title: Reorganization of perylene bisimide J-aggregates: from delocalized collective to localized individual excitations.
abstract: Water-induced reorganization of individual one-dimensional J-aggregates of perylene bisimide (PBI) dyes was observed by fluorescence microscopy. Fluorescence spectra and decay kinetics of individual J-aggregates immobilized on glass surfaces were measured under a dry nitrogen atmosphere and under humid conditions. The fluorescence properties of PBI J-aggregates arisen from collective excitons under dry nitrogen atmosphere were changed to those of non-interacting dye monomers when water vapor was introduced into the environment (sample chamber). Time-dependent changes of the fluorescence spectra and lifetimes upon exposure to water vapor suggest an initial coordination of water molecules at defect sites leading to the formation of H-type dimer units that act as exciton quenchers, and a subsequent slower disintegration of the hydrogen-bonded J-aggregate into monomers that lack resonance coupling. Our present studies resulted in a direct demonstration of how drastically the optical properties of molecular ensembles and characteristics of their excited states can be changed by delicate reorganization of dye molecules at nanometre scales.
authors.affiliation: Chemical Physics, Lund University, Box 124, 22100, Lund, Sweden.
authors.forename: Yuxi
authors.initials: Y
authors.lastname: Tian
authors.forename: Vladimir
authors.initials: V
authors.lastname: Stepanenko
authors.forename: Theo E
authors.initials: TE
authors.lastname: Kaiser
authors.forename: Frank
authors.initials: F
authors.lastname: Würthner
authors.forename: Ivan G
authors.initials: IG
authors.lastname: Scheblykin