Investigation of the response of dye-nonaqueous solvent solutions to carbon dioxide

Solutions of dye-nonaqueous solvent containing fluorescein (FL) and potassium hydroxide (KOH) in solvent mixtures of N,N-dimethylformamide (DMF)-water have been investigated for the sensing of gaseous carbon dioxide (CO2). It has been found that increasing water content in a dye-solvent solution enhances its sensitivity to CO2 but that increasing concentration of KOH has the opposite effect. A flow-through system consisted of a solution of 10.6 μM FL and 180 μM KOH in DMF and plastic optical fibres were used to reversibly determine gaseous CO2 with the range of 0 to 10% (v/v) in N2.