Self-assembled peptide nanostructures are electronically insulating as are most biomaterials derived from natural amino acids. To obtain additional properties and increase the applicability of peptide nanomaterials, some chemical modifications can be performed and materials can be functionalized to form hybrid compounds. In this work, we described the formation of L-diphenylalanine nanotubes (PNTs) with cyclic-tetrameric copper(II) species containing the ligand (4-imidazolyl)ethylene-2-amino-1-ethylpyridine [Cu(4)(apyhist)(4)](4+) in the Nafion membrane on a vitreous carbon electrode surface. This copper complex has been studied as structural and functional models for the active centers of copper containing redox enzymes. Scanning electron microscopy was used to confirm the formation of the nanostructures. The electrochemical properties of the PNT-[Cu(4)(apyhist)(4)](4+)/Nafion film on a glassy carbon electrode were characterized using cyclic voltammetry and square-wave voltammetry and showed high electrocatalytic activity toward the oxidation of dopamine (DA). The detection sensitivity was found to be enhanced by the use of copper(II) complex in the PNTs/Nafion films. Under the optimum conditions, the square-wave voltammetry peak height was linearly related to the DA concentration over two concentration intervals, viz., 5.0-40 μmol L(-1) and 40-1000 μmol L(-1). The detection limit was 2.80 μmol L(-1) (S/N = 3), and ascorbic acid did not interfere with the DA detection. These results suggested that this hybrid bioinorganic system provides an attractive advantage for a new type of electrochemical sensors. The detection sensitivity was found to be enhanced by use of PNTs.
Recebido em 2/12/10; aceito em 4/5/11; publicado na web em 8/7/11 ELECTROCATALYTIC ACTIVITY OF CATALASE BIOMIMETIC SYSTEMS. In this work, we describe the immobilization of the dinuclear compound [Cu 2 (apyhist) 2 Cl 2 ](ClO 4 ) 2 (1) and its derived cations complexes, obtained in water solution or by deprotonation of the imidazolate moiety in the ligand leading to a cyclic tetranuclear species, in the Nafion ® membrane on glass carbon electrode surface. After that, we studied the influence of the equilibrium in the electrocatalytic activity towards the reduction of H 2 O 2 in the development of an amperometric sensor for the analytical determination of hydrogen peroxide. This strategy proved successful, and the electrochemical behaviour of the all complexes formed within the Nafion ® coatings was characterized. We also provide evidence that its related cyclic tetranuclear imidazolate-bridged complex acts as a catalysts for the intramolecular, two-electron reduction of H 2 O 2 .
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