Fluorescence behavior of intramolecular charge transfer probe in anionic, cationic, and nonionic micelles

The intramolecular charge transfer (ICT) property of trans-ethyl p  -(dimethylamino) cinnamate is used to probe the anionic, cationic, and nonionic micelles by steady-state and picosecond time-resolved fluorescence spectroscopy. The ICT fluorescence band intensity was found to increase with concomitant blue shift with addition of surfactants. All the experimental results suggest that the probe molecule resides in the micelle–water interface rather than going into the core. However, the penetration is more toward the micellar core in nonionic surfactants when compared with ionic micelles. The decrease in nonradiative decay constants in micellar environments indicate restricted motion of the probe toward the formation of ICT state. Critical micelle concentrations were determined from the sharp change in fluorescence intensity and effective dielectric constants of the micelle–water interface were calculated from the correlation diagram of 0,00,0 transition energy with polarity of the medium.

Graphical abstractThe fluorescence behavior of intramolecular charge transfer state in trans-ethyl p-(dimethylamino) cinnamate (EDAC) was investigated in different micellar environments. The location of the probe in the micelle structure, critical micelle concentration, and effective polarity of the medium were determined from the steady-state and picosecond time-resolved measurements.Figure optionsDownload full-size imageDownload as PowerPoint slide