Optochemical HCl gas sensor using substituted tetraphenylporphine–ethylcellulose composite films

Abstract

Composite films of various tetraphenylporphines embedded in ethylcellulose were prepared and their optical response to gaseous HCl was investigated. The absorbance of the Soret and Q-bands for free-base tetraphenylporphines is reversibly sensitive to ppm levels of HCl. The replacement of thepara hydrogen in one phenyl group with a hydroxy group is effective in enhancing the sensitivity of the Q-band region while prolonging response time. In addition, the temperature coefficient of the sensitivity of TP(OH)(R)₃PH₂ is lower than that of TPPH₂ . Under filtered light (>600 nm) a significant deterioration of the sensitivity was not observed for more than 50 d.