Low-temperature synthesis and growth mechanism of uniform nanorods of bismuth sulfide

A low-temperature solution-phase method has been demonstrated for the synthesis of uniform nanorods of Bi₂S₃ with diameter of 18 nm and length of below 200 nm. Transmission electron microscopy (TEM), selected-area electron diffraction (SAED), and X-ray diffraction (XRD) studies revealed that these nanorods were grown from a colloidal dispersion of amorphous Bi₂S₃ particles, which was first formed through a thermal reaction between Bi-thiol complexes Bi(SC₁₂)₃ and thioacetamide (TAA) in a pure dodecanethiol (C₁₂SH) solvent at a temperature of 95 °C. Based on these studies, the growth mechanism of Bi₂S₃ nanorods was properly proposed.     

Direct growth of comet-like superstructures of Au-ZnO submicron rod arrays by solvothermal soft chemistry process

The synthesis, characterization and proposed growth process of a new kind of comet-like Au-ZnO superstructures are described here. This Au-ZnO superstructure was directly created by a simple and mild solvothermal reaction, dissolving the reactants of zinc acetate dihydrate and hydrogen tetrachloroaurate tetrahydrate (HAuCl₄·4H₂O) in ethylenediamine and taking advantage of the lattice matching growth between definitized ZnO plane and Au plane and the natural growth habit of the ZnO rods along [001] direction in solutions. For a typical comet-like Au-ZnO superstructure, its comet head consists of one hemispherical end of a central thick ZnO rod and an outer Au-ZnO thin layer, and its comet tail consists of radially standing ZnO submicron rod arrays growing on the Au-ZnO thin layer. These ZnO rods have diameters in range of 0.2-0.5 μm, an average aspect ratio of about 10, and lengths of up to about 4 μm. The morphology, size and structure of the ZnO superstructures are dependent on the concentration of reactants and the reaction time. The HAuCl₄·4H₂O plays a key role for the solvothermal growth of the comet-like superstructure, and only are ZnO fibers obtained in absence of the HAuCl₄·4H₂O. The UV-vis absorption spectrum shows two absorptions at 365-390 nm and 480-600 nm, respectively attributing to the characteristic of the ZnO wide-band semiconductor material and the surface plasmon resonance of the Au particles.     

Novel pseudo-morphotactic synthesis and characterization of tungsten nitride nanoplates

A novel pseudo-morphotactic transformation route was developed to synthesize polycrystalline β-W₂N nanoplates by thermally treating tungstate-based inorganic-organic hybrid nanobelts with a lamellar microstructure in an NH₃ flow. The tungstate-based hybrid nanobelts were formed in a water-in-oil-microemulsion-like “commercial H₂WO₄ powders/n-octylamine/heptane” reaction system. The as-obtained hybrid nanobelts were thermally treated in an NH₃ atmosphere at 650-800 °C for 2 h to form cubic β-W₂N nanoplates. XRD, SEM, TEM, FT-IR and TG-DTA were used to characterize the precursors and their final products. The polycrystalline β-W₂N nanoplates derived from hybrid nanobelts, with side lengths of several hundred nanometers, consist of small nanocrystals with an average grain size of 3.2 nm. The formation of β-W₂N nanoplates involved two steps: decomposing tungstate-based hybrid nanobelts into WO_y and W species and then nitridizing the active W-containing species to β-W₂N nanocrystals in an NH₃ flow. The platelike morphology of the β-W₂N nanocrystals was inherited from the precursor of tungstate-based inorganic-organic hybrid nanobelts.     

Large-scale synthesis of single-crystal hexagonal tungsten trioxide nanowires and electrochemical lithium intercalation into the nanocrystals

Single-crystal nanowires of hexagonal tungsten trioxide in a large scale have been successfully prepared by a simple hydrothermal method without any templates and catalysts. Uniform h-WO₃ nanowires with diameter of 25-50 nm and length of up to several micrometers are obtained. It is found that the morphology and crystal form of the final products are strongly dependent on the amount of the sulfate and pH value of the reaction system. The electrochemical performances of the as-prepared h-WO₃ nanowires as anodic materials of Li-ion batteries have also been investigated. It deliveres a discharge capacity of 218 mAh g⁻¹ for the first cycle. In addition, the cycle ability of the nanocrystals is superior to that of bulk materials, which implies the morphology and particle size have the influence on the electrochemical performances.     

Syntheses and characterization nano-structured bismuth(III) oxide from a new nano-sized bismuth(III) supramolecular compound

Nano-particles of a new Bi(III) supramolecular compound, {Bi₂(μ-4,4′-bipy)Cl₁₀] · 2(4,4′-Hbipy) · (4,4′-H₂bipy) · 2H₂O} (1) {4,4′-bipy = 4,4′-bipyridine}, were synthesized by a sonochemical method. The nano-material was characterized by scanning electron microscopy, X-ray powder diffraction (XRD), IR spectroscopy and elemental analyses. Crystal structure of compound 1 was determined by X-ray crystallography. Calcination of the nano-particles of compound 1 at 400 °C under air atmospheres yields nano-sized particles of α-Bi₂O₃.     

共沉淀法制备PEOUIC的形貌与结构分析

包合复合物(ICs)是超分子化学的重要组成部分。以尿素作为主体分子,PEO作为客体分子,通过共沉淀法制备了不同PEO与Urea比例的PEOUIC,而后分别利用DSC、XRD、SEM、POM分析了PEOUIC晶体的形貌与结构。结果表明:利用共沉淀法可制备六方以及四方晶系的PEOUIC晶体;当PEO与Urea质量比小于为1时,形成四方晶系PEOUIC晶体;而当质量比大于1时,形成六方晶系PEOUIC晶体;随着Urea含量的增大,PEOUIC的T_m先增大在趋于稳定不变;四方晶系PEOUIC晶体呈现球晶形貌,六方晶系呈现中心突起的六边形柱状体形貌。     

Syntheses and characterization of a new nano-structured bismuth(III) bromide coordination polymer; new precursor for preparation of bismuth(III) bromide and bismuth(III) oxide nanostructures

Nanoparticles of a Bi(III) coordination polymer, {[Bi(μ-4,4′-bipy)Br₄] · (4,4′-Hbipy)} _n (1) (4,4′-bipy = 4,4′-bipyridine), were synthesized by a sonochemical method. The new nanoparticles were characterized by scanning electron microscopy, X-ray powder diffraction (XRD), IR spectroscopy, and elemental analyses. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The thermal stabilities of 1 as bulk and at nanosize were studied by thermal gravimetric (TG) and differential thermal analyses (DTA). The Bi₂O₃ and BiBr₃ nanostructures were obtained by calcinations of nanostructure of 1 in air and argon.     

Structure and growth of single crystal SiP2 using flux method

A new orthorhombic phase of silicon diphosphide has been grown in Sn flux by using Gd as a mineralizer. It is a needle-like crystal and its structure has been determined through single crystal X-ray diffraction and elemental analysis. It crystallizes in the orthorhombic space group Pnma (No. 62, Z = 8) with cell parameters: a = 10.0908(19) Å, b = 3.4388(6) Å and c = 13.998(3) Å and the final R value is 0.0294. It has a layered structure that is closely related to the Pbam phase of SiP₂. Its optical band gap is 1.45 eV and it decomposes at 1002 K.     

Inhibation of crystal growth during drying in gels derived from a cheap,mixed metal oxide precursor

The influence of addition of small amounts of either citric acid or lactic acid on the formation of crystalline matter in dried gels derived from a multi-component industrial sol–gel silica precursor has been studied. The sols were water-based and had formic acid as the main acid constituent. A pronounced decrease in the extent of crystallization was observed for both acids, with citric acid being more effective than lactic acid. The results are discussed based on the complexation behavior of the corresponding acids under the studied conditions, and the complexation behavior in solution can be directly linked to the extent of crystallization in the dried gels. However, the sol–gel kinetics followed that expected for a purely silica-based sol, which suggests that the kinetics is mainly controlled by the silica portion of the sol. The results are suggested to be of importance for the industrial use of these sols as binders, as pronounced crystallization in the gels upon drying may lead to mechanical stresses, and thus to a decreased binder performance.     

Simultaneous growth of diamond and nanostructured graphite thin films by hot-filament chemical vapor deposition

Diamond and graphite films on silicon wafer were simultaneously synthesized at 850 °C without any additional catalyst. The synthesis was achieved in hot-filament chemical vapor deposition reactor by changing distance among filaments in traditional gas mixture. The inter-wire distance for diamond and graphite deposition was kept 5 and 15 mm, whereas kept constant from the substrate. The Raman spectroscopic analyses show that film deposited at 5 mm is good quality diamond and at 15 mm is nanostructured graphite and respective growths confirm by scanning auger electron microscopy. The scanning electron microscope results exhibit that black soot graphite is composed of needle-like nanostructures, whereas diamond with pyramidal featured structure. Transformation of diamond into graphite mainly attributes lacking in atomic hydrogen. The present study develops new trend in the field of carbon based coatings, where single substrate incorporate dual application can be utilized.     

Synthesis and structural characterization of YVO3 prepared by sol–gel acrylamide polymerization and solid state reaction methods

The formation of the YVO₃ compound obtained by sol–gel acrylamide polymerization is reported. This synthesis method is contrasted with solid state reaction. Differential thermal analysis (DTA) results show the formation of YVO₃ at 805 °C compared with 1312 °C for solid state reaction. Thermogravimetric analysis (TG) results show that between 400 and 600 °C the denaturalization of the organic part, ethylenediamine, and the decomposition of nitrates occur. The evolution of YVO₄ into YVO₃ was also studied by X-ray powder diffraction (XRD). The refinement results obtained for both YVO₃ samples show an orthorhombic phase with Pbnm (62) space group and lattice parameters: a = 5.283 Å, b = 5.605 Å and c = 7.580 Å. Grain size and morphology evolution for different heat treatments were studied with scanning electron microscopy (SEM). The use of sol–gel acrylamide synthesis allows us to start with a homogeneous grain distribution with a mean size of 5.03 ± 0.65 nm growing up to 4.11 ± 0.87 μm in YVO_4. After reduction to YVO₃ the final grain size was 2.87 ± 0.10 μm also with grain size homogeneity. This is in contrast with samples prepared by solid state reaction for which the grain size starts (YVO₄) between 1 and 7.0 μm and ends (YVO₃) with a size distribution centered at 90.32 ± 74.46 μm. Transmission electron microscopy (TEM) results corroborate XRD results. Energy dispersive X-ray (EDX) results are in agreement with theoretical values.     

成膜溶剂对聚4-甲基戊烯-1膜的形态结构和透过行为的影响——Ⅰ.膜的结晶性质与表面形态

以聚4-甲基戊烯-1(PMP)为膜材质,分别以环己烷、三氯乙烯、四氯乙烯、环己烷/三氯乙烯及环己烷/四氯乙烯为溶剂,研究了这些溶液浇铸膜的结晶性质和表面形态。结果表明,溶剂对PMP的相对溶解能力和挥发速度同所成膜内PMP的结晶形式和结晶度密切相关;不同溶剂体系的PMP溶液浇铸膜的表面形态也不尽相同。并发现以四氯乙烯(或三氯乙烯)为溶剂或溶剂组分之一的PMP溶液浇铸膜存在未见报道的Ⅵ型结晶。     

Hydrothermal synthesis and morphology variation of cadmium hydroxyapatite

Cadmium hydroxyapatite (Cd-Hap) crystals were synthesized by hydrothermal method at 200 °C using the solutions of Cd(NO₃)₂·4H₂O and (NH₄)₂HPO₄. Influences of pH values and reaction time on the crystalline phases and morphology of the products were investigated. In low pH reaction media, Cd₅H₂(PO₄)₄·4H₂O was formed and a relatively high pH reaction media was necessary to obtain Cd-Hap. Morphology of the Cd-Hap crystals changed from stubby hexagonal prismatic to rod-like in shape with the increase in the pH value. This morphological change was explained by the difference in growth mechanism through intermediate phases, Cd₅H₂(PO₄)₄·4H₂O in the low pH reaction media and Cd₂P₂O₇·5H₂O in the high pH reaction media.     

Surfactant effects on pH-controlled synthesis of nickel hydroxides

The aim of the present work is to determine at 60 °C, the influence of the specific nature of nickel salt and pH on nickel hydroxide features such as crystallographic structure and morphology. Within the range 8 ≤ pH ≤ 11.5, a home-made nickel functionalized surfactant, nickel di-dodecylsulfate Ni(C₁₂H₂₅SO₄)₂ is compared to usual salts (nickel nitrate Ni(NO₃)₂ and nickel sulfate NiSO₄). In both cases, a sharp transition appears for pH about 10. In the classic salt case, the transition mainly affects morphology, that could be evidenced by the crosschecking of complementary techniques as SEM and nitrogen gas adsorption. For pH < 10, β-Ni(OH)₂ platelets are yielded, whereas more basic conditions lead to randomly aggregated nano-grains of badly crystallized β hydroxide. Inversely, by employing the functionalized surfactant, 2D morphology is maintained in the whole pH-range, but the crystal structure is pH-controlled ( phase with interlamellar dodecylsulfate for pH ≤ 9.5, and β phase for pH ≥ 10.5).     

Role of the oriented attachment mechanism in the phase transformation of oxide nanocrystals

"Bottom-up" methods to obtain nanocrystals usually result in metastable phases, even in processes carried out at room temperature or under soft annealing conditions. However, stable phases, often associated with anisotropic shapes, are obtained in only a few special cases. In this paper we report on the synthesis of two well-studied oxides-titanium and zirconium oxide-in the nanometric range, by a novel route based on the decomposition of peroxide complexes of the two metals under hydrothermal soft conditions, obtaining metastable and stable phases in both cases through transformation. High-resolution transmission electron microscopy analysis reveals the existence of typical defects relating to growth by the oriented attachment mechanism in the stable crystals. The results suggest that the mechanism is associated to the phase transformation of these structures.     

氨基酸辅助合成多种形貌纳米材料的研究进展

氨基酸等生物大分子作为一种特殊的表面活性剂,在合成特殊形貌纳米材料方面具有很大的应用潜力.本文综述了使用多种氨基酸辅助合成的不同形貌的纳米材料,包括一维纳米材料、雪花状纳米结构、三维纳米球等,并对生物科学和化学学科间的交叉发展进行了展望.     

Bi2Te3-Te nanocomposite formed by epitaxial growth of Bi2Te3 sheets on Te rod

Single-crystal Bi₂Te₃-Te nanocomposites with heterostructure were synthesized using a two-step solvothermal process in the presence of ethylenediaminetetraacetic acid disodium salt. The first step is the formation of the Te nanorods and the second step is to grow the Bi₂Te₃ sheets off the Te rods surface to form the Bi₂Te₃-Te nanocomposites. The products were characterized by X-ray diffraction, scanning electron microscopy and transmission electron microscopy. We demonstrate a method of an epitaxial growth of Bi₂Te₃ nanosheets perpendicular to the axis of the central Te rod and a formation process of Bi₂Te₃-Te nanocomposites is also proposed.     

Epitaxial growth of AlN films on single-crystalline Ta substrates

We have demonstrated the first epitaxial growth of AlN films on single-crystalline Ta substrates by the use of a low-temperature growth technique based on pulsed laser deposition (PLD). Although previous AlN films grown on Ta(100) and (111) substrates have exhibited quite poor crystallinity, an epitaxial AlN(0001) film with an in-plane epitaxial relationship of AlN[112¯0]//Ta[001] has been obtained on a Ta(110) substrate at a growth temperature of 450 °C. We found that the full-width at half-maximum values for the crystal orientation distribution in the tilt and twist directions of the AlN film were 0.37° and 0.41°, respectively. Grazing-incidence X-ray reflection (GIXR) and X-ray photoelectron spectroscopy (XPS) measurements have revealed that the AlN/Ta heterointerface is quite abrupt, and that its abruptness remains unchanged even after annealing at 1000 °C.