Optical CO(2) sensor of the combination of colorimetric change of alpha-naphtholphthalein in poly(isobutyl methacrylate) and fluorescent porphyrin in polystyrene.

An optical CO(2) sensor based on the overlay of the CO(2) induced absorbance change of pH indicator dye alpha-naphtholphthalein in poly(isobutyl methacrylate) (polyIBM) layer with the fluorescence of tetraphenylporphyrin (TPP) in polystyrene layer is developed. The observed luminescence intensity from TPP at 655nm increased with increasing the CO(2) concentration. The ratio I(100)/I(0) value of the sensing film consisting of alpha-naphtholphthalein in polyIBM and TPP in polystyrene layer, where I(0) and I(100) represent the detected luminescence intensities from a layer exposed to argon and CO(2) saturated conditions, respectively, that the sensitivity of the sensor, is estimated to be 192. The response and recovery times of the sensing film are less than 6.0s for switching from argon to CO(2), and for switching from CO(2) to argon. The signal changes are fully reversible and no hysterisis is observed during the measurements. The highly sensitive optical CO(2) sensor based on fluorescence intensity changes of TPP due to the absorption change of alpha-naphtholphthalein in polyIBM layer with CO(2) is achieved.