ZnIn_2S_4的制备及其表面活性剂辅助的形貌控制生长

采用湿化学合成路线以巯基乙酸为包覆剂,水为溶剂制备了六方相ZnIn2S4。应用能谱分析(EDS)、X射线衍射(XRD)、透射电镜(TEM)、扫描电镜(SEM)和紫外-可见光谱对产物的组成、结构、形貌和光学性质进行了表征。结果表明,所得到的ZnIn2S4具有层状形貌。这些层状物是由ZnIn2S4纳米粒子前驱体在热处理过程中聚集生长而成的。另外,以ZnIn2S4纳米粒子前驱体为起始原料,借助表面活性剂的导向作用在固/液界面成功地实现了ZnIn2S4的形貌控制生长,得到了具有棒状、棒簇状、管簇状形貌的ZnIn2S4。根据实验结果,初步讨论了可能的表面活性剂辅助的ZnIn2S4形貌控制生长的机制。     

Spectroscopic Characterization of an Eight‐Iron Nitrogenase Cofactor Precursor that Lacks the “9th Sulfur”

Nitrogenases catalyze the reduction of N₂ to NH₄⁺ at its cofactor site. Designated the M‐cluster, this [MoFe₇S₉C(R‐homocitrate)] cofactor is synthesized via the transformation of a [Fe₄S₄] cluster pair into an [Fe₈S₉C] precursor (designated the L‐cluster) prior to insertion of Mo and homocitrate. We report the characterization of an eight‐iron cofactor precursor (designated the L*‐cluster), which is proposed to have the composition [Fe₈S₈C] and lack the “9^th sulfur” in the belt region of the L‐cluster. Our X‐ray absorption and electron spin echo envelope modulation (ESEEM) analyses strongly suggest that the L*‐cluster represents a structural homologue to the l ‐cluster except for the missing belt sulfur. The absence of a belt sulfur from the L*‐cluster may prove beneficial for labeling the catalytically important belt region, which could in turn facilitate investigations into the reaction mechanism of nitrogenases.     

单分散Fe3O4纳米颗粒的控制合成和表征

以十八烯为溶剂、乙酰丙酮铁为铁源,并在油酸、油胺的辅助作用下,通过热分解法成功合成了单分散Fe3O4纳米颗粒。讨论了实验参数如反应温度、表面活性剂的量和种类、溶剂、油酸、油胺对单分散Fe3O4纳米颗粒的尺寸及形貌的影响。利用X射线衍射（XRD）、透射电子显微镜（TEM）、选区电子衍射（SAED）和高分辨透射电子显微镜（HRTEM）对所得产物的物相、结构、尺寸和形貌进行了表征分析。通过振动样品磁强计（VSM）表征产物磁性能,表明在室温下,Fe3O4纳米颗粒的饱和磁化强度（Ms）和矫顽力（Hc）分别为74.0 emu/g,72.6 Oe。     

An unexpected P-cluster like intermediate en route to the nitrogenase FeMo-co

The nitrogenase MoFe protein contains two different FeS centers, the P-cluster and the iron–molybdenum cofactor (FeMo-co). The former is a [Fe₈S₇] center responsible for conveying electrons to the latter, a [MoFe₇S₉C-(R)-homocitrate] species, where N₂ reduction takes place. NifB is arguably the key enzyme in FeMo-co assembly as it catalyzes the fusion of two [Fe₄S₄] clusters and the insertion of carbide and sulfide ions to build NifB-co, a [Fe₈S₉C] precursor to FeMo-co. Recently, two crystal structures of NifB proteins were reported, one containing two out of three [Fe₄S₄] clusters coordinated by the protein which is likely to correspond to an early stage of the reaction mechanism. The other one was fully complemented with the three [Fe₄S₄] clusters (RS, K1 and K2), but was obtained at lower resolution and a satisfactory model was not obtained. Here we report improved processing of this crystallographic data. At odds with what was previously reported, this structure contains a unique [Fe₈S₈] cluster, likely to be a NifB-co precursor resulting from the fusion of K1- and K2-clusters. Strikingly, this new [Fe₈S₈] cluster has both a structure and coordination sphere geometry reminiscent of the fully reduced P-cluster (P^N-state) with an additional μ²-bridging sulfide ion pointing toward the RS cluster. Comparison of available NifB structures further unveils the plasticity of this protein and suggests how ligand reorganization would accommodate cluster loading and fusion in the time-course of NifB-co synthesis.

The K-cluster of NifB as a key intermediate in the synthesis of the nitrogenase active site supports [Fe₄S₄] cluster fusion occurs before carbide and sulfide insertion and displays ligand spatial arrangement reminiscent to that of the P-cluster.     

Synthesis and characterization of CuInS<Subscript>2</Subscript> nanoflowers

Uniform crystalline CuInS₂ nanoflowers with an average size of 25 nm were synthesized by a hot-injection strategy using CuAc, In(Ac)₃ and sulfur powder as precursors and oleylamine as both the solvent and ligand. Various methods including X-ray diffraction, transmission electron microscopy and absorption spectroscopy were used to characterize CuInS₂ nanoflowers. Control experiments indicated that CuInS₂ nanoflowers were formed through 3D attachment of forming primary nanodots. The obtained CuInS₂ nanoflowers are promising for low-cost, high efficiency solar cells due to several advantages such as the simplicity of synthesis, size and morphology uniformity, stability of dispersion and large surface area for charge separation.     

Preparation and Mo¨ssbauer studies of (FeyNb1−y)1+xS2 compounds

The phase relations for iron niobium sulfides (Fe_yNb_1?y)_1+xS₂ have been examined by varying the partial pressure of sulfur at 950°C. While niobium is difficult to dissolve in iron sulfide, iron dissolves in niobium sulfide up to about 35% of the total metal sites. Iron niobium sulfide has the layered hexagonal type structure (2s-Nb_1+xS₂) with change in the lattice parameters depending on both the value of x and the amount of the iron dissolved. The Mo¨ssbauer spectra of sulfides with three different Fe/Nb ratios, 1/9(y =1/10), 1/4(y =1/5), and 1/2(y =1/3) were taken at 77 and 295 K. Each spectrum is composed of a quadrupole doublet which can be attributed to the Fe²⁺ ions in high spin state. The quadrupole splitting at 295 K decreases markedly with decrease in x which is related to change of the lattice parameters. Fe atoms cannot enter at random into all metal sites, and prefer to intercalate in the sites of partially filled layers. Possible models for the cation distribution in each metal layer are discussed.     

Low temperature synthesis of cubic phase zinc sulfide quantum dots

In this study, we report on a new method for the synthesis of ZnS quantum dots (QDs). The synthesis was carried out at low temperature by a chemical reaction between zinc ions and freshly reduced sulfide ions in ethanol as reaction medium. Zinc chloride and elemental sulfur were used as zinc and sulfur sources, respectively and hydrazine hydrate was used as a strong reducing agent to convert elemental sulfur (S₈) into highly reactive sulfide ions (S²⁻) which react spontaneously with zinc ions. This facile, less toxic, inexpensive route has a high yield for the synthesis of high quality metal sulfide QDs. Transmission electron microscopy (TEM) image analysis and selected area electron diffraction (SAED) reveal that ZnS QDs are less than 3 nm in diameter and are of cubic crystalline phase. The UV-Vis absorption spectrum shows an absorption peak at 253 nm corresponding to a band gap of 4.9 eV, which is high when compared to the bulk value of 3.68 eV revealing strong quantum confinement. PL emission transitions are observed at 314 nm and 439 nm and related to point defects in ZnS QDs.     

Synthesis,Structure, and Molecular Recognition of S6‐ and (SO2)6‐Corona[6](het)arenes: Control of Macrocyclic Conformation and Properties by the Oxidation State of the Bridging Heteroatoms

We report herein the synthesis, structure, and molecular recognition of S₆‐ and (SO₂)₆‐corona[6](het)arenes, and demonstrate a unique and efficient strategy of regulating macrocyclic conformation and properties by adjusting the oxidation state of the heteroatom linkages. The one‐pot nucleophilic aromatic substitution reaction of 1,4‐benzenedithiol derivatives, biphenyl‐4,4′‐dithiol and 9,9‐dipropyl‐9H‐fluorene‐2,7‐dithiol with 3,6‐dichlorotetrazine afforded S₆‐corona[3]arene[3]tetrazines. These compounds underwent inverse‐electron‐demand Diels–Alder reaction with enamines and norbornadiene to produce S₆‐corona[3]arene[3]pyridazines. Facile oxidation of sulfide linkages yielded (SO₂)₆‐corona[3]arene[3]pyridazines. All corona[6](het)arenes adopted generally hexagonal macrocyclic ring structures; however, their electronic properties and conformation could be fine‐tuned by altering the oxidation state of the sulfur linkages. Whereas (SO₂)₆‐corona[3]arene[3]pyridazines were electron‐deficient, S₆‐corona[3]arene[3]pyridazines acted as electron‐rich macrocyclic hosts that recognized various organic cations in both aqueous and organic solutions.     

A small biomolecule-assisted synthesis of iron sulfide nanostructures and magnetic properties

In this article, a facile l-cysteine-assisted solvothermal method is described, which is about the large-scale synthesis of Fe_0.985S novel nanostructures in a mixed solution composed of ethylenediamine (EN) and distilled water. By varying process parameters, such as the molar ratio of Fe³⁺-to-l-cysteine (reactants), the volume ratio of water to ethylenediamine, and the reaction temperature, different kinds of architectural structures can be controllably synthesized in large quantities. At the same time, a reasonable mechanism for the growth of iron sulfide structures has been proposed. The as-prepared iron sulfide products were characterized using diverse techniques including X-ray powder diffraction (XRD), field-emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM), high-resolution TEM, superconducting quantum interface device (SQUID) magnetometer (Quantum Design MPMS XL).     

Direct electrochemistry and electrocatalysis of cytochrome <Emphasis Type="Italic">c</Emphasis> based on dandelion-like Bi<Subscript>2</Subscript>S<Subscript>3</Subscript> nanoflowers

The direct electrochemistry and electrocatalysis of cytochrome c (Cyt c) based on dandelion-like bismuth sulfide (d-Bi₂S₃) nanoflowers have been developed. The morphologies and composition of the d-Bi₂S₃ were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and energy dispersive X-ray spectroscopy (EDS). Then, the electrochemical behaviors of Cyt c immobilized within the d-Bi₂S₃/chitosan film and its electrocatalytic ability toward hydrogen peroxide (H₂O₂) reduction were investigated by cyclic voltammetry. The electron transfer rate constant was estimated to be 13.1 s^?1, suggesting that a fast direct electron transfer was realized. The prepared Cyt c/d-Bi₂S₃/chitosan nanobiocomposite-modified electrode possessed excellent electrocatalytic ability toward H₂O₂ reduction that showed linearity in the range from 0.5 μM to 1.56 mM with a correlation coefficient of 0.9993. The detection limit was 0.2 μM on signal-to-noise ratio of 3. In addition, the d-Bi₂S₃ nanoflowers may be also applied to direct electron transfer of other redox proteins.     

Microwave-assisted synthesis and characterization of hexagonal Fe3O4 nanoplates

Hexagonal magnetite (Fe₃O₄) nanoplates with an average edge length of 80 nm were successfully prepared in large quantities by a facile microwave-assisted route. The influences of experiment parameters such as reaction time, microwave power, and concentration of NaOH and other additive agents on the morphology and size of final products were investigated in detail. Phase structure, morphology and magnetic properties of products were carefully studied by X-ray diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), high-resolution transmission electron microscope (HRTEM), and vibrating sample magnetometer (VSM). Magnetic studies revealed that hexagonal Fe₃O₄ nanoplates have low saturation magnetization of 36.4 emu/g and the possible reason has been proposed.     

新型磁性荧光Fe3O4-CdSe纳米复合材料的制备

以1-十八烯作为高沸点溶剂, 在磁性粒子表面沉积量子点获得新型的磁性荧光Fe₃O₄-CdSe 纳米异质结构. 首先以乙酰丙酮铁(Fe(acac)₃)为前驱体, 二苯醚为溶剂, 油酸为表面活性剂和油胺(OAm)为表面活性剂兼还原剂, 通过溶剂热法制备单分散性的Fe₃O₄ 纳米粒子. 然后以1-十八烯为高沸点溶剂, CdO 为镉源,TOP-Se为硒源, 十六胺为表面活性剂以及硬脂酸为生长促进剂和成核剂制备得到新型的Fe₃O₄-CdSe纳米异质结构. 通过透射电镜(TEM), 傅里叶变换红外(FTIR)光谱, X射线衍射(XRD)谱, X射线光电子能谱(XPS)分析仪, 振动样品磁强计(VSM), 紫外-可见(UV-Vis)光谱和光致发光(PL)等手段对Fe₃O₄-CdSe 纳米复合材料的结构和性能进行表征. 结果表明, CdSe纳米粒子成功地吸附在Fe₃O₄纳米粒子表面, 并沿着c轴生长, 形成了宽3.6 nm, 长分别为14.5 和32.5 nm的新型枣核状和钉子状的异质结构体. 这种新型的Fe₃O₄-CdSe纳米复合材料是由磁铁矿Fe₃O₄和六方形的CdSe棒状结构组成, 具有较好的荧光性能和超顺磁性. 随着CdSe棒长度的增加, 荧光吸收峰向长波方向移动. Fe₃O₄纳米粒子, 枣核状和钉子状的Fe₃O₄-CdSe纳米复合材料的饱和磁化强度分别是57.80, 40.76和31.10 emu·g^-1.     

Useful and accessible organometallic precursors for preparation of zinc sulfide and indium sulfide thin films via solution pyrolysis (printing) method

Polycrystalline β-zinc sulfide thin films were prepared by solution pyrolysis of an ethylzinc isopropylthiolate–zinc bis(dibutyldithiocarbamate) combined precursor (EtZnSiPr–Zn(S₂CNnBu₂)₂) in chloroform solution on glass or silicon(111) substrates at 300°C. Homogeneous but amorphous indium sulfide thin films were obtained from butylindium bis(isopropylthiolate) (nBuInSiPr₂) in P-xylene on these substrates at 300°C similarly. The sulfide thin films obtained were characterized by means of X-ray photoelectron spectroscopy (XPS), X-ray fluorescence Microanalysis, scanning electron microscopy (SEM) and optical band gap measurements.     

3D Porous Carbon Framework Stabilized Ultra‐Uniform Nano γ‐Fe2O3: A Useful Catalyst System

We present a novel strategy for the scalable fabrication of γ‐Fe₂O₃@3DPCF, a three‐dimensional porous carbon framework (PCF) anchored ultra‐uniform and ultra‐stable γ‐Fe₂O₃ nanocatalyst. The γ‐Fe₂O₃@3DPCF nanocomposites were facilely prepared with the following route: condensation of iron(III) acetylacetonate with acetylacetonate at room temperature to form the polymer precursor (PPr), which was carbonized subsequently at 800 °C. The homogeneous aldol condensation offered an ultra‐uniform distribution of iron, so that the γ‐Fe₂O₃ nanoparticles (NPs) were uniformly distributed in the 3D carbon architecture with the average size of approximate 20 nm. The Fe₂O₃ NPs were capped with carbon, so that the iron oxide maintained its γ‐phase instead of the more stable α‐phase. The nanocomposite was an excellent catalyst for the reduction of nitroarene; it gave >99 % conversion and 100 % selectivity for the reduction of nitroarenes to the corresponding anilines at 100 °C. The fabrication of the γ‐Fe₂O₃@3DPCF nanocatalyst represents a green and scalable method for the synthesis of novel carbon‐based metal oxide nanostructures.     

Preparation of iron oxides using ammonium iron citrate precursor: Thin films and nanoparticles

Ammonium iron citrate (C₆H₈O₇·nFe·nH₃N) was used as a precursor for preparing both iron-oxide thin films and nanoparticles. Thin films of iron oxides were fabricated on silicon (111) substrate using a successive-ionic-layer-adsorption-and-reaction (SILAR) method and subsequent hydrothermal or furnace annealing. Atomic force microscopy (AFM) images of the iron-oxide films obtained under various annealing conditions show the changes of the micro-scale surface structures and the magnetic properties. Homogenous Fe₃O₄ nanoparticles around 4 nm in diameter were synthesized by hydrothermal reduction method at low temperature and investigated using transmission electron microscopy (TEM).     

Fabricating Dual‐Atom Iron Catalysts for Efficient Oxygen Evolution Reaction: A Heteroatom Modulator Approach

Understanding the thermal aggregation behavior of metal atoms is important for the synthesis of supported metal clusters. Here, derived from a metal–organic framework encapsulating a trinuclear Fe^III₂Fe^II complex (denoted as Fe₃) within the channels, a well‐defined nitrogen‐doped carbon layer is fabricated as an ideal support for stabilizing the generated iron nanoclusters. Atomic replacement of Fe^II by other metal(II) ions (e.g., Zn^II/Co^II) via synthesizing isostructural trinuclear‐complex precursors (Fe₂Zn/Fe₂Co), namely the “heteroatom modulator approach”, is inhibiting the aggregation of Fe atoms toward nanoclusters with formation of a stable iron dimer in an optimal metal–nitrogen moiety, clearly identified by direct transmission electron microscopy and X‐ray absorption fine structure analysis. The supported iron dimer, serving as cooperative metal–metal site, acts as efficient oxygen evolution catalyst. Our findings offer an atomic insight to guide the future design of ultrasmall metal clusters bearing outstanding catalytic capabilities.     

Single-Source Molecular Precursor for Synthesis of Copper Sulfide Nanostructures

As a new precursor, [bis(thiosemicarbazide)copper(II)]chloride; ([Cu(TSC)₂]Cl₂), complex was used in thermal decomposition process for the synthesis of Cu₂S nanocrystals. The steric hindrance of the precursor raises the need of using co-surfactant, therefore oleylamine (C₁₈H₃₇N) and triphenylphosphine (C₁₈H₁₅P) were applied as solvent and surfactant of the reaction. CuS nanocrystals were synthesized via hydrothermal decomposition of [bis(thiosemicarbazide) copper(II)] without any surfactant. The products were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and photoluminescence spectroscopy. Synthesized copper sulfide nanostructures have average size of 20–50?nm. Finally, optical properties of the products were examined and investigated by PL spectra.     

Towards Microwave Absorbing Metal-Oxide Nanocomposites: The Problem of Metal/Matrix Reaction

Thermostable microwave absorbing materials are of considerable interest for the applications with the tailored radar cross-section. Nanocomposites metal (Co, Fe)-dielectric (Al₂O₃, Al₂O₃2SiO₂, 3Al₂O₃2SiO₂) prepared by sol-gel route have been studied by electron microscopy and ⁵⁷Fe Mössbauer spectroscopy. The relationships between the micro/meso porosity, the composition and the state of the matrix precursor and the metal particle size are discussed with emphasis on the oxidation of nanoparticles. The size are discussed with emphasis on the oxidation of nanoparticles. Fe-based nanocomposites are obtained only using microporous host matrices. The interfacial reaction between iron nitrate solution precursor and host matrix promotes the formation of -(Fe_1-XAl₉)₂O₃ phase. The metal content is maximized by the use of highly concentrate iron solution and/or mixing with cobalt nitrate, in which case alloying particles are obtained.     

Synthesis,characterization, and properties of monodispersed magnetite coated multi‐walled carbon nanotube/polypyrrole nanocomposites synthesized by in‐situ chemical oxidative polymerization

This study describes the preparation of a nanocomposites fabricated from monodispersed 4‐nm iron oxide (Fe₃O₄) coated on the surface of carboxylic acid containing multi‐walled carbon nanotube (c‐MWCNT) and polypyrrole (PPy) by in situ chemical oxidative polymerization. High‐resolution transmission electron microscopy images and X‐ray diffraction (XRD) data indicate that the resulting Fe₃O₄ nanoparticles synthesized using the thermal decomposition are close to spherical dots with a particle size about 4 ± 0.2 nm. The resulting nanoparticles were further mixed with c‐MWCNT in an aqueous solution containing with anionic surfactant sodium bis(2‐ethylhexyl) sulfosuccinate to form one‐dimensional Fe₃O₄ coated c‐MWCNT template for further preparation of nanocomposite. Structural and morphological analysis using field‐emission scanning electron microscopy, high‐resolution transmission electron microscopy, and XRD showed that the fabricated Fe₃O₄ coated c‐MWCNT/PPy nanocomposites are one‐dimensional core (Fe₃O₄ coated c‐MWCNT)‐shell (PPy) structures. The conductivities of these Fe₃O₄ coated c‐MWCNT/PPy nanocomposites are about four times higher than those of pure PPy matrix. © 2008 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 46: 727–733, 2008     

Bildung von Fe3S4?FeS2 durch hydrothermale Reaktion

A mixture of Fe₃S₄ (greigite) and FeS₂ (pyrite) is formed at 200°C on hydrothermal treatment of freshly precipitated iron sulphide. Its electron diffraction diagramm was recorded, which corresponded to an incomplete solid solution of Fe₃S₄ and FeS₂. The surface and the interior of the spherical particles of the samples (size about 500 Å) consisted of Fe₃S₄ and FeS₂, respectively.