Controllable multicolor output, white luminescence and cathodoluminescence properties of high quality NaCeF₄:Ln³⁺ (Ln³⁺ = Eu³⁺, Dy³⁺, Tb³⁺) nanorods

Herein, a series of hexagonal phase lanthanide (Ln³⁺, Ln³⁺ = Eu³⁺, Dy³⁺, Tb³⁺) doped NaCeF₄ nanorods (NRs) with uniform morphology and monodispersity have been successfully synthesized via a typical hydrothermal method using oleic acid as the capping agent. The crystal phase and microstructure of the obtained NRs were analyzed by X-ray diffraction (XRD) patterns and transmission electron microscopy (TEM). The down conversion (DC) luminescence properties and mechanisms of the as-prepared NaCeF₄:Ln³⁺ NRs have been discussed in detail. The as-prepared samples show the characteristic f–f transition of Ln³⁺ (Ln³⁺ = Eu³⁺, Dy³⁺, Tb³⁺). The decay time and quantum yield of these obtained NRs are also studied. Moreover, tunable multicolor, especially white emissions, can be successfully achieved via varying the doping ions and doping concentration. By increasing the content of Eu³⁺, the emission colors vary from light green to white and finally to light red under the excitation of 395 nm. The calculated CIE coordinates of the obtained white emissions are (0.33, 0.31), which are very close to the standard white light located at (0.33, 0.33). This is the first time to demonstrate that white light emission is achieved via only singly-doping Eu³⁺ into the NaCeF₄ system. In addition, the multicolor output changes from yellowish-green to yellow under the excitation at 261 nm, which was also obtained by only tuning the doped content of Dy³⁺ in the NaCeF₄ host. As for Tb³⁺, bright yellowish green emissions were obtained under excitation at 261 nm. Moreover, the cathodoluminescence (CL) spectra demonstrate that these NRs can emerge as ideal nanophosphors under electron beam excitation. Therefore, the as-prepared NaCeF₄:Ln³⁺ NRs with tunable multicolor output and bright white emissions might be applied in field-emission devices, multicolor displays and solid state lasers.