Forster energy transfer Principles

Forster, Th 211, 278, 282, 285 Forster resonance energy transfer, 282 Forster singlet energy transfer, 378 Franck-Condon factors, 23 Franck-Condon principle, 5 Franck-Condon transition, 5 French, C. S., 555 Friedman, G., 353 Fritzsche, J., 37 Frosch, R. P 252, 267, 269 Fumaronitrile, photodimerization in solid state, 478... 

Given the density of Chi in PSI, it is immediately obvious that any detailed description of energy transfer in this system will need to handle both weakly coupled (Forster-type) and strongly coupled (excitonic) systems self consistently. It is also evident that discerning rate limiting steps and optimizing principles may not be straightforward. 

Figure 16.25 Semiconductor nanoparticle-based fluorescent sensors (a) Forster resonant energy transfer (FRET) between two nanoparticles induced by analyte, (b) crown ether receptor for potassium ions, and (c) operation principle of maltose fluorescent sensor. (Adapted from Chen et at. [144] and Medintz et at. [146])...

Details on the mechanisms and theories of excitation energy transfer via dipole-dipole interaction (FRET Forster resonance energy transfer) and via exchange interaction (Dexter s mechanism) can be found in B. Valeur, Molecular Fluorescence. Principles and Applications, Wiley-VCH, Weinheim, 2002, chap. 4 and 9. 

An approach with indirect injection of electron-hole excitations into nanocrystals by the above described noncontact nonradiative Forster-like energy transfer from a proximal quantum well that can in principle be pumped either electrically or optically, can solve the problem of pumping of nanocrystals. The result obtained by the Klimov group indicate that this energy transfer is fast enough to compete with electron-hole recombination in the quantum well, and results in... 

Here we present a brief review of the physical principles underlying fluorescence energy transfer. The theory was developed primarily by Fdrster and extended by Dexter.Forster did some early experimental studies, and Stryer and Haugland convincingly showed that fluorescence energy transfer could be used as a molecular ruler to measure distances. Emphasis is on developing an intuitive feel for the important relevant parameters. Both a classical and a quantum mechanical approach are given. 

The rate of quenching depends on how the quenchers are distributed within the environment and in general also on the rate of the diffusive motion of both the excited state and the quencher, leading to an encounter between them. In the case of excitation energy transfer, the interaction may occur over a considerable distance, the Forster radius, which may exceed 4 nm for many interesting donor-acceptor pairs. A donor with a short excited state lifetime can be employed, so that the transfer occurs with little change in the donor and acceptor positions. Under such circumstances the fluorescence decay can provide information on the distribution of acceptors around the donor. In principle, it should be poss-... 

Energy transfer fibers are based on the principle that, upon excitation, a donor molecule wUl transfer a portion of its energy to an acceptor molecule if there is overlap between the donor s emission and the acceptor s absorption spectrum. This transfer occurs without the emission of a photon and is primarily the result of a dipole-dipole Interaction between the donor and acceptor. The efficiency of singlet dlpde-dipoie energy transfer is predicted by Forster theory (27). 

In fact, FRET (Forster resonant energy transfer) analysis has the same basis as the energy transfer described in the above section. It is used either in simple bioanalyses or to detect protein interactions and DNA hybridization. Its principle is shown on Fig. 14 in the case of a homogeneous immunoassay [43]. 

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