Fig 1

Applications of MXenes materials in various fields. (a) Device configuration of the planar PSCs and the energy-level diagram of the PSCs with and without Ti3C2Tx doping 12. Adapted with permission from Ref. 12. Copyright 2020, Elsevier B.V. (b) Schematic illustration of electromagnetic wave transfer across alternating multilayered CNF@MXene films 14. Adapted with permission from Ref. 14. Copyright 2020, American Chemical Society. (c) Schematic drawing showing the suggested sensing mechanism for the V2CTx gas sensor 15. Adapted with permission from Ref. 15. Copyright 2019, American Chemical Society. (d) Schematic of the working mechanism of MXene applied in photocatalysis 16. Adapted with permission from Ref. 16. Copyright 2019, Springer Nature. (e) Ti3C2/Au intracortical electrode array 18. Adapted with permission from Ref. 18. Copyright 2018, American Chemical Society. (f) A schematic of how Al3+ intercalates the two adjacent MXene layers and thus fixes the d-spacing. The hydrated cations, such as Na+, are rejected, while the water molecules can permeate through the membrane 19. Adapted with permission from Ref. 19. Copyright 2020, Springer Nature."

Fig 2

Schematic showing the preparation of MXenes materials."

Fig 3

Preparation and characterization of MXenes materials. (a) Schematic for the exfoliation process of MAX phase and formation of MXene 27. Adapted with permission from Ref. 27. Copyright 2012, American Chemical Society. (b) SEM micrograph for Ti3AlC2 after HF treatment 27. Adapted with permission from Ref. 27. Copyright 2012, American Chemical Society. (c) Schematic illustration of the synthesis of Ti4N3Tx by molten salt 40. Adapted with permission from Ref. 40. Copyright 2016, The Royal Society of Chemistry. (d) AFM image of a folded Ti3C2Tx flake on Si/SiO2. The inset shows the height profile measured along the red dashed line 33. Adapted with permission from Ref. 33. Copyright 2016, Wiley-VCH. (e) The delaminated Ti3C2Tx SEM image 45. Adapted with permission from Ref. 45. Copyright 2018, Wiley-VCH. (f) Low-magnification HAADF-STEM image of a hexagonal 2D α-Mo2C crystal 47. (g) SAED pattern of a hexagonal 2D α-Mo2C crystal along the [100] zone axis 47. Adapted with permission from Ref. 47. Copyright 2015, Nature Publishing Group."

Table 1

Comparison of advantages and disadvantages of different etching methods."

Fig 4

Various properties of MXenes materials. (a) Strain–stress curves obtained for the Tin+1Cn samples during tensile loading 51. Adapted with permission from Ref. 51. Copyright 2015, IOP Publishing Ltd. (b) Comparison of effective Young's moduli for several 2D materials 52. Adapted with permission from Ref. 52. Copyright 2018, AAAS. (c) I–V curve of a monolayer Ti3C2Tx flake at 300 K and 2.5 K showing metallic behavior 54. Adapted with permission from Ref. 54. Copyright 2016, AIP Publishing LLC. (d) Reflectivity (top) and energy-loss spectra (bottom) of Ti3C2T2 MXene 60. Adapted from AIP Publishing LLC publisher. (e) Optical images of the Ti3C2Tx films on glass (top) and a flexible polyester substrate (bottom) 63. Adapted with permission from Ref. 63. Copyright 2016, Wiley-VCH. (f) Dispersions of 50% HF-etched Ti3C2Tx in the 12 solvents listed above 67. Adapted with permission from Ref. 67. Copyright 2017, American Chemical Society."

Fig 5

Preparation and characterization of MXenes-functionalized fibers. (a) MXene-coated cotton yarn knitted with half-gauge pattern resulted in a porous fabric, and MXene-coated cotton yarn knitted with interlock pattern resulted in a dense fabric 69. Adapted with permission from Ref. 69. Copyright 2019, Wiley-VCH. (b) Optical images of 10 meters of 2-ply MXene-coated cotton yarn (2-MX-Cot) and multifilament nylon fibers (1-MX-Nyl) and SEM images of the coated yarns 70. Adapted with permission from Ref. 70. Copyright 2020, Elsevier Ltd. (c) The mechanism of modified CF/PEEK composites 75. Adapted with permission from Ref. 75. Copyright 2020, Elsevier Ltd. (d) Schematic illustration of the custom-built wet spinning setup used to produce MXene/PEDOT: PSS fiber 82. Adapted with permission from Ref. 82. Copyright 2019, Wiley-VCH. (e) Typical tensile stress curves of single rGO and MXene/rGO fibers 84. Adapted with permission from Ref. 84. Copyright 2017, The Royal Society of Chemistry. (f) Photograph of a 5 m long Ti3C2Tx fiber successfully collected on a spool 86. Adapted from American Chemical Society publisher. (g) Cross-sectional SEM images of Ti3C2Tx fiber produced in the chitosan bath 86. Adapted from American Chemical Society publisher. (h) Schematic of the production of Ti3C2Tx MXene/carbon nanofibers via electrospinning 30. Adapted with permission from Ref. 30. Copyright 2019, The Royal Society of Chemistry. (i) Schematic of the bath electrospinning setup 93. Adapted with permission from Ref. 93. Copyright 2020, Wiley-VCH."

Table 2

Summary of the preparation methods and properties of MXenes-functionalized fibers."

Fig 6

MXenes-functionalized fibers for flexible sensors and energy storage devices. (a) Elbow sleeve knitted by using four-ply yarn of MXene/PU composite fiber 22. Adapted with permission from Ref. 22. Copyright 2020, Wiley-VCH. (b) Optical images showing a smart glove (top), and electrical signal output of the fiber strain sensors from the smart glove for monitoring different gestures of the five fingers (bottom) 71. Adapted with permission from Ref. 71. Copyright 2019, The Royal Society of Chemistry. (c) Sensor output responses to the spoken words 'Ah', 'MXene', 'Flexible' and 'Sensor' 92. Adapted with permission from Ref. 92. Copyright 2020, Elsevier Inc. (d) Schematic of preparing the M-fabric and the trilayer fabric device 97. Adapted with permission from Ref. 97. Copyright 2021, Wiley-VCH. (e) The gas selectivity comparison of rGO fiber and MXene/rGO hybrid fiber (40% (w) MXene) to various testing gases at concentrations of 50 ppm 83. Adapted with permission from Ref. 83. Copyright 2020, American Chemical Society (f) Schematic illustration of the preparation and application for tungstate/MXene fiber 104. Adapted with permission from Ref. 104. Copyright 2020, Elsevier B.V. (g) Photograph of the assembled six supercapacitors lighting up a LED 72. Adapted with permission from Ref. 72. Copyright 2017, Wiley-VCH. (h) Schematic illustration of the large-scale production of MXene and zinc-coated fbers and braided coaxial FSC 73. Adapted with permission from Ref. 73. Copyright 2021, Springer Nature."

Fig 7

Applications of MXenes-functionalized fibers in the field of functional wires and smart fabrics. (a) Ti3C2Tx MXene fiber applied as an electrical or earphone wire 24. Adapted with permission from Ref. 24. Copyright 2020, Nature Publishing Group. (b) Images showing changes in temperature distribution in the fiber under various applied voltages recorded using an infrared (IR) camera 86. Adapted from American Chemical Society publisher. (c) Schematic illustrating the fabrication of hydrophobic, permeable, and conductive silk textile with a vacuum-assisted layer-by-layer assembly approach 112. Adapted with permission from Ref. 112. Copyright 2019, Wiley-VCH. (d, e) Real-time sensing signal recording of the pressure sensor for different human physiological monitoring, including (d) breath and (e) wrist pulse 113. Adapted with permission from Ref. 113. Copyright 2020, Elsevier B.V. (f) Multiple applications of PMFs such as energy storage, strain sensing, EMI shielding and Joule heating 114. Adapted with permission from Ref. 114. Copyright 2021, The Royal Society of Chemistry."

Fig 8

Potential applications of MXenes-functionalized fibers."