Immobilization of electroactive molecules in organized thin films

Redox mediators were immobilized in ordered thin films of an organic matrix. We preliminarily prepared and characterized Langmuir-Blodgett (LB) films of dipalmitoyilphosphatidic acid (DPPA), Self-Assembled (SA) monolayer of octadecylthiol (ODM) and Hybrid Films (HF) combining LB and SA technologies. Several redox mediators were tentatively co-spread with DPPA molecules at the water-air interface and surface pressure-area (π-A) isotherms were recorded. On the basis of its evident tendency to remain incorporated into the monolayer, we select 3-3V,5-5Vtetramethylbenzidine (TMB) and we prepared LB and HF films containing TMB on different solid supports. The resulting structures were characterized by means of ellipsometry and contact angle measurements as a function of mediator content. Electrochemical characterization was performed on the same systems, recording cyclic voltammograms as a function of the number of layers constituting the film at two different transfer surface pressures (π_tr). LB films containing TMB were also characterized by means of UV-VIS spectroscopy, as a function of ptr and of the number of layers. The two sets of independent results evidenced that TMB is quantitatively immobilized in LB nanostructures of DPPA maintaining its electroactive behaviour.