Electrochemical and spectroelectrochemical characterization of lipid organization in an electric field

The characterization of the adsorption/desorption of water insoluble surfactants onto an electrified interface is reviewed. Electrochemical and spectroelectrochemical investigations of the role of potential in controlling the nature of the surfactant present at the interface is described. The adsorption of octadecanol, cis-9-octadecenol onto Au(1 1 1) and the adsorption of DOPC (from a monolayer or from a dispersion of liposomes) onto Hg are used as examples. A general mechanism was proposed to describe the potential-dependent phase changes, desorption and subsequent readsorption process that links the results from impedance, fluorescence and elastically scattered light measurements of the surfactant-modified interface. This proposed mechanism and results from fluorescence microscopy results were used to describe the creation of a hybrid adsorbed hemi-liposomal layer onto a Hg surface. The implications for thermodynamic analysis via the electrocapillary equation for this class of surfactants were discussed. The relevance of the general mechanism towards the reductive desorption of alkyl thiol SAMs was also outlined.