Efficient emission from core/(doped) shell nanoparticles: applications for chemical sensing.

We have studied manganese doping of zinc selenide core/zinc sulfide shell nanocrystals (NCs) where the impurity phosphor resides primarily in the shell. We have found that a simple two-step synthesis can be used to create these nontoxic materials that display efficient energy transfer from the core to the Mn doped shell. These core/shell NCs retain ample quantum efficiency ( approximately 25%) when solubilized in water, which opens the possibility of using these materials as bioimaging agents. As recent work has shown that nanocrystals can be functionalized with organic dyes to operate as ratiometric chemical sensing agents, we have conjugated the doped NCs with an organic dye to showcase efficient Förster resonant energy transfer from the shell-doped phosphor to the surface-bound dye. This result indicates that doped NCs can be used to develop nontoxic ratiometric sensing/biological imaging agents.