Multicolor Tunable Luminescence Based on Tb³⁺/Eu³⁺ Doping through a Facile Hydrothermal Route

Ln³⁺-doped fluoride is a far efficient material for realizing multicolor emission, which plays an important part in full-color displays, biolabeling, and MRI. However, studies on the multicolor tuning properties of Ln³⁺-doped fluoride are mainly concentrated on a complicated process using three or more dopants, and the principle of energy transfer mechanism is still unclear. Herein, multicolor tunable emission is successfully obtained only by codoping with Tb³⁺ and Eu³⁺ ions in β-NaGdF₄ submicrocrystals via a facile hydrothermal route. Our work reveals that various emission colors can be obtained and tuned from red, orange-red, pink, and blue-green to green under single excitation energy via codoping Tb³⁺ and Eu³⁺ with rationally changed Eu³⁺/Tb³⁺ molar ratio due to the energy transfer between Tb³⁺ and Eu³⁺ ions in the β-NaGdF₄ host matrix. Meanwhile, the energy transfer mechanism in β-NaGdF₄: x Eu³⁺/y Tb³⁺ (x + y = 5 mol %) submicrocrystals is investigated. Our results evidence the potential of the dopants' distribution density as an effective way for analyzing energy transfer and multicolor-controlled mechanism in other rare earth fluoride luminescence materials. Discussions on the multicolor luminescence under a certain dopant concentration based on single host and wavelength excitation are essential toward the goal of the practical applications in the field of light display systems and optoelectronic devices.