Synthesis and characterization of Tb/Gd 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.