Dielectric response of one-dimensional polar chains

We propose a theory for the dielectric constant of materials made of parallel infinite one-dimensional chains of dipoles. Each dipole is allowed to rotate in three dimensions. Monte Carlo simulations show that the Kirkwood factor of the chain grows with increasing dipole moment much faster than in the case of three-dimensional polar fluids. With increasing dipole moment or cooling the one-dimensional chain undergoes a continuous order-disorder transition to the ferroelectric phase, in which the dielectric constant is limited by the size of ferroelectric domains along the chain.     

Facile solvothermal synthesis of graphene-MnOOH nanocomposites

In this paper, we report a facile solvothermal route capable of aligning MnOOH nanocrystals on graphene. X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations indicate that the exfoliated graphene sheets are decorated randomly by MnOOH nanocrystals, forming well-dispersed graphene-MnOOH nanocomposites. Dissolution-crystallization and oriented attachment are speculated to be the vital mechanisms in the synthetic process. The attachment of additives, such as MnOOH nanoparticles, are found to be beneficial for the exfoliation of GO as well as preventing the restack of graphene sheets. Moreover, cyclic voltammetry (CV) analyses suggest that the electrochemical reversibility is improved by anchoring MnOOH on graphene. Notably, the as-fabricated nanocomposites reveal unusual catalytic performance for the thermal decomposition of ammonium perchlorate (AP) due to the concerted effects of graphene and MnOOH. This template-free method is easy to reproduce, and the process proceeds at a low temperature and can be readily extended to prepare other graphene-based nanocomposites.     

Synthesis of dandelion-like three-dimensional nickel nanostructures via solvothermal route

The objectives of the present research are synthesizing three-dimensional （3D） nickel nanostructures and investigating their magnetic properties. Thus a template-free method was used to prepare 3D dandelion-like nickel nanostructures via reducing of nickel chloride with hydrazine hydrate in ethylene glycol solution at 100 ℃. The resulting Ni nanostructures were characterized by means of powder X-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electron microscopy （TEM）, and selected-area electron diffraction （SAED）. And the magnetic properties of the 3D Ni nanostructures were measured as well. Results indicated that solvothermal process could be successfully used to prepare 3D dandelion-like nanostructures of Ni at a relatively mild temperature of 100℃. And the conclusions were made as follows： as-prepared Ni samples had obvious shape anisotropy and were composed of fine nanocrystallites, while they had significantly enhanced ferromagnetic properties than bulk Ni and Ni nanoparticles.     

Structure-directing coordination template effect of ethylenediamine in formations of ZnS and ZnSe nanocrystallites via solvothermal route

ZnS and ZnSe precursors (ZnS x 0.5en and ZnSe x 0.5en, en = ethylenediamine) were prepared via a solvothermal process using ethylenediamine as solvent. Phase-pure hexagonal wurtzite ZnS and ZnSe products were obtained by annealing the precursors in argon stream at temperatures above 350 degrees C. The role of ethylenediamine as a structure-directing coordination molecular template responsible for the morphologies of the annealed products was discussed. This work provided further insights into the solvent coordination molecular template (SCMT) mechanism previously proposed to explain the growth mechanism of CdE (E = S, Se, Te) nanorods in ethylenediamine (Inorg. Chem. 1999, 38, 1382). The as-prepared precursors as well as the annealed products were characterized by powder X-ray diffraction (XRD), transmission electron microscopy (TEM), infrared absorbance spectroscopy (IR), thermogravimetric analysis (TGA), X-ray fluorescence (XRF) analysis, and combustion analysis for C, N, H contents.     

Flowerlike MoS2 nanoparticles: solvothermal synthesis and characterization

Flowerlike MoS₂ nanoparticles have been successfully synthesized through a mild solvothermal reaction with the aid of ethanol aqueous solution, and the samples have been characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), and low temperature nitrogen adsorption-desorption. The nanometer flower MoS₂ is composed of ultrathin nanosheets of approximately 10 nanometers in thickness. The influence of the reaction temperature and the reaction time on the formation of the flowerlike MoS₂ nanoparticles were evaluated. The optimal experimental conditions were determined as follows: the molar ratio of 1:1 between ethanol and water, the reaction temperature of 190°C, and the reaction time of 24 h. __________ Translated from Chinese Journal of Inorganic Chemistry, 2008, 24(6) (in Chinese)     

Subcritical solvothermal synthesis of condensed inorganic materials

The solvothermal method has recently been extended from zeolite synthesis to the formation of condensed inorganic solids, which find uses in diverse areas due to properties such as ionic-conductivity, solid-state magnetism, giant magnetoresistance, low thermal expansion and ferroelectricity. This offers specific advantages over the traditional ceramic synthetic routes to inorganic solids and these are highlighted with examples from the recent literature, and the efforts focussed on determining the formation mechanism of solids from the heterogeneous mixtures used in solvothermal procedures are discussed.     

溶剂热合成磷酸亚铁锂的研究

以溶剂热方法首次合成了橄榄石相的磷酸亚铁锂,并以水热法为参照.使用XRD,TEM和FT-IR等手段进行表征.溶剂热法制备的样品呈球形或多面体状.而水热法制备的颗粒则由纤维状成长为菱形.两种方法产物的形状差异可能是由于溶剂热反应体系中较高的压力抑制了纤维态晶体的产生.溶剂热法和灼烧都有利于磷酸亚铁锂晶相发育.     

Microemulsion-mediated solvothermal synthesis of SrCO3 nanostructures

The controlled synthesis of SrCO3 nanostructures with different morphologies, such as rodlike, whiskerlike, ellipsoidlike, and spherelike, were successfully achieved by the cationic surfactant-CTAB-microemulsion-mediated solvothermal method. Various comparison experiments showed that fundamental experimental parameters, such as the molar ratio of H2O to CTAB and the concentration of reactants, played important roles in the morphological control of SrCO3 nanostructures. A lower molar ratio of H2O to CTAB favors rodlike products, whereas a higher molar ratio generally leads to the formation of spherical products. A rational mechanism based on fusion, aggregate, and coalescence of microemulsion droplets is proposed for the selective formation of various morphologies. X-ray powder diffraction (XRD), transmission electron microscopy (TEM), selected area electron diffraction (SAED), and field-emission scanning electron microscope (FE-SEM) were used to characterize the products.     

Hydrothermal synthesis of three-dimensional open-framework beryllium phosphites with 3,4-connected networks

Two new beryllium phosphites, H₂en·Be₃(HPO₃)₄ (1) and H₂pda·Be₃(HPO₃)₄ (2), have been synthesized under hydrothermal conditions. Single-crystal structural analyses reveal that both compounds have three-dimensional inorganic frameworks constructed from strictly alternating BeO₄ tetrahedra and HPO₃ pseudo pyramids. The structure of compound 1 can be described as a pillared layered structure with 12-ring channels. The structure of compound 2 has an interesting sqp topology if Be₃(HPO₃)₄ clusters are regarded as 5-connected nodes in the network.     

One-step synthesis of three-dimensional Pd polyhedron networks with enhanced electrocatalytic performance

Three-dimensional Pd polyhedron networks (Pd PNs) have been fabricated for the first time through a one-step, Cu(2+)-assisted, solution-chemical approach. These as-prepared 3D Pd PNs exhibit high stability and remarkably improved electrocatalytic activity toward formic acid oxidation over commercially available Pd black.     

Shape-controlled solvothermal synthesis of bismuth subcarbonate nanomaterials

Much effort has been devoted to the synthesis of novel nanostructured materials because of their unique properties and potential applications. Bismuth subcarbonate ((BiO)₂CO₃) is one of commonly used antibacterial agents against Helicobacter pylori (H. pylori). Different (BiO)₂CO₃ nanostructures such as cube-like nanoparticles, nanobars and nanoplates, were fabricated from bismuth nitrate via a simple solvothermal method. The nanostructures were characterized by powder X-ray diffraction (XRD), scanning electron microscope (SEM), transmission electron microscopy (TEM) and high-resolution transmission electron microscopy (HRTEM). It was found that the solvents and precursors have an influence on the morphologies of (BiO)₂CO₃ nanostructures. The possible formation mechanism of different (BiO)₂CO₃ nanostructures fabricated under different conditions was also discussed.     

Open three-dimensional unhindered molecular chains: Partition function

An open molecular chain, formed by N classical particles moving in three dimensions and having N − 1 bonds of constant lengths between successive neighbours, is considered. Hamiltonian methods with manifest rotational invariance allow to characterize all constraints. The classical partition function, Z₀, for a large open chain in thermal equilibrium is analyzed in general. Simpler integral representations for Z₀ are obtained, with the following advantages: (i) explicit rotational invariance in the integrands, (ii) only tridiagonal matrices appear and, moreover, approximations for their determinants can be obtained. For a two-dimensional open chain, an approximate factorized formula for Z₀ is presented, and its essentials are generalized to the three-dimensional case. In both cases, the features of the partition functions bear certain similarities to that for a classical ideal gas. The approximate partition functions lead to approximate analytical computations of the correlations between pairs of different bond vectors, of the squared end-to-end distance, of the probability distribution for the end-to-end vector and of the structure factor, which display some novel features. Some comparisons with the corresponding results for the Gaussian chain are made.     

New routes to high nuclearity cages: dimerisation of a manganese triangle via solvothermal synthesis

Heating [Mn3O(O2CPh)6(py)2(H2O)] in MeCN at 100 degrees C for 12 hours in a sealed Teflon container produces the hexanuclear species [Mn6O2(O2CPh)12(py)2]: dimerisation of the triangle occurs via solvent loss and ligand rearrangement.     

Direct solvothermal synthesis of early transition metal nitrides

Solvothermal reactions of TaCl5 with LiNH2 in benzene result in nanocrystalline Ta3N5 at 500 or 550 degrees C. The approximately 25 nm Ta3N5 particles have a band gap of 2.08-2.10 eV. The same reactions in mesitylene resulted in a higher crystallization temperature and large amounts of carbon incorporation due to solvent decomposition. Reactions of Ta(NMe2)5 with LiNH2 under the same conditions resulted in TaN. Rocksalt-type MN phases are obtained for Zr, Hf, or Nb when their chlorides (ZrCl4, HfCl4, or NbCl5) or dialkylamides (M(NEtMe)4, M = Zr, Hf) are reacted with LiNH2 under similar conditions. With the amides, there is some evidence for nitrogen-rich compositions (HfN >1), and carbon is incorporated into the products through pyrolysis of the dialkylamide groups.     

Two three-dimensional metal-organic frameworks containing one-dimensional hydroxyl/carboxylate mixed bridged metal chains: syntheses, crystal structures, and magnetic properties

Two novel three-dimensional complexes formulated as [M(3)(bime)2(mu3-OH)2(HO-BDC)2]n (M = Co, 1; Cu, 2) [bime = 1,2-bis(imidazol-1'-yl)ethane, HO-H2BDC = 5-hydroxyisophthalic acid] have been hydrothermally synthesized and characterized. Both 1 and 2 exhibit similar structural frameworks resulting from one-dimensional metal/oxygen chains extended by HO-BDC, but the bridging modes of HO-BDC and coordination environments of metal centers are different. Complexes 1 and 2 crystallize in the orthorhombic system, space group Pbcn, a = 18.458(2) [18.2119(12) for 2] Angstroms, b = 12.0616(14) [11.6847(7)] Angstroms, c = 11.4859(14) [12.0688(6)] Angstroms, and Z = 4 (4). Magnetic studies show that 1 displays a slow magnetic relaxation, a large hysteresis, and distinct finite-size effects and 2 contains an antiferromagnetic chain.     

Toward controlled spacing in one-dimensional molecular chains: alkyl-chain-functionalized fullerenes in carbon nanotubes

A range of fullerenes (C60) functionalized with long alkyl chains have been synthesized and inserted into single-walled carbon nanotubes. The impact of the alkyl chain length and of the type of linker between the addend and the fullerene cage on the geometry of molecular arrays in nanotube has been studied by high-resolution transmission electron microscopy. In the presence of functional groups the mean interfullerene separations are significantly increased by 2-8 nm depending on the length of the alkyl chain, but the periodicity of the fullerene arrays is disrupted due to the conformational flexibility of the alkyl groups.     

Controlled solvothermal synthesis of novel organic functionalized polyoxovanadates

Four novel organic functionalized polyoxovanadates are solvothermally synthesized by altering the reaction temperature and using different organoarsonic acids. These POVs are fully characterized and the phase transitions between different POVs structures are confirmed by X-ray diffraction analyses. Such a transition is temperature-dependent and thus controlled synthesis of new POVs can be achieved.