Fast energy transfer in layer-by-layer assembled CdTe nanocrystal bilayers

We report on efficient resonant energy transfer in bilayers of water-soluble CdTe quantum dots. The bilayers of CdTe nanocrystals of two different sizes capped by short-chain thiols were formed by layer-by-layer assembly. Temporally and spectrally resolved fluorescence spectroscopy reveals spectral diffusion of the fluorescence signal for quantum dots within one layer as well as rapid (254 ps) energy transfer from layers of small dots to layers of larger dots, which is fast for nanocrystal pairs. Subspecies within the inhomogeneous distribution of donor nanocrystals even show energy transfer rates of $\text{(134\hspace{0.17em}}\mathrm{ps}{)}^{\text{−1}}$ due to a large spectral overlap with acceptor nanocrystals.