With a large number of researches being conducted on two?dimen?sional(2D) materials, their unique properties in optics, electrics, mechanics, and magnetics have attracted increasing attention. Accordingly, the idea of...With a large number of researches being conducted on two?dimen?sional(2D) materials, their unique properties in optics, electrics, mechanics, and magnetics have attracted increasing attention. Accordingly, the idea of combining distinct functional 2D materials into heterostructures naturally emerged that pro?vides unprecedented platforms for exploring new physics that are not accessible in a single 2D material or 3D heterostructures. Along with the rapid development of controllable, scalable, and programmed synthesis techniques of high?quality 2D heterostructures, various heterostructure devices with extraordinary performance have been designed and fabricated, including tunneling transistors, photodetectors, and spintronic devices. In this review, we present a summary of the latest progresses in fabrications, properties, and applications of di erent types of 2D heterostruc?tures, followed by the discussions on present challenges and perspectives of further investigations.展开更多
As an environmentally friendly and high-density energy carrier,hydrogen has been recognized as one of the ideal alternatives for fossil fuels.One of the major challenges faced by“hydrogen economy”is the development ...As an environmentally friendly and high-density energy carrier,hydrogen has been recognized as one of the ideal alternatives for fossil fuels.One of the major challenges faced by“hydrogen economy”is the development of efficient,low-cost,safe and selective hydrogen generation from chemical storage materials.In this review,we summarize the recent advances in hydrogen production via hydrolysis and alcoholysis of light-metal-based materials,such as borohydrides,Mg-based and Al-based materials,and the highly efficient regeneration of borohydrides.Unfortunately,most of these hydrolysable materials are still plagued by sluggish kinetics and low hydrogen yield.While a number of strategies including catalysis,alloying,solution modification,and ball milling have been developed to overcome these drawbacks,the high costs required for the“one-pass”utilization of hydrolysis/alcoholysis systems have ultimately made these techniques almost impossible for practical large-scale applications.Therefore,it is imperative to develop low-cost material systems based on abundant resources and effective recycling technologies of spent fuels for efficient transport,production and storage of hydrogen in a fuel cell-based hydrogen economy.展开更多
Spintronics,exploiting the spin degree of electrons as the information vector,is an attractive field for implementing the beyond Complemetary metal-oxide-semiconductor(CMOS)devices.Recently,two-dimensional(2D)material...Spintronics,exploiting the spin degree of electrons as the information vector,is an attractive field for implementing the beyond Complemetary metal-oxide-semiconductor(CMOS)devices.Recently,two-dimensional(2D)materials have been drawing tremendous attention in spintronics owing to their distinctive spin-dependent properties,such as the ultralong spin relaxation time of graphene and the spin-valley locking of transition metal dichalcogenides.Moreover,the related heterostructures provide an unprecedented probability of combining the di erent characteristics via proximity e ect,which could remedy the limitation of individual 2D materials.Hence,the proximity engineering has been growing extremely fast and has made significant achievements in the spin injection and manipulation.Nevertheless,there are still challenges toward practical application;for example,the mechanism of spin relaxation in 2D materials is unclear,and the high-effciency spin gating is not yet achieved.In this review,we focus on 2D materials and related heterostructures to systematically summarize the progress of the spin injection,transport,manipulation,and application for information storage and processing.We also highlight the current challenges and future perspectives on the studies of spintronic devices based on 2D materials.展开更多
Fluorescence lifetime imaging microscopy(FLIM)has been rapidly developed over the past 30 years and widely applied in biomedical engineering.Recent progress in fluorophore-dyed probe design has widened the application...Fluorescence lifetime imaging microscopy(FLIM)has been rapidly developed over the past 30 years and widely applied in biomedical engineering.Recent progress in fluorophore-dyed probe design has widened the application prospects of fluorescence.Because fluorescence lifetime is sensitive to microenvironments and molecule alterations,FLIM is promising for the detection of pathological conditions.Current cancer-related FLIM applications can be divided into three main categories:(i)FLIM with autofluorescence molecules in or out of a cell,especially with reduced form of nicotinamide adenine dinucleotide,and flavin adenine dinucleotide for cellular metabolism research;(ii)FLIM with Förster resonance energy transfer for monitoring protein interactions;and(iii)FLIM with fluorophore-dyed probes for specific aberration detection.Advancements in nanomaterial production and efficient calculation systems,as well as novel cancer biomarker discoveries,have promoted FLIM optimization,offering more opportunities for medical research and applications to cancer diagnosis and treatment monitoring.This review summarizes cutting-edge researches from 2015 to 2020 on cancer-related FLIM applications and the potential of FLIM for future cancer diagnosis methods and anti-cancer therapy development.We also highlight current challenges and provide perspectives for further investigation.展开更多
Moirésuperlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission applications.Concurrently,the manipulation of s...Moirésuperlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission applications.Concurrently,the manipulation of strain provides a versatile strategy to finely adjust electronic band structures,enhance exciton luminescence efficiency,and establish a robust foundation for two-dimensional quantum light sources.However,the intricate interplay between strain and moirépotential remains partially unexplored.Here,we introduce a meticulously designed fusion of strain engineering and the twisted 2L-WSe_(2)/2L-WSe_(2) homobilayers,resulting in the precise localization of moiréexcitons.Employing low-temperature photoluminescence spectroscopy,we unveil the emergence of highly localized moiré-enhanced emission,characterized by the presence of multiple distinct emission lines.Furthermore,our investigation demonstrates the effective regulation of moirépotential depths through strain engineering,with the potential depths of strained and unstrained regions differing by 91%.By combining both experimental and theoretical approaches,our study elucidates the complex relationship between strain and moirépotential,thereby opening avenues for generating strain-induced moiréexciton single-photon sources.展开更多
Recently,the discovery of a variety of moiré-related properties in the twisted vertical stacking of two different monolayers has attracted considerable attention.The introduction of small twist angles in transiti...Recently,the discovery of a variety of moiré-related properties in the twisted vertical stacking of two different monolayers has attracted considerable attention.The introduction of small twist angles in transition metal dichalcogenide(TMD)heterostructures leads to the emergence of moirépotentials,which provide a fascinating platform for the study of strong interactions of electrons.While there has been extensive research on moiréexcitons in twisted bilayer superlattices,the capture and study of moiréexcitons in homostructure superlattices with layer-coupling effects remain elusive.Here,we present the observation of moiréexcitons in the twisted 1L-WSe_(2)/1L-WSe_(2)and 1L-WSe_(2)/2L-WSe_(2)homostructures with various layer-coupling interactions.The results reveal that the moirépotential increases(~260%)as the number of underlying layers decreases,indicating the effect of layer coupling on the modulation of the moirépotential.The effects of the temperature and laser power dependence as well as valley polarization on moiréexcitons were further demonstrated,and the crucial spectral features observed were explained.Our findings pave the way for exploring quantum phenomena and related applications of quantum information.展开更多
The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)materials.In graphene and transition...The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)materials.In graphene and transition metal dichalcogenides(TMDs)moirésystems,twist angle has been shown to be a key parameter for regulating the moirésuperlattice.However,the effect of the modulation of the twist angle on moirépotential and interlayer coupling has not been the subject of experimental investigation.Here,we report the observation of the modulation of moirépotential and intralayer excitons in the WS_(2)/WS_(2)homostructure.By accurately adjusting the torsion angle of the homobilayers,the depth of the moirépotential can be modulated.The confinement effect of the moirépotential on the intralayer excitons was further demonstrated by the changing of temperature and valley polarization.Furthermore,we show that a detection of atomic reconstructions by the low-frequency Raman mapping to map out inhomogeneities in moirélattices on a large scale,which endows the uniformity of interlayer coupling.Our results provide insights for an in-depth understanding of the behaviors of moiréexcitons in the twisted van der Waals homostructure,and promote the study of electrical engineering and topological photonics.展开更多
Moirésuperlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional materials.The periodic moirépatterns generated by these structu...Moirésuperlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional materials.The periodic moirépatterns generated by these structures lead to the formation of flat mini-bands,which alter the electronic energy bands of the material.The resulting flat electronic bands can greatly enhance strong correlative interactions between electrons,leading to the emergence of exotic quantum phenomena,including moiréphonons and moiréexcitons.While extensive research has been conducted on the exotic quantum phenomena in twisted bilayers of transition metal dichalcogenides(TMDs),and the regulatory effect of stacked layers on moiréexcitons remains unexplored.In this study,we report the fabrication of a twisted WSe_(2)/WSe_(2)/WSe_(2) homotrilayer with two twist angles and investigate the influence of stacked layers on moiréexcitons.Our experiments reveal multiple moiréexciton splitting peaks in the twisted trilayer,with moirépotential depths of 78 and 112 meV in the bilayer and trilayer homostructures,respectively.We also observed the splitting of the moiréexcitons at 90 K,indicating the presence of a deeper moirépotential in the twisted trilayer.Moreover,we demonstrate that stacked layers can tune the moiréexcitons by manipulating temperature,laser power,and magnetic field.Our results provide a new physical model for studying moirésuperlattices and their quantum properties,which could potentially pave the way for the development of quantum optoelectronics.展开更多
The stacking of twisted two-dimensional(2D)layered materials has led to the creation of moirésuperlattices,which have become a new platform for the study of quantum optics.The strong coupling of moirésuperla...The stacking of twisted two-dimensional(2D)layered materials has led to the creation of moirésuperlattices,which have become a new platform for the study of quantum optics.The strong coupling of moirésuperlattices can result in flat minibands that boost electronic interactions and generate interesting strongly correlated states,including unconventional superconductivity,Mott insulating states,and moiréexcitons.However,the impact of adjusting and localizing moiréexcitons in Van der Waals heterostructures has yet to be explored experimentally.Here,we present experimental evidence of the localization-enhanced moiréexcitons in the twisted WSe_(2)/WS_(2)/WSe_(2)heterotrilayer with type-II band alignments.At low temperatures,we observed multiple excitons splitting in the twisted WSe_(2)/WS_(2)/WSe_(2)heterotrilayer,which is manifested as multiple sharp emission lines,in stark contrast to the moiréexcitonic behavior of the twisted WSe_(2)/WS_(2)heterobilayer(which has a linewidth 4 times wider).This is due to the enhancement of the two moirépotentials in the twisted heterotrilayer,enabling highly localized moiréexcitons at the interface.The confinement effect of moirépotential on moiréexcitons is further demonstrated by changes in temperature,laser power,and valley polarization.Our findings offer a new approach for localizing moiréexcitons in twist-angle heterostructures,which has the potential for the development of coherent quantum light emitters.展开更多
Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exh...Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exhibit emerging valley pseudospins,making them ideal platforms for studying valley electronics.However,intervalley scattering of different energy valleys limits the achievable degree of valley polarization.Here,we constructed WSe_(2)/yttrium iron garnet(YIG)heterostructures and demonstrated that the interfacial magnetic exchange effect on the YIG magnetic substrate can enhance valley polarization by up to 63%,significantly higher than that of a monolayer WSe_(2)on SiO_(2)/Si(11%).Additionally,multiple sharp exciton peaks appear in the WSe_(2)/YIG heterostructures due to the strong magnetic proximity effect at the magnetic-substrate interface that enhances exciton emission efficiency.Moreover,under the effect of external magnetic field,the magnetic direction of the magnetic substrate enhances valley polarization,further demonstrating that the magnetic proximity effect regulates valley polarization.Our results provide a new way to regulate valley polarization and demonstrate the promising application of magnetic heterojunctions in magneto-optoelectronics.展开更多
Valley degree of freedom in the first Brillouin zone of Bloch electrons offers an innovative approach to information storage and quantum computation.Broken inversion symmetry together with the presence of time-reversa...Valley degree of freedom in the first Brillouin zone of Bloch electrons offers an innovative approach to information storage and quantum computation.Broken inversion symmetry together with the presence of time-reversal symmetry endows Bloch electrons non-zero Berry curvature and orbital magnetic moment,which contribute to the valley Hall effect and optical selection rules in valleytronics.Furthermore,the emerging transition metal dichalcogenides(TMDs)materials naturally become the ideal candidates for valleytronics research attributable to their novel structural,photonic and electronic properties,especially the direct bandgap and broken inversion symmetry in the monolayer.However,the mechanism of inter-valley relaxation remains ambiguous and the complicated manipulation of valley predominantly incumbers the realization of valleytronic devices.In this review,we systematically demonstrate the fundamental properties and tuning strategies(optical,electrical,magnetic and mechanical tuning)of valley degree of freedom,summarize the recent progress of TMD-based valleytronic devices.We also highlight the conclusion of present challenges as well as the perspective on the further investigations in valleytronics.展开更多
The extraordinary optical and electronic properties of anisotropic two-dimensional materials,such as black phosphorus,ReS2,and GeSe,enable them a promising component of polarization-sensitive photodetectors.However,th...The extraordinary optical and electronic properties of anisotropic two-dimensional materials,such as black phosphorus,ReS2,and GeSe,enable them a promising component of polarization-sensitive photodetectors.However,these applications are significantly limited by the challenges of air-stability,response time,and linearly dichroic ratio.Interestingly,palladium diselenide(PdSe2)with high air stability is an emerging material that has robust in-plane anisotropy induced by its asymmetric pentagonal lattice structure.We have successfully prepared a few-layer PdSe2 using micromechanical exfoliation,and here we demonstrate the strong linear dichroism behavior of PdSe2 by polarization-resolved absorption spectra measurements.Such unique linear dichroism,endows the PdSe2 photodetector powerful ability to detect polarized light.The photodetector based on 5L PdSe2,as tested with polarization-dependent photocurrent mapping,exhibited competitive capability to detect polarized light,achieving a significant photocurrent on/off ratio(>10^2),the quite fast response time(<11 ms)and robust linearly dichroic ratios(/max//min≈1.9 at 532 nm).These results are essential advance in the development of polarization-sensitive photodetector,a crucial step towards opening up a new avenue for the application of 2D optoelectronic devices.展开更多
Interlayer excitons(IXS)are electron–hole pairs bound in the spatial separation layer by the Coulomb effect,and their lifetime is several orders of magnitude longer than that of direct excitons,providing an essential...Interlayer excitons(IXS)are electron–hole pairs bound in the spatial separation layer by the Coulomb effect,and their lifetime is several orders of magnitude longer than that of direct excitons,providing an essential platform for long-lived exciton devices.The recent emergence of the van der Waals heterostructure(HS),which combines two layers of different transitional metal dichalcogenides(TMDs),has created new opportunities for IX research.Herein,we demonstrate the observation of double indirect interlayer excitons in the MoSe_(2)/WSe_(2)HS using photoluminescence(PL)spectroscopy.The intensities of the two peaks are essentially the same,and the energy difference is 22 meV,which is perfectly in line with the calculation result of density functional theory.Furthermore,the experience of variable excitation power also proves that the splitting of the IXs originates from the conduction band spin-splitting of MoSe_(2).The observation results provide a promising platform for further exploring the new physical properties and optoelectronic phenomena of TMD HS.展开更多
Van der Waals’two-dimensional(2D)material heterostructure engineering offers an effective strategy for the design of multifunctional and high-performance optoelectronic devices.However,2D heterostructure photodetecto...Van der Waals’two-dimensional(2D)material heterostructure engineering offers an effective strategy for the design of multifunctional and high-performance optoelectronic devices.However,2D heterostructure photodetectors with a photoconductive effect tend to suffer from high driving source-drain voltages and significant dark noise currents.Herein,a self-powered photodetector with high performance was fabricated based on vertically stacked graphene/MoSe_(2)/PdSe_(2)/graphene heterojunctions through a dry transfer method.The fabricated device displays current rectification characteristics in darkness(on/off ratio>10^(3))and superior photovoltaic behaviors under illumination.In addition,benefitting from the strong built-in field,the Gr/PdSe_(2)/MoSe_(2)/Gr heterojunction photodetector is able to respond to a broad spectrum from visible to near-infrared(NIR)with a remarkable responsivity of 651 mA·W^(−1),a high specific detectivity of 5.29×10^(11) Jones and a fast response speed of 41.7/62.5μs.Moreover,an enhanced responsivity of 1.16 A·W^(−1) has been obtained by a reverse voltage(−1 V)and further evaluation on image recognition has also demonstrated the great application potential of the Gr/MoSe_(2)/PdSe_(2)/Gr heterojunction photodetector.The findings are expected to bring new opportunities for the development of highly sensitive,high-speed and energy-efficient photodetectors for comprehensive applications.展开更多
Pentacoordinated Al(Al~Ⅴ)species in silica-alumina are promising to promote the formation of acid sites or act as surface defects for tailoring single-atom catalysts.However,pentahedral coordination(Al~Ⅴ)is rarely o...Pentacoordinated Al(Al~Ⅴ)species in silica-alumina are promising to promote the formation of acid sites or act as surface defects for tailoring single-atom catalysts.However,pentahedral coordination(Al~Ⅴ)is rarely observed in conventionally prepared silica-alumina.Here,we show that high population and dispersion of Al~Ⅴ species on the surface of amorphous silica-alumina(ASA)can be achieved by means of flame spray pyrolysis.High resolution TEM/EDX,high magnetic-field NMR and DFT calculations are employed to characterize the structure of as-prepared ASAs.Solid-state ^(27)Al multi-quantum MAS NMR experiments show that most of the Al~Ⅴspecies are formed independently from the alumina phase and are accessible for guest molecules on the surface.Upon water adsorption,these Al~Ⅴ species are transformed to Al~Ⅵ species,structurally similar to surface Al~Ⅳ species,as confirmed by DFT calculations.The outstanding catalytic activity of as-synthesized ASA is demonstrated using the in situ H/D exchange reaction with deuterated benzene as an example.The Al~Ⅴ-rich ASA provides a much lower activation energy(~30 kJ/mol)than that reported for zeolite H-ZSM-5(~60 kJ/mol).The superior catalytic performance is attributed to the high Al~Ⅴcontent promoting the surface active sites in ASA.The knowledge gained on the synthesis of Al~Ⅴ-rich ASAs and the nature of aluminum coordination in these materials could pave the way to more efficient silica-alumina based catalysts.展开更多
Recent advances in twisted van der Waals heterostructure superlattices have emerged as a powerful and attractive platform for exploring novel condensed matter physics due to the interplay between the moirépotenti...Recent advances in twisted van der Waals heterostructure superlattices have emerged as a powerful and attractive platform for exploring novel condensed matter physics due to the interplay between the moirépotential and Coulomb interactions.The moirésuperlattices act as a periodic confinement potential in space to capture interlayer excitons(IXs),resulting in moiréexciton arrays,which provide opportunities for quantum emitters and many-body physics.The observation of moiréIXs in twisted transition-metal dichalcogenide(TMD)heterostructures has recently been widely reported.However,the capture and study of the moiréintralayer excitons based on TMD twisted homobilayer(T-HB)remain elusive.Here,we report the observation of moiréintralayer excitons in a WSe_(2)/WSe_(2) T-HB with a small twist angle by measuring PL spectrum.The multiple split peaks with an energy range of 1.55-1.73 eV are different from that of the monolayer WSe_(2) exciton peaks.The split peaks were caused by the trapping of intralayer excitons via the moirépotential.The confinement effect of the moirépotential on the moiréintralayer excitons was further demonstrated by the changing of temperature,laser power,and valley polarization.Our findings provide a new avenue for exploring new correlated quantum phenomena and their applications.展开更多
Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the d...Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the design of optoelectronic devices.However,the bilayer heterostructure with type-II band alignment can only produce low quantum yield.Here,we present the observation of interlayer neutral excitons and trions in the MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure(Tri-HS).In comparison to the 8 K bilayer heterostructure,the addition of a MoSe_(2)layer to the Tri-HS can significantly increase the quantum yield of IXs.It is believed the two symmetrical type-II band alignments formed in the Tri-HS could effectively promote the IX radiation recombination.By analyzing the photoluminescence(PL)spectrum of the IXs at cryogenic temperature and the power dependence,the existence of the interlayer trions was confirmed.Our results provide a promising platform for the development of more efficient optoelectronic devices and the investigation of new physical properties of TMDs.展开更多
Vertically stacked transition metal dichalcogenide(TMD)heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional limit.In such structures,spatially indirect interlayer exc...Vertically stacked transition metal dichalcogenide(TMD)heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional limit.In such structures,spatially indirect interlayer excitons(IXs)can be generated in adjacent layers because of strong Coulomb interactions.However,due to the complexity of the multilayered heterostructure(HS),the capture and study of the IXs in trilayer type-Ⅱ HSs have so far remained elusive.Here,we present the observation of the IXs in trilayer type-Ⅱ staggered band alignment of MoS_(2)/MoSe_(2)/WSe_(2) van der Waals(vdW)HSs by photoluminescence(PL)spectroscopy.The central energy of IX is 1.33 eV,and the energy difference between the extracted double peaks is 23 meV.We confirmed the origin of IX through PL properties and calculations by the density functional theory,we also studied the dependence of the IX emission peak on laser power and temperature.Furthermore,the polarization-resolved PL spectra of HS were also investigated,and the maximum polarizability of the emission peak of WSe_(2) reached 11.40%at 6 K.Our findings offer opportunities for the study of new physical properties of excitons in TMD HSs and therefore are valuable for exploring the potential applications of TMDs in optoelectronic devices.展开更多
Moirésuperlattices are formed by a lattice mismatch or twist angle in two-dimensional materials,which can generate periodical moirépotentials leading to strong changes in the band structure,resulting in new ...Moirésuperlattices are formed by a lattice mismatch or twist angle in two-dimensional materials,which can generate periodical moirépotentials leading to strong changes in the band structure,resulting in new quantum phenomena.However,the experimental engineering of in-situ deformation of moiréheterostructures remains deficient.Here,we demonstrate a dynamic local deformation of the twisted heterostructures using a diamond anvil cell(DAC),enabling in-situ dynamic modulation of moirépotential in twisted WS_(2)–WSe_(2)heterostructures at room temperature.Deformation of the twisted heterostructure increases the moirépotential,causing a red shift of the moiréexciton resonance,and observed the red shift of the intralayer exciton resonance up to 16.3 meV(less than 1.1 GPa).The blue shift of the interlayer excitons of twisted WS_(2)–WSe_(2)heterostructures shows an evident transition of the pressure sensitive exciton,induced by the dominant effect of modifying the band structure on optical properties.Combined with the spectral changes of pressurized Raman,which further demonstrated that the DAC can efficiently regulate the interlayer coupling.Our results offer an effective strategy for in-situ dynamic modulation of moirépotential,providing a promising platform for the development of novel quantum devices.展开更多
基金supported by NSF of China (Grant No. 61775241)partly by the Innovation-driven Project (Grant No. 2017CX019)the funding support from the Australian Research Council (ARC Discovery Projects, DP180102976)
文摘With a large number of researches being conducted on two?dimen?sional(2D) materials, their unique properties in optics, electrics, mechanics, and magnetics have attracted increasing attention. Accordingly, the idea of combining distinct functional 2D materials into heterostructures naturally emerged that pro?vides unprecedented platforms for exploring new physics that are not accessible in a single 2D material or 3D heterostructures. Along with the rapid development of controllable, scalable, and programmed synthesis techniques of high?quality 2D heterostructures, various heterostructure devices with extraordinary performance have been designed and fabricated, including tunneling transistors, photodetectors, and spintronic devices. In this review, we present a summary of the latest progresses in fabrications, properties, and applications of di erent types of 2D heterostruc?tures, followed by the discussions on present challenges and perspectives of further investigations.
基金This work was financially supported by the National Key R&D Program of China(2018YFB1502101)the Foundation for Innovative Research Groups of the National Natural Science Foundation of China(NSFC51621001)+2 种基金National Natural Science Foundation of China Projects(51771075)Natural Science Foundation of Guangdong Province of China(2016A030312011)Z.L.acknowledges the funding support from the Australian Research Council(ARC Discovery Projects,DP180102976 and DP210103539).
文摘As an environmentally friendly and high-density energy carrier,hydrogen has been recognized as one of the ideal alternatives for fossil fuels.One of the major challenges faced by“hydrogen economy”is the development of efficient,low-cost,safe and selective hydrogen generation from chemical storage materials.In this review,we summarize the recent advances in hydrogen production via hydrolysis and alcoholysis of light-metal-based materials,such as borohydrides,Mg-based and Al-based materials,and the highly efficient regeneration of borohydrides.Unfortunately,most of these hydrolysable materials are still plagued by sluggish kinetics and low hydrogen yield.While a number of strategies including catalysis,alloying,solution modification,and ball milling have been developed to overcome these drawbacks,the high costs required for the“one-pass”utilization of hydrolysis/alcoholysis systems have ultimately made these techniques almost impossible for practical large-scale applications.Therefore,it is imperative to develop low-cost material systems based on abundant resources and effective recycling technologies of spent fuels for efficient transport,production and storage of hydrogen in a fuel cell-based hydrogen economy.
基金partially supported by the National Natural Science Foundation of China(Grant No.61775241)the Youth Innovation Team(Grant No:2019012)of CSU+3 种基金the Hunan province key research and development project(Grant No:2019GK2233)Hunan Province Graduate Research and Innovation Project(Grant No:CX20190177)the Science and Technology Innovation Basic Research Project of Shenzhen(Grant No.JCYJ20180307151237242)the funding support from the Australian Research Council(ARC Discovery Project,DP180102976).
文摘Spintronics,exploiting the spin degree of electrons as the information vector,is an attractive field for implementing the beyond Complemetary metal-oxide-semiconductor(CMOS)devices.Recently,two-dimensional(2D)materials have been drawing tremendous attention in spintronics owing to their distinctive spin-dependent properties,such as the ultralong spin relaxation time of graphene and the spin-valley locking of transition metal dichalcogenides.Moreover,the related heterostructures provide an unprecedented probability of combining the di erent characteristics via proximity e ect,which could remedy the limitation of individual 2D materials.Hence,the proximity engineering has been growing extremely fast and has made significant achievements in the spin injection and manipulation.Nevertheless,there are still challenges toward practical application;for example,the mechanism of spin relaxation in 2D materials is unclear,and the high-effciency spin gating is not yet achieved.In this review,we focus on 2D materials and related heterostructures to systematically summarize the progress of the spin injection,transport,manipulation,and application for information storage and processing.We also highlight the current challenges and future perspectives on the studies of spintronic devices based on 2D materials.
基金This work was partially supported by the National Natural Science Foundation of China(Grant No.61775241)the Hunan Science Fund for Distinguished Young Scholar(2020JJ2059)+3 种基金Youth Innovation Team(Grant No.2019012)of CSU,Hunan province key research and development project(Grant No.2019GK2233,Grant 2020SK2053)Hunan Province Graduate Research and Innovation Project(Grant No.CX20190177)the Science and Technology Innovation Basic Research Project of Shenzhen(Grant No.JCYJ20180307151237242)Also,YPL acknowledges the support by the Project of State Key Laboratory of High-Performance Complex Manufacturing,Central South University(Grant No.ZZYJKT2020-12).Besides,we acknowledge the art work from Servier Medical Art.Y.Z.O and Y.P.L contributed equally to this work.
文摘Fluorescence lifetime imaging microscopy(FLIM)has been rapidly developed over the past 30 years and widely applied in biomedical engineering.Recent progress in fluorophore-dyed probe design has widened the application prospects of fluorescence.Because fluorescence lifetime is sensitive to microenvironments and molecule alterations,FLIM is promising for the detection of pathological conditions.Current cancer-related FLIM applications can be divided into three main categories:(i)FLIM with autofluorescence molecules in or out of a cell,especially with reduced form of nicotinamide adenine dinucleotide,and flavin adenine dinucleotide for cellular metabolism research;(ii)FLIM with Förster resonance energy transfer for monitoring protein interactions;and(iii)FLIM with fluorophore-dyed probes for specific aberration detection.Advancements in nanomaterial production and efficient calculation systems,as well as novel cancer biomarker discoveries,have promoted FLIM optimization,offering more opportunities for medical research and applications to cancer diagnosis and treatment monitoring.This review summarizes cutting-edge researches from 2015 to 2020 on cancer-related FLIM applications and the potential of FLIM for future cancer diagnosis methods and anti-cancer therapy development.We also highlight current challenges and provide perspectives for further investigation.
基金supported this research endeavor.Notably,the National Natural Science Foundation of China(No.52373311)the Science Talent Program of China,the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)+10 种基金the Hunan Province Key Research and Development Project(No.2019GK2233)the Youth Innovation Team(No.2019012)of Central South University(CSU)have played an essential role in facilitating the success of this study.Furthermore,the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the Key Program of the Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)have also made significant contributions to the advancement of this workThe support provided by the High-Performance Complex Manufacturing Key State Lab Project at CSU(No.ZZYJKT2020-12)has been of immeasurable value,greatly expediting the research processAcknowledgment is also extended to the Australian Research Council(ARC Discovery Project,DP180102976)for its pivotal role in driving forward this research agenda.AdditionallyJ.T.W.extends gratitude for the support received from the National Natural Science Foundation of China(Nos.92263202 and 11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)the National Key Research and Development Program of China(No.2020YFA0711502)The authors also wish to convey their deep appreciation to the Beijing Super Cloud Computing Center(BSCC,http://www.blsc.cn)for granting access to high-performance computing(HPC)resources,which have been instrumental in yielding the research outcomes detailed in this paper.Finally,the authors hold profound gratitude for the support of the Postdoctoral Science Foundation of China(No.2022M713546)a vital contribution that has substantially propelled the advancement of this research endeavor.This work was supported in part by the High-Performance Computing Center of Central South University.
文摘Moirésuperlattices,arising from the controlled twisting of van der Waals homostructures at specific angles,have emerged as a promising platform for quantum emission applications.Concurrently,the manipulation of strain provides a versatile strategy to finely adjust electronic band structures,enhance exciton luminescence efficiency,and establish a robust foundation for two-dimensional quantum light sources.However,the intricate interplay between strain and moirépotential remains partially unexplored.Here,we introduce a meticulously designed fusion of strain engineering and the twisted 2L-WSe_(2)/2L-WSe_(2) homobilayers,resulting in the precise localization of moiréexcitons.Employing low-temperature photoluminescence spectroscopy,we unveil the emergence of highly localized moiré-enhanced emission,characterized by the presence of multiple distinct emission lines.Furthermore,our investigation demonstrates the effective regulation of moirépotential depths through strain engineering,with the potential depths of strained and unstrained regions differing by 91%.By combining both experimental and theoretical approaches,our study elucidates the complex relationship between strain and moirépotential,thereby opening avenues for generating strain-induced moiréexciton single-photon sources.
基金the National Natural Science Foundation of China(No.61775241)Hunan province key research and development project(No.2019GK2233)+9 种基金Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the Youth Innovation Team(No.2019012)of CSUthe Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)support of the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)the Australian Research Council(ARC Discovery Project,No.DP180102976)the National Natural Science Foundation of China(No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)the National Key Research and Development Program of China(No.2020YFA0711502).
文摘Recently,the discovery of a variety of moiré-related properties in the twisted vertical stacking of two different monolayers has attracted considerable attention.The introduction of small twist angles in transition metal dichalcogenide(TMD)heterostructures leads to the emergence of moirépotentials,which provide a fascinating platform for the study of strong interactions of electrons.While there has been extensive research on moiréexcitons in twisted bilayer superlattices,the capture and study of moiréexcitons in homostructure superlattices with layer-coupling effects remain elusive.Here,we present the observation of moiréexcitons in the twisted 1L-WSe_(2)/1L-WSe_(2)and 1L-WSe_(2)/2L-WSe_(2)homostructures with various layer-coupling interactions.The results reveal that the moirépotential increases(~260%)as the number of underlying layers decreases,indicating the effect of layer coupling on the modulation of the moirépotential.The effects of the temperature and laser power dependence as well as valley polarization on moiréexcitons were further demonstrated,and the crucial spectral features observed were explained.Our findings pave the way for exploring quantum phenomena and related applications of quantum information.
基金the National Natural Science Foundation of China(No.61775241)Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)+3 种基金the Youth Innovation Team(No.2019012)of CSU,Hunan province key research and development project(No.2019GK2233)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)support of the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)Z.W.L.thanks the support from the Australian Research Council(ARC Discovery Project,DP180102976).
文摘The formation of moirésuperlattices in twisted van der Waals(vdW)homostructures provides a versatile platform for designing the electronic band structure of two-dimensional(2D)materials.In graphene and transition metal dichalcogenides(TMDs)moirésystems,twist angle has been shown to be a key parameter for regulating the moirésuperlattice.However,the effect of the modulation of the twist angle on moirépotential and interlayer coupling has not been the subject of experimental investigation.Here,we report the observation of the modulation of moirépotential and intralayer excitons in the WS_(2)/WS_(2)homostructure.By accurately adjusting the torsion angle of the homobilayers,the depth of the moirépotential can be modulated.The confinement effect of the moirépotential on the intralayer excitons was further demonstrated by the changing of temperature and valley polarization.Furthermore,we show that a detection of atomic reconstructions by the low-frequency Raman mapping to map out inhomogeneities in moirélattices on a large scale,which endows the uniformity of interlayer coupling.Our results provide insights for an in-depth understanding of the behaviors of moiréexcitons in the twisted van der Waals homostructure,and promote the study of electrical engineering and topological photonics.
基金The study presented herein was generously supported by multiple funding agencies,including the National Natural Science Foundation of China(No.61775241)the Hunan Province Key Research and Development Project(No.2019GK2233)+9 种基金the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)the Youth Innovation Team(No.2019012)of CSU,the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the Postdoctoral Science Foundation of China(No.2022M713546)The authors also express their gratitude to the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)the Australian Research Council(ARC Discovery Project,DP180102976)for their support of ZWLCTW is grateful for support from the National Natural Science Foundation of China(No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)H.H.Z.acknowledges support from the Postdoctoral Science Foundation of China(No.2022M713546).
文摘Moirésuperlattices in van der Waals structures have emerged as a powerful platform for studying the novel quantum properties of two-dimensional materials.The periodic moirépatterns generated by these structures lead to the formation of flat mini-bands,which alter the electronic energy bands of the material.The resulting flat electronic bands can greatly enhance strong correlative interactions between electrons,leading to the emergence of exotic quantum phenomena,including moiréphonons and moiréexcitons.While extensive research has been conducted on the exotic quantum phenomena in twisted bilayers of transition metal dichalcogenides(TMDs),and the regulatory effect of stacked layers on moiréexcitons remains unexplored.In this study,we report the fabrication of a twisted WSe_(2)/WSe_(2)/WSe_(2) homotrilayer with two twist angles and investigate the influence of stacked layers on moiréexcitons.Our experiments reveal multiple moiréexciton splitting peaks in the twisted trilayer,with moirépotential depths of 78 and 112 meV in the bilayer and trilayer homostructures,respectively.We also observed the splitting of the moiréexcitons at 90 K,indicating the presence of a deeper moirépotential in the twisted trilayer.Moreover,we demonstrate that stacked layers can tune the moiréexcitons by manipulating temperature,laser power,and magnetic field.Our results provide a new physical model for studying moirésuperlattices and their quantum properties,which could potentially pave the way for the development of quantum optoelectronics.
基金The authors express their gratitude to various organizations for their support in this research,including the National Natural Science Foundation of China(Grant No.61775241)the Hunan province key research and development project(Grant No.2019GK2233)+8 种基金the Hunan Provincial Science Fund for Distinguished Young Scholars(Grant No.2020JJ2059)the Youth Innovation Team(Grant No.2019012)of CSU.Additionally,they acknowledge the Science and Technology Innovation Basic Research Project of Shenzhen(Grant No.JCYJ20190806144418859)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)the Key Program of Science and Technology Department of Hunan Province(2019XK2001,2020XK2001)The authors also thank the High-Performance Complex Manufacturing Key State Lab Project of Central South University(Grant No.ZZYJKT2020-12)for their support.Z.W.Lacknowledges the support from the Australian Research Council(ARC Discovery Project,DP180102976)C.T.W.is grateful for the support from the National Natural Science Foundation of China(Grant No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB33000000)H.H.Z.acknowledges the support from the Postdoctoral Science Foundation of China(2022M713546).Finally,the authors recognize the Beijing Super Cloud Computing Center(BSCC)for providing HPC resources,which have greatly contributed to the results reported in this paper.
文摘The stacking of twisted two-dimensional(2D)layered materials has led to the creation of moirésuperlattices,which have become a new platform for the study of quantum optics.The strong coupling of moirésuperlattices can result in flat minibands that boost electronic interactions and generate interesting strongly correlated states,including unconventional superconductivity,Mott insulating states,and moiréexcitons.However,the impact of adjusting and localizing moiréexcitons in Van der Waals heterostructures has yet to be explored experimentally.Here,we present experimental evidence of the localization-enhanced moiréexcitons in the twisted WSe_(2)/WS_(2)/WSe_(2)heterotrilayer with type-II band alignments.At low temperatures,we observed multiple excitons splitting in the twisted WSe_(2)/WS_(2)/WSe_(2)heterotrilayer,which is manifested as multiple sharp emission lines,in stark contrast to the moiréexcitonic behavior of the twisted WSe_(2)/WS_(2)heterobilayer(which has a linewidth 4 times wider).This is due to the enhancement of the two moirépotentials in the twisted heterotrilayer,enabling highly localized moiréexcitons at the interface.The confinement effect of moirépotential on moiréexcitons is further demonstrated by changes in temperature,laser power,and valley polarization.Our findings offer a new approach for localizing moiréexcitons in twist-angle heterostructures,which has the potential for the development of coherent quantum light emitters.
基金The authors would like to acknowledge the National Natural Science Foundation of China(Nos.61775241,62090035,and U19A2090)the Hunan Province Key Research and Development Project(No.2019GK2233)+8 种基金the Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the Youth Innovation Team of CSU(No.2019012)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the Postdoctoral Science Foundation of China(No.2022M713546)The authors would also like to express their gratitude to the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)the Australian Research Council(ARC)Discovery Project(No.DP180102976)for their support of Z.W.L.C.T.W.acknowledges support from the National Natural Science Foundation of China(No.11974387)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB33000000)H.H.Z.is grateful for the support from the Postdoctoral Science Foundation of China(No.2022M713546).
文摘Exploiting the valley degrees of freedom as information carriers provides new opportunities for the development of valleytronics.Monolayer transition metal dichalcogenides(TMDs)with broken space-inversion symmetry exhibit emerging valley pseudospins,making them ideal platforms for studying valley electronics.However,intervalley scattering of different energy valleys limits the achievable degree of valley polarization.Here,we constructed WSe_(2)/yttrium iron garnet(YIG)heterostructures and demonstrated that the interfacial magnetic exchange effect on the YIG magnetic substrate can enhance valley polarization by up to 63%,significantly higher than that of a monolayer WSe_(2)on SiO_(2)/Si(11%).Additionally,multiple sharp exciton peaks appear in the WSe_(2)/YIG heterostructures due to the strong magnetic proximity effect at the magnetic-substrate interface that enhances exciton emission efficiency.Moreover,under the effect of external magnetic field,the magnetic direction of the magnetic substrate enhances valley polarization,further demonstrating that the magnetic proximity effect regulates valley polarization.Our results provide a new way to regulate valley polarization and demonstrate the promising application of magnetic heterojunctions in magneto-optoelectronics.
基金the Innovation-driven Project(No.2017CX019)Youth Innovation Team(No.2019012)of CSU,Hunan Key Research and Development Project(No.2019GK233)partially by the National Natural Science Foundation of China(No.61775241).
文摘Valley degree of freedom in the first Brillouin zone of Bloch electrons offers an innovative approach to information storage and quantum computation.Broken inversion symmetry together with the presence of time-reversal symmetry endows Bloch electrons non-zero Berry curvature and orbital magnetic moment,which contribute to the valley Hall effect and optical selection rules in valleytronics.Furthermore,the emerging transition metal dichalcogenides(TMDs)materials naturally become the ideal candidates for valleytronics research attributable to their novel structural,photonic and electronic properties,especially the direct bandgap and broken inversion symmetry in the monolayer.However,the mechanism of inter-valley relaxation remains ambiguous and the complicated manipulation of valley predominantly incumbers the realization of valleytronic devices.In this review,we systematically demonstrate the fundamental properties and tuning strategies(optical,electrical,magnetic and mechanical tuning)of valley degree of freedom,summarize the recent progress of TMD-based valleytronic devices.We also highlight the conclusion of present challenges as well as the perspective on the further investigations in valleytronics.
基金This work was supported by the National Natural Science Foundation of China(No.61775241)Youth Innovation Team(No.2019012)+3 种基金of CSU,Hunan province key research and development project(No.2019GK2233)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20180307151237242)the Project of State Key Laboratory of High-Performance Complex Manufacturing,Central South University(No.ZZYJKT2020-12)Z.W.L.acknowledges the funding support from the Australian Research Council(ARC Discovery Projects,DP180102976).
文摘The extraordinary optical and electronic properties of anisotropic two-dimensional materials,such as black phosphorus,ReS2,and GeSe,enable them a promising component of polarization-sensitive photodetectors.However,these applications are significantly limited by the challenges of air-stability,response time,and linearly dichroic ratio.Interestingly,palladium diselenide(PdSe2)with high air stability is an emerging material that has robust in-plane anisotropy induced by its asymmetric pentagonal lattice structure.We have successfully prepared a few-layer PdSe2 using micromechanical exfoliation,and here we demonstrate the strong linear dichroism behavior of PdSe2 by polarization-resolved absorption spectra measurements.Such unique linear dichroism,endows the PdSe2 photodetector powerful ability to detect polarized light.The photodetector based on 5L PdSe2,as tested with polarization-dependent photocurrent mapping,exhibited competitive capability to detect polarized light,achieving a significant photocurrent on/off ratio(>10^2),the quite fast response time(<11 ms)and robust linearly dichroic ratios(/max//min≈1.9 at 532 nm).These results are essential advance in the development of polarization-sensitive photodetector,a crucial step towards opening up a new avenue for the application of 2D optoelectronic devices.
基金the National Natural Science Foundation of China(No.61775241)Hunan province key research and development project(No.2019GK2233)+5 种基金the Hunan Science Fund for Distinguished Young Scholar(No.2020JJ2059)Youth Innovation Team of Central South University(No.2019012)Hunan Province Graduate Research and Innovation Project(No.CX20190177)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20180307151237242)Also,Y.P.L.acknowledges the support provided by the Central South University of the State Key Laboratory of High-Performance Complex Manufacturing Project(No.ZZYJKT2020-12)Z.W.L.thanks the funding support from the Australian Research Council(ARC Discovery Projects)(Nos.DP210103539 and DP180102976).
文摘Interlayer excitons(IXS)are electron–hole pairs bound in the spatial separation layer by the Coulomb effect,and their lifetime is several orders of magnitude longer than that of direct excitons,providing an essential platform for long-lived exciton devices.The recent emergence of the van der Waals heterostructure(HS),which combines two layers of different transitional metal dichalcogenides(TMDs),has created new opportunities for IX research.Herein,we demonstrate the observation of double indirect interlayer excitons in the MoSe_(2)/WSe_(2)HS using photoluminescence(PL)spectroscopy.The intensities of the two peaks are essentially the same,and the energy difference is 22 meV,which is perfectly in line with the calculation result of density functional theory.Furthermore,the experience of variable excitation power also proves that the splitting of the IXs originates from the conduction band spin-splitting of MoSe_(2).The observation results provide a promising platform for further exploring the new physical properties and optoelectronic phenomena of TMD HS.
基金the National Natural Science Foundation of China(No.61775241)the Hunan Science Fund for Distinguished Young Scholar(No.2020JJ2059)+5 种基金Hunan Province Key Research and Development Project(No.2019GK2233)Youth Innovation Team(No.2019012)of CSUHunan Province Graduate Research and Innovation Project(No.CX20190177)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20180307151237242)Also,Y.P.L.acknowledges the supported by the Project of State Key Laboratory of High-Performance Complex Manufacturing,Central South University(No.ZZYJKT2020-12)Z.W.L.thanks the funding support from the Australian Research Council(ARC Discovery Projects,Nos.DP210103539,DP180102976,and DP130104231).
文摘Van der Waals’two-dimensional(2D)material heterostructure engineering offers an effective strategy for the design of multifunctional and high-performance optoelectronic devices.However,2D heterostructure photodetectors with a photoconductive effect tend to suffer from high driving source-drain voltages and significant dark noise currents.Herein,a self-powered photodetector with high performance was fabricated based on vertically stacked graphene/MoSe_(2)/PdSe_(2)/graphene heterojunctions through a dry transfer method.The fabricated device displays current rectification characteristics in darkness(on/off ratio>10^(3))and superior photovoltaic behaviors under illumination.In addition,benefitting from the strong built-in field,the Gr/PdSe_(2)/MoSe_(2)/Gr heterojunction photodetector is able to respond to a broad spectrum from visible to near-infrared(NIR)with a remarkable responsivity of 651 mA·W^(−1),a high specific detectivity of 5.29×10^(11) Jones and a fast response speed of 41.7/62.5μs.Moreover,an enhanced responsivity of 1.16 A·W^(−1) has been obtained by a reverse voltage(−1 V)and further evaluation on image recognition has also demonstrated the great application potential of the Gr/MoSe_(2)/PdSe_(2)/Gr heterojunction photodetector.The findings are expected to bring new opportunities for the development of highly sensitive,high-speed and energy-efficient photodetectors for comprehensive applications.
基金the financial supports by Australian Research Council Discovery Projects (DP150103842)Discovery Earlier Career Research Project (DE190101618)+1 种基金the Faculty's MCR Scheme, Energy and Materials Clusters at the University of Sydneythe support by the National Natural Science Foundation of China (21522310, 21473244 and 21210005)
文摘Pentacoordinated Al(Al~Ⅴ)species in silica-alumina are promising to promote the formation of acid sites or act as surface defects for tailoring single-atom catalysts.However,pentahedral coordination(Al~Ⅴ)is rarely observed in conventionally prepared silica-alumina.Here,we show that high population and dispersion of Al~Ⅴ species on the surface of amorphous silica-alumina(ASA)can be achieved by means of flame spray pyrolysis.High resolution TEM/EDX,high magnetic-field NMR and DFT calculations are employed to characterize the structure of as-prepared ASAs.Solid-state ^(27)Al multi-quantum MAS NMR experiments show that most of the Al~Ⅴspecies are formed independently from the alumina phase and are accessible for guest molecules on the surface.Upon water adsorption,these Al~Ⅴ species are transformed to Al~Ⅵ species,structurally similar to surface Al~Ⅳ species,as confirmed by DFT calculations.The outstanding catalytic activity of as-synthesized ASA is demonstrated using the in situ H/D exchange reaction with deuterated benzene as an example.The Al~Ⅴ-rich ASA provides a much lower activation energy(~30 kJ/mol)than that reported for zeolite H-ZSM-5(~60 kJ/mol).The superior catalytic performance is attributed to the high Al~Ⅴcontent promoting the surface active sites in ASA.The knowledge gained on the synthesis of Al~Ⅴ-rich ASAs and the nature of aluminum coordination in these materials could pave the way to more efficient silica-alumina based catalysts.
基金support from the Naional Natural Science Foundation of China(Grant No.61775241)Hunan province key research and development project(Grant No.2019GK2233)+5 种基金Hunan Provincial Science Fund for Distinguished Young Scholars(Grant No.2020JJ2059)the Youth Innovaticn Team(Grant No.2019012)of CSU,the Science and Technolgy Innovaton Basic Research Project of Shenzhen(Grant No.JCY120190806144418859)the National Natural Science Foundation of China (Nos.62090035,U19A2090)the Key Program of Science and Technology Department of Hunan Province(2019XK2001,2020XK2001)support of the High-Performance Complex Manufacturing Key State Lab Project,Central South University(Grant No.ZZYJKT2020-12)ZWL.thanks the support from the Australian Research Council(ARC Discovery Project,DP180102976).
文摘Recent advances in twisted van der Waals heterostructure superlattices have emerged as a powerful and attractive platform for exploring novel condensed matter physics due to the interplay between the moirépotential and Coulomb interactions.The moirésuperlattices act as a periodic confinement potential in space to capture interlayer excitons(IXs),resulting in moiréexciton arrays,which provide opportunities for quantum emitters and many-body physics.The observation of moiréIXs in twisted transition-metal dichalcogenide(TMD)heterostructures has recently been widely reported.However,the capture and study of the moiréintralayer excitons based on TMD twisted homobilayer(T-HB)remain elusive.Here,we report the observation of moiréintralayer excitons in a WSe_(2)/WSe_(2) T-HB with a small twist angle by measuring PL spectrum.The multiple split peaks with an energy range of 1.55-1.73 eV are different from that of the monolayer WSe_(2) exciton peaks.The split peaks were caused by the trapping of intralayer excitons via the moirépotential.The confinement effect of the moirépotential on the moiréintralayer excitons was further demonstrated by the changing of temperature,laser power,and valley polarization.Our findings provide a new avenue for exploring new correlated quantum phenomena and their applications.
基金support from the National Natural Science Foundation of China(Nos.61775241,62090035,and U19A2090)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20180307151237242)+5 种基金Hunan Province Key Research and Development Project(No.2019GK2233)Hunan Provincial Science Fund for Distinguished Young Scholars(No,2020JJ2059)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the Youth Innovation Team(No,2019012)of Central South UniversityThe authors are also thankful for the support of the High Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)Z.W.L.thanks the support from the Australian Research Council(ARC Discovery Project,No.DP180102976).
文摘Van der Waals heterostructures have recently emerged,in which two distinct transitional metal dichalcogenide(TMD)monolayers are stacked vertically to generate interlayer excitons(IXs),offing new opportunites for the design of optoelectronic devices.However,the bilayer heterostructure with type-II band alignment can only produce low quantum yield.Here,we present the observation of interlayer neutral excitons and trions in the MoSe_(2)/MoS_(2)/MoSe_(2)trilayer heterostructure(Tri-HS).In comparison to the 8 K bilayer heterostructure,the addition of a MoSe_(2)layer to the Tri-HS can significantly increase the quantum yield of IXs.It is believed the two symmetrical type-II band alignments formed in the Tri-HS could effectively promote the IX radiation recombination.By analyzing the photoluminescence(PL)spectrum of the IXs at cryogenic temperature and the power dependence,the existence of the interlayer trions was confirmed.Our results provide a promising platform for the development of more efficient optoelectronic devices and the investigation of new physical properties of TMDs.
基金the support of the Hunan Province’s Key Research and Development Project(No.2019GK2233)the National Natural Science Foundation of China(No.61775241)+4 种基金the Hunan Science Fund for Distinguished Young Scholar(No.2020JJ2059)Youth Innovation Team(No.2019012)of CSU,Hunan Province Graduate Research and Innovation Project(No.CX20190177)the Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the support from the Central South University of the State Key Laboratory of High-Performance Complex Manufacturing Project(No.ZZYJKT2020-12).support from the Australian Research Council(ARC Discovery Projects,Nos.DP210103539,DP180102976,and DP130104231).
文摘Vertically stacked transition metal dichalcogenide(TMD)heterostructures provide an opportunity to explore optoelectronic properties within the two-dimensional limit.In such structures,spatially indirect interlayer excitons(IXs)can be generated in adjacent layers because of strong Coulomb interactions.However,due to the complexity of the multilayered heterostructure(HS),the capture and study of the IXs in trilayer type-Ⅱ HSs have so far remained elusive.Here,we present the observation of the IXs in trilayer type-Ⅱ staggered band alignment of MoS_(2)/MoSe_(2)/WSe_(2) van der Waals(vdW)HSs by photoluminescence(PL)spectroscopy.The central energy of IX is 1.33 eV,and the energy difference between the extracted double peaks is 23 meV.We confirmed the origin of IX through PL properties and calculations by the density functional theory,we also studied the dependence of the IX emission peak on laser power and temperature.Furthermore,the polarization-resolved PL spectra of HS were also investigated,and the maximum polarizability of the emission peak of WSe_(2) reached 11.40%at 6 K.Our findings offer opportunities for the study of new physical properties of excitons in TMD HSs and therefore are valuable for exploring the potential applications of TMDs in optoelectronic devices.
基金the National Natural Science Foundation of China(No.61775241)Hunan province key research and development project(No.2019GK2233)+6 种基金Hunan Provincial Science Fund for Distinguished Young Scholars(No.2020JJ2059)the Youth Innovation Team(No.2019012)of CSUthe Science and Technology Innovation Basic Research Project of Shenzhen(No.JCYJ20190806144418859)the National Natural Science Foundation of China(Nos.62090035 and U19A2090)the Key Program of Science and Technology Department of Hunan Province(Nos.2019XK2001 and 2020XK2001)the support of the High-Performance Complex Manufacturing Key State Lab Project,Central South University(No.ZZYJKT2020-12)Z.W.L.thanks the support from the Australian Research Council(ARC Discovery Project,DP180102976).
文摘Moirésuperlattices are formed by a lattice mismatch or twist angle in two-dimensional materials,which can generate periodical moirépotentials leading to strong changes in the band structure,resulting in new quantum phenomena.However,the experimental engineering of in-situ deformation of moiréheterostructures remains deficient.Here,we demonstrate a dynamic local deformation of the twisted heterostructures using a diamond anvil cell(DAC),enabling in-situ dynamic modulation of moirépotential in twisted WS_(2)–WSe_(2)heterostructures at room temperature.Deformation of the twisted heterostructure increases the moirépotential,causing a red shift of the moiréexciton resonance,and observed the red shift of the intralayer exciton resonance up to 16.3 meV(less than 1.1 GPa).The blue shift of the interlayer excitons of twisted WS_(2)–WSe_(2)heterostructures shows an evident transition of the pressure sensitive exciton,induced by the dominant effect of modifying the band structure on optical properties.Combined with the spectral changes of pressurized Raman,which further demonstrated that the DAC can efficiently regulate the interlayer coupling.Our results offer an effective strategy for in-situ dynamic modulation of moirépotential,providing a promising platform for the development of novel quantum devices.