Emergence of Electric Fields at the Water–C12E6 Surfactant Interface
Rahul Gera, Huib J. Bakker, Ricardo Franklin-Mergarejo, Uriel N. Morzan, Gabriele Falciani, Luca Bergamasco, Jan Versluis, Indraneel Sen, Silvia Dante, Eliodoro Chiavazzo, Ali Hassanali
Abstract
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.