Recent advances in 2D MXene-based heterostructures for gas sensing: mechanisms and applications in environmental and biomedical fields.

MXenes, a unique class of 2D transition metal carbides, have gained attention for gas sensing applications due to their distinctive properties. Since the synthesis of Ti3C2Tx MXene in 2011, significant progress has been made in using MXenes as chemiresistive sensors. Their layered structure, abundant surface groups, hydrophilicity, tunable conductivity, and excellent thermal properties make MXenes ideal for low-power, flexible, room temperature gas sensors, fostering scalable and reproducible applications in portable devices. This review evaluates the latest advancements in MXene-based gas sensors, beginning with an overview of the elemental compositions, structures, and typical fabrication process of MXenes. We subsequently examine their applications in gas sensing domains, evaluating the proposed mechanisms for detecting common volatile organic compounds such as acetone, formaldehyde, ethanol, ammonia, and nitrogen oxides. To set this apart from similar reviews, our focus centered on the mechanistic interactions between MXene sensing materials and analytes (particularly for chemiresistive gas sensors), leveraging the distinct functionalities of MXene chemistries, which can be finely tuned for specific applications. Ultimately, we examine the current limitations and prospective research avenues concerning the utilization of MXenes in environmental and biomedical applications.