ENERGY-TRANSFER AND AGGREGATION IN MONOLAYERS CONTAINING PORPHYRINS AND PHTHALOCYANINES

Energy transfer and aggregation of a porphyrin and phthalocyanine with symmetrically substituted aliphatic chains in a phospholipid monolayer at the air-(argon)-water interface are studied by fluorescence microscopy and spectroscopy. Because of the sensitivity of the processes to local concentrations the onset of the lipid phase transition is detected before gel phase domains are microscopically visible. This indicates that domain formation results from aggregation of small particles of condensed lipid. The phthalocyanine, in contrast to the porphyrin, similarly partitions into fluid and solid phases and therefore is rather homogeneously distributed also at high surface pressures. An efficient energy transfer leading to sensitized phthalocyanine fluorescence is detected.