Fabrication of Luminescent Monolayered Tungsten Dichalcogenides Quantum Dots with Giant Spin-Valley Coupling
- 3 September 2013
- journal article
- research article
- Published by American Chemical Society (ACS) in ACS Nano
- Vol. 7 (9), 8214-8223
- https://doi.org/10.1021/nn403682r
Abstract
A high yield (>36 wt %) method has been developed of preparing monolayered tungsten dichalcogenide (WS2) quantum dots (QDs) with lateral size similar to 8-15 nm from multilayered WS2 flakes. The monolayered WS2 QDs are, like monolayered WS2 sheets, direct semiconductors despite the flake precursors being an indirect semiconductor. However, the QDs have a significantly larger direct transition energy (3.16 eV) compared to the sheets (2.1 eV) and enhanced photoluminescence (PL; quantum yield similar to 4%) in the blue-green spectral region at room temperature. UV/vis measurements reveal a giant spin-valley coupling of the monolayered WS2 QDs at around 570 meV, which is larger than that of monolayered WS2 sheets (similar to 400 meV). This spin-valley coupling was further confirmed by PL as direct transitions from the conduction band minimum to split valence band energy levels, leading to multiple luminescence peaks centered at around 369 (3.36 eV) and 461 nm (2.69 eV, also contributed by a new defect level). The discovery of giant spin-valley coupling and the strong luminescence of the monolayered WS2 QDs make them potentially of interests for the applications in semiconductor-based spintronics, conceptual valley-based electronics, quantum information technology and optoelectronic devices. However, we also demonstrate that the fabricated monolayered WS2 QDs can be a nontoxic fluorescent label for high contrast bioimaging application.Keywords
This publication has 27 references indexed in Scilit:
- Extraordinary Room-Temperature Photoluminescence in Triangular WS2 MonolayersNano Letters, 2012
- Creating high yield water soluble luminescent graphene quantum dots via exfoliating and disintegrating carbon nanotubes and graphite flakesChemical Communications, 2012
- Transistors with chemically synthesized layered semiconductor WS2 exhibiting 105 room temperature modulation and ambipolar behaviorApplied Physics Letters, 2012
- Electronic Band Structures of Molybdenum and Tungsten Dichalcogenides by the GW ApproachThe Journal of Physical Chemistry C, 2012
- Phonons in single-layer and few-layer MoSand WSPhysical Review B, 2011
- Economical and effective sulfide catalysts for dye-sensitized solar cells as counter electrodesPhysical Chemistry Chemical Physics, 2011
- Recent developments of molybdenum and tungsten sulfides as hydrogen evolution catalystsEnergy & Environmental Science, 2011
- Identification of active atomic defects in a monolayered tungsten disulphide nanoribbonNature Communications, 2011
- Two-Dimensional Nanosheets Produced by Liquid Exfoliation of Layered MaterialsScience, 2011
- Fullerene‐like WS2 Nanoparticles: Superior Lubricants for Harsh ConditionsAdvanced Materials, 2003