Investigation of ZnO nanorods synthesized by a solvothermal method, using Al-doped ZnO seed films

ZnO nanorods were successfully grown on common glass substrates using a simple solvothermal method via the precursors of zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) and Hexamethylenetetramine (C₆H₁₂N₄) with equal molar concentration at 0.01 mol/l, 0.025 mol/l, 0.05 mol/l, and 0.075 mol/l. The ZnO nanorods were characterized by X-ray diffraction (XRD), Scanning electron microscopy, UV-Vis absorption spectrophotometer and photoluminescence (PL) spectrometer. XRD results indicated that all the ZnO nanorods were preferentially grown along [0 0 0 1] direction (c-axis). With an increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the diffraction intensity of ZnO nanorod along c-axis also increased. Scanning electron microscopy images showed that the well-faceted hexagonal ZnO nanorods were grown vertically from the common glass substrates. In addition, with the increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the exciton band of ZnO nanorods determined by UV-Vis absorption spectra gradually became narrow and the intensity of exciton band also remarkably augmented. Photoluminescence spectra showed that with the increase of Zn(CH₃COO)₂·2H₂O and C₆H₁₂N₄ concentration, the position of emission peak of ZnO nanorod blue-shifts towards shorter wavelength in UV region and the luminescence intensity remarkably enhances in visible emission range (470-630 nm).     

Unique properties of polyaniline in the presence of applied magnetic field and ferric chloride

Fe-contained polyaniline (abbreviated as PANI–Fe) was prepared by chemical oxidation of aniline with ammonium peroxydisulfate oxidant in 0.5 mol dm⁻³ HCl and an adequate content of FeCl₃·6H₂O solution in the presence of an applied magnetic field at room temperature. The X-ray photoelectron spectroscopy (XPS) and UV–vis and FTIR spectra suggest that there is an interaction between FeCl₃ and PANI chains, but PANI–Fe backbone is essentially identical with that of parent polyaniline. The electron paramagnetic resonance (EPR) spectrum shows that there were unpaired electrons in PANI–Fe synthesized in the presence of an applied magnetic field, the spin density and the conductivity of which are 7.308 × 10²⁰ spins g⁻¹ and 0.891 S cm⁻¹, respectively. The plot of magnetization (M) vs. the applied magnetic field (H) displays that the PANI–Fe possesses soft ferromagnetic behavior at room temperature. The results of cyclic voltammogram show that the PANI–Fe film is of excellent electrochemical activity.     

The production of flower-like NiFe2O4 superstructures consisting of nanosheets via the thermolysis of a heterometallic oxo-centered trinuclear complex

Flower-like NiFe₂O₄ superstructures consisting of nanosheets have been successfully synthesized by direct thermolysis of a heterometallic oxo-centered trinuclear complex [NiFe₂O(CH₃COO)₆(H₂O)₃·2H₂O] (NiFe-HOTC) at 400 °C for 6 h in a horizontal tube furnace. The composition and structure of the products were investigated by X-ray diffraction (XRD) and infrared spectra (IR). XRD analysis revealed a pure ferrite phase with high crystallinity. Morphological investigation by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) showed NiFe₂O₄ flowers with average diameter varying from 0.5 to 3 μm consist of nanosheets with average edge length in the range of 60-300 nm and thickness of about 30 nm. Furthermore, energy dispersive X-ray analysis (EDX) demonstrated that the atom ration of Ni, Fe and O is 1:2:4. In addition, magnetic measurements showed that the obtained flower-like NiFe₂O₄ are ferromagnetic at room temperature.     

Neptunium(VI) and Plutonium(VI) Pyrazine-2-carboxylates

New Np(VI) and Pu(VI) pyrazine-2-carboxylates isostructural with the uranyl complex [UO₂ · (C₄H₃N₂COO)₂(H₂O)] · 2H₂O were synthesized from aqueous solutions. The unit cell parameters of [NpO₂ · (C₄H₃N₂COO)₂(H₂O)] · 2H₂O and [PuO₂(C₄H₃N₂COO)₂(H₂O)] · 2H₂O were calculated from the powder X-ray patterns. The thermal behavior of the complexes suggests that the Np(VI) compound contains superstoichiometric water molecules, which are also manifested in the IR spectrum. The absorption spectra of the compounds show that the pyrazinecarboxylic acid anion is a strong complexing agent with respect to Np(VI) and Pu(VI).__________Translated from Radiokhimiya, Vol. 47, No. 1, 2005, pp. 35–38.Original Russian Text Copyright © 2005 by Andreev, Budantseva, Perminov, Fedoseev.     

Dielectric and electric studies of the [N(CH3)4][N(C2H5)4]ZnCl4 compound at low temperature

The [N(CH₃)₄][N(C₂H₅)₄]ZnCl₄ compound was prepared and characterized by electrical technique. The temperature dependence of the dielectric permittivity shows that this compound is ferroelectric below T = 268 K. The two semi-circles observed in the complex impedance identify the presence of the grain interior and grain boundary contributions to the electrical response in the material. The equivalent circuit is modeled by a combination series of two parallel R_P–CPE circuits. The frequency dependent conductivity is interpreted in term of Jonscher's law. The modulus plots can be characterized by the empirical Kohlrausch–Williams–Watts (K.W.W.) function: ?(t) = exp [(−t/τ)^β]. The temperature dependence of the alternative current conductivity (σ_p), direct current conductivity (σ_dc) and the relaxation frequency (f_p) confirm the presence of the ferroelectric–paraelectric phase transition.     

Crystal structure of Rb3[UO2(CH3COO)3]2[UO2(CH3COO)(NCS)2(H2O)]

The structure of Rb₃[UO₂(CH₃COO)₃]₂[UO₂(CH₃COO)(NCS)₂(H₂O)] was studied by single crystal X-ray diffraction. The compound crystallizes in the monoclinic system with the unit cell parameters (at 100 K) a = 18.387(3), b = 16.398(3), c = 12.460(2) Å, β = 92.837(5)^°, V = 3752.4(11) ų, space group C2/c, Z = 4, R = 0.0390. The uranium-containing structural units of the crystals are isolated mononuclear groups [UO₂(CH₃COO)₃]^? and [UO₂(CH₃COO)(NCS)₂(H₂O)]^?, belonging to crystal-chemical groups AB ₃ ⁰¹ and AB⁰¹M ₃ ¹ (A = UO ₂ ²⁺ , B⁰¹ = CH₃COO^?, M¹ = NCS^? and H₂O) of uranyl complexes, respectively. The uranium-containing complexes are linked in a framework by hydrogen bonds and by electrostatic interactions with Rb⁺ cations.     

Rapid fabrication and optical properties of zinc sulfide nanocrystallines in a heterogeneous system

ZnS nanoparticles about 3 nm in size were prepared by a simple, rapid and reliable route under microwave irradiation in a heterogeneous system, using ZnAc₂·2H₂O (AcCH₃COO) and Na₂S·9H₂O as the starting materials, ethylene glycol (EG) as the medium. The product was characterized with X-ray powder diffraction (XRD), transmission electron microscopy (TEM) and ED, respectively. The optical properties of ZnS nanoparticles were studied.     

Fabrication and characterization of all-oxide heterojunction p-CuAlO2 + x/n-Zn1 − xAlxO transparent diode for potential application in “invisible electronics”

Transparent p-n heterojunction diodes have been fabricated by p-type copper aluminum oxide (p-CuAlO_2 + x) and n-type aluminum doped zinc oxide (n-Zn_1 − xAl_xO) thin films on glass substrates. The n-layers are deposited by sol-gel-dip-coating process from zinc acetate dihydrate (Zn(CH₃COO)₂·2H₂O) and aluminum nitrate (Al(NO₃)₃·9H₂O). Al concentration in the nominal solution is taken as 1.62 at %. P-layers are deposited onto the ZnO:Al-coated glass substrates by direct current sputtering process from a prefabricated CuAlO₂ sintered target. The sputtering is performed in oxygen-diluted argon atmosphere with an elevated substrate temperature. Post-deposition oxygen annealing induces excess oxygen within the p-CuAlO_2 + x films, which in turn enhances p-type conductivity of the layers. The device characterization shows rectifying current-voltage characteristics, confirming the proper formation of the p-n junction. The turn-on voltage is obtained around 0.8 V, with a forward-to-reverse current ratio around 30 at ± 4 V. The diode structure has a total thickness of 1.1 μm and the optical transmission spectra of the diode show almost 60% transmittance in the visible region, indicating its potential application in ‘invisible electronics’. Also the cost-effective procedures enable the large-scale production of these transparent diodes for diverse device applications.     

Ceramic system based on ZnO-CuO-glass

Mixtures of powders containing ZnO, (CH₃COO)₂Cu·H₂O and glass frit were obtained by freeze-drying with compositions of 99 wt.% [(100 − x) mol% ZnO + x mol% Cu²⁺ (x = 0.05, 0.5, 5.0)] + 1 wt.% G, where G is a glass powder containing 26% SiO₂, 62% PbO, 7% B₂O₃, 5% ZnO in weight. Pellets were sintered in air at 950 °C/1 h. Ceramic system based on ZnO-CuO-glass originated during heating above 425 °C. Liquid-phase sintering occurred above 850 °C. Results showed that the breakdown electric field, the nonlinearity coefficient (α), average grain size and grain boundary voltage increased; at the same time that the leakage current decreased, densification was enhanced as the Cu-contents increased from 0.05 to 5. An excess Cu-containing segregate phase was observed in ceramics containing 5.0 mol% Cu²⁺. Samples presented densities above 95% of the theoretical density of ZnO and α > 200.     

Recovery of ammonium nitrogen from the effluent of UASB treating poultry manure wastewater by MAP precipitation as a slow release fertilizer

Magnesium ammonium phosphate hexahydrate (MgNH₄PO₄·6H₂O, MAP) precipitation was studied on up-flow anaerobic sludge blanket (UASB) pretreated poultry manure wastewater in a lab-scale batch study. To recover high strength of ammonium nitrogen (NH₄⁺–N = 1318 mg/L) from UASB effluent, three combinations of chemicals including MgCl₂·6H₂O + KH₂PO₄, MgSO₄·7H₂O + NaHPO₄·7H₂O, and MgO + 85% H₃PO₄ were first applied at the stoichiometric ratio (Mg²⁺:NH₄⁺–N:PO₄³⁻–P = 1:1:1) and at different pH levels ranging from 4.45 to 11. Preliminary test results indicated that maximum NH₄⁺–N removal, as well as maximum chemical oxygen demand (COD) and color reductions, were obtained as 85.4%, 53.3% and 49.8% at pH 9.0 with the addition of MgCl₂·6H₂O + KH₂PO₄, respectively. The paired experimental data obtained from batch studies were statistically evaluated by a non-parametric Mann–Whitney test and a two-sample t-test. Based on the previous results, another batch experiments were then performed at pH 9.0 using MgCl₂·6H₂O + KH₂PO₄ for different molar ratios applied as overdose (1.2:1:1, 1.5:1:1, 1:1:1.2, 1:1:1.5) and underdose (0.5:1:1, 0.8:1:1, 1:1:0.5, 1:1:0.8). In the final step, the fertility of the MAP precipitate as struvite was also tested on the growth of three test plants including purslane (Portulaca oleracea), garden cress (Lepidum sativum) and grass (Lolium perenne). Findings of this experimental study clearly confirmed the recovering of NH₄⁺–N from UASB pretreated poultry manure wastewater by MAP precipitation, and also the application of recovered MAP sludge as a valuable slow release fertilizer for agricultural use.     

Preparation and photoluminescence properties of functionalized silica materials incorporating europium complexes

In the present work, the surface of the Eu-BTC = [Eu(EMA)(H₂O)₂], [Eu(TLA)(H₂O)₄] and [Eu(TMA)(H₂O)₆] complexes (EMA = 1,2,3-benzenetricarboxylate, TLA = 1,2,4-benzenetricarboxylate and TMA = 1,3,5-benzenetricarboxylate) was modified using 3-aminopropyltriethoxysilane (APTES) by a new microwave assisted method that proved to be simple and efficient. According to our observations, the most efficient luminescence is the material based on APTES incorporating [Eu(TMA)(H₂O)₆] complexes, denoted as Eu-TMA-Si, shows the highest emission efficiency. Therefore, it is proposed as a promising material for molecular conjugation in clinical diagnosis.     

Control of carrier concentration of p-type transparent conducting CuScO2(0001) epitaxial films

Excess oxygen and 1-at% Mg co-doped CuScO₂[3R](0001) epitaxial films were prepared on a-plane sapphire substrates by combining two-step deposition and post-annealing techniques. The optical and electrical transport properties of the co-doped epitaxial films were compared with those of the CuScO₂[3R](0001) epitaxial films. No significant increase in optical absorption was observed in the co-doped epitaxial films, and the energy gap for direct allowed transition was estimated at 3.7 eV. The carrier concentration of CuScO₂[3R](0001) epitaxial films was controlled from ~ 10¹⁶ cm^- 3 to ~ 10¹⁸ cm^- 3 at room temperature by adjusting the excess oxygen and Mg co-doping. The electrical conductivity, carrier concentration, and Hall mobility of the most conductive film were 3.6 × 10^- 2 Scm^- 1, 8.5 × 10¹⁷ cm^- 3 and 2.6 × 10^- 1 cm²V^- 1 s^- 1 at room temperature, respectively. The temperature dependence of the electrical transport properties of the film exhibited semiconducting characteristics, and the activation energy estimated from the temperature dependence of the carrier concentration was 0.50 eV.     

Synthesis of PbTe thermoelectric materials by alkaline reducing chemical routes

Binary PbTe thermoelectric compounds have been successfully synthesized by alkaline reducing solvothermal, hydrothermal and low-temperature aqueous chemical routes using Pb(CH₃COO)₂·3H₂O and pure tellurium as precursors, and NaBH₄ as the reductant. Compared to PbTe powders synthesized by solvothermal and hydrothermal routes, smaller PbTe nanopowders of about 20 nm have been obtained by low-temperature aqueous chemical route. Possible formation mechanisms of PbTe were discussed.     

Giant electrical conductivity enhancement in BaO–V2O5–Bi2O3 glass by nanocrystallization

The effects of the annealing of 20BaO–30V₂O₅–50Bi₂O₃ glass on the structural and electrical properties were studied by scanning electron micrographs (SEM), X-ray diffraction (XRD), differential scanning calorimeter (DSC) density (d) and dc conductivity (σ). The XRD and SEM observations have shown that the sample under study undergoes structural changes: from amorphous at the beginning, to partly crystalline after nanocrystallization at crystallization temperature (T_c) for 1 h and to colossal crystallization after the annealing at the same temperature for 24 h. The average size of these grains after nanocrystallization at T_c for 1 h was estimated to be about 25–35 nm. However, the glass heat treated at T_c = 580 °C for 24 h the microstructure changes considerably. The nanomaterials obtained by nanocrystallization at T_c for 1 h exhibit giant improvement of electrical conductivity up to four order of magnitude and better thermal stability than the as-received glass. The major role in the conductivity enhancement of this nanomaterial is played by the developed interfacial regions “conduction tissue” between crystalline and amorphous phases, in which the concentration of V⁴⁺–V⁵⁺ pairs responsible for electron hopping is higher than inside the glassy matrix. The annealing at T_c for 24 h leads to decrease of the electronic conductivity. This phenomena lead to disappearance of the abovementioned “conduction tissue” for electrons and substantial reduction of electronic conductivity. The high temperature (above θ/2) dependence of conductivity could be qualitatively explained by the small polaron hopping (SPH) model. The physical parameters obtained from the best fits of this model are found reasonable and consistent with the glass compositions.     

Characterization of AgBiS2 nanostructured flowers produced by solvothermal reaction

AgBiS₂ nanostructured flowers were produced from CH₃COOAg, Bi(NO₃)₃.5H₂O and thiosemicarbazide (NH₂CSNHNH₂) using different solvents [ethylene glycol (EG), water (H₂O), polyethylene glycol with molecular weight of 200 (PEG200), and propylene glycol (PG)] in Teflon-lined stainless steel autoclaves. The phase and purity were detected using X-ray diffraction (XRD), controlled by the solvents. The product was purified AgBiS₂ produced by the 200 °C and 24 h reaction in EG, corresponding to selected area electron diffraction (SAED) and simulation patterns. Scanning and transmission electron microscopies (SEM and TEM) revealed the formation of nanostructured flowers — enlarged by the increase in the lengths of time and temperature. Their photoluminescence (PL) emissions were detected at the same wavelength of 382 nm (3.24 eV), although they were produced under different conditions.     

Growth and characterization of Ba(Cd1/3Ta2/3)O3 thin films

We have synthesized stoichiometric Ba(Cd_1/3Ta_2/3)O₃ [BCT] (100) dielectric thin films on MgO (100) substrates using Pulsed Laser Deposition. Over 99% of the BCT film was found to be epitaxial [BCT (100) || MgO (100) and BCT (010) || MgO (010)] when grown with an elevated substrate temperature of 635 °C, an enhanced oxygen pressure of 53 Pa and a Cd-enriched BCT target with a 1 mol BCT: 1.5 mol CdO composition. A dielectric constant of 32 was inferred from low-frequency capacitance measurements of a planar interdigital metal pattern. Analysis of ultra violet optical absorption results indicates that BCT has a bandgap of 4.9 eV; while the interference pattern in the visible range is consistent with a refractive index of 2.1. Temperature-dependent electrical measurements indicate that the BCT films have a room temperature conductivity of 3 × 10^− 12 Ω^− 1 cm^− 1 with a thermal activation energy of 0.7 eV. A mean particle size of ~ 100 nm and a root mean square surface roughness of 5 to 6 nm were measured using Atomic Force Microscopy.     

Preparation and characterization of CuO nanorods by thermal decomposition of CuC2O4 precursor

Synthesis of copper oxide (CuO) nanorods was achieved by thermal decomposition of the precursor of CuC₂O₄ obtained via chemical reaction between Cu(CH₃COO)₂·H₂O and H₂C₂O₄·2H₂O in the presence of surfactant nonyl phenyl ether (9)/(5) (NP-9/5) and NaCl flux. Transmission electron microscopy (TEM), X-ray diffraction (XRD), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), selected-area electron diffraction (SAED) and high-resolution TEM (HRTEM) were used to characterize the structure features and chemical compositions of the as-made nanorods. The results showed that the as-prepared nanorods is composed of CuO with diameter of 30-100 nm, and lengths ranging from 1 to 3 μm. The mechanism of formation of CuO nanorods was also discussed.     

Ethanol-thermal synthesis of Cd1−xZnxS nanoparticles with enhanced photodegradation of 4-chlorophenol

Cd_1−xZn_xS nanoparticles were prepared by a one-pot solvothermal process from Zn(CH₃COO)₂, Cd(CH₃COO)₂ and NaS₂CNEt₂·3H₂O (sodium diethyldithiocarbamate, DDTC). The Cd_1−xZn_xS nanoparticles were characterized by X-ray powder diffraction, transmission electron microscope and high-resolution transmission electron microscope equipped with an energy-dispersive X-ray spectrometer. The absorption spectra of the Cd_1−xZn_xS nanoparticles can be tuned into visible region by modulating stoichiometric ratio between Zn and Cd. With the increase of Zn content, the Cd_1−xZn_xS nanoparticles showed an enhanced photocatalytic activity on degradation of 4-chlorophenol. The Cd_1−xZn_xS prepared under the optimal experimental condition (initial Zn/Cd = 3:1, 210 °C, 24 h, in ethanol) possessed the best photocatalytic activity. The conversion ratio could reach up to 84% after 12 h under irradiation of visible light for Cd_1−xZn_xS prepared in ethanol, which was obviously superior to those of products prepared in water. These results showed that both crystallinity and synthetic medium were responsible for the enhanced photocatalytic activity for 4-chlorophenol.     

Formation and characterization of thin films from phthalocyanine complexes: An electrosynthesis study using the atomic-force microscope

(μ-Cyano)(phthalocyaninato)metal(III) [PcMCN]_n species with a central transition metal ion, such as Fe(III) and Co(III), were used to prepare molecular films on a highly oriented pyrolytic graphite electrode substrate by using the cyclic voltammetry technique. In order to investigate the influence of the ligand on the film properties, 1,8-dihydroxyanthraquinone and 2,6-dihydroxyanthraquinone as bivalent ligands were employed. The structure of the molecular materials was analyzed by infrared spectroscopy. The in situ film formation, texture, composition and conductivity of each film were further investigated using atomic force microscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy and the four-probe technique, respectively. The [PcMCN]_n complexes provided conductive films with an electrical conductivity of 1 × 10^− 6 Ω^− 1 cm^− 1 at 298 K.     

Cermet-type hydrogen separation membrane obtained from fine particles of high temperature proton-conductive oxide and palladium

A mixed ionic and electronic conducting hydrogen separation membrane, which consisted of proton-conductive oxide and metallic palladium, was fabricated. A porous alumina tube was employed as a support, and proton-conductive oxide particles were introduced into a microporous top layer of the support by an impregnation method. Palladium particles were deposited into the same porous layer by chemical vapor deposition. Hydrogen permeated preferentially via the membrane thus obtained with a hydrogen permeance (PH₂) of 1.2 × 10^− 9 mol·m^− 2·s^− 1·Pa^− 1 at 873 K. Selectivity for hydrogen (PH₂/PN₂) increased with the operating temperature due to an increase in proton conductivity of the membrane, and PH₂/PN₂ = 5.7 was attained at 873 K.