This paper describes the formation of polymeric films derived from 3-hydroxyphenylacetic acid electropolymerized onto graphite electrodes through cyclic voltammetry. We observed the formation of an electroactive material over the electrode surface. The modified electrode showed significant blocking behavior to electron transfer reaction of the pair redox ferricyanide/ferrocyanide, indicating repulsion electrostatic with the negatively charged carboxylate groups of the polymer. The quasi-reversible behavior to Ru(NH3)6Cl2 suggests electrostatic attraction, facilitating the charge transfer. The modified electrode was studied through electrochemical quartz crystal microbalance, electrochemical impedance spectroscopy, and atomic force microscopy. These analyses indicate modification of the graphite electrode. Surface analysis by AFM showed that the morphology of the modified electrode surface presents globular form, randomly distributed, and formed by lower globules with diameter near 100 nm. Immobilization and hybridization of oligonucleotide onto the modified electrode were successfully carried out by using both direct electrochemical oxidation of nitrogenated bases and the redox electroactive indicator methylene blue.
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The authors are grateful for financial support from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), and Fundação de Amparo a Pesquisa do Estado de Minas Gerais (FAPEMIG). Also, we would like to thank teacher Abílio Borghi for the revision of the English manuscript.