Collective substitutions of selective rare earths (Yb, Dy, Tb, Gd, Eu, Nd) in ZrO: an exciting prospect for biomedical applications

The study aims to understand the significance of collective rare earth (RE 3+ ) substitutions in ZrO 2 structures for biomedical applications. The RE 3+ ions namely Yb 3+ , Dy 3+ , Tb 3+ , Gd 3+ , Eu 3+ , and Nd 3+ were selected and their concentrations were adjusted to obtain three different combinations. The influence of RE 3+ on the crystal structure of ZrO 2 alongside the absorption, luminescence, mechanical, magnetic, computed tomography (CT), magnetic resonance imaging (MRI) properties was explored. The concomitant effect of the average ionic size and RE 3+ concentration determines the crystallization behavior of ZrO 2 at elevated temperatures. The collective RE 3+ substitutions exhibit both up-conversion and down-conversion emissions with their respective excitation at 793 and 350 nm. Nevertheless, increment in the concentration of RE 3+ is found to be detrimental to the mechanical stability of ZrO 2 . The collective characteristics of multiple RE 3+ demonstrate the potential of the investigated system in multimodal imaging applications. The unique luminescence characteristics of Eu 3+ and Tb 3+ are promising for fluorescence imaging while the presence of Dy 3+ , Tb 3+ , Gd 3+ and Nd 3+ unveils a paramagnetic response required for MRI. In addition, Dy 3+ and Yb 3+ contribute to the high X-ray absorption coefficient values suitable for X-ray CT imaging. Collective rare earth substitutions in ZrO 2 display structural and mechanical stability alongside a wide range of optical, luminescence, CT and MRI features.