A structural topotactical transformation synthetic strategy for Y2O2S:Ln3+ micro/nanocrystals with multicolor emissions

Abstract

Designing the synthesis of inorganic micro/nanocrystals that are hard to get through conventional synthetic routes remains a challenging issue. Herein, we developed a novel in situ topotactic transformation synthetic strategy towards Y₂O₂S micro/nanocrystals based on high topotactic structural matching with the crystalline relationship between [001]Y₄O(OH)₉NO₃//[001]Y₂O₂S and [001]LYH//[010]Y₂O₂S (LYH is Y₂(OH)₅NO₃·nH₂O). We have contrastively elucidated the in situ topotactic transformation mechanism from the crystal structure point of view and found that the microscopically topotactic structural matching in structural anisotropy and atomic arrangement facilitates the Y₄O(OH)₉NO₃ → Y₂O₂S and LYH → Y₂O₂S transformation processes, respectively. Interestingly, the morphology contours were maintained well although a high degree of crystal lattice rearrangement was involved during the topotactic transformation process, which contributed to two brand-new morphologies that were unavailable by the conventional synthetic route (hexagonal microprism and quadrangle nanoplate) for Y₂O₂S. Besides, we also selected amorphous Y(OH)CO₃ sub-microsphere as a precursor to comparatively study the structural topotactic transformation. Furthermore, the luminescence properties of the as-prepared micro/nanophosphors were emphasized by featuring the multicolor emissions by downshifting (Eu³⁺, Tb³⁺) and upconversion (Yb³⁺/Er³⁺, Yb³⁺/Tm³⁺) luminescence. Our study may bring a new direction of thought for the targeted synthesis of inorganic micro/nanocrystals that are difficult to get via conventional synthetic routes.