Sensitive colorimetric sensors for visual detection of carbon dioxide and sulfur dioxide†
A series of highly efficient, solid-state sensors for direct colorimetric detection of gaseous CO2 and SO2 is described. The basic components of the sensors are a CO2 and SO2-responsive, tertiary amino alcohol, such as triethanolamine, and a pH-indicator dye, e.g. cresol red, immobilized on a porous γ-aluminum oxide support. These sensors show distinct visual responses to low levels of CO2 and SO2 present in air. A structure–performance relationship was also established for these sensors. To increase the shelf-life, tertiary amino alcohols were covalently attached to the porous alumina support. These porous alumina-supported tertiary amino alcohols also offer potential for use as adsorbents for acidic gases such as CO2 and SO2 with the ability to selectively release these under different conditions, allowing easy separation from a gas stream.