Molecular combination between alkanolamines and galvinol for ratiometric colorimetric sensing of CO2 gas†

In this study, the application of alkanolamines as an optical CO₂-responsive medium in combination with galvinol (GALH) as a reversible quantitative colorimetric sensor is proposed. Monoethanolamine (MEA) and diethanolamine (DEA), as the simplest primary (1°) and secondary (2°) alkanolamines, were explored for the colorimetric CO₂ response attributed to their well-known CO₂ absorption ability on an industrial scale from more than six decades. Further, the anionic form of GALH (GAL⁻) generates an intense purple color that allows its application for colorimetric measurement which has been very less explored for optical sensing purposes. A reversible, convenient, and simplified colorimetric detection of CO₂ gas was performed using GALH in combination with MEA and DEA in CH₃CN solvent, which showed limits of detection (LODs) for CO₂ gas as low as ∼19 and ∼31 ppm respectively with recyclabilities. The main feature of the developed CO₂ sensor is its non-aqueous medium application, which makes it ideal for producing error-free results under different humidity conditions.