A simple method to synthesize single-crystalline lanthanide orthovanadate nanorods

Single-crystalline tetragonal LnVO₄ (Ln=La, Nd, Sm, Eu, Dy) nanorods were prepared via a simple hydrothermal method, in the absence of any surfactant or template using cheap and simple inorganic salts as raw materials. The products were characterized by XRD, TEM, HRTEM, and PL. It has been shown that after the hydrothermal process, LaVO₄ transformed its crystal structure from monoclinic to tetragonal phase, but LnVO₄ (Ln=Nd, Sm, Eu, Dy) have not exhibited the structural change. This could be associated with the change of lanthanide ion radius. TEM and HRTEM results show that the nanorods are pure, structurally uniform, single crystalline, and most of them are free from dislocations. Further study reveals the nanorods grow along the [001] direction. A possible growth mechanism of lanthanide orthovanadate nanorods was also proposed. The advantages of our method for the nanorods synthesis lie in the high yield and the low temperature and mild reaction conditions, which permit large scale production at low cost.     

Characterization of h-WO3 nanorods synthesized by hydrothermal process

Hexagonal tungsten oxide nanorods have been synthesized by hydrothermal strategy using Na₂WO₄·2H₂O as tungsten source, aniline and sulfate sodium as structure-directing templates. Techniques X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy have been used to characterize the structure, morphology and composition of the nanorods. The h-WO₃ nanorods are up to 5 μm in length, and 50–70 nm in diameter.     

Controlled synthesis of single-crystalline Mg(OH)2 nanotubes and nanorods via a solvothermal process

The synthesis of Mg(OH)₂ one-dimensional (1D) nanostructures was systematically investigated in different solvents at various temperatures with Mg₁₀OH₁₈Cl₂·5H₂O nanowires as source materials. The results showed that the characters of the products, such as crystal size, shape, and structure, were strongly influenced by the solvent and temperature during the solvothermal process. 1D nanotubes of Mg(OH)₂, with 80-300 nm outer diameter, 30-80 nm wall thickness, and several tens of micrometers in length were obtained by choosing bidentate ligand solvents such as ethylenediamine and 1,6-diaminohexane as the reaction solvent. But when using monodentate ligand pyridine as the reaction solvent, the obtained samples showed nanorods morphology. The Mg(OH)₂ thus produced was analyzed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), high-resolution electron microscopy (HRTEM), and selected-area electron diffraction (SAED). The possible growth mechanism of the 1D nanostructure Mg(OH)₂ was discussed.     

Preparation and characterization of a novel zeolite using hydrothermal synthesis in a stirred reactor

This paper describes the preparation of novel zeolite particles by the hydrothermal method in a stirred reactor. The variations between certain properties of the resulting zeolites, such as morphology by the scanning electron microscopy (SEM), pore properties (i.e., surface areas, pore volume, and porosity) by the surface area & porosity analyzer, crystallinity by the X-ray diffraction (XRD) and Si/Al ratio by the inductively coupled plasma-atomic absorption spectrometer (ICP-AES), and the process parameters, such as aging time, agitation speed, temperature and pressure, were studied at a specific gel composition. The optimal value of the Brunauer–Emmett–Teller (BET) surface area was found to be over 400 m²/g in the resulting microporous zeolite, indicating that the size was centered on about 0.5 nm. The XRD image was indicative of the probable formation of zeolite-P2 in the hydrothermal synthesis.     

Mercury selenide nanorods: Synthesis and characterization via a simple hydrothermal method

HgSe nanorods have been synthesized through a simple hydrothermal reduction approach. The nanorods formed were ≈45 nm average diameter and ≈3 μm nm in length. X-ray diffraction characterization suggested that the product consists of cubic phase pure HgSe. The as-prepared products were also characterized by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). An X-ray energy dispersive spectroscopy (EDX) study further confirmed the composition and purity of the product. The synthesis procedure is simple and uses less toxic reagents than the previously reported methods. The results showed that the capping agent CTAB (cetyltrimethylammoniumbromide) plays a crucial role in the process. Other factors, such as the reaction time, temperature, different capping agent and the reductant type also have an influence on the morphology of the final products to some extent.     

Fabrication of lead titanate single crystalline nanowires by hydrothermal method and their characterization

Single crystalline nanowires of lead titanate (PbTiO₃) were fabricated by hydrothermal method at 200°C using lead acetate and n-tetrabutyl titanate as starting materials, where sodium hydroxide was served as a mineralizer. Crystalline phases, microstructure and optical properties of PbTiO₃ nanowires were investigated. The PbTiO₃ nanowires were uniform and continuous along the long axis, and were composed of single crystalline PbTiO₃ with a tetragonal perovskite structure. The diameter of a single nanowire was around 12 nm and the length reached up to 3 μm. The chemical composition of the samples and the valence states of elements were determined by X-ray photoelectron spectroscopy (XPS). The ultraviolet/visible absorption spectroscopic investigation suggested that the absorption edge of optical transition of the first excitonic state occurred at around 320 nm. A blue-green light emission peaking at about 471 nm (2.63 eV) is observed at room temperature, and the intensity of this emission increased with increasing excitation wavelength. Oxygen vacancies are responsible for the light emission of PbTiO₃ nanowires.     

Synthesis and characterization of one-dimensional CdSe by a novel reverse micelle assisted hydrothermal method

Nanocrystalline cadmium selenide (CdSe) is a low bandgap material (E(g)=1.75 eV, at room temperature) with potential applications in photoelectronic devices. Its electronic properties are dependent on the dimensions of the crystals. In this study, one-dimensional wurtzite CdSe nanoparticles with a diameter of 43+/-6 nm and an aspect ratio of 3.7+/-0.6 were synthesized through a novel reverse micelle assisted hydrothermal method at a relatively low temperature. This method combines the advantages of the hydrothermal method's ability to achieve good crystallinity with the well-controlled growth offered by the reverse micelle method. The morphology of the nanoparticles can be controlled by the amount of sodium bis(2-ethylhexyl) sulfosuccinate (AOT), the amount of hydrazine hydrate and the reaction temperature. It is proposed that AOT controls the length while hydrazine hydrate controls the diameter of the growing nanocrystals. The photoluminescence (PL) of individual nanorods and the longitudinal-optical phonon properties were mapped using confocal microscopy. Raman spectroscopy showed a blue-shift of both the LO and 2LO phonon peaks which may be due to a lattice contraction of the CdSe nanorods. A nucleation and growth mechanism for these nanoparticles is also proposed based on time-dependent studies.     

Synthesis and characterization of vanadium oxides nanorods

Vanadium oxides nanorods with high crystallinity and high surface area were synthesized by hydrothermal method using laurylamine hydrochloride, metal alkoxide and acetylacetone. The samples characterized by XRD, nitrogen adsorption isotherm, SEM, TEM, and SAED. Uniformly sized B phase VO₂ nanorods had widths about 40-80 nm and lengths reaching up to 1 μm. V₂O₅ rodlike structured with the widths about 100-500 nm and the lengths of 1-10 μm were obtained by calcination at 400 °C for 4 h. This synthesis method provides a new simple route to fabricate one-dimensional nanostructured metal oxides under mild conditions.     

Phase-controlled synthesis and characterization of nickel sulfides nanorods

Different one-dimensional nickel sulfides, NiS nanorods and Ni₉S₈ nanorods were synthesized in the presence (Route 1) and absence (Route 2) of gas CO₂. X-ray powder diffraction patterns, scanning electron microscopy and transmission electron microscopy images show that the product from Route 1 is NiS nanorods with a diameter of about 50-120 nm, while the product from Route 2 is Ni₉S₈ nanords about 70-200 nm in diameter. A molecular-template-like mechanism was proposed for the one-dimensional structures growth. The products were also investigated by Raman and photoluminescence (PL) spectroscopy.     

Microemulsion-mediated hydrothermal synthesis and characterization of zircon-type LaVO4 nanowires

The zircon-type tetragonal (t-) LaVO₄ nanowires were controlled synthesized by a new approach, a microemulsion-mediated hydrothermal method, in which the aqueous cores of sodium dodecyl sulfate (SDS)/cyclohexane/n-hexanol/water microemulsion were used as constrained microreactors for a controlled growth of t-LaVO₄ nanocrystals under hydrothermal conditions. The microemulsion exists stably just at room temperature and not under hydrothermal conditions, in addition, the as-obtained nanowires are much larger than the microemulsion droplets, so that the microemulsion does not simply act as a template, but rather directs crystal growth into nanowires presumably by interacting with the surface of the growing crystal. A series of experimental results indicated that several experimental parameters, such as the SDS concentration, the species and content of the cosurfactant play important roles in the morphological control of the t-LaVO₄ nanocrystals. Possible formation mechanism of t-LaVO₄ nanowires is also discussed.     

Fabrication and characterization of hexagonal mesoporous silica monolith via post-synthesized hydrothermal process

Large-sized, optical transparent mesostructured Brij 56/silica monolith has been fabricated using a lyotropic liquid crystal of Brij 56 (C₁₆EO₁₀) as a template and TMOS as a silica source, combined with a optimizing sol-gel process and a hydrothermal aging process. By programmed temperature drying and calcinations, translucent mesoporous silica monolith with two-dimensional hexagonal structure (P6mm) has bee obtained. The ordered mesoporous silica monoliths have been characterized by small-angle X-ray diffraction, transmission electron microscopy (TEM), and nitrogen adsorption, which shows that the materials have a highly ordered two-dimensional hexagonal mesostructure with the high specific surface area of 837 m² · g⁻¹ and narrow pore distribution with a mean BJH pore diameter of 2.73 nm. Based on calculations and differential scanning calorimetry and thermogravimetric analyses, the action mechanism of the hydrothermal aging process has been proposed: the 100°C hydrothermal conditions and autogenous 2.3 atm pressure promote the condensation and dehydration of silanol groups, with the result that cross-linking degree, the flaws and moisture content in gels are reduced notably. Those processes guarantee the integrity of gels in the following drying process.     

氢氧化镍纳米棒的水热制备及其表征

以Ni₂SO₄·6H₂O和NaOH为原料,在水热条件下制备了氢氧化镍纳米棒.运用透射电子显微镜(TEM)和X射线衍射仪(XRD)对样品进行了表征,考察了水热反应温度和pH值对产物的形貌和结构的影响.结果表明,氢氧化镍纳米棒形成的最佳条件是180～200℃,pH为9～10.     

Syntheses and characterization of novel lanthanide adamantine-dicarboxylate coordination complexes

Hydrothermal reactions of 1,10-phenanthroline (phen), 1,3-adamantanedicarboxylic acid (H₂L) and lanthanide chlorides yielded six compounds: [Ln(L)(HL)(phen)] (Ln=Pr, 1; Nd, 2), [Ln(L)(HL)(phen)(H₂O)] (Sm, 3; Eu, 4), [Tb(L)(HL)(phen)(H₂O)]₂·2H₂O (5), [Er₃(L)₄(OH)(phen)]₂ (6). Compounds 1-4 are structurally featured by one-dimensional polymeric chains; 5 hold binuclear structure constructed from eight-coordinated lanthanide center LnN₂O₆ of distorted bicapped trigonal prism bridged by dicarboxylate ligands; 6 shows that erbium ions are in mono and bicapped trigonal prismatic geometries, respectively, which are further connected by μ₃-OH to give rise to trinuclear structure. Thermogravimetric analyses of 1, 3 and 5 were performed. Fluorescent measurements of 4 and 5 were carried out, respectively.     

Preparation and characterization of alumina supported silicalite membranes by sol–gel hydrothermal method

Two types of unsupported zeolites (silicalite-1 and silicalite-2) and porous alumina discs supports were prepared by the hydrothermal sol–gel synthesis method. The influence of the raw materials used as SiO₂ source, the temperature of the thermal treatment and the presence of the ceramic support on the crystallization of zeolites were studied. The reaction products were characterized by X-ray diffraction (XRD), IR spectroscopy (IR) and scanning electron microscopy (SEM) studies. The SiO₂ source had a significant effect on the final zeolite obtained: the use of colloidal silica sol (ZCS) as SiO₂ source in the synthesis led to ZSM-11 (silicalite-2) crystals, while the sodium silicate solution (ZSS) produced the ZSM-5 (silicalite-1) type. The presence of the alumina support influences the crystallization process of ZSM-5, as it improves nucleation and the ordering of the crystals.     

Hydrothermal Synthesis of Rhombus-like SmCO3OH Microplates and Its Photoluminescence Property Doped with Eu3+

Rhombus-like SmCO₃OH microplates with the edge lengths ranging from 5 μm to 10 μm and the thickness about 1.5 μm were synthesized through a simple hydrothermal method using urea as the precipitance. The structure and properties of the rhombus-like SmCO₃OH microplates were characterized by X-ray diffraction, field-emission scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The optical property of the rhombus-like SmCO₃OH microplates doped with Eu³⁺ was investigated by photoluminescence. A broad and strong emission band at 677 nm was obtained, which can be contributed to producing light conversion film.     

室温固相化学反应法合成Cd(OH)2纳米棒

在表面活性剂聚乙二醇(PEG)存在下,利用Cd(Ac)2·2H2O,CdCl2·2.5H2O,3CdSO4·8H2O和CdCO3分别与NaOH在室温下进行固相化学反应,合成了一系列的Cd(OH)2纳米棒,并利用XRD,TEM和SEM对其结构和形貌进行了表征.实验结果表明,表面活性剂PEG在Cd(OH)2纳米棒的形成过程中充当软模板,对产物形貌的控制起到决定作用.利用这种表面活性剂辅助的软模板固相化学反应法合成一维纳米材料,具有简便易行、反应条件温和以及能耗低等优点.     

水热微乳法合成La(OH)3纳米棒的形貌控制研究

自1991年Iijima发现碳纳米管以来,一维纳米材料如纳米管、纳米线、纳米棒和纳米纤维等由于其具有独特的光、电、磁等性质及其潜在的应用前景而引起全世界的广泛关注,一维纳米材料的制备方法有化学气相沉积法、溶胶一凝胶法、催化剂辅助法、固相化学反应法、模板法、溶剂热法、微乳法和水热,微乳法等,其中水热,微乳法是近年来兴起的一种很有发展前途的制备一维纳米材料的方法。     

Shape control of nickel selenides synthesized by a simple hydrothermal reduction process

Nickel selenide (NiSe) nanoparticles were prepared from the reaction of a SeCl₄ aqueous solution with a NiCl₂·6H₂O aqueous solution in the presence of polyvinyl alcohol (PVA) as a capping agent and hydrazine hydrate (N₂H₄·H₂O) as a reductant through a hydrothermal method. The size, morphology, chemical composition and purity of these nanoparticles depend on the capping agent, reductant, reaction temperature and time.