Local Energy Transfer in Self-Assembled Polyelectrolyte Thin Films Probed by Near-Field Optics

Abstract

Near-field scanning optical microscopy (NSOM) has been used to investigate spatially localized energy transfer properties of self-assembled polyelectrolyte films consisting of poly(p-phenylene vinylene) (PPV) and poly(allylamine hydrochloride) (PAH) doped with Texas Red dye (TR-PAH). Local differences in energy transfer efficiency highlight the unique multilayer interpenetration properties of thin films constructed using the layer-by-layer (LbL) electrostatic self-assembly technique, as well as the importance of localized probes, to discern local variation that would not be observed using spatially averaged measurements.

Controlled Fluorescence Resonance Energy Transfer from Multiple Fluorophores in Layer‐by‐Layer Assemblies

“…In particular, LbL assemblies have been employed as model structures to investigate fluorescence resonance energy transfer (FRET) that involves non‐radiative energy transfer from excited‐state donors to ground‐state acceptors 13, 21–27. A variety of donor/acceptor pairs of fluorescent dyes and semiconductor nanoparticles that are either multiply charged by themselves13, 21, 22 or covalently attached to polyelectrolytes23–27 have been incorporated into the layers of LbL assemblies to control the energy transfer process. Since FRET strongly depends on the donor‐to‐acceptor distance,28, 29 the emissions from the thin film can be tuned by adjusting the deposition sequence of neat polyelectrolytes and fluorophores.…”

“…Since FRET strongly depends on the donor‐to‐acceptor distance,28, 29 the emissions from the thin film can be tuned by adjusting the deposition sequence of neat polyelectrolytes and fluorophores. However, most of the previous studies have been focused on a single kind of FRET event with a donor/acceptor pair of fluorophores 13, 21–27. The application of FRET in photonics and optoelectronics, however, requires further controls over multiple FRET events 30–33.…”

Tunable Phosphorescent Emission through Energy Transfer within Multilayer Thin Films Based on a Carbazole‐Based Host and Ir(III)‐Complex Guest System

“…They controlled the energy transfer efficiency by varying the distance between the donor and acceptor layer to investigate the internal structure of the multilayer films, [9][10][11] or to monitor the fluorescence signal based on the fluorescence quenching by varying the distance between the quencher and fluorophore layers. [12,13] The emission color has been controlled by changing the coating sequence and the adsorbed amount of two quantum dots with different colors.…”

Enhancement and Concurrence of Emissions from Multiple Fluorophores in a Single Emitting Layer of Micellar Nanostructures

“…Since the energy transfer between light-absorbing donors and energy-taking acceptors is strongly dependent on their mutual distance at a nanometer scale, [7] many synthetic nanostructures such as dendrimers, [8][9][10] zeolites, [11] sol-gel thin films, [12][13][14] and layer-by-layer thin films [15][16][17] have been employed for accurate nanoscale organization of fluorophores in specific locations. For effective collection and transportation of incident energy, donors and acceptors should be closely placed within their Fö rster radius.…”

“…[7] In a fluorescent pair of donor and acceptor molecules, for example, enhanced light emission of acceptors can be obtained even by the incident light with the wavelength at which acceptors have little absorption of the incident energy because donors can act as antenna molecules to harvest and transfer the incident energy. [8][9][10][11][12][13][14][15][16][17] Contrarily, to restrict the energy transfer, donors and acceptors should be placed beyond their Fö rster radius. [7] In a light-emitting diode (LED), for example, site-isolation of multiple fluorophores which can work as a donor-acceptor pair is desirable for multiple color emissions from a single emitting layer to efficiently fabricate devices without a multilayer structure.…”