Browse Articles

Polyoxometalate‐Directed Assembly of Robust Coordination Cages: Overcoming Kinetic Inertness and Conformational Mismatch

Abstract The selective construction of kinetically robust coordination cages by self‐assembly remains a significant challenge in supramolecular chemistry. Herein, we report an efficient polyoxometalate (POM)‐directed self‐assembly strategy enabling the selective assembly of robust Pt 6 L 4 cages under thermodynamic or kinetic control, which is inaccessible via untemplated methods. For a planar ligand ( L1 ) with a dihedral angle (θ = 0°), the POM template promotes the formation of a thermodynamically favored Pt 6 ( L1 ) 4 analog. Remarkably, for a twisted and flexible ligand ( L2 ) with a nonideal dihedral angle (θ ≈ 36°), which typically favors the thermodynamically preferred M 12 L 8 cages, the POM template induces the formation of the kinetically trapped M 6 L 4 cages even when using inert Pt(II) precursors. In the absence of POMs, such structures cannot form due to conformational mismatch and the kinetic inertness of metal‐ligand coordination. The resulting Pt(II)‐based cages are highly stable and remain intact as discrete, template‐free hosts after POM removal, capable of encapsulating diverse guests in both acidic and basic aqueous media. This work highlights the unique templating role of POMs in accessing both thermodynamic and kinetic architectures, offering new opportunities for designing robust cages for drug delivery, sensing, and catalysis under harsh conditions.

Unveiling laser-induced ultrafast switching mechanism in ferromagnetic spin valves

The recent demonstration of single-shot ultrafast magnetization reversal in ferromagnetic spin valves—combining spin-transfer torque with optically induced ultrafast switching—has offered a promising avenue for next-generation magnetic storage technologies. However, a comprehensive theoretical framework is currently lacking to validate and elucidate the reversal mechanisms across different initial magnetic states. Here, we develop a theoretical model for optically induced ultrafast magnetization reversal by integrating the s-d exchange model with an atomistic spin dynamics approach. The proposed model's validity is corroborated through detailed comparisons with experimental time-resolved magneto-optic Kerr effect data. Our findings highlight distinct contributions from ultrafast demagnetization and ultrafast spin currents to the switching process. Furthermore, we systematically explore the influence of laser pulse parameters, such as fluence and width, as well as material-specific properties like magnetic anisotropy and Gilbert damping coefficients on ultrafast ferromagnetic reversal. Our findings indicate that increasing laser pulse fluence intensifies ultrafast demagnetization and enhances spin current strength, whereas extending pulse width delays demagnetization and diminishes spin current intensity. Notably, magnetic anisotropy exerts minimal influence on spin current generation, while higher damping coefficients amplify spin current intensity, thereby facilitating ultrafast reversal. Comparative simulations across various spin valve materials reveal that CoFe exhibits superior ultrafast spin current conversion efficiency compared to [Co/Ni]n and CoPt-based systems. This work establishes a robust theoretical framework for optically induced ultrafast magnetization reversal and provides critical insights for the design of future picosecond-scale, low-power, and nonvolatile magnetic recording devices.

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In-plane optical anisotropy in PbI2 nanosheets induced by CrOCl

Interface symmetry breaking in heterojunctions can introduce enhanced performance in optoelectronic devices, tunnel transistors, and catalytic applications. Herein, we report a solution recrystallization method for fabricating high-quality two-dimensional PbI2 nanosheets on mechanically exfoliated thin CrOCl flakes. The high crystalline quality of the synthesized heterojunctions is confirmed by a suite of characterization techniques, including atomic force microscopy and high-resolution transmission electron microscopy. Density functional theory calculations reveal the formation of a type-II band alignment at the interface, accompanied by charge transfer from the upper PbI2 layer to the underlying CrOCl. Photoluminescence (PL) and Kelvin probe force microscopy measurements confirm the interfacial charge transfer. Especially, angle-resolved polarized Raman and PL spectroscopy reveal that CrOCl induces in-plane anisotropy (IPA) in PbI2 with anisotropy ratios of 1.64 (Raman) and 1.65 (PL), which is primarily attributed to the anisotropic interfacial charge interactions. Our findings provide a platform for expanding the application prospects of isotropic PbI2 in polarization-related fields through interface induced IPA.

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Machine Learning‐Assisted Prediction of Ground‐ and Excited‐State Redox Potentials in Iridium(III) Photocatalysts

Abstract This study introduces a data‐driven framework that combines DFT calculations with machine learning to facilitate accurate and scalable predictions of ground‐ and excited‐state redox potentials for iridium(III) photocatalysts. We first constructed independent models to identify key geometric and electronic descriptors governing redox behavior. Shapley additive explanations‐based analyses revealed clear structure–activity relationships, offering mechanistic insights and rational guidance for tuning redox potentials. Based on these insights, we developed unified multi‐output models—Model G for ground‐state and Model E for excited‐state redox potentials—to enable rapid, cost‐effective, and high‐throughput predictions. By modeling oxidation and reduction processes within a shared descriptor space, we can reduce computational overhead while maintaining high predictive accuracy. To assess cross‐metal generalizability, residual transfer learning was applied to osmium (Os) photocatalysts. Using feature‐similar complexes, the resulting transfer models (G‐T, E‐T) achieved performance comparable to Os‐only baselines, demonstrating efficient few‐shot cross‐metal transfer. Collectively, this study establishes an interpretable and transferable machine‐learning framework for photocatalyst discovery. This framework provides a foundation for large‐scale screening and rational design across diverse transition‐metal platforms, accelerating advancements in photoredox catalysis, solar fuel production, and broader sustainable energy technologies.

Direct measurement of the electron wind force in cobalt nanowires

Copper back-end-of-line interconnects have been the industry standard for decades, but copper's susceptibility to electromigration failure has motivated a search for alternatives. While cobalt's resistivity is higher than copper's in bulk form, it scales more slowly with decreasing interconnect size, making cobalt a promising alternative for highly scaled interconnects. To better understand the electromigration behavior of cobalt, we map both temperature- and the current-induced strain in cobalt nanowires using a scanning transmission electron microscope equipped with an electron energy loss spectrometer. We consistently see cobalt move away from the anode, and we find cobalt's effective ionic charge Z*=+2±1 near 300 °C. This result will inform the design of highly scaled cobalt interconnects.

Suppression of optical losses in near-infrared PeLEDs using CH(NH₂)₂PbI₃ nanorods embedded in fluoride-based emissive layers

A Synergistic Cu/Ca Dual‐Doping Strategy for High‐Stability and Fast‐Charging O3‐Type Cathode in Sodium‐Ion Batteries

Abstract The O3‐type layered oxide cathodes are highly promising for sodium‐ion batteries due to their high specific capacity. However, the sluggish kinetics and poor interlayer stability caused by narrow layer spacing and volumetric stress accumulation limit their fast‐charging and long‐cycle performance. Herein, targeted interlayer regulation is conducted on O3‐type layered oxide by introducing Cu 2+ and Ca 2+ into the transition metal (TM) and alkali metal (AM) layers, respectively. The introduction of Cu 2+ effectively enlarges sodium‐ion transport channels, mitigates oxygen arrangement around TM octahedra, and suppresses Na + /vacancy ordering, which is evidenced by scanning transmission electron microscopy and density functional theory calculations. Additionally, Ca 2+ in the AM layer effectively mitigates volume variation during electrochemical reactions and preserves structural integrity, as confirmed by in situ X‐ray diffraction, resulting in lower lattice stress and mitigated phase evolution. The result is an exceptionally high‐rate capability of 86.02 mAh g −1 at 10 C (2.4 A g −1 ), accompanied by a prolonged lifetime with 80.64% retention after 300 cycles. This work demonstrates synergistic regulation of ion transport and lattice stability, providing new insights for cathode design.

Stress engineering in ferroelectric hafnium oxide for tuning epitaxial orientation

The development of next generation computing paradigms and memory devices relies on exploiting the unique properties of ferroelectric materials. Hafnium oxide-based ferroelectrics, which are highly compatible with semiconductor processing, offer a promising alternative to conventional perovskite ferroelectrics that face integration challenges. However, the enhancement of ferroelectricity in hafnium oxide and its dependence on epitaxial growth orientation remain insufficiently explored. In this study, we demonstrate that the epitaxial orientation of hafnium oxide is strongly correlated with the in-plane strain conditions. Depending on the strain state, the HfO2 film exhibits either (002)- or (111)-oriented epitaxial growth. Notably, the (002)-oriented films exhibit enhanced ferroelectric polarization. These findings provide an effective strategy for achieving controllable epitaxial growth of ferroelectric HfO2 and for further improving its ferroelectric performance in practical applications.

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Enhanced thermal performance of AlN/GaN/AlN XHEMTs on bulk AlN by suppression of phonon-boundary scattering

AlN/GaN/AlN high electron mobility transistors (HEMTs) have demonstrated exceptional potential for surpassing the electrical limitations of conventional AlGaN/GaN HEMTs. This study investigates the thermal performance of two types of AlN/GaN/AlN HEMTs with homoepitaxial AlN buffer layers grown on AlN substrates: an AlN/GaN/AlN single-crystal HEMT (AlN XHEMT) featuring a pseudomorphic/thin GaN channel and a conventional structure with a relaxed/thick GaN channel. Frequency- and time-domain thermoreflectance measurements reveal bulk-like thermal conductivity in the homoepitaxial AlN buffer layer, with negligible thermal boundary resistance at the AlN buffer/substrate interface. Consequently, Raman thermometry demonstrates that the AlN XHEMT with a thin (∼20 nm) pseudomorphically strained GaN channel exhibits better thermal performance than identical HEMT layer structures grown on a 4H-SiC substrate, despite 4H-SiC possessing a higher thermal conductivity. In addition, the AlN XHEMT exhibits a 22% lower channel temperature under 14 W/mm power density than the AlN/GaN/AlN-on-AlN HEMT that employs a thick (275 nm) relaxed GaN channel. These findings highlight that AlN XHEMTs offer not only electrical but also thermal advantages for high-power and high-frequency applications.

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Thickness scaling and ferroelectric switching in wurtzite structure zinc magnesium oxide thin films

This study reports the thickness scaling of sputtered ferroelectric Zn0.61Mg0.39O (ZMO) thin films down to 43 nm. Encapsulated IrO2/ZMO/Ir capacitors exhibited switchable polarizations exceeding 50 μC cm−2 and coercive fields that increased from 3.9 to 4.4 MV cm−1 as the thickness decreased. Switching kinetics are best described by the simultaneous non-linear nucleation and the growth model. Bimodal switching is prevalent at low thicknesses, with the fastest switching times measured to be approximately 400 ns. Device encapsulation made ZMO switching kinetics more abrupt, potentially due to changes in the concentration of atmosphere-induced defects such as hydroxides. These results demonstrate stable ferroelectricity and sub-microsecond switching in sub-50 nm wurtzite ZMO, highlighting its potential as a low-voltage ferroelectric for integrated nonvolatile memory applications.

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Inverting Palladium–Phosphorus Lewis Pair Formation: Phosphonium Acting as Z‐Type Ligand

Abstract Phosphorus‐based ligands are prototypical L‐type donors. Here, we introduce a Lewis acidic phosphonium cation that engages in unprecedented Z‐type coordination to palladium(0). The resulting Pd→P(V) interactions are structurally unique and stronger than conventional L‐type Pd─phosphine bonds, as revealed by NMR spectroscopy, x‐ray crystallography, and quantum chemical analyses (NBO, ETS‐NOCV, and QTAIM). It enables the formation of rare L 2 Z‐type Pd(0) complexes with distinctive optical and electronic properties. A notably mild P─C bond forming reaction suggests an overlooked role of Z‐type interactions for facilitating reductive elimination pathways.

Alternating Magnetic Field Induced Ultra‐Active Cu Sites in Trimetal‐Organic Frameworks for Low‐Overpotential CO ₂ Electroreduction

Abstract The electrochemical CO 2 reduction reaction is a sustainable approach to address climate challenges, requiring energy‐economic catalysts that are highly active at low electrode potentials. Herein, we developed a Cu‐ZnMg ultrathin metal‐organic framework (MOF), where Zn/Mg atoms enhance CO 2 adsorption and CO desorption and the Cu sites show ultrahigh catalytic activity from CO 2 ‐to‐CO electroreduction under an alternating magnetic field (AMF). The Cu‐ZnMg MOF@AMF exhibited a high current density (25.3 mA cm −2 ) at a low potential of −0.2 V versus RHE with remarkable CO selectivity (∼95%), surpassing that of state‐of‐the‐art Cu‐based catalysts. The incorporation of nonmagnetic metals isolates the unpaired electrons at Cu(II) active sites which are antiferromagnetically coupled in the 1D Cu(II) chains. These spin magnetic moments can effectively interact with the AMF through spin‐lattice relaxation, leading to local electronic energy elevation at the Cu sites. This AMF‐induced activation of isolated Cu sites promotes cooperative proton‐electron transfer, thereby enabling efficient from CO 2 ‐to‐CO conversion at low electrode potential.

Magnetic phase transitions in Sr-defective monolayer FeSe/SrTiO3 interfaces: A first-principles study

The significantly enhanced superconducting transition temperature (Tc) observed at the FeSe/SrTiO3 (FeSe/STO) interface has garnered substantial attention over the past decade. Numerous experiments have demonstrated that the complex TiOx-terminated STO interface structure plays a crucial role in mediating superconductivity. In this work, using first-principles calculations, we find that the magnetic ground state of the interface structures exhibits two distinct evolutionary trends: it shifts from paramagnetic (PM) to an (anti-)ferromagnetic state in the presence of Sr defects or charge doping, and transitions to a ferromagnetic state when the substrate thickness is less than five atomic layers. Calculated spin charge density differences reveal that the polarized spins are primarily distributed around the interface region. As the thickness of the STO substrate increases, electrons transfer from the interface to the substrate—this leads to a reduction in the polarized spin density near the interface and ultimately drives a transition to the PM phase. Our results reveal that the magnetic moments of Fe atoms in FeSe/STO with a TiOx interface structure increase with increasing atomic layer thickness, whereas those in FeSe/STO without a TiOx interface structure exhibit the opposite trend (i.e., decreasing). In addition, compared with the previously reported band structure, the additional Ti-derived bands crossing the Fermi energy are absent. More importantly, we can observe the replica band near the M point, which is in agreement with previously reported results. Our results indicate that the magnetic properties of the FeSe/STO interface are critical to achieving high-temperature superconductivity.

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Tuning magnetocaloric effect of monolayer via flexomagnetism

Flexomagnetism, a coupling between strain gradient and magnetization, offers an alternative pathway to tune the magnetocaloric effect (MCE) by leveraging huge strain gradients in monolayers. Herein, we demonstrate that shear-strain gradient can modulate the Dzyaloshinskii–Moriya interaction in monolayer CrN and then influence the external magnetic field-induced magnetization reversal process characterized by topological magnetic textures, ultimately enabling tuning of the MCE. It is found that strain gradient can increase the isothermal magnetic entropy change (ΔSM) and adiabatic temperature change (ΔTad) of monolayer CrN. A shear-strain gradient of 3 × 107/m was seen to effectively tune ΔSM at low temperatures due to the entropic contribution associated with the topological-to-ferromagnetic magnetic phase transition. Our results suggest a new route to tailor the MCE of monolayers via strain gradients by exploiting flexomagnetism.