Porphyrins as probe molecules in the detection of gaseous pollutants I: Diffusion of pyridine in polystyrene films containing zinc-tetraphenylporphyrin

Abstract

Zinc-porphyrins can be coordinated by amines, resulting in a red shift in the absorption spectrum. We have taken advantage of this property to study the diffusion of gaseous pyridine in polystyrene films. We have studied the absorption properties of polystyrene films of different thicknesses and calculated the extinction coefficients of Zn-porphyrin in these films. It has been demonstrated that there is no aggregation of porphyrins in the film at the concentrations used in this study. We have demonstrated that diffusion of pyridine is dependent on the concentration of porphyrins in the film but independent of the film thickness. A fast response (≈ 2 min) and a detection limit of 10 μmol m −3 of pyridine in atmosphere are obtained. The film can be regenerated by heating at 383 K under vacuum (1 mmHg). Since the films are found to be sensitive to other amines, a possible application is the realization of cheap dosimeters for amines.