Development of an eco-friendly optical sensor element based on tetraphenylporphyrin derivatives dispersed in biodegradable polymer: Effects of substituents of tetraphenylporphyrins on HCl detection and biodegradation

Composite films of 5,10,15,20-tetraphenylporphyrin (TPPH2) derivatives containing electron-releasing groups such as alkyl and alkoxy group embedded in various biodegradable polyesters (BDPE) matrices were prepared and their optical response to hydrogen chloride (HCl) gas were examined in comparison with nonbiodegradable polymers (NBDP) matrices. Absorbance of the Soret- and Q-bands for TPPH2 derivatives-BDPE composite films are reversibly, more sensitive to sub-ppm levels of HCl gas than those for those-NBDP composite films. A high sensitivity to sub-ppm levels of HCl gas was achieved by using a 5,10,15,20-tetra(4′-butoxyphenyl)-porphyrin (TP(OC4H9)PH2)-poly(ɛ-caprolactone) (PCL) composite film.