Paper SS-TuP9
Determining the Surface Electrical Potential at the Air/Water Interface

Tuesday, October 22, 2019, 6:30 pm, Room Union Station B

Several biological and chemical processes directly relate to the organization of molecules at the liquid surface. The surface electric potential across the air/liquid interface provides insight into the molecular organization and propagation of electrical fields by these surface molecules. Using a homemade Air Ionizing Surface Electrical Potential instrument, we measure the surface electrical potential of water, several pure solvents, and inorganic electrolyte solutions without disruption to the liquid surface. Alpha particle radiation from an ionizing source reduces the resistivity of the air gap above the liquid sample, establishing a closed electrical circuit for voltage measurements. From the measured surface potential, we show (i) the orientation of interfacial solvent molecules in pure solvents, and (ii) ascertain the propensity of specific aqueous ions with respect to the air/solution boundary.