Synthesis and x-ray structural investigation of bismuth 2-methyl-8-quinolineselenolate Bi[C<Subscript>9</Subscript>H<Subscript>5</Subscript>(CH<Subscript>3</Subscript>)NSe]<Subscript>3</Subscript>

Bismuth 2-methyl-8-quinolineselenolate, Bi[C₉H₅(CH₃)NSe]₃, was synthesized. X-ray analysis was used to determine the structure of this complex. The crystal chemistry of bismuth(III), antimony(III), and arsenic(III) 2-methyl-8-quinolineselenolates and 2-methyl-8-quinolinethiolates was discussed relative to the effect of going from Se to S as the ligand atoms and presence of a methyl group at C-2 of the quinoline system and unshared electron pair of the central atom in the complex.     

Electrochemical deposition of Bi<Subscript>2</Subscript>Te<Subscript>3</Subscript> for thermoelectric microdevices

The electrolyses of solutions of bismuth oxide and tellurium oxide in nitric acid with molar ratios of Bi:Te=3:3–4:3 lead to cathodic deposits of films of bismuth telluride (Bi₂Te₃), an n-type semiconductor. Current densities of 2–5 mA/cm² were applied. Voltammetric investigations showed that Bi₂Te₃ deposition occurred at potentials more negative than −0.125 V (Ag/AgCl, 3 M KCl). The deposit was identified as bismuth telluride (γ-phase) by X-ray analysis. Hall-effect measurements verified the n-type semiconducting behaviour. The films can be deposited in microstructures for thermoelectric microdevices like thermoelectric batteries or thermoelectric sensors.     

Heat capacity and heat content of BiNb<Subscript>5</Subscript>O<Subscript>14</Subscript>

The heat capacity and the heat content of bismuth niobate BiNb₅O₁₄ were measured by the relaxation time method, DSC and drop method, respectively. The temperature dependence of heat capacity in the form C _pm=455.84+0.06016T–7.7342·10⁶/T ² (J K^–1 mol^–1) was derived by the least squares method from the experimental data. Furthermore, the standard molar entropy at 298.15 K S _m=397.17 J K^–1 mol^–1 was derived from the low temperature heat capacity measurement.     

Preparation,Thermal Behaviour,and Crystal Structure of MgAl<Subscript>2</Subscript>F<Subscript>8</Subscript>(H<Subscript>2</Subscript>O)<Subscript>2</Subscript>

Summary.  Single crystals of MgAl₂F₈(H₂O)₂ have been obtained under hydrothermal conditions (250°C, 14 d) from a starting mixture of AlF₃ and MgAlF₅(H₂O)₂ in a 5% (w/w) HF solution. The crystal structure has been determined and refined from single crystal data (Fmmm (#69), Z = 4, a = 7.2691(7), b = 7.0954(16), c = 12.452(2) ?, 281 structure factors, 27 parameters, R(F ² > 2σ (F ²)) = 0.0282, wR(F ² all) = 0.0885). The obtained crystals were systematically twinned according to (010/100/001) as twinning matrix, reflecting the pseudo-tetragonal metric. The crystal structure is composed of perowskite-type layers built of corner sharing AlF₆ octahedra with an overall composition of AlF₄ ⁻ which are connected via common fluorine atoms of [MgF_4/2(H₂O)_2/1] octahedra. Group-subgroup relations of MgAl₂F₈(H₂O)₂ to WO₃(H₂O)_0.33 and to other M(II)M(III)₂ F₈(H₂O)₂ structures are briefly discussed. Above 570°C, MgAl₂F₈(H₂O)₂ decomposes under elimination of water into α-AlF₃, β-AlF₃, and MgF₂. Received October 29, 2001. Accepted (revised) December 6, 2001     

Facile preparation and electrochemical properties of large-scale Li<Subscript>1+<Emphasis Type="Italic">x</Emphasis></Subscript>V<Subscript>3</Subscript>O<Subscript>8</Subscript> nanobelts

Large-scale Li_1+x V₃O₈ nanobelts were successfully fabricated using filter paper as deposition substrate through a simple surface sol–gel method. The nanobelts were as long as tens of micrometers with widths of 0.4–1.0 μm and thickness of 50–100 nm. The nanobelts were characterized by X-ray diffration (XRD), Fourier infrared (FT-IR) spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM). The formation mechanism of the nanobelts was investigated, showing that the morphology of the nanobelts is mainly determined by the calcination temperature. Electrochemical properties of the Li_1+x V₃O₈ nanobelts were characterized by charge–discharge experiments, and the results demonstrate that the Li_1+x V₃O₈ nanobelts exhibit a high discharge capacity (278 mAh g⁻¹) and excellent cycling stability.     

Aqueous sol–gel processing of precursor oxides for ZrW<Subscript>2</Subscript>O<Subscript>8</Subscript> synthesis

This paper describes the synthesis of ZrW₂O₈ by the use of an aqueous citrate-gel method in order to prepare a fine, pure and homogeneous oxide mixture suitable for ceramic processing. The thermal expansion coefficient thus obtained for α-ZrW₂O₈ is −10.6 × 10⁻⁶ °C⁻¹ (50–125 °C) whereas for the β-ZrW₂O₈ a value of −3.2 × 10⁻⁶ °C⁻¹ (200–300 °C) is obtained. The advantages of the use of a sol–gel method is expressed in the very homogeneous end-products. The paper describes crystallographic data, morphological structure and the thermal expansion properties of the ZrW₂O₈ material. Moreover, photoluminescence and photochromic properties specific to the precursor gel are described and analyzed. These effects support our views that the precursors show homogeneity up to nanometer level.     

Synthesis and structure of the polymeric complex [Ag<Subscript>2</Subscript>(Ph<Subscript>3</Subscript>P)<Subscript>2</Subscript>B<Subscript>10</Subscript>H<Subscript>10</Subscript>]<Subscript><Emphasis Type="Italic">n</Emphasis></Subscript>

A method for the synthesis of the silver(I) complex with the closo-decaborate anion and triphenylphosphine [Ag₂(Ph₃P)₂B₁₀H₁₀] _n was developed and the structure of this complex was studied. The polymeric chain of the complex is formed with participation of Ag(I) atoms, which coordinate the B₁₀H₁₀²⁻ anions through the apical (B(1)–B(2), B(9)–B(10)) and equatorial (B(3)–B(6), B(5)–B(8)) edges, the metalligand bonding occurring through three-center two-electron bonds (MHB). The P atoms of two triphenylphosphine molecules are also incorporated in the inner coordination sphere of the metal: the CN of the silver atom is 4 + 1.     

Bi<Subscript>3.25</Subscript>La<Subscript>0.75</Subscript>Ti<Subscript>3</Subscript>O<Subscript>12</Subscript> powders by the complex polymerization method: synthesis,characterization and morphology

Lanthanum-modified bismuth titanate (Bi_3.25La_0.75Ti₃O₁₂, BLTO) powders were prepared by the complex polymerization method. The structure and morphology of BLTO powders were investigated by X-ray diffraction and scanning electron microscopy. The complexation of citric acid with the metallic cations was detected by Fourier transformed infrared (FT-IR). The thermal analyses of obtained gels were investigated by differential thermal gravimetric (DTG). The pure and normally stoichiometric phase of BLTO powders could be obtained at relatively low temperature of 550–700 °C even if the bismuth content is not excess in the starting precursors, while the secondary phase could be detected at lower and higher calcination temperatures. The shape of the BLTO grains is similarly to platelet in Bi-layer structure and stoichiometry BLTO was detected by the analysis of energy dispersive spectrometry.     

Formation and properties of the Fe<Subscript>8</Subscript>V<Subscript>10</Subscript>W<Subscript>16–x</Subscript>Mo<Subscript>x</Subscript>O<Subscript>85</Subscript> type solid solution

Solid solution phases of a formula Fe₈V₁₀W_16–xMo_xO₈₅ where 0≤x≤4, have been obtained, possessing a structure of the compound Fe₈V₁₀W₁₆O₈₅. It was found on the base of XRD and DTA investigations that these solution phases melted incongruently, with increasing the value of x, in the temperature range from 1108 (x=0) to 1083 K (x=4) depositing Fe₂WO₆ and WO₃. The increase of the Mo⁶⁺ ions content in the crystal lattice of Fe₈V₁₀W₁₆O₈₅ causes the lattice parameters a=b contraction with cbeing almost constant. IR spectra of the Fe₈V₁₀W_16–xMo_xO₈₅ solid solution phases have been recorded.     

The reaction between [RuCl<Subscript>2</Subscript>(PPh<Subscript>3</Subscript>)<Subscript>3</Subscript>] and hydroxyquinoline carboxylic acid

The reactions of [RuCl₂(PPh₃)₃] with 8-hydroxy-2-methyl-quinoline-7-carboxylic acid was examined, and a novel ruthenium(II) complex—[Ru(PPh₃)₂(C₅H₈NO)₂]—was obtained. The compound was studied by IR, UV–vis spectroscopy, and X-ray crystallography. The molecular orbital diagram of the complex was calculated with the density functional theory (DFT) method. The spin-allowed singlet–singlet electronic transitions of the compound were calculated using the time-dependent DFT method, and the UV–vis spectrum of the compound was discussed, on this basis. The luminescence property of the [Ru(PPh₃)₂(C₅H₈NO)₂]was examined.     

LaNi<Subscript>0.5</Subscript>Ti<Subscript>0.5</Subscript>O<Subscript>3</Subscript>/CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript>-based sensor for sensitive determination of paracetamol

A novel electrochemical sensor based on LaNi_0.5Ti_0.5O₃/CoFe₂O₄ nanoparticle-modified electrode (LNT–CFO/GCE) for sensitive determination of paracetamol (PAR) was presented. Experimental conditions such as the concentration of LNT–CFO, pH value, and applied potential were investigated. Under the optimum conditions, the electrochemical performances of LNT–CFO/GCE have been researched on the oxidation of PAR. The electrochemical behaviors of PAR on LNT–CFO/GCE were investigated by cyclic voltammetry. The results showed that LNT–CFO/GCE exhibited excellent promotion to the oxidation of PAR. The over-potential of PAR decreased significantly on the modified electrode compared with that on bare GCE. Furthermore, the sensor exhibits good reproducibility, stability, and selectivity in PAR determination. Linear response was obtained in the range of 0.5 to 901 μM with a detection limit of 0.19 μM for PAR.     

Phase formation in the FeVO<Subscript>4</Subscript>–Co<Subscript>3</Subscript>V<Subscript>2</Subscript>O<Subscript>8</Subscript> system

Phase relations in the solid state in the FeVO₄–Co₃V₂O₈ system, in the whole range of components concentration have been studied. It was found that the composition of the phase of the howardevansite type structure, formed in the investigated system, corresponds with the Co_2.616Fe_4.256V₆O₂₄ formula. The phase of the lyonsite type structure has a homogeneity range with the Co_3+1.5xFe_4–xV₆O₂₄ formula (0.476 formula (0.476<x<1.667). The melting temperature and the volume of the unit cell of the lyonsite type structure phase increases together with the rise of cobalt quantity contained in it. Basing on the results of the DTA and XRD measurements a phase diagram of the FeVO_4–Co₃V₂O₈ system up to the solidus line was constructed.     

Crystal structure of Li(H<Subscript>2</Subscript>O)<Subscript>3</Subscript>[GaEdta]

The ethylenediaminetetraacetate complex Li(H₂O)₃[Ga(Edta)] was synthesized and its crystal structure composed of octahedral (Ga(Edta)⁻ anions connected to the Li(H₂O)₃⁺ ion through the oxygen atom was studied. Five of the six hydrogen atoms of water molecules are involved in weak hydrogen bonds with the oxygen atoms of four Ga(Edta)⁻ complexes, the complex anion is hydrogen-bonded to five water molecules. In addition, shortened contacts C(221)–H(22A)…O(112) between the Ga(Edta)⁻ anions were found. As a result, the molecular packing in the crystal is determined by the three-dimensional lace of hydrogen bonds. The results are compared with published data for the lithium salts of Bi(III), Sb(III), Fe(III), Ni(II), and Hg(II) ethylenediaminetetraacetates.     

Investigation of synthesis and microstructure of bismuth titanates with TiO<Subscript>2</Subscript> rich compositions

Preliminary examinations regarding formation of bismuth titanates in a part of Bi₂O₃—TiO₂ system rich with TiO₂ have been carried out. Bismuth titanates have been synthesized from mixtures of Bi₂O₃ and TiO₂ (anatase) by the conventional solid-state method at the temperatures ranged from 1273 to 1473 K. Differential thermal analysis (DTA), powder X-ray diffraction (XRD) and scanning electron microscopy (SEM) have been used to study the formation of bismuth titanates. The following compounds have been achieved: Bi₄Ti₃O₁₂, Bi₂Ti₂O₇ and Bi₂Ti₄O₁₁. Existence of controversial bismuth titanate of formula Bi₂Ti₃O₉ in the Bi₂O₃—TiO₂ system has not been confirmed.     

Synthesis of three-layered titanates BaLn<Subscript>2</Subscript>Ti<Subscript>3</Subscript>O<Subscript>10</Subscript> in systems with coprecipitated hydroxocarbonates

The synthesis of three-layered titanates BaLn₂Ti₃O₁₀ (Ln = La, Nd, Sm) in systems with coprecipitated hydroxocarbonates was studied. It was established that they are formed through an intermediate phase with a defective perovskite structure followed by its transformation into the three-layered structure by the ordering of vacancies and rare-earth element and barium atoms and subdivision into three-layered blocks. __________ Translated from Teoreticheskaya i éksperimental’naya Khimiya, Vol. 43, No. 6, pp. 349–353, November–December, 2007.     

Electrical conductivity studies in the system Li<Subscript>2</Subscript>TiO<Subscript>3</Subscript>-Li<Subscript>1.33</Subscript>Ti<Subscript>1.67</Subscript>O<Subscript>4</Subscript>

Electrical conductivity in the monoclinic Li₂TiO₃, cubic Li_1.33Ti_1.67O₄, and in their mixture has been studied by impedance spectroscopy in the temperature range 20–730 °C. Li₂TiO₃ shows low lithium ion conductivity, σ₃₀₀≈10^–6 S/cm at 300 °C, whereas Li_1.33Ti_1.67O₄ has 3×10^–8 at 20 °C and 3×10^–4 S/cm at 300 °C. Structural properties are used to discuss the observed conductivity features. The conductivity dependences on temperature in the coordinates of 1000/T versus log_e(σT) are not linear, as the conductivity mechanism changes. Extrinsic and intrinsic conductivity regions are observed. The change in the conductivity mechanism in Li₂TiO₃ at around 500–600 °C is observed and considered as an effect of the first-order phase transition, not reported before. Formation of solid solutions of Li_{2– x} Ti_{1+ x} O₃ above 900 °C significantly increases the conductivity. Irradiation by high-energy (5 MeV) electrons causes defects and the conductivity in Li₂TiO₃ increases exponentially. A dose of 144 MGy yields an increase in conductivity of about 100 times at room temperature. Electronic Publication     

Preparation and characterization of ZrWMoO<Subscript>8</Subscript> powders with different morphologies

ZrWMoO₈ powders with different morphologies were obtained using ammonium tungstate, molybdate tungstate and zirconium tungstate as the starting materials by dehydrating the precursor ZrWMoO₇(OH)₂(H₂O)₂. The precursor was studied by thermo-gravimetric and differential scanning calorimetry (TG-DSC). The influence of the gelling agents (HCl, HClO₄, HNO₃, H₂SO₄ and H₃PO₄) on the crystallization process and crystal morphology of the products prepared was investigated by X-ray powder diffraction (XRD), scanning electron micrograph (SEM) and X-ray fluorescence spectrometer (XRF). Results showed that the morphology of the ZrWMoO₈ particles can be simply adjusted by changing the gelling agents, and the thermal expansion coefficients of cubic ZrWMoO₈ prepared in HCl solution are −3.84 × 10⁻⁶ K⁻¹ from 100°C to 700°C. __________ Translated from Chemical Journal of Chinese University, 2007, 28(3): 397–401 [译自: 高等学校化学学报]     

Electron interactions in the (η<Superscript>2</Superscript>-C<Subscript>60</Subscript>)Pd[P(Ph<Subscript>2</Subscript>)C<Subscript>5</Subscript>H<Subscript>4</Subscript>]<Subscript>2</Subscript>Fe complex

The electronic structure of the (η²-C₆₀)Pd[P(Ph₂)C₅H₄]₂Fe complex was calculated by the “hybrid” B3LYP method. Comparison of the experimental X-ray emission C-Kα spectrum and theoretical spectrum of the compound demonstrated that the electron interactions between the C₆₀ core, palladium atom, and organometallic fragment are described correctly in the framework of the quantum chemical method used. The electronic structure of the organometallic fullerene complex can be presented as a set of blocks of orbitals corresponding to different types of chemical bond. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 12, pp. 2640–2644, December, 2005.     

Fabrication and characterization of TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript> composite nanoparticles and polyurethane/(TiO<Subscript>2</Subscript>–SiO<Subscript>2</Subscript>) nanocomposite films

TiO₂–SiO₂ composite nanoparticles were prepared by a sol–gel process. To obtain the assembly of TiO₂–SiO₂ composite nanoparticles, different molar ratios of Ti/Si were investigated. Polyurethane (PU)/(TiO₂–SiO₂) hybrid films were synthesized using the “grafting from” technique by incorporation of modified TiO₂–SiO₂ composite nanoparticles building blocks into PU matrix. Firstly, 3-aminopropyltriethysilane was employed to encapsulate TiO₂–SiO₂ composite nanoparticles’ surface. Secondly, the PU shell was tethered to the TiO₂–SiO₂ core surface via surface functionalized reaction. The particle size of TiO₂–SiO₂ composite sol was performed on dynamic light scattering, and the microstructure was characterized by X-ray diffraction and Fourier transform infrared. Thermogravimetric analysis and transmission electron microscopy (TEM) employed to study the hybrid films. The average particle size of the TiO₂–SiO₂ composite particles is about 38 nm when the molar ratio of Ti/Si reaches to1:1. The TEM image indicates that TiO₂–SiO₂ composite nanoparticles are well dispersed in the PU matrix.     

Supramolecular structure organization and the biological properties of [Co(DH)<Subscript>2</Subscript>(PP)<Subscript>2</Subscript>][BF<Subscript>4</Subscript>]

The coordination compound [Co(DH)₂(PP)₂][BF₄]₂ · 2H₂O (DH⁻ is the dimethylglyoxime residue, PP is nicotinamide) was synthesized and studied by X-ray diffraction. The equatorial plane of the octahedral Co(III) complex contains two DH⁻ residues combined by intramolecular hydrogen bonds O-H…O, while the apical positions are occupied by two PP molecules. A method for the optimal use of the complex for enhancement of the biosynthesis of standard and acid-stable amylases of the micromycete Aspergillus niger 33–19 CNMN FD 02A and lipases of the micromycete Rhizopus arrhizus Fischer CNMN FD 03L was depeloped. The introduction of the complex in a concentration of 1–5 mg/l into the culture medium of Aspergillus niger 33-19 CNMN FD 02A reduces the process cycle by 24 h. The stimulating effect of the introduction of the complex (5 mg/l) into the culture medium of the Rhizopus arrhizus Fischer CNMN FD 03L strain is 55.5%.