We report on the synthesis, characterization and photophysical study of new luminescent and magnetic hybrid silica nanoparticles. Our method is based on the co-encapsulation of single maghemite gamma-Fe2O3 nanoparticles and luminescent molybdenum cluster units [Mo(6)Br(8)Brg](2-) through a water-in-oil (W/O) microemulsion technique. The as-prepared core-shell [Cs2Mo6Br14-gamma Fe2O3]@SiO2 nanoparticles (4553 nm) possess a single magnetic core (6, 10.5 or 15 nm) and the cluster units are dispersed in the entire volume of the silica sphere. The [Cs2Mo6Br14-gamma Fe2O3]@SiO2 nanoparticles have a perfect spherical shape with a good monodispersity and they display red and near-infrared (NIR) emission in water under UV excitation, whose intensity depends on the magnetic core size. The hybrid nanoparticles have been characterized by transmission electron microscopy (TEM), high annular angular dark field scanning transmission electron microscopy (HAADF-STEM), energy-dispersive X-ray spectroscopy (EDX), UV-Vis-NIR spectroscopy and magnetometer SQUID analysis. Small gold nanoparticles were successfully nucleated at the surface of the hybrid silica nanoparticles in order to add plasmonic properties. (C) 2014 Elsevier Inc. All rights reserved.