Effect of solid inorganic salts on the formation of cubic-like aggregates of ZnSnO3 nanoparticles in solventless,organic-free reactions and their gas sensing behaviors

The effect of added solid inorganic salts on the morphology of ZnSnO₃ nanoparticle aggregates has been investigated based on solventless and organic-free reactions at ambient temperature. Cubic-like aggregates of ZnSnO₃ nanoparticles can be synthesized successfully through direct reaction of solid MOH (M⁺ = K⁺, Na⁺) with a solid mixture of ZnCl₂ and SnCl₄·5H₂O in the presence of added inorganic salt, MCl (M⁺ = K⁺, Na⁺). In contrast, irregular spherical aggregates of ZnSnO₃ nanoparticles are produced in the reactions in absence of added solid inorganic salts. The added solid inorganic salts, which play a key role for producing the cubic-like aggregates of ZnSnO₃ nanoparticles with pores of ca. 2.8 nm, may act as a substrate-template for the growth of nanocrystals and the formation of their cubic-like aggregates. Gas sensors are further constructed with the aggregates of ZnSnO₃ nanoparticles as sensing materials. The sensors made with the cubic-like aggregates (C-sensors) exhibit much higher responses to the reducing gases tested, compared to those (S-sensors) from spherical aggregates synthesized without adding inorganic substrate-template into the reaction. The approach could open a new pathway for controlling the microstructure of materials with high gas sensing functionality.     

Biomolecule-assisted synthesis of copper indium sulfide microspheres with nanosheets

Copper indium sulfide product was successfully synthesized via a mild solvothermal approach involving CuCl₂·2H₂O as the copper source, InCl₃ as the indium source, l-cysteine as the sulfur source and N,N-dimethylformamide as the reaction medium respectively at 200 °C for 12 h. Morphology, structure, and phase constituents of the as-prepared CuInS₂ powders were characterized by XRD, FE-SEM, XPS, and TEM (HRTEM). Results showed that the synthesized powder consists of microspheres made up of nanosheets and the thickness of the CuInS₂ nanosheets was found to vary from 50 to 100 nm. A possible formation mechanism was put forward and briefly discussed. The proposed solvothermal method using l-cysteine as the sulfur source offers a potential alternative avenue to prepare other ternary semiconductor nanomaterials.     

The fabrication of hollow cubic-like CuInS2 cages using Cu2O crystals as sacrificing template

Hollow cubic-like CuInS₂ cages were prepared with cubic Cu₂O nanocrystals as self-sacrificing template through solvothermal process. The formation of these hollow structures could be attributed to the migration of copper ions and the copy of cubic Cu₂O template based on the Kirkendall effect and the Ostwald ripening process. Such process and mechanism might be extended to synthesize other hollow ternary chalcogenide materials.     

A facile chemical route to α-Zn3(PO4)2·4H2O hierarchical sphere structures assembled by nanosheets

Novel α-Zn₃(PO₄)₂·4H₂O hierarchical sphere structures have been synthesized by a simple chemical method through the reaction between zinc acetate and orthophosphoric acid by using cetyltrimethylammonium bromide (CTAB) as capping reagent at room temperature. The structures and morphologies of the as-obtained products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM) and transmission electron microscopy (TEM). The influences of the synthetic parameters on the morphologies of the final products were investigated. The experimental results clearly show that both the concentration of CTAB aqueous solution and the concentration of initial reagents play important roles in the formation of the α-Zn₃(PO₄)₂·4H₂O hierarchical sphere structure. Detailed proofs indicated that the process of crystal growth was dominated by a self-assembly growth mechanism.     

A new synthesis process and characterization of three-dimensionally ordered macroporous ZrO2

A three-dimensionally ordered macroporous (3DOM) material ZrO₂ has been successfully synthesized by using ZrOC1₂·8H₂O as precursor and polystyrene beads with diameters of 480 nm as template. The merit of this process is that ZrOC1₂·8H₂O is cheaper and has a high melting point. SEM images show that precursor concentration has an important effect in fabricating 3DOM ZrO₂. The sample prepared by using the precursor solution with a concentration of 1.6 M displays a well long-ranged ordered structure and uniform pore sizes. Precursor concentration between 1.3 M and 2.0 M is considered to be the most favorable to fabricate 3DOM ZrO₂. XRD analysis indicates that the crystallinity of 3DOM ZrO₂ is monoclinic phase. Nitrogen adsorption and desorption measurements at 77.4 K show detailed pore structures of 3DOM ZrO₂.     

Local structural analysis of hopeite crystals by the EXAFS curve-fitting method

Structural analysis of hopeite crystals was performed by the extended X-ray absorption fine structure (EXAFS) curve fitting method. Two types of hopeite crystals, Zn₃(PO₄)₂·4H₂O and Zn_3-xMn_x(PO₄)₂·4H₂O which is doped by manganese, were studied. Fourier transform of EXAFS gave Zn-O bond distances of 0.146 nm for the former and 0.144 nm for the latter. The real bond distances were determined by the reverse operation of Fourier transform and curve-fitting. By this procedure, the real bond distances of Zn-O were determined to be 0.194 and 0.196 nm, respectively. These distances indicated a Zn-O bond in [ZnO₄] of tetrahedral structure. Although the Mn-O bond distance in Zn_3-xMn_x(PO₄)₂·4H₂O was found to be 0.162 nm by the Fourier transform of EXAFS, the reverse operation of Fourier transform gave a real bond distance of 0.215 nm for the Mn-O bond in the hopeite crystal. The data supported the idea that the Mn-O bond refered to [MnO₂(H₂O)₄] of the octahedral structure in the crystal. The coordination numbers of the zinc and manganese components clarified their local structure in hopeite crystals.     

Preparation of lanthanide orthophosphates by crystallisation from phosphoric acid solution

Highly crystalline solids of the composition of LnPO₄ · nH₂O (Ln = La, Ce, Pr, Nd. Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu and Y) were prepared by crystallisation from boiling phosphoric acid solution with the initial concentration 2 M/1 of H₃PO₄ and 0.02 M/1 of Ln. The number of molecules of water (n) was close to 1. The crystallisation process was completed within two hours. Scanning electron micrographs showed that the diameter of the LnPO₄ · H₂O crystalline particles was increasing within the group of elements from below 1 m (LaPO₄ · H₂O) to above 5 m (TmPO₄ · H₂O). Such large crystals of lanthanide phosphates cannot be obtained by usually applied precipitation methods. The light lanthanides (La Sm) formed clusters of shapeless particles with the tendency to form rod-like crystals. The heavy lanthanides (Ho Lu, and YPO₄ · H₂O) consisted of spherical globules. The TbPO₄ · H₂O and DyPO₄ · H₂O, formed a mixture of the spherical and rod-like crystals.     

Thermal properties and radiation damage in NaNH4XO4·2H2O single crystals (XO4=SO4,SeO4)

Differential thermal analysis (DTA) studies of NaNH₄SO₄·2H₂O, NaND₄SO₄·2H₂O, and NaNH₄SeO₄·2H₂O single crystals were performed in the temperature range of the ferroelectric-paraelectric phase transition and of the dehydration process. The first-order phase transition at the Curie point was confirmed for NaNH₄SO₄·2H₂O, whereas the transition in the isomorphous NaNH₄SeO₄·2H₂O at the Curie temperature was found to be similar to a contineous (second order) with considerable higher transition enthalpy. Dehydration process of the crystals studied was found to proceed in two stages, with maximum dehydration rates at 355 and 400K. A linear decrease in thermal energy related to the long-range ordering in NaNH₄SO₄·2H₂O crystals was observed with the dose of -cobalt-60 irradiation and discussed with respect to the radiation induced decrease in spontaneous polarization.     

Hydrothermal synthesis of CeO2 nano-octahedrons

CeO₂ nano-octahedrons were synthesized with a facile hydrothermal synthesis process where Ce(NO₃)₃·6H₂O and urea were used as a cerium resource and mineralizer respectively and no surfactant or template was applied. The effects of synthesis parameters such as reaction temperature, reaction time, as well as the dosages of Ce (NO₃)₃·6H₂O and urea were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) analysis were conducted to characterize the crystalline and morphology of the obtained CeO₂ powders. The optimal reaction condition to prepare the CeO₂ of the desired fluorite structure was established. The possible mechanism of synthesis of CeO₂ with a nano-octahedron morphology was illustrated.     

EDTA-assisted hydrothermal synthesis,characterization, and luminescent properties of YPO4·nH2O:Eu (n = 0, 0.8) microflakes and microbundles

In this paper, the YPO₄:Eu³⁺ (5%) microflakes and YPO₄·0.8H₂O:Eu³⁺ (5%) microbundles have been synthesized by a simple EDTA-assisted hydrothermal method. The X-ray powder diffraction (XRD), thermogravimetric and differential thermal analysis (TG/DTA), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM) and photoluminescence (PL) were employed to characterize the as-obtained products. It was found that the composition of the product could be changed from YPO₄:Eu³⁺ (5%) to YPO₄·0.8H₂O:Eu³⁺ (5%) with a further increase in the amount of EDTA 0.5–1.0 g. The YPO₄:Eu³⁺ (5%) presented the pure tetragonal phase and flake-like microstructure, while the YPO₄·0.8H₂O:Eu³⁺ (5%) exhibited the hexagonal phase and bundle-like morphology. The possible formation mechanisms of the two architectures were put forward on the basis of different EDTA amount-morphology experiments. A detailed investigation on the photoluminescence of YPO₄·nH₂O:Eu³⁺ (5%) different samples indicated that the luminescent properties of products were strongly dependent on the compositions, morphologies, coordination environment and crystal field symmetry.     

Red light from ZrO2:Eu nanostructures

Zirconia nanocrystals doped with europium ions were developed envisaging optical applications. The nanostructures were produced using zirconyl nitrate (ZrO(NO₃)₂·H₂O) and europium nitrate (Eu(NO₃)₃·5H₂O) as cation precursors, and urea (C₂H₅NO₂) as the fuel, by the combustion synthesis process. The lanthanide-doped nanostructures were characterized by X-ray diffraction, transmission electron microscopy, Raman spectroscopy and photoluminescence. X-ray diffraction revealed the presence of tetragonal and monoclinic crystalline ZrO₂ phases. The latter was found to be a minority phase as identified by Raman and corroborated by the observed europium luminescence when compared to the intraionic emission in crystalline tetragonal fibres grown by the laser floating zone technique. Bright red europium luminescence is observed at room temperature when the combustion synthesized zirconia powders are excited with ultraviolet radiation. The spectroscopic properties of the europium ions in the powders are ascertained by comparing combined excitation–emission measurements with those from crystalline fibres.     

Conversion of V2O5·xH2O into orthorhombic V2O5 single-crystalline nanobelts

Orthorhombic V₂O₅ single-crystalline nanobelts have been synthesized by hydrothermal treating V₂O₅·xH₂O precipitate derived from aqueous solution of V₂O₅ and H₂O₂. The synthetic method is facile, fast, environmental friendly, and easy to scale up. The V₂O₅ single-crystalline nanobelts are 30-80 nm in width, 30-40 nm in thickness, and lengths up to several tens of micrometers. The V₂O₅·xH₂O precursor is crucial for the formation of orthorhombic V₂O₅ single-crystalline nanobelts. The influences of synthetic parameters, such as reaction time and reaction temperature, on the crystal structures and morphologies of the resulting products have been investigated. Time-dependent experiments show that V₂O₅·xH₂O are dehydrated gradually and converted into orthorhombic V₂O₅ single-crystalline nanobelts. High reaction temperature also favors the formation of orthorhombic V₂O₅ nanobelts.     

Cyclic microwave-assisted spray synthesis of nanostructured MnWO4

MnWO₄ with nano-plates in flower-like clusters was produced from the mists of the solutions containing MnCl₂·4H₂O and Na₂WO₄·2H₂O at different pH values by 300-900 W cyclic microwave radiation. The phase was detected by XRD and SAED, and was in accordance with that of the simulation. The flowers were characterized using SEM and TEM, and their lattice planes using HRTEM. The vibration spectra were characterized using Raman and FTIR spectrometers. Their photoluminescence is at 409-420 nm.     

Self-assembly growth of BiFeO3 powders prepared by microwave-hydrothermal method

With FeCl₃·6H₂O and Bi(NO₃)₃·5H₂O powder as raw materials and KOH as a mineralizer, the pure phase BiFeO₃ (BFO) powder was synthesized by microwave-hydrothermal (MH) method at 200 °C, with the reaction time as little as 30 min. The range of preparing the BFO powders had been summarized. The field emission scanning electron microscopy (FE-SEM) images revealed that the little BFO plate grew together forming rock sugar-like BFO powders, and then they grew further to form the mussel-like BFO powders. The transmission electron microscope (TEM) images also improved the self-assembly growth of BFO powders. The X-ray diffraction (XRD), the high resolution transmission electron microscopy (HRTEM) and the selected area electron diffraction (SAED) results indicated that the BFO powders grew along the [110] and [104] crystal orientation. The B-H loops of BFO indicated that the weak magnetism existed in the pure phase BFO powders.     

Synthesis and characterization of stable and crystalline Ce0.6Y0.4O1.8 nanoparticle sol

Ce_0.6Y_0.4O_1.8 (40YCO) nanoparticle sol was synthesized via the hydrolysis of a Ce-Y-triethanolamine (TEA) complex derived from the reaction of hydrate cerium (III) nitrate (Ce(NO₃)₃·6H₂O), yttrium nitrate (Y(NO₃)₃·6H₂O) and TEA in alcohol solution at room temperature. The resultant sol possessed excellent UV shielding ability and high transparency in visible light region, and can be stable for one month. Transmission electron microscopy (TEM) showed a particle size distribution of 4.1 ± 0.7 nm for 40YCO. X-ray diffraction (XRD) as well as selected area electron diffraction (SAED) gave evidence that the as-synthesized nanoparticles were well crystalline. The formation of a solid solution was monitored by XRD and ICP-MS. Moreover, zeta potential measurement and infrared spectra were employed to study the YCO particles.     

Characterization of MMoO4 (M = Ba, Sr and Ca) with different morphologies prepared using a cyclic microwave radiation

Scheelite molybdates (MMoO₄, M = Ba, Sr and Ca) were successfully prepared by the reactions of M(NO₃)₂·2H₂O and Na₂MoO₄·2H₂O in propylene glycol and NaOH using a microwave radiation. The phases were detected using XRD and SAED. TEM analysis revealed the presence of micro-sized bi-pyramids with a square base, nano-sized particles in clusters, and dispersed nano-sized particles for BaMoO₄, SrMoO₄ and CaMoO₄, respectively. Diffraction patterns of the bi-pyramids were simulated, and are in accord with the experimental results. Raman and FTIR spectra provide the evidence of scheelite structure with Mo-O stretching vibration in MoO₄²⁻ tetrahedrons at 742-901 cm^− 1.     

3D navicular ceria micro/nanocomposite structure with multi-layered arrangement and its application in CO oxidation

In this work, novel three-dimensional (3D) navicular ceria micro/nanocomposite architecture with multi-layered structure was synthesized for the first time via solution reaction followed by a simple hydrothermal treatment in the presence of lysozyme. During the synthesis procedure, a 3D navicular ceria precursor (Ce₂O(CO₃)₂·H₂O) with multi-layered structure was obtained after hydrothermal treatment at 100 °C for 10 h. Ceria with the same morphology can be obtained after thermal decomposition of this Ce₂O(CO₃)₂·H₂O precursor. Structural properties of the products were characterized by XRD, TG-DTA, FT-IR, SEM, TEM, and N₂-sorption techniques. Then a possible layer-by-layer electrostatic self-assembled growth mechanism was proposed for the formation of this 3D navicular architecture based on the experimental results and detail analysis of the evolution process of ceria precursors. Furthermore, a mold reaction of the catalytic oxidation of CO was conducted on the as-obtained CeO₂ and gold supported catalyst, both showed excellent activity and durability for CO conversion.     

Reactive magnetron sputtering of CuInS2 absorbers for thin film solar cells: Problems and prospects

We have investigated the reactive magnetron sputtering process from copper and indium targets in Ar/H₂S sputtering atmospheres for the deposition of CuInS₂ absorber films. This large area deposition method is in principle suited for the preparation of absorbers of good electronic quality. One of our best CuInS₂ cells exhibits an efficiency of 11.4% and an open circuit voltage of 745 mV, the highest reported value for CuInS₂ cells.However, it was found that the reproducibility of the photovoltaic layer properties is low. By analyzing the different defects in the films, it was found that the main defects are microscopic pin holes and crevices, which lead to short circuits. The intrinsic electronic quality of the magnetron sputtered CuInS₂ films is excellent, proven by room temperature photoluminescence spectroscopy.The occurrence of short circuits depends decisively on the film morphology, which is determined by the copper-to-indium ratio during the deposition. Even for constant external deposition parameters this ratio changes over the life time of the targets, mainly caused by a significant decrease of the indium deposition rate. For a stable CuInS₂ film deposition process an in situ control of the Cu/In ratio and the film morphology is advisable.     

Simultaneous removal of acetaldehyde,ammonia and hydrogen sulphide from air by active carbon impregnated with p-aminobenzoic acid,phosphoric acid and metal compounds

Simultaneous removal of acetaldehyde, ammonia, and hydrogen sulphide from air by the impregnated active carbon was studied at 25C. p-Aminobenzoic acid (PABA), phosphoric acid (H₃PO₄), and metal compound such as copper (II) chloride dihydrate (CuCl₂·2H₂O), copper (II) nitrate trihydrate (Cu(NO₃)₂·3H₂O), and potassium iodide (KI) were investigated as impregnation ingredients. Acetaldehyde and ammonia were simultaneously removed from air by the active carbon impregnated with PABA and H₃PO₄. The removal was found to be made mainly through chemical reaction. Acetaldehyde, ammonia, and hydrogen sulphide were simultaneously removed from air by the active carbon impregnated with PABA, H₃PO₄, and metal compound such as CuCl₂·2H₂O, Cu(NO₃)₂·3H₂O, and KI.     

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.