Polymer encapsulation via initiated chemical vapor deposition (iCVD) to enhance stability of TiCT MXene-based formaldehyde sensors.

MXene is a class of compounds known for its superior electrical properties and versatile surface chemistries. However, its susceptibility to oxidation-induced degradation under ambient conditions prevents its incorporation into devices. In this work, we enhance the stability of MXene-based devices through encapsulation. We developed a sensor based on a heterojunction of TiCT MXene and silver nanoparticles for formaldehyde detection. This sensor is then encapsulated in poly(1,3,5,7-tetravinyl-1,3,5,7-tetramethylcyclotetrasiloxane) deposited via initiated chemical vapor deposition. Encapsulation substantially improved sensor stability, extending the half life span by more than 200%. These findings were reinforced by molecular dynamic simulations. Furthermore, upon hydration, siloxane in the encapsulant forms silanol which reacts with formaldehyde and boosts sensitivity by 1.7 times. We also demonstrate a rapid, low-energy regeneration process that enables the sensor to attain up to 90% of its previous response after degradation. These enhancements position this sensor as a reliable solution for real-time formaldehyde detection, in applications ranging from indoor air quality monitoring to industrial safety.