Polystyrene nanoparticles doped with a luminescent europium complex, Eu(tta)(3)phen, are prepared by miniemulsion polymerization. The influence of the complex on the miniemulsion polymerization is investigated by the systematic variation of the initial concentration of Eu(tta)(3)phen from 2 to 7 wt% relatively to styrene. A maximum doping level of about 2% by weight in the final particles can be achieved. At higher doping levels, destabilization of the miniemulsion leads to a loss of reproducibility with respect to both the degree of conversion and the final Eu content of the particles. Doped nanoparticles of varying diameter, ranging from 19 to 94 nm, are successfully prepared. Steady-state and time-resolved luminescence measurements indicate that the luminescence properties of Eu(tta)(3)phen in the doped latexes are unchanged from those found in THE solution. Aqueous dispersions of the doped particles exhibit characteristic red emission under UV light irradiation. The luminescence intensity increases linearly with Eu(tta)3phen content, indicating the absence of self-quenching despite the relatively high local concentrations within the particles. (C) 2012 Elsevier Inc. All rights reserved.