Optimizing the performance of optical carbon dioxide gas sensors

Abstract

The basic theory behind conventional colorimetric and fluorimetric optical sensors for CO 2 is examined with respect to the effect on sensor response of the key parameters of initial base concentration and dye acid dissociation constant, K D . Experimental results obtained in aqueous solution using a variety of different dyes and initial base concentrations are reported and found to be consistent with the predictions made by the theoretical model. A series of model-generated pK D versus %CO 2 curves for different initial base concentrations allow those interested in constructing an optical CO 2 sensor to readily identify the optimum dye/initial base combination for their sensor; the response of the sensor can be subsequently fine-tuned through minor adjustment of the initial base concentration. The model appears also to apply to the new generation of plastic film CO 2 sensor which have just been developed.