Permeability of alkanethiol self-assembled monolayers adsorbed on copper electrodes to molecular oxygen dissolved in 0.5 m Na2SO4 solution

Closely packed self-assembled monolayers of alkanethiols (CnT) adsorbed on the copper surface are applicable as protective films against copper corrosion in aerated aqueous solution and atmospheric environments. They act as barrier to oxygen diffusion, since the cathodic process of copper corrosion is suppressed by coating the surface with the CnT monolayer. Diffusion process of molecular oxygen dissolved in 0.5 M Na2SO4 within the CnT self-assembled monolayer adsorbed on copper was investigated by hydrodynamic voltammetry. The diffusion process within the monolayer films of C10T similar to C18T was explained by the permeation model, while a combination of the permeation model with the defect model was applied to diffusion of oxygen within the C6T and C8T monolayer films. Because of the wettability at the film surface, hydrated oxygen molecules could enter into the 11-mercapto-1-undecanol self-assembled monolayer without difficulty.