Fine‐Tunable CO2 Colorimetric Sensors and CO2 Level Indicator Meter with Horizontal Linear Gauge via Inter‐Chain Spacers

Fine‐tuning the sensing properties of carbon dioxide (CO2) colorimetric sensors is a challenging task. In this study, a short synthetic route is developed for CO2‐responsive nanoparticles with diverse sensitivity and detection range across a wide range of CO2 concentrations. This involves the addition of oily liquids as inter‐chain spacers, which changes the diffusivity of CO2 gas into the sensing matrices without other chemical modifications. R values and the limit of detection (LOD) are estimated from Euclidean distance (ED) curves, indicating a ten‐fold difference in sensitivity. Optical and physical analyses revealed that these results arise from intercalating inter‐chain spacers between polymeric chains and modifying the gas diffusivity. Furthermore, the sensitivity and detection range can be easily tuned by mixing two CO2‐responsive nanoparticles having different inter‐chain spacers, allowing the fabrication of the sensors with subtle differences in sensitivity and detection range. Based on these results, a CO2 level meter with a horizontal linear gauge that allows visible identification of the level of CO2 over the entire range of CO2 concentrations (from 0% to 100%) is developed. Consequently, the findings will be helpful in achieving a better understanding of gas information and finding an effective way to control the characteristics of colorimetric sensors. A simple methodology is suggested to synthesize CO2 colorimetric sensors (i.e., CO2‐responsive nanoparticles) with varying sensitivity and detection ranges. This is accomplished by incorporating inter‐chain spacers into the sensing matrices. Further, gradual changes can be achieved in sensitivity and detection range by mixing with CO2‐responsive nanoparticles and different inter‐chain spacers and extending it to develop a CO2 level indicator meter.