Chain-like Structure Research Articles

Krebs-Type {M2(WO2)2[B-β-SbW9O33]2}n− (M = SbIII, (WO3)) Tungstoantimonate Possessing Unique Pseudo-Seesaw Sb–O Structure

Two new Krebs-type tungstoantimonates (H2en)8H6{[Sb2(WO2)2(B-β-SbW9O33)2][(WO2)2(WO3)2(B-β-SbW9O33)2]}·22H2O (1) and (H2en)7[(WO2)2(WO3)2(B-β-SbW9O33)2]·12H2O (2) were synthesized and characterized. Notably, crystal 1 possesses a specific pseudo-seesaw SbO4 subunit in the central metal belt of [Sb2(WO2)2(B-β-SbW9O33)2]12- species, which is rare in reported Krebs-type polyoxometalates. One of the structural features is that there are two kinds of Krebs-type polyanionic clusters in crystal 1 labeled as {(WO2)2(WO3)2(B-β-SbW9O33)2} (part A) and {Sb2(WO2)2(B-β-SbW9O33)2} (part B), respectively. The subunits A and B are alternately connected through Sb-O-W bonds into a chain-like structure of inorganic clusters. Moreover, the catalytic property of crystals 1 and 2 for electron-transfer reaction were investigated by transferring K3[Fe(CN)6] into K4[Fe(CN)6].

Ru nanoassembly catalysts for hydrogen evolution and oxidation reactions in electrolytes at various pH values

Here, in an effort to prepare Ru-based metal organic frameworks, we developed a one-step solvothermal synthesis for Ru nanoassembly catalysts, which consist of ˜4 nm Ru nanoparticles well dispersed on amorphous carbon (Ru/C). The Ru/C catalyst obtained from a mixed solvent of H2O and CH3CH2OH (Ru/C-H2O/CH3CH2OH), featured a chain-like porous structure, provides Pt-like catalytic properties with low overpotentials at −10 mA cm−2 for the hydrogen evolution reaction (HER) within a wide range of pH values, i.e., 35 mV in 0.5 M H2SO4, 53 mV in 1.0 M KOH, and 93 mV in 3.5 wt% NaCl. Ru/C is also an efficient hydrogen oxidation reaction (HOR) catalyst at all pH values. In the alkaline media, Ru/C-H2O/CH3CH2OH achieves a mass activity of 41.1 mA mg-1 at an overpotential of 50 mV and a high exchange current density (0.65 mA cm−2). The work provides a facile strategy to synthesize highly active Ru/C catalysts for bifunctional HER and HOR electrocatalysis.

Hydrothermal synthesis of VS4/CNTs composite with petal-shape structures performing a high specific capacity in a large potential range for high-performance symmetric supercapacitors

Vanadium sulfide (VS4) is recognized as a good anode material for energy storage devices because of its chain-like structure and high content of sulfur. Herein, the patronite VS4 anchored on carbon nanocubes (denoted as VS4/CNTs) with a petal-shape structure consisting of nanolayers is successfully prepared through a one-step hydrothermal reaction. The influence of the optimal ratio of VS4 and CNTs on the electrochemical properties of VS4/CNTs composite is studied by cyclic voltammetry (CV), galvanostatic charge-discharge (GCD) and electrochemical impedance spectroscopy (EIS). The addition of CNTs increases the conductivity and relieves the volume expansion/contraction, resulting excellent electrochemical properties of VS4/CNTs. In the potential window of −1.4 V to 1.4 V, the VS4/CNTs composite electrode delivers an outstanding specific capacitance of 330 F g−1 (924 C g−1) at 1 A g−1, which is much higher than that of VS2 with 105 F g−1 (294 C g−1). The VS4/CNTs symmetric supercapacitor (SSC) device exhibits the areal capacitance as high as 676 mF cm−2 (1488 mC cm−2) at 0.5 mA cm−2, and the energy density of 4.55 W h m−2 (51.2 W h kg−1) at the power density of 2.75 W m−2 (30.95 W kg−1) within a large voltage up to 2.2 V. All the results confirm that VS4/CNTs composite with petal-shape structures is a promising material for high-performance energy storage devices.

A novel holmium–mercury complex: Structure, green photoluminescence, energy transfer mechanism and semiconducting properties

The complex (Ho(IA)3(H3O)(H2O)) n(0.5 nHg2I6) (HIA = isonicotinic acid) has been synthesized via a hydrothermal reaction and has a one-dimensional (1D) chain-like structure. It has an emission band in the green region of 542 nm, which could originate from the 5 S2 → 5 I8 transition of the Ho3+ ion. The compound possesses Commission Internationale de I’Éclairage chromaticity coordinates of (0.2065, 0.4969) and has a wide optical band gap of 2.32 eV, as found by solid-state UV-Vis diffuse reflectance measurements.

Copper(I)-Based Highly Emissive All-Inorganic Rare-Earth Halide Clusters

Summary The development of new environmentally friendly luminescent materials is crucial for future solid-state lighting, sensor, and display applications. Here, a Cu(I)-based all-inorganic rare-earth halide material, Rb 8 CuSc 3 Cl 18 , has been synthesized by a solid-state reaction method. In this compound, two Cu(I) ions are connected to three rare-earth halide octahedra to form a paddle-wheel-like cluster. The Cu(I) coordinated rare-earth halide clusters contribute to a strong blue photoluminescence emission. This Cu(I)-regulated emission can be extended to other isostructural compounds, such as Rb 8 CuY 3 Cl 18 . Moreover, the crucial role of Cu(I) has been illustrated by the isostructural non-emissive Rb 8 AgSc 3 Cl 18 . On the basis of comprehensive spectroscopy studies and density functional theory calculations, we found that Cu(I) photo-oxidation and correct orbital-energy-level alignment are crucial for the observed bright-blue emission through a proposed metal (Cu)-to-octahedra ([ScCl 6 ] 3− ) charge-transfer mechanism. The discovery of Cu(I)-based all-inorganic rare-earth halide clusters establishes a new strategy for constructing promising emissive halide materials.

Anomalous Magnetoelectric Coupling Effect of CoFe2O4–BaTiO3 Binary Mixed Fluids

We report an anomalous magnetoelectric coupling effect of CoFe2O4–BaTiO3 binary mixed fluids, which were prepared by distributing surfactant treated (oleic acid) magnetic CoFe2O4 and ferroelectric BaTiO3 nanoparticles into highly insulating base fluid (silicone oil). A strong coupling effect in this mixed fluid has been observed, in which both the remnant polarization/magnetization and coercive electric/magnetic field are found to be enhanced visibly in the presence of an external magnetic/electric field. Colossal converse and direct magnetoelectric coupling coefficients are estimated to be αH = 1.22 × 10–4Oe·cm/V and αE = 2.52 × 104 V/(cm·Oe), respectively. Moreover, this coefficient clearly depends on the volume fraction of the two kinds of particles and the applied external magnetic/electric field. Even more amazing, CoFe2O4 also shows a strong magnetoelectric coupling effect with a coefficient as high as 4.2 × 10–5 Oe·cm/V. Further analysis indicates that the aggregated, chain-like structure of the pa...

Fabrication of 1D long chain-like metal porphyrin-based coordination complexes for high-efficiency hydrogen evolution and photoelectric response

Hydrogen production from electrocatalytic water splitting has aroused extensive attention in many fields recently. Fabrication of low-cost and high-efficiency electrocatalysts are still an urgent and challenging work. Porphyrins as visible-light photosensitizers have been extensively utilized in visible-light photocatalysts and photoelectronic materials. So, fabrication of novel porphyrin-based complexes will be benefited for high-efficiency hydrogen evolution and photoelectric response. Here a series of zirconium porphyrin-based coordination complexes were successfully fabricated via a facile two-step strategy. Due to the unique long chain-like structure and low charge-transfer resistance, the zirconium porphyrin-based coordination complexes displayed excellent electrocatalytic performance for hydrogen evolution reaction. The ZrTPP-PTA-1 showed a low overpotential of 60 mV at the current density 10 mA cm−2 and a Tafel slope of 87 mV dec−1 with an ultralow electron transfer resistance of 17.5 Ω. In addition, a quick photocurrent response occurred for these coordination complexes with a visible-light illumination. The photocurrent of the ZrTPP-OA-2 rised up to 2.5 μA under visible-light irradiation. With this pleasant result, these zirconium porphyrin-based coordination complexes have a great potential to become available alternative of current noble electrocatalysts for photoelectric application.

Products on electrodes in an argon-methane magnetically rotating arc at atmospheric pressure

The arc discharge method in a hydrocarbon atmosphere has a promising application in the nanocarbon synthesis field due to its high yield. In this paper, products on electrodes in an argon-methane magnetically rotating arc at atmospheric pressure are investigated. Different nanocarbons are obtained on the cathode and anode surfaces, respectively. Material analysis indicates that the products on the cathode are mainly carbon tubes. Some carbon tubes are well-aligned in one direction, and the others have a coil-like structure. The products on the anode are a mixture of graphene nano-flakes and aggregate hollow carbon particles. The hollow carbon particles exhibit a chain-like structure with internal space to be connected. To the authors’ knowledge, this is possibly the first time that aggregate hollow carbon particles with a chain-like structure have been observed in the absence of any catalyst. Based on the configuration of arc plasma, the formation mechanism of electrode products is briefly proposed.

Organically templated metal sulfate-oxalates: Solvent-free synthesis, crystal structure, and proton conduction

Two new metal sulfate-oxalates, namely, (H4bapp)0.5·VO(SO4)(C2O4) (SCU-11) and H2depa⋅Mn2(SO4)(C2O4)2(H2O)⋅H2O (SCU-13), were prepared under solvent-free conditions, where bapp = 1,4-bis(3-aminopropyl)piperazine and depa = 3-(diethylamino)propylamine. SCU-11 has a chainlike structure containing pendant SO4 groups. SCU-13 has a three-dimensional open-framework structure with chainlike manganese oxalate chains assembled by SO4 groups. Notably, SCU-11 shows excellent water stability and a high proton conductivity of 1.2 × 10−3 S cm−1 at 25 °C under 98% relative humidity. The magnetic susceptibility data for the two compounds were also reported.

Monte Carlo simulations of magnetic particle suspensions with a simple assessment method for the particle overlap between magnetic spheroids

We have developed a simple assessment method for the overlap between spheroidal particles, which neither requires the complex manipulation of vectors and matrices that is indispensable in the ordinary methods, nor is based on a model potential. Moreover, we have developed an evaluation method for the interaction energy arising from the overlap of the steric layer coating spheroidal particles. This is based on a sphere-connected particle model, but some modifications are introduced in order to express an appropriate repulsive interaction energy at the deepest overlapping position. We have investigated the phase change in a magnetic spheroidal particle suspension for a two-dimensional system by means of Monte Carlo simulations. In the case of no external magnetic field, if the magnetic particle-particle interaction is sufficiently strong to favour cluster formation, long raft-like clusters tend to be formed in a dilute situation. With decreasing values of area fraction, a chain-like structure in a dense situation transforms into a raft-like structure within a narrow range of the particle area fraction. Similarly, the raft-like clusters are preferred in a weak applied magnetic field, but an increase in the field strength induces a phase change from a raft-like into a chain-like structure.Highlights of the present paper:A simple assessment method has been proposed for the overlap between two spheroidal particles.The particle overlap assessment is free from a complex mathematical manipulation regarding vectors and matrices.A modified sphere-connected model has been proposed in order to more accurately evaluate a repulsive interaction due to the overlap of the steric layers coating spheroidal particles.2D Monte Carlo simulations have been performed to elucidate the phenomenon of a phase change by magnetic spheroidal particles on a material plane surface.A phase change between a raft-like and a chain-like aggregate structure is able to be controlled by the area fraction of particles and an external magnetic field.

Insulin amyloid fibrils-templated rational self-assembly of vine-tree-like PtRh nanocatalysts for efficient methanol electrooxidation

Shape-controlled synthesis of platinum-based alloy nanocatalysts with well-designed size and structure is essential for developing highly efficient catalysts. Here, a biomolecule-based strategy for the synthesis of vine-tree-like PtRh nanowires (VT-PtRhNWs) using insulin amyloid fibrils (INSAFs) as sacrificial templates is presented. In this structure, the inner PtRh nanowires behave as the rigid ‘tree’ and the outer PtRh nanoparticles interconnects to form a spiral chain-like structure as the flexible ‘vine’. Owning to the limitation effect of biological template, both of nanoparticles and nanowires present a very small size of less than 2 nm, and thus leading to a large electrochemical active surface area of 79.20 m2/g. As a result, the as-prepared VT-PtRhNWs exhibit a much higher catalytic activity toward methanol oxidation compared with the commercial Pt/C catalyst, and also an improved CO tolerance, indicating a great potential as excellent electrocatalysts for fuel cells.

A new Pb(II)-based coordination polymer constructed by 5-((4-carboxyphenoxy)methyl)benzene-1,3-dioic acid and N-donor co-ligand: crystal structure and anti-glioma activity

Abstract A new lead(II)-organic architecture [Pb(HL) (dipyrido[3,2-a:2′,3′-c]phenazine (dppz))](H2O)2 (1) was successfully prepared under hydrothermal conditions by using organic-acid linker 5-((4-carboxyphenoxy)methyl) benzene-1,3-dioic acid (H3L) and N-donor chelating ligand dppz. The as-prepared complex was characterized by single-crystal X-ray structural analysis, powder X-ray diffraction (PXRD), and elemental analyses, which reveals that complex 1 shows a one-dimensional (1D) chain-like structure that is further extended to the 3D supermolecular network through H-bond and π-π interactions. Complex 1 was transformed to the nanoscale regime (ca. 190 nm) by mechanical grinding to yield the nano-1, maintaining its structure and crystallinity. Furthermore, the anticancer activity of the nano-1 toward the human neuroglioma cells (U251, U87, SHG-44, and A172) was evaluated via the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide) assay.

Electronic structure of the α-(BEDT-TTF)2I3 surface by photoelectron spectroscopy

We report anomalies observed in photoelectron spectroscopy measurements performed on α-(BEDT-TTF)2I3 crystals. In particular, above its metal-insulator transition temperature (T = 135 K), we observe the lack of a sharp Fermi edge in contradiction with the metallic transport properties exhibited by this quasi-bidimensional organic material. We interpret these unusual results as a signature of a one-dimensional electronic behavior confirmed by DFT band structure calculations. Using photoelectron spectroscopy we probe a Luttinger liquid with a large correlation parameter (α > 1) that we interpret to be caused by the chain-like electronic structure of α-(BEDT-TTF)2I3 surface doped by iodine defects. These new surface effects are inaccessible by bulk sensitive measurements of electronic transport techniques.

Optical fiber magnetic field sensor based on birefringence in liquid core optical waveguide

An optical fiber magnetic field sensor based on the birefringence of magnetic fluid is proposed by filling the magnetic fluid into a hollow-core waveguide. The birefringence characteristics of magnetic fluids with different concentrations tuned by magnetic field were investigated under different magnetic fields when the filled hollow-core waveguide is placed in a Sagnac loop. As the magnetic field increases, the internal chain-like structure of the magnetic fluid increases, resulting in changes in birefringence. The experimental results show that the device has a highly linear response to the variation of magnetic field intensity in the range of 0–300 Oe with the maximum sensitivity of 29.2 pm/Oe and resolution of 0.68 Oe. The proposed magnetic field sensor has such advantages as ease of fabrication, simple structure, low cost and it is expected to find potential applications in the magnetic field measurement with high accuracy, optical fiber gyroscopes, magneto-optic modulators and so on. Due to the external field tunability, the device also provides a promising technology for microfluidics research.

One-dimensionally extended oxygen vacancy states in perovskite oxides

We elucidate as-yet-unidentified spatially extended oxygen vacancy states in $\mathit{AB}{\mathrm{O}}_{3}$ perovskite oxides using first-principles calculations. When $B$ sites are occupied with ${d}^{0}$ transition-metal ions, charged oxygen vacancies are found to be long ranged in one direction because of charge transfer accompanied with atomic displacement along a chainlike structure. This finding offers two important results. First, it explains the reason why accurate calculations of oxygen vacancy formation energies necessitate very large supercells in ${d}^{0}$ perovskite and related oxides. It is remarkable especially for ${\mathrm{KNbO}}_{3}$ and ${\mathrm{WO}}_{3}$ on account of their anomalous Born effective charges. Second, such elongated vacancy states tend to show lower formation energies and thereby shallower donor levels. Our discussion is extendable to systems other than perovskites. Since the chainlike structure also appears in anatase ${\mathrm{TiO}}_{2}$ but not in its rutile counterpart, it could be a reason why the oxygen vacancy is a double shallow donor in the former while constructing a deep state in the latter.

Improved electrochemical performance of Li-S battery with carbon and polymer-modified cathode

In-situ precipitation method is used to synthesize nano-sulfur particles and acetylene black/sulfur (AB/S) binary composite. And then AB/S/polypyrrole (AB/S/PPy) ternary composite is prepared by chemical oxidation polymerization method. AB is an effective sulfur storage substrate, and its chain-like structure provides a good basis for the rapid transmission of lithium ions and electrons. PPy as an outermost coating layer not only alleviates volume expansion but also effectively inhibits the shuttle effect of lithium‑sulfur batteries (LSBs) during charge and discharge process. The experimental results demonstrate that the addition of carbon and the conductive polymer significantly contributes to improving the electrochemical performance of AB/S/PPy composite cathode. At a current density of 200 mA g−1, the initial specific discharge capacity of AB/S/PPy composite cathode is 1090 mAh g−1, and retains 577 mAh g−1 after 100 cycles. In comparison, AB/S composite and pure sulfur electrode exhibit poor electrochemical performance. Therefore, all the experimental results indicate that AB/S/PPy ternary composite is a potential cathode material for LSBs.

Numerical investigation on yielding phenomena of magnetorheological fluid flowing through microchannel governed by transverse magnetic field

To investigate the yielding phenomena during the start-up process of a magnetorheological fluid (MRF) flowing through a microchannel under a transverse uniform magnetic field, a three-dimensional and two-phase numerical simulation method is established based on the lattice Boltzmann method, united with the immersed boundary method and the discrete element method. Affected by the transverse uniform magnetic field, the randomly distributed magnetic nanoparticles (MPs) in MRF form some chains parallel to the direction of the magnetic field, and driven by the carrier fluid, the straight chains become curved due to the velocity gradient of the carrier fluid. It is revealed that the yielding process of MRF with water being the carrier fluid is essentially the deformation of the chains composed of MPs. The averaged shear force on the MPs at the ends of chains is taken to characterize the yielding status of an MP cluster, and there exists the maximum shear force during the deformation of chains. The Reynolds number has obvious influence on the characteristic shear force in the single chain, while for a multi-chain system, the chains are entangled with each other during the course of yielding and the characteristic shear force presents a complicated regularity. When the intensity of the magnetic field is relatively small, it has influence on the yielding force; once it is larger than a critical value, the yielding force remains constant. The yielding of MRF flow in a microchannel is a transient experience, and after yielding, the chain-like structure can maintain its integrity along with the channel flow.

Synthesis, Structure and In Vitro Anti-gastric Cancer Activity of Two New Mixed-Ligand Cu(II) and Cd(II)-Coordination Polymers

By using a strategy of introducing two organic ligands with different donor groups, two new Cu(II) and Cd(II) coordination polymers (CPs) [Cu3(OH)(pz)3(Hpz)(H2O)(ipa)](H2O)4 (1, Hpz = pyrazol, H2ipa = isophthalic acid) and [Cd(phen)(ndc)](H2O) (2, phen = 1,10-phenanthroline, H2ndc = 1,2-naphthalene dicarboxylic acid) are synthesized and characterized. The molecular structures of the as-prepared CPs were determined by the single crystal X-ray diffraction (SCXRD) studies and their phase purities have been confirmed via the power X-day diffraction analysis (PXRD). The Cu(II)-based complex 1 is composed of trinuclear Cu3(µ3-OH)(pz)3 clusters that extended by the ipa2− ligands into a 1D left-handed helical chain along the c axis. In complex 2, the ndc2− ligands connect with the binuclear Cd2 unit along the c axis to shape a 1D chain-like structure, which is further stacked into a 2D layered network via π–π stacking. The as-prepared two CPs transformed to the nanoscale regime by mechanical grinding to yield nano 1 and nano 2 with excellent water dispersibility, maintaining its crystallinity. In addition, the in vitro 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay were conducted on the gastric cancer cell line AGS with increasing concentrations of the two nanosized CPs, which reveal their promising anticancer activity.

Investigation of the impacts on magnetic permeability of MREs

As a new type of intelligent material with field-dependent properties, Magnetorheological Elastomer (MRE) is attracting more and more attention from domestic and foreign scholars. The MRE devices are expected to be used for vibration reduction in various systems. The requirements of MRE devices motivate the intensive investigations of MREs. The magnetic circuit design of MRE devices is necessary and the magnetic permeability is the premise to implement the design. In this paper, the permeability of MRE was calculated by finite element simulation and compared to the results of Maxwell-Garnet method. A simple chain-like structure of anisotropic MRE was modelled to study the influence of particle gap, particle content and external magnetic field on its permeability. Furthermore, the magnetic properties of MREs with same particle volume fraction and different curing field are tested by vibration sample magnetometer. The results are helpful in understanding the rheological mechanism of MREs, design and applications of MRE devices.

Two low-dimensional metal halides: ionothermal synthesis, photoluminescence, and nonlinear optical properties.

Two new organic-inorganic hybrid metal halides, formulated as (C7H13N2)2MnCl4 (1) and (C6H11N2)PbBr3 (2), were prepared by a two-component ionothermal approach using multifunctional ionic liquids as solvents, charge-balancing agents, and halide sources. Compound 1 has an ionic zero-dimensional structure showing bright green luminescence with a high quantum yield of up to 70.78%. Compound 2 has a chain-like structure with a large second harmonic generation efficiency which is approximately 8× that of KH2PO4.