Abstract
The spectral changes of tetraphenylporphyrin (TPPH 2)–polymer composites in the visible region were examined in order to detect HCl gas. For TPPH 2, the absorbance of the Soret and Q bands were sensitive to ppm levels of HCl. The sensing mechanism were characterized basing the protonation reaction and sorption isotherm: TPPH 2+2HCl film⇄TPPH 4 2+·2Cl − and [HCl film]= a[HCl gas] n . The equilibrium constant of the former was decreased with increase in the working temperature and in glass transition temperature ( T g) of polymer matrix. The number of active sites ( a) for HCl sorption decreased with a decrease in the T g. The response behavior was improved by using polymer with lower T g.
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