Yefimova S. Spectroscopy of electronic excitations in molecular nanoclusters characterized by different structural perfection.

Research subject: exciton transport in J-aggregates, exciton-phonon interaction, mechanisms of luminophore interaction in nanoscale volume. Research aim: solving research problem concerning mechanisms of luminescence and factors affecting luminescence properties of nano-scale molecular clusters characterized by different structural perfection and type of electronic excitations (J-aggregates of polymethine dyes and surfactant micelles containing luminophores). Results and novelty: For the first time, the strong exciton localization in J-aggregates with controlled static disorder has been found. J-aggregates are found to be characterized by strong exciton-phonon interaction that is the reason of self-trapped state formation. For the first time, the constants of exciton-phonon interaction have been calculated for several J-aggregates. It has been shown that the value of exciton-phonon interaction increases for strongly localized states. It has been shown for the first time that self-trapped state formation and non-radiative relaxation are responsible for small quantum yield of J-aggregates. It has been demonstrated that local increasing luminophor concentration as a result of their solubilization in nanoscale volume allows the effective multi-cascade fluorescence resonance energy transfer to be realized at luminophor initial small concentrations in a solution ( 10-5 M). Complex interaction between organic molecules in a nonovolume of surfactant micelles has been revealed. The possibility to control solubilization and aggregation of molecules in nanovolume, and consequently luminescent properties of nanoclusters is demonstrated. The fields of implementation are excitonic physics, purposeful development of nanoclusters with controlled optical properties.