Customised porphyrin coating films for graphite electrode protection: An investigation on the role of peripheral groups by coupled AFM and cyclic voltammetry techniques

Controlling the molecular arrangement of properly designed materials is the ultimate target of studies in surface protection by organic thin films. The properties of the films are even more critical when the protection ability must be match with the function of the underneath active surface as in the case of electrodes covered by suitable protective as well conductive materials. In this context, we demonstrate that the electrode protection against anion intercalation, exerted by a vacuum deposited thin film of meso-tetraphenylporphyrin (H2TPP) on a highly-oriented pyrolytic graphite (HOPG) electrode, can be maximized by tailoring the peripheral groups of the porphyrin skeleton. From atomic force microscopy and cyclic voltammetry investigations, our results highlight the important role played by the molecular/electronic structure of the porphyrins to enhance the molecule-substrate interaction and the molecular assembly in the case of a perfluorinated derivative, thus resulting in effective protection ability in acid environment outperforming theH2TPP film.