Luminescence and resonant energy transfer of two sizes of CdTe quantum dots embedded in gelatin films

We have used two sizes of highly monodisperse colloidal CdTe nanocrystals (or quantum dots) and gelatin to form quantum dots (QDs)-gelatin films. Photoluminescence (PL) results for the mixed systems show that the quenching of the emission of the small dots was accompanied by the enhancement of the emission of the large dots as their average separation decrease. The phenomena were attributed to the occurrence of the long-range resonance transfer (LRRT) between two different sizes of QDs when the concentration of the gelatin is low enough to ensure the close proximity of the dots. Determined by the overlap between the emission spectrum of the donor QDs (small dots) and the absorption spectrum of the acceptor QDs (large dots), FRET provides efficient coupling between two different sizes of QDs via long-range dipoledipole interaction. The PL spectrum changes were also confirmed by true-color images of the mixed QDs system, which show that the colors change gradually from red to green at the gelatin concentrations varying from 0.01% to 0.25 wt% in their initial solution. The experimental results are expected to open new opportunities to modulate the luminescence of semiconductor QDs in a simple way.