Films based on electrostatic interactions between tetracationic porphyrin, 5,10,15,20-(4-trimethylammoniophenyl) porphyrin tetra(p-toluenesulfonate), [H2TPhN(Me)(3)P](4+) and Dawson type polyoxometalate alpha(2)-[Fe(P2W17O61)](7-) (POM) are formed by the so called layer-by-layer self-assembly method. Successive deposition of layers has been monitored by UV-visible absorption spectroscopy. Atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS) have been used to explore the morphology and composition, respectively. Electrochemistry and permeability studies have been carried out by cyclic voltammetry. The photocatalytic properties of these films have been also studied for the reduction of silver ions. Indeed, in these systems, porphyrins can be excited by visible light which play the role of photosensitizers able to give electrons to POM known to be good catalysts. Giant silver dendrites have been obtained. (C) 2012 Elsevier B.V. All rights reserved.