Synthesis and characterization of reduced transition metal oxides and nanophase metals with hydrazine in aqueous solution

Reduction of the first row (3d) transition metal complexes in aqueous solution using hydrazine as the reducing agent has been investigated systematically. Nanoscale reduced metal oxides such as VO₂(B), Cr₂O₃ were obtained through hydrazine reduction followed by proper thermal treatments. Nanocrystalline γ-Mn₂O₃ was synthesized directly through aqueous phase reduction at room temperature. Nanoclusters of cobalt, copper and the one-dimensional single crystal nickel nanowhiskers were synthesized by direct reduction without post-annealing process. All the products were characterized on their structure and micro-morphology. The reaction details and features were described and discussed.     

Synthesis and structural characterization of two-dimensional hierarchical covellite nano-structures

We report a simple, template free and low-temperature hydrothermal reaction pathway using Cu(II) – thiourea complex (prepared in situ from copper (II) chloride and thiourea as precursors) and citric acid as complexing agent to synthesize two-dimensional hierarchical nano-structures of covellite (CuS). The product was characterized with the help of X-ray powder diffraction (XRD), scanning electron microscopy (SEM), energy dispersive analysis of X-ray spectroscopy (EDAX) and X-ray photoelectron spectroscopy (XPS). The concentration of citric acid in the hydrothermal precursor solution was seen to have a profound effect on the nanostructure of the product generated. Based on the outcoming product nano-architecture at different concentration of the ionic surfactant in the hydrothermal precursor solution a possible mechanism suited for reaction and further nucleation is also discussed.     

Synthesis and characterization of single crystalline PbO nanorods via a facile hydrothermal method

Single crystalline β-PbO nanorods with diameter range from 40 to 120 nm and length up to 500 nm have been synthesized via a facile hydrothermal method in the presence of citrate. X-ray diffraction (XRD), transmission electron microscopy (TEM), high-resolution transmission electro-microscope (HRTEM) and SAED were used to characterize the as-obtained samples. An interesting intermediate state of self-assembled β-PbO rod-like nanoparticles was found and the possible formation mechanism of single crystalline β-PbO nanorods was also discussed.     

Synthesis and photoluminescence properties of CaSiO3:Eu spheres prepared by the reverse micelles soft template

We report here the successful synthesis of CaSiO₃:Eu³⁺ spheres using the reverse micelles soft template. The influence of the calcination temperature on the shape, crystallization and photoluminescence properties of the prepared spheres was investigated by DTA-TG, XRD, IR, SEM and PL. The results showed that the temperature of crystallization (from amorphous phase to β-CaSiO₃) is 668 °C. The temperature of phase transition (from β-CaSiO₃ to α-CaSiO₃) is 790 °C. The average size of CaSiO₃:Eu³⁺ spheres calcined at 700 °C was about 350 nm. The radiation was dominated by the red emission peak at 613 nm and the highest emission intensity was observed when the spheres were calcined at 700 °C. When calcined at 800 °C, the spheres are almost cracked and melted down, due to the high temperature.     

Microwave-assisted co-precipitation synthesis of high purity β-tricalcium phosphate crystalline powders

A new fabrication technique of β-tricalcium phosphate (β-TCP) has been investigated by the microwave-assisted co-precipitation method and subsequent calcinations. The synthesized powders were characterized by X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), thermogravimetry-differential thermal analysis (TG-DTA), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The calcium/phosphorous atomic ratio of the as-dried sample was determined by energy dispersive analysis of X-rays (EDAX). The results showed that high purity and well-crystallized β-TCP powders could be obtained in a rapid way by microwave processing. The formation process of β-TCP was explained based on the TG-DTA analysis. The effects of microwave irradiation on the reaction mechanism and reaction rate were preliminarily analyzed in the paper.     

Synthesis and characterization of a mesoporous hydrous zirconium oxide used for arsenic removal from drinking water

Powder (20-50 μm) mesoporous hydrous zirconium oxide was prepared from a zirconium salt granular precursor. The effect of some process parameters on product morphology, porous structure and adsorption performance has been studied. The use of hydrous zirconium oxide for selective arsenic removal from drinking water is discussed.     

Synthesis, characterization, and hydrophobic properties of Bi2S3 hierarchical nanostructures

Novel Bi₂S₃ hierarchical nanostructures self-assembled by nanorods are successfully synthesized in mild benzyl alcohol system under hydrothermal conditions. The hierarchical nanostructures exhibit a flower-like shape. X-ray diffraction (XRD), X-ray photoelectron spectra (XPS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED) were used to characterize the as-synthesized samples. Meanwhile, the effect of various experimental parameters including the concentration of reagents and reaction time on final product has been investigated. In our experiment, PVP plays an important role for the formation of the hierarchical nanostructures and the possible mechanism was proposed. In addition, Bi₂S₃ film prepared from the flower-like hierarchical nanostructures exhibits good hydrophobic properties, which may bring nontrivial functionalities and may have some promising applications in the future.     

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.     

Photocatalytic studies of antimonate compounds prepared by a self-combustion route

Antimonates compounds with 1Ca:1Sb and 2Ca:1Sb:1Al compositions were synthesized by a self-combustion method. For the 1Ca:1Sb composition, a calcination at 1573 K led to a pure Ca₂Sb₂O₇ weberite phase, whose structure was determined using the Rietveld method. In the case of the 2Ca:1Sb:1Al composition, a pure phase was achieved at 1073 K, and the use of higher calcination temperatures led to a mixture of phases. Some of the products (1Ca:1Sb (873 K), 2Ca:1Sb:1Al (1073 K) and Ca₂Sb₂O₇ (1573 K)) were tested as photocatalysts for the methyl orange degradation. The results clearly demonstrated that Ca₂Sb₂O₇ is the catalyst exhibiting the best results for the MO photocatalytic degradation. This fact was interpreted as due to a predominant role of structural features on the photocatalytic activity of the prepared compounds.     

Two polymeric metal complexes based on polycarbazole containing complexes of 8-hydroxyquinoline with Zn(II) and Ni(II) in the backbone: Synthesis,characterization and photovoltaic applications

Two novel polymeric metal complexes PZn(Q)₂–C and PNi(Q)₂–C based on polycarbazole containing complexes of 8-hydroxyquinoline with Zn(II) and Ni(II) were synthesized and applied in dye-sensitized solar cells (DSSCs) as photosensitizers. They possess moderate thermal stability and good open-circuit voltages, and the power conversion efficiency of them reached to 1.11% and 0.45%, respectively, under simulated AM 1.5 G solar irradiation (100 mW cm⁻²), which shows a new strategy to design photosensitizers for DSSCs.     

Synthesis and photocatalytic properties of Zn doped anatase TiO2 nanofibers

Zn²⁺ doped TiO₂ nanofibers were prepared by electrospinning followed by calcination. The results of TGA, FE-SEM, XRD and XPS indicated that the obtained nanofibers with diameter in range of 50–150 nm were composed of anatase TiO₂ phase and Zn²⁺ doping in TiO₂ did not distort the pristine crystal structure of TiO₂. Besides methylene blue (MB) was employed to investigate photocatalytic properties of the obtained samples. The results revealed that Zn²⁺ doped TiO₂ nanofibers had excellent photocatalytic activity, which was symbolized by an optimum photodegradation efficiency of 96.1% under Zn²⁺ doping concentration of 2 at.%. The photocatalytic efficiency of 2 at.% Zn²⁺ doped TiO₂ nanofibers still exceeded 95% after using for five times.     

Strontium vanadate nanoribbons: Synthesis, characterization and detection of dopamine

Large-scale, high-purity and uniform strontium vanadate (Sr₂V₂O₇) nanoribbons were easily synthesized via a hydrothermal process without any surfactants. The as-prepared products were up to hundreds of micrometers in length, 200-600 nm in width, and 20 nm in thickness. These nanomaterials were employed to modify glassy carbon electrode, which displayed excellent electrochemical sensitivity in detecting dopamine in the presence of ascorbic acid. A linear relationship between the concentrations of dopamine and its oxidation peak currents was obtained. The modified electrode exhibited high reproducibility and stability, which might be found potential application in the biosensors.     

The synthesis and characterization of electrical and magnetic nanocomposite: PEDOT/PSS–Fe3O4

The poly(3,4-ethylenedioxythiophene)/poly(styrene sulfonate)–Fe₃O₄ (PEDOT/PSS–Fe₃O₄) nanoparticles have been prepared by using polystyrene sulfonic sodium (NaPSS) as a dispersant and dopant. The characterization of nanocomposites was investigated by transmission electron microscope, X-ray diffraction, UV spectroscopy, electrochemical study, four-probe, thermogravimetric analysis and magnetic property measurement system. XRD revealed the presence of spinel phase of Fe₃O₄ and the average size was calculated to be about 12 nm. The conductivity of nanocomposites at room temperature is excellent and it depends on the Fe₃O₄ content. The thermal stability of composites is outstanding. Higher saturation magnetization of 6.47 emu g⁻¹ (20 wt.% Fe₃O₄) was observed at 300 K.     

Synthesis and conductivity of undecatungsto chromoferrous heteropoly acid

The ternary undecatungsto chromoferrous heteropoly acid (HPA) H₆Fe(H₂O)CrW₁₁O₃₉·14H₂O has been synthesized for the first time by the stepwise acidification and the stepwise addition of solutions of the component elements as well as ion exchanging-cooling method. The optimal proportion of the solutions of the component elements and the pH of the synthesis reaction are given. The product is characterized by chemical analysis, IR, UV, XRD and TG-DTA. The results of AC impedance measurement show that its proton conductivity is 3.89×10⁻³ S cm⁻¹ at room temperature (20°C).     

Copper substitutions in synthetic miargyrite α-AgSbS2 mineral: Synthesis,characterization and dielectrical properties

The nominal compositions Ag_0.8Cu_0.2SbS₂ and Ag_0.7Cu_0.3SbS₂ have been synthesized by conventional ceramic solid-state reaction at high temperature. X-ray diffraction (XRD) and scanning electron microscopy chemical analysis (SEM-EDAX) revealed single phases, isostructural to the natural miargyrite α-AgSbS₂ mineral. Examination of the lattice parameters shows a decrease in the cell volume with increasing copper substitutions. The Raman analysis displays absorptions which may be assigned to the Sb–S stretching vibrations of the SbS₃ pyramids. The impedance-frequency analysis showed grain boundary and electrode interface contributions in non-Debye type relaxation, following Jonscher's universal power law. The giant permittivity response is attributed to extrinsic effects without evidence of a ferroelectric transition. Summerfield scaling, leading to the superposition of impedance analysis, implies that the relaxation is thermally activated, without introducing more than one underlying transport mechanism.     

Synthesis and conductivity of solid high-proton conductor H5GeW10MoVO40·21H2O

A new solid high-proton conductor decatungstomolybdovanadogermanic heteropoly acid (HPA) H₅GeW₁₀MoVO₄₀·21H₂O has been synthesized for the first time by stepwise acidification and stepwise addition of solutions of the component elements. The product was characterized by chemical analysis, potentiometric titration, IR, UV, XRD and TG-DTA. The IR, UV and XRD indicate that H₅GeW₁₀MoVO₄₀·21H₂O possesses the Keggin structure. The TG-DTA curve shows the sequence of water loss in the acid, the amount of the loss, as well as the thermostability. The results of AC impedance measurement show that its proton conductivity is 3.58 × 10⁻⁴ S cm⁻¹ at 18 °C and the activation energy for proton conduction is 31.82 kJ/mol.     

Synthesis of higher surface area mayenite by hydrothermal method

Mayenite (Ca₁₂Al₁₄O₃₃) is an important material, being used as a transparent conductive oxide (TCO), catalysts for VOCs cleaning and ionic conductor. Unfortunately, the material has a very low BET surface area, generally below 10 m²/g and requires higher calcination temperature for the formation of mayenite phase. In this study, a new synthesis method, namely hydrothermal method, was employed for the synthesis of mayenite with higher BET surface area of about 70 m²/g, and also the calcination temperature decreased from over 1000 to just 400 °C. It was found that mayenite from different method shows different shapes.     

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 and electrochemical performances of spinel LiCr0.1Ni0.4Mn1.5O4 compound

The spinel compound LiCr_0.1Ni_0.4Mn_1.5O₄ was synthesized by a solid reaction method and a sol-gel method using citric acid as chelating agent. The pure phase LiCr_0.1Ni_0.4Mn_1.5O₄ was obtained by the wet method. The electrochemical performances of the pure phase sample were measured at different current rates. There were three voltage plateaus at about 4.9, 4.7 and 4.0 V in the charge-discharge curves, which were attributed to the oxidation/reduction of chromium, nickel and manganese respectively. In the range of 3.5-5.0 V, its first discharge capacity was 143, 118 and 111 mAh/g corresponding to current densities of 1.0, 4.0 and 5.0 mA/cm², respectively. After 50 cycles, the capacity retention remained well at the current densities of 1.0, 4.0 and 5.0 mA/cm². The electrochemical performances of pure phase LiCr_0.1Ni_0.4Mn_1.5O₄ at 55 °C was also measured, and the results were discussed.     

Synthesis of polypyrrole coated manganese nanowires and their application in hydrogen peroxide detection

This study focuses on the synthesis and application of polypyrrole coated manganese nanowires (Mn/PPy NWs) as an enzyme-less sensor for the detection of hydrogen peroxide (H₂O₂). The X-ray diffraction (XRD), field emission scanning electron microscopy (FESEM) and transmission electron microscopy (TEM) results confirm a core–shell structure with the Mn nanowires encapsulated by the PPy. An electrochemical sensor based on the Mn/PPy NWs for amperometric determination of H₂O₂ is prepared. The electrochemical behaviour of H₂O₂ is investigated by cyclic voltammetry with the use of modified glassy carbon electrode (GCE) with Mn/PPy NWs film. The modified glassy carbon electrode (GCE) with Mn/PPy NWs shows enhanced amperometric response for the detection of H₂O₂. This is due to the high available surface area of Mn/PPy NWs which can provide a suitable area for the reaction of H₂O₂. The detection limit and limit of quantification (S/N = 3) for two linear segments (low and high concentration of H₂O₂) are estimated to be 2.12 μmol L⁻¹, 7.07 μmol L⁻¹ and 22.3 μmol L⁻¹, 74.5 μmol L⁻¹, respectively. In addition, the sensitivity for these two linear segments is 0.4762 μA mM⁻¹ and 0.0452 μA mM⁻¹ respectively.