Surface-modified EuF3 nanoparticles has been produced by mixing of NaF and Eu(NO3)(3) aqueous solutions in the presence of sodium citrate as stabilizer. Transmission electron microscopy and dynamic light scattering has shown citric ions influence on the particle size and morphology. Modified and unmodified EuF3 samples were characterized by X-ray diffraction, elemental analysis, IR and luminescence spectroscopy. The results indicate that citrate ions bond chemically with EuF3 particle, forming a layer onto the surface. The layer stabilizes nanoparticle colloids and prevents their aggregation. In the case of modified EuF3 colloids, reversible precipitation-peptization processes at varying pH values and Cu2+ chemosorption by citric layer are revealed. (C) 2009 Elsevier B. V. All rights reserved.