Synthesis of a porous SiO2–H3BO3–V2O5–P2O5 glassy composite: structural and surface morphological behaviour for CO2 gas sensing applications

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.

Sensitivity Enhancement of CO2 Sensors at Room Temperature Based on the CZO Nanorod Architecture

Cobalt-doped ZnO (CZO) thin films were deposited on glass substrates at room temperature by radio frequency (RF) magnetron sputtering of a single target prepared with ZnO and Co3O4 powders. Changes in the crystallinity, morphology, optical properties, and chemical composition of the CZO thin films were investigated at various sputtering powers of 45, 60, and 75 W. All samples presented a hexagonal wurtzite-type structure with a preferential c-axis at the (002) plane, along with a distinct change in the strain values through X-ray diffraction patterns. Scanning electron and atomic force microscopy revealed uniform and dense deposition of nanorod CZO samples with a high surface roughness (RMS). The Hall mobility and carrier concentration increased with the introduction of Co+ ions into the ZnO matrix, as seen from the Hall effect study. The gradual increase of the power applied on the target source significantly affected the morphology of the CZO thin film, which is reflected in the CO2-sensing performance. The best gas response to CO2 was recorded for CZO-60 W with a response of 1.45 for 500 ppm CO2, and the response/recovery times were 72 and 35 s, respectively. The distinguishing feature of the CZO sensor is its ability to effectively and rapidly detect the CO2 target gas at room temperature (∼27 °C, RT).