Selective growth and upconversion photoluminescence of Y-based fluorides: From NaYF₄: Yb/Er to YF₃: Yb/Er crystals

Y-based fluorides have been recognized as most efficient host materials for upconversion photoluminescence (UC-PL). Herein, we have produced a series of Yb/Er doped Y-based fluorides with specific crystal structures, shapes and sizes. The selective growth process is governed by our pre-designed surfactant 4, 4^′-((2,5-bi’s (2-(diethylamino) ethoxy) -1,4-phenylene) bis (ethyne-2,1-diyl)) dibenzoic acid (DBA) and selective solvents. It is shown that highly pure hexagonal microprisms and cubic microspheres of NaYF₄: Yb/Er could be selectively grown in water at low and high content of DBA, respectively, while only orthorhombic nanowires and microflowers of YF₃: Yb/Er could be obtained in ethanol. Finally, all these materials obtained exhibit strong UC-PL signal while the UC emission intensity of the NaYF₄: Yb/Er hexagonal microprisms is much higher than those of the cubic microspheres and orthorhombic YF₃ nanowires and microflowers. This work provides a novel method for selective crystal growth of Y-based fluorides with specific shape, size, crystal phase and highly UC-PL efficiency by breaking the intrinsic limitation of crystal growth habit, which could be possibly extended to the controlled synthesis of other related materials.