Eu 3+ doped α-sodium gadolinium fluoride luminomagnetic nanophosphor as a bimodal nanoprobe for high-contrast in vitro bioimaging and external magnetic field tracking applications.

Herein, we introduce a novel strategy for the synthesis of Eu ³⁺ doped α-sodium gadolinium fluoride (α-NaGd _0.88 F ₄ :Eu _0.12 ³⁺ ) based luminomagnetic nanophosphors using hydrothermal route. The synthesized nanophosphor has exceptional luminescent and paramagnetic properties in a single host lattice, which is highly desirable for biomedical applications. This highly luminescent nanophosphor with an average particle size ∼ 5±3 nm enables high-contrast fluorescent imaging with decreased light scattering. In vitro cellular uptake is shown by fluorescent microscopy that envisages the characteristic hypersensitive red emission of Eu ³⁺ doped α-sodium gadolinium fluoride centered at 608 nm ( ⁵ D ₀ - ⁷ F ₂ ) upon 465 nm excitation wavelength. No apparent cytotoxicity is observed. Furthermore, time- resolved emission spectroscopy and SQUID magnetic measurements successfully demonstrate a photoluminescence decay time in microseconds and enhanced paramagnetic behavior respectively, which promises the applications of nanophosphors in biomedical studies. Hence, the obtained results strongly suggest that this nanophosphor could be potentially used as a bimodal nanoprobe for high-contrast in vitro bio-imaging of HeLa cells and external magnetic field tracking applications of luminomagnetic nanophosphors using permanent magnet.