| In this work we studied the optical properties of a novel type of hybrid structures that combine CdTe quantum dots (QDs) with organic dye molecules (Pseudocyanine iodide (PIC)) 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. It was found that aggregation of PIC molecules can be efficiently triggered by fast injection of solution of CdTe QDs into concentrated dye solution resulting in formation of hybrid nano-structures. 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 QDs (donors of energy) to be optically coupled with absorption of J-aggregates. Formed QDs/J-aggregate FRET system shows the broadband absorption in the visible and the ultraviolet part of the spectrum typical of quantum dots, 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%. |
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