Synthesis and characterization of Tb3+/Gd3+ dual-doped multifunctional hydroxyapatite nanoparticles

Tb3+/Gd3+ dual-doped multifunctional hydroxyapatite (Tb3+/Gd3+-HAp) nanoparticles with magnetic and luminescent properties were prepared by the co-precipitation method using CaCl2 and Na2HPO4·12H2O as raw materials and CTAB as a template in alkaline conditions. The products were characterized by X-ray diffractometry (XRD), field emission scanning electron microscopy (FESEM), transmission electron microscopy (TEM). Single hexagonal phase Tb3+/Gd3+-HAp nanoparticles were obtained by the co-precipitation method and the products were sphere-like morphology with particle sizes ranging from 40 to 100 nm. Crystallinity degree of the products decreased with the Tb3+/Gd3+ substitute increasing. Photoluminescence (PL) and magnetic properties of the products were also investigated. The results show Tb3+/Gd3+-HAp nanoparticles are endowed with strong luminescence at 544 nm and prominent paramagnetic behavior, allowing their potential applications in biological labeling. Gd3+ ions sensitize the 5D4-7F5 transition emission of Tb3+ ions in HAp nanoparticles, and the PL emission intensity increases along with increasing concentration of Gd3+ ions. Concentration quenching occurs when the Gd3+ concentration exceeds 10 mol%. The magnetization level of Tb3+/Gd3+-HAp increased steadily with the doping concentration of Gd3+ ions.