Energy transfer between quantum dots and conjugated dye molecules

Energy transfer from quantum dots (QDs) to variable-length, dye-labeled peptides is reported. We find that existing models used to calculate the efficiency of energy transfer from steady-state measurements are insufficient for nanoparticle-dye interactions. To accurately measure the distance dependence as a function of separation, the effects of both multiple valencies and variations in the luminescence quantum yield of the acceptor dye with separation need to be taken into consideration. Using Poisson statistics, we account for the distribution of QD/dye ratios. Nevertheless, we find that the actual dependence of the energy-transfer efficiency as a function of QD-dye separation obeys an R^-n dependence with n = 6.1 ± 0.1 as predicted by Förster resonance energy transfer (FRET) theory.