The diffusion of carbon monoxide into thin, transparent, porous film media is studied by doping the film with an iron porphyrin and spectroscopically monitoring the chemical interaction between the reduced iron porphyrin and the diffusing solute. The films are spin-cast from metal alkoxide carboxylates. Both optical absorption and resonance Raman spectroscopies have been used to study the porphyrin-doped film and the diffusion process.
The studies yield information on the effective pore size and homogeneity of the materials, and show that redox chemistry can be performed on incorporated metallo-porphyrins. This investigation also demonstrates the usefulness of porphyrin-doped films as chemical sensors, showing a sensitivity below 70 ppb to aqueous carbon monoxide.