Abstract
Crystal phase plays a crucial role in determining the properties of two-dimensional (2D) transition metal dichalcogenides. Here we achieve phase-switchable preparation of 2D transition metal dichalcogenides using an electrochemical lithium-ion intercalation-based exfoliation strategy by controlling the discharge current density and cutoff voltage. We discover that a small discharge current density (0.005 A g−1, with a 0.9 V cutoff voltage) produces pure semiconducting 2H phase WS2 bilayers. In contrast, a large discharge current density (0.02 A g−1, with a 0.7 V cutoff voltage) leads to the dominant semimetallic 1T′ phase WS2 monolayers. The phase-switching mechanism was clarified through cryo-electron microscopy, annular dark-field scanning transmission electron microscopy, Raman, X-ray photoelectron spectroscopy, etc. The device (humidity sensor) application of produced 2D WS2 was then demonstrated, showing phase-dependent humidity-sensing performances confirming the potential of our produced 2D WS2 with switchable phase in device applications.
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Acknowledgements
Z.Zeng thanks the Young Collaborative Research Grant (project no. C1003-23Y) and General Research Fund (GRF) (project no. CityU11308923) support from the Research Grants Council of the Hong Kong Special Administrative Region, China, the Basic Research Project from Shenzhen Science and Technology Innovation Committee in Shenzhen, China (project no. JCYJ20210324134012034), and the Applied Research Grant of City University of Hong Kong (project no. 9667247) and Chow Sang Sang Group Research Fund of City University of Hong Kong (project no. 9229123). Z.Zeng also thanks the funding supported by the Seed Collaborative Research Fund Scheme of State Key Laboratory of Marine Pollution, which receives regular research funding from Innovation and Technology Commission (ITC) of the Hong Kong SAR Government. However, any opinions, findings, conclusions or recommendations expressed in this publication do not reflect the views of the Hong Kong SAR Government or the ITC. X.Y. thanks the support from Research Grants Council of the Hong Kong Special Administrative Region (grant no. RFS2324-1S03) and Shenzhen Science and Technology Innovation Commission (grant no. SGDX20220530111401011). M.G. acknowledges the support from Guangdong Fundamental Research Association (project no. 2022B1515120013), National Natural Science Foundation of China (project no. 52273225) and Guangdong scientific programme (contract no. 2019QN01L057). L.G. thanks the funding support from National Natural Science Foundation of China (project nos. 52250402, 51991344 and 52025025).
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Z. Zeng conceived and guided the project. L.M. designed and performed the synthesis and characterizations of all the materials. Z.G. and X.G.Y. performed the device fabrication and performance test. D.L., T.Y., H.H., J.Z., D.V. and Y.C. helped to analyse the results. Z. Zhang and M.D.G. carried out the cryo-electron microscopy test. M.S., X.L., Y.Z., B.H. and X.C.Z. conducted the DFT calculations. Q.Z. and L.G. performed the HAADF-STEM test of the samples. L.M., Z.G., R.Y., J.L., X.Y. and Z. Zeng drafted the paper. All authors checked the paper and agreed with its content.
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Nature Synthesis thanks Qiaoliang Bao and the other, anonymous, reviewer(s) for their contribution to the peer review of this work. Primary Handling Editor: Alexandra Groves, in collaboration with the Nature Synthesis team.
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Supplementary Information
Supplementary Figs. 1–47 and Tables 1 and 2.
Source data
Source Data Fig. 1
Unprocessed characterization data for 2H and 1T′-WS2.
Source Data Fig. 3
Unprocessed humidity sensor performance data for 2H and 1T′-WS2.
Source Data Fig. 4
Unprocessed humidity sensor array performance data for 2H-WS2.
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Mei, L., Gao, Z., Yang, R. et al. Phase-switchable preparation of solution-processable WS2 mono- or bilayers. Nat. Synth 4, 303–313 (2025). https://doi.org/10.1038/s44160-024-00679-2
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DOI: https://doi.org/10.1038/s44160-024-00679-2
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