Slender chiral filaments are ubiquitous in both artificial and biological materials.Due to their chiral microstructures,chiral filaments usually exhibit favorable properties such as superior elasticity and unusual str...Slender chiral filaments are ubiquitous in both artificial and biological materials.Due to their chiral microstructures,chiral filaments usually exhibit favorable properties such as superior elasticity and unusual stretch-twist coupling deformation.However,how these chiral microstructures affect the elastic behavior of filaments remains unclear.In this paper,a refined Cosserat rod model with misfit or mismatching of chirality induced by inhomogeneous arrangement of chiral microstructures incorporated is developed.Using the refined rod model,the force-displacement relationships and variation of structural chirality during the tensile processes of two typical helical structures,i.e.,single-strand helix and double-strand helix,are investigated.The results show that the misfit of chirality can lead to a bend-twist deformation with a high coupling degree,which makes the rod much“soft”when stretched.The chiral filaments undergo an unusual twist when stretched,corresponding to an obviously nonlinear variation of structural chirality.The work suggests that the misfit of chirality can be used to tune the elastic behavior of chiral filaments,which is helpful in guiding the design of flexible actuators and soft devices.展开更多
Chiral supramolecules prepared by the additive-driven self-assembly of block copolymers provide a facile method to construct helical nanostructures. In this study, we investigated the chiral transfer from chiral tarta...Chiral supramolecules prepared by the additive-driven self-assembly of block copolymers provide a facile method to construct helical nanostructures. In this study, we investigated the chiral transfer from chiral tartaric acid to poly（styrene）-b-poly（ethylene oxide） using small-angle X-ray scattering,transmission electron microscopy, circular dichroism, and vibrational circular dichroism. The results showed that the chirality was transferred to both the segments of block copolymer irrespective of the interaction with the chiral additives and formation of helical phase structure. However, the chirality transfer was carried out using different methods： for poly（ethylene oxide） segments, the chirality transfer was carried out via direct hydrogen bond formation; for polystyrene segments, the chirality transfer was carried out via the cooperative motion of block copolymers during the thermal annealing.展开更多
Chirality,a common phenomenon in nature,appears in structures ranging from galaxies and condensed matter to atomic nuclei.There is a persistent demand for new,high-precision methods to detect chiral structures,particu...Chirality,a common phenomenon in nature,appears in structures ranging from galaxies and condensed matter to atomic nuclei.There is a persistent demand for new,high-precision methods to detect chiral structures,particularly at the microscale.Here,we propose a novel method,vortex Mössbauer spectroscopy,for probing chiral structures.By leveraging the orbital angular momentum carried by vortex beams,this approach achieves high precision in detecting chiral structures at scales ranging from nanometers to hundreds of nanometers.Our simulation shows the ratio of characteristic lines in the Mössbauer spectra of ^(57)Fe under vortex beams exhibits differences of up to four orders of magnitude for atomic structures with different arrangements.Additionally,simulations reveal the response of ^(229m)Th chiral structures to vortex beams with opposite angular momenta differs by approximately 49-fold.These significant spectral variations indicate that this new vortex Mössbauer probe holds great potential for investigating the microscopic chiral structures and interactions of matter.展开更多
The construction of carbon nanocoil(CNC)-based chiral-dielectric-magnetic trinity composites is considered as a promising approach to achieve excellent low-frequency microwave absorption.However,it is still challengin...The construction of carbon nanocoil(CNC)-based chiral-dielectric-magnetic trinity composites is considered as a promising approach to achieve excellent low-frequency microwave absorption.However,it is still challenging to further enhance the low frequency microwave absorption and elucidate the related loss mechanisms.Herein,the chiral CNCs are first synthesized on a threedimensional(3D)carbon foam and then combined with the FeNi/NiFe_(2)O_(4) nanoparticles to form a novel chiral-dielectric-magnetic trinity foam.The 3D porous CNC-carbon foam network provides excellent impedance matching and strong conduction loss.The formation of the FeNi-carbon interfaces induces interfacial polarization loss,which is confirmed by the density functional theory calculations.Further permeability analysis and the micromagnetic simulation indicate that the nanoscale chiral magnetic heterostructures achieve magnetic pinning and coupling effects,which enhance the magnetic anisotropy and magnetic loss capability.Owing to the synergistic effect between dielectricity,chirality,and magnetism,the trinity composite foam exhibits excellent microwave absorption performance with an ultrabroad effective absorption bandwidth(EAB)of 14 GHz and a minimum reflection of loss less than-50 dB.More importantly,the C-band EAB of the foam is extended to 4 GHz,achieving the full C-band coverage.This study provides further guidelines for the microstructure design of the chiral-dielectric-magnetic trinity composites to achieve broadband microwave absorption.展开更多
Cuticles of some Chrysina scarabs are characterized by flat, graded, and twisted structures of nanosized chitin fibrils. As inferred from SEM images, each species has its own spatial period or pitch P which is depende...Cuticles of some Chrysina scarabs are characterized by flat, graded, and twisted structures of nanosized chitin fibrils. As inferred from SEM images, each species has its own spatial period or pitch P which is dependent on the depth z through the cuticle. From Berreman’s formalism, taking into account the corresponding P(z) dependence, we evaluate reflection spectra of C. aurigans and C. chrysargyrea scarabs. The spectra display the main spectral features observed in the measured ones when small sections of the cuticles are illuminated with non-polarized light, for wavelengths between 300 and 1100 nm. By considering these twisted structures as 1D photonic crystals, an approach is developed to show how the broad band characterizing the reflection spectra arises from a narrow intrinsic photonic band width, whose spectral position moves through visible and near infrared wavelengths. The role of the epicuticle that covers the twisted structures is analyzed in terms of a waxy layer acting as an anti-reflecting coating that also shows low levels of light scattering.展开更多
The crystalline structures and crystallization behaviors of iPP containing β nucleation agent TMB-5 （iPP/TMB-5） were investigated by synchrotron radiation wide angel X-ray diffraction （SR-WAXD）, differential scan...The crystalline structures and crystallization behaviors of iPP containing β nucleation agent TMB-5 （iPP/TMB-5） were investigated by synchrotron radiation wide angel X-ray diffraction （SR-WAXD）, differential scanning calorimeter （DSC） and polarized light microscope （PLM）. It was found that α-crystallization lagged behind β-crystallization at normal temperatures, but the discrepancy reduced with increasing temperature. TMB-5 could not induce β-iPP when the nucleation agent is wrapped up with α-crystal that crystallized at high temperatures. The polymorphic composition of iPP/TMB-5 was susceptible to the introductory moment of shear. New crystallization process of β-nucleated iPP was proposed to understand the experimental phenomena which could not be explained by those reported in the literature. It was supposed that polymer crystallization initiated from mesophase, and the formations of iPP crystals involved the organization of helical conformation ordering within rnesophase. It was proposed that the iPP melt contained mesophases with stereocomplex-type ordering of right-handed and left-handed helical chains which could be disturbed by shear or TMB-5, leading to different polymorphic structures.展开更多
Tracheal stents are an important form of treatment for benign or malignant central airway obstruction.However,the mechanical behavior of current tracheal stents is significantly different from that of the native trach...Tracheal stents are an important form of treatment for benign or malignant central airway obstruction.However,the mechanical behavior of current tracheal stents is significantly different from that of the native trachea,which leads to a variety of serious complications.In this study,inspired by the structure of the native trachea,a wavy non-uniform ligament chiral tracheal stent is proposed,in which J-shaped stress-strain behavior and negative Poisson's ratio response are achieved by replacing the tangential ligament of tetrachiral and anti-tetrachiral hybrid structure with a wavy non-uniform ligament.Through the combination of theoretical analysis,finite element analysis and experimental tests,a wide range of desired J-shaped stress-strain curves are explored to mimic the native porcine trachea by tailoring the stent geometry.Besides,the negative Poisson’s ratio and auxetic diameter curves versus axial strain of the stent are also studied in detail,thus contributing to the enhancement of cross-section ventilation and reducing the migration of the stent.This novel tracheal stent with a unique microstructure shows a potential to perfectly match the physiological activities of the native trachea and thereby reduce potential complications.展开更多
The structural, electronic, and magnetic properties of transition metal doped platinum clusters MPt6 （M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn） are systematically studied by using the relativistic all-electron de...The structural, electronic, and magnetic properties of transition metal doped platinum clusters MPt6 （M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn） are systematically studied by using the relativistic all-electron density functional theory with the generalized gradient approximation. Most of the doped clusters show larger binding energies than the pure Pt7 cluster, which indicates that the doping of the transition metal atom can stabilize the pure platinum cluster. The results of the highest occupied molecular orbital （HOMO） lowest unoccupied molecular orbital （LUMO） gaps suggest that the doped clusters can have higher chemical activities than the pure Pt7 cluster. The magnetism calculations demonstrate that the variation range of the magnetic moments of the MPt6 clusters is from 0 μB to 7 μB, revealing that the MPt6 clusters have potential utility in designing new spintronic nanomaterials with tunable magnetic properties.展开更多
A novel chiral copper（Ⅱ） complex with racemic 1,2-diaminocyclohexane and iodide,[Cu（Ⅱ）（1,2-diaminocyclohexane）_3]（I）_2·3H_2O（1） has been synthesized and structurally characterized by X-ray single-crys...A novel chiral copper（Ⅱ） complex with racemic 1,2-diaminocyclohexane and iodide,[Cu（Ⅱ）（1,2-diaminocyclohexane）_3]（I）_2·3H_2O（1） has been synthesized and structurally characterized by X-ray single-crystal diffraction,elemental analysis,infrared spectroscopy,Raman spectroscopy and thermogravimetric analysis. In complex 1,the CuⅡ ion was coordinated by six nitrogen atoms of three 1,2-diaminocyclohexane molecules. The structure of complex 1 can be described as a supramolecular 3D-like structure which was formed by intermolecular hydrogen-bonding interactions between mononuclear molecules,uncoordinated water molecules and two iodide anions. UV-vis absorption spectrum and surface photovoltage properties of complex 1 have also been studied.展开更多
The title compound 4-（7-methoxy-2,2-dimethyl-2,3-dihydrobenzofuran-5-yl）-N- （pyridin-2-yl） thiazol-2-amine was synthesized by reacting 2-bromo-1-（7-methoxy-2,2-dime- thyl-2,3-dihydrobenzofuran-5-yl）ethanone with...The title compound 4-（7-methoxy-2,2-dimethyl-2,3-dihydrobenzofuran-5-yl）-N- （pyridin-2-yl） thiazol-2-amine was synthesized by reacting 2-bromo-1-（7-methoxy-2,2-dime- thyl-2,3-dihydrobenzofuran-5-yl）ethanone with 1-（pyridine-2-yl）thiourea, and its crystal was determined by single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, chiral space group C2 with a = 18.1328（14）, b = 5.5969（5）, c = 19.2195（15） A, β= 115.5420（10）°, V= 1759.9（2）A3, Z = 4, F（000） = 744, C19H19N3O2S, Mr= 353.43, Dc= 1.334 g/cm3, S = 1.15, μ = 0.201 mm-1, the final R = 0.035 and wR = 0.111 for 2307 observed reflections （I 〉 2σ（I））. The Flack parameter is -0.03（10）. The preliminary bioassay result indicated that the title compound exhibits strong insecticidal activity （93.75% mortality） against Mythimna separate at the concentration of 1.000 g/L.展开更多
A method for the analysis of the relationship between the helical structure and optical activity was proposed by the study of the conformations and X-ray diffraction structures of some cyclic esters prepared by esteri...A method for the analysis of the relationship between the helical structure and optical activity was proposed by the study of the conformations and X-ray diffraction structures of some cyclic esters prepared by esterification of L-(-)-2.3-O-methylidene threitol and L-(+)-2,3-O-isopropplidene threitol with alkanedioyl dichlorides and o-,m-,and p-phthaloyl dichlorides.展开更多
We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and...We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and exciton energies decrease with increasing chirality angles, and they, as functions of widths, oscillate with the period of three, while the exciton binding energies do not have such distinct oscillation. On the other hand, for cGNRs dominated by zigzag edges, all the energy gaps, exciton energies, and exciton binding energies show oscillation properties with their widths, due to the interactions between the edge states localized at the opposite zigzag edges. In addition, the triplet excitons are energy degenerate when the electrons are spin-unpolarized, while the degeneracy split when the electrons are spin-polarized. All the studied cGNRs show strong excitonic effects with the exciton binding energies of hundreds of meV.展开更多
A variety of phenyl alkyl sulfides were oxidized enantioselectively with NaIO_4 in chiral micellar systems formed from eight chiral surfactants,to give optical active sulfoxides.The enantiomer excesses ranged from 1.6...A variety of phenyl alkyl sulfides were oxidized enantioselectively with NaIO_4 in chiral micellar systems formed from eight chiral surfactants,to give optical active sulfoxides.The enantiomer excesses ranged from 1.6 to 15.0%.To understand the mechanistic detail of this asymmetric oxi- dation in chiral micelle,the effects of structure both in substrates and surfactants on the optical yield of the oxidation were studied and discussed.Generally,increasing the alkyl chain length both in sur- factants and in substrates enhances the optical yield,also the surfactant with hydroxy group at its appropriate position gives better enantioselectivity,suggesting the enzymic characteristics of the chiral micelle.展开更多
Chirality is an indispensable integral of biological system.As an important part of organisms,chiral organic structure of bone has been extensively investigated.However,the chirality of bone minerals is unclear and no...Chirality is an indispensable integral of biological system.As an important part of organisms,chiral organic structure of bone has been extensively investigated.However,the chirality of bone minerals is unclear and not fully determined.Here,we report nine levels of fractal-like chirality of bone minerals by combining electron microscopic and spectrometric characterizations.The primary helically twisted acicular apatite crystals inside collagen fibrils and between fibrils merge laterally to form secondary helical subplatelets.The chiral arrangement of several subplatelets forms tertiary spiral mineral platelets.Further coherent stepwise stacking of mineral platelets with collagen fibrils leads to quaternary to ninth levels,which reconciled the previous conflicting models.The optical activities in the UV-visible,infrared and terahertz regions demonstrated chirality from atomic to macroscopic scales based on circularly selective absorption and Bragg resonance at different levels of chirality.Our findings provide new insight into the structural integrity of bone,osteology,forensic medicine and archaeology and inspire the design of novel biomaterials.展开更多
Retinal degeneration is a main class of ocular diseases.So far,retinal progenitor cell(RPC)transplantation has been the most potential therapy for it,in which promoting RPCs neuronal differentiation remains an unmet c...Retinal degeneration is a main class of ocular diseases.So far,retinal progenitor cell(RPC)transplantation has been the most potential therapy for it,in which promoting RPCs neuronal differentiation remains an unmet challenge.To address this issue,innovatively designed L/D-phenylalanine based chiral nanofibers(LPG and DPG)are employed and it finds that chirality of fibers can efficiently regulate RPCs differentiation.qPCR,western blot,and immunofluorescence analysis show that right-handed helical DPG nanofibers significantly promote RPCs neuronal differentiation,whereas left-handed LPG nanofibers decrease this effect.These effects are mainly ascribed to the stereoselective interaction between chiral helical nanofibers and retinol-binding protein 4(RBP4,a key protein in the retinoic acid(RA)metabolic pathway).The findings of chirality-dependent neuronal differentiation provide new strategies for treatment of neurodegenerative diseases via optimizing differentiation of transplanted stem cells on chiral nanofibers.展开更多
Elastocaloric refrigeration is the most promising green solid-state refrigeration technology to replace conventional vapor compression refrigeration.The development direction of the elastocaloric component that acts a...Elastocaloric refrigeration is the most promising green solid-state refrigeration technology to replace conventional vapor compression refrigeration.The development direction of the elastocaloric component that acts as a key part of the elastocaloric refrigeration system contains a large elastocaloric effect,low stress hysteresis,high heat exchange performance,and small driving loads.The first two indices can be realized by material modification;however,the last two are more dependent on a novel porous structure design.However,the conventional porous structure is confronted with some critical challenges,including inhomogeneous stress,a significant hysteresis area,and deformation instability under the alternating cyclic loading.In this study,a NiTi-based elastocaloric structure model with chirality feature and gradient design as innovative elements was presented,bio-inspired by the structure of the plant tendrils.A quantitative optimization for the NiTi-based elastocaloric structure was performed using the finite element analysis(FEA)method.Strain and martensite volume fraction(MVF)fields during the loading and unloading processes were predicted and evaluated.The simulated results indicated that increasing the thickness gradient g_(1) of the strip or decreasing the diameter gradient g_(2) of the structure was beneficial to achieving more homogeneous strain and martensite distribution,simultaneously with higher energy storage efficiency and specific surface area.In addition,these NiTi-based chiral structures with different structural parameters were fabricated by laser powder bed fusion(LPBF).At the optimized structure parameters of g_(1)=2 and g_(2)=1.11,the LPBF-fabricated NiTi-based chiral structure could achieve an adiabatic temperature change ΔT_(ad) of 2.3 K,driving force of as low as 149.11 N,and|ΔT_(ad)/F|of as high as 15.42 K/kN at a recoverable compressive strain of 10%.展开更多
Hetero-assembling of spherical building blocks with well-defined spatial distribution holds great significance in developing chiral nanostructures. Herein, a strategy for hetero-assembling of gold nanoparticles(Au NPs...Hetero-assembling of spherical building blocks with well-defined spatial distribution holds great significance in developing chiral nanostructures. Herein, a strategy for hetero-assembling of gold nanoparticles(Au NPs) was demonstrated using rigid bifacial DNA origami as templates. By tuning the sizes and the fixed location of Au NPs on DNA origami, right-handed and left-handed Au NPs nanostructures were respectively constructed. Gel electrophoresis indicated the formation of the DNA origami-Au NPs complex and transmission electron microscopy(TEM) visually displayed the arrangement of Au NPs in these two chiral structures. The spatial configuration and 3D geometry of Au NPs were further illustrated by the stereographic TEM with tilting angles from ?30° to 30°. This strategy provides a universal approach to construct the asymmetrical 3D geometries, which may have potential applications in biomimicking and nanophotonics.展开更多
The Nernst effect is a fundamental thermoelectric conversion phenomenon that was deemed to be possible only in systems with magnetic field or magnetization.In this work,we propose a novel dynamical chiral Nernst effec...The Nernst effect is a fundamental thermoelectric conversion phenomenon that was deemed to be possible only in systems with magnetic field or magnetization.In this work,we propose a novel dynamical chiral Nernst effect that can appear in two-dimensional van der Waals materials with chiral structural symmetry in the absence of any magnetic degree of freedom.This unconventional effect is triggered by time variation of an out-of-plane electric field,and has an intrinsic quantum geometric origin linked to not only the intralayer center-of-mass motion but also the interlayer coherence of electronic states.We demonstrate the effect in twisted homobilayer and homotrilayer transition metal dichalcogenides,where the strong twisted interlayer coupling leads to sizable intrinsic Nernst conductivities well within the experimental capacity.This work suggests a new route for electric control of thermoelectric conversion.展开更多
基金the National Natural Science Foundation of China(Grant Nos.12020101001,12021002,11872273,and 11890680)Tianjin Research Program of Application Foundation and Advanced Technology(Grant No.19JCYBJC19300).
文摘Slender chiral filaments are ubiquitous in both artificial and biological materials.Due to their chiral microstructures,chiral filaments usually exhibit favorable properties such as superior elasticity and unusual stretch-twist coupling deformation.However,how these chiral microstructures affect the elastic behavior of filaments remains unclear.In this paper,a refined Cosserat rod model with misfit or mismatching of chirality induced by inhomogeneous arrangement of chiral microstructures incorporated is developed.Using the refined rod model,the force-displacement relationships and variation of structural chirality during the tensile processes of two typical helical structures,i.e.,single-strand helix and double-strand helix,are investigated.The results show that the misfit of chirality can lead to a bend-twist deformation with a high coupling degree,which makes the rod much“soft”when stretched.The chiral filaments undergo an unusual twist when stretched,corresponding to an obviously nonlinear variation of structural chirality.The work suggests that the misfit of chirality can be used to tune the elastic behavior of chiral filaments,which is helpful in guiding the design of flexible actuators and soft devices.
基金supported by National Natural Science foundation of China(Nos.21374060 and 21574081)
文摘Chiral supramolecules prepared by the additive-driven self-assembly of block copolymers provide a facile method to construct helical nanostructures. In this study, we investigated the chiral transfer from chiral tartaric acid to poly（styrene）-b-poly（ethylene oxide） using small-angle X-ray scattering,transmission electron microscopy, circular dichroism, and vibrational circular dichroism. The results showed that the chirality was transferred to both the segments of block copolymer irrespective of the interaction with the chiral additives and formation of helical phase structure. However, the chirality transfer was carried out using different methods： for poly（ethylene oxide） segments, the chirality transfer was carried out via direct hydrogen bond formation; for polystyrene segments, the chirality transfer was carried out via the cooperative motion of block copolymers during the thermal annealing.
基金supported in part by the National Key R&D Program(Grant No.2023YFA1606900)the National Natural Science Foundation of China(Grant No.12235003)。
文摘Chirality,a common phenomenon in nature,appears in structures ranging from galaxies and condensed matter to atomic nuclei.There is a persistent demand for new,high-precision methods to detect chiral structures,particularly at the microscale.Here,we propose a novel method,vortex Mössbauer spectroscopy,for probing chiral structures.By leveraging the orbital angular momentum carried by vortex beams,this approach achieves high precision in detecting chiral structures at scales ranging from nanometers to hundreds of nanometers.Our simulation shows the ratio of characteristic lines in the Mössbauer spectra of ^(57)Fe under vortex beams exhibits differences of up to four orders of magnitude for atomic structures with different arrangements.Additionally,simulations reveal the response of ^(229m)Th chiral structures to vortex beams with opposite angular momenta differs by approximately 49-fold.These significant spectral variations indicate that this new vortex Mössbauer probe holds great potential for investigating the microscopic chiral structures and interactions of matter.
基金supported by the National Natural Science Foundation of China[Grant Nos.52272288 and 51972039]the China Postdoctoral Science Foundation[No.2021M700658].
文摘The construction of carbon nanocoil(CNC)-based chiral-dielectric-magnetic trinity composites is considered as a promising approach to achieve excellent low-frequency microwave absorption.However,it is still challenging to further enhance the low frequency microwave absorption and elucidate the related loss mechanisms.Herein,the chiral CNCs are first synthesized on a threedimensional(3D)carbon foam and then combined with the FeNi/NiFe_(2)O_(4) nanoparticles to form a novel chiral-dielectric-magnetic trinity foam.The 3D porous CNC-carbon foam network provides excellent impedance matching and strong conduction loss.The formation of the FeNi-carbon interfaces induces interfacial polarization loss,which is confirmed by the density functional theory calculations.Further permeability analysis and the micromagnetic simulation indicate that the nanoscale chiral magnetic heterostructures achieve magnetic pinning and coupling effects,which enhance the magnetic anisotropy and magnetic loss capability.Owing to the synergistic effect between dielectricity,chirality,and magnetism,the trinity composite foam exhibits excellent microwave absorption performance with an ultrabroad effective absorption bandwidth(EAB)of 14 GHz and a minimum reflection of loss less than-50 dB.More importantly,the C-band EAB of the foam is extended to 4 GHz,achieving the full C-band coverage.This study provides further guidelines for the microstructure design of the chiral-dielectric-magnetic trinity composites to achieve broadband microwave absorption.
文摘Cuticles of some Chrysina scarabs are characterized by flat, graded, and twisted structures of nanosized chitin fibrils. As inferred from SEM images, each species has its own spatial period or pitch P which is dependent on the depth z through the cuticle. From Berreman’s formalism, taking into account the corresponding P(z) dependence, we evaluate reflection spectra of C. aurigans and C. chrysargyrea scarabs. The spectra display the main spectral features observed in the measured ones when small sections of the cuticles are illuminated with non-polarized light, for wavelengths between 300 and 1100 nm. By considering these twisted structures as 1D photonic crystals, an approach is developed to show how the broad band characterizing the reflection spectra arises from a narrow intrinsic photonic band width, whose spectral position moves through visible and near infrared wavelengths. The role of the epicuticle that covers the twisted structures is analyzed in terms of a waxy layer acting as an anti-reflecting coating that also shows low levels of light scattering.
基金supported by the National Natural Science Foundation of China(Nos.51573131,51173130,21274149 and 21374077)
文摘The crystalline structures and crystallization behaviors of iPP containing β nucleation agent TMB-5 （iPP/TMB-5） were investigated by synchrotron radiation wide angel X-ray diffraction （SR-WAXD）, differential scanning calorimeter （DSC） and polarized light microscope （PLM）. It was found that α-crystallization lagged behind β-crystallization at normal temperatures, but the discrepancy reduced with increasing temperature. TMB-5 could not induce β-iPP when the nucleation agent is wrapped up with α-crystal that crystallized at high temperatures. The polymorphic composition of iPP/TMB-5 was susceptible to the introductory moment of shear. New crystallization process of β-nucleated iPP was proposed to understand the experimental phenomena which could not be explained by those reported in the literature. It was supposed that polymer crystallization initiated from mesophase, and the formations of iPP crystals involved the organization of helical conformation ordering within rnesophase. It was proposed that the iPP melt contained mesophases with stereocomplex-type ordering of right-handed and left-handed helical chains which could be disturbed by shear or TMB-5, leading to different polymorphic structures.
基金supported by the National Key Research and Development Program of China(No.2020YFC1107103)the National Natural Science Foundation of China(No.51821093)the Research Project of Public Welfare Technology Application of Zhejiang Province,China(No.LGF21H010006).
文摘Tracheal stents are an important form of treatment for benign or malignant central airway obstruction.However,the mechanical behavior of current tracheal stents is significantly different from that of the native trachea,which leads to a variety of serious complications.In this study,inspired by the structure of the native trachea,a wavy non-uniform ligament chiral tracheal stent is proposed,in which J-shaped stress-strain behavior and negative Poisson's ratio response are achieved by replacing the tangential ligament of tetrachiral and anti-tetrachiral hybrid structure with a wavy non-uniform ligament.Through the combination of theoretical analysis,finite element analysis and experimental tests,a wide range of desired J-shaped stress-strain curves are explored to mimic the native porcine trachea by tailoring the stent geometry.Besides,the negative Poisson’s ratio and auxetic diameter curves versus axial strain of the stent are also studied in detail,thus contributing to the enhancement of cross-section ventilation and reducing the migration of the stent.This novel tracheal stent with a unique microstructure shows a potential to perfectly match the physiological activities of the native trachea and thereby reduce potential complications.
基金Project supported by the National Natural Science Foundation of China (Grant No. 51072072)the Jiangsu Provincial Natural Science Foundation, China (Grant No. BK2010343)
文摘The structural, electronic, and magnetic properties of transition metal doped platinum clusters MPt6 （M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn） are systematically studied by using the relativistic all-electron density functional theory with the generalized gradient approximation. Most of the doped clusters show larger binding energies than the pure Pt7 cluster, which indicates that the doping of the transition metal atom can stabilize the pure platinum cluster. The results of the highest occupied molecular orbital （HOMO） lowest unoccupied molecular orbital （LUMO） gaps suggest that the doped clusters can have higher chemical activities than the pure Pt7 cluster. The magnetism calculations demonstrate that the variation range of the magnetic moments of the MPt6 clusters is from 0 μB to 7 μB, revealing that the MPt6 clusters have potential utility in designing new spintronic nanomaterials with tunable magnetic properties.
基金partly supported by the NSFC(No.21301023)the 2014 Program for Liaoning Excellent Talents in University(No.LJQ2014138)the Fundamental Research Funds for the Central Universities(No.DC201502080305)
文摘A novel chiral copper（Ⅱ） complex with racemic 1,2-diaminocyclohexane and iodide,[Cu（Ⅱ）（1,2-diaminocyclohexane）_3]（I）_2·3H_2O（1） has been synthesized and structurally characterized by X-ray single-crystal diffraction,elemental analysis,infrared spectroscopy,Raman spectroscopy and thermogravimetric analysis. In complex 1,the CuⅡ ion was coordinated by six nitrogen atoms of three 1,2-diaminocyclohexane molecules. The structure of complex 1 can be described as a supramolecular 3D-like structure which was formed by intermolecular hydrogen-bonding interactions between mononuclear molecules,uncoordinated water molecules and two iodide anions. UV-vis absorption spectrum and surface photovoltage properties of complex 1 have also been studied.
基金Project supported by the National Technology R&D Program (No. 2011 BAE06B01)
文摘The title compound 4-（7-methoxy-2,2-dimethyl-2,3-dihydrobenzofuran-5-yl）-N- （pyridin-2-yl） thiazol-2-amine was synthesized by reacting 2-bromo-1-（7-methoxy-2,2-dime- thyl-2,3-dihydrobenzofuran-5-yl）ethanone with 1-（pyridine-2-yl）thiourea, and its crystal was determined by single-crystal X-ray diffraction. The crystal belongs to the monoclinic system, chiral space group C2 with a = 18.1328（14）, b = 5.5969（5）, c = 19.2195（15） A, β= 115.5420（10）°, V= 1759.9（2）A3, Z = 4, F（000） = 744, C19H19N3O2S, Mr= 353.43, Dc= 1.334 g/cm3, S = 1.15, μ = 0.201 mm-1, the final R = 0.035 and wR = 0.111 for 2307 observed reflections （I 〉 2σ（I））. The Flack parameter is -0.03（10）. The preliminary bioassay result indicated that the title compound exhibits strong insecticidal activity （93.75% mortality） against Mythimna separate at the concentration of 1.000 g/L.
文摘A method for the analysis of the relationship between the helical structure and optical activity was proposed by the study of the conformations and X-ray diffraction structures of some cyclic esters prepared by esterification of L-(-)-2.3-O-methylidene threitol and L-(+)-2,3-O-isopropplidene threitol with alkanedioyl dichlorides and o-,m-,and p-phthaloyl dichlorides.
基金Supported by the National Key Scientific Research Projects of China under Grant No 2015CB932400the National Natural Science Foundation of China under Grant Nos 11504158,61474059,and U1432129+1 种基金the Program for New Century Excellent Talents in University of Ministry of Education of China under Grant No NCET-11-1003the Jiangxi Provincial'Ganpo Talentes 555Projects'
文摘We explore the excitonic effects in chiral graphene nanoribbons (cGNRs), whose edges are composed alternatively of armchair-edged and zigzag-edged segments. For cGNRs dominated by armchair edges, their energy gaps and exciton energies decrease with increasing chirality angles, and they, as functions of widths, oscillate with the period of three, while the exciton binding energies do not have such distinct oscillation. On the other hand, for cGNRs dominated by zigzag edges, all the energy gaps, exciton energies, and exciton binding energies show oscillation properties with their widths, due to the interactions between the edge states localized at the opposite zigzag edges. In addition, the triplet excitons are energy degenerate when the electrons are spin-unpolarized, while the degeneracy split when the electrons are spin-polarized. All the studied cGNRs show strong excitonic effects with the exciton binding energies of hundreds of meV.
文摘A variety of phenyl alkyl sulfides were oxidized enantioselectively with NaIO_4 in chiral micellar systems formed from eight chiral surfactants,to give optical active sulfoxides.The enantiomer excesses ranged from 1.6 to 15.0%.To understand the mechanistic detail of this asymmetric oxi- dation in chiral micelle,the effects of structure both in substrates and surfactants on the optical yield of the oxidation were studied and discussed.Generally,increasing the alkyl chain length both in sur- factants and in substrates enhances the optical yield,also the surfactant with hydroxy group at its appropriate position gives better enantioselectivity,suggesting the enzymic characteristics of the chiral micelle.
基金supported by the National Natural Science Foundation of China(No.21931008,S.C.,21975184,Y.D.,21873072,21922304,L.H.)the science foundation of the Shanghai Municipal science and Technology Commission(19JC1410300,S.C).
文摘Chirality is an indispensable integral of biological system.As an important part of organisms,chiral organic structure of bone has been extensively investigated.However,the chirality of bone minerals is unclear and not fully determined.Here,we report nine levels of fractal-like chirality of bone minerals by combining electron microscopic and spectrometric characterizations.The primary helically twisted acicular apatite crystals inside collagen fibrils and between fibrils merge laterally to form secondary helical subplatelets.The chiral arrangement of several subplatelets forms tertiary spiral mineral platelets.Further coherent stepwise stacking of mineral platelets with collagen fibrils leads to quaternary to ninth levels,which reconciled the previous conflicting models.The optical activities in the UV-visible,infrared and terahertz regions demonstrated chirality from atomic to macroscopic scales based on circularly selective absorption and Bragg resonance at different levels of chirality.Our findings provide new insight into the structural integrity of bone,osteology,forensic medicine and archaeology and inspire the design of novel biomaterials.
基金the HE images.This research was funded by the National Nature Science Foundation of China(NSFC 51833006)the National Key R&D Program of China(2018YFC1106100,2018YFC1106101)+3 种基金SJTU Trans-med Awards Research(WF540162603)the Innovation Program of Shanghai Municipal Education Commission(201701070002E00061)the Shanghai Municipal Commission of Health and Family Planning(201840073)the Science and Technology Commission of Shanghai(17DZ2260100).
文摘Retinal degeneration is a main class of ocular diseases.So far,retinal progenitor cell(RPC)transplantation has been the most potential therapy for it,in which promoting RPCs neuronal differentiation remains an unmet challenge.To address this issue,innovatively designed L/D-phenylalanine based chiral nanofibers(LPG and DPG)are employed and it finds that chirality of fibers can efficiently regulate RPCs differentiation.qPCR,western blot,and immunofluorescence analysis show that right-handed helical DPG nanofibers significantly promote RPCs neuronal differentiation,whereas left-handed LPG nanofibers decrease this effect.These effects are mainly ascribed to the stereoselective interaction between chiral helical nanofibers and retinol-binding protein 4(RBP4,a key protein in the retinoic acid(RA)metabolic pathway).The findings of chirality-dependent neuronal differentiation provide new strategies for treatment of neurodegenerative diseases via optimizing differentiation of transplanted stem cells on chiral nanofibers.
基金This work was supported by National Natural Science Foundation of China(Grant No.52105345)Jiangsu Provincial Key Research and Development plan of China(Grant No.BE2022069-2)Fundamental Research Funds for the Central Universities of China(Grant No.JUSRP122028).
文摘Elastocaloric refrigeration is the most promising green solid-state refrigeration technology to replace conventional vapor compression refrigeration.The development direction of the elastocaloric component that acts as a key part of the elastocaloric refrigeration system contains a large elastocaloric effect,low stress hysteresis,high heat exchange performance,and small driving loads.The first two indices can be realized by material modification;however,the last two are more dependent on a novel porous structure design.However,the conventional porous structure is confronted with some critical challenges,including inhomogeneous stress,a significant hysteresis area,and deformation instability under the alternating cyclic loading.In this study,a NiTi-based elastocaloric structure model with chirality feature and gradient design as innovative elements was presented,bio-inspired by the structure of the plant tendrils.A quantitative optimization for the NiTi-based elastocaloric structure was performed using the finite element analysis(FEA)method.Strain and martensite volume fraction(MVF)fields during the loading and unloading processes were predicted and evaluated.The simulated results indicated that increasing the thickness gradient g_(1) of the strip or decreasing the diameter gradient g_(2) of the structure was beneficial to achieving more homogeneous strain and martensite distribution,simultaneously with higher energy storage efficiency and specific surface area.In addition,these NiTi-based chiral structures with different structural parameters were fabricated by laser powder bed fusion(LPBF).At the optimized structure parameters of g_(1)=2 and g_(2)=1.11,the LPBF-fabricated NiTi-based chiral structure could achieve an adiabatic temperature change ΔT_(ad) of 2.3 K,driving force of as low as 149.11 N,and|ΔT_(ad)/F|of as high as 15.42 K/kN at a recoverable compressive strain of 10%.
基金supported by the National Basic Research Program of China (2012CB933301)the National Natural Science Foundation of China (21305070, 21475064)+2 种基金the Natural Science Foundation of Jiangsu Province (BK20130861)the Sci-tech Support Plan of Jiangsu Province (BE2014719)Science Foundation of Nanjing University of Posts and Telecommunications (213005, 214175).
文摘Hetero-assembling of spherical building blocks with well-defined spatial distribution holds great significance in developing chiral nanostructures. Herein, a strategy for hetero-assembling of gold nanoparticles(Au NPs) was demonstrated using rigid bifacial DNA origami as templates. By tuning the sizes and the fixed location of Au NPs on DNA origami, right-handed and left-handed Au NPs nanostructures were respectively constructed. Gel electrophoresis indicated the formation of the DNA origami-Au NPs complex and transmission electron microscopy(TEM) visually displayed the arrangement of Au NPs in these two chiral structures. The spatial configuration and 3D geometry of Au NPs were further illustrated by the stereographic TEM with tilting angles from ?30° to 30°. This strategy provides a universal approach to construct the asymmetrical 3D geometries, which may have potential applications in biomimicking and nanophotonics.
基金supported by the National Key R&D Program of China(Grant No.2020YFA0309600)the Research Grant Council of Hong Kong(AoE/P-701/20,HKU SRFS2122-7S05,A-HKU705/21)New Cornerstone Science Foundation.C.X.also acknowledges support by the UM Start-up Grant(SRG2023-00033-IAPME).
文摘The Nernst effect is a fundamental thermoelectric conversion phenomenon that was deemed to be possible only in systems with magnetic field or magnetization.In this work,we propose a novel dynamical chiral Nernst effect that can appear in two-dimensional van der Waals materials with chiral structural symmetry in the absence of any magnetic degree of freedom.This unconventional effect is triggered by time variation of an out-of-plane electric field,and has an intrinsic quantum geometric origin linked to not only the intralayer center-of-mass motion but also the interlayer coherence of electronic states.We demonstrate the effect in twisted homobilayer and homotrilayer transition metal dichalcogenides,where the strong twisted interlayer coupling leads to sizable intrinsic Nernst conductivities well within the experimental capacity.This work suggests a new route for electric control of thermoelectric conversion.
