Abstract
MXenes are a large family of two-dimensional materials that have attracted attention across many fields due to their desirable optoelectronic, biological, mechanical and chemical properties. There currently exist many synthesis procedures that lead to differences in flake size, defects and surface chemistry, which in turn affect their properties. Herein, we describe the steps to synthesize Ti3C2Tx—the most important and widely used MXene, from a Ti3AlC2 MAX phase precursor. The procedure contains three main sections: synthesis of Ti3AlC2 MAX, wet chemical etching of the MAX in hydrofluoric acid/HCl solution to yield multilayer Ti3C2Tx and its delamination into single-layer flakes. Three delamination options are described; these use LiCl, tertiary amines (tetramethyl ammonium hydroxide/ tetrabutyl ammonium hydroxide) and dimethylsulfoxide respectively. These procedures can be adapted for the synthesis of MXenes beyond Ti3C2Tx. The MAX phase synthesis takes about 1 week, with the etching and delamination each requiring 2 d. This protocol requires users to have experience working with hydrofluoric acid, and it is recommended that users have experience with wet chemistry and centrifugation; characterization techniques such as X-ray diffraction and particle size analysis are also essential for the success of the protocol. While alternative synthesis methods, such as minimally intensive layer delamination, are desirable for certain MXenes (such as Ti2CTx) or specific applications, this protocol aims to standardize the more commonly used hydrofluoric acid/HCl etching method, which produces Ti3C2Tx with minimal concentration of defects and the highest conductivity and serves as a guideline for those working with MXenes for the first time.
Key points
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MXenes are two-dimensional materials, the best known of which is Ti3C2Tx. Many diverse and unique properties have been described for MXenes, but it is difficult to compare the data because their physical characteristics depend on their synthesis.
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This protocol provides a detailed guideline for the synthesis of a Ti3AlC2 MAX phase precursor, wet chemical etching of MAX to yield multilayer Ti3C2Tx and its delamination into single-layer flakes.
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Data availability
The data from experiments are summarized in Supporting Information. All data of importance for this protocol have been included either in the main manuscript or supporting information.
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Acknowledgements
This work was supported by the US National Science Foundation, grant CHE- 2318105. The authors affirm the human participants provided informed consent for publication for Supplementary Fig. 4. R.J. Wang is thanked for proofreading the manuscript. XRD and SEM analyses were performed using instruments in the Materials Characterization Core at Drexel University.
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M.D., C.E.S. and Y.G. conceived the experimental plan. B.M. and J.B. took the experimental setup photographs for figures and measured film conductivity. M.D., C.E.S. and B.M. synthesized the large batch to test the different delaminating agents. M.D. and C.E.S. prepared the MAX phase precursors, performed XRD characterization and drafted the manuscript. M.D. and B.M. performed the DLS measurements. All authors reviewed and edited the final manuscript.
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Key references using this protocol
Naguib, M. et al. Adv. Mater. 23, 4248–4253 (2011): https://doi.org/10.1002/adma.201102306
Alhabeb, M. et al. Chem. Mater. 29, 7633–7644 (2017): https://doi.org/10.1021/acs.chemmater.7b02847
Shekhirev, M. et al. Prog. Mater. Sci. 120, 100757 (2021): https://doi.org/10.1016/j.pmatsci.2020.100757
Mathis, T. S. et al. ACS Nano 15, 6420–6429 (2021): https://doi.org/10.1021/acsnano.0c08357
Shuck, C. E. et al. ACS Chem. Health Saf. 28, 326–338 (2021): https://doi.org/10.1021/acs.chas.1c00051
Sarycheva, A. et al. ACS Nano, 16, 6858–6865 (2022): https://doi.org/10.1021/acsnano.2c01868
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Downes, M., Shuck, C.E., McBride, B. et al. Comprehensive synthesis of Ti3C2Tx from MAX phase to MXene. Nat Protoc (2024). https://doi.org/10.1038/s41596-024-00969-1
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DOI: https://doi.org/10.1038/s41596-024-00969-1
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