Electrocatalytic properties of nanostructured melanin films on HOPG

A. GONZÁLEZ ORIVE; D. GRUMELLI; C. VERICAT; G. BENITEZ; A. HERNÁNDEZ CREUS; R. SALVAREZZA

Encuentro; 61st ISE Annual Meeting; 2010

Melanins are complex biopolymers that are widely distributed in living organisms. Asimple method to produce melanin-modified highly oriented pyrolytic graphite(HOPG) from synthetic eumelanin containing aqueous alkaline solutions by means ofelectrochemical self-assembly is reported. These films were characterized by X-rayphotoelectron spectroscopy (XPS), magnetic force microscopy (MFM) operating intapping mode, and also by cyclic voltammetry. Melanin deposits consist ofnanoparticles 8-40 nm in size and 0.35-6 nm in height depending on the depositiontime. The growth starts with the nucleation and growth of melanin islands at step edgesfollowed by their growth at terraces forming ramified structures. The melanin islandsturn the chemically inert HOPG surface into a highly active surface able to bind largeamounts of iron oxide species. The MFM images show different iron rich zones on thesurface (Fig. 1). The iron-melanin modified HOPG surface becomes electrocataliticallyactive for the electroreduction of hydrogen peroxide, oxygen and molecules such asnitrite in alkali and neutral solutions. These results are interesting for using the HOPGmelaninsystem in electrocatalysis, electroanalysis and also as a biomimetic system forstudying melanoma cell targeting with metallic cation modified drugs.