Ion penetration of the water-oil interface

Ions typically pass with difficulty from water into organic phases because of water's superior solvation power. This inhibits such processes as ion tr ansport in batteries or in Lipid bilayers of cells. ion penetration across such an interface was studied with unusual structural control. Hydronium io ns were soft-landed at 1 electron volt on cold films of 3-methylpentane ("o il") on a metal substrate. The field produced by these ions drove them thro ugh the films when warmed. Coadsorption of water (0.14 to 35 bilayers) inhi bited the ion penetration by creating a solvation energy trap. A Born solva tion model successfully predicted the trapping energies (0 to 38 kilojoules per mole).