NiO_(x)as a hole transport material for inverted perovskite solar cells has received great attention owing to its high transparency,low fabrication temperature,and superior stability.However,the mismatched energy leve...NiO_(x)as a hole transport material for inverted perovskite solar cells has received great attention owing to its high transparency,low fabrication temperature,and superior stability.However,the mismatched energy levels and possible redox reactions at the NiO_(x)/perovskite interface severely limit the performance of NiO_(x) based inverted perovskite solar cells.Herein,we introduce a p-type self-assembled monolayer between NiO_(x)and perovskite layers to modify the interface and block the undesirable redox reaction between perovskite and NiO_(x)The selfassembled monolayer molecules all contain phosphoric acid function groups,which can be anchored onto the NiOr surface and passivate the surface defect.Moreover,the introduction of self-assembled monolayers can regulate the energy level structure of NiO_(x),reduce the interfacial band energy offset,and hence promote the hole transport from perovskite to NiO_(x)layer.Consequently,the device performance is significantly enhanced in terms of both power conversion efficiency and stability.展开更多
The design and preparation of novel quantum materials with atomic precision are crucial for exploring new physics and for device applications.Electron irradiation has been demonstrated as an effective method for prepa...The design and preparation of novel quantum materials with atomic precision are crucial for exploring new physics and for device applications.Electron irradiation has been demonstrated as an effective method for preparing novel quantum materials and quantum structures that could be challenging to obtain otherwise.It features the advantages of precise control over the patterning of such new materials and their integration with other materials with different functionalities.Here,we present a new strategy for fabricating freestanding monolayer SiC within nanopores of a graphene membrane.By regulating the energy of the incident electron beam and the in-situ heating temperature in a scanning transmission electron microscope(STEM),we can effectively control the patterning of nanopores and subsequent growth of monolayer SiC within the graphene lattice.The resultant SiC monolayers seamlessly connect with the graphene lattice,forming a planar structure distinct by a wide direct bandgap.Our in-situ STEM observations further uncover that the growth of monolayer SiC within the graphene nanopore is driven by a combination of bond rotation and atom extrusion,providing new insights into the atom-by-atom self-assembly of freestanding two-dimensional(2D)monolayers.展开更多
The hydroxyl-terminated self-assembled monolayer(OH-SAM),as a surface resistant to protein adsorption,exhibits substantial potential in applications such as ship navigation and medical implants,and the appropriate str...The hydroxyl-terminated self-assembled monolayer(OH-SAM),as a surface resistant to protein adsorption,exhibits substantial potential in applications such as ship navigation and medical implants,and the appropriate strategies for designing anti-fouling surfaces are crucial.Here,we employ molecular dynamics simulations and alchemical free energy calculations to systematically analyze the factors influencing resistance to protein adsorption on the SAMs terminated with single or double OH groups at three packing densities(∑=2.0 nm^(-2),4.5 nm^(-2),and 6.5 nm^(-2)),respectively.For the first time,we observed that the compactness and order of interfacial water enhance its physical barrier effect,subsequently enhancing the resistance of SAM to protein adsorption.Notably,the spatial hindrance effect of SAM leads to the embedding of protein into SAM,resulting in a lack of resistance of SAM towards protein.Furthermore,the number of hydroxyl groups per unit area of double OH-terminated SAM at ∑=6.5 nm^(-2) is approximately 2 to 3 times that of single OH-terminated SAM at ∑=6.5 nm^(-2) and 4.5 nm^(-2),consequently yielding a weaker resistance of double OH-terminated SAM towards protein.Meanwhile,due to the structure of SAM itself,i.e.,the formation of a nearly perfect ice-like hydrogen bond structure,the SAM exhibits the weakest resistance towards protein.This study will complement and improve the mechanism of OH-SAM resistance to protein adsorption,especially the traditional barrier effect of interfacial water.展开更多
Two-dimensional(2D)transition metal dichalcogenides(TMD)are atomically thin semiconductors with promising optoelectronic applications across the visible spectrum.However,their intrinsically weak light absorption and t...Two-dimensional(2D)transition metal dichalcogenides(TMD)are atomically thin semiconductors with promising optoelectronic applications across the visible spectrum.However,their intrinsically weak light absorption and the low photoluminescence quantum yield(PLQY)restrict their performance and potential use,especially in ultraviolet(UV)wavelength light ranges.Quantum dots(QD)derived from 2D materials(2D/QD)provide efficient light absorption and emission of which energy can be tuned for desirable light wavelength.In this study,we greatly enhanced the photon absorption and PLQY of monolayer(1L)tungsten disulfide(WS_(2))in the UV range via hybridization with 2D/QD,particularly titanium nitride MXene QD(Ti_(2)N MQD)and graphitic carbon nitride QD(GCNQD).With the hybridization of MQD or GCNQD,1LWS_(2)showed a maximum PL enhancement by 15 times with 300 nm wavelength excitation,while no noticeable enhancement was observed when the excitation photon energy was less than the bandgap of the QD,indicating that UV absorption by the QD played a crucial role in enhancing the light emission of 1L-WS_(2)in our 0D/2D hybrid system.Our findings present a convenient method for enhancing the photo-response of 1L-WS_(2)to UV light and offer exciting possibilities for harvesting UV energy using 1L-TMD.展开更多
Quantum anomalous Hall(QAH) insulators have highly potential applications in spintronic device. However,available candidates with tunable Chern numbers and high working temperature are quite rare. Here, we predict a 1...Quantum anomalous Hall(QAH) insulators have highly potential applications in spintronic device. However,available candidates with tunable Chern numbers and high working temperature are quite rare. Here, we predict a 1T-PrN_(2) monolayer as a stable QAH insulator with high magnetic transition temperature of above 600 K and tunable high Chern numbers of C = ±3 from first-principles calculations. Without spin-orbit coupling(SOC),the 1T-PrN_(2) monolayer is predicted to be a p-state Dirac half metal with high Fermi velocity. Rich topological phases depending on magnetization directions can be found when the SOC is considered. The QAH effect with periodical changes of Chern number(±1) can be produced when the magnetic moment breaks all twofold rotational symmetries in the xy plane. The critical state can be identified as Weyl half semimetals. When the magnetization direction is parallel to the z-axis, the system exhibits high Chern number QAH effect with C = ±3.Our work provides a new material for exploring novel QAH effect and developing high-performance topological devices.展开更多
By systematic theoretical calculations,we reveal an excitonic insulator(EI)in the Ta_(2)Pd_(3)Te_(5)monolayer.The bulk Ta_(2)Pd_(3)Te_(5)is a van der Waals(vdW)layered compound,whereas the vdW layer can be obtained th...By systematic theoretical calculations,we reveal an excitonic insulator(EI)in the Ta_(2)Pd_(3)Te_(5)monolayer.The bulk Ta_(2)Pd_(3)Te_(5)is a van der Waals(vdW)layered compound,whereas the vdW layer can be obtained through exfoliation or molecular-beam epitaxy.First-principles calculations show that the monolayer is a nearly zero-gap semiconductor with the modified Becke–Johnson functional.Due to the same symmetry of the band-edge states,the two-dimensional polarization 2D would be finite as the band gap goes to zero,allowing for an EI state in the compound.Using the first-principles many-body perturbation theory,the GW plus Bethe–Salpeter equation calculation reveals that the exciton binding energy is larger than the single-particle band gap,indicating the excitonic instability.The computed phonon spectrum suggests that the monolayer is dynamically stable without lattice distortion.Our findings suggest that the Ta_(2)Pd_(3)Te_(5) monolayer is an excitonic insulator without structural distortion.展开更多
Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical pr...Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally verified.We theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground state.Utilizing first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are occupied.The atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase transitions.Introducing doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane polarizations.This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain.The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3).展开更多
Urea synthesis through the simultaneous electrocatalytic reduction of N_(2)and CO_(2)molecules under ambient conditions holds great promises as a sustainable alternative to its industrial production,in which the devel...Urea synthesis through the simultaneous electrocatalytic reduction of N_(2)and CO_(2)molecules under ambient conditions holds great promises as a sustainable alternative to its industrial production,in which the development of stable,highly efficient,and highly selective catalysts to boost the chemisorption,activation,and coupling of inert N_(2)and CO_(2)molecules remains rather challenging.Herein,by means of density functional theory computations,we proposed a new class of two-dimensional nanomaterials,namely,transition-metal phosphide monolayers(TM_(2)P,TM=Ti,Fe,Zr,Mo,and W),as the potential electrocatalysts for urea production.Our results showed that these TM_(2)P materials exhibit outstanding stability and excellent metallic properties.Interestingly,the Mo_(2)P monolayer was screened out as the best catalyst for urea synthesis due to its small kinetic energy barrier(0.35 eV)for C-N coupling,low limiting potential(-0.39 V),and significant suppressing effects on the competing side reactions.The outstanding catalytic activity of the Mo_(2)P monolayer can be ascribed to its optimal adsorption strength with the key^(*)NCON species due to its moderate positive charges on the Mo active sites.Our findings not only propose a novel catalyst with high-efficiency and high-selectivity for urea production but also further widen the potential applications of metal phosphides in electrocatalysis.展开更多
High theoretical capacity and unique layered structures make MoS_(2)a promising lithium-ion battery anode material.However,the anisotropic ion transport in layered structures and the poor intrinsic conductivity of MoS...High theoretical capacity and unique layered structures make MoS_(2)a promising lithium-ion battery anode material.However,the anisotropic ion transport in layered structures and the poor intrinsic conductivity of MoS_(2)lead to unacceptable ion transport capability.Here,we propose in-situ construction of interlayer electrostatic repulsion caused by Co^(2+)substituting Mo^(4+)between MoS_(2)layers,which can break the limitation of interlayer van der Waals forces to fabricate monolayer MoS_(2),thus establishing isotropic ion transport paths.Simultaneously,the doped Co atoms change the electronic structure of monolayer MoS_(2),thus improving its intrinsic conductivity.Importantly,the doped Co atoms can be converted into Co nanoparticles to create a space charge region to accelerate ion transport.Hence,the Co-doped monolayer MoS_(2)shows ultrafast lithium ion transport capability in half/full cells.This work presents a novel route for the preparation of monolayer MoS_(2)and demonstrates its potential for application in fast-charging lithium-ion batteries.展开更多
The recent successful fabrication of two-dimensional(2D)CoO with nanometer-thickness motivates us to investigate monolayer CoO due to possible magnetic properties induced by Co atoms.Here,we employ first-principles ca...The recent successful fabrication of two-dimensional(2D)CoO with nanometer-thickness motivates us to investigate monolayer CoO due to possible magnetic properties induced by Co atoms.Here,we employ first-principles calculations to show that monolayer CoO is a 2D spin-spiral semiconductor with a honeycomb lattice.The calculated phonon dispersion reveals the monolayer's dynamical stability.Monolayer CoO exhibits a type-I spin-spiral magnetic ground state.The spinspiral state and the direct bandgap character are both robust under biaxial compressive strain(-5%)to tensile strain(5%).The bandgap varies only slightly under either compressive or tensile strain up to 5%.These results suggest a potential for applications in spintronic devices and offer a new platform to explore magnetism in the 2D limit.展开更多
As a two-dimensional(2D)material,monolayer MoS2which limits its optical applications has a low absorption efficiency.In this paper,we propose a three-band perfect metamaterial absorber in the visible light range based...As a two-dimensional(2D)material,monolayer MoS2which limits its optical applications has a low absorption efficiency.In this paper,we propose a three-band perfect metamaterial absorber in the visible light range based on monolayer MoS_(2).The peak absorptivity of the structure at each resonance wavelength is nearly perfect,moreover,the light absorption of monolayer MoS2is obviously enhanced at the three resonant wavelengths.The dielectric–dielectric–metal structure we designed produces the coupling of Fabry–Perot resonance and high-order diffraction guided-mode resonance at different absorption peaks,which has been proved by the slab waveguide theory.In addition,the multi-modal absorption phenomenon is explained by extracting the equivalent impedance.The results show that we can adjust the absorption peak wavelength by regulating the parameters of the structure.This structure not only provides an idea for enhancing the interaction between light and two-dimensional materials but also has potential applications for optical detection devices.展开更多
In recent years,Janus two-dimensional(2D)materials have received extensive research interests because of their outstanding electronic,mechanical,electromechanical,and optoelectronic properties.In this work,we explore ...In recent years,Janus two-dimensional(2D)materials have received extensive research interests because of their outstanding electronic,mechanical,electromechanical,and optoelectronic properties.In this work,we explore the structural,electromechanical,and optoelectronic properties of a novel hypothesized Janus InGaSSe monolayer by means of first-principles calculations.It is confirmed that the Janus InGaSSe monolayer indeed show extraordinary charge transport properties with intrinsic electron mobility of 48139 cm^(2)/(V·s)and hole mobility of 16311 cm^(2)/(V·s).Both uniaxial and biaxial strains can effectively tune its electronic property.Moreover,the Janus InGaSSe monolayer possesses excellent piezoelectric property along both inplane and out-of-plane directions.The results of this work imply that the Janus InGaSSe monolayer is in fact an efficient photocatalyst candidate,and may provide useful guidelines for the discovery of other new 2D photocatalytic and piezoelectric materials.展开更多
The hydrogenic donor impurity states and intersubband optical absorption spectra in monolayer transition metal dichalcogenides(ML TMDs) under dielectric environments are theoretically investigated based on a two-dimen...The hydrogenic donor impurity states and intersubband optical absorption spectra in monolayer transition metal dichalcogenides(ML TMDs) under dielectric environments are theoretically investigated based on a two-dimensional(2D)nonorthogonal associated Laguerre basis set. The 2D quantum confinement effect together with the strongly reduced dielectric screening results in the strong attractive Coulomb potential between electron and donor ion, with exceptionally large impurity binding energy and huge intersubband oscillator strength. These lead to the strong interaction of the electron with light in a 2D regime. The intersubband optical absorption spectra exhibit strong absorption lines of the non-hydrogenic Rydberg series in the mid-infrared range of light. The strength of the Coulomb potential can be controlled by changing the dielectric environment. The electron affinity difference leads to charge transfer between ML TMD and the dielectric environment, generating the polarization-electric field in ML TMD accompanied by weakening the Coulomb interaction strength. The larger the dielectric constant of the dielectric environment, the more the charge transfer is, accompanied by the larger polarization-electric field and the stronger dielectric screening. The dielectric environment is shown to provide an efficient tool to tune the wavelength and output of the mid-infrared intersubband devices based on ML TMDs.展开更多
Janus WSSe monolayer is a novel two-dimensional(2D)material that breaks the out-of-plane mirror symmetry and has a large built-in electric field.These features lead to sizable Rashba spin-orbit coupling and enhanced n...Janus WSSe monolayer is a novel two-dimensional(2D)material that breaks the out-of-plane mirror symmetry and has a large built-in electric field.These features lead to sizable Rashba spin-orbit coupling and enhanced nonlinear optical properties,making it a promising material platform for various spintronic and optoelectronic device applications.In recent years,nonlinear photocurrent responses such as shift and injection currents were found to be closely related to the quantum geometry and Berry curvature of materials,indicating that these responses can serve as powerful tools for probing the novel quantum properties of materials.In this work,we investigate the second-order nonlinear photocurrent responses in a Janus WSSe monolayer theoretically based on first-principles calculations and the Wannier interpolation method.It is demonstrated that the Janus WSSe monolayer exhibits significant out-of-plane nonlinear photocurrent coefficients,which is distinct from the nonJanus structures.Our results also suggest that the second-order nonlinear photocurrent response in the Janus WSSe monolayer can be effectively tuned by biaxial strain or an external electric field.Thus,the Janus WSSe monolayer offers a unique opportunity for both exploring nonlinear optical phenomena and realizing flexible 2D optoelectronic nanodevices.展开更多
Elect rides,which confine"excess anionic electrons"in subnanometer-sized cavities of a lattice,are exotic ionic crystals.We propose a non-stoichiometric strategy to realize intrinsic two-dimensional(2D)super...Elect rides,which confine"excess anionic electrons"in subnanometer-sized cavities of a lattice,are exotic ionic crystals.We propose a non-stoichiometric strategy to realize intrinsic two-dimensional(2D)superconducting elect ride.AlH_(2)monolayer,which is structurally identical to 1H-MoS_(2),possesses zero-dimensionally confined anionic electrons in the interstitial sites of A1 triangles,corresponding to a chemical formula of[AlH_(2)]^(+)e^(-).The interaction between interstitial anionic electrons(IAEs)and host cation lattice mainly accounts for stabilization of 1H-AlH_(2)electride.Impressively,1H-AlH_(2)monolayer is an intrinsic Bardeen-Cooper-Schrieffer superconductor with T_(c)=38 K,which is the direct consequence of strong coupling of the H-dominated high electronic states with Al acoustic branch vibrations and mid-frequency H-derived phonon softening modes caused by Kohn anomalies.Under tensile strain,IAEs transform into itinerant electrons,favoring the formation of stable Cooper pairs.Therefore,T_(c)reaches up to 53 K at a biaxial fracture strain of 5%.Our findings provide valuable insights into the correlation between non-stoichiometric electrides and superconducting microscopic mechanisms at the 2D limit.展开更多
We report on ambipolar modulation doping of monolayer FeSe epitaxial films grown by molecular beam epitaxy and in situ spectroscopic measurements via a cryogenic scanning tunneling microscopy.It is found that hole dop...We report on ambipolar modulation doping of monolayer FeSe epitaxial films grown by molecular beam epitaxy and in situ spectroscopic measurements via a cryogenic scanning tunneling microscopy.It is found that hole doping kills superconductivity in monolayer FeSe films on metallic Ir(001)substrates,whereas electron doping from polycrystalline IrO_(2)/SrTiO_(3)substrate enhances significantly the superconductivity with an energy gap of 10.3 meV.By exploring substrate-dependent superconductivity,we elucidate the essential impact of substrate work functions on the superconductivity of monolayer FeSe films.Our results therefore offer a valuable reference guide for further enhancement of the transition temperature Tc in FeSe-based superconductors by interface engineering.展开更多
We fabricated monolayer n-type two-dimensional crystalline semiconducting films with millimeter-sized areas and remarkable morphological uniformity using an antisolvent-confined spin-coating method.The antisolvent can...We fabricated monolayer n-type two-dimensional crystalline semiconducting films with millimeter-sized areas and remarkable morphological uniformity using an antisolvent-confined spin-coating method.The antisolvent can cause a downstream Marangoni flow,which improves the film morphologies.The deposited crystalline monolayer films exhibit excellent thermal stabilities after annealing,which reveals the annealing-induced enhancement of crystallinity.The transistors based on the n-type monolayer crystalline films show linear output characteristics and superior electron mobilities.The improved charge injection between monolayer films and Au electrodes results from the energy level shift as the films decrease to the monolayer,which leads to a lower injection barrier.This work demonstrates a promising method for fabricating air-stable,low-cost,high-performance,and large-area organic electronics.展开更多
Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions(DNLFs).Here,we successfully synthesized a gold telluride(AuTe)monolayer by direct tellurizing an Au(111)substrate...Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions(DNLFs).Here,we successfully synthesized a gold telluride(AuTe)monolayer by direct tellurizing an Au(111)substrate.Low energy electron diffraction measurements reveal that it is(2×2)AuTe layer stacked onto(3×3)Au(111)substrate.Moreover,scanning tunneling microscopy images show that the AuTe layer has a honeycomb structure.Scanning transmission electron microscopy reveals that it is a single-atom layer.In addition,first-principles calculations demonstrate that the honeycomb AuTe monolayer exhibits Dirac nodal line features protected by mirror symmetry,which is validated by angle-resolved photoemission spectra.Our results establish that monolayer AuTe can be a good candidate to investigate 2D DNLFs and provides opportunities to realize high-speed low-dissipation devices.展开更多
Chiral magnetic states are promising for future spintronic applications. Recent progress of chiral spin textures in two-dimensional magnets, such as chiral domain walls, skyrmions, and bimerons, have been drawing exte...Chiral magnetic states are promising for future spintronic applications. Recent progress of chiral spin textures in two-dimensional magnets, such as chiral domain walls, skyrmions, and bimerons, have been drawing extensive attention. Here, via first-principles calculations, we show that biaxial strain can effectively manipulate the magnetic parameters of the Janus Mn Se Te monolayer. Interestingly, we find that both the magnitude and the sign of the magnetic constants of the Heisenberg exchange coupling, Dzyaloshinskii–Moriya interaction and magnetocrystalline anisotropy can be tuned by strain. Moreover, using micromagnetic simulations, we obtain the distinct phase diagram of chiral spin texture under different strains. Especially, we demonstrate that abundant chiral magnetic structures including ferromagnetic skyrmion, skyrmionium, bimeron, and antiferromagnetic spin spiral can be induced in the Mn Se Te monolayer. We also discuss the effect of temperature on these magnetic structures. The findings highlight the Janus Mn Se Te monolayer as a good candidate for spintronic nanodevices.展开更多
目的探讨单核细胞单层实验(monocyte monolayer assay,MMA)是否能够用于IgG抗-M相关胎儿新生儿溶血病(hemolytic disease of fetus and newborn,HDFN)的预测。方法选取8例含有IgG抗-M的孕妇并采集血浆标本,其中有胎儿水肿等严重临床症...目的探讨单核细胞单层实验(monocyte monolayer assay,MMA)是否能够用于IgG抗-M相关胎儿新生儿溶血病(hemolytic disease of fetus and newborn,HDFN)的预测。方法选取8例含有IgG抗-M的孕妇并采集血浆标本,其中有胎儿水肿等严重临床症状及无明显临床症状的各4例;8份血浆用二硫苏糖醇(dithiothreitol,DTT)灭活,与M抗原阳性红细胞孵育致敏后,将致敏红细胞与单核细胞混合进行吞噬试验,同时设立阳性及阴性对照,并计算吞噬率;采用t检验对2组吞噬率进行比较。结果4例发生严重抗-M相关HDFN的孕妇的MMA吞噬率分别为15.37%、13.05%、9.17%和24.50%,均值为15.52%;检出IgG抗-M但未发生HDFN的孕妇,其MMA吞噬率分别为8.74%、11.07%、5.12%和6.23%,均值为7.79%,2组吞噬率无差异(P>0.05)。2组吞噬率分别与阴性对照比较均无差异(P>0.05),但均明显低于阳性对照(P<0.05)。结论IgG抗-M介导单核细胞吞噬的能力较低,提示抗-M导致胎儿水肿的机制可能并非红细胞被吞噬破坏而发生的溶血,因此体外单核细胞单层实验可能不适用于IgG抗-M相关HDFN的预测。对于检出IgG抗-M的孕妇,现仍需通过定期监测胎儿大脑中动脉血流,来判断胎儿宫内贫血情况。展开更多
文摘NiO_(x)as a hole transport material for inverted perovskite solar cells has received great attention owing to its high transparency,low fabrication temperature,and superior stability.However,the mismatched energy levels and possible redox reactions at the NiO_(x)/perovskite interface severely limit the performance of NiO_(x) based inverted perovskite solar cells.Herein,we introduce a p-type self-assembled monolayer between NiO_(x)and perovskite layers to modify the interface and block the undesirable redox reaction between perovskite and NiO_(x)The selfassembled monolayer molecules all contain phosphoric acid function groups,which can be anchored onto the NiOr surface and passivate the surface defect.Moreover,the introduction of self-assembled monolayers can regulate the energy level structure of NiO_(x),reduce the interfacial band energy offset,and hence promote the hole transport from perovskite to NiO_(x)layer.Consequently,the device performance is significantly enhanced in terms of both power conversion efficiency and stability.
基金supports from the Electron Microscopy Center at the University of Chinese Academy of Sciencesfinancially supported by the Ministry of Science and Technology (MOST)of China (Grant No.2018YFE0202700)+3 种基金the Beijing Outstanding Young Scientist Program (Grant No.BJJWZYJH01201914430039)the China National Postdoctoral Program for Innovative Talents (Grant No.BX2021301)the Fundamental Research Funds for the Central Universitiesthe Research Funds of Renmin University of China (Grants No.22XNKJ30)。
文摘The design and preparation of novel quantum materials with atomic precision are crucial for exploring new physics and for device applications.Electron irradiation has been demonstrated as an effective method for preparing novel quantum materials and quantum structures that could be challenging to obtain otherwise.It features the advantages of precise control over the patterning of such new materials and their integration with other materials with different functionalities.Here,we present a new strategy for fabricating freestanding monolayer SiC within nanopores of a graphene membrane.By regulating the energy of the incident electron beam and the in-situ heating temperature in a scanning transmission electron microscope(STEM),we can effectively control the patterning of nanopores and subsequent growth of monolayer SiC within the graphene lattice.The resultant SiC monolayers seamlessly connect with the graphene lattice,forming a planar structure distinct by a wide direct bandgap.Our in-situ STEM observations further uncover that the growth of monolayer SiC within the graphene nanopore is driven by a combination of bond rotation and atom extrusion,providing new insights into the atom-by-atom self-assembly of freestanding two-dimensional(2D)monolayers.
基金Project supported by the National Natural Science Foundation of China (Grants No. 12075201)the Science and Technology Planning Project of Jiangsu Province, China (Grant No. BK20201428)+1 种基金the Postgraduate Research & Practice Innovation Program of Jiangsu Province, China (Grant No. KYCX21 3193)the Special Program for Applied Research on Supercomputation of the NSFC–Guangdong Joint Fund (the second phase)。
文摘The hydroxyl-terminated self-assembled monolayer(OH-SAM),as a surface resistant to protein adsorption,exhibits substantial potential in applications such as ship navigation and medical implants,and the appropriate strategies for designing anti-fouling surfaces are crucial.Here,we employ molecular dynamics simulations and alchemical free energy calculations to systematically analyze the factors influencing resistance to protein adsorption on the SAMs terminated with single or double OH groups at three packing densities(∑=2.0 nm^(-2),4.5 nm^(-2),and 6.5 nm^(-2)),respectively.For the first time,we observed that the compactness and order of interfacial water enhance its physical barrier effect,subsequently enhancing the resistance of SAM to protein adsorption.Notably,the spatial hindrance effect of SAM leads to the embedding of protein into SAM,resulting in a lack of resistance of SAM towards protein.Furthermore,the number of hydroxyl groups per unit area of double OH-terminated SAM at ∑=6.5 nm^(-2) is approximately 2 to 3 times that of single OH-terminated SAM at ∑=6.5 nm^(-2) and 4.5 nm^(-2),consequently yielding a weaker resistance of double OH-terminated SAM towards protein.Meanwhile,due to the structure of SAM itself,i.e.,the formation of a nearly perfect ice-like hydrogen bond structure,the SAM exhibits the weakest resistance towards protein.This study will complement and improve the mechanism of OH-SAM resistance to protein adsorption,especially the traditional barrier effect of interfacial water.
基金supported by National Research Foundation of Korea (NRF)funded by the Ministry of Education (2021R1A6A1A03039696,2022R1A2C2009412)
文摘Two-dimensional(2D)transition metal dichalcogenides(TMD)are atomically thin semiconductors with promising optoelectronic applications across the visible spectrum.However,their intrinsically weak light absorption and the low photoluminescence quantum yield(PLQY)restrict their performance and potential use,especially in ultraviolet(UV)wavelength light ranges.Quantum dots(QD)derived from 2D materials(2D/QD)provide efficient light absorption and emission of which energy can be tuned for desirable light wavelength.In this study,we greatly enhanced the photon absorption and PLQY of monolayer(1L)tungsten disulfide(WS_(2))in the UV range via hybridization with 2D/QD,particularly titanium nitride MXene QD(Ti_(2)N MQD)and graphitic carbon nitride QD(GCNQD).With the hybridization of MQD or GCNQD,1LWS_(2)showed a maximum PL enhancement by 15 times with 300 nm wavelength excitation,while no noticeable enhancement was observed when the excitation photon energy was less than the bandgap of the QD,indicating that UV absorption by the QD played a crucial role in enhancing the light emission of 1L-WS_(2)in our 0D/2D hybrid system.Our findings present a convenient method for enhancing the photo-response of 1L-WS_(2)to UV light and offer exciting possibilities for harvesting UV energy using 1L-TMD.
基金supported by National Natural Science Foundation of China (Grant No. 11874092)the Fok Ying Tong Education Foundation, China (Grant No. 161005)the Science Fund for Distinguished Young Scholars of Hunan Province (Grant No. 2021JJ10039)。
文摘Quantum anomalous Hall(QAH) insulators have highly potential applications in spintronic device. However,available candidates with tunable Chern numbers and high working temperature are quite rare. Here, we predict a 1T-PrN_(2) monolayer as a stable QAH insulator with high magnetic transition temperature of above 600 K and tunable high Chern numbers of C = ±3 from first-principles calculations. Without spin-orbit coupling(SOC),the 1T-PrN_(2) monolayer is predicted to be a p-state Dirac half metal with high Fermi velocity. Rich topological phases depending on magnetization directions can be found when the SOC is considered. The QAH effect with periodical changes of Chern number(±1) can be produced when the magnetic moment breaks all twofold rotational symmetries in the xy plane. The critical state can be identified as Weyl half semimetals. When the magnetization direction is parallel to the z-axis, the system exhibits high Chern number QAH effect with C = ±3.Our work provides a new material for exploring novel QAH effect and developing high-performance topological devices.
基金supported by the National Natural Science Foundation of China(Grant Nos.11974395 and 12188101)the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB33000000)+1 种基金the National Key R&D Program of China(Grant Nos.2022YFA1403800 and 2022YFA1403400)the Center for Materials Genome。
文摘By systematic theoretical calculations,we reveal an excitonic insulator(EI)in the Ta_(2)Pd_(3)Te_(5)monolayer.The bulk Ta_(2)Pd_(3)Te_(5)is a van der Waals(vdW)layered compound,whereas the vdW layer can be obtained through exfoliation or molecular-beam epitaxy.First-principles calculations show that the monolayer is a nearly zero-gap semiconductor with the modified Becke–Johnson functional.Due to the same symmetry of the band-edge states,the two-dimensional polarization 2D would be finite as the band gap goes to zero,allowing for an EI state in the compound.Using the first-principles many-body perturbation theory,the GW plus Bethe–Salpeter equation calculation reveals that the exciton binding energy is larger than the single-particle band gap,indicating the excitonic instability.The computed phonon spectrum suggests that the monolayer is dynamically stable without lattice distortion.Our findings suggest that the Ta_(2)Pd_(3)Te_(5) monolayer is an excitonic insulator without structural distortion.
基金supported by the National Key Research and Development Program of China(Grant Nos.2018YFE0202700 and 2023YFA1406500)the National Natural Science Foundation of China(Grant Nos.11974422 and 12104504)+2 种基金the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)Fundamental Research Funds for the Central Universities,and Research Funds of Renmin University,China(Grant No.22XNKJ30)supported by the Outstanding Innovative Talents Cultivation Funded Programs 2023 of Renmin University,China。
文摘Two-dimensional(2D)van der Waals magnetic materials have promising and versatile electronic and magnetic properties in the 2D limit,indicating a considerable potential to advance spintronic applications.Theoretical predictions thus far have not ascertained whether monolayer VCl_(3) is a ferromagnetic(FM)or anti-FM monolayer;this also remains to be experimentally verified.We theoretically investigate the influence of potential factors,including C_(3) symmetry breaking,orbital ordering,epitaxial strain,and charge doping,on the magnetic ground state.Utilizing first-principles calculations,we predict a collinear type-Ⅲ FM ground state in monolayer VCl_(3) with a broken C_(3) symmetry,wherein only the former two of three t_(2g)orbitals(a_(1g),e_(g2)^(π)and e_(g1)^(π))are occupied.The atomic layer thickness and bond angles of monolayer VCl_(3) undergo abrupt changes driven by an orbital ordering switch,resulting in concomitant structural and magnetic phase transitions.Introducing doping to the underlying Cl atoms of monolayer VCl_(3) without C_(3) symmetry simultaneously induces in-and out-of-plane polarizations.This can achieve a multiferroic phase transition if combined with the discovered adjustments of magnetic ground state and polarization magnitude under strain.The establishment of an orbital-ordering driven regulatory mechanism can facilitate deeper exploration and comprehension of magnetic properties of strongly correlated systems in monolayer VCl_(3).
基金financially supported in China by Natural Science Funds for Distinguished Young Scholars of Heilongjiang Province(No.JC2018004)Natural Science Foundation of Heilongjiang Province of China(No.TD2020B001)in the USA by NSF-CREST Center for Innovation,Research,and Education in Environmental Nanotechnology(CIRE2N)(No.HRD-1736093)
文摘Urea synthesis through the simultaneous electrocatalytic reduction of N_(2)and CO_(2)molecules under ambient conditions holds great promises as a sustainable alternative to its industrial production,in which the development of stable,highly efficient,and highly selective catalysts to boost the chemisorption,activation,and coupling of inert N_(2)and CO_(2)molecules remains rather challenging.Herein,by means of density functional theory computations,we proposed a new class of two-dimensional nanomaterials,namely,transition-metal phosphide monolayers(TM_(2)P,TM=Ti,Fe,Zr,Mo,and W),as the potential electrocatalysts for urea production.Our results showed that these TM_(2)P materials exhibit outstanding stability and excellent metallic properties.Interestingly,the Mo_(2)P monolayer was screened out as the best catalyst for urea synthesis due to its small kinetic energy barrier(0.35 eV)for C-N coupling,low limiting potential(-0.39 V),and significant suppressing effects on the competing side reactions.The outstanding catalytic activity of the Mo_(2)P monolayer can be ascribed to its optimal adsorption strength with the key^(*)NCON species due to its moderate positive charges on the Mo active sites.Our findings not only propose a novel catalyst with high-efficiency and high-selectivity for urea production but also further widen the potential applications of metal phosphides in electrocatalysis.
基金financially supported by Shenzhen Key Laboratory of Advanced Energy Storage(No.ZDSYS20220401141000001)the Research Grants Council of the Hong Kong Special Administrative Region,China(Project No.R6005-20)。
文摘High theoretical capacity and unique layered structures make MoS_(2)a promising lithium-ion battery anode material.However,the anisotropic ion transport in layered structures and the poor intrinsic conductivity of MoS_(2)lead to unacceptable ion transport capability.Here,we propose in-situ construction of interlayer electrostatic repulsion caused by Co^(2+)substituting Mo^(4+)between MoS_(2)layers,which can break the limitation of interlayer van der Waals forces to fabricate monolayer MoS_(2),thus establishing isotropic ion transport paths.Simultaneously,the doped Co atoms change the electronic structure of monolayer MoS_(2),thus improving its intrinsic conductivity.Importantly,the doped Co atoms can be converted into Co nanoparticles to create a space charge region to accelerate ion transport.Hence,the Co-doped monolayer MoS_(2)shows ultrafast lithium ion transport capability in half/full cells.This work presents a novel route for the preparation of monolayer MoS_(2)and demonstrates its potential for application in fast-charging lithium-ion batteries.
基金supported by grants from the National Natural Science Foundation of China(Grant Nos.52102193,52250402,and 61888102)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB30000000)+1 种基金the Fundamental Research Funds for the Central Universitiessupported in part by the Mc Minn Endowment。
文摘The recent successful fabrication of two-dimensional(2D)CoO with nanometer-thickness motivates us to investigate monolayer CoO due to possible magnetic properties induced by Co atoms.Here,we employ first-principles calculations to show that monolayer CoO is a 2D spin-spiral semiconductor with a honeycomb lattice.The calculated phonon dispersion reveals the monolayer's dynamical stability.Monolayer CoO exhibits a type-I spin-spiral magnetic ground state.The spinspiral state and the direct bandgap character are both robust under biaxial compressive strain(-5%)to tensile strain(5%).The bandgap varies only slightly under either compressive or tensile strain up to 5%.These results suggest a potential for applications in spintronic devices and offer a new platform to explore magnetism in the 2D limit.
基金the Strategic Priority Research Program of Chinese Academy of Sciences(Grant No.XDB43010000)the National Natural Science Foundation of China(Grant Nos.61835011 and 12075244)+1 种基金Key Research Projects of the Frontier Science of the Chinese Academy of Sciences(Grant No.QYZDY-SSW-JSC004)the National Key Research and Development Program of China(Grant No.2020YFB2206103).
文摘As a two-dimensional(2D)material,monolayer MoS2which limits its optical applications has a low absorption efficiency.In this paper,we propose a three-band perfect metamaterial absorber in the visible light range based on monolayer MoS_(2).The peak absorptivity of the structure at each resonance wavelength is nearly perfect,moreover,the light absorption of monolayer MoS2is obviously enhanced at the three resonant wavelengths.The dielectric–dielectric–metal structure we designed produces the coupling of Fabry–Perot resonance and high-order diffraction guided-mode resonance at different absorption peaks,which has been proved by the slab waveguide theory.In addition,the multi-modal absorption phenomenon is explained by extracting the equivalent impedance.The results show that we can adjust the absorption peak wavelength by regulating the parameters of the structure.This structure not only provides an idea for enhancing the interaction between light and two-dimensional materials but also has potential applications for optical detection devices.
基金supported by the Fundamental Research Funds for the Central Universities of China(Nos.PA2021KCPY0029 and LEM21A01)。
文摘In recent years,Janus two-dimensional(2D)materials have received extensive research interests because of their outstanding electronic,mechanical,electromechanical,and optoelectronic properties.In this work,we explore the structural,electromechanical,and optoelectronic properties of a novel hypothesized Janus InGaSSe monolayer by means of first-principles calculations.It is confirmed that the Janus InGaSSe monolayer indeed show extraordinary charge transport properties with intrinsic electron mobility of 48139 cm^(2)/(V·s)and hole mobility of 16311 cm^(2)/(V·s).Both uniaxial and biaxial strains can effectively tune its electronic property.Moreover,the Janus InGaSSe monolayer possesses excellent piezoelectric property along both inplane and out-of-plane directions.The results of this work imply that the Janus InGaSSe monolayer is in fact an efficient photocatalyst candidate,and may provide useful guidelines for the discovery of other new 2D photocatalytic and piezoelectric materials.
文摘The hydrogenic donor impurity states and intersubband optical absorption spectra in monolayer transition metal dichalcogenides(ML TMDs) under dielectric environments are theoretically investigated based on a two-dimensional(2D)nonorthogonal associated Laguerre basis set. The 2D quantum confinement effect together with the strongly reduced dielectric screening results in the strong attractive Coulomb potential between electron and donor ion, with exceptionally large impurity binding energy and huge intersubband oscillator strength. These lead to the strong interaction of the electron with light in a 2D regime. The intersubband optical absorption spectra exhibit strong absorption lines of the non-hydrogenic Rydberg series in the mid-infrared range of light. The strength of the Coulomb potential can be controlled by changing the dielectric environment. The electron affinity difference leads to charge transfer between ML TMD and the dielectric environment, generating the polarization-electric field in ML TMD accompanied by weakening the Coulomb interaction strength. The larger the dielectric constant of the dielectric environment, the more the charge transfer is, accompanied by the larger polarization-electric field and the stronger dielectric screening. The dielectric environment is shown to provide an efficient tool to tune the wavelength and output of the mid-infrared intersubband devices based on ML TMDs.
基金supported by the Natural Science Foundation of Fujian Province of China(Grant No.2020J01008)the National Natural Science Foundation of China(Grant No.12174382)。
文摘Janus WSSe monolayer is a novel two-dimensional(2D)material that breaks the out-of-plane mirror symmetry and has a large built-in electric field.These features lead to sizable Rashba spin-orbit coupling and enhanced nonlinear optical properties,making it a promising material platform for various spintronic and optoelectronic device applications.In recent years,nonlinear photocurrent responses such as shift and injection currents were found to be closely related to the quantum geometry and Berry curvature of materials,indicating that these responses can serve as powerful tools for probing the novel quantum properties of materials.In this work,we investigate the second-order nonlinear photocurrent responses in a Janus WSSe monolayer theoretically based on first-principles calculations and the Wannier interpolation method.It is demonstrated that the Janus WSSe monolayer exhibits significant out-of-plane nonlinear photocurrent coefficients,which is distinct from the nonJanus structures.Our results also suggest that the second-order nonlinear photocurrent response in the Janus WSSe monolayer can be effectively tuned by biaxial strain or an external electric field.Thus,the Janus WSSe monolayer offers a unique opportunity for both exploring nonlinear optical phenomena and realizing flexible 2D optoelectronic nanodevices.
基金supported by the National Natural Science Foundation of China(Grant Nos.12274050 and 91961204)the Fundamental Research Funds for the Central Universities(Grant Nos.DUT22LAB104 and DUT22ZD103)。
文摘Elect rides,which confine"excess anionic electrons"in subnanometer-sized cavities of a lattice,are exotic ionic crystals.We propose a non-stoichiometric strategy to realize intrinsic two-dimensional(2D)superconducting elect ride.AlH_(2)monolayer,which is structurally identical to 1H-MoS_(2),possesses zero-dimensionally confined anionic electrons in the interstitial sites of A1 triangles,corresponding to a chemical formula of[AlH_(2)]^(+)e^(-).The interaction between interstitial anionic electrons(IAEs)and host cation lattice mainly accounts for stabilization of 1H-AlH_(2)electride.Impressively,1H-AlH_(2)monolayer is an intrinsic Bardeen-Cooper-Schrieffer superconductor with T_(c)=38 K,which is the direct consequence of strong coupling of the H-dominated high electronic states with Al acoustic branch vibrations and mid-frequency H-derived phonon softening modes caused by Kohn anomalies.Under tensile strain,IAEs transform into itinerant electrons,favoring the formation of stable Cooper pairs.Therefore,T_(c)reaches up to 53 K at a biaxial fracture strain of 5%.Our findings provide valuable insights into the correlation between non-stoichiometric electrides and superconducting microscopic mechanisms at the 2D limit.
基金financially supported by the National Natural Science Foundation of China(Grant No.12141403)the National Key R&D Program of China(Grant No.2022YFA1403100)。
文摘We report on ambipolar modulation doping of monolayer FeSe epitaxial films grown by molecular beam epitaxy and in situ spectroscopic measurements via a cryogenic scanning tunneling microscopy.It is found that hole doping kills superconductivity in monolayer FeSe films on metallic Ir(001)substrates,whereas electron doping from polycrystalline IrO_(2)/SrTiO_(3)substrate enhances significantly the superconductivity with an energy gap of 10.3 meV.By exploring substrate-dependent superconductivity,we elucidate the essential impact of substrate work functions on the superconductivity of monolayer FeSe films.Our results therefore offer a valuable reference guide for further enhancement of the transition temperature Tc in FeSe-based superconductors by interface engineering.
基金the National Natural Science Foundation of China(Grant No.62206030)the Natural Science Foundation of Jiangsu(Grant Nos.BK20220624 and BK20220620)+2 种基金the Scientific Research Foundation of Jiangsu Provincial Education Department(Grant No.21KJB510010)the Changzhou Sci&Tech Program(Grant No.CJ20220085)the Leading Innovative Talents Introduction and Cultivation Project of Changzhou(Grant No.CQ20210084)。
文摘We fabricated monolayer n-type two-dimensional crystalline semiconducting films with millimeter-sized areas and remarkable morphological uniformity using an antisolvent-confined spin-coating method.The antisolvent can cause a downstream Marangoni flow,which improves the film morphologies.The deposited crystalline monolayer films exhibit excellent thermal stabilities after annealing,which reveals the annealing-induced enhancement of crystallinity.The transistors based on the n-type monolayer crystalline films show linear output characteristics and superior electron mobilities.The improved charge injection between monolayer films and Au electrodes results from the energy level shift as the films decrease to the monolayer,which leads to a lower injection barrier.This work demonstrates a promising method for fabricating air-stable,low-cost,high-performance,and large-area organic electronics.
基金Project supported by the National Key R&D Program of China (Grant No.2018YFA0305800)the National Natural Science Foundation of China (Grant Nos.61925111,61888102,and 52102193)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (Grant Nos.XDB28000000 and XDB30000000)CAS Project for Young Scientists in Basic Research (Grant No.YSBR-003)the Fundamental Research Funds for the Central Universities。
文摘Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions(DNLFs).Here,we successfully synthesized a gold telluride(AuTe)monolayer by direct tellurizing an Au(111)substrate.Low energy electron diffraction measurements reveal that it is(2×2)AuTe layer stacked onto(3×3)Au(111)substrate.Moreover,scanning tunneling microscopy images show that the AuTe layer has a honeycomb structure.Scanning transmission electron microscopy reveals that it is a single-atom layer.In addition,first-principles calculations demonstrate that the honeycomb AuTe monolayer exhibits Dirac nodal line features protected by mirror symmetry,which is validated by angle-resolved photoemission spectra.Our results establish that monolayer AuTe can be a good candidate to investigate 2D DNLFs and provides opportunities to realize high-speed low-dissipation devices.
基金supported by the National Key R&D Program of China(Grant No.2022YFA1405102)the National Natural Science Foundation of China(Grant Nos.11874059 and 12174405)+4 种基金the Key Research Program of Frontier Sciences,CAS(Grant No.ZDBS-LY-7021)the Ningbo Key Scientific and Technological Project(Grant No.2021000215)the“Pioneer”and“Leading Goose”R&D Program of Zhejiang Province(Grant No.2022C01053)the Zhejiang Provincial Natural Science Foundation(Grant No.LR19A040002)Beijing National Laboratory for Condensed Matter Physics(Grant No.2021000123)。
文摘Chiral magnetic states are promising for future spintronic applications. Recent progress of chiral spin textures in two-dimensional magnets, such as chiral domain walls, skyrmions, and bimerons, have been drawing extensive attention. Here, via first-principles calculations, we show that biaxial strain can effectively manipulate the magnetic parameters of the Janus Mn Se Te monolayer. Interestingly, we find that both the magnitude and the sign of the magnetic constants of the Heisenberg exchange coupling, Dzyaloshinskii–Moriya interaction and magnetocrystalline anisotropy can be tuned by strain. Moreover, using micromagnetic simulations, we obtain the distinct phase diagram of chiral spin texture under different strains. Especially, we demonstrate that abundant chiral magnetic structures including ferromagnetic skyrmion, skyrmionium, bimeron, and antiferromagnetic spin spiral can be induced in the Mn Se Te monolayer. We also discuss the effect of temperature on these magnetic structures. The findings highlight the Janus Mn Se Te monolayer as a good candidate for spintronic nanodevices.
文摘目的探讨单核细胞单层实验(monocyte monolayer assay,MMA)是否能够用于IgG抗-M相关胎儿新生儿溶血病(hemolytic disease of fetus and newborn,HDFN)的预测。方法选取8例含有IgG抗-M的孕妇并采集血浆标本,其中有胎儿水肿等严重临床症状及无明显临床症状的各4例;8份血浆用二硫苏糖醇(dithiothreitol,DTT)灭活,与M抗原阳性红细胞孵育致敏后,将致敏红细胞与单核细胞混合进行吞噬试验,同时设立阳性及阴性对照,并计算吞噬率;采用t检验对2组吞噬率进行比较。结果4例发生严重抗-M相关HDFN的孕妇的MMA吞噬率分别为15.37%、13.05%、9.17%和24.50%,均值为15.52%;检出IgG抗-M但未发生HDFN的孕妇,其MMA吞噬率分别为8.74%、11.07%、5.12%和6.23%,均值为7.79%,2组吞噬率无差异(P>0.05)。2组吞噬率分别与阴性对照比较均无差异(P>0.05),但均明显低于阳性对照(P<0.05)。结论IgG抗-M介导单核细胞吞噬的能力较低,提示抗-M导致胎儿水肿的机制可能并非红细胞被吞噬破坏而发生的溶血,因此体外单核细胞单层实验可能不适用于IgG抗-M相关HDFN的预测。对于检出IgG抗-M的孕妇,现仍需通过定期监测胎儿大脑中动脉血流,来判断胎儿宫内贫血情况。
