MXenes, two‐dimensional (2D) transition metal carbides and/or nitrides, possess surface termination groups such as hydroxyl, oxygen, and fluorine, which are available for surface functionalization. Their surface chemistry is critical in many applications. This article reports amine functionalization of Ti3C2Tx MXene surface with [3‐(2‐aminoethylamino)‐propyl]trimethoxysilane (AEAPTMS). Characterization techniques such as X‐ray photoelectron spectroscopy verify the success of the surface functionalization and confirm that the silane coupling agent bonds to Ti3C2Tx surface both physically and chemically. The functionalization changes the MXene surface charge from −35 to +25 mV at neutral pH, which allows for in situ preparation of self‐assembled films. Further, surface charge measurements of the functionalized MXene at different pH values show that the functionalized MXene has an isoelectric point at a pH around 10.7, and the highest reported positive surface charge of +62 mV at a pH of 2.58. Furthermore, the existence of a mixture of different orientations of AEAPTMS and the simultaneous presence of protonated and free amine groups on the surface of Ti3C2Tx are demonstrated. The availability of free amine groups on the surface potentially permits the fabrication of crosslinked electrically conductive MXene/epoxy composites, dye adsorbents, high‐performance membranes, and drug carriers. Surface modifications of this type are applicable to many other MXenes.
The excellent conductivity
and versatile surface chemistry of MXenes
render these nanomaterials attractive for sensor applications. This
mini-review puts recent advances in MXene-based sensors into perspective
and provides prospects for the area. It describes the attractive properties
and the working principles of MXene-based sensors fabricated from
a MXene/polymer nanocomposite or a pristine MXene. The importance
of surface modification of MXenes to improve their affinity for polymers
and to develop self-healing and durable sensors is delineated. Several
novel sensor fabrication methods and their challenges are discussed.
Emerging applications of MXene-based sensors including moisture, motion,
gas, and humidity detection as well as pressure distribution mapping
are critically reviewed. Potential applications of MXene-based sensors
in the food industry to monitor food materials and production plants
are highlighted.
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