The gadolinium effect on crystallization behavior and luminescence of β‐NaYF ₄ :Yb,Er phase

Abstract Single phase β‐NaY _{0.8‐ x} Gd _x Yb _0.18 Er _0.02 F ₄ nanoparticles with different concentrations of gadolinium ions were prepared via PVP‐assisted solvothermal treating at 200°C (PVP‐ polyvinylpyrrolidone). With the increase in Gd ³⁺ concentration, size of the nanoparticles decreased. The up‐converting spectra recorded upon 980 nm irradiation showed the green (510‐560 nm) and red (640‐690 nm) emissions, due to ² H _11/2 , ⁴ S _3/2 → ⁴ I _15/2 and ⁴ F _9/2 → ⁴ I _15/2 transitions, respectively. The strongest up‐conversion luminescence was detected in 15 mol% Gd ³⁺ ‐doped nanoparticles obtained after 20 hours of solvothermal treating. With the rise of Gd ³⁺ content up‐conversion emission decreased due to increased defect concentration in the NaYF ₄ matrix. Fourier transform infrared spectroscopy proved in situ generation of hydrophilic nanoparticles as a result of PVP ligands retention at the particle surface.