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.     

Preparation and characterization of rare earth orthoborates, LnBO3 (Ln = Tb, La, Pr, Nd, Sm, Eu, Gd, Dy, Y) and LaBO3:Gd, Tb, Eu by metathesis reaction: ESR of LaBO3:Gd and luminescence of LaBO3:Tb, Eu

Lanthanide orthoborates of composition LnBO₃ (Ln = Tb, La, Pr, Nd, Sm, Eu, Gd, Dy, Y) and LaBO₃:Gd, Tb, Eu have been prepared by metathesis reaction. This method provides a convenient route for the synthesis of orthoborates and its solid solutions at low temperatures. Powder X-ray diffraction and FT-IR spectroscopy were used to characterize these borates. Rare earth borates, (LnBO₃) are isomorphous with different forms of CaCO₃ depending on the radius of rare earth ion. LaBO₃, LaBO₃:Gd, Tb, Eu, PrBO₃, NdBO₃ crystallized in aragonite structure, SmBO₃ crystallized in H-form and TbBO₃, EuBO₃, GdBO₃, DyBO₃, YBO₃ crystallized in vaterite structure. The structural analysis of TbBO₃ was carried out. The morphology of these borates was obtained from Scanning electron microscopy. Spin-Hamiltonian parameters for Gd³⁺ are deduced from room temperature electron spin resonance spectrum of LaBO₃:Gd. The luminescence of LaBO₃:Tb, Eu gave characteristics peaks corresponding to Tb³⁺, Eu³⁺ respectively.     

Preparation and luminescence properties of Mn-doped ZnGa2O4 nanofibers via electrospinning process

One-dimensional Mn²⁺-doped ZnGa₂O₄ nanofibers were prepared by a simple and cost-effective electrospinning process. X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TG-DTA), scanning electron microscopy (SEM), energy-dispersive X-ray spectrum (EDS), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), photoluminescence (PL) and cathodoluminescence (CL) spectra as well as kinetic decays were used to characterize the samples. SEM results indicated that the as-formed precursor fibers and those annealed at 700 °C are uniform with length of several tens to hundred micrometers, and the diameters of the fibers decrease greatly after being heated at 700 °C. Under ultraviolet excitation (246 nm) and low-voltage electron beams (1–3 kV) excitation, the ZnGa₂O₄:Mn²⁺ nanofibers presents the blue emission band of the ZnGa₂O₄ host lattice and the strong green emission with a peak at 505 nm corresponding to the ⁴T₁–⁶A₁ transition of Mn²⁺ ion.     

Hydrothermal synthesis,characterization and luminescent properties of GdPO4·H2O:Tb nanorods and nanobundles

In this paper, the Tb³⁺-doped GdPO₄·H₂O nanorods and nanobundles have been synthesized by the hydrothermal method with and without glycine, respectively. The X-ray powder diffraction (XRD), thermogravimetric and differential thermal analysis (TG–DTA), Fourier transform infrared spectroscopy (FT-IR), transmission electron microscopy (TEM), energy-dispersive spectra (EDS) and photoluminescence (PL) were employed to characterize the as-obtained products. It was found that the addition of glycine and the pH value have crucial influences on the formation of the resulting morphologies and sizes. The possible formation mechanisms for GdPO₄·H₂O:Tb³⁺ nanorods and nanobundles were put forward. A detailed investigation on the photoluminescence of GdPO₄·H₂O:Tb³⁺ different samples revealed that the luminescent properties of products are strongly correlated with the morphologies, sizes, coordination environment and crystal field symmetry.     

Encapsulation of titanium (IV) silsesquioxane into the NH4USY zeolite: Preparation, characterization and application

This work describes the encapsulation of titanium (IV) silsesquioxane into the supercavities of NH₄USY ultra stabilized zeolite, after chemical treatment. The modified zeolite was characterized by Fourier transform infrared spectra, Nuclear magnetic resonance, scanning electronic microscopy, X-ray diffraction and thermogravity. This encapsulated titanium (IV) silsesquioxane can adsorb Azure A chloride after treatment with H₃PO₄, without modifier leaching problems. In an electrochemical study, the cyclic voltammograms of the graphite paste modified electrode, shows two redox couples with formal potential (E⁰′) −0.1 V and 0.21 V to I and II redox couples respectively (v=700 mV s−1; Britton Robinson buffer (B-R) solution, pH 3) versus SCE ascribed to a monomer and dimmer of azure. This paper shows the use of ultra stabilized zeolite in the electrochemical field as host for molecules with nanometric dimensions.     

Preparation, characterization and electrical conductivity studies of nanocrystalline La doped BaMoO4

Different compositions of scheelite type nanocrystalline La doped BaMoO₄ [Ba_1−xLa_xMoO_4+x/2, where x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5] samples were prepared by acrylamide assisted sol-gel combustion process. Dried gels prepared at 60 °C were heated at different temperatures and characterized using TG/DTA, XRD, FTIR and SEM-EDX techniques. From XRD patterns, crystalline phases for La doped BaMoO₄ samples were confirmed and their average crystallite sizes were calculated using Scherrer's formula and it was found to be less than 80 nm. Structure and thermal behavior of scheelite type nanocrystalline La doped BaMoO₄ samples were identified respectively using FTIR and TG/DTA measurements. Microstructure and existence of O, La, Ba and Mo elements in the La doped BaMoO₄ samples were obtained from SEM-EDX and HRTEMtechniques. The ‘d’ spacing values were obtained for different (h k l) planes and were well matched with the standard BaMoO₄. (h k l) values for different directions of planes were assigned for the observed HRTEM images and were matched with standard BaMoO₄. Grain and grain boundary conductivities were evaluated by analyzing the impedance data, using the Winfit software, measured at different temperatures.     

Preparation and characterization of organic-inorganic poly(ethylene glycol)/WS2 nanocomposite

Layered nanocomposite PEG/WS₂, intercalating oligomeric poly(ethylene glycol) (PEG6000) into the tungsten disulfide host galleries, was synthesized using the exfoliation-adsorption technique. X-ray diffraction revealed that the intercalated oligomer within the host galleries is in a double-layer arrangement with an interlayer expansion of about 8.8 Å. The optimum conditions were explored to prepare the single-phase product with a composition of Li_0.12(PEG)_1.51WS₂. Thermal analyses suggested that the resulting material shows good thermal stability, with the decomposition of the interacted oligomeric chains within the disulfide galleries occurring at around 258 °C. Despite high conductivity of the host material, those of the PEG/WS₂ nanocomposite were found to be high in the order of 1 × 10⁻² S cm⁻¹ at ambient temperature, resulted from the host guest-host charge transfers.     

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.     

Structural study and luminescence of TlSrLa(AsO4)2

This work presents the crystal structure and luminescent properties of TlSrLa(AsO₄)₂. In this phase Tl⁺ ions are located in large tunnels delimited by chains of alternating (AsO₄) and (Sr,La)O₈ polyhedra. Thallium atoms are eightfold coordinated with C₁ symmetry. Large TlO distances are observed revealing a low stereochemical activity of the 6s² lone pair. Excitation and emission spectra of Tl⁺ in TlSrLa(AsO₄)₂ showed broad bands at lower energy than those observed in previous works. Excitation spectra are decomposed into multiple Gaussian bands and a theoretical analysis is made to explain the number of observed components. Two Gaussian components are revealed for emission spectra.     

Preparation and electrocatalytic activity of tungsten carbide and titania nanocomposite

Tungsten carbide and titania nanocomposite was prepared by combining a reduced-carbonized approach with a mechanochemical approach. The samples were characterized by X-ray diffraction, transmission electron microscope under scanning mode and X-ray energy dispersion spectrum. The results show that the crystal phases of the samples are composed of anatase, rutile, nonstoichiometry titanium oxide, monotungsten carbide, bitungsten carbide and nonstoichiometry tungsten carbide, and they can be controlled by adjusting the parameters of the reduced-carbonized approach; tungsten carbide particles decorate on the surface of titania support, the diameter of tungsten carbide particle is smaller than 20 nm and that of titania is around 100 nm; the chemical components of the samples are Ti, O, W and C. The electrocatalytic activity of the samples was measured by a cyclic voltammetry with three electrodes. The results indicate that the electrocatalytic activities of the samples are related to their crystal phases and the property of electrolyte in aqueous solution. A synergistic effect between titania and tungsten carbide is reported for the first time.     

Synthesis and characterization of nanocrystalline Zn ferrites substituted with Ni

Nanocrystalline powders of nickel substituted zinc ferrite with general formula Ni_xZn_1−xFe₂O₄ (x = 0, 0.2, 0.4, 0.6, 0.8, 1) have been synthesized via sol-gel auto-combustion method using tartaric acid as combustion-complexing agent. Samples were sintered at 773 K and 973 K in static air atmosphere. The absence of the organic phase and the spinel formation were monitored by using Fourier transform infrared spectroscopy. The structure and crystallite size were analyzed from X-ray diffraction data revealing spinel mono-phase formation in the range of nanometric crystallite size confirmed also through scanning electron microscopy. Mean size of crystallites lay in the range 20-40 nm. The influence of nickel content on the microstructure was investigated considering the crystallite size, distance between adjacent crystal planes, lattice parameter and porosity. The variation of magnetic properties of the samples was studied by using vibrating samples magnetometer and discussed considering the proposed cation distribution, relative bond angles and canting angles. The highest maximum value of the magnetization (63 emu/g) was found for Ni_0.8Zn_0.2Fe₂O₄.     

Preparation of VO2 nanowires and their electric characterization

Large-scale VO₂ nanowires have been synthesized by two-step method. First, we have been obtained (NH₄)_0.5V₂O₅ nanowire precursors by hydrothermal treatment of ammonium metavanadate solution at 170 °C. Secondly, the precursors have been sealed in quartz tube in vacuum and annealed to form VO₂ nanowires at 570 °C. Scanning electron microscope and transmission electron microscope analysis show that the nanowires have self-assembling nanostructure with the diameter of about 80-200 nm, length up to125 μm. Electrical transport measurements show that it is semiconductor with conduction activate energy of 0.128 eV. A metal-semiconductor transition can be observed around 341 K.     

Synthesis and photoluminescent properties of mesoporous (MgO)x(ZnO)1−x materials

(MgO)_x(ZnO)_1−x materials have been synthesized using mesoporous carbon as template. By increasing the MgO content in the materials greater than 25%, the (MgO)_x(ZnO)_1−x materials began to form the mesoporous structure. Pore size distribution curves indicated that the BJH pore diameter decreased with increasing MgO content. In photoluminescence spectra, all the samples except pure ZnO showed both the band-edge emission and the deep-level emission (green band). It was interesting to note that the UV emission peak energy (E_UV) had a red-shift of about 48 meV at the low MgO content range of 0-25%, while when the MgO content varied from 25 to 75%, the E_UV displayed a blue-shift of about 36 meV to the higher energy direction. The optical band gap (E_g) of the (MgO)_x(ZnO)_1−x calculated from the absorption spectra was far smaller than that in literature, and this may be related to the formation of mesoporous structure.     

Fabrication and characterization of mesoporous TiO2/polypyrrole-based nanocomposite for electrorheological fluid

Mesoporous TiO₂/polypyrrole (PPy)-based nanocomposite for electrorheological fluid was synthesized through one-pot method. By exploiting the combination conductivity of PPy and high dielectric constant of TiO₂, the ER fluid exhibited an enhanced effect. The shear stress was 3.3 times as high as that of mesoporous TiO₂. Powder X-ray diffraction (XRD), TEM and Fourier transform infrared (FT-IR) spectroscopy were employed to characterize the as-made samples. Using a modified rotational viscometer, the electrorheological effect was measured. Dielectric spectra were also given to explain the mechanism.     

Synthesis and characterization of chloro-sulphide glass-ceramics containing neodymium(III) ions

In this paper, we describe the preparation of Nd³⁺ doped glass-ceramics in the (GeS₂)₇₀-(Ga₂S₃)₂₀-(CsCl)₁₀ system. Neodymium has been introduced as metallic powder or incorporated as sulphide. Appropriate heat treatments of the base-glass lead to glass-ceramics with controllable crystal sizes that are transparent in the visible and infrared spectral ranges. X-ray diffraction as well as electron diffraction techniques were used to investigate the crystallization process. Differential scanning calorimetry indicates that neodymium ions are poor nucleating agents in this glass compared to erbium ions. Luminescence measurements were also performed and point out that although the ceramization process increases significantly the luminescence efficiency, the neodymium ions are only partially incorporated in the nanocrystals.     

Synthesis and characterization of new composites: PANI/Na-AlSBA-3 and PANI/Na-AlSBA-16

The new aluminosilicate materials (Na-AlSBA-3 and Na-AlSBA-16) were synthesized for application in the preparation of composites. Silica mesoporous materials were obtained following the sol-gel method and post-synthesis alumination. These methods were effective for the synthesis of SBA-3 and SBA-16, showing XRD patterns and other characteristics in agreement with the literature.Aniline-saturated hosts were prepared by adsorption of aniline (exposed to the equilibrium vapors from liquid aniline) into the mesoporous materials. Polyaniline/Na-AlSBA-3 (PANI-3) and polyaniline/Na-AlSBA-16 (PANI-16) composites have been synthesized by an in situ polymerization of aniline-saturated hosts. TG, FTIR, XRD, SEM and TEM were used to characterize the resulting composites. These studies show that PANI is generated inside the channel of the hosts. PANI-16 has an amount of emeraldine salt higher than PANI-3 composite. The electrical conductivity measurements confirmed that PANI and mesoporous materials were true hybrid nanocomposites. The conductive properties of these composites were compared with those of other composites (polyaniline/Na-AlMCM-41 and polyaniline/Na-AlSBA-15) reported.     

Synthesis and photoluminescence of Ca-(Sn,Ti)-Si-O compounds

The phase relation of the compounds prepared in the CaO-SnO₂-SiO₂ system at 1673 K and in the CaO-TiO₂-SiO₂ system at 1573 K was investigated in order to explore new Ti⁴⁺-activated stannate phosphors. Solid solutions of Ca(Sn_1−xTi_x)SiO₅ and Ca₃(Sn_1−yTi_y)Si₂O₉ were synthesized at x = 0-1.0 and y = 0-0.10, respectively, and their crystal structures were analyzed by powder X-ray diffraction. Photoluminescence of these solid solutions was observed in a broad range of a visible light wavelength region under ultraviolet (UV) light excitation. The peaks of the emission band of Ca(Sn_0.97Ti_0.03)SiO₅ and Ca₃(Sn_0.925Ti_0.075)Si₂O₉ were at 510 nm under excitation of 252 nm and at 534 nm under excitation of 258 nm, respectively. The absorption edges estimated by the diffuse reflectance spectra were at 300 nm (4.1 eV) for CaSnSiO₅ and at 270 nm (4.6 eV) for Ca₃SnSi₂O₉, suggesting that the excitation levels in Ca(Sn_1−xTi_x)SiO₅ were above the band gap of the host, although the levels in Ca₃(Sn_1−yTi_y)Si₂O₉ were within the band gap and near the conduction band edge.     

Unusual intrinsic luminescence of the host and energy transfer process in YVO4:Er phosphors

YVO₄:Er³⁺ phosphors were prepared by solid state reaction method. The X-ray diffraction results testify the pure tetragonal YVO₄ crystalline phase. The emission spectra of the samples show the obvious intrinsic luminescence of the hosts even though the concentration of the dopants has reached nominal 6 mol%, which is unusual since it is believed that the energy transferring from VO₄³⁻ to rare-earth ions occurs efficiently, thus the intrinsic luminescence of the host disappears when the concentration of the dopants is higher than ∼1 mol%. The comparison of the photoluminescence excited at 320 nm (the absorption of vanadate host) and 380, 490, 525 or 532 nm (the absorption of erbium ions) in visible and infrared range has revealed that energy transfer process has occurred in the system. The study of decay times has revealed that the energy transfer efficiency of the doped YVO₄:Er samples is very low. The low efficiency might be one important reason for the unusual intrinsic emission of the host.     

Electrospinning preparation and characterization of a new kind of composite nanomaterials: One-dimensional composite nanofibers doped with TiO2 nanoparticles and Ru(II) complex

One-dimensional composite nanomaterials, PVP (poly(vinylpyrrolidone)) fibers with diameters in the range of 300–500 nm doped with RuL₂(NCS)₂ (L = 4,4′-Dicarboxy-2,2′-bipyridine) complex and TiO₂ nanoparticles (NPs), were prepared by electrospinning technique. The morphology of the composite nanofibers was systemically studied when the diameters of TiO₂ NPs, the concentrations of TiO₂ NPs and RuL₂(NCS)₂ in the PVP matrix were changed. A new kind of organic–inorganic composite nanomaterials which combine the advantages of one-dimensional nanostructures, organic materials and inorganic materials was obtained and it is desirable for low-weight and flexible photovoltaic devices, especially for dye-sensitized TiO₂ solar cells.     

Synthesis and characterization of IR up-conversion material CaS:Eu, Sm by low-temperature combustion synthesis method

Infrared up-conversion material CaS:Eu, Sm was synthesized by the low-temperature combustion synthesis (LCS) method, which has expanded the application range of the LCS method which is always used in the synthesis of oxides and compound oxides. The combustion process was discussed and the effect of the amount of carbamide on the up-conversion luminescence properties was analyzed. XRD patterns show that the products are with the cubic CaS crystal structure. Spectral analysis indicates that the sample can be excited effectively by ultraviolet or visible light to store energy, and subsequently is sensitive to 800-1600 nm infrared light and then emit red light resulting from the multi-transitions of Eu²⁺ 4f⁶5d → 4f⁷(⁸S_7/2).