Dielectric Interfaces Reshape Dynamic Single-Molecule Optical Fingerprints in Nanoscopic Polymer Films

ChemRxiv

Abstract

Fluorescence lifetimes near dielectric interfaces depend on molecular dipole orientation, but this relationship becomes more complex when emitters are confined within finite nanoscopic films. Here, we combine radially polarized excitation imaging with time-correlated single-photon counting to follow the orientation and fluorescence lifetime of individual PDI molecules undergoing rotational motion in thin poly(n-butyl methacrylate) films. Orientation-sensitive fluorescence patterns were analyzed using vectorial wave-optical simulations, enabling dipole orientation and excited-state lifetime to be correlated over time for the same emitter. The lifetime–orientation relationships vary systematically with film thickness and between molecules within the same film. Electrodynamic calculations for the glass–polymer–air geometry reproduce the principal trends and show that the observed heterogeneity is consistent with different axial emitter positions. These results establish single molecular dipoles as probes of finite nanoscopic dielectric environments.

Authors 6

1. Daniel Marx
2. David Malsbenden Aachen

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry

   RWTH Aachen University

3. Ivan A. Gligonov
4. Dominik Wöll Aachen

   RWTH Aachen University

   Affiliation as printed

   Institute of Physical Chemistry

   RWTH Aachen University

5. Jörg Enderlein

   Universitätsmedizin Göttingen · Multiscale Bioimaging

   Affiliation as printed

   Cluster of Excellence “Multiscale Bioimaging: from Molecular Machines to Networks of Excitable Cells” (MBExC

   Universitätsmedizin Göttingen

6. Oleksii Nevskyi