Stretchable, Stable, and Room-Temperature Gas Sensors Based on Self-Healing and Transparent Organohydrogels

Abstract

Conductive hydrogels have emerged as promising candidate materials for fabricating wearable electronics because of their fascinating stimuli-responsive and mechanical properties. However, the inherent instability of hydrogels seriously limits their application scope. Herein, the stable, ultrastretchable (upon to 1330% strain), self-healing, and transparent organohydrogel was exploited as a novel gas-responsive material to fabricate NH 3 and NO 2 gas sensors for the first time with extraordinary performance. A facile solvent substitution method was employed to convert the unstable hydrogel into the organohydrogel with a remarkable moisture retention (avoid drying within a year), frost resistance (freezing point below −130 °C), and unimpaired mechanical and gas sensing properties. First-principles simulations were performed to uncover the mechanisms of antidrying and antifreezing effects of organohydrogels and the interactions between NH 3 /NO 2 and organohydrogels, revealing the vital role of hydrogen bonds in enhancing the stability and the adsorption of NH 3 /NO 2 on the organohydrogel. The organohydrogel gas sensor displayed high sensitivity, ultralow theoretical limit of detection (91.6 and 3.5 ppb for NH 3 and NO 2, respectively), reversibility, and fast recovery at room temperature. It exhibited the capabilities to work at a highly deformed state with nondegraded sensing performance and restore all the electrical, mechanical, and sensing properties after mechanical damage. The gas sensing mechanism was understood by considering the gas adsorption on functional groups, dissolution in the solvent, and the hindering effect on the transport of ions.