Article

Luminescence and phonon properties of nanocrystalline Bi2WO6:Eu3+ photocatalyst prepared from amorphous precursor.

Institute of Low Temperature and Structure Research, Polish Academy of Sciences, P.O. Box 1410, 50-950 Wrocław 2, Poland.
Journal of Nanoscience and Nanotechnology (Impact Factor: 1.34). 09/2010; 10(9):5746-54. DOI: 10.1166/jnn.2010.2465
Source: PubMed

ABSTRACT Bi2WO6:Eu3+ samples were prepared by mechanically activated metathesis reaction and subsequent annealing at different temperatures of the as-prepared precursor. X-ray, TEM, Raman, IR, diffuse reflectance and luminescence studies of the prepared samples are presented. It was found that variation of the particle size have significant impact on phonon and emission properties of this material. It was observed that intensity of some Raman and IR bands significantly decreases and the bandwidth of Raman, IR and Eu3+ emission lines significantly increases with decreasing particles size. Moreover, it was observed that intensity ratios I((5)D0-(7)F2)/I((5)D0-(7)F1) and I(5D0_(7)F0)/I((5)D0-(7)F1) increase with decreasing particle size. The observed changes were attributed to phonon confinement effect, decrease in the orthorhombic distortion of the unit cell and concentration increase of surface defects.

1 Bookmark
 · 
137 Views
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: This article represents data on the mechanochemical synthesis, characterization and catalytic properties of Bi2WO6 nanoparticles. The synthesis of Bi2WO6 nanopowder (10 nm) started after 90 min of milling time interval and it was completely finished after 4 h when using 2.5 g batch of the initial oxides. Longer milling time intervals (8 h) were needed to synthesize the target nanophase (4 nm), when using a 4.0 g batch of precursor oxides. The Bi2WO6 powders manifest low absorbance ability in the visible range with a band gap ranging from 2.85 to 2.88 eV. The catalytic activity was investigated in the reactions of CO, n-hexane and methane oxidation, respectively. The oxidation of CO on Bi2WO6 proceeds at temperatures higher than 200 �C, while the complete oxidation of n-hexane was found to occur at temperatures higher than 250 �C. A remarkable increase in the catalytic activity was achieved in the case of Bi2WO6 supported with 0.14 wt.% Pd. The promotional effect of Bi on the catalytic activity of the Pd loaded sample could be explained by the formation of alloy or inter-metallic phases (a-Bi2Pd and b-BiPd), which is considered as perspective for the development of a catalyst for treatment of methane emissions.
    Journal of Alloys and Compounds 09/2013; 570:34. · 2.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Polycrystalline samples of Bi2W1−xMexO6−y (Me = Nb, Ta) solid solutions have been prepared by solid-state reactions, and the influence of Nb and Ta substitutions for W on the polymorphism and electrical properties of Bi2WO6 has been studied. The limit of the solid solutions is at x = 0.1 for Me = Nb and at x = 0.15 for Me = Ta. The distinctive features of the polymorphism of the Nb- and Ta-doped materials have been identified. According to differential scanning calorimetry data, tantalum and niobium substitutions for tungsten increase the temperature of the high-temperature, orthorhombic-to-monoclinic reconstructive phase transition and suppress the transition starting at x = 0.05 for Me = Nb and x = 0.10 for Me = Ta. As a result, the Bi2W1−xNbxO6−y samples have an orthorhombic Aurivillius-type structure up to their melting point. The Bi2W1−xTaxO6−y solid solutions at high temperatures consist of a mixture of an orthorhombic and a monoclinic phase. Nb and Ta doping shifts the ferroelectric phase transition to lower temperatures by more than 200 °C, thus markedly extending the stability range of the nonpolar orthorhombic paraelectric phase, which exists in a temperature range as narrow as 930–960 °C in the case of undoped Bi2WO6. The increase in oxygen vacancy concentration due to heterovalent substitutions of Nb5+ and Ta5+ for W6+ leads to an increase in conductivity by two orders of magnitude relative to the unsubstituted compound.
    Journal of Alloys and Compounds 10/2013; 573:90–95. · 2.73 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Graphene/Bi2WO6 composites have been synthesized by hydrothermal reduction at 160°C for 24 h using ethanol as the reducing agent. All as‐prepared composites were characterized using X‐ray diffraction (XRD), UV–vis diffuse reflectance spectroscopy, FT‐IR spectroscopy, Raman spectroscopy, scanning electron microscopy, high‐resolution transmission electron microscopy, N2 adsorption, and photocatalytic activity evaluation. The effective charge separation of graphene/Bi2WO6 composites was caused by the electrical conduction of graphene which is the most important factor. The results have proved the formation of interfacial contact between graphene nanosheets and Bi2WO6 nanoplates. The adsorptivity for azo dyes was enhanced greatly with the introduction of graphene. The oxy‐functional groups located at the edges of graphene were responsible for the enhanced adsorptivity. As‐prepared graphene/Bi2WO6 composites exhibited enhanced light absorption from UV to visible‐light region. In addition, the introduction of graphene would also result in smaller crystalline size and lower crystallinity of Bi2WO6. Graphene/Bi2WO6 composites containing an appropriate amount of graphene were proved to exhibit higher adsorptivities and photocatalytic activities for azo dyes. High photocatalytic activities of graphene/Bi2WO6 composites were considered to be the synergetic effects of high adsorption, high light absorption, and high electrical conduction induced by the introduction of graphene.
    Journal of the American Ceramic Society 05/2013; 96(5). · 2.43 Impact Factor

Full-text (2 Sources)

Download
28 Downloads
Available from
May 21, 2014