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PreprintCC BYChemRxiv

Imaging of ultrafast electronic and chemical dynamics in biological systems

  • Ligong Zhao1,2,3,4
  • Mohamed Sennary1,2
  • Anaísa Coelho5,6
  • Tingting Yang5,6
  • Nir Sukenik5,6
  • Dina Hussein1,2
  • Olga E. Eremina7,6
  • Mohamed Y El-Naggar5,6,8,9
  • Mohammed Th. Hassan1,2
9 affiliations
  1. 1Department of Physics
  2. 2University of Arizona
  3. 3Center for Attosecond Science and Technology
  4. 4Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences
  5. 5Department of Physics and Astronomy
  6. 6University of Southern California
  7. 7Alfred E. Mann Department of Biomedical Engineering
  8. 8Department of Chemistry
  9. 9Department of Biological Sciences
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Abstract

Ultrafast electron microscopy (UEM) has enabled real-space visualization of dynamics in inorganic nanomaterials on fundamental timescales, but its application to functional biological nanostructures remains largely unexplored. Here, we use time-resolved UEM and electron energyloss spectroscopy (EELS) to probe the photoinduced electronic response and the light-induced chemical modification of the conductive periplasmic nanofiber network extracted from filamentous cable bacteria. Low-loss EELS reveals a feature at 3.6 eV, assigned to π→π* excitations, that is absent in non-conductive bacterial controls. Upon femtosecond near-infrared excitation (800 nm, 4.8 mJ cm−2), the spectral weights of this π feature and of the collective valence excitation at 23.1 eV decrease by ~10% and ~8%, respectively, within the first ~2 ps and largely recover within a few picoseconds, leaving a small long-lived component. A comparison with the expected photothermal response indicates that this transient is dominated by electronic excitation. Power-dependent core-loss EELS and elemental mapping under quasi-continuous illumination show that cumulative exposure irreversibly depletes nitrogen and oxygen, relatively enriches sp2bonded carbon and causes partial mass loss, while the outline of the nanofiber network is preserved. These results establish time-resolved EELS as a probe of the electronic photoresponse and photostability of biological conductors, and show how transient electronic and cumulative chemical light-induced effects can be distinguished in such systems.

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Cite

BibTeXRIS
BibTeX
@misc{zhao2026imaging,
  title = {{Imaging of ultrafast electronic and chemical dynamics in biological systems}},
  author = {Ligong Zhao and Mohamed Sennary and Anaísa Coelho and Tingting Yang and Nir Sukenik and Dina Hussein and Olga E. Eremina and Mohamed Y El-Naggar and Mohammed Th. Hassan},
  howpublished = {ChemRxiv},
  year = {2026},
  month = oct,
  doi = {10.26434/chemrxiv.15010541/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010541/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - Imaging of ultrafast electronic and chemical dynamics in biological systems
AU  - Ligong Zhao
AU  - Mohamed Sennary
AU  - Anaísa Coelho
AU  - Tingting Yang
AU  - Nir Sukenik
AU  - Dina Hussein
AU  - Olga E. Eremina
AU  - Mohamed Y El-Naggar
AU  - Mohammed Th. Hassan
PY  - 2026
DA  - 2026/10/15
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15010541/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15010541/v1
AB  - Ultrafast electron microscopy (UEM) has enabled real-space visualization of dynamics in inorganic nanomaterials on fundamental timescales, but its application to functional biological nanostructures remains largely unexplored. Here, we use time-resolved UEM and electron energyloss spectroscopy (EELS) to probe the photoinduced electronic response and the light-induced chemical modification of the conductive periplasmic nanofiber network extracted from filamentous cable bacteria. Low-loss EELS reveals a feature at 3.6 eV, assigned to π→π* excitations, that is absent in non-conductive bacterial controls. Upon femtosecond near-infrared excitation (800 nm, 4.8 mJ cm−2), the spectral weights of this π feature and of the collective valence excitation at 23.1 eV decrease by ~10% and ~8%, respectively, within the first ~2 ps and largely recover within a few picoseconds, leaving a small long-lived component. A comparison with the expected photothermal response indicates that this transient is dominated by electronic excitation. Power-dependent core-loss EELS and elemental mapping under quasi-continuous illumination show that cumulative exposure irreversibly depletes nitrogen and oxygen, relatively enriches sp2bonded carbon and causes partial mass loss, while the outline of the nanofiber network is preserved. These results establish time-resolved EELS as a probe of the electronic photoresponse and photostability of biological conductors, and show how transient electronic and cumulative chemical light-induced effects can be distinguished in such systems.
ER  -