Phase-switchable preparation of solution-processable WS2 mono- or bilayers
The crystal phase plays a crucial role in determining the properties of two-dimensional (2D) transition metal dichalcogenides. SKLMP Member Prof. Zhiyuan Zeng from City University of Hong Kong, collaborated with Prof. Xinge Yu from City University of Hong Kong, Prof. Ju Li from MIT, Prof. Meng Gu from the Eastern Institute of Technology, as well as many other researchers, to conduct relevant experiments and published their research findings in the journal Nature Synthesis.
The research team discovered that by controlling the discharge current density and cutoff voltage, and utilizing an electrochemical lithium-ion intercalation-based exfoliation strategy, they successfully achieved phase-switchable preparation of 2D transition metal dichalcogenides. A small discharge current density (0.005 A g⁻¹, cutoff voltage 0.9 V) could produce a pure semiconducting 2H phase WS2 bilayers, while a large discharge current density (0.02 A g⁻¹, cutoff voltage 0.7 V) leads to the dominant semimetallic 1T′phase WS2 monolayers. Through techniques such as cryo-electron microscopy, annular dark-field scanning transmission electron microscopy, and Raman, the researchers clarified the mechanism behind phase-switchable preparation. These findings inject new vitality into the current electrochemical Li⁺ intercalation-based exfoliation strategy, rendering it a feasible method for large-scale production of solution-processable group-VI 2D transition metal dichalcogenides (WS2) with designated phases.
More information: https://doi.org/10.1038/s44160-024-00679-2