@article{GrandeSoberatsHerbstetal.2018,
  author    = {Grande, Vincenzo and Soberats, Bartolome and Herbst, Stefanie and Stepanenko, Vladimir and W{\"u}rthner, Frank},
  title     = {Hydrogen-bonded perylene bisimide J-aggregate aqua material},
  volume    = {9},
  issn      = {2041-6539},
  doi       = {10.1039/C8SC02409J},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-204715},
  pages     = {6904-6911},
  year      = {2018},
  abstract  = {A new twelvefold methoxy-triethyleneglycol-jacketed tetraphenoxy-perylene bisimide (MEG-PBI) amphiphile was synthesized that self-assembles into two types of supramolecular aggregates in water: red-coloured aggregates of low order and with weak exciton coupling among the PBIs and blue-coloured strongly coupled J-aggregates consisting of a highly ordered hydrogen-bonded triple helix of PBIs. At room temperature this PBI is miscible with water at any proportions which enables the development of robust dye aggregates in solution, in hydrogel states and in lyotropic liquid crystalline states. In the presence of 60-95 wt\% water, self-standing coloured hydrogels exhibit colour changes from red to blue accompanied by a fluorescence light-up in the far-red region upon heating in the range of 30-50 °C. This phenomenon is triggered by an entropically driven temperature-induced hydrogen-bond-directed slipped stacking arrangement of the MEG-PBI chromophores within structurally well-defined J-aggregates. This versatile aqua material is the first example of a stable PBI J-aggregate in water. We anticipate that this study will open a new avenue for the development of biocompatible functional materials based on self-assembled dyes and inspire the construction of other hydrogen-bonded supramolecular materials in the highly competitive solvent water.},
  language  = {en}
}
@article{DostalFennelKochetal.2018,
  author    = {Dost{\´a}l, Jakub and Fennel, Franziska and Koch, Federico and Herbst, Stefanie and W{\"u}rthner, Frank and Brixner, Tobias},
  title     = {Direct observation of exciton-exciton interactions},
  series = {Nature Communications},
  volume    = {9},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-018-04884-4},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-226271},
  year      = {2018},
  abstract  = {Natural light harvesting as well as optoelectronic and photovoltaic devices depend on efficient transport of energy following photoexcitation. Using common spectroscopic methods, however, it is challenging to discriminate one-exciton dynamics from multi-exciton interactions that arise when more than one excitation is present in the system. Here we introduce a coherent two-dimensional spectroscopic method that provides a signal only in case that the presence of one exciton influences the behavior of another one. Exemplarily, we monitor exciton diffusion by annihilation in a perylene bisimide-based J-aggregate. We determine quantitatively the exciton diffusion constant from exciton-exciton-interaction 2D spectra and reconstruct the annihilation-free dynamics for large pump powers. The latter enables for ultrafast spectroscopy at much higher intensities than conventionally possible and thus improves signal-to-noise ratios for multichromophore systems; the former recovers spatio-temporal dynamics for a broad range of phenomena in which exciton interactions are present.},
  language  = {en}
}
@article{GoerlSoberatsHerbstetal.2016,
  author    = {G{\"o}rl, Daniel and Soberats, Bartolome and Herbst, Stefanie and Stepanenko, Vladimir and W{\"u}rthner, Frank},
  title     = {Perylene bisimide hydrogels and lyotropic liquid crystals with temperature-responsive color change},
  series = {Chemical Science},
  volume    = {7},
  journal   = {Chemical Science},
  number    = {11},
  doi       = {10.1039/c6sc02249a},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-162459},
  pages     = {6786-6790},
  year      = {2016},
  abstract  = {The self-assembly of perylene bisimide (PBI) dyes bearing oligo ethylene glycol (OEG) units in water affords responsive functional nanostructures characterized by their lower critical solution temperature (LCST). Tuning of the LCST is realized by a supramolecular approach that relies on two structurally closely related PBI-OEG molecules. The two PBIs socially co-assemble in water and the resulting nanostructures exhibit a single LCST in between the transition temperatures of the aggregates formed by single components. This permits to precisely tune the transition from a hydrogel to a lyotropic liquid crystal state at temperatures between 26 and 51 °C by adjusting the molar fraction of the two PBIs. Owing to concomitant changes in PBI-PBI interactions this phase transition affords a pronounced color change with "fluorescence-on" response that can be utilized as a smart temperature sensory system.},
  language  = {en}
}