Rapid responsible optical CO₂ sensor of the combination of colorimetric change of α-naphtholphthalein in poly(trimethylsiliylpropyne) layer and internal reference fluorescent porphyrin in polystyrene layer

An optical CO₂ sensor based on the overlay of the CO₂ induced absorbance change of pH indicator dye α-naphtholphthalein in poly(trimethylsiliypropyne) (poly(TMSP))layer with the fluorescence of tetraphenylporphyrin (TPP) in polystyrene layer is developed. The observed luminescence intensity from TPP at 655 nm increased with increasing the CO ₂ concentration. The ratio I₁₀₀/I₀ value of the sensing film, where I₀ and I₁₀₀ represent the detected luminescence intensities from a layer exposed to 100% argon and 100% CO ₂, respectively, that the sensitivity of the sensor, is estimated to be 10.3. The response and recovery times of the sensing film are less than 3.0 s for switching from argon to CO₂, and for switching from CO ₂ to argon. The signal changes are fully reversible and no hysteresis is observed during the measurements. The highly sensitive and fast responsible optical CO₂ sensor based on fluorescence intensity changes of TPP due to the absorption change of α-naphtholphthalein with CO₂ is achieved using poly(TMSP) film.