ZnS nanoparticles with different sizes are synthesized using a reverse micelles method in the presence of Tb3+ ions. The photoluminescence, excitation and absorption spectra of ZnS/Tb3+ NPs are studied to elucidate remarkable energy transfer from both ZnS host and the surfactant, i.e., AOT, to Tb3+ ions. When Tb3+ ions are introduced merely on the outside of ZnS nanoparticles in reverse micelles, obvious energy transfer from ZnS to the Tb3+ ions is also observed, indicating the important role of spatial confinement on the performance of energy transfer between host and luminescent centers which are even not doped into the host lattices. (c) 2005 Elsevier B.V. All rights reserved.