Tunable multicolor and bright white emission in PEG modified β-NaGdF4 nanocrystals by systematic introduction of Ce3+ and Mn2+/Ln3+

Abstract

In this paper, Mn²⁺/Ln³⁺-doped hexagonal phase (β-) NaGdF₄:Ce (Ln = Tb, Dy, Eu) nanomaterials with subtly tuned multicolor output have been successfully synthesized by a typical simple hydrothermal method using polyethylene glycol (PEG) as a surface modifying agent. The crystal structures, morphology, luminescence performance, and energy transfer (ET) mechanism of the synthesized NaGdF₄ nanoparticles (NPs) were investigated in detail. It is found that due to the effective ET between Ce³⁺ and Mn²⁺/Ln³⁺, the multicolor down-conversion (DC) emission phosphors can yield three major emission bands in the visible region including blue, green and red. Moreover, the white emission could be realized through manipulating the doping ratio of Ce³⁺, Dy³⁺ and Eu³⁺ with suitable concentration in β-NaGdF₄ NPs through effective resonance-type ET under the irradiation of 273 nm. And the corresponding CIE1931 coordinates were calculated to be (0.31, 0.32), which is near the normative white emission (0.33, 0.33). All the multicolor tuning and white emission results evidently suggest that the present Ce³⁺ and Mn²⁺/Ln³⁺-doped β-NaGdF₄ NPs are feasible phosphors for potential applications in white-light emitters, full-color displays and photonic devices.