A Flexible and Polymer-Based Chemiresistive CO2 Gas Sensor at Room Temperature

CO₂ 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 CO₂ 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 CO₂ 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 CO₂ 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 CO₂ 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 CO₂, indicating the protonation of the polymer’s amine sites, facilitating the detection of CO₂ in the wet environment. This sensor is efficient for detecting CO₂ concentration released during fermentation of kimchi as a food model.