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Highly luminescent semiconductor nanocrystals or quantum dots (QDs) possess a number of interesting and
important properties that are tunable thanks to their size-dependent discrete electronic spectra. In this work we studied
the optical properties of a novel type of hybrid structures that combine CdTe QDs with organic dye molecules
(Pseudocyanine iodide) in a J-aggregate state. Due to the excitonic nature of electronic excitations, J-aggregates have the
narrowest absorption and luminescence bands among organic materials, large oscillator strengths and giant third-order
nonlinear susceptibility. In developed structures optical energy harvested by the quantum dots as artificial antennas then
transferred to J-aggregates to enhance the photostability and efficiency of the carriers recombination. To fabricate
CdTe/J-aggregates hybrid nanostructures we have used an approach based on electrostatic interaction between the
positively charged dye and CdTe QDs capped with thioglycolic acid and, thus, carrying a negative charge. In order to
develop an efficient hybrid material operating in the FRET regime, we carefully selected the PL colors (diameters) of the
QD to be optically coupled with absorption of J-aggregates. We took advantage of extremely thin ligand shell (~0.5 nm)
of CdTe QDs, which insures high efficiency of energy transfer. Formed QD/J-aggregate FRET system shows the
broadband absorption in the visible and the ultraviolet part of the spectrum typical of QDs, along with the narrow
emission linewidths characteristic of J-band emitters (~15 nm full width at half-maximum). We use absorption and
photoluminescence spectroscopy and photoluminescence lifetime studies to conclude that efficiency of energy transfer is
95%.
Also we report on development of active whispering-gallery microcavities integrated with with hybrid QDs/J-aggregate
shell. Results of micro-PL spectroscopy and PL lifetime imaging confirm strong quenching of QDs emission
and multifold shortening of their photoluminescence lifetime, which is consistent with highly efficient FRET in hybrid
organic/inorganic semiconductor nanostructures coupled to microcavity modes.
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