Tungsten Diselenide Powder
|Molecular weight||341.76 g/mol|
|Bandgap||1.4 - 2.01 eV |
|Synonyms||Tungsten Selenide, Tungsten (IV) Selenide|
|Classification / Family||Transition metal dichalcogenides (TMDCs), 2D Semiconductor Materials, NIR band-gap, Nano-electronics, Nano-photonics, Transistors, Photovoltaics, Materials Science|
|Preparation||Synthetic - Chemical Vapour Transport (CVT)|
|Electronic properties||2D semiconductor|
|Melting point||> 1200 °C|
Like WS2 and other TMDCs, 2-dimensional layered tungsten diselenide (WSe2) has a 2H (semiconducting) structure. This structure is the more stable form of the two hexagonal phases that exist in the naturally-occurring bulk-material forms. A 1T octahedral phase also exists - this is metallic in nature and is only associated with single layer films. Monolayer, few-layer nanosheet structures, and nanoparticles can be prepared by mechanical or chemical exfoliation.
The 2H-WSe2 phase has a hexagonal symmetry, with a trigonal prismatic metal coordination, where layers of selenium atoms are stacked directly above one another. The 1T-WSe2 phase has a tetragonal symmetry, with an octahedral metal coordination, as the layers are offset from each other. It has been demonstrated that the phase change from 2H to 1T can happen via chemical treatments, such as lithium-assisted intercalation of bulk crystals or powder by liquid exfoliation.
The 1T-WSe2 phase is of particular interest for hydrogen evolution reactions (HER). Aside from that, exfoliated 2H-WSe2 nanosheets and particles play an important role in device applications such as transistors, photodetectors, light emitting diodes, photovoltaic solar cells, and in biomedical and photothermal therapies.
Tungsten diselenide (WSe2) powder is obtained by CVT with a purity over 99.995%.
WSe2 powder is suitable for liquid chemical exfoliation to prepare WSe2 nanoparticles and nanosheets down to few-layer films. High-purity WSe2 powders can also be used in chemical vapour deposition to create mono-layer films.
Literature and Reviews
- Layer-dependent electronic structure of an atomically heavy two-dimensional dichalcogenide, P-C. Yeh et al., Phys. Rev. B 91, 041407 (2015); DOI: 10.1103/PhysRevB.91.041407.
- Dynamic tungsten diselenide nanomaterials: supramolecular assembly-induced structural transition over exfoliated two-dimensional nanosheets, A. Muhabie et al., Chem. Sci., 9, 5452 (2018); DOI: 10.1039/c8sc01778f.
- 2H - 1T phase transition and hydrogen evolution activity of MoS2, MoSe2, WS2 and WSe2 strongly depends on the MX2 composition, A. Ambrosi et al., Chem. Commun., 51, 8450 (2015); DOI: 10.1039/c5cc00803d.
- Self-assembled 2D WSe2 thin films for photoelectrochemical hydrogen production, X. Yu et al., Nat Commun 6, 7596 (2015); DOI: 10.1038/ncomms8596.
- Atomic-layer triangular WSe2 sheets: synthesis and layer-dependent photoluminescence property, K. Xu et al, Nanotechnology 24, 465705 (2013); doi:10.1088/0957-4484/24/46/465705.
- Solution-Phase Synthesis of Highly Conductive Tungsten Diselenide Nanosheets, P. D. Antunez et al., Chem. Mater., 25, 2385−2387 (2013); DIO: 10.1021/cm400790z.