biostudies-literatureWright DLeverhulme TrustEuropean Research CouncilDeutsche Akademie der Naturforscher Leopoldina - Nationale Akademie der WissenschaftenUK Research and InnovationEngineering and Physical Sciences Research Council4905-4911https://www.ebi.ac.uk/biostudies/studies/S-EPMC9189927biostudies-literatureUnknown13(22)Molecules containing vibrational Stark shift reporters provide a useful tool for measuring DC electric fields <i>in situ</i>. To quantify this effect theoretically, density functional theory (DFT) calculations are usually utilized in a uniform electric field. However, using a combined theoretical and experimental study, we demonstrate here that uniform field DFT cannot simultaneously model the behavior of the three strongest vibrational modes in molecules forming a monolayer on an electrode. We show, by directly modeling ionic movement, that the measured Stark shifts are explained by partial electrical double-layer penetration into the molecular layer. This effect is sensitive to the local environment, and the Stark shifts can be fully suppressed experimentally by introducing a mixed molecThe journal of physical chemistry lettersVibrational Stark Effects: Ionic Influence on Local Fields.PMC9189927ECF-2018-375829067883703EP/L015978/1MR/S015329/2EP/L027151/1861950Lin QBaumberg JJSadeghi HSangtarash SWright DMueller NSfalseVibrational Stark Effects: Ionic Influence on Local Fields.Molecules containing vibrational Stark shift reporters provide a useful tool for measuring DC electric fields <i>in situ</i>. To quantify this effect theoretically, density functional theory (DFT) calculations are usually utilized in a uniform electric field. However, using a combined theoretical and experimental study, we demonstrate here that uniform field DFT cannot simultaneously model the behavior of the three strongest vibrational modes in molecules forming a monolayer on an electrode. We show, by directly modeling ionic movement, that the measured Stark shifts are explained by partial electrical double-layer penetration into the molecular layer. This effect is sensitive to the local environment, and the Stark shifts can be fully suppressed experimentally by introducing a mixed molec2022-01-01T00:00:00Z2022 Jun2025-04-05T15:33:59.457Z2025-04-05T15:33:59.457ZS-EPMC91899273562308910.1021/acs.jpclett.2c01048