AFM OF GUANINE ADSORBED ON HOPG UNDER ELECTROCHEMICAL CONTROL

摘要

The characterisation of the adsorption mechanism of guanine on a highly oriented pyrolytic graphite (HOPG) electrode surface was carried out using in situ MAC Mode Atomic Force Microscopy (MAC Mode AFM) and the electrochemical behaviour of the guanine layer was investigated with Electrochemical AFM. Guanine adsorbs spontaneously on the HOPG substrate as a stable molecular layer, covering the surface uniformly and almost completely. The adsorption of DNA at the HOPG surface was controlled by adjusting the potential of the HOPG electrode and electrochemical adsorption provides better attachment of the guanine at the electrode surface compared to natural adsorption. The characteristics of the adsorbed guanine films were dependent on the deposition time and on the electrochemical adsorption procedure. The film was dissolved by carrying out cyclic voltammetry between 0 and + 1.3 V, after which guanine started to readsorb freely on the clean HOPG surface. The guanine molecules were held together on the substrate mainly by non-covalent interactions such as hydrogen bonding, van der Waals and hydrophobic interactions.