. . . . . . . . . .    ANM 2010     3rd International Conference on Advanced Nano Materials     12-15 September 2010 - Agadir, Morocco Back    Abstract ANMM147 STRUCTURE AND RELAXATION DYNAMICS IN NANOCOMPOSITES BASED ON SEMICONDUCTOR CDSE/ZNS QUANTUM DOTS AND FUNCTIONAL ORGANIC LIGANDS  E. Zenkevich (a) , Th. Blaudeck (b), D. Kowerko (c), F. Cichos (d), C. von Borczyskowski (c) (a) National Technical University of Belarus, Minsk 220013, Belarus (b) Institute for Print and Media technology, University of Technology, 09107 Chemnitz, Germany (c) Institute of Physics and Center for Nanostructured Materials and Analytics, 09107 Chemnitz, Germany (d) Molecular Nanophotonics, University of Leipzig, 04103 Leipzig, Germany . In the past decade, emerging hybrid nanocomposites consisting of semiconductor quantum dots (QD) and functional organic molecules (ligands) are considered as promising building blocks for advanced multifunctional nanostructures of considerable scientific and practical interest. Nevertheless, there has been still difficulty in the fundamental understanding of the basic mechanisms on photophysical processes, especially photoluminescence (PL) response, related to the unique interface properties of QD-organic nanocomposites. Recently, we have succeeded in the direct labelling of colloidal semiconductor CdSe/ZnS QDs with pyridyl-substituted porphyrins (H2P) and perylene bisimide dyes (PBI), using the bottom-up, self-assembly approach through non-covalent interactions of QD surface with anchoring substituents of H2P and PBI molecules in non-polar solvents at 77-295 K. In this report, we are focusing on photo-physical mechanisms of exciton relaxation in such complexes. It was found both on an ensemble and single QD level that the efficiency of QD PL quenching drastically depends on the kind of ligating organic molecules and anchoring groups, interface properties (ZnS layer thickness) as well as increases upon QD decrease. The observed PL strong quenching effect is hardly described by neither Forster resonance energy transfer QD ligand no the photoinduced charge separation. Using experimental Stern-Volmer PL quenching plots and quantum mechanical calculations for the electron wave functions in the quantum confinement regime, we have shown that the specificity of the exciton non-radiative decay in QD-porphyrin nanocomposites is due to the manifestation of inductive and mesomeric effects leading to the charge tunnelling through ZnS barrier in quantum confinement conditions followed by a self-localization of the electron or the formation of trap states. In conclusion, we would like to discuss some possible applications of QD-porphyrin nanocomposites in nanobiotechnology and nanobiomedicine (fluorescence sensing, photodynamic therapy etc.). . © nanoAC . . . . . . . . . .

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