Journal of the American Chemical Society, Vol.138, No.49, 15972-15979, 2016
Enabling Forster Resonance Energy Transfer from Large Nanocrystals through Energy Migration
The stringent distance dependence of Forster resonance energy transfer (FRET) has limited the ability of an energy donor to donate excitation energy to an acceptor over a Forster critical distance (R-0) of 2-6 nm. This poses a fundamental size constraint (<8 nm or similar to 4R(0)) for experimentation requiring particle-based energy donors. Here, we describe a spatial distribution function model and theoretically validate that the particle size constraint can be mitigated through coupling FRET with a resonant energy migration process. By combining excitation energy migration and surface trapping, we demonstrate experimentally an over 600-fold enhancement over acceptor emission for large nanocrystals (30 nm or similar to 15R(0)) with surface-anchored molecular acceptors. Our work shows that the migration-coupled approach can dramatically improve sensitivity in FRET-limited measurement, with potential applications ranging from facile photochemical synthesis to biological sensing and imaging at the single-molecule level.