Microenvironments of 8-anilino-1-naphthalenesulfonate at the heptane-water interface: time-resolved total internal reflection fluorescence spectroscopy

Picosecond time-resolved total internal reflection fluorescence spectroscopy was applied to study the microenvironments of 8-anilino-1-naphthalenesulfonate molecules at the heptane-water interface. By analyzing the fluorescence decay profiles, it was found that the fluorophores in the vicinity of the interface are present in two different solvated structures. One of them is located up to a few nanometers from the interface, and the other is located in a relatively wide range toward the aqueous phase. The former solvated structure is the cause of a long fluorescence lifetime which reflects the low polarity or the extremely high viscosity of the microenvironments.