Electrocatalytic and Magnetic Properties of Ultrathin Nanostructured Iron–Melanin Films on Au(111)

Alejandro González Orive,Felix Requejo,Roberto C Salvarezza,Pilar Díaz,Yurima Gimeno,Patricio Dip,Pilar Carro,Leandro Andrini,Alberto Hernández Creus,Patricia L Schilardi,Guillermo Benítez

doi:10.1002/chem.200600492

Abstract

We have prepared ultrathin, nanostructured melanin films on Au(111) by means of electrochemical self-assembly. These films were characterized by using Auger electron spectroscopy, X-ray absorption near-edge structure spectroscopy, scanning tunneling microscopy, magnetic force microscopy, and electrochemical techniques. Two types of nanostructures are present in the film: melanin nanoparticles and Fe(3)O(4) nanoparticles. The melanin nanoparticles contain Fe bonded to oxygen-containing phenolic groups in an octahedral configuration similar to that found in Fe(2)O(3). The inorganic-organic composite exhibits magnetic properties and catalyzes the electroreduction of hydrogen peroxide in alkaline and neutral electrolyte solutions. The electrocatalytic activity depends on the Fe-bound melanin and appears to be similar to that found for Fe-porphyrins.

Highlights

Melanins are complex biopolymers that are widely distributed in living organisms
In this work we explore the electrochemical and magnetic properties of Fe-containing, nanostructured ultrathin melanin films electrochemically self-assembled on AuACHTUNGRE(111)
Auger electron spectroscopy (AES) characterization: A Typical AES spectrum for a melanin film grown for ta = 100 min on Au is shown in Figure 1a

Summary

Introduction

Melanins are complex biopolymers that are widely distributed in living organisms. The most widespread, eumelanin, comprises molecular species derived from the coupling of 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) monomers, which aggregate and form granules.[1]. With this value (obtained as it was indicated in the Experimental Section), the relative concentration of Fe species in melanin films on AuACHTUNGRE(111) is estimated by considering the XANES spectra (spectra a and b in Figure 2) as a linear superposition from only two different absorbing Fe sites: Fe2+ in Fe3O4 and Fe3+ in melanin.

Results

Conclusion