Browse Articles

Aqua‐Oxidation of Polyethylene Into Carboxylic Acids Under Mild Conditions: A Catalyst‐Free Upcycling Strategy for Nonpolar Plastics

ABSTRACT Noncatalytic polyolefin upcycling offers distinct advantages in eliminating catalyst costs and enhancing operational stability, yet it remains highly challenging under mild conditions. Herein, we develop an aqua‐oxidation strategy that converts polyethylene into carboxylic acids at 160°C without using any catalysts or organic solvents. The mass yield of carboxylic acid is up to 97.8 wt%, of which 72.1% is comprised by C 4 –C 10 dicarboxylic acids. The roles of H 2 O and O 2 play in aqua‐oxidation were further investigated in an in situ liquid‐phase spectroscopic reactor filled with isotope‐labeled D 2 O. It reveals that O 2 governs the effective initiation and oxidation of polyethylene. Whereas H 2 O serves as a key medium to intensify oxygen–polyethylene interaction uniformly and inhibit localized oxidation, promoting selective upcycling to narrow‐distributed acids. Moreover, this strategy allows for upcycling diverse commercial polyolefins with additives. This study presents a breakthrough in the noncatalytic upcycling of polyolefins under mild conditions and demonstrates the potential of this eco‐friendly and streamlined strategy for advancing plastic circularity.

Direct nanoscale characterization of polarization-dependent diffusion in non-polar GaN via scanning diffusion microscopy

Non-polar GaN planes (e.g., a-plane and m-plane) present a promising path to mitigate the quantum-confined Stark effect inherent to polar orientations, thereby enhancing the efficiency of optoelectronic devices. Their inherent optical polarization anisotropy is also advantageous for applications requiring polarized light without using a polaroid. However, the polarization-dependent carrier diffusion behavior in non-polar GaN, which is governed by different valence bands and critically influences device performance, remains inadequately characterized. Here, we employ scanning diffusion microscopy based on photo-assisted Kelvin probe force microscopy to quantitatively map the polarization-dependent carrier diffusion coefficients in non-polar a-plane and m-plane GaN. By comparing the diffusion behavior under light polarized perpendicular and parallel to the c-axis, we reveal a clear polarization dependence that aligns with the effective mass. Our study provides the first direct nanoscale mapping of polarization-dependent diffusion coefficients in non-polar GaN, bridging a critical gap between macroscopic transport properties and microscopic band structure parameters. In future, the polarization-dependent diffusion in non-polar GaN-based devices would provide information for better design of the transverse-electric or transverse-magnetic modes via band control.

The combined effects of viscoelasticity and shear-thinning on the flow characteristics of gel propellant in nozzle injectors

Gel propellants exhibit significant potential for aerospace propulsion systems due to their complex combined viscoelastic and shear-thinning properties, enabling mobility adjustments to suit diverse flow conditions. However, current research predominantly focuses on either their shear-thinning characteristics alone or isolates the study of their non-Newtonian flow behaviors. Here, we investigate the flow dynamics of gel propellants in converging–diverging nozzles, focusing on the synergistic mechanisms of viscoelasticity and shear-thinning behaviors. Using the White–Metzner constitutive model, we reveal that the drag reduction mechanism is governed by the concurrent modulation of the first normal stress difference (N1) and shear stress. Compared to purely elastic flows, our stress analysis demonstrates that shear stress reduction makes the primary contribution to the enhanced discharge coefficient (CD), while N1 plays a secondary yet non-negligible role. Viscoelasticity is found to actively suppress the shear stress magnitude, and this effect is more prominent in the low Reynolds number (low-inertia) regime, thereby exerting stronger flow control at low velocities. While the impacts of shear effect on CD dominates over a wider Reynolds number (Re) regime compared to the viscoelastic contribution, as the energy dissipation due to viscous losses dominate over elastic losses. These findings clarify the hierarchy of stress contributions in confined non-Newtonian flows, and fill the gap in understanding the combined effects of multiple rheological properties on the flow of gel propellants in nozzles.

Selective Upcycling of Polycarbonate Waste to Cyclohexanol via RuLa Dual‐Atom Catalysis

ABSTRACT Cyclohexanol is a key intermediate for nylon manufacture, yet its industrial synthesis relies on partial oxidation of cyclohexane at ∼2 MPa with <5% single‐pass conversion, an energetically wasteful and atom‐inefficient process that demands extensive recycle and generates substantial emissions. Here, we introduce an oxygen‐atom‐efficient synthetic strategy that transforms polycarbonate (PC) waste directly into cyclohexanol through a non‐oxidative catalytic route. The method leverages the intrinsic oxygen functionality of the polymer as a built‐in source of hydroxyl groups, thereby eliminating the conventional oxidation step. A RuLa dual‐atom (RuLa‐DA) catalyst anchored on CoAl oxide enables cooperative hydrogen activation and spillover through moderated Ru–H binding, driving selective aromatic‐ring hydrogenation under mild gas‐phase conditions. Operating at 0.25 MPa and a 4.2 s residence time, the tandem hydropyrolysis–hydrogenation process affords a 69.9% yield and 95.4% selectivity for cyclohexanol, maintaining >95% selectivity for post‐consumer PC over 100 feed cycles. Life‐cycle and techno‐economic analyses indicate the potential environmental and economic advantages, showing a 35% cost reduction and a threefold lower carbon footprint relative to the fossil route. This oxygen‐retentive hydrogenation paradigm establishes a general approach for valorizing oxygen‐rich substrates and suggests a conceptually viable pathway toward atom‐economical synthesis and circular chemical manufacturing.

Preferential formation of highly efficient Eu luminescent centers in Eu-doped GaN grown on semipolar (202¯1) GaN

Eu-doped GaN (GaN:Eu) exhibiting bright red emission is a promising material for the realization of ultrahigh-resolution micro-light-emitting diode (LED) displays that can be applied to virtual reality/augmented reality/mixed reality. The full-color monolithic integration of a red GaN:Eu LED and blue/green InGaN LEDs is a key technology, in which the use of semipolar substrates is preferred to suppress wavelength shift in the InGaN LEDs under current injections. We investigate the effects of the growth plane on GaN:Eu-based red emission and find that the emission intensity from a semipolar (202¯1) GaN:Eu is drastically enhanced as compared with a conventional (0001) GaN:Eu,O. Combined excitation–emission spectroscopy reveals that the fraction of Eu luminescent centers with different local structures dramatically changed. A highly efficient Eu center is preferentially formed, and its abundance increases by more than two orders. These results show a clear pathway to develop a red LED with higher light output power.

Detwinning deformation behaviors in Fe-Co-Ni-Al-Ti multi-component alloys

FeCoNi-based multi-component alloys have great potential for engineering applications due to their excellent mechanical properties. In this study, (FeCoNi)95(AlTi)5 and (FeCoNi)90(AlTi)10 alloys (named AT5 and AT10) were prepared by vacuum arc melting and then homogenized, cold-rolled, and recrystallized in sequence. It was found that the AT5 alloy had a single FCC phase, while the AT10 contained an FCC matrix, and L12 precipitates with a grain size of ∼4.6 nm and a volume fraction of ∼17.3%. The microstructural evolution and deformation behaviors at different deformation stages were systematically studied by in situ tensile electron backscatter diffraction. Results showed that the AT5 alloy has a yield strength of 231 MPa and a ductility of 55.4%, whereas the AT10 alloy reaches 327 MPa and 34.5%. The AT5 alloy deformed by dislocation planar slip, in contrast to the wavy slip in the AT10 alloy. The increased large-sized atoms in AT10 alloy caused significant lattice distortion and solid solution strengthening, which increased the dislocation density and enhanced strain hardening capacity. However, the solute drag and nano-precipitates led to inhomogeneous deformation within grains, promoting void formation and premature failure. Both alloys showed a strain-induced detwinning behavior at different deformation stages. Despite a lower stacking fault energy in the AT10 alloy, its annealed twin content was reduced due to the nano-precipitates and solute drag. This in situ study provides real-time and compelling insights into the deformation mechanisms of high-performance multi-component alloys.

Constructing Wide‐Temperature‐Range Li–S Batteries Through Synergistic Boride Spin‐Polarization Coupling Regulation and Magnetohydrodynamic Effects

ABSTRACT Lithium–sulfur batteries, despite their high specific capacity, high theoretical energy density, environmental benignity, and low cost‐related unique advantages, face critical challenges including polysulfide shuttling, sluggish redox kinetics, and uncontrolled lithium dendrite growth. Here, we propose a magnetic field cooperative regulation strategy that concurrently optimizes both sulfur cathode and lithium via spin engineering and magnetohydrodynamic (MHD) effects. Bilayer‐hollow FeNi boride bipyramids (FeNi─B) with nanoreactor architectures were designed, in which an external magnetic field triggers 3d‐orbital electron spin rearrangement. Simultaneously, the uniform distribution of ions and dendrite‐free deposition were achieved by driving lithium‐ion spiral convection through MHD effects. It is worth noting that the optimized cells exhibit exceptional cycling stability under extreme conditions (−40°C). Density functional theory and multiphysics simulations jointly reveal two mechanisms: Spin‐polarization‐enhanced adsorption energy for sulfur species and lithium protection via Lorentz‐force‐mediated ion transport. This work establishes a novel paradigm for designing magnetic field‐responsive electrocatalysts and manipulating spin‐orbit coupling, offering broad implications for multiphysical‐field strategies in next‐generation batteries.

Achieving programmable bipolar photocurrents via <i>p</i> – <i>n</i> junction design for PEPS-based optoelectronic applications

The photoelectrochemical photocurrent switching (PEPS) effect, which enables a single photodetector to generate opposite photocurrent polarities under varied conditions, offers key insights into carrier dynamics at heterojunctions and holds promise for advanced applications in photoelectric logic, optical communication, and self-powered sensing. To achieve wavelength-programmable bipolar photocurrents, this study designed two distinct heterojunctions, such as a p–n junction (Cu2O/α-Ga2O3) and an n–n junction (CdS/α-Ga2O3), and compared their PEPS behaviors. The designed p–n junction successfully realized the desired PEPS effect at 0 V bias, exhibiting a positive photocurrent under 254 nm UV light and a negative photocurrent under 365 nm illumination. In contrast, the n–n junction showed no such polarity switching. This functional difference is attributed to the strong, unidirectional built-in electric field engineered into the p–n junction, which orchestrates wavelength-selective carrier transport and thus dictates the photocurrent polarity. The weaker, diffuse field in the n–n junction fails to achieve this directional control. By leveraging the programmable bipolar photoresponse of the designed p–n device, we further demonstrated its application as a single-element half-adder for simplified logic circuits and its potential for high-density coding and binary phase shift keying modulation in optical communication. This work confirms that intentional band engineering through heterojunction design is the key to materializing the PEPS effect, providing a clear design principle and material platform for developing advanced intelligent photoelectrochemical devices.

Daily briefing: How labs are coping with ‘RAMmageddon’

Product Ligand‐Modification on Ni(OH) ₂ for Boosted Electrocatalytic Oxidation of Aromatic Alcohols

ABSTRACT The development of active electrocatalysts for converting biomass‐derived aromatic alcohols into value‐added acids is of great significance. Ni(OH) 2 has been employed as a cost‐effective catalyst, unfortunately, suffering from rather low catalytic activity due to the considerable energy barrier to transform into active NiOOH and the weak interaction with reactants. To address these limitations, a novel “product ligand‐modification” (PLM) strategy has been proposed here simply by adopting the target molecule ligands as modification units, which simultaneously facilitates the Ni(II)/Ni(III) redox kinetics and significantly enriches reactants at the catalytic surface via profound π‐π stacking interaction. The PLM strategy has been demonstrated to exhibit exceptionally high performance in electro‐oxidizing aromatic alcohols into corresponding acids across various product ligand‐Ni(OH) 2 (PL‐Ni(OH) 2 ) catalysts. As a typical paradigm, the aromatic ligand FDCA‐modified Ni(OH) 2 catalyst (termed FDCA‐Ni(OH) 2 ) demonstrates significantly enhanced BHMF electrocatalytic oxidation activity, featuring a BHMF conversion rate of &gt;99.4%, FDCA selectivity and yield of 99.2% and 98.6%, and Faradaic efficiency of 99.0%. Furthermore, FDCA‐Ni(OH) 2 features an excellent stability for over 250 h in a flow electrolyzer to produce FDCA with a &gt;99.0% purity. This PLM strategy offers valuable insights into the performance enhancement of Ni(OH) 2 catalyst for the targeted conversion of aromatic reactants.

Enhancement of piezoelectric response based on oxygen vacancy migration behavior in (K, Na)NbO3 crystals

Piezoelectric properties of materials are strongly influenced by atomic-scale defects. Proper design and modulation of oxygen vacancy (VO⋅⋅) through external fields are crucial for the comprehensive optimization of piezoelectric materials. In this study, we investigate the effects of poling on VO⋅⋅ in potassium sodium niobate (KNN) crystals, and design corresponding strategies to enhance the piezoelectric performance. We confirm the migration of VO⋅⋅ toward the negative surface under an electric field, which is then retained after the removal of the field, resulting in a VO⋅⋅-rich negative surface. Based on this, we grind away the negative surface to reduce VO⋅⋅ and weaken the shielding effect, significantly improving the small-signal d33 (from 276 to 338 pC/N) and electric field-induced strain performance (from 0.038% to 0.081%). Furthermore, the decreased VO⋅⋅ enhances the switching capability of domains, resulting in an additional transformation of the polarization orientations from [1 1¯ 0] to [1¯ 01], compared to that of the original crystal. These findings contribute to fully exploring the application potential of KNN crystals. The VO⋅⋅-rich surface of poled KNN crystals may offer promising applications in piezoelectric catalysis. Our results provide valuable insights for the modulation of piezoelectric properties.

Robust helicity-dependent phononic switching of magnetization via polarization-modulated transient gratings

Optical control of magnetization has emerged as a promising approach to achieve ultrafast and energy-efficient magnetization reversal. Here, we investigate helicity-dependent switching of magnetization driven by the resonant excitation of circularly polarized transverse-optical phonons, using a polarization-modulated transient grating. Our results show that the polarized phonons within the sample substrate induce robust, helicity-defined magnetization reversal in the magnetic overlayer. Moreover, the quality of switching remains largely unaffected when the degree of ellipticity of the infrared excitation is varied at frequencies resonant with the targeted phonon modes. Conversely, as the excitation is moved slightly off resonance, switching quality becomes highly sensitive to the ellipticity of the incident light.

Outside Front Cover: A Redox‐Active Mesoporous Cobalt–Pyrazolate Framework for Reversible O ₂ Sorption (Angew. Chem. Int. Ed. 12/2026)

Field-validated underwater microcavity acoustic sensor

Whispering-gallery-mode resonators offer a promising route to broadband, high-sensitivity underwater acoustic detection. However, their frequency-dependent sensing mechanism is not yet fully understood. In this paper, we present a comprehensive acoustic sensing model in which fiber vibration serves as the dominant transduction mechanism. This model demonstrates good agreement with water tank experiments across 100 Hz to 100 kHz. The laboratory tests reveal that the sensitivity of the sensor is 1–2 orders of magnitude higher than the reference hydrophone. The robustness of the sensor was first established through free-fall and seawater immersion tests. Subsequently, we successfully demonstrated its performance in in situ lake and sea trials, where we reconstructed underwater acoustic pressure maps that showed strong agreement with measurements from a commercial reference hydrophone. This work not only clarifies the sensing mechanism of underwater microtoroidal sensors but also demonstrates their significant potential for practical underwater acoustic applications.

Discovering the pH‐independent Oxygen–Oxygen Formation via Direct Mn‐oxo Coupling

ABSTRACT Unraveling the mechanism of O─O bond formation on metal‐oxo is critical yet remains a central challenge in electrocatalytic water oxidation. Herein, we show the pH‐independent O─O bond formation pathway in edge‐shared dual [MnO 6 ] motifs. By manipulating the atomic‐scale connectivity of [MnO 6 ] units, two structurally well‐defined sodium manganese pyrophosphate compounds with edge‐sharing (Mn‐edge) and corner‐sharing (Mn‐corner) [MnO 6 ] octahedral configurations were synthesized with similar chemical composition and morphology, except that the Mn ∼ Mn distance in Mn‐edge is significantly shorter than that in Mn‐corner. Electrochemical and spectroscopic analyses reveal that Mn‐edge exhibits an unprecedented pH‐independent evolution of O 2 . Isotope‐labeling experiments and in situ Raman spectroscopy identify a direct coupling mechanism between Mn−O species in Mn‐edge, bypassing the conventional nucleophilic water attack. Density functional theory calculations further support that Mn‐oxo coupling between asymmetric Mn VI  ∼ Mn V centers drastically reduces the energy barrier for O─O bond formation. These findings establish the connectivity of [MnO 6 ] as a critical descriptor for water oxidation mechanism and offer a new design strategy for efficient catalysts inspired by natural oxygen‐evolving complexes.

Leveraging acoustic and mechanical wave phenomena to fabricate Cu(2-x)CoxP2O7 as electrocatalysts for energy storage and electrochemical water splitting application

The development of renewable energy systems require the unification of efficient energy storage and hydrogen production facilities. Trifunctional electrocatalysts function as a single system which synchronously enables charge storage, hydrogen evolution reaction (HER), and oxygen evolution reaction (OER), providing a congruent platform. Systematic synthesis techniques promote the enhancement of catalytic activity, and long-term stability. In this context, low-frequency ultrasound (∼20 kHz) induces severe cavitation with the resultant physical forces generating radicals that primarily drive sonochemical processes. In this work, we employed a mechanical wave-assisted synthesis method to prepare Cu(2-x)CoxP2O7. The resulting electrocatalyst delivers an impressive specific capacitance of 681 F g−1, maintaining a cycling stability of 81% after enduring 30 000 cycles. The constructed symmetric supercapacitor attains an energy density of 17.4 Wh kg−1 and a power density of 699 W kg−1. Furthermore, CuCoP2O7 delivers strong bifunctional activity, necessitating merely 64 mV for HER and 288 mV for OER to reach a current density of 10 mA cm−2 while also facilitating overall water splitting by attaining 20 mA cm−2 at 1.60 V. Remarkably, the electrocatalyst achieves a Faradaic efficiency of 97.5%, demonstrating its outstanding effectiveness in facilitating oxygen and hydrogen evolution. These multifunctional electrocatalysts establish a pathway toward scalable, high-performance devices that integrate electrochemical energy storage with sustainable hydrogen production.

A Mechanochemical Kolbe–Schmitt Reaction: Catechol Carboxylation Provides Building Blocks for Renewable Plasticizers

ABSTRACT Catechol, an important aromatic platform molecule which can be derived from biomass, was carboxylated by mechanochemical Kolbe–Schmitt reaction of disodium catecholate with CO 2 , providing a mixture of mono‐ and dicarboxylated catechol derivatives. While classical protocols require harsh reaction conditions, involving a high temperature and/or CO 2 pressure, a mild ball milling method was developed. This represents the first mechanochemical Kolbe–Schmitt reaction featuring a low CO 2 pressure and reactivity at room temperature. From the individual catechol‐based mono‐ and dicarboxylic acid reaction products, a library of novel renewable plasticizers was synthesized through esterification of the carboxylic acid functionalities and O ‐acylation of the phenolic hydroxy groups. The resulting esters were evaluated in poly(vinylchloride) (PVC) and poly(lactic acid) (PLA), revealing plasticizing efficiencies competitive to benchmark commercial plasticizers. These efficiencies were maintained when the best performing ester substitution pattern was installed on the ball mill‐derived mixture of mono‐ and dicarboxylated catechols, making resource intensive separation (e.g. chromatographic separation) of these ortho ‐dihydroxybenzene(di)carboxylic acids redundant.

Bilayer oxide memristor based on IGZO/IAZO structure for artificial tactile perception system

Rapid advances in neuromorphic computing and intelligent perception demand electronic devices that faithfully replicate human nociception, which is crucial for achieving human–computer interaction. In this study, a self-limiting and volatile transparent ITO/IGZO/IAZO/ITO memristor with a bilayer structure is designed and prepared. Compared with the traditional single-layer structure (ITO/IAZO/ITO and ITO/IGZO/ITO) devices, the bilayer device exhibits better I–V cycling stability, more focused current response, and narrower distribution of volatile voltage in terms of electrical performance, reflecting improved device consistency and reliability (μ increased by ∼43% and σ increased by ∼57%). The ITO/IGZO/IAZO/ITO memristors are able to effectively mimic the core characteristics of biological nociceptors, including “threshold,” “no adaption,” “relaxation,” and “sensitization of allodynia/hyperalgesia.” By integrating the IGZO/IAZO memristor with a piezoresistive force sensor, a biomimetic nociceptive sensing system is further constructed for responding to external noxious stimuli, which demonstrates the potential of self-protective neuromorphic electronics.

Multifaceted Molecular Design Enables Comprehensive Luminescence Modulation in Metalloligand‐Stabilized Gold Nanoclusters

ABSTRACT Photoluminescent metal nanoclusters hold promise for optoelectronics, photonics, and chemosensing, yet systematic modulation of their emission within a single system remains challenging. Here, we report two isostructural clusters, Au 13 @Au 3 ‐Cl and Au 9 Cu 4 @Au 3 ‐Cl , stabilized by a tridentate phosphine (NP 3 ) metalloligand. Both adopt an unprecedented “Au 9 M 4 (Au/Cu) icosahedron + Au 3 crown” configuration and exhibit high solid‐state PLQYs of 44.5% and 38.9%, respectively. In contrast, replacing NP 3 with a monophosphine ligand (BPP) affords Au 9 Cu 4 ‐Cl lacking the Au 3 crown, with a dramatically reduced PLQY of 0.6%, highlighting the crucial roles of NP 3 and the Au 3 crown in boosting luminescence. Distinct photophysical behaviors are observed: Au 13 @Au 3 ‐Cl shows phosphorescence, while Au 9 Cu 4 @Au 3 ‐Cl exhibits thermally activated delayed fluorescence (TADF), confirmed by femtosecond transient absorption spectroscopy. The role of Cu doping is further supported by the TADF activity of Au 9 Cu 4 ‐Cl . Coordinating anion substitution also modulates emission, with iodide promoting TADF in Au 13 @Au 3 ‐I . Moreover, the NP 3 ligand confers reversible protonation‐induced luminescence switching, enabling chemosensing potential. Collectively, these findings demonstrate a comprehensive investigation of TADF behavior and luminescence modulation in atomically precise metal nanoclusters, systematically engineered through heteroatom doping of the inner core, ligand design and anion exchange at the coordination surface, and outer‐sphere complexation and protonation.

Effects of interlayer electrons and high-order anharmonicity on phonon thermal transport of electride Sc2C

Electrides have attracted considerable research interest over the past four decades owing to their rich physical properties. However, their phonon thermal transport behavior, which is critical for thermal management applications, remains relatively unexplored. In this work, we systematically investigate the influence of high-order anharmonicity and interlayer electrons on the lattice thermal conductivity (κL) of Sc2C using density functional theory calculations combined with the phonon Boltzmann transport equation. Our results reveal that four-phonon scattering processes substantially suppress the κL of Sc2C, leading to remarkable reductions of 61.5% in the in-plane and 58.6% in the out-of-plane directions at 300 K due to the strong quartic anharmonicity. Furthermore, the removal of interlayer electrons markedly reduces the in-plane κL, while its effect on the out-of-plane component remains minimal. This anisotropic behavior is attributed to a competition between two opposing effects: an increase in phonon group velocity due to lattice contraction, and enhanced phonon scattering rates resulting from increased anharmonicity upon the removal of interlayer electrons. This work deepens our understanding of the phonon thermal transport property of Sc2C and provides a theoretical guidance for regulating the κL of electride materials.