title: Hemin interaction with bare and 4,4'-thio-bis-benzene-thiolate covered n-GaAs (110) electrodes.
abstract: 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 Fe(2+) species having a flat configuration with the porphyrin plane oriented parallel to the surface were detected on GaAs, unlike the TBBT-GaAs, where Fe(2+) and Fe(3+) 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.
authors.affiliation: Romanian Academy-Institute of Physical Chemistry Ilie Murgulescu, Spl. Independentei nr. 202, Bucharest, Romania.
authors.forename: Loredana
authors.initials: L
authors.lastname: Preda
authors.forename: Catalin
authors.initials: C
authors.lastname: Negrila
authors.forename: Mihail F
authors.initials: MF
authors.lastname: Lazarescu
authors.forename: Mihai
authors.initials: M
authors.lastname: Anastasescu
authors.forename: Gianina
authors.initials: G
authors.lastname: Dobrescu
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Santos
authors.forename: Valentina
authors.initials: V
authors.lastname: Lazarescu
mesh_terms: D001152:Arsenicals / Q000737:chemistry; D001554:Benzene / Q000737:chemistry*; D058266:Dielectric Spectroscopy; D055664:Electrochemical Techniques; D004566:Electrodes; D005708:Gallium / Q000737:chemistry; D006427:Hemin / Q000737:chemistry*; D018625:Microscopy, Atomic Force; D010084:Oxidation-Reduction; D056951:Photoelectron Spectroscopy; D013438:Sulfhydryl Compounds / Q000737:chemistry*
chemical_list: D001152:Arsenicals; D013438:Sulfhydryl Compounds; C043055:gallium arsenide; D006427:Hemin; D005708:Gallium; D001554:Benzene