Aggregation enhanced excimer emission (AEEE) of benzo[ghi]perylene and coronene: multimode probes for facile monitoring and direct visualization of micelle transition.

We report benzo[ghi]perylene (BzP) and coronene (Cron) as multimode fluorescent probes for accurate monitoring and direct visualization of monomer-micelle transitions in surfactants for the first time. The probe molecules formed self-assembled nanoparticles in an aqueous solution and displayed strong aggregation-enhanced excimer emission (AEEE). During the process of surfactant monomer-micelle transition, the probe nanoparticles dissolved, and the observation of excimer-monomer emission transition clearly indicated the formation of micelles. The ratiometric changes in excimer-monomer emission (IE/IM) were used for the precise determination of critical micelle concentration (CMC) of various surfactants. The monomer-micelle transition process was directly observed under a UV lamp, and the visual determination of CMC became possible. The CMC value determination using the excimer/monomer ratio (IE/IM), UV-vis, lifetime and visual assessment clearly suggests that BzP and Cron are excellent multimode probes for monitoring the micelle structural transitions of amphiphiles.