A Flexible and Polymer‐Based Chemiresistive CO ₂ Gas Sensor at Room Temperature

Abstract CO 2 sensing is important in many applications ranging from air‐quality monitoring to food packaging. In this study, an amine‐functionalized copolymer, poly( N ‐[3‐(dimethylamino)propyl]‐methacrylamide‐ co ‐2‐ N ‐morpholinoethyl methacrylate) (p(D‐ co ‐M)) is synthesized, offering moderate basicity suitable for a wide CO 2 detection range. Taking advantage of this characteristic of p(D‐ co ‐M), this polymer is used for designing a chemiresistive, low‐cost, flexible, and reversible CO 2 sensor. The p(D‐ co ‐M)‐based sensors show a noticeable decrease in their direct current resistance and alternating current impedance upon exposure to a wide range of CO 2 concentration (1–100%) at room temperature with a response and a recovery time of 6 and 14 min, respectively. Additionally, the p(D‐ co ‐M)‐based sensors demonstrate a favorable selectivity to CO 2 in the presence of interfering gases including methanol, ethanol, toluene, and acetone. Surface potential measurements show an increase of +6.34 V upon exposure to humidity and CO 2 , indicating the protonation of the polymer's amine sites, facilitating the detection of CO 2 in the wet environment. This sensor is efficient for detecting CO 2 concentration released during fermentation of kimchi as a food model.