ChemAtom Seminar: Excited State Relaxation Dynamics of Fluorescent Molecules in Nano-sized Micellar Systems​

Excited state dynamics of fluorescent probe molecules in homogeneous environments have been studied in the past in order to understand various excited state relaxation processes.As photoexcitation of a molecule generally induces changes in its electronic and geometrical structures, which in turn lead to the changes in photophysical and photochemical processes, which include electronic charge redistribution, electron and proton transfer, large amplitude intramolecular torsional motions, trans-cis isomerization, intramolecular vibrational redistribution, intermolecular vibrational relaxation (vibrational cooling), internal conversion, solvation etc.

Thus, the dynamics and mechanism of the reactions in organized media are expected to differ largely as compared to those in homogeneous solutions. Also, the reactions in organized media are of direct relevance to biology, medicinal chemistry, host-guest chemistry, catalysis, molecular electronics and many others. The wide range of functions performed by the biological membranes and membrane proteins have motivated researchers to look for simple model systems that mimic the biological systems. Organized media such as micelles, micro emulsions, vesicles so forth can mimic reactions in bio-systems and also have the potential for energy storage. A typical example of such membrane mimetic models is a micelle. The water near the micellar interface possesses certain characteristics of water at the biological membranes. These micellar solutions are excellent model systems for the use in studying biologically relevant processes and have been utilized to investigate processes in restricted environments.

Fluorescent probe methods have been utilized to investigate such processes. As surfactant micelles and polymers influence the physical-chemical properties of many dyes. Studies of such systems are important for the understanding of the photophysical photochemical activities of the dyes in organized assemblies, in particular, the photophysical behavior of fluorescent dye molecules in the presence of surfactants-micelles-reverse micelles and nanoparticles has been a subject of intense investigations because the dynamical characteristics of confined molecules differ considerably from its bulk molecules.