Synthesis and studies of trisubstituted biphthalonitrile/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> magnetic hybrid microspheres

New trisubstituted biphthalonitrile/magnetite (TSB/Fe₃O₄) magnetic hybrid microspheres were synthesized from TSB and FeCl₃ · 6H₂O using the method of one-stage thermal temperature crystallization of solvents. The morphology and structure of magnetic hybrid microspheres were inspected using a scanning electron microscope, IR Fourier spectroscopy, and X-ray diffraction. It was found that the grown TSB/Fe₃O₄ magnetic hybrid microspheres represent spherical particles with an average size of ~137 nm and a small size spread. The size and size distribution of magnetic hybrid microspheres can be controlled by a small change in the ratio of TSB and Fe³⁺ ion contents in the microsphere. TSB/Fe₃O₄ hybrid microspheres exhibit a rather high saturation magnetization (58.16 emu g^–1) and new microwave electromagnetic properties, i.e., lower (in comparison with published) dielectric losses at low frequencies; magnetic losses are increased obviously due to an increase in the TSB content. Furthermore, it is detected that magnetic hybrid microspheres absorb microwaves, and strong reflection losses in a wide frequency range are established. The effective reflection loss of–31 dB is obtained in the microwave range from 2 to 16 GHz due to TSB content variations. Wide absorption properties of microwaves along with regular spherical shape and excellent magnetic properties offer wide opportunities for various applications of TSB/Fe₃O₄ magnetic hybrid microspheres as functional materials.     

EDTA辅助水热合成FeS2/NiSe2复合纳米晶及其薄膜光电性质

以EDTA为螯合剂，加入MX2结构化合物NiSe₂作为晶种，水热合成了FeS₂纳米晶. x射线衍射分析结果表明产物为单一相黄铁矿型FeS₂（pyrite）,平均粒径约40—50nm.丝网印刷成膜且高温退火后FeS₂薄膜光学直接带隙变宽.随晶种量的增加，吸收边在紫外—可见光谱区红移、方块电阻升高、霍尔迁移率上升和载流子浓度下降，实现了n型掺杂.并且对FeS₂的形成机理进行了讨论. 关键词： 2纳米晶')" href="#">FeS₂纳米晶 水热 诱导结晶 直接禁带宽度      

Photoacoustic characterization of natural mineral pyrite (FeS<Subscript>2</Subscript>)

A single p-type crystal of the mineral, pyrite (FeS₂) was characterized photoacoustically using the transmission detection configuration. Photoacoustic (PA) amplitude and phase spectra were measured using a specially constructed PA cell. The PA signals of different sample thicknesses were measured using an experimental setup with a semiconductor red laser (80 mW) as the optical source. The obtained amplitude and phase spectra for different thicknesses were numerically analyzed enabling determination of thermal diffusivity, mobility of minority free carriers and other parameters characteristic for this material.     

Transformations of Pyrite and Pyrrhotite in Supercritical Water

The interaction of pyrite (FeS₂) with water at the uniform heating (1.5 K/min) of the reaction mixture to 923 K and its subsequent cooling (about 3 K/min) to 423 K is studied. The reaction products are analyzed using the methods of mass-spectrometry, elemental and X-ray diffraction analyses, and scanning electron microscopy. It is established that H₂S, SO₂, and rhombic and hexagonal pyrrhotite (FeS) are formed while heating, and the subsequent cooling of the reaction system gives rise to the formation of H₂S, H₂, cubic pyrite, and monoclinic pyrrhotite exhibiting ferromagnetic properties. It is shown that the transformations FeS₂ → FeS → FeS _x (1 < x ≤ 2) are accompanied by changes in the morphology and size of particles.     

Preparation of RE<Subscript>2</Subscript>O<Subscript>2</Subscript>SO<Subscript>4</Subscript> (RE=La,Pr-Lu) microspheres from rare-earth-based infinite coordination polymers

Rare-earth-based infinite coordination polymer (RE-ICP) spheres with diameters ranging from 50 nm to 2 μm have been prepared using meso-2,3-dimercaptosuccinic acid (DMSA) as ligand under hydrothermal conditions. RE₂O₂SO₄ microspheres with similar morphology were obtained by calcining the corresponding RE-ICP spheres. However, as for Ce-ICP and Sc-ICP, CeO₂ and Sc₂O₃ were obtained. The products were characterized using X-ray diffraction, scanning electron microscopy, thermogravimetric analysis, infrared spectroscopy, laser Raman spectrometry, and energy-dispersive X-ray spectrum. Elemental analysis and inductive coupled plasma atomic emission spectrometer were adopted to study the composition of the Eu-ICP. To explore their potential applications, several samples of the products were selected and their properties were investigated. The Eu-ICP and Eu₂O₂SO₄ microspheres give strong red emissions when excited with a 394-nm ultraviolet light. Furthermore, the Eu-ICP displays a high selectivity for Fe(III). The obtained CeO₂ has a strong absorption in the UV region and the Gd₂O₂SO₄ microspheres show paramagnetic behavior.

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Graphical abstract A series of RE₂O₂SO₄ microspheres were prepared using a coordination polymer precursor method.

     

Physicochemical properties of core/shell structured pyrite FeS2/anatase TiO2 composites and their photocatalytic hydrogen production performances

A new photocatalytic system using anatase TiO₂ loaded onto pyrite FeS₂ (FeS₂/TiO₂) was developed to enhance the production of hydrogen. The FeS₂ (3.0, 5.0, 10.0, and 15.0 wt-%)/TiO₂ particles in SEM photos showed a core/shell structure composed of pyrite FeS₂ with a grape-like morphology of length of ～1.0 μm and anatase TiO₂ of diameter <50 nm. The evolution of H₂ by methanol/water (1:1) photo splitting over FeS₂/TiO₂ in a liquid system was enhanced as compared with that obtained using pure TiO₂ and FeS₂. In particular, 9.8 mmol of H₂ gas was produced in 10 h when 0.5 g of a 10.0 wt-% FeS₂/TiO₂ core/shell composite was used. Hydrogen production was increased by adding KOH electrolyte to 11.2 mmol. On the basis of cyclic voltammetry (CV) and UV–visible spectra results, this photoactivity of the FeS₂/TiO₂ composite was attributed to a shorter band gap than those of pure TiO₂ and FeS₂.     

Hydrothermal synthesis of FeS2 for lithium batteries

Nanocrystalline FeS₂ cathode material of lithium cell was synthesized from cheap materials of FeSO₄, Na₂S₂O₃, and sulfur by a hydrothermal process. The scanning electron microscopy analysis showed the obtained material was nano-sized, about 500 nm. The X-ray powder diffraction analysis showed that the synthetic FeS₂ material had two phases of the crystalline structure, pyrite and marcasite. The phase of marcasite seems to have no negative effect on the electrochemical performance of the material. The synthetic FeS₂ showed a significant improvement of electrochemical performance for Li/FeS₂ cells.     

Urea-assisted solvothermal synthesis of monodisperse multiporous hierarchical micro/nanostructured ZnCo<Subscript>2</Subscript>O<Subscript>4</Subscript> microspheres and their lithium storage properties

High-quality monodisperse multiporous hierarchical micro/nanostructured ZnCo₂O₄ microspheres have been fabricated by calcinating the Zn_1/3Co_2/3CO₃ precursor prepared by urea-assisted solvothermal method. The as-prepared products are characterized by X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), and Brunauer-Emmett-Teller (BET) measurement to study the crystal phase and morphology. When tested as anode material for lithium ion batteries, the multiporous ZnCo₂O₄ microspheres exhibit an initial discharge capacity of 1,369 mAh g^?1 (3,244.5 F cm^?3) and retain stable capacity of 800 mAh g^?1 (1,896 F cm^?3) after 30 cycles. It should be noted that the good electrochemical performances can be attributed to the porous structure composed of interconnected nanoscale particles, which can promote electrolyte diffusion and reduce volume change during discharge/charge processes. More importantly, this ZnCo₂O₄ 3D hierarchical structures provide a large number of active surface position for Li⁺ diffusion, which may contribute to the improved electrochemical performance towards lithium storage.     

An efficient process to fabricate spherical hierarchical LiFePO<Subscript>4</Subscript>/C cathode composites with controllable coating thickness

Hierarchical lithium iron phosphate/carbon (LiFePO₄/C) microspheres were fabricated successfully using a facile spray drying-assisted coprecipitation method. A relatively short calcination time and a relatively low calcination temperature were adopted to prepare the hierarchical LiFePO₄/C microspheres. The hierarchical microspheres consisted of nanoparticles with a uniform coating of amorphous carbon. The thickness of the carbon layer was controlled by the addition of glucose. The hierarchical LiFePO₄/C microspheres exhibited a high tap density and a large specific surface area. The electrochemical properties of the sample were investigated. The sample exhibited a better rate capability and a better cyclability than the coral-like LiFePO₄/C cathode material, and these were ascribed to the highly uniform carbon coating and the self-assembled nanoparticles.     

Synthesis,characterization, and photocatalytic properties of Ni<Subscript>12</Subscript>P<Subscript>5</Subscript> hollow microspheres

Ni₁₂P₅ hollow microspheres were prepared by a simple mixed cetyltrimethyl ammonium bromide/sodium dodecyl sulfate surfactant-assisted hydrothermal route. The as-prepared Ni₁₂P₅ microstructures were characterized by X-ray powder diffraction (XRD), field emission scanning electron microscopy (FE-SEM), and transmission electron microscopy (TEM). It was interesting to find that cetyltrimethyl ammonium bromide/sodium dodecyl sulfate could form a micro-reactor by the mixed micelles in the aqueous solution, which served as a soft template for Ni₁₂P₅ hollow microspheres with a diameter of 2~6 μm. Moreover, the as-prepared Ni₁₂P₅ hollow microspheres exhibited a good photocatalytic degradation activity for some organic dyes (such as Rhodamine B, Methylene Blue, Pyronine B, and Safranine T), and the degradation ratio could achieve more than 80%.     

Fabrication of urchin-like NiCo<Subscript>2</Subscript>O<Subscript>4</Subscript> microspheres assembled by using SDS as soft template for anode materials of Lithium-ion batteries

In this paper, the urchin-like NiCo₂O₄ microspheres assembled by using sodium dodecyl sulfate (SDS) as soft template are successfully fabricated by a facile procedure including microemulsion-solvothermal reaction and subsequent calcination at 400 °C for 4 h. The structure and morphology of synthesized NiCo₂O₄ particles are investigated by X-ray diffraction (XRD) and scanning electron microscopy (SEM). It has been clearly revealed that the prepared three-dimensional urchin-like NiCo₂O₄ microspheres are constituted by one-dimension nanowires. As it is applied to anode for lithium-ion batteries (LIBs), the initial coulombic efficiency is up to 75.7%, and the specific reversible capacity retains up to 1034.2 mAh/g even after 40 cycles at a current density of 100 mA/g. Furthermore, as the current density gradually increases to 800 mA/g, it still delivers the reversible capacity of 895.4 mAh/g. The high reversible specific capacity, perfect cyclability, and rate performance are attributed to the unique urchin-like NiCo₂O₄ microspheres, which can alleviate the volume expansion and shorten the diffusion path of ions and electrons during lithiation/delithiation process. The self-standing urchin-like NiCo₂O₄ microspheres may be a very promising candidate in place of the commercial graphite-based anode materials for high-performance LIBs.     

Gas sensing properties of MoO<Subscript>3</Subscript> nanoparticles synthesized by solvothermal method

MoO₃ nanoparticles were prepared by thermally oxidizing the MoO₂ nano-crystallites synthesized by solvothermal reaction, and their gas sensing properties were investigated. Ethanol and water mixed solvents were used in the solvothermal synthesis, and it was observed that the phase, size, and morphology of the products were strongly dependent on the composition of solvents. Well-crystallized and spherical MoO₂ nano-crystallites (~20 nm) were obtained in the mixed solvent (water:ethanol = 40:10 in vol), and subsequent heat treatment at 450 °C produced the well-separated, slightly elongated MoO₃ nano-particles of ~100 nm. The nano-particle MoO₃ gas sensor responded to both oxidizing and reducing gases, but it exhibited the extremely high gas response toward H₂S with a short response time (<10 s). In particular, the magnitude of gas response of nano-particle MoO₃ gas sensor was about 10 times higher than that of micron-sized commercial MoO₃ powder sensor at 20 ppm H₂S.     

Carbon@SnS<Subscript>2</Subscript> core-shell microspheres for lithium-ion battery anode materials

A novel unique C@SnS₂ core-shell structure composites consisting of well-dispersity carbon microspheres and ultrathin tin disulfide nanosheets were successfully synthesized for the first time through a simple solvothermal method. The thin SnS₂ nanosheets grew onto the carbon microspheres surfaces perpendicularly and formed the close-knit porous structure. When it was used as anode materials for lithium-ion batteries, the hybrid C@SnS₂ core-shell structure composites showed a remarkable electrochemical property than pure SnS₂ nanosheets. Typically, the hybrid composites with SnS₂ nanosheet shells and carbon microsphere’s core exhibited an excellent initial discharge capacity of 1611.6 mAh/g. Moreover, the hybrid composites exhibited capacities of 474.8–691.6 mAh/g at 100 mA/g over 50 battery cycles, while the pure SnS₂ could deliver capacities of 243–517.6 mAh/g in the tests. The results indicated that the improvement of lithium storage performance of the core-shell structure C@SnS₂ anode materials in terms of rate capability and cycling reversibility owing to the introduction of the smooth carbon microspheres and special designing of core-shell structure.     

Ab initio study of phonon dispersion and thermodynamic properties of pure and doped pyrites

Pyrites (FeS₂) are solid minerals that are found abundantly in Nigeria and are easy to prepare in laboratories. In this work, FeS₂ is studied extensively in its pure state as well as when iron is substitutionally doped with zinc and calcium at concentrations of 0, 0.25, 0.5, 0.75 and 1. Using density functional theory, the eectronic, dynamic and thermodynamic properties were calculated. The results revealed that the lattice parameters and bulk modulus increases with increasing concentration and the obtained values are in agreement with available experimental and theoretical values. Though pyrite, when doped with zinc, obeys Vegard’s law, doping with calcium revealed pronounced deviation from this law. The calculated band structures showed that FeS₂ has an indirect band gap whose size decreases after introducing zinc while doping with calcium increases the band gap. The phonon dispersion of the end members FeS₂ and ZnS₂ indicate that the systems are dynamically stable while CaS₂ is dynamically unstate. Also, the thermodynamic properties of the pure and doped pyrites were calculated and the ranges of temperature at which the lattice and electronic degrees of freedom contribute to the specific heat capacity are presented.     

Mo-doped V<Subscript>2</Subscript>O<Subscript>5</Subscript> hierarchical nanorod/nanoparticle core/shell porous microspheres with improved performance for cathode of lithium-ion battery

Mo-doped V₂O₅ hierarchical nanorod/nanoparticle core/shell porous microspheres (MVHPMs) were prepared via a simple hydrothermal approach using ammonium metavanadate and ammonium molybdate as precursors followed by a thermal annealing process. The samples were characterized by XRD, SEM, TEM, EDS, and XPS carefully; it confirmed that porous microspheres with uniform Mo doping in the V₂O₅ matrix were obtained, and it contains an inner core self-assembled with 1D nanorods and outer shell consisting of nanoparticles. A plausible growth mechanism of Mo-doped V₂O₅ (Mo-V₂O₅) porous microspheres is suggested. The unique microstructure made the Mo-V₂O₅ hierarchical microspheres a good cathode material for Li-ion battery. The results indicate the synthesized Mo-V₂O₅ hierarchical microspheres exhibit well-improved electrochemical performance compared to the undoped samples. It delivers a high initial reversible capacity of 282 mAh g^?1 at 0.2 C, 208 mAh g^?1 at 2 C, and 111 mAh g^?1 at 10 C, and it also exhibits good cycling stabilities; a capacity of 144 mAh g^?1 is obtained after 200 cycles at 6 C with a capacity retention of >?82%, which is much high than that of pure V₂O₅ (95 mAh g^?1 with a capacity retention of 72%).

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Graphical Abstract Mo-doped V₂O₅ hierarchical porous microspheres with improved LIB performance

     

Magnetotransport properties of nano-constriction array in La<Subscript>0.67</Subscript>Sr<Subscript>0.33</Subscript>MnO<Subscript>3</Subscript> film

Nano-constriction array in La_0.67Sr_0.33MnO₃ film was fabricated by using ion beam etching masked by a monolayer of packed and ordered array of SiO₂ microspheres. Nano-constrictions of around 50 nm in width were fabricated. The low field magnetoresistance (LFMR) exhibited in the samples were observed to be current dependent and the I-V characteristics of the film were found to be nonlinear. These observations were attributed to the co-existence of the ferromagnetic regions and the nano-constricted region of weakened ferromagnetic coupling where Mn³⁺-O-Mn⁴⁺ bond were distorted due to the ion beam bombardment. The spin polarized bias current would strengthen local ferromagnetic coupling when passing through this nano-constricted regions. This current effect is relatively large comparing to the external magnetic field to the drop of resistance.     

Force field of FeS2 with pyrite structure at zero wave vector

Published experimental frequencies are used to calculate force field and effective charge of FeS₂ with pyrite structure. The values obtained are discussed. Some preliminary calculations on MnS₂ are reported.     

Mössbauer spectroscopic study on chemical changes of iron compounds with the aid of sulfate-reducing bacteria

⁵⁷Fe Mössbauer spectra were measured of reaction products formed during an incubation experiment with sulfate-reducing bacteria, which were isolated from estuarine sediments of the Tama River in Tokyo. The spectrum of the product incubated for several days showed some overlapping sextets. This product had a different chemical form from amorphous iron monosulfide produced by inorganic reaction between ferrous and sulfide ions. It was estimated that the structure of nearest neighbor of iron in this product was similar to that of pyrrhotite (Fe_1?x S). After several months of incubation, other singlet and doublet appeared successively on the spectrum, corresponding to mackinawite (FeS_1?x ) and new sulfide, respectively. Both values of isomer shift and quadrupole splitting of new sulfide increased with increasing incubation time and approached those of pyrite (FeS₂). Extended X-ray absorption fine structure (EXAFS) showed that iron atoms were coordinated by sulfur in the incubation product.     

Fabrication and characterization of visible light-driven In<Subscript>2.77</Subscript>S<Subscript>4</Subscript>/In(OH)<Subscript>3</Subscript> composite photocatalysts with excellent redox performance

The In_2.77S₄ microspheres had been firstly fabricated by using polyethylene glycol (PEG) as the morphological modifier and then used to hybridize with In(OH)₃ nanocubes by a simply depositional method. The structure, optical properties, morphology, chemical compositions, and charge carrier behaviors of the as-prepared In_2.77S₄/In(OH)₃ composites were characterized, respectively. The methyl orange, tetracycline, rhodamine B, and Cr(VI) dilute solution were selected to evaluate their photocatalytic activities. Experimental results showed that In(OH)₃ nanocubes could improve the photocatalytic activity and recyclability of the In_2.77S₄ microspheres under the visible light irradiation. With the usage of In(OH)₃ increased, the photocatalytic efficiency of the hybrids was firstly increased and then decreased. When the mass ratios of In_2.77S₄ to In(OH)₃ were 6:2, it reached the maximum of 100% in 15 min for methyl orange, obviously higher than 67.4% of In_2.77S₄ and 1.1% of In(OH)₃. Meanwhile, it could also oxidize 85.6% of tetracycline in 20 min, 97.8% of rhodamine B in 7.5 min, and reduce 92.9% of Cr(VI) in 30 min under the visible light irradiation. Moreover, it could still degrade 91.7% of methyl orange solution after 3 cycles, which was much higher than 40.7% of In_2.77S₄ microspheres. In addition, the possible mechanism of enhancing photocatalytic properties was proposed.     

Study of the compressibility of FeSi,MnSi, and CoS<Subscript>2</Subscript> transition-metal compounds at high pressures

Silicides and sulfides of transition metals attract great attention of researchers because of a wide spectrum of interesting magnetic, electronic, and optical properties. The crystal structure of FeSi, MnSi, and CoSi silicides is P2₁3(B20), whereas FeS₂, CoS₂, and MnS₂ sulfides have a structure of pyrite Pa3. Despite the great interest in these systems and the cubic symmetry of crystals, the structure and compressibility of these compounds at high pressures are still insufficiently studied. There is a significant spread (more than a factor of two!) in the bulk modulus and its pressure derivative for a single compound. Most studies were performed under nonhydrostatic conditions. In this work, the compressibility of FeSi and MnSi silicides (at pressures up to 35 GPa) and CoS₂ sulfide (up to 22 GPa) has been studied by the X-ray diffraction method in a diamond anvil cell with the use of helium as the softest pressure-transmitting medium. The values obtained for the bulk modulus and its derivative—B = 178 ±3 GPa and B_p = 5.6 ± 0.5 for FeSi, B = 167 ± 3 GPa and B_p^' = 4.6 ± 0.5 for MnSi, and B = 94 ± 2 GPa and B_p^' = 6.9 ± 0.5 for CoS₂—can be considered as the most reliable and can be used to test numerous theoretical models. The results for the compressibility of FeSi are important for the verification of models of the Earth’s core.