Permeation of Electroactive Solutes through Ultrathin Polymeric Films on Electrode Surfaces

摘要

The rates of permeation of a series of electroactive solutes, bromide, ferrocene, benzoquinone, diquat, (Ru(bpy)2Cl2), (Fe(bpy)2(CN)2), and (Ru(bpy)2(py)Cl)(+) have been measured through ultrathin, electrochemically polymerized films like poly-(Ru(vbpy)3-2plus 2 valence. The films are coated on Pt disk electrodes. The permeabilities, expressed as PDS, pol, the product of a partition coefficient and a diffusion coefficients in the films, range from very fast (bromide, greater than 4 X 10 to the -7 square centimeters/sec.). The permeation rates vary linearly with films thickness; this and the molecular size discrimination rule out transport through larger-than-molecular-dimensional channels and pinholes in the film. The film permeability process is described as membrane diffusion. Relatively pinhole-free films are preparable as thin as 20 - 40 angstroms. (Author)