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Authors: Andries Meijerink, Yiming Zhao, Celso de Mello Donegá, Joren Eilers, Cees van Walree, Tim van Puffelen, Tim Senden and Freddy Rabouw The incorporation of optically active dopants into quantum dots has been actively investigated, especially since the report by Bhargava et al. on a spectacular shortening of the life time of the spinforbidden Mn2+ emission in ZnS quantum dots. Even though it turned out that later that there is no shortening of life time, research on doped nanocrystals continued grow. Luminescent transition metal ions and lanthanide ions in quantum dots give further control over the optical and magnetic properties. Incorporation is however not trivial. In this presentation an introduction to research on doping quantum dots will be given and the physical properties will be discussed, including research on the variation of the life time for Mn2+ doped into ZnS and CdSe QDs. The second part of the presentation will discuss recent work on new doping strategies. Both cation exchange and single precursor decomposition methods have been successful in achieving doped quantum dots which were not realized by cionventional methods. Examples include ZnTe:Mn2+ magic size nanoclusters and CaS and SrS nanocrystals. ZnTe:Mn clusters were doped via cation exchange. Through single source precursor synthesis methods monodisperse ~8 nm CaS and SrS nanocrystals were achieved which were successfully doped with a variety of magnetic and luminescent ions, including Eu2+ and Ce3+. The optical properties of these doped nanocrystals will be discussed. Finally, it will be shown that in addition to being interesting for optical applications, doped nanocrystals can also be used as probes for testing the validity of theoretical models for local field effects on the radiative decay rate of two level systems. |
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