Smart Interfacing between Co-Fe Layered Double Hydroxide and Graphitic Carbon Nitride for High-efficiency Electrocatalytic Nitrogen Reduction

Bimetallic compounds such as hydrotalcite-type layered double hydroxides(LDHs)are promising electrocatalysts owing to their unique electronic structures.However,their abilities toward nitrogen adsorption and reduction are undermined since the surface-mantled,electronegative-OH groups hinder the charge transfer between transition metal atoms and nitrogen molecules.Herein,a smart interfacing strategy is proposed to construct a coupled heterointerface between LDH and 2D g-C_(3)N_(4),which is proven by density functional theory(DFT)investigations to be favorable for nitrogen adsorption and ammonia desorption compared with neat LDH surface.The interfaced LDH and g-C_(3)N_(4) is further hybridized with a self-standing TiO_(2) nanofibrous membrane(NM)to maximize the interfacial effect owing to its high porosity and large surface area.Profited from the synergistic superiorities of the three components,the LDH@C_(3)N_(4)@TiO_(2) NM delivers superior ammonia yield(2.07×10^(−9) mol s^(−1) cm^(−2))and Faradaic efficiency(25.3%),making it a high-efficiency,noble-metal-free catalyst system toward electrocatalytic nitrogen reduction.

Field-induced anisotropic magnetic phase transitions and tricritical phenomena in GdCr_(6)Ge_(6)

The interaction between complex magnetic structures and non-trivial band structures in ternary rare-earth GdCr_(6)Ge_(6) induces exotic and abundant electro-magnetic phenomena.In this work,we perform a systematical investigation on critical behaviors and magnetic properties of the single-crystal GdCr_(6)Ge_(6).The temperature,field,and angle dependence of magnetization unveils strong magnetic anisotropy along the c-axis and isotropic characteristic in the ab-plane.Critical exponentsβ=0.252(1),γ=0.905(9),δ=4.606(3)for H//ab,andβ=0.281(3),γ=0.991(8),δ=4.541(5)for H//c are obtained by the modified Arrott plot method(MAP)and critical isotherm(CI)analysis.The determined exponents for both directions are consistent with the theoretical prediction of a tricritical mean-field model.Based on detailed magnetization measurements and universality scaling,comprehensive magnetic phase diagrams of GdCr6Ge6for H//ab and H//c are constructed,which reveal that the external field induces a ferromagnetic(FM)transition for H//ab while a ferrimagnetic(FIM)one for H//c.Two tricritical points are determined for H//ab(11.2 K,266.3 Oe)and H//c(11.3 K,3.3 kOe)on the phase diagrams,respectively.The field-induced anisotropic magnetic configurations and multiple phases are clarified,where the moments of Gd and Cr form FM coupling for H//ab while FIM one for H//c via the interaction between Gd and Cr sublattices.

Magnetic properties and critical behavior of quasi-2D layered Cr_(4)Te_(5)thin film

Quasi-2D layered Cr4Te5 thin film has attracted great attention because it possesses the high Curie temperature close to room temperature and relatively large saturation magnetization.However,the magnetic interactions and the nature of magnetic phase transition in the Cr4Te5 film have not been explored thoroughly.In this paper,we focused on the critical behavior of its magnetic phase transition through the epitaxial Cr4Te5 film fabricated by pulsed laser deposition(PLD).The final critical exponentsβ=0.359(2)andγ=1.54(2)were obtained by linear extrapolation together with ArrottNoakes equation of state,and their accuracy was confirmed by using the Widom scaling relation and scaling hypothesis.We find that some magnetic disorders exist in the Cr4Te5 film system,which is related to Cr4Te5 critical behavior why its critical behavior is quite far from any conventional universality class.Furthermore,we also determined that the Cr4Te5 film exhibits a quasi-2D long-range magnetic interaction.Finally,the itinerant ferromagnets of Cr4Te5 films were confirmed by the Takahashi’s self-consistent renormalization theory of spin fluctuations.Our work provides a new idea for understanding the mechanism of magnetic interactions in similar 2D layered films.

Recent advances in organic-based materials for resistive memory applications

With the rapid development of data-driven human interaction,advanced datastorage technologies with lower power consumption,larger storage capacity,faster switching speed,and higher integration density have become the goals of future memory electronics.Nevertheless,the physical limitations of conventional Si-based binary storage systems lag far behind the ultrahigh-density requirements of post-Moore information storage.In this regard,the pursuit of alternatives and/or supplements to the existing storage technology has come to the forefront.Recently,organic-based resistive memory materials have emerged as promising candidates for next-generation information storage applications,which provide new possibilities of realizing high-performance organic electronics.Herein,the memory device structure,switching types,mechanisms,and recent advances in organic resistive memory materials are reviewed.In particular,their potential of fulfilling multilevel storage is summarized.Besides,the present challenges and future prospects confronted by organic resistive memory materials and devices are discussed.

Strong phonon-magnon coupling of an O/Fe(001) surface

Using density functional calculations,we elucidate the interaction between magnons and phonons on Fe(001)and O/Fe(001)surfaces.The effective Heisenberg exchange parameters between neighbor sites(Ji)were derived by fitting the ab initio spin spiral dispersion relation to a classical Heisenberg model.In bulk Fe,J5bhas a larger amplitude than J2b-J4b.Surface magnons were softer on the Fe(001)surface than in bulk,but were strengthened on the O/Fe(001)surface through strong interactions between the O and Fe atoms.The four calculated high-energy phonon modes of O/Fe(001)excellently agreed with the experimental measurements.The J1in O/Fe(001)decreased significantly with increasing phonon amplitude.Phonon-magnon coupling occurred more easily on O/Fe(001)than on Fe(001).The softening of the magnon on the O/Fe(001)with phonon amplitude was attributed to the reduced amplitude of longitudinal excitations.Magnetic moment of the Fe atom of the second layer(Fe2)was especially sensitive to phonon amplitude,regardless of the motion direction of the Fe2 atoms.

A robust graphene oxide memristor enabled by organic pyridinium intercalation for artificial biosynapse application

Graphene oxide(GO)-based memristors offer the promise of low cost,eco-friendliness,and mechanical flexibility,making them attractive candidates for outstanding flexible electronic devices.However,their resistive transitions often display abrupt change rather than bidirectional progressive tuning,which largely limits their applications for biological synapse emulation and neuromorphic computing.Here,a memristor with a novel layered structure of GO/pyridinium/GO is presented with tunable bidirectional feature.The inserted organic pyridinium intercalation succeeds in serving as a satisfactory buffer layer to intrinsically control the formation of conductive filaments during device operation,leading to progressive conductance regulation.Thus,the essential synaptic behaviors including analog memory characteristics,excitatory postsynaptic current,paired pulse facilitation,prepulse inhibition,spike-timing-dependent plasticity,and spike-rate-dependent plasticity are replicated.The emulation of brain-like“learning-forgetting-relearning”process is also implemented.Additionally,the instant responses of the memristor can be stimulated by low operational voltages and short pulse widths.This study paves one way for GO-based memristors to actuate appealing features such as bidirectional tuning and fast speed switching that are desirable for the development of bio-inspired neuromorphic systems.

基于结晶材料的柔性忆阻器的研究进展

忆阻器因其结构独特以及电学行为能够模拟生物突触,近年来在存算一体化和人工神经网络领域显现出广阔的应用前景.从材料多样性的角度而言,目前已有诸多材料显示出应用于忆阻器的巨大潜力.在本文中,我们关注一类基于结晶材料的柔性忆阻器.首先介绍了典型的忆阻器件结构与开关机制,其次重点综述了基于结晶材料的柔性忆阻器及其在数据存储和神经形态计算领域的应用,包括二维材料、金属有机框架材料、共价有机框架材料和钙钛矿材料.最后,对当前基于结晶材料的柔性忆阻器的发展前景进行了展望.

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.

Variable Learning-Memory Behavior fromπ-Conjugated Ligand to Ligand-Containing Cobalt(II)Complex

In the information-explosion era,developing novel algorithms and memristive devices has become a promising concept for next-generation capacity enlargement technology.Organic small molecule-based devices displaying superior learning-memory performance have attracted much attention,except for the existence of poor heat-resilience and mediocre conductivity.In this paper,a strategy of transforming an organic-type data-storage material to metal complex is proposed to resolve these intrinsic issues.A pristine NDI-derivative(NIPy)and its corresponding Co(II)complex(CoNIPy)are synthesized for the purpose of electrical property investigation.CoNIPy complex-based memristive device exhibits superior ternary WORM memory performance compared with the binary behavior of NIPy,including>104 s of reading,lower threshold voltage(V_(th)),1:10^(2):10^(5)of OFF/ON1/ON2 current ratio,and long-term stability in heating environment.The variable learning-memory behavior can be attributed to the enhanced ligand-to-metal charge transfer(LMCT)and improved redox activity after the introduction of central metal atom and coordination bond.These studies on material innovation and optimal performance are of great importance not only for environmentally-robust memristive devices but also for practical application of a host of organic electronic devices.