Phase-change memory based on matched Ge-Te,Sb-Te,and In-Te octahedrons:Improved electrical performances and robust thermal stability

Phase-change memory(PCM)has been developed for three-dimensional(3D)data storage devices,posing huge challenges to the thermal stability and reliability of PCM.However,the low thermal stability of Ge2Sb2Te5(GST)limits further application.Here,we demonstrate PCM based on In0.9Ge2Sb2Te5(IGST)alloy,showing 180C 10-years data retention,6 ns set speed,one order of magnitude longer life time,and 75%reduced power consumption compared to GST-based device.The In can occupy the cationic positions and the In-Te octahedrons with good phase-change properties can geometrically match well with the host Ge-Te and Sb-Te octahedrons,acting as nucleation centers to boost the set speed and enhance the endurance of IGST device.Introducing stable matched phase-change octahedrons can be a feasible way to achieve practical PCMs.

Anchoring CoP nanoparticles on the octahedral CoO by self-phosphating for enhanced photocatalytic overall water splitting activity under visible light

Designing an effective and stable composite photocatalyst is of significance for the further realization of practical applications. In this study, a series of CoP/CoO composites are successfully prepared by a straight one-step phosphating method. The reasonable design and controllable preparation of CoP/CoO composite make it exhibit improved photocatalytic performance for overall water splitting and excellent stability under visible light irradiation in comparison with pure CoO, which is derived from the CoP nanoparticles well dispersed on the(111) facets of CoO octahedrons, intimate interface between them and efficiently accelerated of photo-induced electrons from CoO to CoP. This study presents a simple method to design highly-effective composite photocatalysts for overall water splitting to meet the energy demand.

Simultaneously Effi cient Solar Light Harvesting and Charge Transfer of Hollow Octahedral Cu_(2)S/CdS p-n Heterostructures for Remarkable Photocatalytic Hydrogen Generation

Solar-driven water splitting is a promising alternative to industrial hydrogen production.This study reports an elaborate design and synthesis of the integration of cadmium sulfi de(CdS)quantum dots and cuprous sulfi de(Cu_(2)S)nanosheets as three-dimensional(3D)hollow octahedral Cu_(2)S/CdS p-n heterostructured architectures by a versatile template and one-pot sulfi dation strategy.3D hierarchical hollow nanostructures can strengthen multiple refl ections of solar light and provide a large specifi c surface area and abundant reaction sites for photocatalytic water splitting.Owing to the construction of the p-n heterostructure as an ideal catalytic model with highly matched band alignment at Cu_(2)S/CdS interfaces,the emerging internal electric fi eld can facilitate the space separation and transfer of photoexcited charges between CdS and Cu_(2)S and also enhance charge dynamics and prolong charge lifetimes.Notably,the unique hollow Cu_(2)S/CdS architectures deliver a largely enhanced visible-light-driven hydrogen generation rate of 4.76 mmol/(g·h),which is nearly 8.5 and 476 times larger than that of pristine CdS and Cu_(2)S catalysts,respectively.This work not only paves the way for the rational design and fabrication of hollow photocatalysts but also clarifi es the crucial role of unique heterostructure in photocatalysis for solar energy conversion.

Syntheses, Characterization and Crystal Structures of Two Novel Oxazoline Based Titanium Complexes

Two novel titanium compounds [（E）-N＇-（2,6-diisopropylphenyl）-N-（2-（4,4-dimethyl-4,5-dihydrooxazol-2-yl）phenyl）benzimidamido]titanium trichloride（1） and [N-（2-（4,4-dimethyl-4,5-dihydrooxaz-ol-2-yl）phenyl）-6-（2,4,6-triisopropyl-phenyl） pyridin-2-amido]titanium trichloride（2） were synthesized by reacting the corresponding ligand with diethylaminetitaniumtrichloride in equal molar ratios. The compounds were characterized with 1H, 13 C NMR, elemental analysis and single-crystal X-ray diffraction analysis. The geometry of both compounds is distorted octahedron. The three nitrogen and one chlorine atoms are in the equatorial plane. Compound 1 crystallizes in orthorhombic system, space group P212121 with a = 10.3520（4）, b = 16.5750（7）, c = 17.1530（7） , Z = 4 and V = 2943.2（2）3. Compound 2 crystalizes in the monoclinic system, space group P21/n with a = 15.6400（11）, b = 10.12.60（7）, c = 22.9120（14）, Z = 4 and V = 3558.5（4）3. The synthesized compounds were employed for ethylene polymerization catalysis. Both complexes showed moderate activity when activated with dry methylaluminoxane（d MAO） and complex 1 produced very high molecular weight polyethylene.

On self-affine tiles that are homeomorphic to a ball

Let M be a 3×3 integer matrix which is expanding in the sense that each of its eigenvalues is greater than 1 in modulus and let D?Z^(3)be a digit set containing|det M|elements.Then the unique nonempty compact set T=T(M,D)defined by the set equation MT=T+D is called an integral self-affine tile if its interior is nonempty.If D is of the form D={0,v,...,(|det M|-1)v},we say that T has a collinear digit set.The present paper is devoted to the topology of integral self-affine tiles with collinear digit sets.In particular,we prove that a large class of these tiles is homeomorphic to a closed 3-dimensional ball.Moreover,we show that in this case,T carries a natural CW complex structure that is defined in terms of the intersections of T with its neighbors in the lattice tiling{T+z:z∈Z^(3)}induced by T.This CW complex structure is isomorphic to the CW complex defined by the truncated octahedron.

Atomic-level unveiling secondary recrystallization enabled microand macroscopic polarization enhancement for piezophotocatalytic oxygen activation

Piezoelectric semiconductors bear the bifunctional photocatalysis and piezocatalysis,while the absent or weak internal charge driving force severely restricts its catalytic activity.Developing polarization strategy is desirable,and particularly understanding its mechanism from a microscopic perspective remains scanty.Herein,we report a secondary recrystallization approach to achieving the simultaneous micro-and macroscopic polarization enhancement on Bi2WO6 nanosheets for boosting piezo-photocatalytic oxygen activation,and unravel the mechanism at an atom-level.The secondary recrystallization process not only results in a strengthened distortion of[WO6]octahedra with distortion index enhancement by~20%for a single octahedron,but also enables lateral crystal growth of nanosheets along the ab plane(av.50 to 180 nm),which separately allows the rise in dipole moment of unit cell(e.g.,1.63 D increase along a axis)and the stacking of the distorted[WO6]octahedron to accumulate the unit cell dipole,collectively contributing to the considerably strengthened spontaneous polarization and piezoelectricity.Besides,exposure of large-area{001}front facet enables more efficient capture and conversion of stress into piezo-potential.Therefore,the well-recrystallized Bi2WO6 nanosheets exhibit considerably promoted piezo-photocatalytic reactive oxygen species generation,given the decreased specific surface area.This work presents a feasible methodology to regulate inside-out polarization for guiding carriers transfer behavior,and may advance the solid understanding on the intrinsic mechanism.

Platinum nickel alloy-MXene catalyst with inverse opal structure for enhanced hydrogen evolution in both acidic and alkaline solutions

The development of an efficient Pt-based electrocatalyst in acidic and alkaline electrolytes is of great significance to the field of electrocatalytic hydrogen evolution.Herein,we report a strategy for in situ growth of Pt_(3)Ni truncated octahedrons on Ti3C2Tx nanosheets and then obtain an ordered porous catalyst via a template method.Meanwhile,we use the finite element calculation to clarify the relationship between the component structure and performance and find that the performance of the spherical shell microstructure catalyst is higher than that of the disc structure catalyst,which is also verified by experiments.The experimental analysis shows that the ordered porous catalyst is conducive to enhancing electrocatalytic hydrogen evolution activity in acidic and alkaline electrolytes.In an acidic solution,the overpotential is 25 mV(10 mA·cm^(−2)),and the Tafel slope is 22.86 mV·dec−1.In an alkaline solution,the overpotential is 44.1 mV(10 mA·cm^(−2)),and the Tafel slope is 39.06 mV·dec−1.The synergistic coupling between Ti3C2Tx and Pt_(3)Ni nanoparticles improves the stability of the catalyst.The in situ growth strategy and design of microstructure with its correlation with catalytic performance represent critical steps toward the rational synthesis of catalysts with excellent catalytic activity.

Effect of Sb-induced oxygen octahedral distortion on piezoelectric performance and thermal stability of Pb(In,Nb)O_(3)-Pb(Hf,Ti)O_(3)ceramics

The combination of excellent thermal stability and outstanding electrical performance is of great sig-nificance for piezoelectric ceramics.Herein,we have prepared 0.11Pb(In_(0.5)Nb_(0.5))O_(3)-0.89Pb(Hf_(0.47)Ti_(0.53))O_(3)-Sb_(2)O_(5)(PIN-PHT-x Sb)ceramics by solid-phase method and investigated the effect of oxygen octahedral lattice distortion on microstructure and macroscopic electrical properties.The distortion index of oxygen octahedra is studied by Rietveld refinement,showing that optimal octahedral distortion can soften B-O repulsion,disrupt long-range ordered ferroelectric domains,and enhance local heterogeneities,signifi-cantly increasing piezoelectric properties.Moreover,outstanding thermal stability and ultrahigh piezo-electric response of PIN-PHT-1.2Sb ceramics are realized under the synergistic influence of octahedral distortion,excellent density,and large grain size.Compared with PIN-PHT ceramics,PIN-PHT-1.2Sb ce-ramics exhibit ultrahigh piezoelectric responses(d_(33)=706 pC/N,k_(p)=0.68,ε_(r)=3244),a high Curie temperature(T C)of 300℃,excellent thermal stability,and anti-fatigue properties.

Engineering yolk-shell CuCo_(2)S_(4)@Cu_(2)O Z-scheme nanoreactors for accelerating generation of value-added chemicals and of degradation multi-organic contaminants

The synthesis of solar-driven chemical value-added products and the degradation of pollutants is a promising approach for sustainable development. However, achieving these works via photocatalysts with efficient charge-separation, photo-absorption is challenging. A yolk-shell CuCo_(2)S_(4)@Cu_(2)O Z-scheme nanoreactor (YS-CuCo_(2)S_(4)@Cu_(2) O-NR) with octahedron Cu_(2)O as the core and tubular CuCo2 S4 as the shell, has been synthesized by regulating composition and morphology. YS-CuCo_(2)S_(4)@Cu_(2)O-NR shows superior photocatalytic activities for producing H_(2) O_(2) collaborates by selective oxidation of benzyl alcohol (BA) to high value-added benzaldehyde (BAD)/utilized Fenton-like reaction to degrade multi-pollutants through space-confinement effect, reaching 80% conversion and 99% selectivity of BA, a yield of 12 mM g^(−1) for H_(2)O_(2) and above 90% degradation efficiency for multi-pollutants. A photocatalysis nanoconfinement reactor system is proposed and demonstrated by using yolk-shell to enhance the performance of the chemical reaction. Mechanism studies show that the yolk-shell provides confined space to accelerate redox reaction kinetics;while the inner void promotes light harvesting and keeps yolk Cu_(2) O from deactivation;combined with the Z-scheme charge transfer, engineering Cu^(+) /Cu^(2+) active composition, they are favorable for enhancing the H_(2) O_(2) generation and Fenton-like activity. These findings provide new opportunities for application of yolk-shell Z-scheme metal-oxide-based photocatalysts.

Shape-Controlled Synthesis of Mn_(3)O_(4) Nanocrystals and Their Catalysis of the Degradation of Methylene Blue

Various sizes and shapes of Mn_(3)O_(4) nanocrystals have been prepared in a one-pot synthesis in extremely dilute solution by soft template self-assembly. To better control size and shape, the effects of varying the growth time, reaction temperature, surfactant, and manganese source were examined. The average size of octahedral Mn_(3)O_(4) crystallites was found to be related to the reaction time, while higher reaction temperature (150 °C) and the use of a cetyltrimethylammonium bromide/poly(vinylpyrrolidone) (CTAB/PVP) mixture allowed construction of a better-defined octahedral morphologies. When PVP or poly(ethylene oxide)-poly(propylene oxide) (P123) was used as template, large-scale agglomeration resulting in loss of the octahedral morphology occurred and crystallites with a quasi-spherical shape were obtained. The nano-octahedral crystallites were shown to be an efficient catalyst for the oxidation of methylene blue.

高度多孔的铂铅纳米晶用作高效的多元醇电氧化催化剂（英文）

本论文采用简便的湿化学刻蚀法首次成功合成了具有明确形貌、组分和多孔性的PtPb/Pt多孔纳米晶.由于具有高度开放的三维立体结构和合金效应, PtPb/Pt多孔纳米晶的多元醇电催化性能良好.其中,最优化的Pt_3Pb多孔纳米片在乙二醇氧化反应中的催化活性为1.75 mA cm^(-2)和1.19 A mg_(Pt)^(-1),在丙三醇氧化反应中的催化活性为1.46 mA cm^(-2)和1.00 A mg_(Pt)^(-1),均远远高于商业Pt/C催化剂的催化活性.另外, Pt_3Pb多孔纳米片在乙二醇和丙三醇氧化反应中均表现出优异的电催化稳定性,分别经过20000个循环和5000个循环后,其催化活性没有发生明显衰减且纳米结构没有发生改变.因此, Pt_3Pb多孔纳米片可作为一种非常有发展前景的铂基电催化剂应用于多元醇燃料电池及相关领域中.

Hydrothermal growth of octahedral Fe_3O_4 crystals

This paper reports the growth of octahedral magnetic Fe3O4 particles from iron powders via a simple alkaline hydrothermal process. The chemical compositions and morphologies of the as-grown Fe3O4 particles were characterized by X-ray diffraction （XRD）, X-ray photoelectron spectra （XPS）, and scanning electron microscopy （SEM）. Structure characterization showed that the phase structure of the prepared particles evolved from α-Fe to pure Fe3O4 with increasing concentration of KOH, indicating the important role of KOH concentration on the formation of the magnetite octahedron. The magnetic properties of samples were also studied by means of a vibrating sample magnetometer （VSM）. The pure magnetite Fe3O4 octahedrons exhibited a relatively high saturation magnetization of 96.7 emu/g.

Facile synthesis of perfect ZnSn（OH）6 octahedral microcrystallines with controlled size and high sensing performance towards ethanol

Uniform and monodisperse ZnSn（OH）6 perfect octahedrons have been synthesized by a facile coprecipitation reaction process. The particle size of the asprepared ZnSn（OH）6 octahedral structure can be readily controlled by adjusting the reaction temperature （T）, and the side length of ZnSn（OH）6 octahedrons was tailored from 3 pm （40℃） to 4 pm （60℃） and 5 μm （80℃）. The ethanol sensing properties of ZnSn（OH）6 octahedrons were carefully investigated. The gas sensing experimental data show that the sensor based on ZnSn（OH）6 （40℃） has good selectivity, fast response/recovery time and the highest response （Ra/Rg = 23.8） to 200 ppm ethanol at relatively low optimum operating temperature （200℃） compared to sensors based on ZnSn（OH）6 （60℃） and ZnSn（OH）6 （80℃）, which might result from different specific surface areas. The study demonstrated that perfect octahedral ZnSn（OH）6 with controlled crystalline size and desirable sensing performance can be synthesized by a simple fabrication procedure, and the octahedral ZnSn（OH）6 could be a highly promising material for high-performance sensors.

Thermal annealing synthesis of double-shell truncated octahedral Pt-Ni alloys for oxygen reduction reaction of polymer electrolyte membrane fuel cells

Shape-controlled Pt-Ni alloys usually offer an exceptional electrocatalytic activity toward the oxygen reduction reaction(ORR)of polymer electrolyte membrane fuel ceils(PEMFCs),whose tricks lie in welldesigned structures and surface morphologies.In this paper,a novel synthesis of truncated octahedral PtNi_(3.5) alloy catalysts that consist of homogeneous Pt-Ni alloy cores enclosed by NiO-Pt double shells through thermally annealing defective heterogeneous PtNi35 alloys is reported.By tracking the evolution of both compositions and morphologies,the outward segregation of both PtOv and NiO are first observed in Pt-Ni alloys.It is speculated that the diffusion of low-coordination atoms results in the formation of an energetically favorable truncated octahedron while the outward segregation of oxides leads to the formation of NiO-Pt double shells.It is very attractive that after gently removing the NiO outer shell,the dealloyed truncated octahedral core-shell structure demonstrates a greatly enhanced ORR activity.The asobtained truncated octahedral Pt_(2.1)Ni core-shell alloy presents a 3.4-folds mass-specific activity of that for unannealed sample,and its activity preserves 45.4%after 30000 potential cycles of accelerated degradation test(ADT).The peak power density of the dealloyed truncated octahedral Pt2jNi core-shell alloy catalyst based membrane electrolyte assembly(MEA)reaches 679.8 mW/cm^(2),increased by 138.4 mW/cm^(2) relative to that based on commercial Pt/C.

Structure of Hexakis(imidazole)nickel(II) Nitrate Water Solvate:[Ni(Im)_6] (NO_3)_2·4H_2O

Crystal structure of the title compound, (NO 3) 2·4H 2O (Im=imidazole), was determined by X-ray crystallographic analysis. The crystal structure consists of discrete Ni^(Im) 2+ 6 cation, NO - 3 anion and four uncoordinated water molecules. It crystallizes in the hexagonal system, space group P63, with lattice parameters a=b= 0.9003(2) nm, c= 2.1034(4) nm, and Z=2. The Ni(II) ion is centro- symmetric octahedron geometry with the NiN 6 core. Six imidazole molecules are coordinated to each nickel(II) atom through its tertiary nitrogen atom. The short and long bond distances of Ni-N are 0.2059(6) and 0.2204(7) nm, respectively. In the solid state, 2+, H 2O moieties and nitrate anions form the three dimensional hydrogen bonds network which stabitizes the crystal structure.

SYNTHESIS AND X-RAY CRYSTAL STRUCTURE OF HEXANUCLEAR COBALT-SELENIUM CLUSTER COMPOUND[Co_6(μ3-Se)_8(PEt_3)_6]BPh_4

Ⅰ. INTRODUCTION Polynuclear metal cluster compounds have attracted much interest owing to their novel structural features and potential uses as heterogeneous catalysts. The structural characterization of these cluster compounds is of fundamental importance in establishing the relationship between the geometric and electronic structures. Recently, we have

Superconductivity of a cuprate with compressed local octahedron

Since the historical discovery of high Tc superconductivity(HTS)of La2CuO4 in 1986[1],the superconductivity me chanism of copper oxides remains one of the biggest mysteries in the field of condensed matter physics[2-10].High-Tc cuprates crystallize into layered perovskite structure,as well as copper oxygen octahedron coordination.In octahedron symmetry,the 3d orbitals of Cu^2+with a 3d^9 configuration degenerate into two top eg and three lower t2g orbitals.

Evolution of stellated gold nanoparticles:New conceptual insights into controlling the surface processes

Understanding the surface processes(deposition and surface diffusion)that occur at or close to the surface of growing nanoparticles is important for fabricating reproducibly stellated or branched gold nanoparticles with precise control over arm length and spatial orientation of arms around the core.By employing a simple seed-mediated strategy,we investigate the key synthetic variables for precise tuning of in situ surface processes(competition between the deposition and surface diffusion).These variables include the reduction rate of a reaction,the packing density of molecules/ions on the high surface energy facets,and temperature.As a result,the thermodynamically stabilized nanoparticles(cuboctahedron and truncated cube)and kinetic products(cube,concave cube,octapod,stellated octahedron,and rhombic dodecahedron)in different sizes with high quantitative shape yield(>80%)can be obtained depending on the reduction rate of reaction and the packing density of molecules/ions.With computer simulation,we studied the stability of stellated(branched structure)and non-stellated(non-branched structure)gold nanoparticles at high temperature.We construct a morphology phase diagram by varying different synthetic parameters,illustrating the formation of both stellated and non-stellated gold nanoparticles in a range of reaction conditions.The stellated gold nanoparticles display shape-dependent optical properties and can be self-assembled into highly ordered superstructures to achieve an enhanced plasmonic response.Our strategy can be applied to other metal systems,allowing for the rational design of advanced new stellated metal nanoparticles with fascinating symmetry dependent plasmonic,catalytic,and electronic properties for technological applications.

Effect of octahedron tilt on the structure and magnetic properties of bismuth ferrite

Multiferroic BiFeO_(3)-based ceramics were synthesized using the rapid liquid-phase sintering method.The rare-earth ion(Sm^(3+),Gd^(3+),Y^(3+))doping causes structural distortion without changing the intrinsic rhombohedral perovskite structure.Raman analysis shows that the effect of doping on E modes is greater than A1 modes,and the microstructure of FeO_(6) octahedron can be regulated by ion doping.A-site trivalent ion doped ceramics exhibit improved magnetism compared with pure BiFeO_(3) ceramic,which originated from the suppressed spiral spin structure of Fe ions.The tilt of FeO_(6) octahedron as a typical structure instability causes the anomalous change of the imaginary part of permittivity at high frequency,and doped ceramics exhibit natural resonance around 16-17 GHz.

Precise Assembly and Supramolecular Catalysis of Tetragonal-and Trigonal-Elongated Octahedral Coordination Containers

The construction of distorted or irregular coordination polyhedrons with specific shapes and functionalities is highly challenging.Here,we demonstrate a viable strategy for attaining a severely distorted octahedral coordination container through precise geometrical manipulation of its nanocavity along the C_(3) or C4 axis to turn on its supramolecular catalysis.We constructed a tetragonal-elongated octahedral coordination container utilizing sulfonylcalix[4]arene-capped Co4 units as six vertexes and tetragonalelongated from single-arm lengthened 5-[(4-carboxybenzyl)amino]isophthalate(L)as eight triangular faces.Through the concomitant introduction of C_(3)-symmetry cyclohexane-1,3,5-tricarboxylate as a secondary linker to construct two equilateral triangular base surfaces and L to build six isosceles triangular side planes,trigonal antiprismatic architecture(trigonal-elongated octahedron)was attained.The elongated octahedral containers exhibited distinctly higher binding capacity and stronger binding affinity toward reaction substrates than that of regular octahedral containers;thus,promoting geometry-dependent catalytic reactivity.Our geometrical manipulation strategy provides a viable approach for the convenient design of metal–organic materials with specific functionalities.