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.