Preparation and characterization of inorganic colored coating layers on lamellar mica-titania substrate

The inorganic colored composite pigments, such as Fe₂O₃-, Bi₄Ti₃O₁₂-, and CoAl₂O₄-coated mica-titania composites, were prepared by hydrolysis of FeCl₃, Bi(NO₃)₃, and Co(NO₃)₂/Al(NO₃)₃ in the presence of mica-titania substrate and calcination at different temperatures. The inorganic coating layers on mica-titania substrate surfaces were explored by X-ray diffraction, scanning electron microscopy, Fourier transform infrared, and X-ray photoelectron spectroscopy. Dense and uniform Fe₂O₃ coating layers were formed on the surfaces of mica-titania substrates. At lower Bi₂O₃ loading, Bi₄Ti₃O₁₂ nanoparticles were formed on the surfaces of mica-titania substrates. But at higher Bi₂O₃ loading, Bi₄Ti₃O₁₂ nanosheets were formed and perpendicularly oriented to the substrate surfaces. CoAl₂O₄ nanosheets were formed on the mica-titania substrates and perpendicularly oriented to the substrate surfaces. The pigmentary performances of the inorganic composite pigments were analyzed by CIE, indicating that red, yellow, and blue colored pigments were achieved by coating Fe₂O₃, Bi₄Ti₃O₁₂, and CoAl₂O₄ on mica-titania substrate surfaces, respectively. The pigmentary performances of the inorganic composite pigments were significantly affected by the morphology and loading of inorganic coating layers.     

Preparation of Bi2S3 thin films with a nanoleaf structure by electrodeposition method

Nanoleaf-like Bi₂S₃ thin films were deposited on indium tin oxide (ITO) glass using Bi(NO₃)₃ and Na₂S₂O₃ as precursors by a cathodic electrodeposition process. The as-deposited thin films were characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), atomic force microscopy (AFM) and photoluminescence spectrum (PL). The influence of precursor solution mole concentration ratios [Bi(NO₃)₃]/[Na₂S₂O₃] on the phase compositions, morphologies and photoluminescence properties of the obtained thin films were investigated. Results show that a uniform Bi₂S₃ thin film with nanoleaf structure can be obtained with the precursor solution concentration ratio [Bi(NO₃)₃]/[Na₂S₂O₃] = 1:7. The as-prepared thin films exhibit blue-green photoluminescence properties under ultraviolet light excitation. With the increase of concentration ratios [Bi(NO₃)₃]/[Na₂S₂O₃] in the deposition solution, the crystallizations and PL properties of Bi₂S₃ thin films are obviously improved.     

One-dimensional structures of Bi2O3 synthesized via metalorganic chemical vapor deposition process

We have demonstrated the synthesis of one-dimensional (1D) structures of bismuth oxide (Bi₂O₃) by a reaction of a trimethylbismuth (TMBi) and oxygen (O₂) mixture at 450 °C. Scanning electron microscopy showed that the product consisted of 1D materials with width or diameters less than 1 μm and lengths up to several tens of micrometers. The X-ray energy dispersive spectroscopy revealed that the materials contained elements of Bi and O. The results of X-ray diffraction and selected area electron diffraction pattern indicated that the obtained Bi₂O₃ were crystalline with monoclinic structure.     

Application of transmission electron microscopy for studying phase relations in the bismuth-rich region of the Ba-Bi-O system

The crystal structure and cation composition of oxides of the Ba-Bi-O system in the composition range 80–100 mol % BiO_1.5 have been investigated by the methods of transmission electron microscopy. Ordered phases of the compositions Ba: Bi = 2: 9, 1: 6, and 1: 15 with a rhombohedral structure have been revealed. In the range of the compositions Ba: Bi from 1: 36 to 1: 46, phases with triclinic, monoclinic, and cubic structures have been found. The monoclinic and cubic phases have structures similar to the structures of the α and γ modifications of bismuth oxide Bi₂O₃, respectively. Phase formation was found to be dependent on the following parameters: annealing temperature, partial oxygen pressure, oxygen content in the initial pairs of reacting components (BaO₂-Bi₂O₃, Ba(NO₃)₂-Bi₂O₃, BaCO₃-Bi₂O₃), and crucible material (alundum or platinum).     

Simultaneous removal of nitrogen oxides and diesel soot particulate in nano-structured electrochemical reactor

Simultaneous decomposition of nitrogen oxides (NO_x) and solid state graphite particles were carried out using a 8 mol% Y₂O₃ doped ZrO₂ (YSZ) based electrochemical reactor with a nano-structured NO_x selective multilayer cathode and an oxidative porous anode. The ceramic electrochemical cell was prepared by screen-printing a Pt and a NiO–YSZ pastes as cathode layers and a 12 CaO7Al₂O₃–Pt paste as an anode layer on the YSZ electrolyte, respectively. Simultaneous decomposition of NO_x and graphite particles was investigated using the cell with coated graphite particles on the surface of the 12 CaO7Al₂O₃–Pt composite anode in 1000 ppm NO_x–He gas flow under applying DC voltage at 475 °C. The coated graphite particles at the anode were removed completely with 80% NO_x decomposition by electrochemical reactions.     

The influence of oxidation temperature on structural, optical and electrical properties of thermally oxidized bismuth oxide films

Monoclinic bismuth oxide (Bi₂O₃) films have been prepared by thermal oxidation of vacuum evaporated bismuth thin films onto the glass substrates. In order to obtain the single phase Bi₂O₃, the oxidation temperature was varied in the range of 423-573 K by an interval of 50 K. The as-deposited bismuth and oxidized Bi₂O₃ films were characterized for their structural, surface morphological, optical and electrical properties by means of X-ray diffraction, scanning electron microscopy (SEM), optical absorption and electrical resistivity measurements, respectively. The X-ray analyses revealed the formation of polycrystalline mixed phases of Bi₂O₃ (monoclinic, α-Bi₂O₃ and tetragonal, β-Bi₂O₃) at oxidation temperatures up to 523 K, while at an oxidation temperature of 573 K, a single-phase monoclinic α-Bi₂O₃ was formed. From SEM images, it was observed that of as-deposited Bi films consisted of the well-defined isolated crystals of different shapes while after thermal oxidation the smaller dispersed grains were found to be merged to form bigger grains. The changes in the optical properties of Bi₂O₃ films obtained by thermal oxidation at various temperatures were studied from optical absorption spectra. The electrical resistivity measurement depicted semiconducting nature of Bi₂O₃ with high electrical resistivity at room temperature.     

Anionic conductors Ln2/3[Bi12O14](MoO4)5 with Ln = La,Nd, Gd,Ho, Yb. Synthesis–spark plasma sintering–structure–electric properties

A new series of columnar phases Ln_2/3□_1/3[Bi₁₂O₁₄](MoO₄)₅ (□ vacancy) with Ln = La, Nd, Gd, Ho and Yb have been synthesized and structurally characterized. They feature the same formula as the molybdate phase Bi_2/3□_1/3[Bi₁₂O₁₄](MoO₄)₅ and crystallize in the monoclinic system, space group P2/c. These phases are isostructural with the prototype structure Bi[Bi₁₂O₁₄](MoO₄)₄(VO₄). Pellets of this rare-earth series obtained by spark plasma sintering and measured by impedance spectroscopy show a good anionic conductivity with a parabolic evolution whose maximum is raised by the Gd species at a determined value σ = 6.6 × 10^− 3 S cm^− 1 at 980 K.     

Syntheses and structural characterization of two new nanostructured Bi(III) supramolecular polymers via sonochemical method

Two new bismuth(III) coordination supramolecular polymers, {[Bi₂(Hbpp)(bpp)(μ-I)₂I₆](Hbpp)·MeOH}_n (1) and [Bi(Hbpp)(Br₄)] (2), (bpp = 1,3-di(pyridin-4-yl)propane) were prepared and were structurally characterized by single crystal X-ray diffraction. Single crystalline one-dimensional materials were prepared using a heat gradient applied a solution of the reagents using the branched tube method. The structural determination by single crystal X-ray crystallography shows that compounds 1 and 2 form monoclinic polymers with symmetry space group P2₁ in the solid state. These new nanostructured Bi(III) supramolecular compounds, {[Bi₂(Hbpp)(bpp)(μ-I)₂I₆](Hbpp)·MeOH} (1) and [Bi(Hbpp)(Br₄)] (2), were also synthesized by sonochemical method. The nanostructures were characterized by Field Emission-scanning electron microscopy (FE-SEM), powder X-ray diffraction (PXRD) and IR spectroscopy.     

Electrodeposition of thermoelectric Bi2Te3 thin films with added surfactant

Bismuth telluride (Bi₂Te₃) thin films were electrodeposited at room temperature from nitric baths in the presence of a surfactant, cetyltrimethylammonium bromide (CTAB). Nearly stoichiometric Bi₂Te₃ thin films were obtained from electrolytes containing 7.5 mM Bi(NO₃)₃. The surface morphology and mechanical properties of the electrodeposited thin film were improved by the addition of CTAB to the electrolyte, while the electrical and thermoelectric properties were preserved. Post-deposition annealing in a reducing environment did not improve the electrical and thermoelectric properties, possibly because the change in the microstructure of the Bi₂Te₃ thin film was too small.     

Rapid,Microwave‐Assisted,and One‐Pot Synthesis of Magnetic Palladium–CoFe2O4–Graphene Composite Nanosheets and Their Applications as Recyclable Catalysts

Here, a microwave‐assisted approach has been demonstrated to rapidly prepare magnetic Pd–CoFe₂O₄–graphene (GE) composite nanosheets in ethylene glycol (EG) solvent. The generation of both Pd and CoFe₂O₄ nanoparticles is accompanied with the reduction process of graphene oxide (GO) by EG. The surface morphologies and chemical composition of the composite nanosheets are characterized by transmission electron microscopy (TEM), energy‐dispersive X‐ray spectrometer (EDS), powder X‐ray diffraction (XRD), X‐ray photoelectron spectroscopy (XPS), and Fourier transform infrared spectroscopy (FTIR) measurements. The as‐prepared Pd–CoFe₂O₄–GE composite nanosheets exhibit a remarkable catalytic activity towards the reduction of 4‐nitrophenol by sodium borohydride (NaBH₄) at room temperature. The apparent kinetic rate constant (K _app) of this catalytic reaction could reach about 11.0 × 10^?3 s^?1. Moreover, the CoFe₂O₄ component exhibits a magnetic property, which could make the Pd–CoFe₂O₄–GE composite nanocatalysts separated from the suspension system. The catalytic conversion of the 4‐nitrophenol to 4‐aminophenol could reach 87.2% after four cycles. This work presents a simple, rapid, and versatile method to fabricate both metal and spinel‐type complex oxides on GE nanosheets, providing a new opportunity for their applications in the recyclable catalytic reaction.     

Hydroxyethyl cellulose-assisted hydrothermal synthesis of Bi2S3 urchin-like colonies

Orthorhombic Bi₂S₃ with different morphologies was successfully synthesized by the acid-catalyst hydrothermal reactions of bismuth nitrate (Bi(NO₃)₃) and thiourea (NH₂CSNH₂) solutions containing different amounts of hydroxyethyl cellulose (HEC). Phase, morphologies, and optical properties were characterized by X-ray diffraction, selected area electron diffraction, scanning and transmission electron microscopy, and ultraviolet-visible spectroscopy. The products, hydrothermally synthesized in the HEC-free, 0.25 g HEC-added, 0.5 g HEC-added and 1.00 g HEC-added solutions, were respectively proved to be orthorhombic Bi₂S₃ irregular nanorods, complete urchin-like colonies of regular nanorods, incomplete urchin-like colonies of regular nanorods, and highly crystalline regular nanorods growing along the [001] direction. Tauc band gaps of the orthorhombic Bi₂S₃ nanorods, synthesized in the HEC-free, 0.25 g HEC-added, and 1.00 g HEC-added solutions were determined to be 3.0, 1.75 and 1.8 eV, respectively. Formation mechanism of orthorhombic Bi₂S₃ nanorods, synthesized in the HEC-free and HEC-added solutions, was also discussed at great detail.     

Local ordered magnetic fields in bismuth dielectrics. 209Bi NQR in Bi4Ge3O12 single crystal

The results of the ²⁰⁹Bi NQR experiments carried out on α-Bi₂O₃, Bi₃O₄Br, Bi₂M₄O₉ (M=Al, Ga), Bi₂Ge₃O₉, and Bi₄Ge₃O₁₂ showed that these compounds are not diamagnets in the conventional sense. The Zeeman perturbed zero-field ²⁰⁹Bi NQR spectra gave an indication that local ordered magnetic fields of the order of 30–200 G exist in these substances comprising neither transition nor rare earth elements. Further aspects of this principally new phenomenon of yet unknown nature were studied by the ²⁰⁹Bi NQR experiments on the Bi₄Ge₃O₁₂ single crystal in external magnetic fields below 500 Oe, applied at various orientations with respect to the crystal axes. The spectral patterns of dramatically increased intensity and multiplicity, caused by the unknown magnetism of the compound, were observed in applied fields and modeled. Based on the results of the modeling, the conclusions were made that at least four magnetically non-equivalent Bi sites characterized by antiferromagnetically ordered local fields of the order of 30 G are present in the Bi₄Ge₃O₁₂ crystal; the intensity increase was interpreted to arise from the change in orientation of the electric field gradient axes at the Bi site upon applying an external magnetic field.     

Light Dispersion in Bismuth Germanate Crystals and Bismuth Oxide Films

The dispersion of light in Bi₄Ge₃O₁₂ and Bi₁₂GeO₂₀ single crystals and thin Bi₂O₃ films with a monoclinic structure was investigated in the visible spectral region. The parameters of a single-oscillator approximation have been found. It is established that in Bi₄Ge₃O₁₂ crystals the absorption band caused by the O2p–Bi6p transitions makes the main contribution to the dispersion curve in the visible region, whereas in Bi₁₂GeO₂₀ crystals this is made by transitions from the hybrid O2p–Bi6p states to the conduction band. The dispersion energy, the degree of the ionicity of binding, and the coordination number of the first coordination sphere of the Bi³⁺ cation have been determined.     

Sonochemical synthesis of a new nano-structures bismuth(III) supramolecular compound: New precursor for the preparation of bismuth(III) oxide nano-rods and bismuth(III) iodide nano-wires

A new nanostructured Bi(III) supramolecular compound, {[Bi₂(4,4′-Hbipy)_1.678(4,4′-Hbipy)_0.322(μ-I)₂I_5.678] (4,4′-bipy)} (1), 4,4′-bipy = 4,4′-bipyridine} was synthesized by a sonochemical method. The nano-structure of 1 was investigated using scanning electron microscopy, powder X-ray powder diffraction (XRD), IR spectroscopy and elemental analysis, and the crystal structure of compound 1 was determined by single-crystal X-ray diffraction. The thermal stability of bulk compound 1 and of nano sized particles was studied by thermal gravimetric (TG) and differential thermal analyses (DTA). Bi₂O₃ and BiI₃ nano-structures were obtained by calcinations of nano-structures of compound 1 at 400 °C under air and nitrogen atmospheres, respectively.     

Synthesis and visible light photocatalysis water splitting property of chromium-doped Bi4Ti3O12

Photocatalysts Bi₄Ti_3 ? xCr_xO₁₂(x = 0.00, 0.06, 0.15, 0.30, 0.40, and 0.50) with perovskite structure were synthesized by sol–gel method and their electronic structures and photocatalytic activities were investigated. The Bi₄Ti_2.6Cr_0.4O₁₂ photocatalyst exhibited the highest performance of H₂ evolution in methanol aqueous solution (58.1 μmol h^? 1 g^? 1) under visible light irradiation (λ > 400 nm) without a co-catalyst, whereas no H₂ evolution is observed for Bi₄Ti₃O₁₂ under the same conditions. The UV–vis spectra indicated that the Bi₄Ti_2.6Cr_0.4O₁₂ had strong photoabsorption in the visible light region. The results of density functional theory (DFT) calculation illuminate that the conduction bands of Bi₄Ti₃O₁₂ are mainly attributable to the Ti 3d + Bi 6p orbitals, and the valence bands are composed of O 2p + Bi 6s hybrid orbitals, while the conduction bands of chromium-doped Bi₄Ti₃O₁₂ are mainly attributable to the Ti 3d + Bi 2p + Cr 3d orbitals, and the O 2p + Cr 3d hybrid obitals are the main contribution to the valence band.     

Luminescence spectroscopy of Ln-doped Bi-containing phosphates and molybdates

The photoluminescence (PL) emission and excitation spectra of undoped and doped with rare-earth (RE = Eu, Tb) ions K₃Bi₅(PO₄)₆ and K₂Bi(PO₄)(MoO₄) crystals are studied in 3.7–14 eV region of the excitation photon energies at T = 8 and 300 K. The mechanisms of the host-related and RE-related luminescence in 3.7–7 eV region of the excitation photon energies are revealed in comparative analysis of the PL spectra of studied compounds. It is assumed that the excitation mechanisms of host luminescence of K₃Bi₅(PO₄)₆ and K₂Bi(PO₄) (MoO₄) crystals below 4.8 eV are related to Bi³⁺ ions in oxygen surrounding. An efficient energy transfer from the Bi³⁺-related luminescence centers to the emitting RE centers exists in crystals with low concentration of the RE dopants (1%). The PL excitation spectra of K₃Bi₅(PO₄)₆ crystals with high concentration of Eu dopants are formed by O – Eu CT transitions.     

Studies on the sonochemical polymorphism of Sb2O3 on activated graphite for the electrochemical determination of imipramine

This work reports the simultaneous sonochemical activation of graphite and sonohydrolysis of antimony chloride (SbCl₃) in the alkaline medium. The experiments conducted by bath sonicator operated at 37 kHz of frequency and a maximum power of 150 W. The simple sonohydrolysis of SbCl₃ alone produced an orthorhombic phase of Sb₂O₃, whereas, it produced mixed phases of cubic and orthorhombic Sb₂O₃ when introduced with graphite. Herein, the activated graphite (aGR) provides the best support to the growth of cubic phase. This cubic Sb₂O₃ is grown only on the graphite basal planes, which confirmed by scanning electron microscope. Moreover, the phase changes have identified by the X-ray diffraction, Raman and X-ray photoelectron analysis. The prepared aGR-Sb₂O₃ composite has applied to the electroanalytical studies of anti-depressant drug imipramine (IMP). The results showed that aGR-Sb₂O₃ revealed better activity than Sb₂O₃; the reasons are discussed comprehensively. Furthermore, aGR-Sb₂O₃ exhibited comparable analytical results for the determination of IMP.     

Luminescence of Bismuth‐Activated Ceramics of Yttrium and Scandium Oxides

The luminescence spectra of Y₂O₃:Bi and Sc₂O₃:Bi ceramics have been investigated. The spectra have been resolved into elementary components by the Alentsev–Fock method. It has been established that the luminescence is attributed to emission centers of three types, two of which are due to the replacement of Y³⁺ (or Sc³⁺) by Bi³⁺ at the nodes of the crystal lattice of Y₂O₃ (or Sc₂O₃) with the point symmetry C ₂ and C _3i . The emission center Bi³⁺ in the position C_3i leads to the appearance of blue luminescence with maxima at 3.03 eV for Y₂O₃:Bi and at 3.05 eV for Sc₂O₃:Bi; this luminescence is attributed to the transition ³ P ₁–¹ S ₀. The emission center Bi³⁺ in the position C ₂ initiates green luminescence (which is also related to the ³ P ₁–¹ S ₀ transition in Bi³⁺) with a maximum in the region of 2.40 eV in Y₂O₃:Bi and in the region of 2.46 eV in Sc₂O₃:Bi. The red luminescence band with maxima at 1.85 eV in Y₂O₃:Bi and at 1.95 eV in Sc₂O₃:Bi is related to the presence of structural defects.     

Synthesis and characterization of (Bi,Cu)Sr2(RE,Ca)Cu2Oz (RE: Y or rare-earth element)

Samples with nominal compositions of x = 0–0.1 in (Bi_(1+3x)/3Cu_(2?3x)/3)Sr₂(RE_1?xCa_x)Cu₂O_z ((Bi,Cu)-“1-2-1-2”; RE: Y or rare-earth element) were synthesized by a solid-state reaction method and characterized by means of X-ray diffractometry (XRD). It is confirmed that the (Bi,Cu)-“1-2-1-2” forms only when RE = Y, Dy and Ho. Single- or nearly single-phase samples are obtained for x = 0–0.05 and the Ca-free composition of this compound is determined to be (Bi_1/3Cu_2/3)Sr₂RECu₂O_z. Since ionic radii of Y, Dy and Ho are very close to each other and this seems to be an essential factor for the stability of the (Bi,Cu)-“1-2-1-2”.     

Micro‐Raman study of exfoliated Bi2Sr2CaCu2O8+δ single crystals with different thicknesses

Exfoliated Bi₂Sr₂CaCu₂O_8+δ (Bi‐2212) single crystals were prepared by micromechanical cleavage of bulk Bi‐2212 single crystals on SiO₂/Si substrates. Room temperature micro‐Raman spectra were collected using a 532‐nm laser source. The evolutions of the spectra of A_1g (Bi), A_1g (Sr), and A_1g (O_Bi) Raman modes with different thicknesses of the samples were studied. The refractive index of Bi‐2212 single crystal was obtained by studying the intensity evolutions based on the interference effect. The observed wavenumber shifts of the A_1g (Bi), A_1g (Sr), and A_1g (O_Bi) modes were analyzed. Copyright © 2011 John Wiley & Sons, Ltd.