Evaluation of europium-doped HA/beta-TCP ratio fluorescence in biphasic calcium phosphate nanocomposites controlled by the pH value during the synthesis

Abstract

Europium-doped hydroxyapatite (HA), beta-tricalcium phosphate (beta-TCP) and biphasic phosphate nanopowders were synthesized by co-precipitation method and their crystal structures and fluorescence properties were investigated depending on the pH of the starting solution. In the range of pH 6-10, HA and beta-TCP phases coexist The beta-TCP proportion increased as the pH of the solution decreased, while HA yields decreased. At pH below 6, monophasic beta-TCP powder was obtained after thermal treatment. In particular, HA and beta-TCP can be used as luminescent materials when activated by Eu3+ ions in substitution of Ca2+ ions. Herein, the Eu3+ ions doped HA and beta-TCP phase composition were analyzed in order to investigate the fluorescence emission of the HA, beta-TCP and biphasic compounds. Eu-doped HA exhibited a red-orange emission at 575 nm with several minor peaks at 610-640 nm, while Eu-doped beta-TCP had an unexpected strong red emission at 610-620 nm and a secondary band at 590-600 nm. In fact, the Eu:beta-TCP integrated emission area is almost 20-fold higher than Eu:HA for the same europium ion concentration. These results demonstrate the potential of Eu:beta-TCP as biomarker for medical applications, as drug release and targeting based on their luminescent properties. (C) 2016 Elsevier B.V. All rights reserved.