Articles in 2020

Since the interfacial effect has been commonly understood to be generated entirely at the boundary between the two atomic layers, the strength of the interfacial effect has been considered independent of the thickness of each layer. In this study, contrary to the common concept, we show that the interfacial phenomenon requires threshold thickness for full emergence and is suppressed when it is too thin, by providing the result of the peculiar ferromagnet layer thickness dependence of the Dzyaloshinskii-Moriya interaction (DMI). Our result refines conventional perspectives on interfacial phenomena and provides the optimum thickness to maximize DMI for technological applications.

Very efficient, fast and scalable Fluidized Bed Reactor Atomic Layer Deposition (FBR-ALD) of highly dense and uniform Pt nanoparticles (NPs) on the functionalized carbon were successfully demonstrated for the proton exchange membrane fuel cell (PEMFC) application. The textural properties, functional groups and structural defects of the carbon supports significantly influenced Pt NPs deposition. A proper carbon supporter matching for FBR-ALD of Pt resulted in excellent electrochemical properties, long-term durability and fuel cell performance.

A germole-containing π-conjugated polymer is prepared from the corresponding tellurophene-containing polymer by its Te–Li exchange reaction using n-butyllithium followed by the reaction with dimethylgermanium dichloride. The low-lying LUMO energy level of the germole-containing π-conjugated polymer is also described.

The fiber membrane prepared from silk fibroin was modified by polydopamine and grafted the liposomes encapsulated leptin that endow the fiber with vascularization. The fiber membrane was covered with the defect of oral mucosa in rabbits, and leptin was released from the broken liposomes to promote early vascularization and accelerate the regeneration of mucous membrane.

The structure of a high-temperature non-glass forming liquid Er₂O₃ was investigated by a combination of density measurements in the International Space Station and synchrotron X-ray diffraction measurements utilizing levitation techniques with the aid of computational and advanced mathematical analyses. These multidisciplinary approaches revealed that unusually sharp diffraction peak in the liquid is originated from the formation of distorted tetraclusters whose homology is similar to that of the crystalline phase.

Using a combination of angle-dependent spectroscopic ellipsometry and angle-resolved photoemission spectroscopy as a function of temperature and supported by first-principles calculations, we reveal a new pair of correlated plasmonic excitations at 1.04 and 1.52 eV and a significant Fermi level shift of 0.12 eV, accompanied by spectral weight transfer in the topological insulator, Bismuth Selenide (Bi₂Se₃). Interestingly, such a spectral weight transfer over a broad energy range causes a drastic change in the charge-carrier density whereby the contribution of charge-carriers in the bulk starts to rival those in the surface states and Bi₂Se₃ becomes more uniformly conducting.

An electrically tunable photonic band gap structure of monodomain blue phases shows the wide tunable band gap range of ~241 nm. A novel chiral monomer enables us to stabilize the blue phases and to induce electrostriction upon biased electric fields. This device also exhibits a color gamut 85% of NTSC with high color purity owing to narrow bandwidth of 31 nm.

Non-destructive ultrafast control of magnetic vortices by a simple sequence of time asymmetric electric-field pulses.

Magnetic refrigeration, which is based on the magnetocaloric effect (MCE), is an emerging pathway for environment-friendly refrigeration. In this work, we performed a machine learning based approach to discover experimentally that HoB₂ exhibits |ΔS_M| = 40.1 J/kg K (0.35 J/cm⁻³ K) for μ₀ΔΗ = 5 Τ at second order transition of T_C ~ 15 K, having the largest |ΔS_M| around this temperature region. Thus, HoB₂ is a highly suitable material for hydrogen liquefaction and low-temperature magnetic cooling applications. Our study also sheds light on the machine learning approach as an effective method for searching functional materials characterized by complex physical properties.

Precise control of colloidal-semiconductor-quantum-dots (CQD) assembly morphologies and the related carrier transport characteristics are vital to advance their utilisations. Each application requires different assembly types to exploit either the quantum confinement effect or the large surface-to-volume ratio. On-demand control of CQD-solids‘ morphology are demonstrated using variety of assembly methods. Employment of the electric-double-layer gating on varieties of CQD solids reveals their intrinsic carrier transport and accumulation characteristics. Compact superlattice structure shows high conductivity, and the hierarchical porous assembly exhibits high carrier accumulations. These flexibilities in assembly controls and characteristic tunings signify CQD versatilities as building blocks for different modern electronics.

A low toxicity and high efficiency nucleic acid delivery system is the key to the successful implementation of gene therapy. In this study, a novel fluorinated polycationic carrier was used to effectively inhibit tumor growth by targeting VEGF genes with RNAi technology based on its unique fluorine effect, providing a feasible strategy for future clinical solid tumor treatment.

A submicron structure strategy was introduced in a selective laser melted (SLM) Ag-Cu-Ge alloy, showing semi-coherent precipitates distributed in a discontinuous but periodic fashion along the cellular boundaries. It leads to a remarkable strength of ~410 MPa with ~16% ductility, well surpassing the strength-ductility combination of their cast counterparts. The hierarchal SLM microstructure and high density of internal defects leading to a high strain hardening rate and strong strengthening. Premature failure occurred due to the external defects, such as pores and unmelted particles. This work paves a way for additively manufacturing materials towards high strength–ductility synergy.

The polyurethane–antimony tin oxide (PU–ATO) composite fibers makes infrared (IR) radiations emitted by an object to be as similar as possible to ambient background radiation such that an IR detection sensor fails to distinguish the target object. Hydrophobic surface of the PU–ATO composite fiber prevent the distortion of the IR and thermal radiation caused by the wetting of the PU–ATO composite fiber with water. The PU–ATO composite fiber-based textile can be applied in wearable IR- and thermal radiation-shielding technologies to shield IR signals generated by objects of diverse and complex shapes.

A data-driven approach, called materials informatics (MI) method, is developed to maximize the inference ability even using a small training dataset. The idea is to use a joint representation with the three descriptors to describe physical and chemical multifaceted perspectives of materials. This ensemble-based machine learning was trained with only 29 training data. Experiments confirmed that the virtual-screening process successfully discovered five oxygen-ion conductors, that have not been reported.

Initiations of magnetic reversals can be described by microstructures of the hot-deformed permanent magnet. Strong dipole fields are applied at magnetic-nucleation sites. Inclinations of easy axes from a nominal easy axis are essential to generate the magnetic nucleation. The magnetization reversal tends to starts from regions in which the grains having tilted easy axis are concentrated. The results of this study show that the performance of the hot-deformed permanent magnet is enhanced by avoiding the concentration of the grains with the tilted easy axis.

In this work, we prepared laser-scribed graphene/LiNi_1/3Mn_1/3Co_1/3O₂ (LSG/NMC) without binder and conductive agent as a new breakthrough cathode through DVD burner. The obtained LSG/NMC delivers not only high capacitance but also rate capability and cyclability. This is because the NMC spacer maximizes the effective area of LSG. This work demonstrates that LSG/NMC cathode can be regarded as a candidate for high-performance hybrid supercapacitor.

Existing healing experiments on self-healing bulk materials typically rely on manual contact of fracture interfaces. Development of 3D-architected lattice structures that can autonomously heal fractures or damages is still an outstanding engineering challenge. This paper presents a class of additively manufactured lattice structures that can autonomously heal fractures by first aligning fracture interfaces through a shape-memory process and then repairing fracture interfaces through a fracture-healing process. Through harnessing the coupling of shape-memory and self-healing, this paper also demonstrates reversible configuration transformations of lattice structures among states of different stiffnesses, vibration transmittances, and acoustic absorptions.

In this paper, the authors present an ultrathin compound metamaterial coat that could make underwater objects simultaneously invisible from the detection of both magnetic field and acoustic wave. The robustness of the methodology to realize this dual functional coat has been verified experimentally in various electromagnetic and acoustic frequency bands.

In this study, we designed an injectable antibacterial hydrogel that was photopolymerized by visible light for the treatment of skin infections. The hydrogel consists of γ-poly(glutamic acid)-glycidyl methacrylate (γ-PGA-GMA) and ε-polylysine-glycidyl methacrylate (ε-PL-GMA). The hydrogels showed the characteristics of injectable and rapid gels, and were easy to use. Importantly, the hydrogels demonstrated high levels of antibacterial activity and biocompatibility. In in vivo infection models, the hydrogels reduced inflammation, promoted wound healing, and shortened the healing time. This highlights the hydrogels as promising candidates for anti-infection and wound healing.

Collective phenomena, such as charge/spin density waves and superconductivity, may change abruptly at the surface or in single layers of layered materials, whose observation may be affected by epitaxial strain. In Niobium diselenide, a stripe charge density wave, in place of a usual triangular one, has been observed at the surface, but not in single-layer. Phonon calculations and total energy calculations shed light on the intrinsic nature of the periodic lattice distortions, finding good agreement with experimental observations of phase separation between triangular and stripe phases, attributing to isotropic compressive strain the emergence of the latter.