l-Cysteine films on Ag(1Â 1Â 1) investigated by electrochemical and nonlinear optical methods

The electrochemical behaviour and nonlinear optical properties of l-Cysteine on Ag(1 1 1) single crystal electrodes in a non adsorbing electrolyte have been investigated for the first time. l-Cysteine adsorbs on Ag(1 1 1) stronger than on Au(1 1 1) and is stable over a wider range of potential. Reduction/oxidation processes have been identified at potentials well below the potential of zero charge. The adsorption process at a controlled potential value has been followed by measurements of the second harmonic response, which mainly responds to the electronic changes produced at the interface by the formation of the Ag-S bond. The film formed on Ag(1 1 1) exhibits rather insulating properties in the potential region positive to the potential of zero charge.