A Polyol-Mediated Fluoride Ions Slow-Releasing Strategy for the Phase-Controlled Synthesis of Photofunctional Mesocrystals.

There are only a few inorganic compounds that have evoked as much interest as sodium yttrium fluoride (NaYF₄). Its extensive applications in various fields, including transparent displays, luminescence coding, data storage, as well as biological imaging, demand the precise tuning of the crystal phase. Controlling the emergence of the desired α-phase has so far remained a formidable challenge, especially via a simple procedure. Herein, we represented a polyol-assisted fluoride ions slow-release strategy for the rational control of pure cubic phase NaYF₄ mesocrystals. The combination of fluorine-containing ionic liquid as a fluoride source and the existence of a polyalcohol as the reactive medium ensure the formation of uniform α-phase mesocrystallines in spite of a higher temperature and/or higher doping level.