Dependence of Short-Range Energy Transfer Behavior on the Average Distance between Colloidal Quantum Dots in Solutions: Implications for Resonance Energy Transfer

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High Resolution Image Download MS PowerPoint Slide For the applications of color conversion and the characterization of colloidal quantum dots (QDs), we use three series of solution samples of surface-charged QDs for studying the dependence of resonance energy transfer (RET) behavior on QD concentration or average QD distance. The mixture samples of green-emitting QD, i.e., donor, and red-emitting QD, i.e., acceptor, and the reference samples of single-type QD are prepared for investigating the RET behavior. The variations of RET efficiency, RET rate, and red-overgreen intensity ratio with average QD distance under the three conditions of different relative surface charges and different relative concentrations are compared. A theoretical model for the dependence of normalized RET rate on average QD distance is derived to show the reduced inverse-proportion power index in such a multiple-acceptor RET system. However, this model is applicable only when the average QD distance is larger than ∼50 nm under the condition of the same surface charge on the donor and acceptor. When the average QD distance is smaller than ∼50 nm, the effects of excitation shielding, electrostatic force, and multiple-donor/multiple-acceptor interaction further reduce the inverse-proportion power index. Under the condition of the opposite surface charges, a small inverse-proportion power index can always be observed irrespective of the average QD distance, which is attributed to the attraction between the donor and acceptor, i.e., a QD distribution with small distances between a donor and a few acceptors even though individual donors are far apart.

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