We study the properties of the interface of water and the surfactant hexaethylene glycol monododecyl ether (C12E6) with a combination of heterodyne-detected vibrational sum frequency generation (HD-VSFG), Kelvin-probe measurements, and molecular dynamics (MD) simulations. We observe that the addition of the hydrogen-bonding surfactant C12E6, close to the critical micelle concentration (CMC), induces a drastic enhancement in the hydrogen bond strength of the water molecules close to the interface, as well as a flip in their net orientation. The mutual orientation of the water and C12E6 molecules leads to the emergence of a broad (∼3 nm) interface with a large electric field of ∼1 V/nm, as evidenced by the Kelvin-probe measurements and MD simulations. Our findings may open the door for the design of novel electric-field-tuned catalytic and light-harvesting systems anchored at the water–surfactant–air interface.

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J. Am. Chem. Soc.
Ultrafast Spectroscopy

Gera, R., Bakker, H., Franklin-Mergarejo, R., Morzan, U., Falciani, G., Bergamasco, L., … Hassanali, A. (2021). Emergence of Electric Fields at the Water–C12E6 Surfactant Interface. J. Am. Chem. Soc., 143(37), 15103–15112. doi:10.1021/jacs.1c05112