Electrical Properties of Langmuir-Blodgett Nano Thin Biofilms from a Fluorescently Labelled Phospholipid for Biosensor Applications

Fluorescently labelled phospholipids are promising matrix molecules for the sensing layer in chemical biosensor applications. However, their electrical properties in a well-ordered monolayer deposited on a conducting substrate have not been investigated. Here we combine the powerful methods of Scanning Kelvin Probe Microscopy with nanometer lateral resolution and Electrical Impedance Spectroscopy (EIS) to investigate these properties. For the EIS measurements we use the interdigitated gold electrodes of a Surface Acoustic Wave resonator to measure electrical properties parallel to the substrate, which is a novel approach. Molecules behave as dielectrics with resistance around 440 GΩ. Lower resistance is observed at the boundaries of the micrometer sized solid phase domains where the film is the liquid phase. On exposure to chloroform vapors over two orders decrease in resistance was observed which was completely reversible.