Picosecond Spin Current Generation from Vicinal Metal-Antiferromagnetic Insulator Interfaces.

We report the picosecond spin current generation from the interface between a heavy metal and a vicinal antiferromagnet insulator Cr_{2}O_{3} by laser pulses at room temperature and zero magnetic field. It is converted into a detectable terahertz emission in the heavy metal via the inverse spin Hall effect. The vicinal interfaces are apparently the source of the picosecond spin current, as evidenced by the proportional terahertz signals to the vicinal angle. We attribute the origin of the spin current to the transient magnetic moment generated by an interfacial nonlinear magnetic-dipole difference-frequency generation. We propose a model based on the in-plane inversion symmetry breaking to quantitatively explain the terahertz intensity with respect to the angles of the laser polarization and the film azimuth. Our work opens new opportunities in antiferromagnetic and ultrafast spintronics by considering symmetry breaking.

Two-Dimensional Room-Temperature Magnetism in Janus Mn2I3S3 and Cr2I3Se3 Monolayers with Tunable Magnetic Properties by Strain Engineering.

Exploring room-temperature intrinsic magnetism in two-dimensional (2D) materials for nanoscale spintronic devices has garnered significant interest. Achieving a high Curie temperature and substantial spin polarization in 2D ferromagnetic materials remains challenging. Drawing inspiration from the substantial enhancement of the Curie temperature observed in ferromagnetic CrIS monolayers by manipulating the covalent nature of Cr-S bonds, our study systematically delves into the electronic structure and magnetic properties of Janus M2X3Y3 (M = V, Cr, Mn, Fe, and Co; X = Cl, Br, I; Y = S, Se, and Te) monolayers through first-principles calculations. Our findings reveal that 15 kinds of these monolayers exhibit dynamic and thermodynamic stability while displaying diverse electronic and ferromagnetic characteristics. Notably, Mn2I3S3 demonstrates half-metallicity and in-plane magnetic anisotropy, while Cr2I3Se3 exhibits a half-semiconductor and perpendicular magnetic anisotropy. Consequently, Mn2I3S3 transforms from in-plane to perpendicular magnetic anisotropy through strain manipulation. Cr2I3Se3, under strain, transforms from a half-semiconductor to a bipolar magnetic semiconductor. The strong coupling caused by the M-Y bonds makes them have a Curie temperature higher than room temperature. The unique magnetic properties exhibited by the 2D Janus Mn2I3S3 and Cr2I3Se3 magnets hold promise for applications in spintronics. Our study provides a foundational understanding for future experimental explorations in this exciting research area.

Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in Ge1-x-yBixCayTe with Ultrafine Ferroelectric Domain Structure.

GeTe and its derivatives emerging as a promising lead-free thermoelectric candidate have received extensive attention. Here, a new route was proposed that the minimization of κL in GeTe through considerable enhancement of acoustic phonon scattering by introducing ultrafine ferroelectric domain structure. We found that Bi and Ca dopants induce strong atomic strain disturbance in the GeTe matrix because of large differences in atom radius with host elements, leading to the formation of ultrafine ferroelectric domain structure. Furthermore, large strain field and mass fluctuation induced by Bi and Ca codoping result in further reduced κL by effectively shortening the phonon relaxation time. The co-existence of ultrafine ferroelectric domain structure, large strain field, and mass fluctuation contribute to an ultralow lattice thermal conductivity of 0.48 W m-1 K-1 at 823 K. Bi and Ca codoping significantly enhances the Seebeck coefficient and power factor through reducing the energy offset between light and heavy valence bands of GeTe. The modified band structure boosts the power factor up to 47 µW cm-1 K-2 in Ge0.85Bi0.09Ca0.06Te. Ultimately, a high ZT of ∼2.2 can be attained. This work demonstrates a new design paradigm for developing high-performance thermoelectric materials.

Broadband and High-Efficiency Microwave Absorbers Based on Pyramid Structure.

Microwave-absorbing materials with wide bandwidth and high absorptivity are increasingly playing an important role in over-the-air (OTA) testing. In this work, a kind of pyramid absorbing material was prepared using flame-retardant absorbers as the filler. In addition, a coating was used to further improve the flame-retardant properties of the microwave-absorbing material. To obtain excellent microwave absorption performance (MWAP), a high-frequency structure simulator (HFSS) was adopted to design structural materials. Here, the total height, the base height, the decapitation height of the pyramid tip, the distance between the pyramids, and other parameters were analyzed; then, the actual processing and molding were realized. The MWAP of -30 dB was achieved at 2.7-18 GHz, and the MWAP of -10 dB was also met at 2-18 GHz. In particular, the study also investigated the MWAP of large angle, which can meet the MWAP of -10 dB at 2-18 GHz and MWAP of -30 dB at 4-18 GHz. Most importantly, the absorption mechanism of the pyramid structure was explored. The influence of the tip was proved by the distribution of the electromagnetic field in the pyramid. It can be regarded as a multilayer microwave-absorbing material due to the impedance gradient of the pyramid, which can provide an effective research idea and method for future engineering applications.

Does supplier concentration matter to investors during the COV1D-19 crisis: evidence from China?

The literature shows that investor attention to customer-supplier disclosure increases when suppliers' information arrival is anticipated. Due to the widespread of city lockdowns in China and the implementation of social distancing to control the COVID-19 pandemic, investor attention to potential disruption of the supply chain spikes, leading to a price devaluation for firms with high supplier concentration risk. We find that a higher degree of supplier concentration is related to more serious stock price declines over the short-term and medium-term windows right after the Wuhan lockdown. This result lends support to the argument that the concentration risk of suppliers is a significant consideration for China stock market investors, especially under the potential financial distress at the firm level induced by the COVID-19 crisis.

Enhanced interfacial polarization of biomass-derived porous carbon with a low radar cross-section.

Ultra-thin microwave absorbers have been urgently demanded for electromagnetic applications in recent years. Herein, porous carbon with a "flower cluster" microstructure was synthesized from biomass waste (mango seeds) by a facile activation and carbonization method. The novel structure reduced the density and also improved the impedance matching, dipole polarization, and provided many carbon matrix-air interfaces for interfacial polarization, resulting in superior microwave absorption performance. At an ultra-thin thickness of 1.5 mm, extraordinary microwave absorption was achieved, with a reflection loss (RL) of -42 dB. The effective absorption bandwidth reached 4.2 GHz. The RL can be further improved to -68.4 dB by adjusting the amount of activator to manipulate the structure of porous carbon. In addition, from the simulated radar scattering results, the maximum reduction in the radar cross-section (RCS) reached 30.4 dBm2, which can greatly reduce the probability of equipment being detected by radar. This work provides a low-cost and high-performance microwave absorber for electromagnetic stealth technologies.

A breathable and flexible fiber cloth based on cellulose/polyaniline cellular membrane for microwave shielding and absorbing applications.

High-performance electromagnetic (EM) wave absorption and shielding materials integrating with flexibility, air permeability, and anti-fatigue characteristics are of great potential in portable and wearable electronics. These materials usually prepared by depositing metal or alloy coatings on fabrics. However, the shortcomings of heavy weight and easy corrosion hamper its application. In this work, the cellulose nanofiber (CF) fabric was prepared by electrospinning technology. Then, conductive polyaniline (PANI) was deposited on the CF surface via a facile in-situ polymerization process. The interweaving cellulose/polyaniline nanofiber (CPF) composite constructs a conductive network, and the electrical conductivity can be adjusted by polymerization time. Benefiting from optimal impedance matching, strong conductive loss, as well as interfacial polarization, the CPF possesses excellent EM absorption performance. The minimum reflection loss (RLmin) value is -49.24 dB, and the effective absorption bandwidth (RL < -10 dB, fe) reaches 6.90 GHz. Furthermore, the CPF also exhibits outstanding electromagnetic interference (EMI) shielding capability with shielding efficiency (SE) of 34.93 dB in the whole X band. Most importantly, the lightweight CPF fabrics have the merits of mechanical flexibility, breathability and wash resistance, which is highly applicable for wearable devices.

Circular RNA circPDSS1 promotes osteosarcoma progression by sponging miR-502-3p and miR-4436a.

Osteosarcoma (OS) is a highly aggressive bone cancer. Patients with OS frequently develop drug resistance in clinical treatment, and the prognosis has not been improved significantly. There is an urgent need to identify novel markers and therapeutic targets. In this study, we focused on the highly expressed noncoding circular RNA circPDSS1 in OS, and studied its functional roles and downstream targets in OS cells by CCK-8, clone formation assay, transwell assays. Additionally, we performed luciferase reporter assay, RNA pull-down experiment and qRT-PCR to validate the micoRNA targets of circPDSS1. The involvement of circPDSS1 in tumorigenesis was also investigated in mouse xenografts model. The expression of circPDSS1 was significantly upregulated in OS tissues and cell lines. Patients with high circPDSS1 expression were associated with poorer progression-free survival (PFS) and overall survival (OS) as compared to those with low circPDSS1 expression. CircPDSS1 knockdown significantly inhibited the viability, clone formation ability and invasion ability of OS cells, and induced cell apoptosis, which were associated with the upregulation of proapoptotic proteins and the impairment of prosurvival signaling. Molecular mechanism study further demonstrated that circPDSS1 modulates OS cell functions by regulating the expression of miR-502-3p and miR-4436a. Our data suggest that circPDSS1 acts as a molecular sponge of miR-502-3p and miR-4436a regulates the proliferation and invasion of OS cells and promote the malignant progression of OS.

Synthesis of Structurally Stable and Highly Active PtCo3 Ordered Nanoparticles through an Easily Operated Strategy for Enhanced Oxygen Reduction Reaction.

Constructing robust and cost-effective Pt-based electrocatalysts with an easily operated strategy remains a crucial obstacle to fuel cell applications. Conventional Pt-based catalysts suffer from high Pt content and an arduous synthetic process. Herein, through the spray dehydration method and annealing treatment, facile producible synthesis of a small-sized (5.2 nm) low-Pt (10.5 wt %) ordered PtCo3/C catalyst (O-PtCo3/C) for oxygen reduction reaction is reported. The fast spray evaporation rate contributes to small size and uniform nucleation of nanoparticles (NPs) on carbon support. O-PtCo3/C-600 exhibits efficient electrocatalytic performance with mass activity (MA) 6.0-fold and specific activity 3.9-fold higher than commercial Pt/C. The ordered chemical structure generates superior stability with merely 3.5% decay in MA after 10,000 potential cycles. Density functional theory calculations reveal that the enhanced catalytic performance originates from rational modification of d-band through strain and ordering effect and accompanying weaker adsorption of intermediate OH. This work highlights the potentials of low-Pt PtM3-type ordered NPs for prospective fuel cell cathodic catalysis. The proposed facile and practical synthetic strategy also shows promising prospects for preparing effective Pt-based electrocatalysts.

Boosting the figure of merit of refractive index sensing via magnetoplasmon in H-shaped magnetoplasmonic crystals.

Nanoscale refractive index (RI) sensors based on plasmonic structures usually suffer from a low figure of merit (FoM) due to the broad linewidth of the resonance peaks. Here, we report a magnetoplasmon-based RI sensing method with high FoM in the designed H-shaped magnetoplasmonic crystals. Instead of the light intensity spectrum, the Faraday signal is detected to analyze the changes of the surrounding RI. Sharp resonance with extremely narrow linewidth is obtained by plotting the reciprocal Faraday rotation near the null point region. Therefore, the FoM is hugely enhanced, and a theoretical value exceeding 1775/RIU is achieved, which is one order of magnitude higher than has ever been reported, to the best of our knowledge, for the RI sensor based on the Faraday effect. The Faraday reversal and the enhanced FoM arise from the Fano resonance. These findings are of potential value for practical high performance biochemical sensors.

Structurally ordered Pt3Co for oxygen reduction reaction prepared using polyvinylpyrrolidone as auxiliary dispersant.

Structurally ordered Pt3Co/C nanoparticles (NPs) were obtained via a spray paint drying method with an annealing treatment. The addition of a suitable dose of polyvinylpyrrolidone resulted in a narrow size distribution of the Pt3Co/C-600-1 NPs, an average particle size of ca. 4.6 nm, which may be due to the enhanced dispersion in aqueous solution resulting from the carbon support. The sample denoted as Pt3Co/C-600-1 NPs performs high activity for oxygen reduction reaction with the mass activity (MA) ca. 3 times higher than that of a commercial Pt/C catalyst at 0.9 V. Accelerated durability tests (ADTs) showed that Pt3Co/C-600-1 NPs exhibit superior stability with a minimal loss of 17.5% in MA at 0.9 V after 5000 cycles, while Pt/C catalysts show loss of 44.4%. This simple two-step strategy provides an effective way to prepare Pt-based catalysts for industrial application.

Facile Synthesis of Quaternary Structurally Ordered L12-Pt(Fe, Co, Ni)3 Nanoparticles with Low Content of Platinum as Efficient Oxygen Reduction Reaction Electrocatalysts.

Synthesis of electrocatalysts for oxygen reduction reaction (ORR) with not only prominent electrocatalytic performance but also a low amount of Pt is the urgent challenge in the popularization of fuel cells. In this work, through a facile synthetic strategy of spray dehydration on a solid surface and annealing process, we demonstrate the first manufacture of quaternary structurally ordered PtM3 (M = transition metal) intermetallic nanoparticles (NPs), Pt(Fe, Co, Ni)3, in order to lower the content of Pt. The atomic contents of Pt, Fe, Co, and Ni are equal and the chemical structure of Pt(Fe, Co, Ni)3 is a cubic L12-ordered structure. L12-Pt(Fe, Co, Ni)3/C electrocatalysts exhibit enhanced electrocatalytic performance toward ORR with mass activity (MA) 6.6 times higher than the commercial Pt/C and a minimal loss of 17% in MA and 1.5% loss in specific activity (SA) after 10 000 potential cycles at 0.9 V. Furthermore, the stability behavior is confirmed to be attributed to the coaction of particle sizes and the ordering effect. Compared with traditional Pt-based electrocatalysts in the stoichiometric forms of Pt3M and PtM, L12-Pt(Fe, Co, Ni)3 intermetallic NPs exhibit excellent performance and higher cost effectiveness. Moreover, this work also proposes a facile and effective synthetic strategy for manufacturing multicomponent Pt-based electrocatalysts for ORR.

P-Superdoped Graphene: Synthesis and Magnetic Properties.

Phosphorus (P)-doping in vacancies of graphene sheets can significantly change graphene's physical and chemical properties. Generally, a high level for P-doping is difficult due to the low concentration of vacancy but is needed to synthesize graphene with the perfect properties. Herein, we synthesized the P-superdoped graphene with the very high P content of 6.40 at. % by thermal annealing of fluorographite (FGi) in P vapor. Moreover, we show that the P-doping level can be adjusted in the wide range from 2.86 to 6.40 at. % by changing the mass ratio of red phosphorus to FGi. The magnetic results show that (i) P-doping can effectively create localized magnetic moments in graphene; (ii) the higher the doping level of sp3-type POx groups, the higher the magnetization of P-superdoped graphene is; and (iii) the high P-doping levels can lead to the coexistence of antiferromagnetic and ferromagnetic behavior. It is proposed that the sp3-type POx groups are the major magnetic sources.

Tuning the magneto-optical Kerr effect by the nanograting cross section.

The magneto-optical Kerr effect, especially the Kerr slope, is of great significance to magneto-optical devices. Herein, we developed a method to tune the magneto-optical effect by the nanograting cross section. Both the simulation and experiment confirm that the resonance strength of the plasmon can be modulated by the nanograting cross section, resulting in the large Kerr slope and Kerr rotation. By designing the nanograting cross section, we obtained the Kerr slope of 0.397°/nm, which is 4 orders of magnitude higher than the reported results. And the Kerr rotation of the magnetic nanograting reaches up to 1.218°, which is 24 times higher than the flat Co film. Such a huge enhancement on the Kerr slope and the Kerr rotation may have profound applications in magneto-optical devices in the future.

Ultrafast Orbital-Oriented Control of Magnetization in Half-Metallic La0.7 Sr0.3 MnO3 Films.

Manipulating spins by ultrafast pulse laser provides a new avenue to switch the magnetization for spintronic applications. While the spin-orbit coupling is known to play a pivotal role in the ultrafast laser-induced demagnetization, the effect of the anisotropic spin-orbit coupling on the transient magnetization remains an open issue. This study uncovers the role of anisotropic spin-orbit coupling in the spin dynamics in a half-metallic La0.7 Sr0.3 MnO3 film by ultrafast pump-probe technique. The magnetic order is found to be transiently enhanced or attenuated within the initial sub-picosecond when the probe light is tuned to be s- or p-polarized, respectively. The subsequent slow demagnetization amplitude follows the fourfold symmetry of the d x 2 - y 2 orbitals as a function of the polarization angles of the probe light. A model based on the Elliott-Yafet spin-flip scatterings is proposed to reveal that the transient magnetization enhancement is related to the spin-mixed states arising from the anisotropic spin-orbit coupling. The findings provide new insights into the spin dynamics in magnetic systems with anisotropic spin-orbit coupling as well as perspectives for the ultrafast control of information process in spintronic devices.

Review of the Electronic, Optical, and Magnetic Properties of Graphdiyne: From Theories to Experiments.

Graphdiyne (GDY), a two-dimensional artificial-synthesis carbon material, has aroused tremendous interest because of its unique physical properties. The very high activity affords the possibility to chemically dope GDY with metal atoms or lightweight elements such as hydrogen and halogen and so on. Chemical doping has been confirmed to be an effective method to lead to various GDY derivatives with useful physical properties. Thus, this review is intended to provide an overview of the electronic, optical, and magnetic properties of pristine GDY and its derivatives reported from theories to experiments. Because of the importance of pristine GDY and its derivatives in real applications, we also summarize the main physical applications of GDY and its derivatives reported in recent years in this review. We believe that the review will be valuable to all those interested in GDY.

Enhancing the figure of merit of refractive index sensors by magnetoplasmons in nanogratings.

The sensing performance of one-dimensional magnetic nanograting based on magnetoplasmons was investigated. The predictable Kerr reversal and enhancement are achieved in our experiment. The further result shows that the shift of the Kerr null point has a linear relationship with the surrounding refractive index in a wide range. In addition, a huge figure of merit (FoM) of 1728/refractive index unit is achieved, which is 1 order of magnitude higher than the results reported. The experiment and theory confirm that the excitation of surface plasmons leads to the Kerr reversal and enhancement, resulting in a huge FoM.

Administration of chlorogenic acid alleviates spinal cord injury via TLR4/NF­κB and p38 signaling pathway anti­inflammatory activity.

Chlorogenic acid, as a secondary metabolite of plants, exhibits a variety of effects including free radical scavenging, antiseptic, anti­inflammatory and anti­viral, in addition to its ability to reduce blood glucose, protect the liver and act as an anti­hyperlipidemic agent and cholagogue. The present study demonstrated that administration of chlorogenic acid alleviated spinal cord injury (SCI) via anti­inflammatory activity mediated by nuclear factor (NF)­κB and p38 signaling pathways. Wistar rats were used to structure a SCI model rat to explore the effects of administration of chlorogenic acid on SCI. The Basso, Beattie and Bresnahan test was executed for assessment of neuronal functional recovery and then spinal cord tissue wet/dry weight ratio was recorded. The present study demonstrated that chlorogenic acid increased SCI­inhibition of BBB scores and decreased SCI­induction of spinal cord wet/dry weight ratio in rats. In addition, chlorogenic acid suppressed SCI­induced inflammatory activity, inducible nitric oxide synthase activity and cyclooxygenase­2 protein expression in the SCI rat. Furthermore, chlorogenic acid suppressed Toll like receptor (TLR)­4/myeloid differentiation primary response 88 (MyD88)/NF­κB/IκB signaling pathways and downregulated p38 mitogen activated protein kinase protein expression in SCI rats. The findings suggest that administration of chlorogenic acid alleviates SCI via anti­inflammatory activity mediated by TLR4/MyD88/NF­κB and p38 signaling pathways.

All-solid-state asymmetric supercapacitors based on Fe-doped mesoporous Co3O4 and three-dimensional reduced graphene oxide electrodes with high energy and power densities.

An asymmetric supercapacitor offers opportunities to effectively utilize the full potential of the different potential windows of the two electrodes for a higher operating voltage, resulting in an enhanced specific capacitance and significantly improved energy without sacrificing the power delivery and cycle life. To achieve high energy and power densities, we have synthesized an all-solid-state asymmetric supercapacitor with a wider voltage range using Fe-doped Co3O4 and three-dimensional reduced graphene oxide (3DrGO) as the positive and negative electrodes, respectively. In contrast to undoped Co3O4, the increased density of states and modified charge spatial separation endow the Fe-doped Co3O4 electrode with greatly improved electrochemical capacitive performance, including high specific capacitance (1997 F g-1 and 1757 F g-1 at current densities of 1 and 20 A g-1, respectively), excellent rate capability, and superior cycling stability. Remarkably, the optimized all-solid-state asymmetric supercapacitor can be cycled reversibly in a wide range of 0-1.8 V, thus delivering a high energy density (270.3 W h kg-1), high power density (9.0 kW kg-1 at 224.2 W h kg-1), and excellent cycling stability (91.8% capacitance retention after 10 000 charge-discharge cycles at a constant current density of 10 A g-1). The superior capacitive performance suggests that such an all-solid-state asymmetric supercapacitor shows great potential for developing energy storage systems with high levels of energy and power delivery.

Enhancement of magneto-optical Faraday effects and extraordinary optical transmission in a tri-layer structure with rectangular annular arrays.

The properties of optics and magneto-optical Faraday effects in a metal-dielectric tri-layer structure with subwavelength rectangular annular arrays are investigated. It is noteworthy that we obtained the strongly enhanced Faraday rotation of the desired sign along with high transmittance by optimizing the parameters of the nanostructure in the visible spectral ranges. In this system, we obtained two extraordinary optical transmission (EOT) resonant peaks with enhanced Faraday rotations, whose signs are opposite, which may provide the possibility of designing multi-channel magneto-optical devices. Study results show that the maximum of the figure of merit (FOM) of the structure can be obtained between two EOT resonant peaks accompanied by an enhanced Faraday rotation. The positions of the maximum value of the FOM and resonant peaks of transmission along with a large Faraday rotation can be tailored by simply adjusting the geometric parameters of our models. These research findings are of great importance for future applications of magneto-optical devices.