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PreprintCC BYChemRxiv

NanoFTIR spectroscopy probes solvation electrostatics in nanoconfinement

  • Leonard Pfister1,2
  • Sviatoslav Kovalchuk2,3
  • Oguzhan Yüzel2,3
  • Kirill Bolotin2,3
  • Joachim Heberle1,2
  • Jacek Kozuch1,2,4
4 affiliations
  1. 1Physics Department, Experimental Molecular Biophysics, Freie Universität Berlin, Arnimallee 14, Germany, 14195
  2. 2Freie Universität Berlin, Altensteinstr. 23a, Germany, 14195
  3. 3Physics Department, Quantum nanoelectronics of 2D materials, Arnimallee 14, Germany, 14195
  4. 4Institute of Physical and Theoretical Chemistry, BRICS – Braunschweig Integrated Centre of Systems Biology, Physical Chemistry of Biomolecular Systems, Rebenring 56, Braunschweig, Germany, 38106
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Abstract

The structure and electrostatics of liquids change dramatically under nanometric confinement, suggesting that solvent-solute interactions in such environments differ fundamentally from those in the bulk. Here, we combine nanoscale Fourier-transform infrared spectroscopy (nanoFTIR) with the vibrational Stark effect (VSE) to directly map the local electric field experienced by a molecular probe—the C=O stretching vibration of dimethylformamide (DMF)—within buried nanofluidic channels. To this end, we fabricated hexagonal boron nitride (hBN)-capped trenches with depths ranging from ~100 nm down to 2.6 nm and filled them with a 1:1 (v/v) aqueous DMF solution. Under the strongest confinement (2.6 nm), the DMF C=O stretching mode exhibits a +17 cm -1 blueshift, corresponding to a substantial change in the local solvation electric field strength of 0.39 V Å -1 . Molecular dynamics (MD) simulations, combined with MD-derived IR spectra, reproduce the observed spectral shift and the associated change in local solvation electrostatics. The simulations further reveal the emergence of a quasi-phase-separated interfacial layer under finite-size confinement as the origin for the altered electrostatics. Together, these results establish nanoFTIR-based VSE spectroscopy as a direct and quantitative probe of nanosolvation electrostatics in nanoscale fluidic reactors.

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Cite

BibTeXRIS
BibTeX
@misc{pfister2026nanoftir,
  title = {{NanoFTIR spectroscopy probes solvation electrostatics in nanoconfinement}},
  author = {Leonard Pfister and Sviatoslav Kovalchuk and Oguzhan Yüzel and Kirill Bolotin and Joachim Heberle and Jacek Kozuch},
  howpublished = {ChemRxiv},
  year = {2026},
  month = sep,
  doi = {10.26434/chemrxiv.15008628/v1},
  url = {https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008628/v1},
  note = {CC BY},
}
RIS
TY  - UNPB
TI  - NanoFTIR spectroscopy probes solvation electrostatics in nanoconfinement
AU  - Leonard Pfister
AU  - Sviatoslav Kovalchuk
AU  - Oguzhan Yüzel
AU  - Kirill Bolotin
AU  - Joachim Heberle
AU  - Jacek Kozuch
PY  - 2026
DA  - 2026/09/10
PB  - ChemRxiv
DO  - 10.26434/chemrxiv.15008628/v1
UR  - https://chemrxiv.org/doi/full/10.26434/chemrxiv.15008628/v1
AB  - The structure and electrostatics of liquids change dramatically under nanometric confinement, suggesting that solvent-solute interactions in such environments differ fundamentally from those in the bulk. Here, we combine nanoscale Fourier-transform infrared spectroscopy (nanoFTIR) with the vibrational Stark effect (VSE) to directly map the local electric field experienced by a molecular probe—the C=O stretching vibration of dimethylformamide (DMF)—within buried nanofluidic channels. To this end, we fabricated hexagonal boron nitride (hBN)-capped trenches with depths ranging from ~100 nm down to 2.6 nm and filled them with a 1:1 (v/v) aqueous DMF solution. Under the strongest confinement (2.6 nm), the DMF C=O stretching mode exhibits a +17 cm -1 blueshift, corresponding to a substantial change in the local solvation electric field strength of 0.39 V Å -1 . Molecular dynamics (MD) simulations, combined with MD-derived IR spectra, reproduce the observed spectral shift and the associated change in local solvation electrostatics. The simulations further reveal the emergence of a quasi-phase-separated interfacial layer under finite-size confinement as the origin for the altered electrostatics. Together, these results establish nanoFTIR-based VSE spectroscopy as a direct and quantitative probe of nanosolvation electrostatics in nanoscale fluidic reactors.
ER  -