MXenes are a class of two-dimensional inorganic compounds composed of layers of transition metal carbides, nitrides, or carbonitrides. They have many desirable properties including hardness, high melting points, oxidation resistance, and high electrical and thermal conductivity. Common synthesis methods involve selectively etching MAX precursor phases, which are hexagonal layered transition metal carbides and/or nitrides. MXenes show potential for applications as sensors due to their hydrophilic surfaces, high surface areas, and ability to host intercalants.

1. Introduction
MXenes are a class of two-dimensional inorganic compounds. These materials consist of few-atoms-thick layers of
transition metal carbides, nitrides, or carbonitrides
Properties:
 Hardness
 High melting point
 Excellent oxidation resistance
 High electrical and thermal conductivity
 Hydrophilic nature
 High surface area
 Capability to host a broad range of intercalants
 Low diffusion barrier
 Biocompatibility
https://en.wikipedia.org/wiki/MXenes#/media/File:SEM_of_MXene.png
J. Mater. Chem. A, 2018,6, 1865-1865

2. MAX phases are a large family of hexagonal layered transition metal carbides and/ or
nitrides with composition of Mn+1AXn, where,
M= Early transition metal
A= Elements from group 13 and 14
X= C or N atoms
Precursor: MAX Phase

3. Synthesis
Adv. Mater. 26 (2014) 992e1005.
ACS Nano 6 (2012) 1322-1331.
The most commonly adopted selective etching
and surface functionalization process using
HF can be described by the following equations:

4. Application: Sensors
• Amperometric response of Hb-naf-
MXene/GCE biosensor with increasing
concentration of H2O2 at 0.35 V
• Detection limit of 20 nM for H2O2
J. Electrochem. Soc. 162 B16
Electrochemical Sensors Gas Sensors
Ti2CO2 MXene based sensor for NH3 detection, (b) adsorption energies
of different gases at MXene surface, (c) Schematic sensing mechanism
of NH3 at Ti3C2 MXene.
Acs Appl. Mater. Interfaces 9 (2017) 37184e37190.