Phase-Transition-Driven Regional Distribution of Rare-Earth Ions for Multiplexed Upconversion Emissions

• Published in: JACS Au 2023-03, Vol.3 (3), p.860-867
• Main Authors: Lyu, Ze-Yu, Dong, Hao, Yang, Xiang-Fei, Huang, Ling, Xu, Yue-Jiao, Wu, Ke, Sun, Ling-Dong, Yan, Chun-Hua
• Format: Article
• Language: English
• ISSN: 2691-3704; 2691-3704
• DOI: 10.1021/jacsau.2c00660

Phase transition of the polymorphs is critical for controlled synthesis and property modulation of functional materials. Upconversion emissions from an efficient hexagonal sodium rare-earth (RE) fluoride compound, β-NaREF4, which is generally obtained from the phase transition of the cubic (α-) phase counterpart, are attractive for photonic applications. However, the investigation of the α → β phase transition of NaREF4 and its effect on the composition and architecture is still preliminary. Herein, we investigated the phase transition with two kinds of α-NaREF4 particles. Instead of a uniform composition, the β-NaREF4 microcrystals exhibited regionally distributed RE3+ ions, in which the RE3+ with a smaller ionic radius (smaller RE3+) sandwiched the RE3+ with a larger ionic radius (larger RE3+). We unravel that the α-NaREF4 particles transformed to β-NaREF4 nuclei with no controversial dissolution, and the α → β phase transition toward NaREF4 microcrystals included nucleation and growth steps. The component-dependent phase transition is corroborated with RE3+ ions from Ho3+ to Lu3+ and multiple sandwiched microcrystals were obtained, in which up to five kinds of RE components were distributed regionally. Moreover, with rational integration of luminescent RE3+ ions, a single particle with multiplexed upconversion emissions in wavelength and lifetime domains is demonstrated, which provides a unique platform for optical multiplexing applications.