Optochemical HCl gas detection using mono-substituted tetraphenylporphin-polymer composite films

Hydroxy-/alkoxy-substituted tetraphenylporphin were synthesized and their Soret- and Q-bands’ changes with HCl gas in ppm levels were examined. Both the bands were influenced by HCl gas concentration and their changes in sub-ppm levels of HCl were decreased with an increase in the alkoxy chain length. The changes of the absorbance of the Soret- and Q(0–0)-bands were enhanced by replacing ethylcellulose with poly-hexylmethacrylate as a matrix while the recovery times prolonged. The introductions of electron donating substituents to p-phenyl positions of the porphin ring result in the basicity of pyrrole nitrogens.