New developments on fibre optic colorimetrie sensors for dissolved CO2 in aquatic environments

摘要

The detection of dissolved carbon dioxide (dCO₂) is made possible through a colorimetric effect that occurs in a sensitive membrane. The reaction with dCO₂ changes the pH of the membrane causing a small difference in its colour which results in a characteristic absorbance spectrum band near 435 nm. A sensing platform based on this effect was developed and tested in gaseous and in aqueous environments. It is a combination of a bundle of large core fibre optics (with diameters above 200 μm) with light emission diodes (LEDs) in the visible range of the spectrum, a silicon photodetector and a polymer membrane sensitive to CO₂. A variation in the absorption of 3 / %VV was obtained in the range from 0 to 1.6 % of gaseous CO₂ with an estimated response time below 60 seconds.