Hemin interaction with bare and 4,4′-thio-bis-benzene-thiolate covered n-GaAs (110) electrodes

• Autores: Preda, Loredana; Negrila, Catalin; Lazarescu, Mihail F.; Anastasescu, Mihai; Dobrescu, Gianina; Santos, Elizabeth del Carmen; Lazarescu, Valentina
• Año de publicación: 2011
• Idioma: inglés
• Tipo de recurso: artículo
• Materia: second harmonic generation; GaAs; Hemin; Impedance
• Institución: Consejo Nacional de Investigaciones Científicas y Técnicas

Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) investigations on the redox behavior of hemin at bare and 4,4′-thio-bis-benzene-thiolate (TBBT) covered n-GaAs (110) electrodes in dimethylsulfoxide (DMSO) revealed the high irreversibility of the electroreduction process, which appeared to be closely related to the stable adsorbed species strongly interfering with the electronic properties of the semiconducting substrate. The subsequent exploration of the hemin-modified electrodes by second harmonic generation (SHG), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements pointed to significant differences between the iron protoporphyrin species adsorbed on the bare- and TBBT–GaAs (110) electrodes. Only Fe2+ species having a flat configuration with the porphyrin plane oriented parallel to the surface were detected on GaAs, unlike the TBBT–GaAs, where Fe2+ and Fe3+ species having both flat and vertical adsorption positions could be observed. These differences originate from the mutual interactions between the solvent, hemin and dithiolate molecules as well as their competition for the surface sites found to play a key role in the electrochemical process under discussion.
Fil: Preda, Loredana. No especifíca;
Fil: Negrila, Catalin. No especifíca;
Fil: Lazarescu, Mihail F.. No especifíca;
Fil: Anastasescu, Mihai. No especifíca;
Fil: Dobrescu, Gianina. No especifíca;
Fil: Santos, Elizabeth del Carmen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Córdoba. Instituto de Física Enrique Gaviola. Universidad Nacional de Córdoba. Instituto de Física Enrique Gaviola; Argentina
Fil: Lazarescu, Valentina. No especifíca;