The gadolinium effect on crystallization behavior and luminescence of β-NaYF4:Yb,Er phase

Abstract

Single phase β-NaY0.8-xGdxYb0.18Er0.02F4 nanoparticles with different concentrations of gadolinium ions were prepared via PVP-assisted solvothermal treating at 200°C (PVP- polyvinylpyrrolidone). With the increase in Gd3+ 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 2H11/2, 4S3/2 → 4I15/2 and 4F9/2 → 4I15/2 transitions, respectively. The strongest up-conversion luminescence was detected in 15 mol% Gd3+-doped nanoparticles obtained after 20 hours of solvothermal treating. With the rise of Gd3+ content up-conversion emission decreased due to increased defect concentration in the NaYF4 matrix. Fourier transform infrared spectroscopy proved in situ generation of hydrophilic nanoparticles as a result of PVP ligands retention at the particle surface.