Quantitating the Binding Energy of Metal Ions to Langmuir-Blodgett Monolayers: The Copper(II)-Octadecylphosphonic Acid System.

We report on the formation and organization of a Cu 2+ -complexed octadecylphosphonic acid (ODPA) monolayer formed by Langmuir-Blodgett deposition. The formation of the Cu-complexed monolayer is seen to depend sensitively on the subphase pH and Cu 2+ concentration, and it is possible to form a monolayer containing the regions of complexed and free ODPA. From the pressure-area isotherm data for these monolayers, we determine the equilibrium constant and free energy of formation for the Cu 2+ -ODPA complex, Δ G = -22.5 kJ/mol.