Study of the electron transfer properties of nanostructured bimetallic films of polymerized porphyrins

The amperometric response of gold electrodes modified with bimetallic films of metalloporphyrins (FeCuPP) to H2O2 is dramatically higher than the corresponding to the bare electrode (up to 60 times) and far exceeding the individual CuPP or FePP. This response is attributed to the incorporation of H2O2 as ligand of both metal centers. Polymeric mono and bimetallic porphyrins doped with multiwalled carbon nanotubes were studied by EIS and voltammetry to understand the differential response. A better electron transfer rate was observed in the composites allowing the study of the effect of ligands on the electrochemical response. The cyclic voltammetry showed a reversible wave for azide reduction only with the bimetallic composite. The EIS experiment showed two different RC time constants suggesting that H2O2 and azide intercalate as linking the metal centres. The anion nitrite inhibits these differences and does not affect the monometallic structures.Polymers deposited onto gold electrodes reveal an amorphous structure by SEM micrograph, whereas the corresponding composites prepared by electro-co-deposition present a network of interconnected fibrils with diameters similar to the nanotubes serving as backbones of the porphyrin aggregates.