Yttrium oxide nanoparticles doped with 2.0 wt% Eu (Eu@Y2O3) were synthesized via the surfactant assembly method. The average diameter of Eu@Y2O3 (day) depends on the alkyl chain number (N) of the sodium alkyl sulfates employed as surfactants. Using surfactants with N = 8,10, and 12, Eu@Y2O3 with day = 35, 200, and 500 nm, respectively were obtained. Such changes in day are ascribed to the difference in the micelle aggregation numbers, supporting the use of rare-earth ions in the assembly. The Eu@Y2O3 particles synthesized presently emitted through Eu3+ transitions under UV excitation of Y2O3, making them applicable to nanoemitters. (C) 2016 Elsevier B.V. All rights reserved.