Borophene, a promising material with potential applications in electronics, energy storage, and sensors, is successfully grown as a monolayer on Ag(111), Cu(111), and Au(111) surfaces using molecular beam epitaxy. The growth of two-dimensional borophene on Ag(111) and Au(111) is proposed to occur via surface adsorption and boron segregation, respectively. However, the growth mode of borophene on Cu(111) remains unclear. To elucidate this, scanning tunneling microscopy in conjunction with theoretical calculations is used to study the phase transformation of boron nanostructures under post-annealing treatments. Results show that by elevating the substrate temperature, boron nanostructures undergo an evolution from amorphous boron to striped-phase borophene (eta = 1/6) adhering to the Cu < 1 (1) over bar0 > step edge, and finally to irregularly shaped beta-type borophene (eta = 5/36) either on the substrate surface or embedded in the topmost Cu layer. dI/dV spectra recorded near the borophene/Cu lateral interfaces indicate that the striped-phase borophene is a metastable phase, requiring more buckling and electron transfer to stabilize the crystal structure. These findings offer not only an in-depth comprehension of the beta-type borophene formation on Cu(111), but also hold potential for enabling borophene synthesis on weakly-binding semiconducting or insulating substrates with 1D active defects.

Nowadays, Fe-based microwave absorption materials still face crucial problems of poor oxidation resistance, lack of dielectric loss and narrow effective absorption bandwidth. In this work, we developed a feasible way of calcining and etching SiO2 microspheres coated Fe3+ and polydopamine (SiO2@Fe3+-PDA) to confine Fe nanoparticles (12nm) in the hollow carbon microspheres with a thickness of 17nm, which provides more interfaces and polarization sites to enhance microwave attenuation. With the increase of Fe content, the microwave absorption performance of the sample is gradually improved. When Fe content is 19.7wt.%, the sample has a minimum reflection loss (RL) of -30.9dB and a broadband absorption bandwidth (RL ≤ -10 dB) of 11.9GHz (6.1-18GHz) at the thickness of 4.0mm. The ultra-wide effective absorption bandwidth is ascribed to synergetic effect of Fe nanoparticles and carbon layer, which provide magnetic loss and dielectric loss, respectively. Moreover, the hollow structure extends the transmission path and induces the multiple scattering of the incident electromagnetic waves. The novel hollow Fe/C microspheres are promising as high-efficiency microwave absorbers with strong microwave absorption and broad absorption bandwidth.

At present, to solve the threat of electromagnetic wave (EMW) radiation pollution to human health, intelligent control and information security, tremendous efforts have been made to manufacture EMW absorbing materials. For ideal microwave absorption materials (MAMs), it is generally necessary not only to pursue strong microwave absorption (MA) over wide effective absorption bandwidth (EAB), but also to take into account the requirements of light weight, thin matching thickness and chemical stability characteristics. It has been found that magnetite (Fe3O4) is the most promising MAM to absorb and dissipate EMW among various absorbers, because of its good mechanical and chemical stability, controllable morphology, high Curie temperature, easy preparation, economy and excellent magnetic properties. However, the application performance of Fe3O4 absorber with single composition is limited by its easy agglomeration, eddy current, high density, and impedance mismatch. In addition, achieving efficient MA metrics with low absorber loading remains a huge challenge. To overcome these limitations, conjugation with dielectric carbon-based materials and special structural designs have been extensively explored as viable solutions to optimize the microwave absorption performance (MAP) of Fe3O4. This paper reviews the recent research progress of Fe3O4/carbon MAMs, and then the influence of dimensions and structures regulations on the MAPs are introduced in detail. Finally, the current existing problems and future development direction of Fe3O4/carbon composites in the field of MA are also presented.

Composites composed of ferromagnetic alloy/dielectric material have been widely studied and applied. The alloying of the two metals endows these composites with escalated magnetic loss capacity, but they are usually micro-sized, which is not conducive to further improving the absorption performance. Herein, we develop an efficient approach to synthesize Co7Fe3@C nanocomposites with particle sizes ranging from 32 to 42 nm based on the in-situ carbon coating on the FeCo2O4 precursor and subsequent carbothermal reduction procedure. The thickness of carbon coating can be effectively tailored by controlling the reaction conditions. The minimum reflection loss (RL) value of the Co7Fe3@C nanocomposite with a carbon coating of 2.5 nm goes up to-100.8 dB at only 1.7 mm thickness, and the effective absorption bandwidth (EAB) also reaches 9.9 GHz (8.1-18 GHz) at 2.0 mm. Moreover, as the carbon coating increases to 4.2 nm, the bandwidth escalates to 11.5 GHz (6.5-18 GHz) at 2.0 mm, which covers the whole X and Ku bands and half of the C band. The remarkable performance originates from the strong magnetic loss capability of the nano-sized Co7Fe3 core as well as the good impedance matching brought by appropriate carbon coating. Accordingly, the Co7Fe3@C nanocomposite is convinced to be a competent candidate among absorbers with high absorption intensity and ultra-wide broadband.

Post-combustion flue gas (mainly containing 5-40% CO2 balanced by N2 ) accounts for about 60% global CO2 emission. Rational conversion of flue gas into value-added chemicals is still a formidable challenge. Herein, this work reports a β-Bi2 O3 -derived bismuth (OD-Bi) catalyst with surface coordinated oxygen for efficient electroreduction of pure CO2 , N2, and flue gas. During pure CO2 electroreduction, the maximum Faradaic efficiency (FE) of formate reaches 98.0% and stays above 90% in a broad potential of 600 mV with a long-term stability of 50 h. Additionally, OD-Bi achieves an ammonia (NH3 ) FE of 18.53% and yield rate of 11.5 µg h-1 mgcat -1 in pure N2 atmosphere. Noticeably, in simulated flue gas (15% CO2 balanced by N2 with trace impurities), a maximum formate FE of 97.3% is delivered within a flow cell, meanwhile above 90% formate FEs are obtained in a wide potential range of 700 mV. In-situ Raman combined with theory calculations reveals that the surface coordinated oxygen species in OD-Bi can drastically activate CO2 and N2 molecules by selectively favors the adsorption of *OCHO and *NNH intermediates, respectively. This work provides a surface oxygen modulation strategy to develop efficient bismuth-based electrocatalysts for directly reducing commercially relevant flue gas into valuable chemicals.

We study genuine tripartite entanglement and multipartite entanglement in arbitrary n-partite quantum systems based on complete orthogonal basis (COB). While the usual Bloch representation of a density matrix uses three types of generators, the density matrix with COB operators has one uniformed type of generators which may simplify related computations. We take the advantage of this simplicity to derive useful and operational criteria to detect genuine tripartite entanglement and multipartite entanglement. We first convert the general states to simpler forms by using the relationship between general symmetric informationally complete measurements and COB. Then we derive an operational criteria to detect genuine tripartite entanglement. We study multipartite entanglement in arbitrary dimensional multipartite systems. By providing detailed examples, we demonstrate that our criteria can detect more genuine entangled and multipartite entangled states than the previously existing criteria.

In this paper, we investigate the genuine entanglement in tripartite systems based on partial transposition and the norm of correlation tensors of the density matrices. We first derive an analytical sufficient criterion to detect genuine entanglement of tripartite qubit states combining with the partial transposition of the density matrices. Then, we use the norm of correlation tensors to study genuine entanglement for tripartite qudit quantum states and obtain a genuine entanglement criterion by constructing certain matrices. With detailed examples, our results are seen to be able to detect more genuine tripartite entangled states than previous studies.

High-efficiency and thermal stability are two important factors of ideal microwave absorption materials (MAMs), which are becoming desired because of the more complex modern service environment. Herein, a novel quaternary magnetic core-shell-shell structure FeCo-Co@Fe3O4 @SiO2 (FCSF) has been fabricated by a facile and generic route. In this structure, the incipient oxidation temperature of magnetic core can be greatly increased from 523 K to 773 K by the Fe3O4/SiO(2 )double shells, and the multiple magnetic het-erointerfaces can generate electron transfer and spin-orbit interaction based on DFT calculations. The minimum reflection loss (RLmin) and efficient absorption band (RL < -10 dB, feff) of FCSF composites can reach up to -42.8 dB and 7.3 GHz with the thickness of 2 mm, due to the emerged electromagnetic loss mechanisms of interface polarization and exchange resonance. Moreover, owing to the optimized impedance matching and enhanced electromagnetic loss at elevated temperature, the RLmin values of FCSF at 673 K and 773 K increase by 15.4% and 41.2% compared with that at 298 K, respectively. The results de-monstrate that the FCSF composite can act as a promising candidate for high-efficiency MAMs in thermal environment, and the synthetic strategy of heterostructures in this work can also be applied to design other MAM systems. (C) 2022 Elsevier B.V. All rights reserved.

Blood vessels are one of the most essential organs, which nourish all tissues in our body. Once there are intravascular plaques or vascular occlusion, other organs and circulatory systems will not work properly. Therefore, it is necessary to detect abnormal blood vessels by intravascular imaging technologies for subsequent vascular treatment. The emergence of lasers and fiber optics promotes the development of intravascular imaging and treatment. Laser imaging techniques can obtain deep vascular images owing to light scattering and absorption properties. Moreover, photothermal and photomechanical effects of laser make it possible to treat vascular diseases accurately. In this review, we present the research progress and applications of laser techniques in intravascular imaging and treatment. Firstly, we introduce intravascular optical coherent tomography and intravascular photoacoustic imaging, which can obtain various information of plaques. Multimodal intravascular imaging techniques provide more information about intravascular plaques, which have an essential influence on intravascular imaging. Secondly, two laser techniques including laser angioplasty and endovenous laser ablation are discussed for the treatment of arterial and venous diseases, respectively. Finally, the outlook of laser techniques in blood vessels, as well as the integration of laser imaging and treatment are prospected in the section of discussions.

In the free space optical communication system, atmospheric turbulence (AT) will distort the helical phase of the orbital angular momentum (OAM) beam, resulting in inter-mode crosstalk and system performance degradation. Based on modified Gerchberg-Saxton (GS) algorithm, this paper proposes a wavefront sensorless adaptive optics system to compensate the wavefront distortion of an OAM beam. For the modified GS algorithm, at each iteration, the spatial phase is re-modulated to descend along a new phase gradient direction to improve algorithm convergence. At the same time, in the spatial domain, negative feedback is generated by nonlinear operation to optimize the beam amplitude, so as to speed up the convergence speed of the algorithm. Simulation results show that our modified GS algorithm can better compensate the wavefront distortion of an OAM beam caused by atmospheric turbulence than the traditional GS and hybrid input–output algorithms, which provides a new idea to solve the problem of atmospheric turbulence in free space optical communication system.

Nowadays, constructing strong absorption materials addressing the low-frequency electromagnetic radiation (S and C bands) from electronic devices remains a significant challenge. In this work, size-tunable Co/CoO nanoparticles (NPs) are fabricated by decomposing zeolitic imidazolate framework (ZIF-67) precursors and subsequent hydrogen reduction. All samples show obvious low-frequency attenuation in the S and C bands. At a thin thickness of 2.3 mm, the minimum reflection loss (RL) value for the Co/CoO NPs of 30 nm reaches up to -90.3 dB at 4.4 GHz, and the corresponding effective absorption bandwidth (EAB) of RL <= -10 dB ranges from 3.8 to 5.4 GHz. Notably, 90 % of the electromagnetic waves can be absorbed in the frequency range of 2.3-13.2 GHz, covering almost the entire S, C, and X bands at a thickness of 1.0-4.0 mm. The strong low-frequency absorption performance is attributed to the nano-porous structure, high conduction loss, tunable dielectric/magnetic loss, as well as optimized impedance matching. These Co/CoO NPs are promising candidates for high-efficient microwave absorbers in the low-frequency application. (C) 2022 Elsevier Inc. All rights reserved.

It is highly demanding and challenging to construct the nano-scale microwave absorber with wide-frequency responding feature. Herein, a series of Co@C nanocapsules (NCs) are fabricated via one-step carbon reduction of Co3O4 nanoparticles (NPs) of only 20 nm obtained by the nitrate pyrolysis method. The electromagnetic parameters of the samples can be effectively regulated by flexibly adjusting the carbon shell thickness. Surprisingly, all samples exhibit ultra-wide microwave absorption (MA) performance investigated by the coaxial method. For the Co@C NCs with a carbon shell of 25 nm, especially, the effective absorption bandwidth (EAB) for reflection loss (RL) below -10 dB reaches a record high of 15.2 GHz (2.8-18 GHz), which completely covers the whole C-, X-, and Ku-bands. More excitingly, the absorption bandwidth for RL <= -20 dB is up to 7.1 GHz at only 2.0 mm thickness. Such outstanding MA properties are attributed to nano-size effect, synergistic effects of strong dielectric/magnetic loss, and superior impedance matching characteristics. Notably, the polarization and magnetic coupling behaviors are clarified with the aid of electric field and magnetic field simulations using HighFrequency Structure Simulator (HFSS). The plate coating sample is further prepared and measured by the arch method, which also displays an ultrawide MA bandwidth. This work provides a new design strategy toward the facile synthesis of ultra-broadband microwave absorbers.

Nowadays, in the practical application of microwave absorption, it is still urgent and challenging to develop the microwave absorber with broadened bandwidth at a single thickness. Constructing composites with multi-component and multi-structure has been an effective strategy to obtain enhanced microwave absorption performance. Herein, yolk-shelled Co@SiO2@Mesoporous carbon (Co@SiO2@MC) microspheres were prepared by in-situ one-pot synthesis, carbonization reduction, and subsequent etching. The mesoporous carbon shell and hollow cavity structure were obtained simultaneously by controlling the etching of SiO2. The large carbon-air interface in the mesoporous shell and interior voids extend the propagation path of electromagnetic wave and enhance scattering. Owing to strong dielectric/magnetic loss, synergistic effect between different components and microstructures, as well as excellent impedance matching, Co@SiO2@MC microspheres exhibit desirable microwave absorption performance. Notably, for the sample with mesoporous carbon shell thickness of 25nm, the effective absorption bandwidth (reflection loss below -10 dB) is as wide as 9.6 GHz (8.4-18 GHz), completely covering the whole X and Ku bands at 3.7 mm. The ultra-wide absorption bandwidth of the yolk-shelled Co@SiO2@MC microspheres highlight their potential application in the field of microwave absorption. Furthermore, this work provides new insights for the preparation of multi-component/multi-structure microwave absorbers. (C) 2021 Elsevier Inc. All rights reserved.

We research the transport properties on a three-region structure of the bulk Weyl semimetals. We show the change of electron scattering with field b0 in center transport region when electrons pass through the center transport region. A valley is filtered when b0 is near Fermi energy EF by calculating valley-resolved transmission probability and valley-resolved reflection probability of Weyl electrons. We also research the influence of short-range disorders on valley transport property. These results can not only contribute to the comprehending of Weyl semimetals and valleytronics, but also provide a feasible method to design valley filter in view of the Weyl semimetals.

Metal nanomaterials have attracted increasing attention due to their outstanding nonlinear optical and photonic properties, making them as potential saturable absorber (SA) candidates for realizing ultrafast photonic devices. In this article, we demonstrate the generation of mode-locked dual-wavelength pulse trains in an Ag nanoplates (AgNPTs)-based Yb-doped all-fiber laser for the first time to the best of our knowledge. The AgNPTs are synthesized by seed-mediated growth and then integrated into a fiber ferrule by optical deposition, which serve as SA in the ring laser cavity. The plasmonic properties of such nanoplates are measured by absorption spectrophotometry and their nonlinear optical properties are characterized by Z-scan. The measured nonlinear saturable absorption of the AgNPTs-based SA is 6.4%. In our laser, the dual-wavelength synchronous mode-locking is achieved at the center wavelengths of 1031.92 and 1033.24 nm with 3-dB spectral bandwidth of 0.52 and 0.46 nm, respectively, where 293-ps pulse trains with a repetition rate of 11.43 MHz are obtained at the pump power of 350 mW. The results demonstrate that the solution-processed AgNPTs are promising SA candidates for achieving stable and low-cost pulsed laser sources which could be used for spectroscopy and ultrafast photonics.

We theoretically study the Landau levels and the magneto-optical conductivity of eight-Pmmn borophene in the presence of a perpendicular magnetic field and an inplane electric field. We find that in the absence of the inplane electric field, the magneto-optical conductivity of eight-Pmmn borophene presents a series of striking single resonance peaks as functions of the frequency ω, and the longitudinal conductivities are found to be anisotropic due to its anisotropic tilted Dirac cones. In the presence of the inplane electric field, some novel effects are predicted on the Landau levels and the magneto-optical conductivity. The Landau level spacings in the two tilted Dirac cones are different, which lifts the degeneracy of the twofold valley, and the magneto-optical conductivity appears a double peak structure. We also discuss the influence of the chemical potential between different Landau levels on the double peak of the magneto-optical response. The valley related magneto-optical properties in the anisotropic structure may make eight-Pmmn borophene a candidate for the new optical devices.

The fluorescent molecules utilizing hybridized local and charge-transfer (HLCT) state as potential organic light-emitting diodes materials attract extensive attention due to their high exciton utilization. In this work, we have performed the density functional theory method on three HLCT-state molecules to investigate their excited-state potential energy surface (PES). The calculated results indicate the T 1 and T 2 energy gap is quite large, and the T 2 is very close to S 1 in the energy level. The large gap is beneficial for inhibiting the internal conversion between T 1 and T 2 , and quite closed S 1 and T 2 energies are favor for activating the T 2 → S 1 reverse intersystem crossing path. However, considering the singlet excited-state PES by twisting the triphenylamine (TPA) or diphenylamine (PA) group, it can be found that the TPA or PA group almost has no influence on T 1 and T 2 energy levels. However, the plots of S 1 PES display two kinds of results that the S 1 emissive state is dominated by charge-transfer (CT) or HLCT state. The CT emission state formation would decrease the S 1 energy level, enlarge the S 1 and T 2 gap, and impair the triplet exciton utilization. Therefore, understanding the relationship between the S 1 PES and molecular structures is important for designing high-performance luminescent materials utilizing HLCT state.

以正硅酸四乙酯和FeCo为原料,采用改进的St?ber工艺制备了FeCo@纳米SiO2.结果表明:制备粉体为均匀核壳结构;当SiO2含量为35％(质量分数)时,样品的最低反射损耗(RL)在厚度为2.6 mm时达到?36.1 dB,有效吸收带宽(RL10 dB)为3.2 GHz;当SiO2含量为65％时,样品具有最佳的抗氧化性,升温至800℃,质量增加仅2％.SiO2的包覆不仅优化了FeCo的阻抗匹配,有利于电磁波吸收,而且在高温下SiO2可以阻隔FeCo和氧气接触,增加其抗氧化性.

We investigate the magneto-optical transport properties and Landau levels of type-II nodal line semimetals. The tilted liner dispersion in type-II nodal line semimetals makes the conduction band and valence band asymmetric, and Landau levels are coupling in the presence of a magnetic field. We find the background of absorption peaks is curved. The oscillation peaks are tailless with the change of magnetic field. Through tuning tilt term, we find the absorption peaks of optical conductivity change from incomplete degenerate structure to splitting double peaks structure. We also find interband absorption peaks is no longer zero in the imaginary part of Hall conductivity. With the change of the tilt term, the contribution of the absorption peak has two forms, one is that the negative peak only appears at high frequencies, and the other is two adjacent peaks with opposite signs. In addition, the resistivity, circularly polarized light and magnetic oscillation of Hall conductivity are studied.

In this paper, we theoretically study the topological phase transition from nodal-line semimetal to Weyl semimetal. The nodal-line structure is protected by mirror symmetry and located on the kx-ky mirror reflection plane, and the Hamiltonian of nodal-line semimetal has an emergent chiral symmetry on this plane. When the mirror symmetry is broken, the topological nodal line opens the gap and the nodal-line semimetal transition to Weyl semimetal with Weyl points on the kx axis or the ky axis. In addition, we break the chiral symmetry and realize the Weyl semimetal with the Weyl points on the kz axis. Destruction of the chiral symmetry leads to the gradual bending of the energy bands. With the evolution of the energy bands, the type-II nodal-line semimetal, the type-II Weyl semimetal and the type-I Weyl semimetal are successively realized. Furthermore, we also study the surface states of the nodal-line semimetal and the corresponding Weyl semimetals after the phase transition. Our work provides more ways to study the phase transition between nodal-line semimetal and Weyl semimetal and helps realize possible applications in topological electronic devices in the future.