Chemiresistive Sensor for Enhanced CO₂ Gas Monitoring

Carbon dioxide (CO₂) gas sensing and monitoring have gained prominence for applications such as smart food packaging, environmental monitoring of greenhouse gases, and medical diagnostic tests. Although CO₂ sensors based on metal oxide semiconductors are readily available, they often suffer from limitations such as high operating temperatures (>250 °C), limited response at elevated humidity levels (>60% RH), bulkiness, and limited selectivity. In this study, we designed a chemiresistive sensor for CO₂ detection to overcome these problems. The sensing material of this sensor consists of a CO₂ switchable polymer based on N-3-(dimethylamino)propyl methacrylamide (DMAPMAm) and methoxyethyl methacrylate (MEMA) [P(D-co-M)], and diethylamine. The designed sensor has a detection range for CO₂ between 10³ and 10⁶ ppm even at high humidity levels (>80% RH), and it is capable of differentiating ammonia at low concentrations (0.1–5 ppm) from CO₂. The addition of diethylamine improved sensor performance such as selectivity, response/recovery time, and long-term stability. These data demonstrate the potential of using this sensor for the detection of food spoilage.