Mixed monolayers of phospholipids with a viologen and the electrochemical properties in Langmuir–Blodgett films

Monolayers of phospholipids, 1,2-Didodecanoyl-sn-glycero-3-phosphate (DDGP) and 1,2-dihexadecanoyl-sn-glycero-3-phosphate (DHGP), mixed with a viologen derivative 1,1-Dilauryl-4,4′-bipyridine dibromide have been formed on 0.01 mol l−1 NaClO4 subphase surface and transferred onto solid substrates by Langmuir-Blodgett method. An ideal mixing of two components could be achieved in molar ratio of 1:1. Electrochemical properties of the viologen in mixed mono- and multilayers have been studied for different parameters: the molar ratios of two components, the number of layers and the alkyl chains of phospholipid. Peak splitting and a large ΔEp value were observed for the LB films of DDGP/viologen, while not for DHGP/viologen. These electrochemical characters were discussed in terms of the formation of dimers, diffusion of a charged species in thin films as well as the arrangement of viologen.