Keggin-type dodecatungstosilicates polyoxometallates (POMs) ([SiW12O40](4-)) were immobilized in a straightforward manner by electrostatic interactions on ammonium layers covalently grafted on silicon. This method does not require any POM modification synthetical steps. The presence of [SiW12O40](4-) on the surface is demonstrated by X-ray Photoelectron Spectroscopy from a specific modification of the tungsten 4f(7/2) signal. Moreover the surface coverage of [Siw(12)O(40)](4-) has been improved by 35% upon changing the nature of the anchoring ammonium groups from protonated to methylated amino groups. The organic-inorganic composite films have also been characterized by cyclic voltammetry showing that POMs have a specific behavior on silicon surfaces. In addition the use of a polyallylamine capping layer proved to stabilize efficiently the POM electrochemical response. (C) 2011 Elsevier B.V. All rights reserved.