A trinuclear copper complex [Cu_(3)(L2)_(2)(SO_(4))_(2)(H_(2)O)_(7)]·8H_(2)O(1)(HL2=1-hydroxy-3-(pyrazin-2-yl)-N-(pyrazin-2-ylmethyl)imidazo[1,5-a]pyrazine-8-carboxamide) with a multi-substituted imidazo[1,5-a]py...A trinuclear copper complex [Cu_(3)(L2)_(2)(SO_(4))_(2)(H_(2)O)_(7)]·8H_(2)O(1)(HL2=1-hydroxy-3-(pyrazin-2-yl)-N-(pyrazin-2-ylmethyl)imidazo[1,5-a]pyrazine-8-carboxamide) with a multi-substituted imidazo[1,5-a]pyrazine scaffold was serendipitously prepared from the reaction of the pro-ligand of H_(2)L1(N,N'-bis(pyrazin-2-ylmethyl)pyrazine-2,3-dicarboxamide) with CuSO_(4)·5H_(2O) in aqueous solution at room temperature.Complex 1 was characterized by IR,single-crystal X-ray analysis,and magnetic susceptibility measurements.Single-crystal X-ray analysis reveals that the complex consists of three Cu(Ⅱ) ions,two in situ transformed L2~-ligands,two coordinated sulfates,seven coordinated water molecules,and eight uncoordinated water molecules.Magnetic susceptibility measurement indicates that there are obvious ferromagnetic coupling interactions between the adjacent Cu(Ⅱ) ions in 1.CCDC:1852713.展开更多
Chiral topological semimetals hosting multifold fermions and exotic surface states represent a frontier in topological materials research. Among them, noncentrosymmetric cubic B20 compounds—notably transitionmetal si...Chiral topological semimetals hosting multifold fermions and exotic surface states represent a frontier in topological materials research. Among them, noncentrosymmetric cubic B20 compounds—notably transitionmetal silicides and germanides—offer a unique platform for realizing symmetry-protected topological phases and unconventional optoelectronic responses. Here, we report the physical properties of Rh Ge and Co Ge single crystals with B20 structure in detail. Transport measurements revea metallic behavior with characteristic Fermi-liquid scaling at low temperatures, while magnetization results confirm paramagnetism in both compounds. In addition,both materials exhibit low carrier concentrations with small electronic specific heat coefficients, indicating their semimetal feature with weak electronic correlations. Such high-quality Co Ge and Rh Ge single crystals provide a material platform to explore the evolution of multifold fermions and the instability of helicoid-arc surface states with spin–orbit coupling and surface environment in B20 material systems.展开更多
Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four plan...Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four planar N-coordination and one axial P-coordination(Co-N_(4)P_(1))are decorated on the lateral edges of nanorod-like crystalline g-C_(3)N_(4)(CCN)photocatalysts.Significantly,the electronic structures of central Co as active sites for O_(2) reduction reaction(ORR)and planar N-coordinator as active sites for H_(2)O oxidation reaction(WOR)in Co-N_(4)P_(1) can be well regulated by the synergetic effects of introducing axial P-coordinator,in contrast to the decorated Co single-atoms with only four planar N-coordination(Co-N_(4)).Specifically,directional photoelectron accumulation at central Co active sites,induced by an introduced midgap level in Co-N_(4)P_(1),mediates the ORR active sites from 4e–-ORR-selective terminal–NH_(2) sites to 2e–-ORR-selective Co sites,moreover,an elevated d-band center of Co 3d orbital strengthens ORR intermediate*OOH adsorption,thus jointly facilitating a highly selective and active 2e^(–)-ORR pathway to H_(2)O_(2) photosynthesis.Simultaneously,a downshifted p-band center of N_(2)p orbital in Co-N_(4)P_(1) weakens WOR intermediate*OH adsorption,thus enabling a preferable 2e^(–)-WOR pathway toward H_(2)O_(2) photosynthesis.Subsequently,Co-N_(4)P_(1) exhibits exceptional H_(2)O_(2) photosynthesis efficiency,reaching 295.6μmol g^(-1) h^(-1) with a remarkable solar-to-chemical conversion efficiency of 0.32%,which is 15 times that of Co-N_(4)(19.2μmol g^(-1) h^(-1))and 10 times higher than CCN(27.6μmol g^(-1) h^(-1)).This electronic structure modulation on single-atom catalysts offers a promising strategy for boosting the activity and selectivity of H_(2)O_(2) photosynthesis.展开更多
Besides the cross sections of roadways and the tendency and obliquity of roadway axes, the major controlling factors affecting the height of a collapsing roof include the weak lithological structure of surrounding roc...Besides the cross sections of roadways and the tendency and obliquity of roadway axes, the major controlling factors affecting the height of a collapsing roof include the weak lithological structure of surrounding rocks. This thesis analyzes the effect of two single and weak lithological structures of both sides and the roof on the height of a collapsing roof in a deep soft rock road- way. Using the two-dimensional UDEC3.1 software, a numerical structures of both sides of a roadway and of two weak lithological simulation was carried out on the models of weak lithological structures of roof of different depths. We reconstruct the overall processes from a break-away layer, bending, subsidence and the cracking of a collapsing roof. We also illustrate the distribution characteristics of displacement fields in the surrounding rock after the roof collapse in a deep soft rock roadway. The results of our numerical simulations indicate that the form of a roof collapse is side-expanding when the roadway is a weak structure at both sides The height of the roof collapse is related to the lithological combination of the roof when the roadway is a weak structure of the roof.展开更多
We investigate metallic microdisk-size dependence of quantum dot （QD） spontaneous emission rate and micro- antenna directional emission effect for the hybrid metM-distributed Bragg reflector structures based on a pa...We investigate metallic microdisk-size dependence of quantum dot （QD） spontaneous emission rate and micro- antenna directional emission effect for the hybrid metM-distributed Bragg reflector structures based on a particular single QD emission. It is found that the measured photolumineseence （PL） intensity is very sensitive to the size of metMlic disk, showing an enhancement factor of 11 when the optimal disk diameter is 2μm and the numerical aperture of microscope objective NA=0.5. It is found that for large metal disks, the Purcell effect is dominant for enhanced PL intensity, whereas for small size disks the main contribution comes from plasmon scattering at the disk edge within the light cone collected by the microscope objective.展开更多
Developing low-loading single-atom catalysts with superior catalytic activity and selectivity in formaldehyde(HCHO)oxidation at room temperature remains challenging.Herein,ZrO_(2)nanoparticles coupled low-loading Ir s...Developing low-loading single-atom catalysts with superior catalytic activity and selectivity in formaldehyde(HCHO)oxidation at room temperature remains challenging.Herein,ZrO_(2)nanoparticles coupled low-loading Ir single atoms in N-doped carbon(Ir_(1)-N-C/ZrO_(2))was prepared.The optimal Ir_(1)-N-C/ZrO_(2)with 0.25 wt%Ir loading delivers the high HCHO removal and conversion efficiency(>95%)at 20℃,which is higher than that over Ir_(1)-N-C with the same Ir loading.The specific rate can reach 1285.6 mmol gIr^(-1)h^(-1),surpassing the Ir based catalysts reported to date.Density functional theory calculation results and electron spin resonance spectra indicate that the introduction of Zr O_(2)nanoparticles modulate the electronic structure of the Ir single atoms,promoting O_(2)activation to·O_(2)^(–).Moreover,the Ir-C-Zr channel is favorable for the dissociation of·O_(2)^(–)to active oxygen atom(*O),and further accelerates the transformation of HCHO and intermediates(dioxymethylene and formates)to CO_(2)and H_(2)O.This work provides a facile strategy to design low-loading single-atom catalysts with high catalytic activity toward HCHO oxidation.展开更多
The mosaic structure in a Ni-based single-crystal superalloy is simulated by molecular dynamics using a potential employed in a modified analytic embedded atom method. From the calculated results we find that a closed...The mosaic structure in a Ni-based single-crystal superalloy is simulated by molecular dynamics using a potential employed in a modified analytic embedded atom method. From the calculated results we find that a closed threedimensional misfit dislocation network, with index of （011）{100} and the side length of the mesh 89.6A, is formed around a cuboidal γ′ precipitate. Comparing the simulation results of the different mosaic models, we find that the side length of the mesh only depends on the lattice parameters of the γ and γ′ phases as well as the γ/γ′ interface direction, but is independent of the size and number of the cuboidal γ′ precipitate. The density of dislocations is inversely proportional to the size of the cuboidal γ′ precipitate, i.e. the amount of the dislocation is proportional to the total area of the γ/γ′ interface, which may be used to explain the relation between the amount of the fine γ′ particles and the creep rupture life of the superalloy. In addition, the closed three-dimensional networks assembled with the misfit dislocations can play a significant role in improving the mechanical properties of superalloys.展开更多
Precipitation of α-phase in massive and feathery microstructures was studied during aging in the single α field. It was found that the α-phase mainly precipitated along the γ-plate interfaces as laths in the feath...Precipitation of α-phase in massive and feathery microstructures was studied during aging in the single α field. It was found that the α-phase mainly precipitated along the γ-plate interfaces as laths in the feathery structure, while it nucleated at various sites in the massive structure in the form of particles and dominantly as plates. Precipitation of α-plates in the massive structure occurred by the difFusional ledge mechanism. The γm→α reaction proceeded by the growth of previously nucleated α-precipitates, and chiefly by the development of new α-plates展开更多
The single crystals and powder of a Yavapaiite Structure phosphate,namely,PbSb0.5Fe0.5（PO4）2,were synthesized by solid state method and characterized by X-ray single-crystal diffraction and powder diffraction.The ti...The single crystals and powder of a Yavapaiite Structure phosphate,namely,PbSb0.5Fe0.5（PO4）2,were synthesized by solid state method and characterized by X-ray single-crystal diffraction and powder diffraction.The title compound crystallizes in the monoclinic system,space group C2/c（No.15） with a = 16.716（4）,b = 5.186（7）,c = 8.130（2）A,β = 114.93（6）°,Z = 4,R（I 〉 2s（I）） = 0.0430,R indices（all data） = 0.0460,and T = 293（2） K.The title compound belongs to the Yavapaiite Structure A^（Ⅱ）M^（Ⅳ）（PO4）2 compounds,and the Sb1 atom and Fe1 atoms occupy the same site（M） and their occupancy factors are refined to be 0.5 and 0.5 having a sum occupancy factor of 1.0.Its structure consists of [M（PO）4]n^2n- layers running parallel to the（b,c） plane built up of cornerconnected MO6 octahedra and PO4 tetrahedra.Additionally,the calculations of energy band structure,and density of states have been performed with the density functional theory method.The studies of computational calculation and UV experimental results show that the new compound is an indirect band-gap insulator.展开更多
Children from two-parent families have better outcomes,on average,than children from single-parent families.Yet the mechanisms associated with family structure and family process that produce divergent outcomes are le...Children from two-parent families have better outcomes,on average,than children from single-parent families.Yet the mechanisms associated with family structure and family process that produce divergent outcomes are less well understood.Based on data from the 2011-2015 National Health Interview Survey(N=26,783),I leverage the case of military families with deployment and examine the impacts of parenting quality,economic capital,and social capital on children’s psychological well-being.The regression results show that single parenthood produced by divorce,separation,and birth out of wedlock leads to worse child outcomes than single parenthood produced by military deployment,and family process partially explains the variation in children’s well-being beyond family structure.Married families,military or civilian,deployed or not,enjoy advantages that translate into positive child outcomes.Marriage,therefore,emerges as the primary axis of inequality,and maintaining a healthy marriage better promotes children’s well-being.展开更多
Introduction-Nuclei near and beyond the proton drip line represent a fascinating frontier in the nuclear landscape. Proton-rich nuclei exhibit intriguing phenomena, such as the Thomas-Ehrman shift and proton-halo stru...Introduction-Nuclei near and beyond the proton drip line represent a fascinating frontier in the nuclear landscape. Proton-rich nuclei exhibit intriguing phenomena, such as the Thomas-Ehrman shift and proton-halo structure. Beyond the proton dripline, nuclei become unbound, allowing protons to be emitted and giving rise to novel radioactive decay modes. Single-proton radioactivity, a process in which some nuclei with an odd number of protons(Z) decay by ejecting a proton, was discovered several decades ago and has been extensively studied [1, 2].展开更多
Regulating the electronic structure and oxygencontaining intermediates adsorption behavior on Fe-based catalysts is of great significance to cope with the sluggish oxygen reduction reaction(ORR)kinetics,but it still r...Regulating the electronic structure and oxygencontaining intermediates adsorption behavior on Fe-based catalysts is of great significance to cope with the sluggish oxygen reduction reaction(ORR)kinetics,but it still remains a great challenge.In this work,Fe atom clusters(Fe_(AC))modified by high-density Cu single atoms(Cu_(SA))in a N,S-doped porous carbon substrate(Fe_(AC)/Cu_(SA)@NCS)is reported for enhanced ORR electrocatalysis.Fe_(AC)/Cu_(SA)@NCS exhibits excellent ORR performance with a half-wave potential(E_(1/2))of 0.911 V,a high four-electron process selectivity and excellent stability.The ORR performance is also verified in the Fe_(AC)/Cu_(SA)@NCS-based Zn-air battery,which shows a high peak power density of 192.67 mW cm^(-2),a higher specific capacity of 808.3 mAh g^(-1)and impressive charge-discharge cycle stability.Moreover,density functional theory calculations show that Cu single atoms synergistically modulate the electronic structure Fe active atoms in Fe atomic clusters,reducing the energy barrier of the rate-determining step(i.e.,*OH desorption)on Fe_(AC)/Cu_(SA)@NCS.This work provides an effective way to regulate the electronic structure of Fe-based catalysts and optimize their electrocatalytic activity based on the introduction of a second metal source.展开更多
The underappreciated role of supports has severely constrained the modification of single-atom catalysts.It's important to develop a strategy for achieving a strong synergy between catalytic structures and active ...The underappreciated role of supports has severely constrained the modification of single-atom catalysts.It's important to develop a strategy for achieving a strong synergy between catalytic structures and active sites.Here,we devise a structure-inducing method involving the manipulation of the chemical reaction environment and spin-state of Cu single-atom with helical carbon nanotube(HCNT)for CO_(2)efficient electroreduction to formate.Utilizing in situ characterization and finite element simulation,we find that the helical structure effectively enriches HCO_(3)-and OH-on the surface of Cu-N_(2)O_(2)/HCNT catalyst during electrocatalytic CO_(2)reduction,creating a favorable interfacial environment for formate generation.Magnetic characterizations and theoretical calculations reveal spin polarization of Cu-N_(2)O_(2)sites,yielding readily polarized magnetic moments.Consequently,a spin-ordered phase emerges on the surface of Cu-N_(2)O_(2)/HCNT under a magnetic field,enhancing formate selectivity.Impressively,Cu-N_(2)O_(2)/HCNT achieves93.6%formate selectivity at-0.80 V vs.RHE under 200 mT.Under an in situ magnetic field,it maintains over 80%formate selectivity at-175 mA/cm^(2)for 100 h.Our findings offer novel insights into single-atom catalyst modification.展开更多
Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one o...Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one of Lewis’s criteria. The same method was however rapidly applied to represent compounds that do not follow the octet-rule, i.e. compounds for which some of the composing atoms have greater or less than eight electrons in their valence shell. In a previous paper, an even-odd rule was proposed and shown to apply to both types of uncharged molecules. In the present paper, the even-odd rule is extended with the objective to encompass all single-bonded ions in one group: Lewis’s ions, hypo- and hypervalent ions. The base of the even-odd representation is compatible with Lewis’s diagram. Additionally, each atom is subscripted with an even number calculated by adding the valence number, the number of covalent bonds of the element, and its electrical charge. This paper describes how to calculate the latter number and in doing so, how charge and electron-pairs can actually be precisely localized. Using ions known to be compatible with Lewis’s rule of eight, the even-odd rule is compared with the former. The even-odd rule is then applied to ions known as hypo- or hypervalent. An interesting side effect of the presented rule is that charge and electron-pairs are unambiguously assigned to one of the atoms composing the single-charged ion. Ions that follow the octet rule and ions that do not, are thus reconciled in one group called “electron-paired ions” due to the absence of unpaired electrons. A future paper will focus on the connection between the even-odd rule and molecules or ions having multiple bonds.展开更多
In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the nu...In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the number of covalent bonds that each atom forms with its neighbors and multiple bonds are frequent. Lewis’ octet rule has unfortunately shown limitations very early when applied to non-organic compounds: most of them remain incompatible with the “rule of eight” and location of charges is uncertain. In an attempt to unify structural formulas of octet and non-octet molecules or single-charge ions, an even-odd rule was recently proposed, together with a procedure to locate charge precisely. This even-odd rule has introduced a charge-dependent effective-valence number calculated for each atom. With this number and the number of covalent bonds of each element, two even numbers are calculated. These numbers are both used to understand and draw structuralformulas of single-covalent-bonded compounds. In the present paper, a procedure is proposed to adjust structural formulas of compounds that are commonly represented with multiple bonds. In order to keep them compatible with the even-odd rule, they will be represented using only single covalent bonds. The procedure will then describe the consequences of bond simplification on charges locations. The newly obtained representations are compared to their conventional structural formulas, i.e. single-bond representation vs. multiple-bond structures. Throughout the comparison process, charges are precisely located and assigned to specific atoms. After discussion of particular cases of compounds, the paper finally concludes that a rule limiting representations of multiplecovalent bonds to single covalent bonds, seems to be suitable for numerous known compounds.展开更多
Indium selenide,aⅢ–Ⅴgroup semiconductor with layered structure,attracts intense attention in various photoelectric applications,due to its outstanding properties.Here,we report super deformability and thermoelectri...Indium selenide,aⅢ–Ⅴgroup semiconductor with layered structure,attracts intense attention in various photoelectric applications,due to its outstanding properties.Here,we report super deformability and thermoelectricity ofγ-In Se single crystals grown by modified Bridgeman method.The crystal structure of In Se is studied systematically by transmission electron microscopy methods combined with x-ray diffraction and Raman spectroscopy.The predominate phase ofγ-In Se with dense stacking faults and local multiphases is directly demonstrated at atomic scale.The bulkγ-In Se crystals demonstrate surprisingly high intrinsic super deformative ability which is highly pliable with bending strains exceeding12.5%and 264%extension by rolling.At the meantime,In Se also possesses graphite-like features which is printable,writable,and erasable.Finally,the thermoelectric properties ofγ-In Se bulk single crystals are preliminary studied and thermal conductivity can be further reduced via bending-induced defects.These findings will enrich the knowledge of structural and mechanical properties'flexibility of In Se and shed lights on the intrinsic and unique mechanical properties of In Se polytypes.展开更多
Developing high performance and low-cost catalysts for oxygen reduction reaction(ORR)in challenging acid condition is vital for proton-exchange-membrane fuel cells(PEMFCs).Carbon-supported nonprecious metal single ato...Developing high performance and low-cost catalysts for oxygen reduction reaction(ORR)in challenging acid condition is vital for proton-exchange-membrane fuel cells(PEMFCs).Carbon-supported nonprecious metal single atom catalysts(SACs)have been identified as potential catalysts in the field.Great advance has been obtained in constructing diverse active sites of SACs for improving the performance and understanding the fundamental principles of regulating acid ORR performance.However,the ORR performance of SACs is still unsatisfactory.Importantly,microenvironment adjustment of SACs offers chance to promote the performance of acid ORR.In this review,acid ORR mechanism,attenuation mechanism and performance improvement strategies of SACs are presented.The strategies for promoting ORR activity of SACs include the adjustment of center metal and its microenvironment.The relationship of ORR performance and structure is discussed with the help of advanced experimental investigations and theoretical calculations,which will offer helpful direction for designing advanced SACs for ORR.展开更多
The local maxima of water density in the space near the single-helical of Konjac glucomannan as well as the dominant conformation of the system was studied by molecular dyna-mics under the water environment. The resul...The local maxima of water density in the space near the single-helical of Konjac glucomannan as well as the dominant conformation of the system was studied by molecular dyna-mics under the water environment. The results indicate that the hydration shell,potential energy,and its hydrogen bond network with water bridges of the left-handed single-helix conformation was favored compared to those of right-handed single-helix conformation. This work suggests that the left-handed single-helix conformation was the dominant conformation of KGM in the water environment.展开更多
A novel layered oxouranium phosphite open-structure [（C10H24N2）（H2O）][（UO2）2（HPO3）3]（denoted as TJPU-8,TJPU=Tianjin Polytechnic University） was hydrothermally synthesized with isophorondiamine（IPDA） as the...A novel layered oxouranium phosphite open-structure [（C10H24N2）（H2O）][（UO2）2（HPO3）3]（denoted as TJPU-8,TJPU=Tianjin Polytechnic University） was hydrothermally synthesized with isophorondiamine（IPDA） as the template.Single crystal structure refinement disclosed that TJPU-8 crystallized in the monoclinic space group P21c with cell parameters a=1.8346（9） nm,b=0.6734（1） nm,c=2.0639（0） nm,β=114.61（5）°,V=2.3182（8） nm3,Z=2.TJPU-8 was constructed by UO7 monomer,U2O12 dimer and HPO3 groups.The monomeric UO7 or dimeric U2O12 was connected by HPO3 groups to form two types of 4-ring chains.An undulating sheet was then generated by connecting these two types of chains via HPO3 bridges.The layer structure formed by stacking the sheets along the a direction via the strong H-bonds of organoamine cations and water molecules intercalated in the interlayer spaces with the framework oxygen atoms.Although a mixture of cis-and trans-IPDA was used,only cis-IPDA served as the template.A typical green light emission of TJPU-8 is observed when excited by 266 nm laser.展开更多
A new heterobimetallic nitrilotriacetatoperoxotitanate complex with the formula of [Mn（H2O）5]2[Ti（O2）2O（nta）2]·7H2O （1, C6H6O6N = H3nta） has been isolated in pure crystals. It was characterized by element...A new heterobimetallic nitrilotriacetatoperoxotitanate complex with the formula of [Mn（H2O）5]2[Ti（O2）2O（nta）2]·7H2O （1, C6H6O6N = H3nta） has been isolated in pure crystals. It was characterized by elemental analyses, IR, thermal analysis （TGA） and single-crystal X-ray diffraction. Complex 1 crystallizes in monoclinic, space group C2/c with a = 15.088（3）, b = 13.311（3）, c = 17.741（4） , β = 100.92（3）°, Z = 4, V = 3498.6（12） 3, Mr = 968.19, Dc = 1.838 g/cm3, μ = 1.266 mm-1, F（000） = 1992, R = 0.0337 and wR = 0.0819. Single-crystal X-ray analysis reveals that the titanium atom is N,O,O＇,O＇＇-chelated by the nitrilotriacetate and O,O＇-chelated by the peroxo group, and is coordinated to the bridging O atom in an overall pentagonal-bipyramidal geometry. The manganese ions in the compound are both 6-coordinated by five water molecules and one bridged carboxylato oxygen atom. A decameric water cluster consisting of a cyclic water hexamer in a boat fashion is also found in complex 1. The TGA and XRD results prove that 1 undergoes facile thermal decomposition to form the mixture of Mn2O3 and TiO2 at 600～800 ℃, and pure MnTiO3 at 900 ℃.展开更多
文摘A trinuclear copper complex [Cu_(3)(L2)_(2)(SO_(4))_(2)(H_(2)O)_(7)]·8H_(2)O(1)(HL2=1-hydroxy-3-(pyrazin-2-yl)-N-(pyrazin-2-ylmethyl)imidazo[1,5-a]pyrazine-8-carboxamide) with a multi-substituted imidazo[1,5-a]pyrazine scaffold was serendipitously prepared from the reaction of the pro-ligand of H_(2)L1(N,N'-bis(pyrazin-2-ylmethyl)pyrazine-2,3-dicarboxamide) with CuSO_(4)·5H_(2O) in aqueous solution at room temperature.Complex 1 was characterized by IR,single-crystal X-ray analysis,and magnetic susceptibility measurements.Single-crystal X-ray analysis reveals that the complex consists of three Cu(Ⅱ) ions,two in situ transformed L2~-ligands,two coordinated sulfates,seven coordinated water molecules,and eight uncoordinated water molecules.Magnetic susceptibility measurement indicates that there are obvious ferromagnetic coupling interactions between the adjacent Cu(Ⅱ) ions in 1.CCDC:1852713.
基金supported by National Key R&D Program of China (Grant Nos.2022-YFA1403800,2023YFA1406000,and 2023YFA1406500)the National Natural Science Foundation of China (Grant Nos.12274459,12474002,22171283,and 52130103)+1 种基金China Postdoctoral Science Foundation (Grant No.2023M730011)supported by the Synergetic Extreme Condition User Facility (SECUF,https://cstr.cn/31123.02.SECUF)。
文摘Chiral topological semimetals hosting multifold fermions and exotic surface states represent a frontier in topological materials research. Among them, noncentrosymmetric cubic B20 compounds—notably transitionmetal silicides and germanides—offer a unique platform for realizing symmetry-protected topological phases and unconventional optoelectronic responses. Here, we report the physical properties of Rh Ge and Co Ge single crystals with B20 structure in detail. Transport measurements revea metallic behavior with characteristic Fermi-liquid scaling at low temperatures, while magnetization results confirm paramagnetism in both compounds. In addition,both materials exhibit low carrier concentrations with small electronic specific heat coefficients, indicating their semimetal feature with weak electronic correlations. Such high-quality Co Ge and Rh Ge single crystals provide a material platform to explore the evolution of multifold fermions and the instability of helicoid-arc surface states with spin–orbit coupling and surface environment in B20 material systems.
文摘Single-atom catalysts are promising for H_(2)O_(2) photosynthesis from O_(2) and H_(2)O,but their efficiency is still limited by the ill-defined electronic structure.In this study,Co single-atoms with unique four planar N-coordination and one axial P-coordination(Co-N_(4)P_(1))are decorated on the lateral edges of nanorod-like crystalline g-C_(3)N_(4)(CCN)photocatalysts.Significantly,the electronic structures of central Co as active sites for O_(2) reduction reaction(ORR)and planar N-coordinator as active sites for H_(2)O oxidation reaction(WOR)in Co-N_(4)P_(1) can be well regulated by the synergetic effects of introducing axial P-coordinator,in contrast to the decorated Co single-atoms with only four planar N-coordination(Co-N_(4)).Specifically,directional photoelectron accumulation at central Co active sites,induced by an introduced midgap level in Co-N_(4)P_(1),mediates the ORR active sites from 4e–-ORR-selective terminal–NH_(2) sites to 2e–-ORR-selective Co sites,moreover,an elevated d-band center of Co 3d orbital strengthens ORR intermediate*OOH adsorption,thus jointly facilitating a highly selective and active 2e^(–)-ORR pathway to H_(2)O_(2) photosynthesis.Simultaneously,a downshifted p-band center of N_(2)p orbital in Co-N_(4)P_(1) weakens WOR intermediate*OH adsorption,thus enabling a preferable 2e^(–)-WOR pathway toward H_(2)O_(2) photosynthesis.Subsequently,Co-N_(4)P_(1) exhibits exceptional H_(2)O_(2) photosynthesis efficiency,reaching 295.6μmol g^(-1) h^(-1) with a remarkable solar-to-chemical conversion efficiency of 0.32%,which is 15 times that of Co-N_(4)(19.2μmol g^(-1) h^(-1))and 10 times higher than CCN(27.6μmol g^(-1) h^(-1)).This electronic structure modulation on single-atom catalysts offers a promising strategy for boosting the activity and selectivity of H_(2)O_(2) photosynthesis.
基金supported by the National Basic Research Program of China (No2006 CB202200)
文摘Besides the cross sections of roadways and the tendency and obliquity of roadway axes, the major controlling factors affecting the height of a collapsing roof include the weak lithological structure of surrounding rocks. This thesis analyzes the effect of two single and weak lithological structures of both sides and the roof on the height of a collapsing roof in a deep soft rock road- way. Using the two-dimensional UDEC3.1 software, a numerical structures of both sides of a roadway and of two weak lithological simulation was carried out on the models of weak lithological structures of roof of different depths. We reconstruct the overall processes from a break-away layer, bending, subsidence and the cracking of a collapsing roof. We also illustrate the distribution characteristics of displacement fields in the surrounding rock after the roof collapse in a deep soft rock roadway. The results of our numerical simulations indicate that the form of a roof collapse is side-expanding when the roadway is a weak structure at both sides The height of the roof collapse is related to the lithological combination of the roof when the roadway is a weak structure of the roof.
基金Supported by the National Key Basic Research Program of China under Grant No 2013CB922304the National Natural Science Foundation of China under Grant Nos 11474275 and 11464034
文摘We investigate metallic microdisk-size dependence of quantum dot （QD） spontaneous emission rate and micro- antenna directional emission effect for the hybrid metM-distributed Bragg reflector structures based on a particular single QD emission. It is found that the measured photolumineseence （PL） intensity is very sensitive to the size of metMlic disk, showing an enhancement factor of 11 when the optimal disk diameter is 2μm and the numerical aperture of microscope objective NA=0.5. It is found that for large metal disks, the Purcell effect is dominant for enhanced PL intensity, whereas for small size disks the main contribution comes from plasmon scattering at the disk edge within the light cone collected by the microscope objective.
基金supported by the Strategic Priority Research Program of the Chinese Academy of Sciences,China(Nos.XDA23010300 and XDA23010000)National Science Foundation of China,China(Nos.52200137 and 21725102)+1 种基金the Plan for“National Youth Talents”GuangDong Basic and Applied Basic Research Foundation(No.2021A1515110427)。
文摘Developing low-loading single-atom catalysts with superior catalytic activity and selectivity in formaldehyde(HCHO)oxidation at room temperature remains challenging.Herein,ZrO_(2)nanoparticles coupled low-loading Ir single atoms in N-doped carbon(Ir_(1)-N-C/ZrO_(2))was prepared.The optimal Ir_(1)-N-C/ZrO_(2)with 0.25 wt%Ir loading delivers the high HCHO removal and conversion efficiency(>95%)at 20℃,which is higher than that over Ir_(1)-N-C with the same Ir loading.The specific rate can reach 1285.6 mmol gIr^(-1)h^(-1),surpassing the Ir based catalysts reported to date.Density functional theory calculation results and electron spin resonance spectra indicate that the introduction of Zr O_(2)nanoparticles modulate the electronic structure of the Ir single atoms,promoting O_(2)activation to·O_(2)^(–).Moreover,the Ir-C-Zr channel is favorable for the dissociation of·O_(2)^(–)to active oxygen atom(*O),and further accelerates the transformation of HCHO and intermediates(dioxymethylene and formates)to CO_(2)and H_(2)O.This work provides a facile strategy to design low-loading single-atom catalysts with high catalytic activity toward HCHO oxidation.
基金Project supported by the State Key Development Program for Basic Research of China （Grant No G2000067102） and the National Natural Science Foundation of China （Grant No 90101004）.
文摘The mosaic structure in a Ni-based single-crystal superalloy is simulated by molecular dynamics using a potential employed in a modified analytic embedded atom method. From the calculated results we find that a closed threedimensional misfit dislocation network, with index of （011）{100} and the side length of the mesh 89.6A, is formed around a cuboidal γ′ precipitate. Comparing the simulation results of the different mosaic models, we find that the side length of the mesh only depends on the lattice parameters of the γ and γ′ phases as well as the γ/γ′ interface direction, but is independent of the size and number of the cuboidal γ′ precipitate. The density of dislocations is inversely proportional to the size of the cuboidal γ′ precipitate, i.e. the amount of the dislocation is proportional to the total area of the γ/γ′ interface, which may be used to explain the relation between the amount of the fine γ′ particles and the creep rupture life of the superalloy. In addition, the closed three-dimensional networks assembled with the misfit dislocations can play a significant role in improving the mechanical properties of superalloys.
文摘Precipitation of α-phase in massive and feathery microstructures was studied during aging in the single α field. It was found that the α-phase mainly precipitated along the γ-plate interfaces as laths in the feathery structure, while it nucleated at various sites in the massive structure in the form of particles and dominantly as plates. Precipitation of α-plates in the massive structure occurred by the difFusional ledge mechanism. The γm→α reaction proceeded by the growth of previously nucleated α-precipitates, and chiefly by the development of new α-plates
基金Supported by the National Natural Science Foundation of China(21101156 and 61376002)State Key Laboratory of Structure Chemistry(No.20150016)+1 种基金Outstanding Youth of Colleges and Universities of Department of Education,Fujian Province Natural Science Foundation for Youths(No.2016J05109)Fujian Education Department(No.JK2015056)
文摘The single crystals and powder of a Yavapaiite Structure phosphate,namely,PbSb0.5Fe0.5（PO4）2,were synthesized by solid state method and characterized by X-ray single-crystal diffraction and powder diffraction.The title compound crystallizes in the monoclinic system,space group C2/c（No.15） with a = 16.716（4）,b = 5.186（7）,c = 8.130（2）A,β = 114.93（6）°,Z = 4,R（I 〉 2s（I）） = 0.0430,R indices（all data） = 0.0460,and T = 293（2） K.The title compound belongs to the Yavapaiite Structure A^（Ⅱ）M^（Ⅳ）（PO4）2 compounds,and the Sb1 atom and Fe1 atoms occupy the same site（M） and their occupancy factors are refined to be 0.5 and 0.5 having a sum occupancy factor of 1.0.Its structure consists of [M（PO）4]n^2n- layers running parallel to the（b,c） plane built up of cornerconnected MO6 octahedra and PO4 tetrahedra.Additionally,the calculations of energy band structure,and density of states have been performed with the density functional theory method.The studies of computational calculation and UV experimental results show that the new compound is an indirect band-gap insulator.
文摘Children from two-parent families have better outcomes,on average,than children from single-parent families.Yet the mechanisms associated with family structure and family process that produce divergent outcomes are less well understood.Based on data from the 2011-2015 National Health Interview Survey(N=26,783),I leverage the case of military families with deployment and examine the impacts of parenting quality,economic capital,and social capital on children’s psychological well-being.The regression results show that single parenthood produced by divorce,separation,and birth out of wedlock leads to worse child outcomes than single parenthood produced by military deployment,and family process partially explains the variation in children’s well-being beyond family structure.Married families,military or civilian,deployed or not,enjoy advantages that translate into positive child outcomes.Marriage,therefore,emerges as the primary axis of inequality,and maintaining a healthy marriage better promotes children’s well-being.
文摘Introduction-Nuclei near and beyond the proton drip line represent a fascinating frontier in the nuclear landscape. Proton-rich nuclei exhibit intriguing phenomena, such as the Thomas-Ehrman shift and proton-halo structure. Beyond the proton dripline, nuclei become unbound, allowing protons to be emitted and giving rise to novel radioactive decay modes. Single-proton radioactivity, a process in which some nuclei with an odd number of protons(Z) decay by ejecting a proton, was discovered several decades ago and has been extensively studied [1, 2].
基金financially supported by the National Natural Science Foundation of China(No.22278042)the National Natural Science Foundation of Jiangsu Province(No.BK20240567)+2 种基金the Introduction and Cultivation of Leading Innovative Talents Foundation of Changzhou,Jiangsu Province(No.CQ20220093)the Natural Science Foundation of the Jiangsu Higher Education Institutions of China(No.24KJD530001)the Open Project Program of Key Laboratory of Optic-electric Sensing and Analytical Chemistry for Life Science(No.M2024-7),MOE
文摘Regulating the electronic structure and oxygencontaining intermediates adsorption behavior on Fe-based catalysts is of great significance to cope with the sluggish oxygen reduction reaction(ORR)kinetics,but it still remains a great challenge.In this work,Fe atom clusters(Fe_(AC))modified by high-density Cu single atoms(Cu_(SA))in a N,S-doped porous carbon substrate(Fe_(AC)/Cu_(SA)@NCS)is reported for enhanced ORR electrocatalysis.Fe_(AC)/Cu_(SA)@NCS exhibits excellent ORR performance with a half-wave potential(E_(1/2))of 0.911 V,a high four-electron process selectivity and excellent stability.The ORR performance is also verified in the Fe_(AC)/Cu_(SA)@NCS-based Zn-air battery,which shows a high peak power density of 192.67 mW cm^(-2),a higher specific capacity of 808.3 mAh g^(-1)and impressive charge-discharge cycle stability.Moreover,density functional theory calculations show that Cu single atoms synergistically modulate the electronic structure Fe active atoms in Fe atomic clusters,reducing the energy barrier of the rate-determining step(i.e.,*OH desorption)on Fe_(AC)/Cu_(SA)@NCS.This work provides an effective way to regulate the electronic structure of Fe-based catalysts and optimize their electrocatalytic activity based on the introduction of a second metal source.
基金the support and funding from the Fundamental Research Funds for Central Universitiessupported by the Shanghai Science and Technology Commission(19DZ2271500)supported by Beijing Zhongkebaice Technology Service Co.,Ltd.
文摘The underappreciated role of supports has severely constrained the modification of single-atom catalysts.It's important to develop a strategy for achieving a strong synergy between catalytic structures and active sites.Here,we devise a structure-inducing method involving the manipulation of the chemical reaction environment and spin-state of Cu single-atom with helical carbon nanotube(HCNT)for CO_(2)efficient electroreduction to formate.Utilizing in situ characterization and finite element simulation,we find that the helical structure effectively enriches HCO_(3)-and OH-on the surface of Cu-N_(2)O_(2)/HCNT catalyst during electrocatalytic CO_(2)reduction,creating a favorable interfacial environment for formate generation.Magnetic characterizations and theoretical calculations reveal spin polarization of Cu-N_(2)O_(2)sites,yielding readily polarized magnetic moments.Consequently,a spin-ordered phase emerges on the surface of Cu-N_(2)O_(2)/HCNT under a magnetic field,enhancing formate selectivity.Impressively,Cu-N_(2)O_(2)/HCNT achieves93.6%formate selectivity at-0.80 V vs.RHE under 200 mT.Under an in situ magnetic field,it maintains over 80%formate selectivity at-175 mA/cm^(2)for 100 h.Our findings offer novel insights into single-atom catalyst modification.
文摘Lewis developed a 2D-representation of molecules, charged or uncharged, known as structural formula, and stated the criteria to draw it. At the time, the vast majority of known molecules followed the octet-rule, one of Lewis’s criteria. The same method was however rapidly applied to represent compounds that do not follow the octet-rule, i.e. compounds for which some of the composing atoms have greater or less than eight electrons in their valence shell. In a previous paper, an even-odd rule was proposed and shown to apply to both types of uncharged molecules. In the present paper, the even-odd rule is extended with the objective to encompass all single-bonded ions in one group: Lewis’s ions, hypo- and hypervalent ions. The base of the even-odd representation is compatible with Lewis’s diagram. Additionally, each atom is subscripted with an even number calculated by adding the valence number, the number of covalent bonds of the element, and its electrical charge. This paper describes how to calculate the latter number and in doing so, how charge and electron-pairs can actually be precisely localized. Using ions known to be compatible with Lewis’s rule of eight, the even-odd rule is compared with the former. The even-odd rule is then applied to ions known as hypo- or hypervalent. An interesting side effect of the presented rule is that charge and electron-pairs are unambiguously assigned to one of the atoms composing the single-charged ion. Ions that follow the octet rule and ions that do not, are thus reconciled in one group called “electron-paired ions” due to the absence of unpaired electrons. A future paper will focus on the connection between the even-odd rule and molecules or ions having multiple bonds.
文摘In organic chemistry, as defined by Abegg, Kossel, Lewis and Langmuir, compounds are normally represented using structural formulas called Lewis structures. In these structures, the octet rule is used to define the number of covalent bonds that each atom forms with its neighbors and multiple bonds are frequent. Lewis’ octet rule has unfortunately shown limitations very early when applied to non-organic compounds: most of them remain incompatible with the “rule of eight” and location of charges is uncertain. In an attempt to unify structural formulas of octet and non-octet molecules or single-charge ions, an even-odd rule was recently proposed, together with a procedure to locate charge precisely. This even-odd rule has introduced a charge-dependent effective-valence number calculated for each atom. With this number and the number of covalent bonds of each element, two even numbers are calculated. These numbers are both used to understand and draw structuralformulas of single-covalent-bonded compounds. In the present paper, a procedure is proposed to adjust structural formulas of compounds that are commonly represented with multiple bonds. In order to keep them compatible with the even-odd rule, they will be represented using only single covalent bonds. The procedure will then describe the consequences of bond simplification on charges locations. The newly obtained representations are compared to their conventional structural formulas, i.e. single-bond representation vs. multiple-bond structures. Throughout the comparison process, charges are precisely located and assigned to specific atoms. After discussion of particular cases of compounds, the paper finally concludes that a rule limiting representations of multiplecovalent bonds to single covalent bonds, seems to be suitable for numerous known compounds.
基金the National Natural Science Foundation of China(Grant Nos.11674040,11604032,51472036,51672270,and 11904039)the Fundamental Research Funds for the Central Universities,China(Grant No.106112016CDJZR308808)Key Research Program of Frontier Sciences,Chinese Academy of Sciences(Grant No.QYZDB-SSW-SLH016)。
文摘Indium selenide,aⅢ–Ⅴgroup semiconductor with layered structure,attracts intense attention in various photoelectric applications,due to its outstanding properties.Here,we report super deformability and thermoelectricity ofγ-In Se single crystals grown by modified Bridgeman method.The crystal structure of In Se is studied systematically by transmission electron microscopy methods combined with x-ray diffraction and Raman spectroscopy.The predominate phase ofγ-In Se with dense stacking faults and local multiphases is directly demonstrated at atomic scale.The bulkγ-In Se crystals demonstrate surprisingly high intrinsic super deformative ability which is highly pliable with bending strains exceeding12.5%and 264%extension by rolling.At the meantime,In Se also possesses graphite-like features which is printable,writable,and erasable.Finally,the thermoelectric properties ofγ-In Se bulk single crystals are preliminary studied and thermal conductivity can be further reduced via bending-induced defects.These findings will enrich the knowledge of structural and mechanical properties'flexibility of In Se and shed lights on the intrinsic and unique mechanical properties of In Se polytypes.
基金supported by the Joint Funds of the National Natural Science Foundation of China(U20A20280)the Postgraduate Scientific Research Innovation Project of Hunan Province(CX20210171)。
文摘Developing high performance and low-cost catalysts for oxygen reduction reaction(ORR)in challenging acid condition is vital for proton-exchange-membrane fuel cells(PEMFCs).Carbon-supported nonprecious metal single atom catalysts(SACs)have been identified as potential catalysts in the field.Great advance has been obtained in constructing diverse active sites of SACs for improving the performance and understanding the fundamental principles of regulating acid ORR performance.However,the ORR performance of SACs is still unsatisfactory.Importantly,microenvironment adjustment of SACs offers chance to promote the performance of acid ORR.In this review,acid ORR mechanism,attenuation mechanism and performance improvement strategies of SACs are presented.The strategies for promoting ORR activity of SACs include the adjustment of center metal and its microenvironment.The relationship of ORR performance and structure is discussed with the help of advanced experimental investigations and theoretical calculations,which will offer helpful direction for designing advanced SACs for ORR.
基金supported by the National Natural Science Foundation of China (30871749,30901004,31071518)Natural Science Foundation of Fujian Province (2009J01061)
文摘The local maxima of water density in the space near the single-helical of Konjac glucomannan as well as the dominant conformation of the system was studied by molecular dyna-mics under the water environment. The results indicate that the hydration shell,potential energy,and its hydrogen bond network with water bridges of the left-handed single-helix conformation was favored compared to those of right-handed single-helix conformation. This work suggests that the left-handed single-helix conformation was the dominant conformation of KGM in the water environment.
基金Supported by the National Natural Science Foundation of China(Nos.20771030,20671025)
文摘A novel layered oxouranium phosphite open-structure [（C10H24N2）（H2O）][（UO2）2（HPO3）3]（denoted as TJPU-8,TJPU=Tianjin Polytechnic University） was hydrothermally synthesized with isophorondiamine（IPDA） as the template.Single crystal structure refinement disclosed that TJPU-8 crystallized in the monoclinic space group P21c with cell parameters a=1.8346（9） nm,b=0.6734（1） nm,c=2.0639（0） nm,β=114.61（5）°,V=2.3182（8） nm3,Z=2.TJPU-8 was constructed by UO7 monomer,U2O12 dimer and HPO3 groups.The monomeric UO7 or dimeric U2O12 was connected by HPO3 groups to form two types of 4-ring chains.An undulating sheet was then generated by connecting these two types of chains via HPO3 bridges.The layer structure formed by stacking the sheets along the a direction via the strong H-bonds of organoamine cations and water molecules intercalated in the interlayer spaces with the framework oxygen atoms.Although a mixture of cis-and trans-IPDA was used,only cis-IPDA served as the template.A typical green light emission of TJPU-8 is observed when excited by 266 nm laser.
基金supported by the Fundamental Research Funds for the Central Universities, SCUT (No. 2009ZM0313) the National Natural Science Foundation of China (B5080320)
文摘A new heterobimetallic nitrilotriacetatoperoxotitanate complex with the formula of [Mn（H2O）5]2[Ti（O2）2O（nta）2]·7H2O （1, C6H6O6N = H3nta） has been isolated in pure crystals. It was characterized by elemental analyses, IR, thermal analysis （TGA） and single-crystal X-ray diffraction. Complex 1 crystallizes in monoclinic, space group C2/c with a = 15.088（3）, b = 13.311（3）, c = 17.741（4） , β = 100.92（3）°, Z = 4, V = 3498.6（12） 3, Mr = 968.19, Dc = 1.838 g/cm3, μ = 1.266 mm-1, F（000） = 1992, R = 0.0337 and wR = 0.0819. Single-crystal X-ray analysis reveals that the titanium atom is N,O,O＇,O＇＇-chelated by the nitrilotriacetate and O,O＇-chelated by the peroxo group, and is coordinated to the bridging O atom in an overall pentagonal-bipyramidal geometry. The manganese ions in the compound are both 6-coordinated by five water molecules and one bridged carboxylato oxygen atom. A decameric water cluster consisting of a cyclic water hexamer in a boat fashion is also found in complex 1. The TGA and XRD results prove that 1 undergoes facile thermal decomposition to form the mixture of Mn2O3 and TiO2 at 600～800 ℃, and pure MnTiO3 at 900 ℃.
