Fig. 2. Chemical structures of the investigated photosensitizers: methylene blue (top left), eosin y (top right), sodium meso-tetraphenylporphine-4,4′,4′′,4′′′-tetrasulfonat (bottom left) and 5,10,15,20-tetrakis(1-methyl-4-pyridinio)porphyrin tetra(p-toluene-sulfonate) (bottom right).