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PreprintCC BY-NC-NDChemRxiv

Order in Disorder: Exciton Dynamics Reveal Short-Range Molecular Packing in Small-Molecule Ionic Isolation Lattices Fluorescent Nanoparticles

  • Simin Jiang1,2
  • Siyu Liu1,2
  • Jakub Dostál3
  • Amar H. Flood4,5
  • Bo W. Laursen1,2
  • Junsheng Chen1,2,4,5
5 affiliations
  1. 1Nano-Science Center and Department of Chemistry
  2. 2University of Copenhagen
  3. 3ELI Beam lines Facility, The Extreme Light Infrastructure ERIC
  4. 4Department of Chemistry
  5. 5Indiana University
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Abstract

Organic fluorescent nanoparticles (NPs) enable exceptional brightness through high dye loading, yet the fundamental relationship between local molecular organization and exciton dynamics remains elusive because short-range packing in densely packed assemblies is difficult to resolve using conventional structural characterization techniques. Here, femtosecond transient absorption spectroscopy reveals hidden short-range orientational order within globally disordered small-molecule ionic isolation lattice NPs (SMILES NPs) and establishes how this local organization governs exciton transport and fluorescence loss. Within locally ordered domains, fluorophore orientations are isotropically distributed within a two-dimensional plane perpendicular to the local stacking axis. Such local structural organization enables ultrafast exciton migration, followed by efficient energy funneling into non-emissive traps on a ~100 ps timescale, defining a kinetic window for exciton harvesting. Guided by this mechanistic insight, we introduce an emissive acceptor that captures excitons through sub-50 ps energy transfer, outcompeting trap-assisted quenching and producing binary SMILES NPs with a brightness per volume of 8700 M -1 cm -1 nm -3 , among the highest reported in the deep-red/near-infrared region. Collectively, this work establishes exciton dynamics as powerful probe of short-range molecular organization in dense molecular nanostructures and provides a molecular-packing-driven framework for controlling exciton transport and energy flow, offering general design principles for next-generation ultrabright emitters.

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Cite

BibTeXRIS
BibTeX
@misc{jiang2026order,
  title = {{Order in Disorder: Exciton Dynamics Reveal Short-Range Molecular Packing in Small-Molecule Ionic Isolation Lattices Fluorescent Nanoparticles}},
  author = {Simin Jiang and Siyu Liu and Jakub Dostál and Amar H. Flood and Bo W. Laursen and Junsheng Chen},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15008882/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008882/v1},
  note = {CC BY-NC-ND},
}
RIS
TY  - UNPB
TI  - Order in Disorder: Exciton Dynamics Reveal Short-Range Molecular Packing in Small-Molecule Ionic Isolation Lattices Fluorescent Nanoparticles
AU  - Simin Jiang
AU  - Siyu Liu
AU  - Jakub Dostál
AU  - Amar H. Flood
AU  - Bo W. Laursen
AU  - Junsheng Chen
PY  - 2026
DA  - 2026/09/15
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15008882/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008882/v1
AB  - Organic fluorescent nanoparticles (NPs) enable exceptional brightness through high dye loading, yet the fundamental relationship between local molecular organization and exciton dynamics remains elusive because short-range packing in densely packed assemblies is difficult to resolve using conventional structural characterization techniques. Here, femtosecond transient absorption spectroscopy reveals hidden short-range orientational order within globally disordered small-molecule ionic isolation lattice NPs (SMILES NPs) and establishes how this local organization governs exciton transport and fluorescence loss. Within locally ordered domains, fluorophore orientations are isotropically distributed within a two-dimensional plane perpendicular to the local stacking axis. Such local structural organization enables ultrafast exciton migration, followed by efficient energy funneling into non-emissive traps on a ~100 ps timescale, defining a kinetic window for exciton harvesting. Guided by this mechanistic insight, we introduce an emissive acceptor that captures excitons through sub-50 ps energy transfer, outcompeting trap-assisted quenching and producing binary SMILES NPs with a brightness per volume of 8700 M -1 cm -1 nm -3 , among the highest reported in the deep-red/near-infrared region. Collectively, this work establishes exciton dynamics as powerful probe of short-range molecular organization in dense molecular nanostructures and provides a molecular-packing-driven framework for controlling exciton transport and energy flow, offering general design principles for next-generation ultrabright emitters.
ER  -