Abstract Eu2+ and Eu3+ co-activated YF3:Eu phosphors were prepared by a traditional hydrothermal method with citric acid as reducing agent. Products with bitter gourd like morphology comprised of numerous nanoparticles show a blue emission of Eu2+ and a red emission of Eu3+ simultaneously. The relative amount of Eu2+ and Eu3+ can be tuned by adjusting Eu concentration, citric acid concentration and hydrothermal reaction time. Obvious energy transfer from Eu2+ to Eu3+ can be observed. Through energy transfer, Eu2+ and Eu3+ can be effectively excited by the ultraviolet light in the range of 275–400 nm and a tunable luminescence color from red, white to blue can be achieved. The work will provide an alternative solution for the development of new LED phosphors.

中文翻译：

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水热法制备的荧光粉 YF3:Eu 从 Eu2+ 到 Eu3+ 的能量转移和可调发光的观察

摘要 以柠檬酸为还原剂，采用传统的水热法制备了Eu2+和Eu3+共活化的YF3:Eu荧光粉。由无数纳米颗粒组成的苦瓜状形态的产品同时显示出 Eu2+ 的蓝色发射和 Eu3+ 的红色发射。Eu2+ 和 Eu3+ 的相对量可以通过调节 Eu 浓度、柠檬酸浓度和水热反应时间来调节。可以观察到从 Eu2+ 到 Eu3+ 的明显能量转移。通过能量转移，Eu2+和Eu3+可以被275-400nm范围内的紫外光有效激发，并且可以实现从红色、白色到蓝色的可调发光颜色。该工作将为开发新型 LED 荧光粉提供替代解决方案。