Potential-dependent adsorption/desorption of organic adsorbate at HOPG electrode and accompanying delamination of graphite surface

In situ electrochemical scanning tunneling microscopy, alternating current voltammetry, and electrochemical quartz crystal microbalance have been empl oyed to follow the potential-dependent adsorption/desorption processes of n ucleic acid bases on highly oriented pyrolytic graphite (HOPG) electrode. T he results show that (i) potential-dependent adsorption/desorption of nucle ic acid bases on HOPG electrode was accompanied by delamination of the HOPG surface, and the delamination initiates from steps or kinks on the electro de surface, which provide highly active sites for adsorption; (ii) the dela mination usually occurred when the electrode potential was changed or when the electrode was at potentials where the phase transition of adsorbate occ urred. These results suggest that the surface stress resulting from the int eraction between the substrate and adsorbate, as well as the interaction du e to potential-induced surface charge distribution and the hysteresis of ch arge equilibrium are the main factors resulting in HOPG delamination. (C) 1 999 The Electrochemical Society. S0013-4651(97)12-013-4. All rights reserve d.