Amorphization activated FeB_(2) porous nanosheets enable efficient electrocatalytic N_(2) fixation

Designing active,robust and cost-effective catalysts for the nitrogen reduction reaction(NRR) is of paramount significance for sustainable electrochemical NH3 synthesis.Transition-metal diborides(TMB_2)have been recently theoretically predicted to be a new class of potential NRR catalysts,but direct experimental evidence is still lacking.Herein,we present the first experimental demonstration that amorphous FeB_2 porous nanosheets(a-FeB_2 PNSs) could be a highly efficient NRR catalyst,which exhibited an NH3 yield of 39.8 μg h^(-1) mg^(-1)(-0.3 V) and a Faradaic efficiency of 16.7%(-0.2 V),significantly outperforming their crystalline counterpart and most of existing NRR catalysts.First-principle calculations unveiled that the amorphization could induce the upraised d-band center of a-FeB_2 to boost d-2π~* coupling between the active Fe site and ~*N_2 H intermediate,resulting in enhanced ~*N_2 H stabilization and reduced reaction barrier.Out study may facilitate the development and understanding of earth-abundant TMB_2-based catalysts for electrocatalytic N_2 fixation.

Amorphous MoS_(3) enriched with sulfur vacancies for efficient electrocatalytic nitrogen reduction

Developing low-priced,yet effective and robust catalysts for the nitrogen reduction reaction(NRR) is of vital importance for scalable and renewable electrochemical NH3 synthesis.Herein,we provide the first demonstration of MoS_3 as an efficient and durable NRR catalyst in neutral media.The prepared amorphous MoS_3 naturally possessed enriched S vacancies and delivered an NH3 yield of 51.7 μg h^(-1) mg^(-1)and a Faradaic efficiency of 12.8% at-0.3 V(RHE) in 0.5 M LiClO_4,considerably exceeding those of MoS_2 and most reported NRR catalysts.Density functional theory calculations unraveled that S vacancies involved in MoS_3 played a crucial role in activating the NRR via a consecutive mechanism with a low energetics barrier and simultaneously suppressing the hydrogen evolution reaction.

Spectrum evolution of Rayleigh backscattering in one‐dimensional waveguide

Despite the tremendous awareness of Rayleigh scattering characteristics and its considerable research interest for numerous fields,no report has been documented on the dynamic characteristics of spectrum evolution(SpE)and physical law for Rayleigh scattering from a micro perspective.Herein,the dynamic characteristics of the SpE of Rayleigh scattering in a one-dimensional waveguide(ODW)is investigated based on the quantum theory and a SpE-model of Rayleigh backscattering(RBS)source is established.By means of simulation,the evolution law which represents the dynamic process of the spectrum linewidth at a state of continuous scattering is revealed,which is consistent with our previous experimental observation.Moreover,an approximate theoretical prediction of the existing relationship between the spectrum linewidth of RBS source and the transmission length in ODW is proposed,which theoretically provides the feasibility of constructing functional devices suitable to ascertain laser linewidth compression.The designed experimental scheme can be implemented provided the assumptions are fulfilled.In addition,a theoretical model of the micro-cavity structure to realize the deep compression of laser linewidth is proposed.

纳光电子与光子芯片研究:发展与挑战

光子芯片被认为是“后摩尔时代”信息领域发展的核心技术之一。纳光电子学的发展为实现更高性能和更高集成度的光子芯片技术奠定了基础。同时,光子芯片对于突破电子芯片“卡脖子”的现实问题具有重要战略意义,有助于推动我国在未来光电信息产业的国际竞争中走出“缺芯”困境,并取得先发优势。基于国家自然科学基金委员会第312期“双清论坛”,本文总结了我国在纳光电子与光子芯片研究方面的重大需求,回顾了纳光电子与光子芯片领域近年来通过物理、材料、信息、制造等学科交叉融合所取得的主要进展和成就,凝炼了该领域未来5~10年的重大关键科学问题,探讨了前沿研究方向和科学基金资助战略。

Symmetry-protected third-order exceptional points in staggered flatband rhombic lattices

Higher-order exceptional points(EPs), which appear as multifold degeneracies in the spectra of non-Hermitian systems, are garnering extensive attention in various multidisciplinary fields. However, constructing higher-order EPs still remains a challenge due to the strict requirement of the system symmetries. Here we demonstrate that higher-order EPs can be judiciously fabricated in parity–time(PT)-symmetric staggered rhombic lattices by introducing not only on-site gain/loss but also non-Hermitian couplings. Zero-energy flatbands persist and symmetry-protected third-order EPs(EP3s) arise in these systems owing to the non-Hermitian chiral/sublattice symmetry, but distinct phase transitions and propagation dynamics occur. Specifically, the EP3 arises at the Brillouin zone(BZ) boundary in the presence of on-site gain/loss. The single-site excitations display an exponential power increase in the PT-broken phase. Meanwhile, a nearly flatband sustains when a small lattice perturbation is applied. For the lattices with non-Hermitian couplings, however, the EP3 appears at the BZ center. Quite remarkably, our analysis unveils a dynamical delocalization-localization transition for the excitation of the dispersive bands and a quartic power increase beyond the EP3. Our scheme provides a new platform toward the investigation of the higher-order EPs and can be further extended to the study of topological phase transitions or nonlinear processes associated with higher-order EPs.

Hybrid nano-scale Au with ITO structure for a high-performance near-infrared silicon-based photodetector with ultralow dark current

An internal photoemission-based silicon photodetector detects light below the silicon bandgap at room temperature and can exhibit spectrally broad behavior,making it potentially suited to meet the need for a near-infrared pure Si photodetector.In this work,the implementation of a thin Au insertion layer into an ITO/n-Si Schottky photodetector can profoundly affect the barrier height and significantly improve the device performance.By fabricating a nanoscale thin Au layer and an ITO electrode on a silicon substrate,we achieve a well-behaved ITO/Au/n-Si Schottky diode with a record dark current density of 3.7×10^(−7) A/cm^(2) at−1 V and a high rectification ratio of 1.5×10^(8) at±1 V.Furthermore,the responsivity has been obviously improved without sacrificing the dark current performance of the device by decreasing the Au thickness.Such a silicon-based photodetector with an enhanced performance could be a promising strategy for the realization of a monolithic integrated pure silicon photodetector in optical communication.

Nanodevices engineering and spin transport properties of MnBi_(2)Te_(4) monolayer

Two-dimensional(2D)magnetic materials are essential for the development of the next-generation spintronic technologies.Recently,layered van der Waals(vdW)compound MnBi2Te4(MBT)has attracted great interest,and its 2D structure has been reported to host coexisting magnetism and topology.Here,we design several conceptual nanodevices based on MBT monolayer(MBT-ML)and reveal their spin-dependent transport properties by means of the first-principles calculations.The pn-junction diodes and sub-3-nm pin-junction field-effect transistors(FETs)show a strong rectifying effect and a spin filtering effect,with an ideality factor n close to 1 even at a reasonably high temperature.In addition,the pip-and nin-junction FETs give an interesting negative differential resistive(NDR)effect.The gate voltages can tune currents through these FETs in a large range.Furthermore,the MBT-ML has a strong response to light.Our results uncover the multifunctional nature of MBT-ML,pave the road for its applications in diverse next-generation semiconductor spin electric devices.

Comparison of Additives in Anode:The Case of Graphene,MXene,CNTs Integration with Silicon Inside Carbon Nanofibers

Recently,graphene oxide(GO),MXene,carbon nanotubes(CNTs) have been used for compounding with other materials as anodes and cathodes to achieve excellent electrochemical properties for metal-ion batteries.However,few researches have focused on the differences between the three additives.Herein,silicon,as a typical anode,is selected to integrate with MXene,GO and CNTs in carbon nanofibers(CNFs) and form Si/MXene@CNFs,Si/GO@CNFs and Si/CNTs@CNFs,respectively.Together with the results,it can be realized that these CNFs with a significant improved performance compared with pure Si@CNFs show superiority in different aspects of electrochemical properties.Additionally,the reasons for the superiority are also discussed in this work.The addition of MXene can improve the cycle stability of the electrodes,thereby obtaining a high capacity retention rate,CNTs are favorable for the enhancement of rate performance,and the electrodes reversible capacity can be increased due to the addition of GO.Consequently,the studies on three additives may contribute to the rational design of silicon-based and other anode materials.