Sensing strategies utilizing Forster resonance energy transfer (FRET) are widely used for probing biological phenomena. The sensing mechanism is usually enabled by correlating such FRET efficiency changes with the donor-acceptor distance within the Forster dipole-dipole approximation, which could be employed either to measure the concentration of a particular analyte that docks at a known distance to a host or to determine the spatial separation between fluorescent labels in targeted macromolecules. But the problem is the measured total efficiency of the donor PL quenching, in general, may include contributions from non-FRET processes. Here, we report on a general spectroscopic strategy for distinguishing between charge and energy transfer processes in donor-acceptor systems and apply the developed method for measuring the corresponding FRET and non-FRET efficiencies in cyanine dye−semiconductor quantum dot (QD) assemblies. The present method relies on correlating the amplitude of the acceptor emission to changes in the donor excitation profile in order to extract ET-only transfer efficiencies. Quenching of the donor emission is then utilized to determine the non-ET component, tentatively attributed to the charge transfer.

Charge and energy transfer in donor-acceptor fluorescence pairs

2019 Spring National Meeting

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