The transition to sustainable energy relies on the efficient conversion of CO2 into specific multi-carbon (C2+) products, yet this process is severely hindered by the slow kinetics of C─C coupling and uncertain product selectivity. Single-atom catalysts (SACs) exhibit promising catalytic performance but suffer from a fundamental limitation: their lack of contiguous active sites impedes C─C coupling. Herein, we report an innovative isotropic 2D Cu single-atomic-layer catalyst anchored on amorphous carbon substrate, designed to enhance C─C coupling and C2+ selectivity. By stabilizing Cuδ + species and precisely tuning the Cu-Cu spacing to 2.35 Å-matching the C─C bond length of ethylene (C2H4), which significantly promotes C2H4 production. The catalyst achieved a remarkable Faradaic efficiency of 78.6% for C2H4 at -0.8 V versus the reversible hydrogen electrode, accompanied with high stability over 120 h. These findings not only elucidate the profound impact of spatially controlled active sites in complex multi-step reactions but also represent a significant leap forward in CO2 conversion technologies, offering great potential for sustainable carbon utilization and addressing global energy transition challenges.

Bound states in the continuum (BICs) suppress radiative leakage and enable high-Q resonances for terahertz (THz) photonics. Here, we propose a metallic quadrumer metasurface in which dual quasi-BICs are efficiently excited via translational-symmetry perturbations, while preserving the overall C4v symmetry, leading to polarization-insensitive operation. The two resonances originate from distinct BIC mechanisms, namely, a Gamma-point symmetry-protected BIC and a Friedrich-Wintgen BIC arising from modal interference, and evolve into coexisting Fano and electromagnetically induced transparency (EIT)-like responses within the same design. Notably, the resonance frequencies remain nearly unchanged across the perturbation range, indicating strong spectral robustness due to negligible variation of the metasurface's effective refractive index. Terahertz time-domain spectroscopy (THz-TDS) measurements show consistent overall trends with simulations, while discrepancies in Q-factor and spectral contrast are mainly attributed to metallic loss and fabrication/measurement non-idealities. This work provides a compact route toward polarization-robust, multi-mode high-Q THz metasurface devices for filtering, sensing, and dispersion control.

In this paper, we propose a three-layer all-dielectric multi-band multifunctional chiral metasurface, designed to achieve circular dichroism (CD), extinction ratio (ER), and asymmetric transmission (AT). This multifunctional chiral metasurface attains four CD bands in the near-infrared wavelength range of 710-770 nm, with three of these bands exceeding 0.98 in absolute value. Within the same wavelength range, it also achieves four ER bands, three of which exceed 30 dB in absolute value. Additionally, the metasurface demonstrates high AT with absolute values close to 1 across five bands in this range. Mechanism analysis shows that the selective excitation of multiple resonant modes and interlayer electromagnetic coupling are the core sources of its excellent performance. This structure has advantages such as low loss, CMOS compatibility, and strong process robustness, and it has important application potential in near-infrared polarization detection, chiral sensing, and on-chip integrated photonic systems.

We propose a vanadium dioxide-based reconfigurable terahertz metasurface with switchable ultra-broadband polarization conversion and ultra-broadband absorption. By employing a dual-layer architecture consisting of an anisotropic vanadium dioxide-gold mosaic layer and a symmetric vanadium dioxide circular-patch layer, the proposed design independently optimizes the two functions and breaks the inherent bandwidth-performance trade-off. In the insulating state, the device realizes an ultra-broadband polarization conversion with a polarization conversion ratio above 90

Objective Terahertz (THz) waves, with frequencies ranging from 0.1 to 10 THz and wavelengths from 30 to 3000 mu m, exhibit unique characteristics such as low energy, high penetration, transient behavior, and non-ionization, making them ideal for detecting material properties. However, the limited response of conventional materials to THz waves restricts the sensing capabilities. Metamaterials with tunable electromagnetic properties provide a solution, offering higher sensitivity and efficiency compared to other sensing technologies. Despite this, the sensitivity and resolution of current metamaterial sensors remain suboptimal, and traditional metamaterials are often single-function, capable of detecting analytes only in specific environments, which limits their broader applicability. To overcome these challenges, dual-nominal tunable materials can enhance sensor adaptability, thereby expanding the application range and flexibility of metamaterial sensors. This study introduces a novel, highly sensitive, and multifunctional terahertz metamaterial sensor based on indium antimonide (InSb) and graphene, capable of detecting physical quantities such as refractive index, temperature, and magnetic field, thereby improving the versatility and adaptability of terahertz sensing technology. Methods To design a high-sensitivity, multifunctional terahertz metamaterial sensor, we combined InSb and graphene to exploit their unique properties. InSb, a compound semiconductor, experiences significant changes in its dielectric constant under external stimuli such as magnetic fields and temperature variations. Graphene, with its adjustable Fermi level, offers dynamic electrical tunability. The sensor consists of a graphene layer, an InSb dielectric layer, and a metal reflective layer. The sensor's performance was optimized using COMSOL Multiphysics for simulation and theoretical analysis. The response of the sensor to various physical quantities such as refractive index, temperature, and magnetic field was systematically studied. This design enhances the sensor's sensitivity and dynamic adjustability, overcoming the limitations of traditional single-function sensors and improving their adaptability and application in the terahertz domain. Results and Discussions The THz transmission characteristics of the sensor are numerically calculated using COMSOL Multiphysics. The simulation results reveal that at 3.20 THz and 3.99 THz, the sensor's absorption rate reach 99.27 degrees o and 97.96 degrees o, respectively, achieving ideal absorption of double narrow bands. The relationship between geometric parameters and performance is studied to evaluate the sensor's stability under structural changes. Additionally, the Fermi level of graphene within the sensor's structure adjusts, altering its conductivity. This allows the voltage to be tuned to any resonant peak, enabling high-sensitivity sensing. To examine the sensor's refractive index sensing capabilities, we observed how the absorption spectrum shifts with changes in the environmental refractive index. When the refractive index varied from 0.9 to 1.3, the absorption peaks exhibit a significant red shift, confirming the device's ability to sense refractive index. The sensor's refractive index sensitivity is calculated as 830 GHz/RIU and 510 GHz/RIU for the A and B peaks, with peak A demonstrating the highest sensitivity. Furthermore, temperature-induced frequency shifts are observed, with the resonant frequencies moving to higher values as the temperature increased from 200 K to 300 K, demonstrating the sensor's temperature sensitivity. The device also exhibits strong sensitivity to magnetic fields, with new resonant peaks emerging upon the application of a magnetic field. At magnetic field intensities ranging from 1.1 T to 1.5 T, a new resonant peak (C) appears at 2.09 THz, with its frequency shifting significantly towards higher values as the magnetic field increases. The magnetic field sensitivity of peak C is calculated as 1700 GHz/T. Compared to recent work, this sensor's ability to dynamically adjust resonant frequencies through electrical, thermal, and magnetic stimuli provides enhanced flexibility and adaptability, enabling multi-physical field sensing. The sensor demonstrates superior refractive index sensitivity, Q-factor, and overall performance. Conclusions A terahertz metamaterial sensor capable of multi-physical field sensing is designed based on the thermal and magnetic sensitivity of InSb and the electrical tunability of graphene. This design allows the sensor to detect various physical quantities, such as refractive index, temperature, and magnetic field, without requiring structural changes. Theoretical simulations show that the sensor's refractive index sensitivity reaches 830 GHz/RIU, its Q-factor is 64, and its magnetic field sensitivity is 1700 GHz/T. The sensor's sensing curve exhibits greater steepness and higher sensitivity compared to traditional terahertz metamaterial sensors. This design offers a new approach for developing multifunctional terahertz metamaterial devices, paving the way for new applications in safety detection, material performance research, and sensor detection.

Rechargeable zinc–air batteries (ZABs) offer high energy density, intrinsic safety, and low cost, yet their performance is limited by sluggish oxygen reduction and evolution reactions (ORR/OER). These reactions cause the accumulation of oxygenated intermediates, leading to active-site blockage, catalyst degradation, and compromised long-term stability. Accelerating reaction kinetics while facilitating the dynamic evolution of reaction intermediates is therefore critical for durable ZABs. Here, we report a device-integrated magnetic field strategy to address these limitations. Neodymium‑iron‑boron (NdFeB) magnetic particles are incorporated into a nickel single-atom catalyst supported on carbon nitride, constructing a magnetic environment directly within the operational ZAB device. This device-integrated magnetic field modulates the spin states of Ni active sites, accelerates ORR/OER kinetics, and facilitates the dynamic evolution of surface reaction intermediates, mitigating active-site blockage. Applied in both button-type and flexible ZABs, NiSAs-Mag exhibits enhanced electrocatalytic activity, robust cycling stability, and practical device compatibility. In situ Raman spectroscopy reveals that the integrated magnetic environment facilitates dynamic intermediate evolution while suppressing their accumulation, providing mechanistic insight into spin-state regulation and the dynamic evolution of intermediates. This work establishes a device-compatible approach for magnetic-field-assisted electrocatalysis, offering a new design paradigm for durable, high-activity catalysts in practical energy devices.

Magnetic heating by alternating magnetic field (AMF) is a fascinating solution to break the bottleneck in oxygen evolution reaction (OER) catalyst improvement. However, practical applications of AMF in electrochemistry are always impeded by the inherent characteristics of the catalyst (i.e., non-magnetic nature and oxidizable feature). Here, a self-heating working electrode substrate of C/Fe3O4/C is proposed to be fabricated, on which non-magnetic Ru nanoparticles confined within the amorphous carbon matrix are deposited as the catalytic layer. Under AMF, magnetic Fe3O4 particle can be stimulated and generate the magnetic heating associated with Néel relaxation, which improves the OER efficiency of Ru nanoparticles with the overpotential at 10 mA cm−2 reduced by 72 mV. Together with the high stability rendered by confined structure, the exploitation of AMF on non-magnetic catalyst is confirmed, and the developed strategy offers a general pathway to advance OER catalyst performance in the future.

Inspired by the design concept of negative curvature hollow-core fibers, this paper presents an innovative negative curvature suspended-core THz fiber. Compared to traditional suspended-core fibers, all structural units of this fiber are designed with circular boundaries, effectively avoiding the issues of insufficient mechanical strength and manufacturing difficulties associated with the wide and ultra-thin rectangular support arms in traditional structures. The numerical simulation using the full-vector finite element method shows that the optical fiber loss is as low as 0.0868dB/cm (0.02cm-1) in 0.4-0.9THz, and the low loss bandwidth is 0.43THz. In addition, by adjusting the structural parameters of the fiber, near zero flat dispersion of -0.15-0.05 ps/THz/cm can be achieved in the range of 0.4-0.9 THz. The fiber exhibits excellent characteristics of low loss, wide bandwidth, and low dispersion, theoretically opening a new research path for the design of low loss THz fibers. This will provide important component support for the application and development of THz technology in fields such as communication, sensing, and imaging.

A full stack strategy, including facilitating the capture of CO2 molecules on catalysts, regulating intermediates, and releasing products, is highly needed to break the bottleneck for CO2 electroreduction to CO. The electric field is expected to promote capture of CO2, reduce energy barriers of reaction, and efficiently release CO, boosting the overall CO2 reduction reaction (CO2RR) activities. In this work, ZnO/Cu2S PN-junctions with a built-in electric field were fabricated. Kelvin probe force microscopy measurements confirmed that the presence of the built-in electric field facilitates the adsorption of more CO2 molecules onto the catalyst surface. Furthermore, theoretical calculations and electrochemical testing demonstrated that the built-in electric field lowers the reaction energy barrier and effectively modulates the reaction intermediates, contributing to enhanced catalytic performance. This work provides a full stack strategy to improve CO2RR performance and thinking for gas-fed catalytic reactions.

A dual-functional polarization converter designed for both reflective polarization conversion and asymmetric transmission in the terahertz band is proposed, leveraging the phase transition of vanadium dioxide. In its metallic state, vanadium dioxide facilitates reflective mode operation. Simulation results demonstrate that the polarization conversion rate exceeds 90%, converting linearly polarized or circularly polarized waves into crosspolarized waves, with relative bandwidths of 100.6% and 100.8%, respectively. Experimental validation confirms the polarization conversion capabilities of the device. In the insulating state of vanadium dioxide, the converter demonstrates a notable asymmetric transmission effect for wide-angle incident circularly polarized waves. The proposal of this converter fills the gap of switchable polarization conversion and asymmetric transmission functions, and has broad application prospects in multifunctional polarization devices and multichannel polarization detection.

The conventional Pancharatnam-Berry (PB) phase modulation can achieve phase modulation of polarised waves across a wide bandwidth by rotating the structural angle. However, its wide bandwidth can be inefficient for practical applications that require precise frequency band utilization. In this research, we present a novel approach to achieve PB phase modulation at specific frequency points in full space by implementing local structural rotation, based on the time-domain coupled-mode model. Our findings demonstrate that while rotating the entire unit structure exhibits PB phase characteristics across the 0-1.5 THz range, selectively rotating the outer ring results in PB phase modulation exclusively at 0.975 THz, and rotating the inner ring produces similar effects only at 1.44 THz. This innovative modulation method significantly enhances the applicability and efficiency of PB phase modulation in practical scenarios, opening up new possibilities for multi-channel communication, optical encryption, and adjustable focal-length superstructured lenses.

A simple-structured total internal reflection terahertz filter based on a microstructured optical fiber is proposed in this paper, consisting of two non-uniform thickness dielectric tubes symmetrically nested within an outer cladding. The investigation uses the finite element method and the simulation results show that the x-polarized fundamental mode (XPFM) is well confined within the fiber core, while the lowest-loss higher-order mode (LL-HOM) exhibits significant loss, and y-polarized fundamental mode (YPFM) exhibits even greater loss. Specifically, the loss difference between the XPFM and the LL-HOM is 15.39 dB/cm at 1 THz. After a 2 cm transmission length, the LL-HOM achieves an extinction ratio of 30 dB, while the insertion loss of the XPFM is only 0.67 dB. Furthermore, when the length of the filter is fixed at 4.1 cm, stable single-mode transmission of the XPFM is maintained over the frequency range from 0.755 THz to 1.075 THz, with the insertion loss of the XPFM remaining below 1.5 dB. The proposed filter demonstrates excellent fabrication tolerance and holds significant potential for applications in terahertz systems.

This paper proposes a single-mode polarization beam splitter (PBS) based on dual-hollow-core anti-resonant fiber (DHC-ARF). A glass dielectric layer is introduced through the center of hollow-core anti-resonant optical fiber with nested tubes. Due to the thickness of the glass dielectric layer being between the resonant and anti-resonant thicknesses, it is partially transmissive to the operating wavelength. The two fiber cores are separated by the glass dielectric layer, and the operating modes can be coupled from one core to the other through this glass dielectric layer. The influences of various parameters of DHC-ARF on coupling length, coupling length ratio, polarization extinction ratio, and high-order mode extinction ratio were analyzed using the finite element method. By adjusting the size of the cladding tube, an extremely short coupling length can be obtained and single-mode performance can be effectively achieved. The data results indicate that the polarization extinction ratio of 5.96 mm PBS is greater than 20 dB in the wavelength range of 1545.8-1553.8 nm. The high-order extinction ratio is greater than 100 in the wavelength range of 1544.25-1554.55 nm. These results demonstrate the potential of our PBS design in meeting the increasing demand for integrated optical devices in communication systems.

This study investigates a metallic metasurface with $\mathrm{C} 4_{\mathrm{v}}$ symmetry that supports dual quasi-bound states in the continuum(QBICs), exhibiting Fano and electromagnetically induced transparency (EIT)-like resonances under normal incidence. By introducing controlled translational symmetry protection in a tetramer unit composed of four rectangular copper rings, we simultaneously excited two high-Q QBIC modes at 0.825 THz and 1.016 THz. Full - wave simulations reveal a linear relationship between the quality factor (Q -factor) and the inverse square of $\alpha\left(\mathrm{Q} \propto \alpha^{-2}\right)$, confirming the suppression of radiation loss through symmetry-protected bound states. Multipole decomposition reveals the dominance of the electric quadrupole moment in both modes. The structure demonstrates excellent frequency stability and mechanically tunable Q-factors, enabling dual-band operation with distinct resonance line shapes. These findings establish a paradigm for ultra-thin, reconfigurable photonic platforms, with significant potential for applications in multi-channel terahertz filtering, refractive index biosensing, and compact nonlinear light sources.

The surface defect and interfacial states in nanoparticles have strong carrier trapping capacity and are closely related to the charge storage capacity and life of nanoparticles memory devices. In this work, solid and hollow CoO nanoparticles confined in amorphous HfO2 high dielectric thin film with similar size and density were synthesized and characterized, and the effect of interfacial state regulation of nanoparticles on charge storage performance of memory capacitors was studied by comparing the experimental data of the two samples. A larger memory window was observed in the memory capacitor based on hollow CoO nanoparticles comparing to the solid one, which is attributed to an abundant of defects originated from the surface and grain boundaries of CoO nanoparticles with hollow structure. Artificially controlling surface defects and interface states of nanoparticles from the nano-floating gate memory is of great significance in the development of memory devices.

The electrocatalytic reduction of CO2 to multicarbon (C2+) products is of great importance but still faces challenges. The moderate oxidation state of Cu (Cu delta+) plays a critical role in promoting the C-C coupling, thereby enhancing the Faraday efficiency (FE) for C2+ products. However, Cu delta+ active species are unstable during the reaction. In this work, two-dimensional (2D) Cu-phenylalanine (Cu-phe) nanoflakes by assembling Cu ions and phenylalanine are prepared. X-ray absorption spectroscopy (XAS) is performed to confirm the moderate oxidation state and Cu-O/N coordination of Cu-phe nanoflakes. Owing to the carboxylic ligand and more stable Cu-N coordination, Cu-phe nanoflakes maintain a moderate oxidation state and exhibit high FE for C2+ products (88.1% at -0.8 V) in a flow cell, along with excellent stability. This work offers valuable insights for designing stable and efficient catalysts for the electro-conversion of CO2 into high-value chemical stocks.

Understanding the relationship between magnetic structures (magnetic domains and domain walls) and enhanced activity is crucial for elucidating the mechanism behind magnetic field-assisted oxygen evolution reaction (OER). In this work, two-dimensional CoSe2 nanosheets with room-temperature ferromagnetic properties and structural stability were synthesized using chemical vapor deposition. Electrochemical measurements suggest that OER performance of CoSe2 nanosheets is improved under a 200 mT magnetic field, with the overpotential at 10 mA cm−2 reduced by 81 mV. Moreover, magnetic force microscopy observations on CoSe2 nanosheets reveal that spin disorder in the magnetic domain wall region transforms to spin order under the 200 mT magnetic field, resulting in improved OER performance. Although the magnetic field has a negligible effect on the OER performance of single-domain CoSe2 nanosheets, these findings reveal the decisive role of magnetic domain walls in enhancing OER performance under an applied magnetic field, pointing to the potential for industrial applications of magnetic field-assisted catalysis.

In situ studies of the relationship between surface spin configurations and spin-related electrocatalytic reactions are crucial for understanding how magnetic catalysts enhance oxygen evolution reaction (OER) performance under magnetic fields. In this work, 2D Fe7Se8 nanosheets with rich surface spin configurations are synthesized via chemical vapor deposition. In situ magnetic force microscopy and Raman spectroscopy reveal that a 200 mT magnetic field eliminates spin-disordered domain walls, forming a spin-ordered single-domain structure, which lowers the OER energy barrier, as confirmed by theoretical calculations. Electrochemical tests show that under a 200 mT magnetic field, the OER overpotential of multidomain Fe7Se8 nanosheets at 10 mA cm-2 decreases from 346 mV to 259 mV, while the magnetic field has minimal effect on single-domain nanosheets. These findings highlight the critical role of spin configurations in enhancing electrocatalytic performance, offering new insights into the design of magnetic catalysts for industrial applications.

Electromagnetic metasurfaces exhibit remarkable scattering effects that enable precise modulation of electromagnetic waves. Bound-states in the continuums (BICs) are able to confine the electromagnetic energy to a localized region without high radiative losses and therefore exhibit ultra-high quality (Q) factor resonances. This study presents a novel approach to achieving dual BICs within metallic metasurfaces, enabling the confinement of electromagnetic energy with minimal radiative losses and ultra-high factor resonances. We demonstrate that dual quasi-BIC (QBIC) with stable resonance frequencies can be realized by breaking translational symmetry while preserving C-2 symmetry. Importantly, BICs derived from both Fano resonance and electromagnetically induced transparency (EIT) can coexist at distinct frequencies. The design features a dimer structure in the metal metasurface, where the resonance point shows minimal dependence on the shape of the metal sheet. The resonance frequency of the QBIC can be effectively tuned by adjusting the periodicity, while the Q factor is modifiable through changes in the relative positioning of the metal sheets. Our findings indicate significant potential for high-Q factors and exceptional slow-light effects, paving the way for the development of high-performance filters, sensors, and modulators in terahertz applications.

The surface spin configuration of catalysts is crucial for spin-dependent catalysis, as electrochemical reactions predominantly occur at the solid-liquid interface. This configuration influences reaction efficiency by altering the spin states of intermediates. Thus, identifying the surface spin configuration is essential for understanding the mechanisms affecting catalytic activity. This work designs multidomain and single-domain Fe7S8 nanosheets through thickness control. Under a 200 mT magnetic field, the multidomain sample transitions to a single-domain state, while the surface spin configuration of the single-domain sample remains unchanged, as observed via magnetic force microscopy. Electrochemical tests show that a saturated magnetic field of 200 mT reduces the overpotential of the multidomain sample from 306 to 240 mV at 10 mA cm-2, while the single-domain sample maintains an overpotential of 257 mV. These results demonstrate that spin disorder at magnetic domain walls limits spin selectivity during the OER, suggesting strategies for developing innovative spin-selective catalysts.