Highly Flexible, Selective and Sensitive Ammonia Sensor Based on MXene/Cellulose Nanofibers.

Flexible electronics have become imperative in an emerging era of the Internet of Things (IoT), as they offer promising alternatives to rigid and complex circuitry for the development of wearable devices. As a result, the research field of flexible gas sensors is increasingly being investigated, including different potential materials, with the aim of high selectivity and sensitivity. In this study, a flexible ammonia (NH₃) sensor unit was fabricated using cellulose nanofibers (C-NFs) as a flexible supporting framework and sensing material coating of Ti₃C₂T_x MXene. The fabricated sensor displayed higher selectivity to NH₃ relative to other interferents in the ppm concentration range. The results revealed that the MXene/C-NFs-based sensor exhibited a response of 2.4% towards 5 ppm NH₃ with faster response and recovery times of 42 s and 69 s, respectively, which were improved relative to a pristine MXene-based sensor with sensing response of 1.42% and response/recovery time of 67 s/104 s. This enhanced sensing performance was ascribed to the large specific surface area and efficient charge transport pathways provided by the one-dimensional structure of C-NFs, which facilitated the surface adsorption/desorption of NH₃ molecules. In addition, the fabricated sensor demonstrated excellent flexibility features and reproducible sensing properties at different bending angles and bending cycles, with low sensing response attenuation of 5.2% under a maximum bending angle of 120°. Overall, this work illustrates the feasibility of employing a nanofiber matrix as a flexible sensing framework along with a porous absorption/desorption surface for next-generation wearable gas sensors. [ABSTRACT FROM AUTHOR]