Europium (III) (Eu3+)-doped hydroxyapatite (HAp) nanocrystals were synthesized in the presence of a cetyltrimethylammoniumbromide (CTAB) to investigate the states of Eu3+ ions in the structure. The HAp structure was preserved with the doping as well as the CTAB existence, and the carbonate ions were included in the structure. The uniformshapes andmono-dispersion of the nanocrystals were observed by adding CTAB. The transitions of D-5(0)-F-7(1) and D-5(0)-F-7(2) in the photoluminescence spectra indicated the presence of the Eu3+ in an environment of a low symmetry before the calcination. The Eu3+ was effectively positioned in the Ca sites in the HAp structure. The CTAB addition would prevent the Eu3+ ions from aggregating each other, inducing the effective substitution and resultantly showing the efficient luminescence. Therefore, the interactions between the Eu3+ ions and HAp structure were successfully enhanced in the presence of CTAB. (C) 2016 Elsevier B.V.