Solvation dynamics of 4-aminophthalimide in water-in-oil microemulsion of triton X-100 in mixed solvents

Solvation dynamics of 4-aminophthalimide (4-AP) in water-in-oil microemulsion of Triton X-100 (TX) in mixed solvents containing 30% benzene and 70% n-hexane is studied using picosecond time-resolved Stokes shift. The steady-state emission spectrum of 4-AP in this microemulsion is very different from that in TX reverse micelle or in water. This indicates that in this microemulsion the 4-AP molecule stays in the water pool and the micropolarity of the water pool is very much different from that of ordinary bulk water. In TX microemulsions 4-AP exhibits wavelength-dependent fluorescence decays and a growth in the nanosecond time scale at long wavelengths. The solvation dynamics of 4-AP in TX microemulsion is bimodal with a short component of 0.74 ns and a very long component of 29.73 ns. This is similar to the solvation dynamics of coumarin 480 in the large water pools of sodium dioctyl sulfosuccinate (AOT)/n-heptane/water microemulsions