Adsorption of 1,3-Dimethyluracil at the Au(111)/Aqueous Electrolyte Interface. A Chronocoulometric Study

The interfacial behavior of 1,3-dimethyluracil (1,3-DMU) on Au(111) has been investigated quantitatively using chronocoulometry. The adsorption parameters such as film pressure, relative Gibbs surface excess, Gibbs energy of adsorption, and electrosorption valency were determined as a function of electrode potential and charge density for concentrations of 1,3-DMU up to 50 mM. The values of the relative Gibbs surface excess and the small shift of the zero charge potential due to 1,3-DMU adsorption, E NI, indicate that the organic molecules are oriented parallel to the electrode surface within the entire region of an ideal polarizable interface. The Gibbs energy at maximum adsorption is equal to −35.4 kJ mol-1 and suggests weak chemisorption. The strategy of analyzing chronocoulometric data, as shown in the present communication, provides the tools for a subsequent project aimed to address the role of the adsorbate structure on the thermodynamics of adsorption and phase-formation of N- and C-alkylated uracil derivatives on single crystal electrodes.