Cosubstitution of Lanthanides (Gd<sup>3+</sup>/Dy<sup>3+</sup>/Yb<sup>3+</sup>) in β‑Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> for Upconversion Luminescence, CT/MRI Multimodal Imaging

Published on 2018-06-24T11:29:34Z (GMT) by
Multifunctional Gd<sup>3+</sup>, Dy<sup>3+</sup> and Yb<sup>3+</sup> cosubstitutions in β-Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> were achieved through a facile synthetic technique. Gd<sup>3+</sup> and Dy<sup>3+</sup> prefer to occupy the 7-fold coordinated Ca<sup>2+</sup>(1), 6- or 8-fold coordinated Ca<sup>2+</sup>(2), and 8-fold coordinated Ca<sup>2+</sup>(3) sites of the β-Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> structure. The shortest Ca(5)O bond length of te Ca<sup>2+</sup>(5) site with 6-fold co-ordination favors Yb<sup>3+</sup> accommodation. The substitution limit of each dopant to attain β-Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> solid solution is determined as ∼1.25 mol %. The combined substitutions displayed upconversion emission in blue, yellow and red regions on excitation at 980 nm via the energy transfer mechanism from Yb<sup>3+</sup> to Dy<sup>3+</sup>. Yb<sup>3+</sup> and Dy<sup>3+</sup> combination induces a high X-ray absorption ability for computed tomography (CT). The materials also displayed paramagnetic behavior and exhibited high longitudinal (<i>r</i><sub>1</sub> = 48.71 mM<sup>–1</sup> s<sup>–1</sup>) and transverse relaxivity (<i>r</i><sub>2</sub> = 61.79 mM<sup>–1</sup> s<sup>–1</sup>) indicating their potential as <i>T</i><sub>1</sub> and <i>T</i><sub>2</sub> contrast agents in magnetic resonance imaging (MRI). The negligible toxicity of Gd<sup>3+</sup>/Dy<sup>3+</sup>/Yb<sup>3+</sup> cosubstitutions in β-Ca<sub>3</sub>(PO<sub>4</sub>)<sub>2</sub> is also demonstrated. The overall results justify the potential of the developed material as possible contrast agent for <i>T</i><sub>1</sub> and <i>T</i><sub>2</sub> MRI/CT/upconversion luminescence.

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Meenambal, Rugmani; Kannan, S. (2018): Cosubstitution of Lanthanides (Gd3+/Dy3+/Yb3+) in β‑Ca3(PO4)2 for Upconversion Luminescence, CT/MRI Multimodal Imaging. ACS Publications. Collection.