PEDOT:PSS-Facilitated Directionally 3-D Assembled MXene-Based Aerogel for High-Performance Chemoresistive Sensing & Breath Analysis

MXene has garnered growing interest in the field of electrochemistry, thanks to its unique electrical and surface characteristics. Nonetheless, significant challenges persist in realizing its full potential in chemoresistive sensing applications. In this study, a novel unidirectional freeze-casting approach for fabricating a Poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS)-facilitated vertically aligned MXene-based aerogel with enhanced chemoresistive sensing properties was introduced. Firstly, the persistent challenge of poor gelation in MXene was addressed by formulating a nanohybrid of MXene and PEDOT:PSS, which acted as flexible conductive nanobinder. Employing a unique freeze-casting method, MXene flakes interconnected by PEDOT:PSS, were stabilized into a flexible, vertically aligned structure, leading to maximum surface exposure and enhanced robustness. The resulting 3-dimentional (3-D) aerogel exhibited a fast, heightened chemoresistive response of 7 to 50 parts per million (ppm) acetone and expanded the working range to between 10 parts per billion (ppb)-8000 ppm. Interfacial heterostructures formed between MXene and PEDOT:PSS, provided active sites, reduced activation energy, and enhanced selectivity. Modulated MXene bandgap, and its electron mobility further facilitated electron transfer, and enhanced signal strength. The sensor showed excellent biocompatibility and was also successfully employed as a breathalyzing tool, for on-demand alcohol consumption monitoring.