Molar Fraction Dependence of Excitation Energy Transfer in Mixed Monolayer Assemblies of 11‐(9‐Carbazolyl)undecanoic Acid and Long‐chain Fatty Acids

The efficient energy transfer from 11‐(9‐carbazolyl)undecanoic acid to a very small fraction (470 ppm) of benzocarbazolyl derivatives in mixed monolayer assemblies with long‐chain fatty acids was observed when the molar fraction of chromophore‐containing amphiphiles (fc) was higher than about 0.05. The fluorescence intensity ratio of acceptors and donors increased with the molar fraction. It tended to saturate when fc is larger than about 0.2. Such fraction dependence was not explained by the Förster energy transfer among randomly distributed chromophores, but was analyzed by the exciton migration model. Our results show that aggregation of chromophores in mixed monolayer assemblies does occur depending on the molar fraction fc.