A composite film consisting of the mixed-addenda Keggin-type polyoxometalate alpha-K3PMo3W9O40 (PMo3W9) and silver nanoparticles (AgNPs) was fabricated on quartz, silicon, and [TO by the layer-by-layer self-assembly method. The regular growth of the multilayer film was monitored by UV-vis spectroscopy, and the morphology was measured by atomic force microscopy (AFM). The multilayer film embedded by AgNPs exhibited the photo-luminescence ascribed to electronic transitions from excited states to d levels of the silver nanoparticles. The composite film also showed electrocatalytic activity towards reduction of NO2-, H2O2, ClO3-, BrO3-, and IO3- attributed to tungsten-centered and molybdenum-centered redox processes Of PMo3W9. (C) 2009 Elsevier Ltd. All rights reserved.