The effects of confinement of the ionic liquid 1-butyl-3-methylimidazolium tetrafluoroborate on solvation dynamics and rotational relaxation of Coumarin 153 (C-153) in Triton X-100/cyclohexane microemulsions have been explored using steady-state and picosecond time-resolved emission spectroscopy. The steady-state and rotational relaxation data indicate that C-153 molecules are incorporated in the core of the microemulsions. The average rotational relaxation time increases with increase in w ([bmim][BF(4)]/[TX-100]) values. The solvent relaxation in the core of the microemulsion occurs on two different time scales and is almost insensitive to the increase in w values. The solvent relaxation is retarded in the pool of the microemulsions compared to the neat solvent. Though, the retardation is very small compared to several-fold retardation of the solvation time of the conventional solvent inside the pool of the microemulsions.

We have reported the retardation of solvation dynamics of Coumarin 480 (C-480) in the Stern layer of the cetyltrimethylammonium bromide (CTAB)−sodium deoxycholate (NaDC) and Tween 80−NaDC mixed micelles compared to pure water using picosecond time-resolved emission spectroscopy. The slow solvation dynamics in the Stern layer of the mixed micelles is due to the water molecules confined in the Stern layer, counterions, and interactions of the counterions with the headgroups of the surfactant. The rotational relaxation time of C-480 in these mixed micelles is also investigated. The rotational relaxation times are retarded in the Stern layer of the mixed micelles.