Synthesis and characterization of a new layered magnesium zinc phosphate hydrate

A new layered magnesium zinc phosphate hydrate, MgZn(HPO₄)₂·H₂O, with a zinc phosphate framework isostructural with the one of Na₂Zn(HPO₄)₂·4H₂O, was prepared by the direct ambient pressure and temperature reaction between zinc 2,4-pentanedionate, phosphoric acid and hexahydrated magnesium chloride. The as-prepared sample is monoclinic (a = 8.780(7) Å, b = 13.240(7) Å, c = 11.123(0) Å and β = 116.21(2)°). The prepared solid undergoes two thermal transformations when it is heated from 110 to 600 °C. The first transformation is due to the release of intercalated water molecules and the second one is due to the HPO₄²⁻ → P₂O₇⁴⁻ transition.     

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.     

Synthesis, deposition and characterization of magnesium hydroxide nanostructures on zeolite 4A

The precipitation and self-assembly of magnesium hydroxide Mg(OH)₂ nanopetals on dispersed zeolite 4A particles was investigated. Mg(OH)₂/zeolite nanocomposites were produced from magnesium chloride solutions and characterized via X-ray powder diffraction (XRD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), Fourier transform infrared analysis (FTIR), and solid state NMR. It was determined that Mg(OH)₂ interacted with bridging hydroxyl protons (SiOHAl) on the zeolite surface, but not with silanol or aluminol groups. NMR analysis showed that 13% of the tetrahedral Al sites on the zeolite were converted to octahedral Al. The zeolite structure and crystallinity remained intact after treatment, and no dealumination reactions were detected. This suggests that the deposition-precipitation process at ambient conditions is a facile method for controlling Mg(OH)₂ nanostructures on zeolites.     

The growth of lanthanum phosphate (rhabdophane) nanofibers via the hydrothermal method

Hexagonal LaPO₄ (rhabdophane) nanofibers are synthesized and characterized. TEM images show that the synthesized LaPO₄ nanofibers are about 5-50 nm in diameter and up to several micrometers long. The morphologies of the product are strongly dependent on the pH value of the reaction solution.     

Synthesis and characterization of CuO nanoparticles from liquid ammonia

A new type of CuO nanoparticles were synthesized in liquid ammonia in the presence of sodium metal. First, Cu nanoparticles were obtained by reducing copper nitrate with the alkali metal in liquid ammonia, then, CuO nanoparticles were formed in the ambient conditions. The morphology and structure of as-prepared CuO nanoparticles were characterized by TEM and XRD, and the reason of aggregation of CuO nanoparticles was supposed.     

Synthesis and characterization of β-MnO2 single crystals with novel tetragonous morphology

β-MnO₂ single crystals with novel tetragonous morphology have been hydrothermally prepared in an HCl solution at 180 °C for 24 h without using templates, catalysts, and organic reagents. The structure of the obtained β-MnO₂ was systematically investigated by X-ray diffraction, SEM and TEM microscopy, FT-IR spectroscopy, DSC-TGA analyses, and chemical compositional analyses. The morphology of β-MnO₂ could be controlled by the hydrothermal treatment temperatures and the hydrothermal reaction times. β-MnO₂ single crystals with diameters 200-600 nm and lengths up to 1-5 μm not only had novel tetragonous morphology, but also had high purity.     

Synthesis and characterization of ZnS nanowires by AOT micelle-template inducing reaction

ZnS nanowires, with diameters around 30 nm and lengths up to 2.5 μm, had been successfully synthesized from solutions containing an anionic surfactant, sodium bis(2-ethylhexyl)sulfosuccinate (AOT). Powder X-ray diffraction (XRD) pattern, energy-dispersive X-ray spectroscopy (EDS) and selected-area electron diffraction (SAED) pattern indicated that the product was pure polycrystalline cubic-phase β-ZnS. The morphology and size of the as-synthesized product were determined by the transmission electron microscopy (TEM). The effects of some of the key reaction parameters (such as the ratio of surfactant to water, the reactant concentration and reaction temperature, etc.) had been explored in this paper. A growth mechanism of ZnS nanowires by micelle-template inducing reaction was also proposed.     

Intercalation of Ru(II) tris (1,10-phenanthroline) complex in α- and γ-zirconium dihydrogen phosphate. Synthesis, thermal behaviour and X-ray characterization

Layered inorganic systems such as ion-exchangers (α- and γ-zirconium dihydrogen phosphate) already used as hosts for larger cations, were studied for the intercalation of Ru(II) tris (1,10-phenanthroline) complex into these host matrices. The uptake of the complex occurs using the batch method; the colour of the materials changes from white to brilliant orange; the highest ion uptake is obtained in the case of the γ-phase. The materials obtained are thermally stable up to ∼350 °C and the complex decomposition occurs in two (α-phase) or three (γ-phase) steps. The complex decomposition is complete at ∼700 °C and at 550 °C (respectively for α- and γ-Ru(II) materials). As can be seen from the X-ray patterns, the Ru(II) materials are still layered and show a new phase with an increase in the interlayer distance with respect to the starting materials. The hydrogen form is always present in the case of the α-materials; whereas, in the case of the γ-materials, it is present when ≤0.12 moles of the complex/mole of exchanger are inserted. Microanalysis measurements confirm the fact that the Ru(II) complex is not modified when exchanged.     

PEG-300 assisted hydrothermal synthesis of 4ZnO·B2O3·H2O nanorods

4ZnO·B₂O₃·H₂O is commonly used as a flame-retardant filler in composite materials. The microstructure of the powder is of importance in its applications. In our study, for the first time, one-dimensional (1D) nanostructure of 4ZnO·B₂O₃·H₂O with rectangle rod-like shape has been synthesized by a hydrothermal route in the presence of surfactant polyethylene glycol-300 (PEG-300). The nanorods have been characterized by X-ray powder diffraction (XRD), inductively coupled plasma with atomic emission spectroscopy (ICP-AES), thermogravimetry (TG) and differential thermal analysis (DTA), scanning electron microscopy (SEM), transmission electron microscopy (TEM) equipped with selected area electron diffraction (SAED) as well as high-resolution transmission electron microscopy (HRTEM). These nanorods are about 70 nm in thickness, 150-800 nm in width and have lengths up to a few microns. 4ZnO·B₂O₃·H₂O nanorods crystallize in the monoclinic space group P2₁/m, a = 6.8871(19) Å, b = 4.9318(10) Å, c = 5.7137(16) Å, β = 98.81(21)° and V = 191.779(71) Å³.     

Preparation and characterization of lamellar-like Mg(OH)2 nanostructures via natural oxidation of Mg metal in formamide/water mixture

Facile, scale-up, and controllable fabrication of lamellar-like Mg(OH)₂ on a magnesium substrate through natural oxidation of Mg metal in formamide/water mixtures has been demonstrated. The one-step, wet-chemical approach has displayed well-controlled growth of densely packed magnesium hydroxide with large-area homogeneity and uniform morphology. The chemical-liquid-deposition process, an analogue to the widely used chemical-vapor-deposition technique, has been well developed for production of specific morphological Mg(OH)₂ through continuous supply, transport, and thermal decomposition of magnesium complexes in a liquid phase. The formation mechanism of lamellar-like Mg(OH)₂ was also discussed based on experimental phenomena.     

A new route for synthesizing VO2(B) nanoribbons and 1D vanadium-based nanostructures

This paper demonstrated the large-scale fabrication of metastable single crystal VO₂(B) nanoribbons with a home-made vanadium (IV, V) compound as a precursor. The influence factors on the morphology and a primary formation mechanism were presumably studied. Furthermore, the capability fabricating other vanadium-based 1D nanostructures was also explored from the precursor.     

Synthesis of flower- and rod-like nickel sulfide nanostructures by an organic-free hydrothermal process

Well-crystalline flower- and rod-like NiS nanostructures have been synthesized by an organic-free hydrothermal process at a low temperature of 200 °C. X-ray diffraction (XRD), field-emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) were employed to characterize the as-synthesized NiS nanostructures. The effects of temperature and reaction time on the morphology have been also investigated. The two-step flake-cracking mechanism for the formation of flower- and rod-like NiS nanostructures was discussed. The products were also investigated by photoluminescence (PL) spectroscopy.     

Hydrothermal synthesis, characterization, and influence factors of PbTe nanocrystals

In the present paper, we successfully prepared PbTe nanocrystals in a simple aqueous system via the hydrothermal route employing PbO, Te powders and N₂H₄·H₂O as the starting reactants at 150 °C for 14 h. Some factors affecting the morphologies of the PbTe nanocrystals, such as the reaction temperature, time, the amount of NaOH, sorts of reductants and Pb²⁺ ion sources, were systematically investigated. Experimental results indicated that, under keeping the other experimental conditions constant: raising the reaction temperature, the shapes of the as-obtained PbTe hardly changed, while decreasing the temperature, some PbTe dendrites were obtained; the short reaction time availed to obtain cubes with a hole in the center of each face; more amounts of NaOH were favorable to the formation of regular PbTe nanocuboids. When NaBH₄ was used as the reductant, a large amount of near spherical PbTe nanocrystals was produced; while NaH₂PO₂ was used, many PbTe crystals with hollow framework structures were obtained. When Pb(CH₃COO)₂ was used as the Pb²⁺ ion source, some dendrites made of many irregular particles were generated; while PbSO₄ was employed, many PbTe nanocuboids were produced. A possible formation mechanism of PbTe nanocrystals was proposed based on the experimental results.     

Synthesis, characterization and evaluation of nano-zirconium vanadate ion exchanger by using three different preparation techniques

Sol-gel, homogeneous precipitation and hydrothermal synthesis are three different preparation techniques have been used as an attempt to synthesize nano-zirconium vanadate with properties suitable to be used as ion exchangers. The impact of the synthetic preparation variables such as the reactant concentrations, reaction temperature and reaction time on the ion exchange capacity of the produced ion exchanger has been considered for each preparation technique. One sample from each preparation technique having the largest ion exchange capacity has been selected to be physically and chemically characterized using various analytical techniques such as XRD, TGA, DSC, pH titration, FTIR and SEM in order to determine the properties of the ion exchanger produced from each technique. For all the studied ZrV samples it can be presumed that they have the ion exchange affinity sequences for alkali metal ions K > Na > Li, the order for the alkaline earth metals is Ba > Ca > Mg and their affinity for radioactive metals follow Cs > Sr. Moreover, the prepared materials are of high thermal and radiation stabilities. Also they have high chemical stabilities toward wide concentration ranges of acid, basic as well as polar solvents. It has been deduced from the X-ray analysis that ZrV produced from the sol-gel technique has an amorphous structural. While those produced from the homogeneous precipitation and hydrothermal synthesis techniques, in the nano-scale have semi-crystalline structural. Furthermore, SEM confirms that particle size of the all studied prepared ZrV samples have nano-diameters of range 50-60 nm. Specific surface area of the three different prepared ion exchangers are found to be equal to 187, 192 and 320 m²/g for sol-gel, homogeneous precipitation and hydrothermal, respectively. A tentative structural formula of Zr(OH)₂(HVO₄)₂·2H₂O has been proposed for all studied samples on the basis of on FTIR, DSC and TGA results.     

Synthesis of single-crystalline Ce(CO3)(OH) with novel dendrite morphology and their thermal conversion to CeO2

Single-crystalline cerium carbonate hydroxide (Ce(CO₃)(OH)) with dendrite morphologies have been successfully synthesized by hydrothermal method at 150 °C using Ce(NO₃)₃·6H₂O as the cerium source, aqueous carbamide as both an alkaline and carbon source and poly(vinyl pyrrolidone) (PVP) as surfactant. Ceria (CeO₂) with dendrite morphologies have been fabricated by a thermal decomposition-oxidation process at 500 °C for 6 h using single-crystalline Ce(CO₃)(OH) dendrites as the precursor. The dendrite morphologies of Ce(CO₃)(OH) was sustained after thermal decomposition-oxidation to CeO₂. The as-prepared products were characterized by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), field-emission scanning electron microscopy (FE-SEM), and thermogravimetric analysis (TG).     

Urchin-like Co2P nanocrystals: Synthesis, characterization, influencing factors and photocatalytic degradation property

In this paper, cobalt phosphides (Co₂P) nanocrystals with urchin-like structures have been successfully synthesized via a water-ethanol mixed-solvothermal route, employing white phosphorus (WP) and cobalt dichloride as starting reactants, sodium acetate as the pH adjustor, and sodium dodecyl benzene sulfonate (SDBS) as the surfactant. The as-obtained product was characterized by X-ray powder diffraction (XRD), energy dispersive spectrometry (EDS), (high resolution) transmission electron microscopy (TEM/HRTEM), selected area electron diffraction (SAED) and field emission scanning electron microscopy (FESEM). It was found that sodium acetate played an important role in the formation of Co₂P nanocrystals with urchin-like structures. Some factors influencing the morphology of the product, including the reaction temperature, time, amounts of WP and SDBS and so on, were investigated. The photocatalytic property of the product for the degradation of organic dyes was studied. A possible formation mechanism of urchin-like Co₂P nanocrystals was suggested based on the experiment results.     

Synthesis and characterization of layered double hydroxides (LDHs) with intercalated chromate ions

Chromate intercalated layered double hydroxides (LDHs) having the formula M^II₆M′^III₂(OH)₁₆CrO₄·4H₂O (M^II = Ca, Mg, Co, Ni, Zn with M′^III = Al and M^II = Mg, Co, Ni with M′^III = Fe) have been prepared by coprecipitation. The products obtained are replete with stacking disorders. DIFFaX simulations show that the stacking disorders are of three kinds: (i) turbostratic disorder of an originally single layered hexagonal (1H) crystal, (ii) random intergrowth of polytypes with hexagonal (2H) and rhombohedral (3R) symmetries and (iii) translation of randomly chosen layers by (2/3, 1/3, z) and (1/3, 2/3, z) leading to stacking faults having a local structure of rhombohedral symmetry. IR spectra show that the CrO₄²⁻ ion is incorporated either in the T_d or in the C_3v symmetry. The interlayer spacing in the latter case is 7.3 Å characteristic of a single atom thick interlayer showing that the CrO₄²⁻ ion is grafted to the metal hydroxide slab. On thermal treatment, the CrO₄²⁻ ion transforms into Cr(III) and is incorporated into the spinel oxide or phase separates as Cr₂O₃. In the LDH of Mg with Al, Cr(III) remains in the MgO lattice as a defect and promotes the reconstruction of the LDH on soaking in water. In different LDHs, 18-50% of the CrO₄²⁻ ion is replaceable with carbonate anions showing only partial mineralization of the water-soluble chromate. The extent of replaceable chromates depends upon the solubility of the corresponding LDH, which in turn is determined by the solubility of the MCrO₄. These studies have profound implications for the possible use of LDHs for chromate amelioration in green chemistry.     

Hydrothermal preparation, characterization and property research of flowerlike ZnO nanocrystals built up by nanoflakes

In the present paper, flowerlike ZnO nanocrystals were successfully synthesized via a simple hydrothermal route in the presence of sodium dodecyl sulfate (SDS), employing Zn(CH₃COO)₂ and KOH as the starting reactants. The phase and morphology of the product were characterized by means of powder X-ray diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and select area electron diffraction (SAED). The optical properties of the product were studied. Some factors influencing the morphology of the final product including reaction time, temperature and amounts of the surfactant were discussed. Researches showed that the flowerlike ZnO nanocrystals had a good photo-catalytic activity for degradation of safranine T under 254 nm UV light irradiation. The electrochemical research of the product showed that flowerlike ZnO nanocrystals could promote electron transfers between catechol and the Au electrode. A possible formation mechanism was also suggested based on the results of the experiments.     

A facile soft template synthesis and characterization of PbHAsO4 nanocrystals

Monoclinic lead hydrogen arsenate (LHA) nanocrystals with different crystallization morphologies and crystallite sizes were prepared successfully by a soft template synthesis method in the presence of sodium dodecylbenzenesulfonate (SDBS) or polyvinylpyrrolidone (PVP). The products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The possible mechanism of SDBS and PVP in the experiment was briefly illustrated.     

Synthesis of cerium hydroxycarbonate powders via a hydrothermal technique

CeOHCO₃ powders have been directly synthesized using a hydrothermal process at temperatures as low as 160°C. The well-dispersed powders are obtained in a short period of reaction time during hydrothermal reaction via the hydrolysis of urea. For synthesizing CeOHCO₃, the concentration of urea is found to be a crucial determinant, which has significant effects on the morphology of the derived powders. When low urea concentrations are provided, the formed particles are rhomboidal platelets. On the other hand, the high urea concentrations cause the shape of the powders to become prismatic. Increasing the concentration of urea tends to increase the particle size as well as the aspect ratio of CeOHCO₃ powders. After further heating at 500°C, a phase transformation from orthorhombic CeOHCO₃ to cubic CeO₂ takes place. The crystallinity and size of CeO₂ strongly depend on the particle size of CeOHCO₃.