Color tunable YF3: Ce3+/Ln3+(Ln3+: Eu3+, Tb3+, Dy3+, Sm3+) luminescent system: role of sensitizer and energy transfer study

Nano-fluorides with attractive optical properties have been proposed as potential phosphors for solid state lighting and bio-applications. In the present work, redispersible YF3: Ln(3+) and YF3: Ce3+/Ln(3+) nanocrystals were obtained by a simple one step ethylene glycol mediated soft chemical synthesis. Uniformly distributed nanoparticles with a leaf-like morphology and particle size of 10-15 nm were observed. X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transformed infrared spectroscopy (FT-IR), photoluminescence (PL) and decay studies were employed to characterize the samples. The highly intense emissions of various activators (Dy3+, Tb3+, Eu3+ and Sm3+) in the presence of Ce3+, their long lifetimes (similar to ms) and significant reduction in the lifetime of Ce3+ proved an efficient energy transfer operating in the nanocrystals. The time resolved emission studies indicated towards the presence of two different sites for the activator ions. Under ultraviolet irradiation, the emission color of YF3: Ce3+/Ln(3+) nanophosphors can be easily tuned by changing the Ln(3+) ions. Bright blue (Dy3+), green (Tb3+), red (Eu3+) and purple (Sm3+) emissions were observed from corresponding YF3: Ce3+, Ln(3+) nanocrystals under ultraviolet light.