Chemiresistive Sensor for Enhanced CO₂ Gas Monitoring

Abstract

Carbon dioxide (CO 2 ) gas sensing and monitoring have gained prominence for applications such as smart food packaging, environmental monitoring of greenhouse gases, and medical diagnostic tests. Although CO 2 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 CO 2 detection to overcome these problems. The sensing material of this sensor consists of a CO 2 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 CO 2 between 10 3 and 10 6 ppm even at high humidity levels (>80% RH), and it is capable of differentiating ammonia at low concentrations (0.1−5 ppm) from CO 2 . 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.

Developing a Chemiresistive Gas Sensor Array for Simultaneous Detection of Ammonia and Carbon Dioxide Gases

“…Since DEA has a higher p K a (10.64), in the presence of both ions, DEA would protonate the ammonium ions. As the concentration of ammonia increases, the number of DEA ions that can protonate the NH 4 + ions decreases, which leads to a decline in the electrical resistance . This mechanism was validated by measuring the pH and resistance of DEA solution in the presence of ammonium ions (Figure S4F).…”

“…At room temperature, the DEA molecules protonate the NH 4 + ions generated; however, the solubility of NH 3 increases with a decrease in temperature. Therefore, the DEA molecules cannot protonate the additional NH 4 + ions fast enough and we observed a drop in sensor resistance for concentrations above 1 ppm as shown in Figure A …”