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

Abstract

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: Ln³⁺ and YF₃: Ce³⁺/Ln³⁺ 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 (∼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⁺/Ln³⁺ nanophosphors can be easily tuned by changing the Ln³⁺ ions. Bright blue (Dy³⁺), green (Tb³⁺), red (Eu³⁺) and purple (Sm³⁺) emissions were observed from corresponding YF₃: Ce³⁺, Ln³⁺ nanocrystals under ultraviolet light.