Electronic Properties of h-WO3 and CuWO4 Nanocrystalsas Determined from X-ray Spectroscopy and First-Principles Band-Structure Calculations

Atuchin, Victor V.; Troitskaia, I. B.; Khyzhun, O.Y.; Bekenev, V.L.; Solonin, Yu. М.

doi:10.7763/ijapm.2011.v1.4

Cited by 16 publications

(10 citation statements)

References 44 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…10 we can find the energy-band dispersion for MnWO 4 at ambient pressure and 10 GPa. Wolframites with unfilled d A 2+ cations present indirect band gaps, 48 top of the valence band remains at the same energy. This is translated into a band-gap increase for the MgWO 4 and a band-gap decrease for the MnWO 4 , which is in agreement with the type of band-gap behavior previously reported for CuWO 4 .…”

Section: Energy-band Dispersionsmentioning

confidence: 97%

Pressure effects on the electronic and optical properties ofAWO4wolframites (A =

et al. 2012

View full text Add to dashboard Cite

The electronic band-structure and band-gap dependence on the d character of A 2+ cation in AWO 4 wolframitetype oxides is investigated for different compounds (A = Mg, Zn, Cd, and Mn) by means of optical-absorption spectroscopy and first-principles density-functional calculations. High pressure is used to tune their properties up to 10 GPa by changing the bonding distances establishing electronic to structural correlations. The effect of unfilled d levels is found to produce changes in the nature of the band gap as well as its pressure dependence without structural changes. Thus, whereas Mg, Zn, and Cd, with empty or filled d electron shells, give rise to direct and wide band gaps, Mn, with a half-filled d shell, is found to have an indirect band gap that is more than 1.6 eV smaller than for the other wolframites. In addition, the band gaps of MgWO 4 , ZnWO 4 , and CdWO 4 blue-shift linearly with pressure, with a pressure coefficient of approximately 13 eV/GPa. However, the band gap of multiferroic MnWO 4 red-shifts at −22 meV/GPa. Finally, in MnWO 4 , absorption bands are observed at lower energy than the band gap and followed with pressure based on the Tanabe-Sugano diagram. This study allows us to estimate the crystal-field variation with pressure for the MnO 6 complexes and how it affects their band-gap closure.

show abstract

Section: Energy-band Dispersionsmentioning

confidence: 97%

Pressure effects on the electronic and optical properties ofAWO4wolframites (A =

et al. 2012

View full text Add to dashboard Cite

show abstract

“…7 a). The upward movement in the VB position indicates a decrease in the band gap, which results in an increased visible-light absorption range [ 98 ]. However, the composition of the CB is still a topic of hot debate.…”

Section: Ternary Mwo 4 Photocatalysts (M = Bivalenmentioning

confidence: 99%

Nanostructured Ternary Metal Tungstate-Based Photocatalysts for Environmental Purification and Solar Water Splitting: A Review

et al. 2018

View full text Add to dashboard Cite

Visible-light-responsive ternary metal tungstate (MWO4) photocatalysts are being increasingly investigated for energy conversion and environmental purification applications owing to their striking features, including low cost, eco-friendliness, and high stability under acidic and oxidative conditions. However, rapid recombination of photoinduced electron–hole pairs and a narrow light response range to the solar spectrum lead to low photocatalytic activity of MWO4-based materials, thus significantly hampering their wide usage in practice. To enable their widespread practical usage, significant efforts have been devoted, by developing new concepts and innovative strategies. In this review, we aim to provide an integrated overview of the fundamentals and recent progress of MWO4-based photocatalysts. Furthermore, different strategies, including morphological control, surface modification, heteroatom doping, and heterojunction fabrication, which are employed to promote the photocatalytic activities of MWO4-based materials, are systematically summarized and discussed. Finally, existing challenges and a future perspective are also provided to shed light on the development of highly efficient MWO4-based photocatalysts.

show abstract

“…Currently, the scientific studies on the electronic properties of pure and doped CuWO 4 have been mainly focused on the photocatalytic (PC) degradation of organic dyes (Rhodamine B, eosin yellow dye and methylene blue) under ultraviolet and visible light [53][54][55], magnetic [56][57][58][59], photoelectrochemical water splitting [60][61][62][63][64], visible and solar-assisted water splitting [65,66], photoanode for solar water oxidation [67,68], electrical transport [69], and photoluminescence (PL) [24,53,70]. An important point to be considered is that the theoretical studies [16,[71][72][73][74][75], performed by means of ab initio calculations based on the density-functional theory (DFT) for the electronic structure of CuWO 4 crystals, have shown that the conduction band (CB) of this oxide is composed of 3d orbitals (Cu atoms) and 5d orbitals (W atoms), while the valence band (VB) is formed of 2p orbitals (O atoms).…”

Section: Introductionmentioning

confidence: 99%

Structural evolution, growth mechanism and photoluminescence properties of CuWO4 nanocrystals

Souza

Sczancoski

Nogueira

et al. 2017

Ultrasonics Sonochemistry

View full text Add to dashboard Cite

Copper tungstate (CuWO) crystals were synthesized by the sonochemistry (SC) method, and then, heat treated in a conventional furnace at different temperatures for 1h. The structural evolution, growth mechanism and photoluminescence (PL) properties of these crystals were thoroughly investigated. X-ray diffraction patterns, micro-Raman spectra and Fourier transformed infrared spectra indicated that crystals heat treated and 100°C and 200°C have water molecules in their lattice (copper tungstate dihydrate (CuWO·2HO) with monoclinic structure), when the crystals are calcinated at 300°C have the presence of two phase (CuWO·2HO and CuWO), while the others heat treated at 400°C and 500°C have a single CuWO triclinic structure. Field emission scanning electron microscopy revealed a change in the morphological features of these crystals with the increase of the heat treatment temperature. Transmission electron microscopy (TEM), high resolution-TEM images and selected area electron diffraction were employed to examine the shape, size and structure of these crystals. Ultraviolet-Visible spectra evidenced a decrease of band gap values with the increase of the temperature, which were correlated with the reduction of intermediary energy levels within the band gap. The intense photoluminescence (PL) emission was detected for the sample heat treat at 300°C for 1h, which have a mixture of CuWO·2HO and CuWO phases. Therefore, there is a synergic effect between the intermediary energy levels arising from these two phases during the electronic transitions responsible for PL emissions.

show abstract

Electronic Properties of h-WO3 and CuWO4 Nanocrystalsas Determined from X-ray Spectroscopy and First-Principles Band-Structure Calculations

Abstract: Abstract-The electronic structure of hexagonal WO 3 and triclinic CuWO 4 nanocrystals, prospective materials for functional electronic devices, has been studied using the X-ray photoelectron spectroscopy (XPS) and X-ray emission spectroscopy (

Cited by 16 publications

References 44 publications

Pressure effects on the electronic and optical properties ofAWO4wolframites (A =

Pressure effects on the electronic and optical properties ofAWO4wolframites (A =

Nanostructured Ternary Metal Tungstate-Based Photocatalysts for Environmental Purification and Solar Water Splitting: A Review

Structural evolution, growth mechanism and photoluminescence properties of CuWO4 nanocrystals

Contact Info

Product

Resources

About