Ultralong phosphorescent materials have numerous applications across biological imaging, lightemitting devices, X-ray detection and anti-counterfeiting. Triplet-state molecular phosphorescence typically accompanies th...Ultralong phosphorescent materials have numerous applications across biological imaging, lightemitting devices, X-ray detection and anti-counterfeiting. Triplet-state molecular phosphorescence typically accompanies the singlet-state fluorescence during photoluminescence, and it is still difficult to achieve direct triplet photoemission as ultralong room temperature phosphorescence(RTP). Here, we have designed Zn-IMDC(IMDC, 4,5-imidazoledicarboxylic acid) and Cd-IMDC, two-dimensional(2D)hydrogen-bond organized metal–organic crystalline microsheets that exhibit rarely direct ultralong RTP upon UV excitation, benefiting from the appropriate heavy-atom effect and multiple triplet energy levels. The excitation-dependent and thermally stimulated ultralong phosphorescence endow the metal–organic systems great opportunities for information safety application and temperature-gated afterglow emission. The well-defined 2D microsheets present color-tunable and anisotropic optical waveguides under different excitation and temperature conditions, providing an effective way to obtain intelligent RTP-based photonic systems at the micro-and nano-scales.展开更多
A hexaazatriphenylene（HAT） derivative that bears two n-octyl chains was designed and synthesized.Its photophysical and electrochemical properties have been investigated.SEM study revealed that it could self-assemble...A hexaazatriphenylene（HAT） derivative that bears two n-octyl chains was designed and synthesized.Its photophysical and electrochemical properties have been investigated.SEM study revealed that it could self-assemble into well-ordered 1D nanoribbons or 2D microsheets,which depends on the polarity of the solvents used.展开更多
Lithium-sulfur(Li-S)batteries are receiving increasing attention as one of the potential next-generation batteries,owing to their high energy densities and low cost.However,practical Li-S batteries with high energy de...Lithium-sulfur(Li-S)batteries are receiving increasing attention as one of the potential next-generation batteries,owing to their high energy densities and low cost.However,practical Li-S batteries with high energy densities are extremely hindered by the sulfur loss,low Coulombic efficiency,and short cycling life originating from the polysulfide(LiPS)shuttle.In this study,two-dimensional(2D)ZnCo_(2)O_(4) microsheets fabricated by a facile hydrothermal process are employed to modify the separator,for improving the electrochemical performances of Li-S cells.The resulting 2D Zn Co_(2)O_(4)-coated separator features a coating thickness of approximately 10 lm,high ionic conductivity of 1.8 m S/cm,and low mass loading of 0.2 mg/cm^(2).This 2D ZnCo_(2)O_(4)-coated separator effectively inhibits Li PS shuttle by a strong chemical interaction with Li PS as well as promotes the redox kinetics by Zn CO2O4-coated layers,as determined by X-ray photoelectron spectroscopy analysis,self-discharge,time-dependent permeation test,Li symmetric cell test,and Li2S nucleation analyses.Consequently,the Li-S batteries based on the 2D Zn Co_(2)O_(4)-coated separator exhibit a high initial discharge capacity of 1292.2 m Ah/g at 0.1 C.Moreover,they exhibit excellent long cycle stability at 1 and 2 C with capacity retention of 84%and 86%even after800 cycles,corresponding to a capacity fading rate of 0.020%and 0.016%per cycle,respectively.Effectively,these Li-S cells with a high sulfur loading at 5.3 mg/cm^(2) and low electrolyte concentration of 9 l L/mg deliver a high discharge capacity of 4.99 m Ah/cm^(2) after 200 cycles at 0.1 C.展开更多
The effects of different parameters on the nonlinear dynamic characteristics of macrofiber composite(MFC)microsheet with graphene(GP)skin under non-uniform thermal field are investigated.Firstly,the physical parameter...The effects of different parameters on the nonlinear dynamic characteristics of macrofiber composite(MFC)microsheet with graphene(GP)skin under non-uniform thermal field are investigated.Firstly,the physical parameters of the MFC–GP structure are calculated by the mixing rule,and the constitutive equations of the structure are set up by employing the Eringen theory.The nonlinear dynamic equations of the microsheet are obtained by using Hamilton’s principle.Then,the heat conduction equations of the microsheet are considered,adopting Green and Naghdi’s generalized thermoelasticity theory.According to the Galerkin weighted residual method,the thermoelasticity coupling equations of the structure are obtained.Meanwhile,the influence of the positive piezoelectric effect of GP and MFC on the vibration response of the structure is also investigated.The nonlinear dynamic governing equations including displacement,coupled thermoelasticity,and electricity field are discretized by the Galerkin method.The effects of non-local parameter,volume fraction of GP,and thermal and electricity coupling coefficients on structural dynamic behavior are discussed in the numerical simulation.展开更多
Owing to their strong nonlinearity,cadmium sulfide(CdS)nanostructures are promising platforms for investigating the fundamental physics of light-matter interactions.However,observing the strong exciton-photon interact...Owing to their strong nonlinearity,cadmium sulfide(CdS)nanostructures are promising platforms for investigating the fundamental physics of light-matter interactions.However,observing the strong exciton-photon interactions in CdS microstructures at room temperature continues to present significant challenges,primarily because of the limited exciton binding energy.This study reports the direct observation of the interaction between excitons and microcavity photons in Sn-doped CdS microsheets without extreme fabrication conditions.Using angle-resolved photoluminescence(ARPL)spectroscopy,Rabi splitting of polaritons up to 163 meV was obtained at room temperature.Additionally,the temporal lasing dynamics of the Sn-doped CdS microsheets were investigated using a streak camera system.Most importantly,exciton-polariton condensation and coherent exciton-polariton lasing in the Sn-doped CdS microsheet was observed at room temperature.These results advance the fundamental understanding of exciton-polaritons in Sn-doped CdS microsheets and their applications in miniaturized microlaser devices.展开更多
Graphene is a promising electromagnetic wave absorption(EMWA)material because of its structural designability,controllable electromagnetic properties,and excellent stability.However,the impedance mismatch caused by hi...Graphene is a promising electromagnetic wave absorption(EMWA)material because of its structural designability,controllable electromagnetic properties,and excellent stability.However,the impedance mismatch caused by high conductivity and dielectric properties has seriously hindered the application of graphene in the EMWA field.In this work,based on the dielectric dispersion behavior of ideal broadband absorption as a guide,a Fe microsheet/reduced graphene oxide(Fe/RGO)composite was prepared by simple hydrothermal and thermal reduction methods.The permittivity of RGO is optimized by adjusting the content of anisotropic Fe microsheets,and a balance between attenuation ability and impedance matching is achieved.Theoretical calculations and off-axis electron holography results reveal that the abundant polar sites and heterogeneous interfaces of Fe and RGO enhance the dipole and interface polarizations.The threedimensional(3D)conductive network structure contributes to multiple reflections of incident electromagnetic waves and conduction loss.The natural and exchange resonances and eddy current loss caused by anisotropic Fe microsheets further increase magnetic loss.Based on the dielectric-magnetic loss mechanism and good impedance matching,Fe/RGO achieves a minimum reflection loss(RL_(min))of−67.95 dB at 8.48 GHz and a maximum effective absorption bandwidth(EAB_(max))of 6.91 GHz(11.09–18 GHz)with a low filling content of 10 wt%.In addition,Fe/RGO has excellent radar stealth performance,with a radar cross section(RCS)of−31.21 dBm^(2) at 0°.Therefore,the proposed strategy and theoretical analysis provide a reference for the microstructure design,composition,and mechanism analysis of EMWA materials.展开更多
The objective of this work was to fabricate a rigid,resorbable and osteoconductive scaffold by mimicking the hierarchical structure of the cortical bone.Aligned peptide-functionalize nanofiber microsheets were generat...The objective of this work was to fabricate a rigid,resorbable and osteoconductive scaffold by mimicking the hierarchical structure of the cortical bone.Aligned peptide-functionalize nanofiber microsheets were generated with calcium phosphate(CaP)content similar to that of the natural cortical bone.Next,the CaP-rich fibrous microsheets were wrapped around a microneedle to form a laminated microtube mimicking the structure of an osteon.Then,a set of the osteon-mimetic microtubes were assembled around a solid rod and the assembly was annealed to fuse the microtubes and form a shell.Next,an array of circular microholes were drilled on the outer surface of the shell to generate a cortical bone-like scaffold with an interconnected network of Haversian-and Volkmann-like microcanals.The CaP content,porosity and density of the bone-mimetic microsheets were 240 wt%,8%and 1.9 g/ml,respectively,which were close to that of natural cortical bone.The interconnected network of microcanals in the fused microtubes increased permeability of a model protein in the scaffold.The cortical scaffold induced osteogenesis and vasculogenesis in the absence of bone morphogenetic proteins upon seeding with human mesenchymal stem cells and endothelial colony-forming cells.The localized and timed-release of morphogenetic factors significantly increased the extent of osteogenic and vasculogenic differentiation of human mesenchymal stem cells and endothelial colony-forming cells in the cortical scaffold.The cortical bonemimetic nature of the cellular construct provided balanced rigidity,resorption rate,osteoconductivity and nutrient diffusivity to support vascularization and osteogenesis.展开更多
基金supported by the Beijing Municipal Natural Science Foundation(JQ20003)the National Natural Science Foundation of China(21771021,21822501,and 22061130206)+3 种基金the Fok Ying-Tong Education Foundation(171008)the Measurements Fund of Beijing Normal Universitythe State Key Laboratory of Heavy Oil Processing。
文摘Ultralong phosphorescent materials have numerous applications across biological imaging, lightemitting devices, X-ray detection and anti-counterfeiting. Triplet-state molecular phosphorescence typically accompanies the singlet-state fluorescence during photoluminescence, and it is still difficult to achieve direct triplet photoemission as ultralong room temperature phosphorescence(RTP). Here, we have designed Zn-IMDC(IMDC, 4,5-imidazoledicarboxylic acid) and Cd-IMDC, two-dimensional(2D)hydrogen-bond organized metal–organic crystalline microsheets that exhibit rarely direct ultralong RTP upon UV excitation, benefiting from the appropriate heavy-atom effect and multiple triplet energy levels. The excitation-dependent and thermally stimulated ultralong phosphorescence endow the metal–organic systems great opportunities for information safety application and temperature-gated afterglow emission. The well-defined 2D microsheets present color-tunable and anisotropic optical waveguides under different excitation and temperature conditions, providing an effective way to obtain intelligent RTP-based photonic systems at the micro-and nano-scales.
文摘A hexaazatriphenylene（HAT） derivative that bears two n-octyl chains was designed and synthesized.Its photophysical and electrochemical properties have been investigated.SEM study revealed that it could self-assemble into well-ordered 1D nanoribbons or 2D microsheets,which depends on the polarity of the solvents used.
基金supported by a grant from R&D Program of the Korea Railroad Research Institute,Republic of Korea。
文摘Lithium-sulfur(Li-S)batteries are receiving increasing attention as one of the potential next-generation batteries,owing to their high energy densities and low cost.However,practical Li-S batteries with high energy densities are extremely hindered by the sulfur loss,low Coulombic efficiency,and short cycling life originating from the polysulfide(LiPS)shuttle.In this study,two-dimensional(2D)ZnCo_(2)O_(4) microsheets fabricated by a facile hydrothermal process are employed to modify the separator,for improving the electrochemical performances of Li-S cells.The resulting 2D Zn Co_(2)O_(4)-coated separator features a coating thickness of approximately 10 lm,high ionic conductivity of 1.8 m S/cm,and low mass loading of 0.2 mg/cm^(2).This 2D ZnCo_(2)O_(4)-coated separator effectively inhibits Li PS shuttle by a strong chemical interaction with Li PS as well as promotes the redox kinetics by Zn CO2O4-coated layers,as determined by X-ray photoelectron spectroscopy analysis,self-discharge,time-dependent permeation test,Li symmetric cell test,and Li2S nucleation analyses.Consequently,the Li-S batteries based on the 2D Zn Co_(2)O_(4)-coated separator exhibit a high initial discharge capacity of 1292.2 m Ah/g at 0.1 C.Moreover,they exhibit excellent long cycle stability at 1 and 2 C with capacity retention of 84%and 86%even after800 cycles,corresponding to a capacity fading rate of 0.020%and 0.016%per cycle,respectively.Effectively,these Li-S cells with a high sulfur loading at 5.3 mg/cm^(2) and low electrolyte concentration of 9 l L/mg deliver a high discharge capacity of 4.99 m Ah/cm^(2) after 200 cycles at 0.1 C.
基金The authors gratefully acknowledge the support of the National Natural Science Foundation of China(NNSFC)through Grant Nos.11772010 and 11832002the Funding Project for High-Level Teachers’Team Construction in Beijing Municipal Colleges and Universities.
文摘The effects of different parameters on the nonlinear dynamic characteristics of macrofiber composite(MFC)microsheet with graphene(GP)skin under non-uniform thermal field are investigated.Firstly,the physical parameters of the MFC–GP structure are calculated by the mixing rule,and the constitutive equations of the structure are set up by employing the Eringen theory.The nonlinear dynamic equations of the microsheet are obtained by using Hamilton’s principle.Then,the heat conduction equations of the microsheet are considered,adopting Green and Naghdi’s generalized thermoelasticity theory.According to the Galerkin weighted residual method,the thermoelasticity coupling equations of the structure are obtained.Meanwhile,the influence of the positive piezoelectric effect of GP and MFC on the vibration response of the structure is also investigated.The nonlinear dynamic governing equations including displacement,coupled thermoelasticity,and electricity field are discretized by the Galerkin method.The effects of non-local parameter,volume fraction of GP,and thermal and electricity coupling coefficients on structural dynamic behavior are discussed in the numerical simulation.
基金supported by the Postdoctoral Fellowship Program of CPSF(No.GZC20241576)the Shanxi Province Basic Research Program(No.202403021212341)the Open Project Program of Shanxi Key Laboratory of Advanced Semiconductor Optoelectronic Devices and Integrated Systems(No.2024SZKF03).
文摘Owing to their strong nonlinearity,cadmium sulfide(CdS)nanostructures are promising platforms for investigating the fundamental physics of light-matter interactions.However,observing the strong exciton-photon interactions in CdS microstructures at room temperature continues to present significant challenges,primarily because of the limited exciton binding energy.This study reports the direct observation of the interaction between excitons and microcavity photons in Sn-doped CdS microsheets without extreme fabrication conditions.Using angle-resolved photoluminescence(ARPL)spectroscopy,Rabi splitting of polaritons up to 163 meV was obtained at room temperature.Additionally,the temporal lasing dynamics of the Sn-doped CdS microsheets were investigated using a streak camera system.Most importantly,exciton-polariton condensation and coherent exciton-polariton lasing in the Sn-doped CdS microsheet was observed at room temperature.These results advance the fundamental understanding of exciton-polaritons in Sn-doped CdS microsheets and their applications in miniaturized microlaser devices.
基金supported by the National Natural Science Foundation of China(Nos.52432002,52372041,and 52302087)the Heilongjiang Touyan Team Program,the Fundamental Research Funds for the Central Universities(No.HIT.OCEF.2021003)the Shanghai Aerospace Science and Technology Innovation Fund(No.SAST2022-60).
文摘Graphene is a promising electromagnetic wave absorption(EMWA)material because of its structural designability,controllable electromagnetic properties,and excellent stability.However,the impedance mismatch caused by high conductivity and dielectric properties has seriously hindered the application of graphene in the EMWA field.In this work,based on the dielectric dispersion behavior of ideal broadband absorption as a guide,a Fe microsheet/reduced graphene oxide(Fe/RGO)composite was prepared by simple hydrothermal and thermal reduction methods.The permittivity of RGO is optimized by adjusting the content of anisotropic Fe microsheets,and a balance between attenuation ability and impedance matching is achieved.Theoretical calculations and off-axis electron holography results reveal that the abundant polar sites and heterogeneous interfaces of Fe and RGO enhance the dipole and interface polarizations.The threedimensional(3D)conductive network structure contributes to multiple reflections of incident electromagnetic waves and conduction loss.The natural and exchange resonances and eddy current loss caused by anisotropic Fe microsheets further increase magnetic loss.Based on the dielectric-magnetic loss mechanism and good impedance matching,Fe/RGO achieves a minimum reflection loss(RL_(min))of−67.95 dB at 8.48 GHz and a maximum effective absorption bandwidth(EAB_(max))of 6.91 GHz(11.09–18 GHz)with a low filling content of 10 wt%.In addition,Fe/RGO has excellent radar stealth performance,with a radar cross section(RCS)of−31.21 dBm^(2) at 0°.Therefore,the proposed strategy and theoretical analysis provide a reference for the microstructure design,composition,and mechanism analysis of EMWA materials.
基金supported by research grants to E.Jabbari from the National Science Foundation under Award Numbers CBET1403545 and IIP150024 and the National Institute of Arthritis and Musculoskeletal and Skin Diseases of the National Institutes of Health under Award Number AR063745.
文摘The objective of this work was to fabricate a rigid,resorbable and osteoconductive scaffold by mimicking the hierarchical structure of the cortical bone.Aligned peptide-functionalize nanofiber microsheets were generated with calcium phosphate(CaP)content similar to that of the natural cortical bone.Next,the CaP-rich fibrous microsheets were wrapped around a microneedle to form a laminated microtube mimicking the structure of an osteon.Then,a set of the osteon-mimetic microtubes were assembled around a solid rod and the assembly was annealed to fuse the microtubes and form a shell.Next,an array of circular microholes were drilled on the outer surface of the shell to generate a cortical bone-like scaffold with an interconnected network of Haversian-and Volkmann-like microcanals.The CaP content,porosity and density of the bone-mimetic microsheets were 240 wt%,8%and 1.9 g/ml,respectively,which were close to that of natural cortical bone.The interconnected network of microcanals in the fused microtubes increased permeability of a model protein in the scaffold.The cortical scaffold induced osteogenesis and vasculogenesis in the absence of bone morphogenetic proteins upon seeding with human mesenchymal stem cells and endothelial colony-forming cells.The localized and timed-release of morphogenetic factors significantly increased the extent of osteogenic and vasculogenic differentiation of human mesenchymal stem cells and endothelial colony-forming cells in the cortical scaffold.The cortical bonemimetic nature of the cellular construct provided balanced rigidity,resorption rate,osteoconductivity and nutrient diffusivity to support vascularization and osteogenesis.
