Magnetic proximity effect in the two-dimensional ε-Fe_(2)O_(3)/NbSe_(2)heterojunction

Two-dimensional(2D)magnet/superconductor heterostructures can promote the design of artificial materials for exploring 2D physics and device applications by exotic proximity effects.However,plagued by the low Curie temperature and instability in air,it is hard to realize practical applications for the reported layered magnetic materials at present.In this paper,we developed a space-confined chemical vapor deposition method to synthesize ultrathin air-stable ε-Fe_(2)O_(3) nanosheets with Curie temperature above 350 K.The ε-Fe_(2)O_(3)/NbSe_(2) heterojunction was constructed to study the magnetic proximity effect on the superconductivity of the NbSe_(2) multilayer.The electrical transport results show that the subtle proximity effect can modulate the interfacial spin–orbit interaction while undegrading the superconducting critical parameters.Our work paves the way to construct 2D heterojunctions with ultrathin nonlayered materials and layered van der Waals(vdW)materials for exploring new physical phenomena.

Two‑Dimensional Cr_(5)Te_(8)@Graphite Heterostructure for Efficient Electromagnetic Microwave Absorption

Two-dimensional(2D)transition metal chalcogenides(TMCs)hold great promise as novel microwave absorption materials owing to their interlayer interactions and unique magnetoelectric properties.However,overcoming the impedance mismatch at the low loading is still a challenge for TMCs due to the restricted loss pathways caused by their high-density characteristic.Here,an interface engineering based on the heterostructure of 2D Cr_(5)Te_(8) and graphite is in situ constructed via a one-step chemical vapor deposit to modulate impedance matching and introduce multiple attenuation mechanisms.Intriguingly,the Cr_(5)Te_(8)@EG(ECT)heterostructure exhibits a minimum reflection loss of up to−57.6 dB at 15.4 GHz with a thin thickness of only 1.4 mm under a low filling rate of 10%.The density functional theory calculations confirm that the splendid performance of ECT heterostructure primarily derives from charge redistribution at the abundant intimate interfaces,thereby reinforcing interfacial polarization loss.Furthermore,the ECT coating displays a remarkable radar cross section reduction of 31.9 dB m^(2),demonstrating a great radar microwave scattering ability.This work sheds light on the interfacial coupled stimulus response mechanism of TMC-based heterogeneous structures and provides a feasible strategy to manipulate high-quality TMCs for excellent microwave absorbers.

Ultrafast quasi-three-dimensional imaging

Understanding laser induced ultrafast processes with complex three-dimensional(3D)geometries and extreme property evolution offers a unique opportunity to explore novel physical phenomena and to overcome the manufacturing limitations.Ultrafast imaging offers exceptional spatiotemporal resolution and thus has been considered an effective tool.However,in conventional single-view imaging techniques,3D information is projected on a two-dimensional plane,which leads to significant information loss that is detrimental to understanding the full ultrafast process.Here,we propose a quasi-3D imaging method to describe the ultrafast process and further analyze spatial asymmetries of laser induced plasma.Orthogonally polarized laser pulses are adopted to illuminate reflection-transmission views,and binarization techniques are employed to extract contours,forming the corresponding two-dimensional matrix.By rotating and multiplying the two-dimensional contour matrices obtained from the dual views,a quasi-3D image can be reconstructed.This successfully reveals dual-phase transition mechanisms and elucidates the diffraction phenomena occurring outside the plasma.Furthermore,the quasi-3D image confirms the spatial asymmetries of the picosecond plasma,which is difficult to achieve with two-dimensional images.Our findings demonstrate that quasi-3D imaging not only offers a more comprehensive understanding of plasma dynamics than previous imaging methods,but also has wide potential in revealing various complex ultrafast phenomena in related fields including strong-field physics,fluid dynamics,and cutting-edge manufacturing.

Evolving insights:how DNA repair pathways impact cancer evolution

Viewing cancer as a large,evolving population of heterogeneous cells is a common perspective.Because genomic instability is one of the fundamental features of cancer,this intrinsic tendency of genomic variation leads to striking intratumor heterogeneity and functions during the process of cancer formation,development,metastasis,and relapse.With the increased mutation rate and abundant diversity of the gene pool,this heterogeneity leads to cancer evolution,which is the major obstacle in the clinical treatment of cancer.Cells rely on the integrity of DNA repair machineries to maintain genomic stability,but these machineries often do not function properly in cancer cells.The deficiency of DNA repair could contribute to the generation of cancer genomic instability,and ultimately promote cancer evolution.With the rapid advance of new technologies,such as single-cell sequencing in recent years,we have the opportunity to better understand the specific processes and mechanisms of cancer evolution,and让s relationship with DNA repair.Here,we review recent findings on how DNA repair affects cancer evolution,and discuss how these mechanisms provide the basis for critical clinical challenges and therapeutic applications.

Asymmetric Fraunhofer pattern in Josephson junctions from heterodimensional superlattice V_(5)S_(8)

Introduction of spin-orbit coupling(SOC)in a Josephson junction(JJ)gives rise to unusual Josephson effects.We investigate JJs based on a newly discovered heterodimensional superlattice V_(5)S_(8) with a special form of SOC.The unique homointerface of our JJs enables elimination of extrinsic effects due to interfaces and disorder.We observe asymmetric Fraunhofer patterns with respect to both the perpendicular magnetic field and the current.The asymmetry is influenced by an in-plane magnetic field.Analysis of the pattern points to a nontrivial spatial distribution of the Josephson current that is intrinsic to the SOC in V_(5)S_(8).

Single-Molecule Confinement Induced Intrinsic Multi-Electron Redox-Activity to Enhance Supercapacitor Performance

Aggregation of polyoxometalates(POM)is largely responsible for the reduced performance of POM-based energy-storage systems.To address this challenge,here,the precise confinement of single Keggin-type POM molecule in a porous carbon(PC)of unimodal super-micropore(micro-PC)is realized.Such precise single-molecule confinement enables sufficient activity center exposure and maximum electron-transfer from micro-PC to POM,which well stabilizes the electron-accepting molecules and thoroughly activates its inherent multi-electron redox-activity.In particular,the redox-activities and electron-accepting properties of the confined POM molecule are revealed to be super-micropore pore size-dependent by experiment and spectroscopy as well as theoretical calculation.Meanwhile,the molecularly dispersed POM molecules confined steadily in the“cage”of micro-PC exhibit unprecedented large-negative-potential stability and multiple-peak redox-activity at an ultra-low loading of~11.4 wt%.As a result,the fabricated solid-state supercapacitor achieves a remarkable areal capacitance,ultrahigh energy and power density of 443 mF cm^(-2),0.12 mWh cm^(-2)and 21.1 mW cm^(-2),respectively.This work establishes a novel strategy for the precise confinement of single POM molecule,providing a versatile approach to inducing the intrinsic activity of POMs for advanced energy-storage systems.

Enhancing the cycling stability of Na-ion batteries by bonding MoS2 on assembled carbon-based materials

Room temperature Na-ion batteries(SIBs) show great potential for use as renewable energy storage systems.However, the large-scale application of SIBs has been hindered by the lack of an ideal SIBs anode material. We synthesized MoS2 on carbonized graphene-chitosan(G-C) using the hydrothermal method. The strong interaction between the MoS2 and the G-C greatly improved the electron transport rate and maintained the structural stability of the electrode, which lead to both an excellent rate capability and long cycle stability. The G-C monolith was proven to enhance the electrical conductivity of the composites and served as a matrix for uniformly dispersing active MoS2 nanosheets(NSs), as well as being a buffer material to adapt to changes in volume during the cycle.Serving as an anode material for SIBs, the MoS2-G-C electrode showed good cycling stability(527.3mAh g-1 at100 m A g-1 after 200 cycles), excellent rate capability, and a long cycle life(439.1 m Ah g-1 at 1 A g-1 after 200 cycles).

A–D–A’–D–A type nonfused ring electron acceptors for efficient organic solar cells via synergistic molecular packing and orientation control

Nonfused ring electron acceptors(NFREAs)are promising candidates for future commercialization of organic solar cells(OSCs)due to their simple synthesis.Still,the power conversion efficiencies(PCEs)of NFREA-based OSCs have large room for improvement.In this work,by merging end group halogenation and side chain engineering,we developed four A-D-A’-D-A type NFREAs,which we refer to as EH-4F,C4-4F,EH-4Cl,and C4-4Cl.Single crystal X-ray diffraction revealed that multiple intermolecular S⋅⋅⋅F interactions between cyclopentadithiophene and 5,6-difluoro-3-(dicyanomethylene)indanone could cause an unfavorable dimer formation,leading to ineffectiveπ-πstackings in EH-4F and C4-4F,whereas no such dimer was found in EH-4Cl and C4-4Cl after replacing with 5,6-dichloro-3-(dicyanomethylene)indanone.Moreover,although the shorter n-butyl side chain resulted in a closer molecular packing in C4-4Cl,EH-4Cl(2-ethylhexyl substitution)with proper crystallinity exhibited enhanced face-on orientation in thin film,which is favorable for vertical charge transport and further reducing charge recombination.As a result,a PCE of 13.0%is obtained for EH-4Cl-based OSC with a fill factor of 0.70.This work highlights the importance of molecular packing and orientation control toward future high-performance A-D-A’-D-A type NFREAs.

Excitons in confined molecular aggregates

Organic optoelectronic materials have attracted extensive attention in the past decades due to their wide applications in organic light‐emitting diodes(OLEDs),organic photovoltaics(OPVs),photocatalysis,etc.Significant ad-vancements have been obtained in the material designs based on the insight into the fundamental physics of exciton related to molecular stacking patterns in solid/condensed states.The exciton characteristics and behaviors are not only a starting point for studying photophysical and photochemical processes on a microscopic level,but also a crucial point in determining the optoelec-tronic properties of macroscopic aggregates.This review summarizes the historic development of exciton models,accompanied by the discoveries of special molecular stacking patterns(H‐/J‐/X‐/M‐aggregates),and the competitive de‐excitation pathways of excitons including fluorescence,energy transfer,singlet fission,excimer formation and symmetry‐breaking charge separation in the confined aggregate structures.Additionally,it highlights the capabilities of a correlation between molecular stacking modes and exciton behaviors,which provides new insights and perspectives for optimizing exciton character and behavior through the modulation of molecular arrangement in aggregate states,thereby enhancing the performance of optoelectronic materials.

二维过渡金属硫族化合物的研究进展

二维过渡金属硫族化合物(transition metal dichalcogenides, TMDCs)是继石墨烯之后的新型范德瓦耳斯材料,由于其天然的二维特性以及强自旋轨道耦合作用(spin-orbital coupling, SOC),导致诸如金属-绝缘体转变、电荷密度波(charge density wave, CDW)、能谷电子学、非常规超导电性等新颖物理性质的出现,使得这类材料成为研究低维量子物理的又一理想平台.其中能谷电子学与拓扑超导已经成为近年来凝聚态物理前沿研究的热点方向.本文在综述TMDCs材料的结构与基本物理性质的基础上,重点介绍了最近发展的用于生长原子层厚度的TMDCs材料的熔盐辅助化学气相沉积方法、在Se掺杂的MoSexTe2-x薄膜中实现的Td相到1T′相再到2H相的结构相变与超导增强现象,以及在少层Td-MoTe2中发现的非对称性SOC作用引起的类伊辛超导现象.最后,展望了TMDCs材料的潜在应用与可能存在的拓扑超导.

Diffraction-limited imaging with monolayer 2D material-based ultrathin flat lenses

Ultrathin flat optics allow control of light at the subwavelength scale that is unmatched by traditional refractive optics.To approach the atomically thin limit,the use of 2D materials is an attractive possibility due to their high refractive indices.However,achievement of diffraction-limited focusing and imaging is challenged by their thickness-limited spatial resolution and focusing efficiency.Here we report a universal method to transform 2D monolayers into ultrathin flat lenses.Femtosecond laser direct writing was applied to generate local scattering media inside a monolayer,which overcomes the longstanding challenge of obtaining sufficient phase or amplitude modulation in atomically thin 2D materials.We achieved highly efficient 3D focusing with subwavelength resolution and diffractionlimited imaging.The high focusing performance even allows diffraction-limited imaging at different focal positions with varying magnifications.Our work paves the way for downscaling of optical devices using 2D materials and reports an unprecedented approach for fabricating ultrathin imaging devices.

Raman scattering investigation of twisted WS_(2)/MoS_(2) heterostructures: interlayer mechanical coupling versus charge transfer

Twisted van der Waals homo-and hetero-structures have aroused great attentions due to their unique physical properties,providing a new platform to explore the novel two-dimensional(2D)condensed matter physics.The robust dependence of phonon vibrations and electronic band structures on the twist angle has been intensively observed in transition metal dichalcogenide(TMD)homo-structures.However,the effects of twist angle on the lattice vibrational properties in the TMD heterostructures have not caused enough attention.Here,we report the distinct evolutions of Raman scattering and the underlying interlayer interactions in the twisted WS_(2)/MoS_(2) heterostructures.The shifts and linewidths of E_(2g)(Γ)and A_(1g)(Γ)phonon modes are found to be twist angle dependent.In particular,analogous to that of the twisted TMD homostructures,the frequency separations between E_(2g)(Γ)and A_(1g)(Γ)modes of MoS_(2) and WS_(2) in the twisted heterostructures varying with twist angle correlate with the interlayer mechanical coupling,essentially originating from the spacing-related repulsion between sulfur atoms.Moreover,the opposite shift behaviors and broadening of A_(1g)(Γ)modes caused by charge transfer are also observed in the twisted heterostructures.The calculated interlayer distances and band alignment of twisted WS_(2)/MoS_(2) through density functional theory further evidence our interpretations on the roles of the interlayer mechanical coupling and charge transfer in variations of Raman features.Such understanding and controlling of interlayer interaction through the stacking orientation are significant for future optoelectronic device design based on the newly emerged 2D heterostructures.

Giant excitonic upconverted emission from two-dimensional semiconductor in doubly resonant plasmonic nanocavity

Phonon-assisted upconverted emission is the heart of energy harvesting,bioimaging,optical cryptography,and optical refrigeration.It has been demonstrated that emerging two-dimensional(2D)semiconductors can provide an excellent platform for efficient phonon-assisted upconversion due to the enhanced optical transition strength and phonon-exciton interaction of 2D excitons.However,there is little research on the further enhancement of excitonic upconverted emission in 2D semiconductors.Here,we report the enhanced multiphoton upconverted emission of 2D excitons in doubly resonant plasmonic nanocavities.Owing to the enhanced light collection,enhanced excitation rate,and quantum efficiency enhancement arising from the Purcell effect,an upconverted emission amplification of>1000-fold and a decrease of 2~3 orders of magnitude in the saturated excitation power are achieved.These findings pave the way for the development of excitonic upconversion lasing,nanoscopic thermometry,and sensing,revealing the possibility of optical refrigeration in future 2D electronic or excitonic devices.

Isomerism: Minor Changes in the Bromine Substituent Positioning Lead to Notable Differences in Photovoltaic Performance

An isomerism strategy was employed to develop single,end‐group bromine-substituted non‐fullerene two isomeric acceptors,2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2,"3′′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(4-bromo-3-oxo-2,3-dihydro-1H-inden-1-ylidene)dimalononitrile(BTIC-2Br-β)and 2,2′-((2Z,2′Z)-((12,13-bis(2-ethylhexyl)-3,9-diundecyl-12,13-dihydro-[1,2,5]thiadiazolo[3,4-e]thieno[2,"3′′:4′,5′]thieno[2′,3′:4,5]pyrrolo[3,2-g]thieno[2′,3′:4,5]thieno[3,2-b]indole-2,10-diyl)bis(methanylylidene))bis(5-bromo-3-oxo-2,3-dihydro-1Hinden-1-ylidene)dimalononitrile(BTIC-2Br-γ).

2D/2D atomic double-layer WS_(2)/Nb_(2)O_(5)shell/core nanosheets with ultrafast interfacial charge transfer for boosting photocatalytic H_(2)evolution

Low-efficiency charge transfer is a critical factor to limit the photocatalytic H_(2)evolution activity of semiconductor photocatalysts.The interface design is a promising approach to achieve high chargetransfer efficiency for photocatalysts.Herein,a new 2 D/2 D atomic double-layer WS_(2)/Nb_(2)O_(5)shell/core photocatalyst(DLWS/Nb_(2)O_(5))is designed.The atom-resolved HAADF-STEM results unravel the presence of an unusual 2 D/2 D shell/core interface in DLWS/Nb_(2)O_(5).Taking advantage of the advanced femtosecond-resolved ultrafast TAS spectra,the average lifetime of charge carriers for DLWS/Nb_(2)O_(5)(180.97 ps)is considerably shortened as compared to that of Nb_(2)O_(5)(230.50 ps),strongly indicating that the 2 D/2 D shell/core interface enables DLWS/Nb_(2)O_(5)to achieve ultrafast charge transfer from Nb_(2)O_(5)to atomic double-layer WS_(2),thus yielding a high photocatalytic H_(2)evolution rate of 237.6 mmol/h,up to10.8 times higher than that of pure Nb_(2)O_(5)nanosheet.This study will open a new window for the development of high-efficient photocatalytic systems through the interface design.

Space-confined microwave synthesis of ternary-layered BiOCl crystals with high-performance ultraviolet photodetection

In recent years,two-dimensional(2D)ternary materials have attracted wide attention due to their novel properties which can be achieved by regulating their chemical composition with a very great degree of freedom and adjustable space.However,as for the precise synthesis of 2D ternary materials,great challenges still lie ahead that hinder their further development.In this work,we demonstrated a simple and reliable approach to synthesize 2D ternary-layered BiOCl crystals through a microwave-assisted space-confined process in a short time(<3 minutes).Their ultraviolet(UV)detection performance was analyzed systematically.The photodetectors based on the as-obtained BiOCl platelets demonstrate high sensitivity to 266-nm laser illumination.The responsivity is calculated to be8 A/W and the response time is up to be18 ps.On the other hand,the device is quite stable after being exposed in the ambient air within 3 weeks and the response is almost unchanged during the measurement.The facile and fast synthesis of single crystalline BiOCl platelets and its high sensitivity to UV light irradiation indicate the potential optoelectronic applications of 2D BiOCl photodetectors.

A universal method for rapid and large‐scale growth of layered crystals

Layered van der Waals(vdW)materials,consisting of atomically thin layers,are of paramount importance in physics,chemistry,and materials science owing to their unique properties and various promising applications.However,their fast and large‐scale growth via a general approach is still a big challenge,severely limiting their practical implementations.Here,we report a universal method for rapid(~60 min)and large‐scale(gram scale)growth of phase‐pure,high‐crystalline layered vdW materials from their elementary powders via microwave plasma heating in sealed ampoules.This method can be used for growth of 30 compounds with different components(binary,ternary,and quaternary)and properties.The ferroelectric and transport properties of mechanically exfoliated flakes validate the high crystal quality of the grown materials.Our study provides a general strategy for the fast and large‐scale growth of layered vdW materials with appealing physiochemical properties,which could be used for various promising applications.

Preparation and electronic characteristics of anionic perylene bisimide films

Neutral perylene bisimides(PBI) are well-known n-type organic semiconductors, with number of challenging electronic properties in their neutral and reduced states. We report the characteristic electronic properties of PBI anionic films. We unexpectedly discovered that pristine PBI dianion film showed p-type character, while oxidized dianion film(dominant neutral state with few radical anions) showed normal n-type semiconductor character based on Seebeck effect measurements. Both kinds of films exhibit high electrical conductivity with a potential for thermoelectric applications. The mechanism of polarity reversal is proposed.

Enhancing photovoltaic performance via aggregation dynamics control in fused-ring electron acceptor

A new fused-ring electron acceptor FNIC3 with dynamics controlled aggregation behavior was synthesized.FNIC3 shows strong absorption in 600–900 nm,HOMO/LUMO energy levels of−5.59/−4.04 eV,and electron mobility of 1.2×10^(−3) cm^(2) V^(−1) s^(−1).The aggregation of FNIC3 shows strong dependency on film formation time.Prolongation of film formation time promotes the crystallization of FNIC3,leading to improved crystallinity and enlarged aggregate sizes.Aggregation of FNIC3 significantly influences the photovoltaic device parameters.Appropriate aggregation red-shifts the absorption and improves the mobilities of the blend,which contributes to high photocurrent and fill factor thus high power conversion efficiency(PCE).Overaggregation leads to increased nonradiative energy loss and insufficient charge generation,resulting in decreased open-circuit voltage and short-circuit current density.The blends based on PM6:FNIC3 fabricated under proper film formation time exhibit a PCE of 12.3%,higher than those fabricated under short and long film formation time(10.0–10.5%).