Get charged up: Nonlinear optical voltammetry for quantifying the thermodynamics and electrostatics of metal cations at aqueous/oxide interfaces

This Letter provides a tutorial review of how the Eisenthal χ(3) Technique can be applied as a general method for quantifying (1) the amount of metal ions adsorbed, (2) the electrostatics associated with the adsorption processes, and (3) the thermodynamics, kinetics, and molecular mechanisms that underlie the interaction of the metal ions with aqueous/solid interfaces. We focus on our recent effort to quantify potentials at aqueous/solid interfaces in the presence of magnesium, calcium, strontium, and barium cations and determine alkaline earth metal ion adsorption thermodynamics at pH 7 and 10 mM NaCl. Important theoretical considerations for this method are discussed as well.