Synthesis and characterization of FeVO4 nanoparticles

Iron vanadate (FeVO₄) nanoparticles were synthesized by simple co-precipitation method using various surfactants such as ethylene glycol, polyethylene glycol 200 and polyethylene glycol 400 as the structure directing agents. Systematic investigations on the structural, morphological and magnetic properties of the materials have been studied. The lattice constants of the triclinic structure of FeVO₄ were calculated from the X-ray diffraction (XRD) analyses. The average grain size was estimated to be around 35 nm, which increased with increasing the calcination temperature. The stretching and bending vibrations of Fe-O were evaluated from the FT-IR spectra. Using VSM magnetometer, magnetic property was investigated through magnetic susceptibility and magnetization measurements. FeVO₄ exhibits two magnetic ordering temperatures at T ≈ 20 K and 14 K, which is due to two different chemical environments of Fe ligands such as octahedral FeO₆ and trigonal bipyramidal FeO₅ in a six-column doubly bent chain, respectively.     

Synthesis and electrochemical behavior of nanostructured cauliflower-shape Co-Ni/Co-Ni oxides composites

Nanostructured Co-Ni/Co-Ni oxides were electrochemically deposited onto stainless steel electrode by electrochemical method and characterized for their structural and supercapacitive properties. The SEM images indicated that the obtained Co-Ni/Co-Ni oxides had cauliflower-type nanostructure. The X-ray diffraction pattern showed the formation of Co₃O₄, NiO, Co and Ni. The EDX elemental mapping images indicated that Ni, Co and O are distributed uniformly. The deposited Co-Ni/Co-Ni oxides showed good supercapacitive characteristics with a specific capacitance of 331 F/g at 1 mA/cm² current density in 1 M KOH electrolyte. A mechanism of the formation of cauliflower-shape Co-Ni/Co-Ni oxides was proposed. A variety of promising applications in the fields such as energy storage devices and sensors can be envisioned from Co-Ni/Co-Ni oxides.     

Synthesis, characterization and optical properties of sheet-like ZnO

Sheet-like ZnO with regular hexagon shape and uniform diameter has been successfully synthesized through a two-step method without any metal catalyst. First, the sheet-like ZnO precursor was synthesized in a weak alkaline carbamide environment with stirring in a constant temperature water-bath by the homogeneous precipitation method, then sheet-like ZnO was obtained by calcining at 600 °C for 2 h. The structures and optical properties of sheet-like ZnO have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and UV-vis-NIR spectrophotometer. The results reveal that the product is highly crystalline with hexagonal wurtzite phase and has appearance of hexagon at (0 0 0 1) plane. The HRTEM images confirm that the individual sheet-like ZnO is single crystal. The PL spectrum exhibits a narrow ultraviolet emission at 397 nm and a broad visible emission centering at 502 nm. The band gap of sheet-like ZnO is about 3.15 eV.     

Synthesis and characterization of porous ZnO nanoparticles by hydrothermal treatment of as pure aqueous precursor

The presence of the complexing agents in the growth solution poses risk of the unintentional doping in the synthesized product and hence is likely to adversely affect the intrinsic properties. Herein we report the synthesis of ZnO nanoparticles with porous microstructure using pure aqueous precursor. Crystalline ZnO nanoparticles were synthesized by thermal treatment of aqueous solution of zinc acetate in an open bath. The size of the nanocrystals was controlled by changing the initial precursor concentration. The structural and optical properties of the synthesized nanocrystals were analyzed by X-ray diffraction, high resolution transmission electron microscopy, UV-vis absorption and room temperature photoluminescence measurement techniques. The TEM and UV-vis spectral signature analyses confirmed the formation of dispersed single crystalline ZnO nanoparticles. The nanopowders were found to have disordered mesoporous structure. The synthesized nanocrystals exhibited characteristic band edge emission as well as to surface defect related deep level visible luminescence.     

Synthesis and characterization of bulk and coatings of hydroxyapatite using methanol precursor

Hydroxyapatite, an important bioceramic was synthesized in the bulk form and developed as a coating by a sol-gel route using alcoholic precursor. The bioactive coating was developed on bio-inert α-alumina and yttria stabilized zirconia substrates. The apatite phase began to form after the heat treatment of the precursor at 500 °C for 10 min. The complete crystallization of the apatite was obtained at 800 °C heat treatment for 10 min. The phase composition of the bulk and the coatings was identified by FT-IR spectroscopic and powder X-ray diffraction (XRD) techniques. Surface morphology was determined by scanning electron microscopy. The study indicates different surface textures for the powder and for the coatings on α-alumina and yttria stabilized zirconia substrates.     

Synthesis of size tuneable cadmium sulphide nanoparticles from a single source precursor using ammonia as the solvent

Size tuneable cadmium sulphide nanoparticles of a few nanometres in size were prepared by thermolysis of a single source precursor of cadmium xanthates with variable carbon chain length (Cd(ROCS₂)₂, where R denotes -C₂H₅, -C₄H₉, -C₈H₁₇ and -C₁₂H₂₅, respectively) in an ammonia solution. The particle size, morphology and crystallinity of these nanoparticles were characterized using X-ray powder diffractometry, transmission electron microscopy, and nitrogen adsorption/desorption techniques. The results show that hexagonal CdS nanoparticles can be produced by thermolysis of cadmium alkyl xanthate in an ammonia solution at a temperature as low as 100 °C. The size of CdS particles (between 5.60 nm and 3.71 nm) decreases with increasing length of carbon chain in the precursor, as further confirmed by UV-visible and fluorescence spectrophotometric measurements. The size tuning mechanism of CdS from cadmium alkyl xanthate is also discussed.     

Preparation and characterization of indium doped CdS0.2Se0.8 thin films by spray pyrolysis

The CdS_0.2Se_0.8 and indium doped CdS_0.2Se_0.8 thin films have been deposited onto the amorphous glass and fluorine doped tin oxide coated glass substrates by spray pyrolysis. The doping concentration of indium has been optimized by photoelectrochemical characterization technique. The structural, surface morphological, optical and electrical properties of CdS_0.2Se_0.8 and indium doped CdS_0.2Se_0.8 thin films have been studied. X-ray diffraction studies reveal that the films are polycrystalline in nature with hexagonal crystal structure. Scanning electron microscopy studies reveal that the grains are uniform with uneven spherically shaped, distributed over the entire substrate surface. The complete surface morphology has been changed after doping. In optical studies, the transition of the deposited films is found to be direct allowed with optical energy gaps decreasing from 1.91 to 1.67 eV with indium doping. Semiconducting behavior has been observed from resistivity measurements. The thermoelectric power measurements reveal that the films exhibit n-type conductivity.     

Synthesis of aluminum nitride powder by carbothermal reduction of a combustion synthesis precursor

A new homogeneous mixing precursor of alumina and carbon (Al₂O₃ + C) was prepared by low temperature combustion synthesis (LCS) with aluminum nitrate (Al(NO₃)₃·9H₂O), urea (CO(NH₂)₂), and glucose (C₆H₁₂O₆·H₂O) as starting materials. The precursor prepared was a foamy and porous mass due to the large amount of gases liberated in the combustion reaction and composed of nanosize particles. XRD analysis showed that this precursor consisted of amorphous alumina and carbon. The amorphous alumina in the precursor first transformed into γ-Al₂O₃, and then γ-Al₂O₃ was directly nitrided to yield AlN during the calcination process. The reaction temperature needed for a complete conversion for the precursor was about 1400 °C, which is much lower than that when using alumina and carbon black as starting materials. The synthesized AlN powder was composed of very fine particles and had good dispersability.     

CeO2 nanocrystals: Seed-mediated synthesis and size control

This work reports on seed-mediated synthesis and size control of monodispersed CeO₂ nanoparticles. CeO₂ nanoparticles of mean size smaller than 2 nm were first prepared by a simple mixing of aqueous solution of cerium (IV) sulfate and ammonia solution at ambient conditions. Using these as-prepared fine particles as the tiny seeds, tunable sizes of CeO₂ nanoparticles were achieved via a facile hydrothermal treatment. All samples were characterized by X-ray diffraction (XRD), infrared (IR) spectroscopy, UV-vis spectroscopy, and thermogravimetric analysis (TGA). It is shown that in comparison with other inorganic cerium salts such as cerium (III) nitrates, cerium (IV) sulfate appears more suitable for forming CeO₂ nanoparticles at room temperature. Sulfate groups are strongly thermodynamically adsorbed on CeO₂ nanoparticle surfaces. The formation mechanism, surface hydration and sulfation characteristics of the resulting CeO₂ nanoparticles are also discussed.     

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 of fine magnetite powder using reverse coprecipitation method and its heating properties by applying AC magnetic field

Nano-sized FeFe₂O₄ ferrite powder for local thermal coagulation therapy was synthesized by a reverse coprecipitation method. The crystal diameter for the samples from the reverse coprecipitation method was smaller than that from a normal coprecipitation method. The crystal diameter increased with an increase in the synthesized temperature for both methods. The maximum increasing temperature under the AC magnetic field was at around a 12 nm crystal diameter. The FeFe₂O₄ powder was oxidized to Fe₂O₃ by calcination at 600 °C in ambient air. The heating ability almost depended on the hysteresis loss value. Although the increased temperature under the AC magnetic field for the fresh FeFe₂O₄ sample was very close to that for the commercialized MgFe₂O₄ powder, it was gradually decreased for FeFe₂O₄ with time in ambient air.     

Preparation and characterization of nanocrystallite size cuprous oxide

Uniform spheres of nanocrystallite size cuprous oxide particles have been prepared by a simple polyol process using cupric nitrate as a precursor in ethylene glycol. As synthesized compound was dried at 333 K in a vacuum oven and characterized by XRD, FT-IR and SEM techniques. The crystallite size of the cuprous oxide calculated from Scherer's formula was found to be ∼11 nm.     

Synthesis and characterization of micrometer Cu/PVP architectures

Micrometer-sized flower-like Cu/polyvinylpyrrolidone (PVP) architectures are synthesized by the reduction of copper (II) salt with hydrazine hydrate in aqueous solution in the presence of PVP capping agent. The resulting Cu/PVP architectures are investigated by UV-vis spectroscopy, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), and scanning electron microscopy (SEM). The Cu/PVP flowers have uniform morphologies with an average diameter of 10 μm, made of several intercrossing plates. The formation of Cu/PVP flowers is a new kinetic control process, and the factors such as the amount of N₂H₄H₂O, reaction temperature, molar ratio of CuCl₂ to PVP and molecular weight of PVP have significant effect on the morphology of Cu/PVP architectures. A possible mechanism of the formation of micrometer Cu/PVP architectures was discussed.     

Size and grain morphology dependent magnetic behaviour of Co-doped ZnO

We have carried out a comparative study of structural, microstructural and magnetic properties of the two sets of Co-doped ZnO samples synthesized using solid state reaction and sol–gel method. Rietveld refinement of the X-ray diffraction data reveals single phase hexagonal wurtzite structure for all the samples, while the tunnelling electron microscopy measurements show the presence of nano-phase in the sol–gel grown Co-doped ZnO samples. It is found that, the microstructure strongly depends on the synthesis method adopted. Samples with higher Co-concentration synthesized by SSR route exhibit antiferromagnetism while SG grown Co-doped ZnO samples exhibit weak ferromagnetic behaviour. Improved magnetic phase in the SG grown samples has been attributed to the grain morphology.     

Synthesis and characterization of carbon nanoribbons and single crystal iron filled carbon nanotubes

Carbon nanoribbons and single crystal iron filled multiwall carbon nanotubes (MWCNTs) have been synthesized by simple pyrolysis technique. SEM investigation shows that the material consist mainly carbon nanoribbons and carbon nanotubes (CNTs). X-ray diffraction (XRD), electron energy loss spectroscopy (EELS), electron energy dispersive X-ray (EDX), transmission electron miscroscopy (TEM) and highresolution transmission electron miscroscopy (HRTEM) studies reveal carbon nanotubes are filled with α-Fe. Closer inspection of HRTEM images indicated that the bcc structure α-Fe nanowires are monocrystalline and Fe (1 1 0) plane is indeed perpendicular to the G (0 0 2) plane, whereas orientation of (0 0 2) lattice planes of carbon nanoribbon is perpendicular to the axis of growth. Magnetic properties studied by superconducting quantum interference device (SQUID) at 300 K and 10 K exhibited coercivity of 1037 Oe and 2023 Oe. The large coercitivity is strongly attributed to the small size monocrystalline single phase α-Fe, single domain nature of the encapsulated Fe crystal, magnetocrystalline shape anisotropy and ferromagnetic behaviour of localized states at the edges of the carbon nanoribbons.     

Room temperature synthesis of Si-MCM-41 using polymeric version of ethyl silicate as a source of silica

Synthesis of mesoporous MCM-41 materials at room temperature using less expensive polymeric version of ethyl silicate (40 wt% SiO₂) as a source of silica was established. The influence of crucial synthesis parameters such as molar ratios of H₂O/NH₄OH, NH₄OH/SiO₂ and CTMABr/SiO₂ in gel on the quality of the phase formed was investigated. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and low temperature N₂ adsorption-desorption isotherms have been employed to characterize the products. The magnitude of orderness, textural properties and thermal stability of the Si-MCM-41 samples prepared under identical judiciously pre-controlled synthesis conditions using ethyl silicate and conventional tetraethyl orthosilicate (TEOS) were assessed. Even though, ethyl silicate has proved to be suitable source for the preparation of MCM-41 at room temperature, there exists an optimum value of H₂O/NH₄OH for different NH₄OH/SiO₂ molar ratios in the gel. Changes in the morphology were observed when NH₄OH/SiO₂, H₂O/NH₄OH molar ratios in the gels were changed.     

Structural characterization and surface heterogeneity of bimodal mesoporous silicas functionalized with aminopropyl groups and loaded aspirin

Bimodal mesoporous materials were modified with different amount of 3-aminopropyltriethoxysilane and employed as aspirin carriers. The modified and drug loaded bimodal mesoporous materials were characterized with XRD, FT-IR, TEM and elemental analysis methods to explore the influence of amino groups and drug molecules on the mesoporous surface. Meanwhile, the mesoporous surface energy states was calculated by the density functional theory based on the N₂ sorption analysis. According to the surface energy distributions of samples including before and after modification and drug loading, it can be deduced that through superficial modification with amino groups, the surface energy moves to high state, implying the introduction of amino moieties could provide the mesoporous surface with much active sites. Besides, the interaction between the amino groups and drug molecules is weak, and hence the controlled drug delivery would be possible.     

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.     

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.     

Na substitution for La- and Mn-sites in LaMnO3 from alkali halide fluxes: low temperature synthesis, structure and properties

La_1−xNa_xMn_1−yNa_yO₃ (0.12<x<0.16; 0.04<y<0.07) have been synthesized from NaBr and NaI fluxes at relatively low temperature of 850 and 750 °C, respectively. Final composition of these oxides was obtained from chemical analysis of the elements present. The flux grown oxides crystallize in the rhombohedral structure (space group R-3c, No. 167) and are ferromagnetic metals (FMM). Chemical analysis and Rietveld refinement of X-ray data indicate Na ion is substituted for both La- and Mn-sites in the compound prepared from NaBr and NaI fluxes with 33 and 49% of Mn⁴⁺ concentration, respectively.