Large diameter MWNTs growth on iron-sprayed catalyst by CCVD method under atmospheric pressure

In this work, we have synthesized large diameter multi-walled carbon nanotubes (MWNTs), by simple catalyst chemical vapor deposition (CCVD). Fe powder was spread on quartz substrate as a catalyst by a simple method and then heated under Ar atmosphere. Carbon’s products can be synthesized by the decomposition of ethylene gas and deposition of carbon atoms on the Fe catalyst particles in Ar atmosphere at 930°C. XRD pattern, SEM and TEM images were used to investigate the characteristics, morphology and structure of carbon’s products.     

Improved charge collection efficiency of hollow sphere/nanoparticle composite TiO2 electrodes for solid state dye sensitized solar cells

The photoanodes of solid state dye sensitized solar cells (ss-DSCs) embedded with different contents of TiO₂ hollow spheres (HSs) were prepared and the photovoltaic performances were systematically characterized. TiO₂ hollow spheres were synthesized by a facile sacrificial templating method, grounded and added in different ratios to TiO₂ nanoparticle (NP) paste, from which composite HS/NP electrodes were fabricated. The composite photoanodes include hollow spheres of 300–700 nm with enhanced light scattering characteristics in visible range which leads to improved light absorption in conventional thin film electrodes of ss-DSC. By optimizing the amount of HSs in the paste, 40% improvement in efficiency was obtained in comparison to ss-DSC utilized pure NP electrodes. By increasing the fraction of HSs in the electrode the current density increased by 56% (from 2.5 to 3.9 mA cm^?2). The improved photovoltaic performance of ss-DSC is primarily due to different morphology and altered charged trap distribution in HSs in comparison to NP which leads to significant enhancement in electron transport time and electron lifetime as well as charge collection efficiency and light absorption properties.     

Characterization of ZnO:Si nanocomposite films grown by thermal evaporation

Composite films were fabricated by co-evaporating Zinc Oxide with Silicon at room temperatures. The resulting films had polycrystalline grains of Zinc Oxide whose grain size were few hundred nanometers, embedded in the silicon matrix. These nanocrystalline grains of ZnO showed good photoluminescence emission at 520 nm along with a photoluminescence emission at 620 nm being contributed by the silicon background. Thus, the nanocomposite films gave a board emission, making it a potentially useful candidate for optoelectronic devices. The photo-luminescent property of the films was found to be stable since the homgenously dispersed ZnO nanocrystals were not allowed to agglomerate by the silicon background.     

Styrene-containing Phosphine-sulfonate Ligands for Nickel-and Palladium-catalyzed Ethylene Polymerization

A series of phosphine-sulfonate ligands bearing 2-, 3-and 4-vinylphenyl on the phosphorus atom were designed, synthesized,characterized and investigated in Ni-and Pd-catalyzed ethylene polymerization. The structure of the phosphine-sulfonate Pd complex bearing2-vinylphenyl on the phosphorus atom showed 2,1-insertion for the 2-vinyl group. The phosphine-sulfonate Ni complex bearing 2-vinylphenyl resulted in significantly increased thermal stability and polyethylene molecular weights(Mn=3.69×104 g·mol-1 at 80 °C) versus the counterparts bearing 3-/4-vinyl groups as well as previously reported phosphine-sulfonate Ni complexes bearing bulky biaryl substituents.     

Combination of dispersive liquid-liquid microextraction with flame atomic absorption spectrometry using microsample introduction for determination of lead in water samples

The dispersive liquid-liquid microextraction (DLLME) was combined with the flame atomic absorption spectrometry (FAAS) for determination of lead in the water samples. Diethyldithiophosphoric acid (DDTP), carbon tetrachloride and methanol were used as chelating agent, extraction solvent and disperser solvent, respectively. A new FAAS sample introduction system was employed for the microvolume nebulization of the non-flammable chlorinated organic extracts. Injection of 20 μL volumes of the organic extract into an air-acetylene flame provided very sensitive spike-like and reproducible signals.Some effective parameters on the microextraction and the complex formation were selected and optimized. These parameters include extraction and disperser solvent type as well as their volume, extraction time, salt effect, pH and amount of the chelating agent. Under the optimized conditions, the enrichment factor of 450 was obtained from a sample volume of 25.0 mL. The enhancement factor, calculated as the ratio of the slopes of the calibration graphs with and without preconcentration, which was about 1000. The calibration graph was linear in the range of 1-70 μg L⁻¹ with a detection limit of 0.5 μg L⁻¹. The relative standard deviation (R.S.D.) for seven replicate measurements of 5.0 and 50 μg L⁻¹ of lead were 3.8 and 2.0%, respectively. The relative recoveries of lead in tap, well, river and seawater samples at the spiking level of 20 μg L⁻¹ ranged from 93.8 to 106.2%. The characteristics of the proposed method were compared with those of the liquid-liquid extraction (LLE), cloud point extraction (CPE), on-line and off-line solid-phase extraction (SPE) as well as co-precipitation, based on bibliographic data. Operation simplicity, rapidity, low cost, high enrichment factor, good repeatability, and low consumption of the extraction solvent at a microliter level are the main advantages of the proposed method.     

Smart computing approach for design and scale-up of conical spouted beds with open-sided draft tubes

Open-sided draft tubes provide an optimal gas distribution through a cross flow pattern between the spout and the annulus in conical spouted beds.The design,optimization,control,and scale-up of the spouted beds require precise information on operating and peak pressure drops.In this study,a multi-layer perceptron(MLP)neural network was employed for accurate prediction of these hydrodynamic characteristics.A relatively huge number of experiments were accomplished and the most influential dimensionless groups were extracted using the Buckingham-pi theorem.Then,the dimensionless groups were used for developing the MLP model for simultaneous estimation of operating and peak pressure drops.The iterative constructive technique confirmed that 4-14-2 is the best structure for the MLP model in terms of absolute average relative deviation(AARD%),mean square error(MSE),and regression coefficient(R²).The developed MLP approach has an excellent capacity to predict the transformed operating(MSE=0.00039,AARD%=1.30,and R²=0.76099)and peak(MSE=0.22933,AARD%=11.88,and R2=0.89867)pressure drops.     

Piperazinediium,Zr(IV) and Ce(IV) pyridine-2,6-dicarboxylates: Syntheses,characterizations, crystal structures, ab initio HF,DFT calculations and solution studies

The novel title compounds, (pipzH₂)_1.5(pydcH)₃·3.7H₂O, 1, (pipzH₂)[Zr(pydc)₃]·8H₂O, 2 and (pipzH₂)[Ce(pydc)₃]·8H₂O, 3 in which pydcH₂ is pyridine-2,6-dicarboxylic acid and pipz is piperazine were obtained in aqueous solution. The compounds were characterized by IR, ¹H NMR and ¹³C NMR spectroscopy, elemental analyses, and X-ray crystallography. Compound 1 is resulted from proton transfer between pydcH₂ and pipz. However, compounds 2 and 3 are resulted from complexation of 1 and corresponding metallic salts. Both compounds 2 and 3 contain three pyridine-2,6-dicarboxylate species as tridentate ligands, one piperazinediium as counter ion, and eight-uncoordinated water molecules in the asymmetric unit. In both structures each M(IV) is coordinated in a distorted tricapped trigonal prism geometry by three nitrogen and six oxygen atoms of carboxylate groups of three (pydc)²⁻ fragments. In the crystal structures of 1, 2 and 3, extensive O–H···O, N–H···O and C–H···O hydrogen bonds as well as electrostatic forces, C–H···π, C–O···π and π–π stacking play important roles in stabilizing structures. The geometrical parameters of the [M(pydc)₃]²⁻ anionic complexes, where M = Ce(IV), Zr(IV) have been optimized with the B3LYP method of density functional theory (DFT) and ab initio Hartree–Fock (HF) methods for comparison. In addition, we have studied the structures of (pydc)²⁻ anion and its mono and doubly protonated forms, (pydcH)⁻ and pydcH₂. The electronic properties of the anionic complexes and ligands have been investigated based on the natural bond orbital (NBO) analysis at the B3LYP method which verifies that the synergistic effect has been occurred in the title complexes. In solution study of 2, the stoichiometry and stability constant of complexation of pipz, pydc, pydc–pipz proton transfer system and Zr(IV) ion in aqueous solution were investigated by potentiometric method.     

A New Steepest Descent Differential Inclusion-Based Method for Solving General Nonsmooth Convex Optimization Problems

In this paper, we investigate a steepest descent neural network for solving general nonsmooth convex optimization problems. The convergence to optimal solution set is analytically proved. We apply the method to some numerical tests which confirm the effectiveness of the theoretical results and the performance of the proposed neural network.     

Chloride Binding by Polyammonium Receptor Molecules: 35Cl-NMR Studies

Binding of chloride anion by protonated polyamines was investigated by ³⁵Cl? NMR spectroscopy. The presence of protonated macro(poly)cyclic polyamines caused downfield shifts and significant line broadening of the ⁵³Cl? NMR signals. ³⁵Cl? NMR spectroscopy was used for complex-formation stoichiometry determination and revealed the formation of a binuclear chloride complex with the fully protonated ditopic hexaazamacrocyclic receptor 6 . ³⁵Cl? NMR spectroscopy was also applied in competition experiments between Cl? and SO₄^2? and demonstrated that the fully protonated macrocyclic hexaamine 4 forms a strong complex with SO₄^?2 with 1:1 stoichiometry.     

Sensitized extraction spectrophotometric determination of Hg(II) with dithizone after its flotation as ion-associate using iodide and ferroin

This paper describes a simple and highly selective method for the separation, preconcentration and spectrophotometric determination of extremely low concentration of mercury. The method is based on the flotation of an ion-associate of HgI₄²⁻ and ferroin between aqueous and n-heptane interface at pH 5. The ion-associate was then separated and treated with ammonia and dithizone solutions to extract only the mercury chelate with CH₂Cl₂. The measurement is feasible when the volume of the water sample containing Hg(II) was varied over 50-800 ml. Beer's law was obeyed over the concentration range of 8 × 10⁻⁹ to 1.6 × 10⁻⁷ mol l⁻¹ with an apparent molar absorptivity of 6.53 × 10⁶ l mol⁻¹ cm⁻¹ for a 500 ml aliquot of the water sample. The detection limit (n = 7) was 5.0 × 10⁻¹⁰ mol l⁻¹ and the R.S.D. (n = 5) for 8.0 × 10⁻⁷ mol l⁻¹ of Hg(II) was 3.7%. A notable advantage of the method is that the determination of Hg(II) is free from the interference of almost all cations and anions found in the environmental and waste water samples. The determination of Hg(II) in tap, synthetic sea water and human hair samples was carried out by the present method and cold vapor atomic absorption spectrometry (CV-AAS). The results were satisfactorily comparable so that the applicability of the proposed method was confirmed to the real samples.