Research articles

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  • X-ray magnetic tomography measurements were performed on an advanced high-coercivity Nd-Fe-B permanent magnet, and three-dimensional (3D) magnetic domain structure was successfully obtained along the magnetic hysteresis curve. Furthermore, scanning electron tomography measurement was adopted to obtain 3D microstructure for the same observing volume. By comparing these two types of 3D images, we found various critical behaviors of magnetic domains inside the magnet, which are essential to understand the microscopic coercivity mechanism of permanent magnets.

    • Makoto Takeuchi
    • Motohiro Suzuki
    • Satoshi Okamoto
    Article Open Access
  • Though collinear-type antiferromagnets are fundamental building blocks of antiferromagnetic (AFM) spintronics, the potential utilization of non-collinear-type antiferromagnets for spintronic functionality has not been elucidated thus far. Here we suggest an AFM helimagnet of EuCo2As2 as a novel spintronic material, revealing an unconventional sign-changing behavior of anisotropic magnetoresistance. This contrast arises from electrically distinctive dual magnetic phases. Further, various AFM memory states regarding magnetic-phase evolution were identified by combining experimental and theoretical results. Our findings based on a unique type of AFM order are useful for the development of AFM spintronics, which has been driven by new materials.

    • Jong Hyuk Kim
    • Hyun Jun Shin
    • Young Jai Choi
    Article Open Access
  • Potassium acetate (KAc) has desirably both a high solubility and a salting-out effect on polyvinyl alcohol (PVA). The freezing temperature of 50 wt% KAc solution can reach as low as −70 °C. The hydrogels soaked in 50 wt% KAc solution exhibit the highest mechanical properties with an ultimate stress of 8.2 MPa and toughness of 25.8 MJ/m3, surpassing most reported results for anti-freezing gels. At 50 wt% KAc, the hydrogels also present a high conductivity of 8.0 S/m at room temperature and 1.2 S/m at −60 °C.

    • Shuwang Wu
    • Ta-Wei Wang
    • Ximin He
    Article Open Access
  • We report a new type of mesh electrode based on metal/oxide-based elastic films such as indium zinc oxide (IZO) with high transparency and low diffraction for highly stretchable organic light-emitting diodes (SOLEDs). Furthermore, the electrical, optical, and mechanical performances of the IZO mesh electrode are further enhanced by incorporating island-shaped Ti nanoparticles beneath the IZO mesh [i.e., 22 Ω/sq., 92% at 480 nm, mechanical stability under 100% strain and 1000 endurance cycles]. TADF-based blue SOLED with the proposed Ti-embedded IZO mesh electrode exhibits a stable operation with a high external quantum efficiency of 13.2% and a 100% stretchability.

    • Tae Hoon Park
    • Wanqi Ren
    • Tae Geun Kim
    Article Open Access
  • We propose a gravity-assisted rotatory drawing method to fabricate multicolor lasing microfibers, and weave them into flexible textiles. Through regulating the doped dyes and solution viscosity, full-color tunable lasing textiles can be achieved. Furthermore, nanoparticle patterns are printed on the lasing textile to encrypt it for anticounterfeiting application.

    • Jun Ruan
    • Dan Guo
    • Tianrui Zhai
    Article Open Access
  • Self-propelled amorphous, cubic, and tetrahedral Ag3PO4 micromotors were synthetized using a scalable precipitation method for antibacterial applications. Their programmable morphologies exhibited different motion properties under fuel-free and surfactant-free conditions and visible light irradiation. Differences in these motion properties were observed according to morphology and correlated with photocatalytic activity. Ag3PO4 micromotors are inherently fluorescent. The as-prepared self-propelled particles exhibited morphologically dependent antibiofilm activities toward eradication of gram-positive and gram-negative bacteria.

    • Daniel Rojas
    • Michaela Kuthanova
    • Martin Pumera
    Article Open Access
  • We first show through computational simulations and experiments that mechanochromic molecules, spiropyrans (SPs), were activated by force in Diels–Alder (DA) reaction-based CANs. Owing to the mechanochromic SP molecules and thermally reversible DA networks, these thermosets indicated damage with colour and fluorescence signals and autonomously repaired it with thermal treatment. While maintaining high solvent resistivity and good mechanical performance, they were reprocessed up to fifteen times without degrading the mechanical, damage-reporting, and self-healing properties.

    • Subin Yoon
    • Jong Ho Choi
    • Tae Ann Kim
    Article Open Access
  • Glasses are non equilibrium materials that develop by cooling of a supercooled liquid, where the rapidly increasing viscosity results in a kinetic arrest of long range atom rearrangements. During heating from glass state, different relaxations are thermally activated and display different relaxation spectrum. Here, we used one ultrafast nanocalorimetry to examine the evolution of multiple relaxations and discover the merging of the relaxation modes with increasing heating rates, resulting in step-like increases in both the supercooled liquid region and excess heat capacity. Our findings provide new insights on the evolution of the relaxation spectrum and the associated heterogeneous atomic motion.

    • Meng Gao
    • John H. Perepezko
    Article Open Access
  • Plasmonic thin-layer chromatography was developed for the separation of quantum dots (QDs) by combining plasmonic optical trapping with thin-layer chromatography (TLC). Photoexcitation of the localized surface plasmon resonance of Au nanoparticles immobilized on a TLC plate decreased the distance traveled by QDs, enabling size separation of QDs with identical compositions and sorting of QDs according to the optical properties of QDs with the same size. Optical property-based separation cannot be achieved by conventional chromatography, in which the interactions between stationary phases of chromatographs and QDs are simply based on the differences in the size or surface functionality of QDs.

    • Tsukasa Torimoto
    • Naoko Yamaguchi
    • Yasuyuki Tsuboi
    Article Open Access
  • Charge carrier modulation in graphene by proximate ferroelectricity has attracted much attention, but it was rarely successful especially for oxide ferroelectrics mainly due to uncontrolled interfacial charge traps. In this work, the device operation of field–effect transistor comprising of graphene and ferroelectric single-crystal Pb(Mg1/3Nb2/3)O3–PbTiO3 was carefully analyzed for studying the direct or indirect coupling phenomena between charge carriers in graphene and nearby ferroelectricity.

    • Nahee Park
    • Hyunkyung Lee
    • Dongseok Suh
    Article Open Access
  • Stickable light-emitting diodes (LEDs) were fabricated by selectively growing GaN micro-LEDs on a graphene sheet. Using the van der Waals interaction of the bottom graphene layer, the micro-LED/graphene heterostructures uniformly adhered to foreign graphene films. The transferred LEDs were fully operational and maintained good mechanical adhesion and electrical connections to the foreign graphene films under various bending conditions. Since the van der Waals integration method provides simple assembly processes of heterogeneous materials with negligible material compatibility issues, the LED/graphene heterostructure will be capable of integrating with various 2D devices.

    • Anuj Kumar Singh
    • Kwangseok Ahn
    • Kunook Chung
    Article Open Access
  • The effects of nanomorphologies of acceptors on the environmental stability of donor:acceptor blends were investigated. Dispersed acceptors in mixed phase accelerate the photooxidation of donor, whereas aggregated acceptors stabilize the donor, both of phenomena coinciding for blends. Furthermore, photooxidation of donor leads to significant deterioration of hole transport, which shows strong correlation with efficiency loss in donor:acceptor organic solar cells.

    • Woong Sung
    • Hansol Lee
    • Kilwon Cho
    Article Open Access
  • We developed multi-bishelled cobalt-based nanospheres with each bi-shelled structure consisting of symmetric heterogeneous configuration. This architecture features sufficient heterointerfaces and a high density of active sites benefiting from interfacial electronic modulation. When they worked as OER electrocatalysts in CO2 electrolysis, the electrochemical performance of Pd nanosheets (NSs) for CO2 reduction can be significantly enhanced in terms of product selectivity and energy input.

    • Yu Zhang
    • Penglun Zheng
    • Qingyu Yan
    Article Open Access
  • Alkaline phosphatase (ALP) is one of the most extensively distributed enzymes existed in living species, which could act as crucial prognostic indicators for various diseases. Here, we present novel hybrid photonic alginate hydrogel microparticles for ALP detection. An intermediary chemical, the pyrophosphate ion (PPi), was introduced to trigger the phase transition of the copper alginate hydrogel, while ALP can react with PPi and suppress the process. This response can be converted into dual optical readouts, a fluorescence signal and a structural color signal. Quantitative determination of ALP was established based on this dual-indicator system with high accuracy and reliability.

    • Yuetong Wang
    • Dagan Zhang
    • Yuanjin Zhao
    Article Open Access
  • We, for the first time, reveal that manipulation of microstructure enables the suppression of phase transformation and enhancement of long-term stability of Bi2O3-based ionic conductors. To investigate the microstructural influence on the stability, thin films with precisely defined grain structures are prepared. The conductivity of polycrystalline thin film decreased by 94.6% after approximately 20 h of operation, while the initial conductivity of epitaxial thin film remained almost constant during annealing for up to 100 h. This study provides novel insights for the development of highly conductive and durable solid electrolytes for next-generation energy applications.

    • Incheol Jeong
    • Seung Jin Jeong
    • Kang Taek Lee
    Article Open Access
  • Two-dimensional (2D) silicon sample consists of an airy hole array in a crystalline silicon thin film matrix was designed and fabricated with the property of phononic crystal. Significant suppression of hot carrier cooling was observed with lifetime prolongation by orders of magnitude. The present direct experimental evidence for hot carrier cooling suppression in 2D silicon phononic crystals and opens opportunities for promising applications.

    • Wensheng Yan
    • Liyuan Long
    • Guijie Liang
    Article Open Access
  • Sialylated glycans (SGs), abundant in cell membranes, play decisive roles in regulating ion channels (e.g., NaV1.4, KV1.1, CaV1.2) in life system, only when the ion channels work stably and accurately can life activities proceed normally. Here we construct a biomimetic SG-modulated nanochannel based on a smart polymer design. Carbohydrate‒carbohydrate interaction triggers globule-to-coil transition of the polymer chains, which regulated the dynamic ion gating behavior of this nanochannel, resulting in a significant reduction in transmembrane ionic current. This device exhibits excellent specificity and sensitivity in response to α-2,6-linked sialyllactose, further realizing real-time monitoring of the sialylation reaction catalyzed by α2,6-sialyltransferase.

    • Jie Xiao
    • Wenqi Lu
    • Guangyan Qing
    Article Open Access
  • In this work, a high-Tc (~117 K) joined with a high-Jc (>104 A/cm2, 100 K) are reported in the CuBa2Ca3Cu4O10+δ (Cu-1234) superconductor. Studies have shown that the ordering vacancies and platelike 90° micro-domains serve as efficient microstructure pinning centers which suppress the vortex flux flow and enhance Jc. And plenty of holes with 2pz symmetry owing to unique compressed [CuO6] octahedrons decrease superconducting anisotropy and enhance the interlayer coupling that guarantee a high-Jc.

    • Xuefeng Zhang
    • Jianfa Zhao
    • Jing Zhu
    Article Open Access