Collective Effects Influencing Fluorescence Emission - Advanced Fluorescence Reporters in Chemistry and Biology - page 107

Collective Effects Influencing Fluorescence
Emission

Alexander P. Demchenko

Abstract Dramatic improvement of fluorescence sensing technologies can be
achieved by combining molecular emitters into clusters, nanoparticles, and aggre-
gates. This chapter addresses the new effects that appear on incorporation of dyes
into these supramolecular structures. We consider different types of intermolecular
interactions that influence the emission spectra, focusing on spectral changes that
are observed on concentrating organic dyes in confined media. The mechanisms of
energy transfer between fluorescence emitters are discussed. They provide possi-
bilities for increasing the dynamic range of sensing response by extending the
variation of intensity (light-harvesting, superquenching), and wavelength range
(directed transfer, wavelength-shifting).

Keywords Excimers Intermolecular interactions Light-harvesting Red-edge

effects Resonance energy transfer Superquenching Wavelength-shifting

Contents
1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 108
2 Spectroscopy of Intermolecular Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
2.1 Universal Intermolecular Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 109
2.2 Hydrogen Bonding in the Ground and Excited States . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 111
2.3 Excimers and Exciplexes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 112
3 Resonance Interactions between Fluorophores . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
3.1 Electron Exchange Interactions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
3.2 F¨rster Resonance Energy Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 113
4 Site-Selective Red-Edge Effects . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 114