Colorimetric Dye-Loaded, Adhesive, and Stretchable Hydrogel Sensor: A Sensitive and Visible H2S Gas Sensing Platform

Abstract

Hydrogen sulfide (H₂S), as a toxic gas, is one of the occupational hazards to workers' health. Traditional H₂S sensors often suffer from external circuits, measurement systems, liquid-phase reactions, or high detection limits. Herein, a colorimetric sensor for H₂S detection was developed by incorporating colorimetric dye [lead acetate, Pb(OAc)₂] into polyacrylamide (PAM)/polyvinyl alcohol (PVA) hydrogel. Benefitting from the interpenetrating polymer network, non-covalent interactions such as hydrogen bonds and dense internal structure, the hydrogel exhibited excellent adhesion to different substances (adhesion strength up to 14.11 kPa) and mechanical properties (tensile strength up to 116.92 kPa, elongation rate up to 576%). Furthermore, due to the liquid-phase reaction system and excellent [Pb(OAc)₂] loading capacity provided by the hydrogel, the prepared sensors exhibited excellent sensing performance response time, sensitivity, and simplicity. The theoretical detection limit of the sensor was 0.69 ppm, and the minimum exposure time required for detection was 14 s. The colorimetric effect of the hydrogels was positively correlated with the addition of Pb(OAc)₂ and the extension of time. The results showed that the color change of PAM/PVA/Pb(OAc)₂ hydrogel can be visible to the naked eye even if the concentration of H₂S is only 1 ppm. It is expected that this hands-free, arbitrarily adhesive, stretchable hydrogel colorimetric sensor strategy for visual detection of H₂S will extend toxic gas alarm systems to a new level.