Year: 2026
Type: preprint
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.
Source: ChemRxiv
Institution: Freie Universität Berlin
Language: English
Subfield: Atomic and Molecular Physics, and Optics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W7212136346