Electrochemistry of Lumiflavin Adsorbed at Mercury Acidic Aqueous Solution Interface

CECILIA BONAZZOLA; GABRIEL GORDILLO

JOURNAL OF ELECTROANALYTICAL CHEMISTRY

Año: 2006

0022-0728

The adsorption of the oxidized and the reduced forms of lumiflavin (_0.150 V and _0.450 V, respectively) at pH 4.5, and the electrochemical conversion of them were investigated. Two adsorbed surface stages could be distinguished for each oxidation state. Vertical interactions between adsorbed molecules lead to bilayer formation at high surface concentration. These interactions are stronger for the reduced form (H2LF) than the corresponding oxidized (LF) molecule. Surface charge values for a virtual monolayer of QM = 17 lC cm_2 for both, LF andH2LF, and the corresponding capacitances of 16 lF cm_2 and 11 lF cm_2 were obtained, respectively. The electrochemical behaviour of adsorbed species under sub-monolayer coverage is characterized as a quasi-reversible redox process conditioned by molecular lateral interactions. The apparent standard rate constant for the overall two-electron process, k0 = 295 s_1, and a transfer coefficient, a = 0.5, were estimated from square wave voltammetry.