process, it can be operated as a counter ion by self-assembling with conductive polymer

chains having positively charged to generate a conductive polymer film doped with

MXene at the molecular level on the electrode surface in a single step with great effi­

ciency. The MXene-doped conductive polymer has the potential to produce a better

electrode architecture for energy storage devices.

The purpose of this work is to present such an overview for Mxenes and MXene/

polymer nanocomposites. It gives an overview of the concept, preparation method, and

characteristics of MXene; this is followed by MXene/polymer nanocomposites, which

elaborates and narrates the preparation technique of the composites, summarizes the

properties of the material and details of a variety of applications, including enzyme and

non-enzyme sensing, biomedical, and bioelectronics. The last part provides a perspective

on the future and challenges for MXenes.

15.2 Synthesis of MXenes

MXenes are produced by the etching method through a wet chemical process that pro­

vides fewer defects in the atomic level and higher electronic conductivity according to

experiments. The method, however, is only applicable to carbon-based MXenes because

from nitride-based MAX phases it does not eliminate the A-layer. The first etching agent

employed was hydrofluoric acid (HF), which is toxic to the environment. As a result, the

necessity for diverse etchants arose. In 2014, a secured blend of lithium fluoride (LiF) and

hydrochloric acid (HCl) was introduced [7]. However, due to HF gas being created in-

situ, the problem remained. The problem was solved by the invention of several ways

that did not require the usage of HF. These techniques will be explained further.

15.2.1 Chemical Vapor Deposition

Methane was chosen as a source for carbon while Mo foil as a substrate and Cu foil on top

of Mo substrate has been devised by Xu et al. by a chemical vapor deposition (CVD)

technique to synthesize MXenes in 2015 [8]. They conducted their experiments at a

temperature of over 1,085°C or 1,358 K. The breakdown of chemicals on the substrate

surface causes the deposition of material layers from the vapor phase during CVD. Due to

the high temperature, the Cu foil melted, generating an alloy of molybdenum and copper.

Molybdenum atoms dispersed to the surface of the liquid Cu after reacting with the

C atoms generated by the breakdown of methane, forming Mo2C crystals.

Despite its MXene-like structure, the created material was a transition metal based 2D

carbide with a greater surface area when compared to the previously synthesized na­

nosheets. Xu et al. [8] created 2D very thin Mo2C crystals with lateral diameters more than

100 m and thicknesses of a few nanometers. The thickness has been altered by adjusting

the methane content. The resulting MXene material was defect-free, and its super­

conductivity remained stable after a few months in contact with air [8].

15.2.2 Hydrothermal Synthesis

Li et al. [9] described a method in which from the Ti3AlC2 MAX phase, Ti3C2Tx

MXene, can be obtained with the use of sodium hydroxide (NaOH) [10]. The

MXenes-Based Polymer Composites

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