Journal
ACS NANO
Volume 12, Issue 6, Pages 5657-5665Publisher
AMER CHEMICAL SOC
DOI: 10.1021/acsnano.8b01451
Keywords
energy transfer; nanocrystals; FRET; cross-talk; bleed through
Categories
Funding
- National Science Foundation [CHE-1465052, CHE-1508501]
- Welch Foundation [U-0047]
- Asahi-Kasei Corp
- Division Of Chemistry [1465052, 1508501] Funding Source: National Science Foundation
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Sensing strategies utilizing Forster resonance energy transfer (FRET) are widely used for probing biological phenomena. FRET sensitivity to the donor acceptor distance makes it ideal for measuring the concentration of a known analyte or determining the spatial separation between fluorescent labels in a macro molecular assembly. The difficulty lies in extracting the FRET efficiency from the acceptor-induced quenching of the donor emission, which may contain a significant non FRET contribution. Here, we demonstrate a general spectroscopic approach for differentiating between charge transfer and energy transfer (ET) processes in donor-acceptor assemblies and apply the developed method for unravelling the FRET/non-FRET contributions in cyanine dye-semiconductor quantum dot (QD) constructs. The present method relies on correlating the amplitude of the acceptor emission to specific 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. We observe that the latter accounts for 50-99% of donor emission quenching in QD-Cy5 and QD-Cy7 systems, stressing the importance of determining the non-FRET efficiency in a spectroscopic ruler and other FRET-based sensing applications.
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