Experimental and theoretical studies of l-cysteine adsorbed at Ag(1 1 1) electrodes |
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Authors: | E. Santos,L. Avalle,P. Vé lez |
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Affiliation: | a Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina b Facultad de Ciencias Químicas, Universidad Nacional de Córdoba, 5000 Córdoba, Argentina c University of Ulm, 89069 Ulm, Germany |
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Abstract: | We have investigated l-cysteine adsorbed on Ag(1 1 1) electrodes under different conditions. We have employed experimental and theoretical approaches to obtain a better understanding of the adsorbed layer. An estimation of the coverage from charge measurements and the second harmonic response shows C3v symmetry for the interface indicating a (√3 × √3)R°30 overlayer. The theoretical calculations show a variety of different structures with local adsorption energy minima. Particularly, under special initial conditions, zwitterionic structures adsorbed at different sites have been found. This can account for the multiplicity of redox processes observed experimentally below the potential of zero charge. The presence of an external field produces the stabilization of the zwitterion by interaction of the amino/carboxylic groups with the substrate. |
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Keywords: | smallcaps" >l-Cysteine Self-assembled monolayer Second harmonic generation Density functional theory Adsorption |
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