Optochemical HCl gas detection using alkoxy substituted tetraphenylporphyrin-polymer composite films: Effects of alkoxy chain length on sensing characteristics

Composite films of 5,10,15,20-tetra(4′-alkoxyphenyl)porphyrin (TP(OR)PH2) embedded in various polymer matrices were prepared and their optical responses to HCI gas were examined. The absorbance of the Soret and Q-bands for free-base TP(OR)PH2 is reversibly sensitive to sub-ppm levels of HCl. The glass transition temperature (Tg) of a matrix below the sensing temperature is more effective to the response and recovery behavior than above the sensing temperature. High sensitivity to sub-ppm levels of HCl was achieved by using a TP(OC4H9)PH2-BuMA composite film.