Equilibrium studies on a fluorescence plastic thin film sensor for carbon dioxide

The method of preparation of a novel plastic thin film sensor which incorporates the fluorescent dye, 8-hydroxy, 1,3,6 pyrene trisulfonic acid is described; the shelf-life of the film is over 6 months. The results of a study of the equilibrium response of the sensor towards different levels of gaseous CO2 fit a model in which there is a 1:1 equilibrium reaction between the deprotonated form of the dye (present in the film as an ion pair) and the level of CO2 the film is exposed to. The 0 - 90% response time of the film when exposed to an alternating atmosphere of air and 5% CO2 is typically less than 3 s. The response of the film towards a random variation in %CO2 as a function of time compares favorably with that observed at the same time using an infra-red detector.