Excitation dynamics in polymer-coated semiconductor quantum dots with integrated dye molecules: The role of reabsorption

Inorganic CdSe/ZnS core-shell quantum dots have been coated with amphiphilic polymers in order to enable their transfer to aqueous solutions. Additionally, ATTO-dye molecules have been embedded in the polymer shell. In this geometry ATTO dye acts as acceptor of the quantum dot donors' excitation. The energy transfer dynamics has been investigated in detail within the system by steady state and time-resolved optical spectroscopy. Radiative and nonradiative transfer processes dominate the photoluminescence properties of the quantum dots and dye molecules. Choosing different sizes of the quantum dots allowed for tuning the spectral overlap between the semiconductor dot emission and dye absorption. The experimental results have been. described within a kinetic model which enables precisely to reveal the respective contributions of reabsorption and radiationless transfer rates. The, distance dependence of quantum efficiencies and transfer rates shows that radiationless transfer is the more dominating the smaller the distance between the core of the nanoparticles and the dye molecules. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3253762]