D-DOS could effectively differentiate the interaction between MXenes and lithium polysulfide (LiPS) intermediates. This study underscores the importance of the electronic fingerprint in catalytic performance and thus may pave a new way for future high-throughput material screening for energy storage applications.

Metal-Sulfur Interfaces as the Primary Active Sites for Catalytic Hydrogenations.

The determination of catalytically active sites is crucial for understanding the catalytic mechanism and providing guidelines for the design of more efficient catalysts. However, the complex structure of supported metal nanocatalysts (e.g., support, metal surface, and metal-support interface) still presents a big challenge. In particular, many studies have demonstrated that metal-support interfaces could also act as the primary active sites in catalytic reactions, which is well elucidated in oxide-supported metal nanocatalysts but is rarely reported in carbon-supported metal nanocatalysts. Here, we fill the above gap and demonstrate that metal-sulfur interfaces in sulfur-doped carbon-supported metal nanocatalysts are the primary active sites for several catalytic hydrogenation reactions. A series of metal nanocatalysts with similar sizes but different amounts of metal-sulfur interfaces were first constructed and characterized. Taking Ir for quinoline hydrogenation as an example, it was found that their catalytic activities were proportional to the amount of the Ir-S interface. Further experiments and density functional theory (DFT) calculations suggested that the adsorption and activation of quinoline occurred on the Ir atoms at the Ir-S interface. Similar phenomena were found in p-chloronitrobenzene hydrogenation over the Pt-S interface and benzoic acid hydrogenation over the Ru-S interface. All of these findings verify the predominant activity of metal-sulfur interfaces for catalytic hydrogenation reactions and contribute to the comprehensive understanding of metal-support interfaces in supported nanocatalysts.

Electrocatalytic Mechanism and Sabatier Principle in C2N-Supported Atomically Dispersed Catalysts for the Sulfur Reduction Reaction in Lithium-Sulfur Batteries.

The sluggish kinetics of the sulfur reduction reaction (SRR) impedes the practical application of lithium-sulfur batteries (LSBs). Electrocatalysts are necessary to expedite the conversion of polysulfides. Here, we systematically investigate the chemical mechanisms and size dependence of catalytic activities toward the SRR from Li2S4 to Li2S on single-, double-, and triple-atom catalysts supported on C2N (Mn@C2N, where M is a 3d transitional metal and n = 1-3) as model systems by using first-principles calculations and a comprehensive electrocatalytic model. Our results reveal that the adsorption strength of the LiS• intermediate is identified as an optimal descriptor for catalytic activity. M1@C2N exhibits superior stability and exceptional activity compared to those of the other two catalyst types. Cu1@C2N exhibits the lowest overpotential of 0.426 V. Li embedding or a prelithiation strategy verifies the therein Sabatier principle. This work emphasizes the precise control of the active site structure and microenvironment in catalytic SRR and offers guidance for the design of electrocatalysts for metal-sulfur batteries.

Highly Crystalline Iridium-Nickel Nanocages with Subnanopores for Acidic Bifunctional Water Splitting Electrolysis.

Developing efficient bifunctional materials is highly desirable for overall proton membrane water splitting. However, the design of iridium materials with high overall acidic water splitting activity and durability, as well as an in-depth understanding of the catalytic mechanism, is challenging. Herein, we successfully developed subnanoporous Ir3Ni ultrathin nanocages with high crystallinity as bifunctional materials for acidic water splitting. The subnanoporous shell enables Ir3Ni NCs optimized exposure of active sites. Importantly, the nickel incorporation contributes to the favorable thermodynamics of the electrocatalysis of the OER after surface reconstruction and optimized hydrogen adsorption free energy in HER electrocatalysis, which induce enhanced intrinsic activity of the acidic oxygen evolution reaction (OER) and hydrogen evolution reaction (HER). Together, the Ir3Ni nanocages achieve 3.72 A/mgIr(η=350 mV) and 4.47 A/mgIr(η=40 mV) OER and HER mass activity, which are 18.8 times and 3.3 times higher than that of commercial IrO2 and Pt, respectively. In addition, their highly crystalline identity ensures a robust nanostructure, enabling good catalytic durability during the oxygen evolution reaction after surface oxidation. This work provides a new revenue toward the structural design and insightful understanding of metal alloy catalytic mechanisms for the bifunctional acidic water splitting electrocatalysis.

First-principles calculations of inorganic metallocene nanowires.

Inspired by the recently synthesized inorganic metallocene derivatives Fe(P4)22-, we have identified four stable inorganic metallocene nanowires, MP4 (M = Sc, Ti, Cr and Fe) in configurations of either regular quadrangular prism (Q-type) or anticube (A-type), and further investigated their magnetic and electronic characteristics utilizing the first-principles calculation. It shows that CrP4 is a ferromagnetic metal, while other nanowires are semiconducting antiferromagnets with bandgaps of 0.44, 1.88, and 2.29 eV within the HSE06 level. It also shows that both ScP4 and TiP4 can be stabilized in the Q-type and A-type, corresponding to the antiferromagnetic and ferromagnetic ground states, respectively, indicating a configuration-dependent magnetism. The thermodynamic and lattice stabilities are confirmed by the ab initio molecular dynamics and phonon spectra. This study has unmasked the structural and physical properties of novel inorganic metallocene nanowires, and revealed their potential application in spintronics.

Interlayer Biatomic Pair Bridging the van der Waals Gap for 100% Activation of 2D Layered Material.

2D layered materials are regarded as prospective catalyst candidates due to their advantageous atomic exposure ratio. Nevertheless, the predominant population of atoms residing on the basal plane with saturated coordination, exhibit inert behavior, while a mere fraction of atoms located at the periphery display reactivity. Here, a novel approach is reported to attain complete atom activation in 2D layered materials through the construction of an interlayer biatomic pair bridge. The atoms in question have been strategically optimized to achieve a highly favorable state for the adsorption of intermediates. This optimization results from the introduction of new gap states around the Fermi level. Moreover, the presence of the interlayer bridge facilitates the electron transfer across the van der Waals gap, thereby enhancing the reaction kinetics. The hydrogen evolution reaction exhibits an impressive ultrahigh current density of 2000 mA cm-2 at 397 mV, surpassing the pristine MoS2 by approximately two orders of magnitude (26 mA cm-2 at 397 mV). This study provides new insights for enhancing the efficacy of 2D layered catalysts.

Association between two different lipid injectable emulsions and parenteral nutrition-associated cholestasis in very low birth weight infants: A retrospective cohort study.

BACKGROUND: Using soybean oil-based lipid emulsions (Intralipid), which contain higher amounts of ω-6 fatty acids and phytosterols in parenteral nutrition, is a risk factor for cholestasis (parenteral nutrition-associated cholestasis [PNAC]). An alternative form of a mixed lipid emulsion (SMOFlipid) has been developed to reduce the risk of PNAC, but significant benefits over Intralipid in very low birth weight (VLBW) infants have yet to be demonstrated. The aim of this study was to compare the differences in PNAC incidence in VLBW infants receiving SMOFlipid vs Intralipid. METHODS: The study was conducted in Sir Run Run Shaw Hospital of the Zhejiang University School of Medicine, Hangzhou, China, from January 2016 to March 2022. In total, 235 VLBW infants were administered SMOFlipid or Intralipid for ≥21 days and were included in the study. The primary outcome was the incidence of PNAC. Secondary outcomes included bronchopulmonary dysplasia, retinopathy of prematurity, necrotizing enterocolitis, late-onset sepsis, length of stay, weight 28 days after birth, severity of PNAC, and the time to reversal of PNAC. RESULTS: Forty-four VLBW infants (35.5%) in the SMOFlipid group vs 41 (36.9%) in the Intralipid group achieved PNAC (P = 0.817). The subgroup analysis showed that the peak direct bilirubin level was lower (median [interquartile range] 55.6 [36.4] vs 118.4 [77.2] µmol/L; P < 0.001), and the time to reversal of PNAC was shorter (44 [49] vs 96 [61]; P < 0.001) in the SMOFlipid group than in the Intralipid group. CONCLUSION: SMOFlipid may represent a better alternative for VLBW infants who require prolonged parenteral nutrition.

Aldehyde modified nanocellulose-based fluorescent hydrogel toward multistage data security encryption.

In view of the insecurity of encode information storage based on fluorescence switch single-stage encryption, a fluorescent hydrogel for multistage data security encryption were proposed, named as polyvinyl alcohol/dialdehyde cellulose nanofibrils/carbon quantum dots hydrogel. Herein, the interpenetrating network was formed by chemically crosslinking between polyvinyl alcohol (PVA) and dialdehyde cellulose nanofibrils (DACNF). Additionally, nitrogen-doped carbon quantum dots (CDs) synthesized by one-step hydrothermal method were introduced into the above hydrogel system by hydrogen bonds. The resultant fluorescent hydrogels possessed high stretchability up to 530 %, good strength of 0.96 MPa, Fe3+-responsive fluorescence quenching, fluorescence recovery triggered by ascorbic acid and borax-triggered shape memory. Moreover, various complex 3D hydrogel geometries were fabricated by folding/assembling 2D fluorescent hydrogel sheets, extending data encryption capability from 2D plane to 3D space. More remarkably, the 3D data encryption-erasing process of fluorescent hydrogel was realized by the strategy of alternating treatment of Fe3+ solution and ascorbic acid solution. This work provided a facile and general strategy for constructing high security important information encryption and protection.

Bifunctional Interphase Promotes Li+ De-Solvation and Transportation Enabling Fast-Charging Graphite Anode at Low Temperature.

The most successful lithium-ion batteries (LIBs) based on ethylene carbonate electrolytes and graphite anodes still suffer from severe energy and power loss at temperatures below -20 °C, which is because of high viscosity or even solidification of electrolytes, sluggish de-solvation of Li+ at the electrode surface, and slow Li+ transportation in solid electrolyte interphase (SEI). Here, a coherent lithium phosphide (Li3P) coating firmly bonding to the graphite surface to effectively address these challenges is engineered. The dense, continuous, and robust Li3P interphase with high ionic conductivity enhances Li+ transportation across the SEI. Plus, it promotes Li+ de-solvation through an electron transfer mechanism, which simultaneously accelerates the charge transport kinetics and stands against the co-intercalation of low-melting-point solvent molecules, such as propylene carbonate (PC), 1,3-dioxolane, and 1,2-dimethoxyethane. Consequently, an unprecedented combination of high-capacity retention and fast-charging ability for LIBs at low temperatures is achieved. In full-cells encompassing the Li3P-coated graphite anode and PC electrolytes, an impressive 70% of their room-temperature capacity is attained at -20 °C with a 4 C charging rate and a 65% capacity retention is achieved at -40 °C with a 0.05 C charging rate. This research pioneers a transformative trajectory in fortifying LIB performance in cryogenic environments.

Recent Progress in Using Mesoporous Carbon Materials as Catalyst Support for Proton Exchange Membrane Fuel Cells.

Developing durable oxygen reduction reaction (ORR) electrocatalysts is essential to step up the large-scale applications of proton exchange membrane fuel cells (PEMFCs). Traditional ORR electrocatalysts provide satisfactory activity, yet their poor durability limits the long-term applications of PEMFCs. Porous carbon used as catalyst support in Pt/C is vulnerable to oxidation under high potential conditions, leading to Pt nanoparticle dissolution and carbon corrosion. Thus, integrating Pt nanoparticles into highly graphitic mesoporous carbons could provide long-term stability. This Perspective seeks to reframe the existing approaches to employing Pt alloys and mesoporous carbon-integrated ORR electrocatalysts to improve the activity and stability of PEMFCs. The unusual porous structure of mesoporous carbons promotes oxygen transport, and graphitization provides balanced stability. Furthermore, the synergistic effect between Pt alloys and heteroatom doping in mesoporous carbons not only provides a great anchoring surface for catalyst nanoparticles but also improves the intrinsic activity. Furthermore, the addition of Pt alloys into mesoporous carbon optimizes the available surface area and creates an effective electron transfer channel, reducing the mass transport resistance. The long-term goals for fuel-cell-powered cars, especially those designed for heavy-duty use, are well aligned with the results shown when this hybrid material is used in PEMFCs to improve performance and durability.

Anomalous isotope effect on mechanical properties of single atomic layer Boron Nitride.

The ideal mechanical properties and behaviors of materials without the influence of defects are of great fundamental and engineering significance but considered inaccessible. Here, we use single-atom-thin isotopically pure hexagonal boron nitride (hBN) to demonstrate that two-dimensional (2D) materials offer us close-to ideal experimental platforms to study intrinsic mechanical phenomena. The highly delicate isotope effect on the mechanical properties of monolayer hBN is directly measured by indentation: lighter 10B gives rise to higher elasticity and strength than heavier 11B. This anomalous isotope effect establishes that the intrinsic mechanical properties without the effect of defects could be measured, and the so-called ultrafine and normally neglected isotopic perturbation in nuclear charge distribution sometimes plays a more critical role than the isotopic mass effect in the mechanical and other physical properties of materials.

Band-Edge Prediction of 2D Covalent Organic Frameworks from Molecular Precursor via Machine Learning.

The band-edge positions of two-dimensional (2D) covalent organic frameworks (COFs) play a crucial role in their applications in photocatalysts and nanoelectronics. However, massive amounts of 2D COFs with targeted band-edge positions from high-level first-principles calculations based on their composition are time-consuming due to the diversity and complexity of unit cell structures. Here, we report a strategy to predict the band-edge positions of 2D COFs by combining first-principles calculations with machine learning (ML). The root-mean-square error (RMSE) of the predicted valence band maximum (VBM) and conduction band minimum (CBM) between ML prediction and first-principles calculated values at the Perdew-Burke-Ernzerhof (PBE) level are 0.229 and 0.247 eV in test data set, respectively. In addition, a linear relationship is established between the PBE results and the HSE06 results with RMSE values of 0.089 and 0.042 eV for VBMs and CBMs in the test data set. Finally, a workflow is developed to determine the band-edge positions of the 2D COFs.

Establishment of a risk prediction model for multidrug-resistant bacteria in deceased organ donors: a retrospective cohort study in China.

Background: Multidrug resistance in bacteria is a serious problem in organ transplantations. This study aimed to identify risk factors and establish a predictive model for screening deceased organ donors for multidrug-resistant (MDR) bacteria. Methods: A retrospective cohort study was conducted at the First Affiliated Hospital of Zhejiang University School of Medicine from July 1, 2019 to December 31, 2022. The univariate and multivariate logistic regression analysis was used to determine independent risk factors associated with MDR bacteria in organ donors. A nomogram was established based on these risk factors. A calibration plot, receiver operating characteristic (ROC) curve, and decision curve analysis (DCA) were used to estimated the model. Results: In 164 organ donors, the incidence of MDR bacteria in culture was 29.9%. The duration of antibiotic use ≥3 days (odds ratio [OR] 3.78, 95% confidence interval [CI] 1.62-8.81, p=0.002), length of intensive care unit (ICU) stay per day(OR 1.06, 95% CI 1.02-1.11, p=0.005) and neurosurgery (OR 3.31, 95% CI 1.44-7.58, p=0.005) were significant independent predictive factors for MDR bacteria. The nomogram constructed using these three predictors displayed good predictive ability, with an area under the ROC curve value of 0.79. The calibration curve showed a high consistency between the probabilities and observed values. DCA also revealed the potential clinical usefulness of this nomogram. Conclusions: The duration of antibiotic use ≥3 days, length of ICU stay and neurosurgery are independent risk factors for MDR bacteria in organ donors. The nomogram can be used to monitor MDR bacteria acquisition risk in organ donors.

Electric-Field Control of Spin Polarization above Room Temperature in Single-Layer A-Type Antiferromagnetic Semiconductor.

Two-dimensional (2D) antiferromagnets have drawn great interest for absence of stray fields in antiferromagnetic (AFM) spintronics. However, it remains challenging to manipulate their spin polarization above room temperature for practical applications. Herein, a general strategy is reported to realize the control of spin polarization above room temperature in 2D A-type AFM semiconductors by external electric field based on first-principles calculations, exemplified by transition metal monohalide MnCl and carbide MXenes Cr2CX2 (X = F, Cl, OH). It shows that 100% spin polarization can be induced around Fermi level with spin splitting gap related to the spatial distribution of spin density in real space. Meanwhile, the Neél temperature of 2D MnCl and Cr2CF2 remains above room temperature under external electric field up to 0.6 V/Å. This study exhibits the potential for application of 2D AFM semiconductors in electric-field-controlled spintronics.