Detection of phase transients in two-dimensional adlayers of adenosine at the solid amalgam electrode surfaces

The application of amalgam-alloy electrodes (MeAEs) for the detection of the phase transients in two-dimensional (2D) adlayers of adenosine is shown. The electrochemical characterisation of the surface of the MeAEs used was performed by cyclic voltammetry (CV) and capacitance measurements (C-E curves). An optical diffractive element (DOE) based sensor was used for the inspection of the optical roughness of the bare and amalgamated surface of the metal electrodes. The kinetics of the phase transitions of adenosine adsorbed at the copper (CuAE), platinum (PtAE), and silver amalgam-alloy electrode (AgAE) was studied by chronoamperometry (j-t curves) and capacitance measurements (C-E curves). In the acid (pH 5) solution adenosine forms two different 2D physisorbed condensed adlayers at the MeAEs. The first of these (adlayer II) is located around the potential of -1.2 V, and the second 2D physisorbed film (adlayer III) is formed close to the potential of -0.5 V. Both of the adlayers II and III exist at the CuAE and PtAE substrates where the thickness of the amalgam-alloy layer is as low as 0.04 mum. The 2D condensed films of adenosine are poorly developed on the AgAE substrate. During the phase transition of adenosine from a dilute adsorption adlayer (region Ia) to a 2D physisorbed condensed film (region II) the polynucleation and growth process takes place at the CuAE and PtAE substrates. At the AgAE substrate only the adsorption process takes place. (C) 2004 Elsevier B.V. All rights reserved.