Europium(III) and Gadolinium(III) co-doped nanohydroxyapatite with enhanced photoluminescence as potential multimodal bioimaging agent

The advancement of bioimaging and theranostics necessitates the development of highly biocompatible multifunctional agents. Here, we introduce a potential multimodal agent based on nanosized hydroxyapatite (HAp) codoped with europium(III) and gadolinium(III) (Eu3+ and Gd3+) ions. The study presents a detailed characterization of the HAp:Eu3+/Gd3+ nanoparticles synthesized via the co-precipitation method. The structure and morphology were analyzed using X-ray powder diffraction (XRPD), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The study of spectroscopic properties (emission, excitation, emission kinetics) as a function of optically active ions was carried out. Moreover, various dopant ratio combinations were studied to optimize the optical and magnetic properties. HAp:Eu3+/Gd3+ demonstrates tunable PL intensity with different concentrations of Eu3+ and Gd3+ ions and increased magnetization with higher doping with Gd3+ ions. Furthermore, co-doping with Gd3+ ions results in an enhancement of Eu3+ emission intensity, rendering HAp:Eu3+/Gd3+ a potentially promising candidate for bioimaging applications.