Enabling Förster Resonance Energy Transfer from Large Nanocrystals through Energy Migration

Abstract

The stringent distance dependence of Förster resonance energy transfer (FRET) has limited the ability of an energy donor to donate excitation energy to an acceptor over a Förster critical distance (R) of 2-6 nm. This poses a fundamental size constraint (<8 nm or ∼4R) 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 ∼15R) 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.

Energy Transfer in Dye‐Coupled Lanthanide‐Doped Nanoparticles: From Design to Application

“…revealed that, in homogenously doped LnNPs, only the near‐surface emitters contributed to FRET, whereas a major part of the near‐center lanthanide ions only transferred energy to acceptors through reabsorption processes . Consequently, this effect imposes a size constraint for the LnNPs because larger NPs increase the number of near‐center lanthanides beyond R 0 required for efficient nonradiative energy transfer (Figure b) . Additionally, energy transfer has to compete with other deactivation pathways, including radiative decay from the emission of the emitter and nonradiative deactivation through vibrational excitation of the host crystal lattice or surface defects/quenching sites.…”

“…We demonstrated that the gadolinium sublattice could assist an energy‐migration process to bridge energy transfer through the central particle–surface interface. This design allows us to realize more efficient FRET from a larger (≈30 nm) core–shell upconversion NP to FITC and many other dye molecules …”

“…[9] Consequently,t his effect imposes as ize constraint for the LnNPs because larger NPs increase the number of near-center lanthanides beyond R 0 required for efficient nonradiative energy transfer ( Figure 2b). [10] Additionally,e nergy transfer has to competew ith other deactivation pathways, including radiative decay from the emission of the emitter and nonradiative deactivation throughv ibrationale xcitation of the host crystal lattice or surface defects/quenching sites. All of these factors are challenging the structurald esigno fl anthanide NP-based energy-transfer systems.…”

“…This design allows us to realize more efficient FRET from al arger ( % 30 nm) core-shell upconversion NP to FITC and many other dye molecules. [10]…”

Photon Upconversion Kinetic Nanosystems and Their Optical Response

“…The case of high sensitizer concentration, when the migration rate is faster than the spontaneous sensitizer decay or the sensitizer‐activator energy transfer, is called the fast migration case. Excitation energy could migrate over a relatively long range, covering the nanoparticle as a whole. As energy migration plays a very important role in upconversion luminescence, there have been many attempts to manipulate it in order to control the upconversion luminescence .…”