Synthesis of titanate nanostructures using amorphous precursor material and their adsorption/photocatalytic properties

This article reports on a new and swift hydrothermal chemical route to prepare titanate nanostructures (TNS) avoiding the use of crystalline TiO2 as starting material. The synthesis approach uses a commercial solution of TiCl3 as titanium source to prepare an amorphous precursor, circumventing the use of hazardous chemical compounds. The influence of the reaction temperature and dwell autoclave time on the structure and morphology of the synthesised materials was studied. Homogeneous titanate nanotubes with a high length/diameter aspect ratio were synthesised at 160 degrees C and 24 h. A band gap of 3.06 +/- 0.03 eV was determined for the TNS samples prepared in these experimental conditions. This value is red shifted by 0.14 eV compared to the band gap value usually reported for the TiO2 anatase. Moreover, such samples show better adsorption capacity and photocatalytic performance on the dye rhodamine 6G (R6G) photodegradation process than TiO2 nanoparticles. A 98% reduction of the R6G concentration was achieved after 45 min of irradiation of a 10 ppm dye aqueous solution and 1 g L-1 of TNS catalyst.

Synthesis of titanate nanofibers co-sensitized with ZnS and Bi2S3 nanocrystallites and their application on pollutants removal

The synthesis of nanocomposite materials combining titanate nanofibers (TNF) with nanocrystalline ZnS and Bi2S3 semiconductors is described in this work. The TNF were produced via hydrothermal synthesis and sensitized with the semiconductor nanoparticles, through a single-source precursor decomposition method. ZnS and Bi2S3 nanoparticles were successfully grown onto the TNF's surface and Bi2S3-ZnS/TNF nanocomposite materials with different layouts. The samples' photocatalytic performance was first evaluated through the production of the hydroxyl radical using terephthalic acid as probe molecule. All the tested samples show photocatalytic ability for the production of this oxidizing species. Afterwards, the samples were investigated for the removal of methylene blue. The nanocomposite materials with best adsorption ability were the ZnS/TNF and Bi2S3ZnS/TNF. The dye removal was systematically studied, and the most promising results were obtained considering a sequential combination of an adsorption-photocatalytic degradation process using the Bi2S3ZnS/TNF powder as a highly adsorbent and photocatalyst material. (C) 2015 Elsevier Ltd. All rights reserved.

A thermal analysis study of dithizone and dithizonates of mercury, silver and bismuth

Solid dithizonates of Hg(I), Ag(I) and Bi(III) have been prepared. Thermogravimetry (TG), derivative thermogravimetry (DTG), differential scanning calorimetry (DSC), X ray diffraction powder patterns and elemental analysis have been used to characterize and to study the thermal stability and thermal decomposition of the dithizone and of these dithizonates.

Unusual bismuth-containing surface layers of III-V compound semiconductors

The understanding and engineering of bismuth (Bi) containing semiconductor surfaces are signi cant in the development of novel semiconductor materials for electronic and optoelectronic devices such as high-e ciency solar cells, lasers and light emitting diodes. For example, a Bi surface layer can be used as a surfactant which oats on a III-V compound-semiconductor surface during the epitaxial growth of IIIV lms. This Bi surfactant layer improves the lm-growth conditions if compared to the growth without the Bi layer. Therefore, detailed knowledge of the properties of the Bi/III-V surfaces is needed. In this thesis, well-de ned surface layers containing Bi have been produced on various III-V semiconductor substrates. The properties of these Bi-induced surfaces have been measured by low-energy electron di raction (LEED), scanning-tunneling microscopy and spectroscopy (STM), and synchrotron-radiation photoelectron spectroscopy. The experimental results have been compared with theoretically calculated results to resolve the atomic structures of the studied surfaces. The main ndings of this research concern the determination of the properties of an unusual Bi-containing (2×1) surface structure, the discovery and characterization of a uniform pattern of Bi nanolines, and the optimization of the preparation conditions for this Bi-nanoline pattern.

Continuous hydride generation in the presence of L- cysteine for the determination of arsenic, bismuth, antimony and tin in steels by inductively coupled plasma atomic emission spectrometry

Arsenic, bismuth, germanium, antimony and tin were simultaneously determined by continuous hydride generation and inductively coupled plasma-atomic emission spectrometry . I Hydrides were introduced into four different types of gas-liquid separators. Two of the gas-liquid separators were available in-house. A third was developed for this project and a fourth was based on a design used by CET AC. The best signal intensity was achieved by the type II frit-based gas-liquid separator, but the modified Cetac design gave promise for the future, due to low relative standard deviation. A method was developed for the determination of arsenic, bismuth, antimony and tin in low-alloy steels. Four standard reference materials from NIST were dissolved in 10 mL aqua regia without heat. Good agreement was obtained between experimental values and certified values for arsenic, bismuth, antimony and tin. The method was developed to provide the analyst with the opportunity to determine the analytes by using simple aqueous standards to prepare calibration lines. Within the limits of the samples analyzed, the method developed is independent of matrix.

Surface effect ferromagnetism in pure and reduced strontium titanate

A room temperature ferromagnetic hysteresis is observed in single crystal strontium titanate substrates as purchased from several manufacturers. It was found that polishing all sides of the substrates removed this observed hysteresis, suggesting that the origin of the ferromagnetic behavior resides on the surface of the substrates. X-ray diffraction and energy dispersive x-ray spectra were measured however they were unable to detect any impurity phases. In similar semiconducting oxides it was previously suggested that ferromagnetism could originate in oxygen vacancies or from disorder within the single crystal. To this end substrates were annealed in both air and vacuum in a range of temperatures (600°C to 1100°G) to both create bulk oxygen vacancies and to heal surface damage. Annealing in vacuum was found to create a measureable number of oxygen vacancies however their creation could not be correlated to the ferromagnetic signal of the substrate. Annealing in air was found to effect the remnant moment of the substrate as well as the width of the x-ray diffraction peaks on the unpolished face, weakly suggesting a relation between surface based disorder and ferromagnetism. Argon ion bombardment was employed to create a layer of surface disorder in the polished crystal, however it was not found to induce ferromagnetism. It was found that acid etching was sufficient to remove the ferromagnetism from as purchased samples and similarly simulated handling with stainless steel tweezers was sufficient to re-create the ferromagnetism. It is suggested that the origin of this ferromagnetism in SrTi03 is surface contaminants (mainly iron).

A study of the preparation and characterization of bismuth telluride and bismuth oxide thin films

This thesis deals with the preparation and properties of two compounds of V-II family, viz. bismuth telluride and bismuth oxide, in thin filmform. In the first chapter is given the resume of basic solid state physics relevant to the work reported here. In the second chapter the different methods of thin film preparationtia described. Third chapter deals with the experimental techniques used for preparation and characterization of the films. Fourth chapter deals with the preparation and propertiesof bismuth telluride films. In next four chapters, the preparation and properties of bismuth oxide films are discussed in detail. In the last chapter the use of Bi205 films in the fabrication of Heat mirrors is examined and discussed.

Predicted properties of the superheavy elements. III. Element 115, Eka-Bismuth

Element 115 is expected to be in group V-a of the periodic table and have most stable oxidation states of I and III. The oxidation state of I, which plays a minor role in bismuth chemistry, should be a major factor in 115 chemistry. This change will arise because of the large relativistic splitting of the spherically symmetric 7p_l/2 shell from the 7P_3/2 shell. Element 115 will therefore have a single 7p_3/2 electron outside a 7p^2_1/2 closed shell. The magnitude of the first ionization energy and ionic radius suggest a chemistry similar to Tl^+. Similar considerations suggest that 115^3+ will have a chemistry similar to Bi^3+. Hydrolysis will therefore be easy and relatively strongly complexing anions of strong acids will be needed in general to effect studies of complexation chemistry. Some other properties of 115 predicted are as follows: ionization potentials I 5.2 eV, II 18.1 eV, III 27.4 eV, IV 48.5 eV, 0 \rightarrow 5^+ 159 eV; heat of sublimation, 34 kcal (g-atom)^-1; atomic radius, 2.0 A; ionic radius, 115^+ 1.5 A, 115^3+ 1.0 A; entropy, 16 cal deg^-1 (g-atom)^-l (25°); standard electrode potential 115^+ |115, -1.5 V; melting and boiling points are similar to element 113.

Influence of ceria addition on thermal properties and local structure of bismuth germanate glasses

Bismuth germanate glasses are interesting materials due to their physical properties and their unique structural characteristics caused by the coordination changes of bismuth and germanium atoms. Glasses of the bismuth germanate system were prepared by melting/molding method and were investigated concerning their thermal and structural properties. The structural analysis of the samples was carried out by micro-Raman and Fourier transform infrared spectroscopes. It was observed that the glass structure is formed basically by GeO(4) tetrahedral units also having the formation of the GeO(6) octahedral units. BiO(2) was considered a network former by observing the presence of octahedral BiO(6) and pyramidal BiO(3) groups in the local structure of the samples. An absorption band observed at 1103 cm(-1) in the IR spectrum of the undoped glass was attributed to the Bi-O-Ge and/or Bi-O-Bi linkage vibration. The said band shifted to lower wavenumbers after the CeO(2) addition thus reflecting changes in the glass network. Cerium oxide was an efficient oxidant agent to prevent the darkening of the glasses which was probably associated to the reduction of Bi ions. However, CeO(2) was incorporated as a local network modifier in the glass structure even at concentrations of 0.2 mol%. (C) 2010 Elsevier B.V. All rights reserved.

Bismuth germanate films prepared by Pechini method

Bismuth germanate films were prepared by dip coating and spin coating techniques and the dependence of the luminescent properties of the samples on the resin viscosity and deposition technique was investigated. The resin used for the preparation of the films was obtained via Pechini method, employing the precursors Bi(2)O(3) and GeO(2). Citric acid and ethylene glycol were used as chelating and cross-linking agents, respectively. Results from X-ray diffraction and Raman spectroscopy indicated that the films sintered at 700 degrees C for 10 h presented the single crystalline phase Bi(4)Ge(3)O(12). SEM images of the films have shown that homogeneous flat films can be produced by the two techniques investigated. All the samples presented the typical Bi(4)Ge(3)O(12) emission band centred at 505 nm. Films with 3.1 mu m average thickness presented 80% of the luminescence intensity registered for the single crystal at the maximum wavelength. Published by Elsevier B.V.

Preparation and structural characterization of rare-earth doped lead lanthanum zirconate titanate ceramics

A new preparation route towards rare-earth (RE) doped polycrystalline lead lanthanum zirconate titanate (PLZT) ceramics (RE = Y(3+), Nd(3+), Yb(3+)), based on the use of doped lanthanum oxide or zirconia, is reported. Structural characterization by X-ray powder diffraction reveals that secondary phase formation can be substantially diminished in comparison to conventional preparation methods. The distribution of the rare-earth dopants was investigated as a function of concentration by static (207)Pb spin echo NMR spectra, using Fourier Transformation of Carr-Purcell-Meiboom-Gill spin echo trains. For the Nd- and Yb-doped materials, the interaction of the (207)Pb nuclei with the unpaired electron spin density results in significant broadening and shifting of the NMR signal, whereas these effects are absent in the diamagnetic Y(3+) doped materials. Based on different concentration dependences of the NMR lineshape parameters, we conclude that the structural role of the Nd(3+) dopants differs significantly from that of Yb(3+). While the Nd(3+) ions appear to be statistically distributed in the PLZT lattice, incorporation of Yb(3+) into PLZT appears to be limited by the appearance of doped cubic zirconia as a secondary phase. (C) 2009 Elsevier Masson SAS. All rights reserved.

Solid state NMR as a new approach for the structural characterization of rare-earth doped lead lanthanum zirconate titanate laser ceramics

To facilitate the design of laser host materials with optimized emission properties, detailed structural information at the atomic level is essential, regarding the local bonding environment of the active ions (distribution over distinct lattice sites) and their extent of local clustering as well as their population distribution over separate micro- or nanophases. The present study explores the potential of solid state NMR spectroscopy to provide such understanding for rare-earth doped lead lanthanum zirconate titanate (PLZT) ceramics. As the NMR signals of the paramagnetic dopant species cannot be observed directly, two complementary approaches are utilized: (1) direct observation of diamagnetic mimics using Sc-45 NMR and (2) study of the paramagnetic interaction of the constituent host lattice nuclei with the rare-earth dopant, using Pb-207 NMR lineshape analysis. Sc-45 MAS NMR spectra of scandium-doped PLZT samples unambiguously reveal scandium to be six-coordinated, suggesting that this rare-earth ion substitutes in the B site. Static Pb-207 spin echo NMR spectra of a series of Tm-doped PLZT samples reveal a clear influence of paramagnetic rare-earth dopant concentration on the NMR lineshape. In the latter case high-fidelity spectra can be obtained by spin echo mapping under systematic incrementation of the excitation frequency, benefiting from the signal-to-noise enhancement afforded by spin echo train Fourier transforms. Consistent with XRD data, the Pb-207 NMR lineshape analysis suggests that statistical incorporation into the PLZT lattice occurs at dopant levels of up to 1 wt.% Tm3+, while at higher levels the solubility limit is reached. (C) 2008 Elsevier Masson SAS. All rights reserved.