Extracting fluorescence signal due to direct excitation of the energy acceptor from quantum dot-based FRET

An “in situ” strategy for extracting the fluorescence signal of dye acceptors due to direct excitation from Qdot-based FRET systems has been reported. The relevant theory model was developed to describe the present strategy. This strategy involves selective control of the quantum yield of Qdot donors “in situ”, not only providing a straightforward approach to qualitatively confirm the FRET-based fluorescence enhancement but also allowing us to quantitatively separate the fluorescence signal of dye acceptors due to direct excitation and FRET enhancement from each other with high precision and convenient procedures. Different from existing method which was commonly used in literatures, our “in situ” strategy does not involve complicated quantification of the dye acceptors conjugated on the surface of Qdots. Results indicated that the fraction of the emission from the dye acceptors due to FRET process decreases with the increase in the amount of dye acceptors on the Qdot surface. In addition, the relation between the quantum yield of Qdot donors and the FRET enhancement factor of the dye acceptors have also been explored for the first time by the present “in situ” strategy.