“Electron transfer processes at electrodes covered by lipid layers. Correlation with the lipid behavior at air-water interfaces”.

M. F. MORA, N. WILKE, A.M. BARUZZI

LANGMUIR

ACS

Año: 2003 vol. 19 p. 6876 - 6880

0743-7463

Langmuir-Blodgett lipid films deposited onto glassy carbon electrodes were analyzed by comparing the voltammetric profiles of Fe(CN)6 3-/Fe(CN)6 4-, FeEDTA-/FeEDTA2-, Cu(NH3)4 2+/Cu(NH3)2 +, and Ru- (NH3)6 3+/Ru(NH3)6 2+ redox couples at these electrodes. A series of sphingolipids was analyzed, including a glicerocholine. A decrease in current depending on the lipid nature and on the couple was observed. The dependence on the lipid nature was analyzed by considering the behavior of the lipid monolayers at the air-aqueous-phase interface. The molecular area of the lipids, the dipole moment perpendicular to the interface, and the compressibility at the transfer pressure were obtained from the compression isotherms when each redox couple was present in the subphase. The results indicate that the electrochemical blocking depends mainly on the compressibility factor. Concerning the dependence on the redox reaction nature, it was found that, under these experimental conditions and for neutral lipids, as the electron-transferprocess rate increases, the electrochemical response is less sensitive to the presence of the lipid layers.-Blodgett lipid films deposited onto glassy carbon electrodes were analyzed by comparing the voltammetric profiles of Fe(CN)6 3-/Fe(CN)6 4-, FeEDTA-/FeEDTA2-, Cu(NH3)4 2+/Cu(NH3)2 +, and Ru- (NH3)6 3+/Ru(NH3)6 2+ redox couples at these electrodes. A series of sphingolipids was analyzed, including a glicerocholine. A decrease in current depending on the lipid nature and on the couple was observed. The dependence on the lipid nature was analyzed by considering the behavior of the lipid monolayers at the air-aqueous-phase interface. The molecular area of the lipids, the dipole moment perpendicular to the interface, and the compressibility at the transfer pressure were obtained from the compression isotherms when each redox couple was present in the subphase. The results indicate that the electrochemical blocking depends mainly on the compressibility factor. Concerning the dependence on the redox reaction nature, it was found that, under these experimental conditions and for neutral lipids, as the electron-transferprocess rate increases, the electrochemical response is less sensitive to the presence of the lipid layers.