Sensitive colorimetric sensors for visual detection of carbon dioxide and sulfur dioxide

Abstract

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.