Electrical control of Förster energy transfer

Abstract

Bringing together compounds of intrinsically different functionality, such as inorganic nanostructures and organic molecules, constitutes a particularly powerful route to creating novel functional devices with synergetic properties found in neither of the constituents. We introduce nanophotonic functional elements combining two classes of materials, semiconductor nanocrystals and dyes, whose physical nature arises as a superposition of the properties of the individual components. The strongly absorbing rod-like nanocrystals focus the incident radiation by photopumping the weakly absorbing dye via energy transfer. The CdSe/CdS nanorods exhibit a large quantum-confined Stark effect on the single-particle level, which enables direct control of the spectral resonance between donor and acceptor required for nanoscopic Förster-type energy transfer in single nanorod-dye couples. With this far-field manipulation of a near-field phenomenon, the emission from single dye molecules can be controlled electrically. We propose that this effect could lead to the design of single-molecule optoelectronic switches providing building blocks for more complex nanophotonic circuitry.

Photoluminescence Spectroscopy of Carbon Nanotube Bundles: Evidence for Exciton Energy Transfer

“…We show that their apparently complex spectra can be simply interpreted considering exciton energy transfer between tubes. This is a well known phenomenon in biological systems, conjugated polymers, quantum wires, dots, and other lowdimensional systems [11,12,13,14,15], which we now clearly identify in nanotubes. We find that energy transfer is a major non-radiative relaxation channel for large (8,4), (7,6) and (9,4) SWNTs, with excitation matching eh11, eh22,eh33 of (6,5).…”

“…In low-dimensional systems, exciton tunneling, photon-exchange and Förster Resonance Energy Transfer (FRET) are efficient exciton energy transfer mechanisms [11,12,13,14,15,30]. We attribute energy transfer in bundles to FRET.…”

“…FRET is a very efficient exciton energy transfer mechanism via a resonant, near-field, dipole-dipole interaction [11,12,13,14,15]. It is commonly observed in biological systems, conjugated polymers, wires, dots [11,12,13,14,15], where it dominates at short and intermediate distances (0.5-10nm) [11,12,13,14,15].…”

Plasmonic beaming and active control over fluorescent emission

“…Using such contacts, one can electrically pump a light-emitting device [28][29][30] , apply electric fields across electro-optic materials to modulate an optical signal 31 or even initiate electrochemical reactions. Here, we demonstrate how electric fields can be applied across the central slit of our beaming structures to tune the emission wavelength and intensity of QDs by means of the quantum-confined Stark effect 32,33 and luminescence quenching (Supplementary Methods). Figure 5a shows the voltage-dependent QD emission spectrum measured from our slit-groove sample.…”

Förster Coupling in Nanoparticle Excitonic Circuits

“…Thus, in addition to the desire to understand FRET in naturally occurring systems, the many photonic engineering systems currently under investigation motivate studies aimed at controlling the excitons and their interactions. As one example, tunability of the energy transfer between a nanorod and a dye molecule by an electric field was shown in [8]. In another case, control of exciton diffusion in excitonic integrated circuits was recently displayed [9].…”