Hybrid films composed of poly(luminol) and nanometer-sized clusters of polyoxometalate, SiMo12O404- and PMo12O403- have been prepared in acidic aqueous solutions. These films are stable and electrochemically active, and produced on glassy carbon, platinum, gold and transparent semiconductor tin oxide electrodes. The electrochemical quartz crystal microbalance and cyclic voltammetry were used to study in situ growth of the hybrid poly(luminol)/SiMo12O404- and poly(luminol)/PMo12O403-. Both the poly(luminol)/SiMo12O404- and poly(luminol)/PMo12O403- hybrid films showed four redox couples and the electrochemical properties were compared to SiMo12O404- and PMo12O403-. When transferred to various acidity aqueous solutions, the four redox couples and the formal potentials of two hybride film were observed to be pH-dependent. The electrocatalytic reduction of ClO3-, BrO3-, IO3-, S2O82- and NO2- by a poly(luminol)/PMo12O403- hybrid film in an acidic aqueous solution showed an electrocatalytic reduction activity of IO3- > BrO3- and ClO3-. The electrocatalytic oxidation of dopamine and epinephrine by a poly(luminol)/PMo12O403- hybrid film was also investigated. (C) 2005 Elsevier Ltd. All rights reserved.