Tuning free base tetraphenylporphyrins as optical sensing elements for volatile organic analytes

Changes in the visible absorption spectra of ten free base porphyrin compounds in solution and thin film form upon exposure to a range of volatile organic compounds have been investigated. The functional groups attached to the phenyl rings varied in their electron donating/withdrawing strength. These porphyrins were studied with a view to determining their suitability for use in the fabrication of an optical based gas sensor. It has been found that the sensitivity of these sensor materials depends upon the electron donating/withdrawing strength of the functional groups attached to the phenyl rings.