ELECTRICAL CHARACTERIZATION OF DIPALMITOYLPHOSPHATIDYLETHANOLAMINE AND CADMIUM STEARATE FILMS ON PLATINUM SURFACES IN AQUEOUS-SOLUTIONS

The electrical properties of multilayers of both cadmium stearate and dipalmitoylphosphatidyl-ethanolamine/dipalmitoyl phosphatidic acid films transferred onto platinum wires by using the Lang-muir-Blodgett process have been investigated. The electrical measurements of the films were per-formed in situ. The impedance of the lipid films on the platinum is determined as a function of the lipid surface pressure of the film in the trough and was found to increase with increasing surface pres-sure. Although the films could be transferrred at relatively low pressures, it was found that a relatively high pressure is necessary to obtain an impedance comparable to black lipid membrane impedance. The impedance is used to determine the coverage of the platinum as a function of surface pressure and area per molecule. The coverage of the electrode is investigated for a variety of dipping speeds at fixed ionic strengths and pHs of the trough. The effects of water on the impedance of the multilayers of the cadmium stearate films are discussed. The electrical impedance of the films is compared to the impedance of lipid films prepared under other conditions. These results serve as the basis for analyzing lipid and fatty acid films in aqueous environments for sensor applications. © 1990, American Chemical Society. All rights reserved.