Advances in the engineering of MXenes-based sensors: A transition towards advanced sensing technologies

MXenes are a two-dimensional group that have opened a new frontier in science, as their real-world applications are far-reaching, including batteries, supercapacitors, catalysts, electronics, and optics. MXenes possess adjustable electrical properties, high conductivity, and plenty of surface functional groups, compelling them to be extremely attractive for gas sensing applications. This review provides a comprehensive analysis of recent advancements in MXene-based gas sensors, emphasizing environmentally friendly synthesis methods that are replacing traditional HF etching. The properties of MXenes, encompassing their optical, thermal, mechanical, and gas-sensing characteristics, were discussed. Furthermore, the review examines modifications aimed at enhancing sensing capabilities, including functional group control, defect engineering, heterostructure formation, light assistance, and noble metal doping. Each enhancement method is systematically compared in terms of advantages and limitations. The advantages and limitations of each gas-sensing enhancement method were conveniently tabulated for ease of comparison. A computational analysis of the conductivity of an MXene based on the first principle DFT analysis on Ti₃C₂Tx is also discussed. A principle component analysis, which is used in machine learning and data analysis to identify patterns in complex datasets and identify which variables are most important, was discussed. The encore of this review discusses self-powered gas sensors, their integration into the Internet of Things (IoT), and the commercial viability and scalability of gas sensors, with a detailed analysis of their application in the fish market. The review concludes by addressing existing challenges and future directions in MXene-based gas sensors, underscoring the need for improved synthesis techniques, a better understanding of sensing mechanisms, and strategies for long-term material stability.